Gelbart Cuts 1-Micron Parts on Home-Built Air-Bearing CNC Lathe

High precision air bearing CNC lathe and grinder — Dan Gelbart

Dan Gelbart

Floating every axis on surplus air bearings over precompressed granite parallels produces airtight, frictionless fits directly off tooling without manual lapping.

AI-assisted summary of High precision air bearing CNC lathe and grinder — original source. Check the original for full context.

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Key ideas

  • Dan Gelbart presents a home-built dual-purpose CNC lathe and cylindrical grinder capable of achieving 1-micron (0.00004") machining accuracy. (0:06)
  • Every spindle and carriage floats on pressurized air bearings, using surplus semiconductor manufacturing spindles sourced for roughly $200 each. (3:48)
  • The machine bed was built from commercial granite parallels bonded into T-sections with epoxy and placed under continuous compressive preloading via through-bolts. (6:20)
  • Workholding utilizes a watertight chuck adapted from an extinct Skinner design, featuring radial adjustment screws that allow chuck runout to be dialed down to zero. (2:00)

Detailed notes

## Background Published on YouTube by Dan Gelbart on March 6, 2015, this video showcases his home-built, ultra-high-precision air-bearing CNC lathe and grinder. According to the description, the dual-purpose machine tool was engineered from scratch to achieve an operating accuracy of one micron (0.00004 inches).

## TL;DR Dan Gelbart presents a scratch-built CNC machine tool capable of both turning and cylindrical grinding to one-micron tolerances, demonstrated initially with a self-acting air-bearing piston assembly that requires zero lapping. The design eliminates friction and wear by utilizing surplus semiconductor air-bearing spindles, a watertight modified Skinner-style chuck, and a bed assembled from commercial granite parallels bonded under permanent bolt compression. Powered by custom CNC software developed alongside James Midgley and equipped with manual DRO overrides and an inspection microscope, the system supports versatile prototyping workflows. Gelbart wraps up by demonstrating live single-point threading under high optical magnification and smooth, low-splash precision grinding with dialed-in zero runout.

## Atmosphere & style The presentation carries the understated, authoritative tone of a master-class workshop tour, completely free of dramatic hype or filler. Gelbart speaks with methodical, practical enthusiasm, casually demystifying sub-micron engineering while sharing thrifty maker techniques like trepanning depleted grinding stones and repurposing surplus eBay spindles. Watching the video feels deeply satisfying and tactile, marked by mesmerizing demonstrations—from the frictionless coasting of an airtight piston to the sharp, microscopic curl of metal chips in the live camera feed.

## Bulletin - [00:06](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=6s) Dan Gelbart presents a home-built dual-purpose CNC lathe and cylindrical grinder capable of achieving 1-micron (0.00004") machining accuracy. - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) Every spindle and carriage floats on pressurized air bearings, using surplus semiconductor manufacturing spindles sourced for roughly $200 each. - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) The machine bed was built from commercial granite parallels bonded into T-sections with epoxy and placed under continuous compressive preloading via through-bolts. - [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) Workholding utilizes a watertight chuck adapted from an extinct Skinner design, featuring radial adjustment screws that allow chuck runout to be dialed down to zero.

## Key takeaways - [00:06](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=6s) The machine achieves 1-micron (0.00004") geometric accuracy, enabling parts like matching pistons and cylinders to function as self-acting air bearings right off the tool without manual lapping. - [00:06](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=6s) A matched piston-and-cylinder demonstration shows zero-clearance, frictionless rotation and an airtight sliding fit with no oil film required. - [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) Gelbart collaborated with James Midgley to program a custom CNC package tailored to the combined operations of an integrated turning lathe and precision grinder. - [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) The custom chuck is based on a historical Skinner Chuck Company concept, fully sealing the radial slots against grinding swarf and coolant at all jaw positions. - [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) Drilled pin holes in the chuck face allow modular pins to clamp workpieces from 0 mm to approximately 200 mm on both inner and outer diameters. - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) All linear axes, the workhead spindle, and the grinding head utilize air bearings to completely eliminate stick-slip, mechanical friction, and wear. - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) Surplus air-bearing spindles manufactured for semiconductor fabrication equipment can be acquired second-hand for around $200. - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) The tailstock features a 300 mm quill extension, enabling up to 600 mm of center distance within a very compact overall machine footprint. - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) Custom internal grinding wheels are waterjet-cut from worn-out standard grinding wheels and epoxy-bonded to shanks, opening up full commercial abrasive selections for internal grinding. - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) The bed was constructed by epoxying commercial granite parallels that were pre-lapped to 1-micron parallelism on all four faces. - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) Granite components were clamped upside down on a master surface plate during bonding and through-bolted under compression so the epoxy experiences only pure shear. - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) Integrated digital readouts (DRO) allow the machine to operate fully manually if computer issues arise. - [08:25](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=505s) An integrated overhead video microscope displays a real-time magnified view of the cutting edge and chip formation during operations such as single-point threading. - [08:25](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=505s) Radial adjustment screws on the spindle nose allow an operator to dial chuck runout to absolute zero when re-chucking parts against reference surfaces. - [08:25](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=505s) A precision-metered coolant delivery system prevents splashing during high-speed cylindrical grinding while maintaining thermal stability.

## Detailed walkthrough ### [00:06](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=6s) The 1-Micron Lathe and Grinder & the Air-Bearing Demonstration

Dan Gelbart introduces his home-built, ultra-high-precision machine tool designed to cut, turn, and grind parts to a tolerance of one micron (approximately 40 millionths of an inch, or 0.00004"). Anticipating the obvious question of why an individual craftsman would ever require one-micron precision, Gelbart notes that numerous demanding applications require this level of accuracy, and he presents a finished cylinder-and-piston assembly as proof. The piston is machined to such tight geometric tolerances that it acts as a completely loose, free-sliding fit inside the cylinder bore with zero noticeable play.

```mermaid flowchart TD accTitle: Granite Bed Assembly Process accDescr: Diagram illustrating the step-by-step construction of the lathe bed using bonded granite parallels.

subgraph Prep ["Component Preparation"] A["Granite Parallels<br/>(4 sides parallel to 1 µm)"] B["Granite Surface Plate<br/>(Flat Reference Base)"] end

subgraph Assembly ["Alignment & Bonding"] C["Invert Bars onto Surface Plate"] D["Set Spacing with Precision Spacers"] E["Epoxy Bond Bars into T-Sections"] end

subgraph Preload ["Preloading & Final Geometry"] F["Preload Joints in Compression<br/>with Through-Bolts"] G["Finished Co-Planar Bed<br/>(1 µm Guidance Gap)"] end

A --> C B --> C C --> D D --> E E --> F F --> G ```

The mechanical behavior of the assembly changes dramatically depending on whether airflow is permitted. When Gelbart seals the small air vent on top with his fingertip, the fit proves to be completely airtight, instantly supporting the piston without physical contact. When spun by hand, both the outer sleeve and the inner core rotate frictionlessly for an extended duration, acting as a true self-acting air bearing. Conventional production of such matching parts demands laborious, iterative lapping steps, whereas this scratch-built machine produces finished parts right off the tooling.

Addressing the practical utility and mechanics of self-acting aerodynamic surfaces, Dan Gelbart explains: “So in other words if you made a bearing like this this bearing will never need lubrication and never wear out because there is no contact between the inner part and the outer part you can verify that with an ohmmeter while they turn it's the same idea as air bearing in a hard drive or air bearings and other self-acting air bearings devices.”

- **Accuracy specification:** 1 micron (0.001 mm / 40 millionths of an inch / 0.00004"). - **Demonstration workpiece:** Matched cylinder and piston demonstrating an airtight sliding fit with no oil film. - **Electrical verification:** Contactlessness can be tested with an ohmmeter across spinning parts to prove continuous infinite resistance.

---

[02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) Custom CNC Control and the Watertight Skinner-Style Chuck

Gelbart designed and fabricated the machine mechanicals from scratch, but he collaborated with engineer James Midgley out of Vancouver, British Columbia, to create a dedicated CNC software package. Off-the-shelf CNC control software could not accommodate the dual-purpose architecture of an integrated turning lathe and precision grinder alongside its idiosyncratic hardware setups. As Gelbart emphasizes: “The reason I couldn't use a standard software package is this machine is both a lathe and grinder and has some other special features so I wanted to have a customized CNC package.”

The workholding setup centers on a specialized chuck adapted from an extinct American design by the Skinner Chuck Company. Standard lathe chucks have radial slots that ingest coolant, grinding swarf, and fine debris, but this Skinner-derived mechanism remains entirely watertight at all jaw openings. The jaws are driven internally via drive pins, and the jaw bodies themselves continuously seal the radial slots.

Because precision finishing involves relatively small cutting forces, Gelbart drilled pin holes directly into the chuck face. By inserting modular pins into these positions, an operator can securely clamp parts on either their inner diameter (ID) or outer diameter (OD) without swapping out the primary jaws. This hybrid jaw-and-pin arrangement enables the chuck to grip workpieces spanning from zero up to roughly 200 mm in diameter.

- **CNC software developer:** James Midgley (Vancouver, BC). - **Chuck design basis:** Skinner Chuck Company design, modified for complete environmental sealing. - **Sealing mechanism:** Drive pins engage the jaws from behind while the jaw profiles cover the guideway slots. - **Pin gripping capacity:** 0 mm to ~200 mm diameter for both internal and external holding.

---

[03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) Air-Bearing Ways, Long-Travel Tailstock, and Internal Grinding Wheels

Every moving carriage and spindle on the machine floats on pressurized air films, eliminating friction, stick-slip, and mechanical wear. The tailstock, saddle, cross slide, main workhead spindle, and high-speed grinding spindle are all mounted on air bearings. Rather than fabricating specialized spindles from raw stock, Gelbart sourced surplus air-bearing spindles originally built for semiconductor fabrication machinery, which are widely available second-hand on eBay for only a few hundred dollars.

The tailstock incorporates an exceptionally long quill travel that extends from fully retracted inside the casting out to approximately 300 mm. This arrangement gives the compact machine an effective center distance of nearly 600 mm when the center is retracted, accommodating unusually long workpieces or through-spindle bar stock. The cross slide travel is equally generous: driving the cross slide forward provides ample clearance for traditional lathe turning tools, while racking it backward clears the work zone to engage the grinding head.

For internal cylindrical grinding, the external wheel can be removed and replaced by either a precision collet adapter or dedicated direct-mount threaded grinding mandrels. Rather than purchasing costly proprietary internal mounted points, Gelbart fabricates bespoke wheels using a waterjet cutter: “All what you do is take a used up grinding stone and cut out any size of wheel you want with a water jet cutter then you just mount it with epoxy on the shaft so you and this way you have access to the full range of wheel materials which are available for external wheels.”

- **Spindle sourcing:** Surplus semiconductor manufacturing air-bearing spindles purchased on eBay for roughly $200 each. - **Tailstock quill travel:** ~300 mm extension range. - **Maximum center distance:** Nearly 600 mm on a compact machine footprint. - **Internal wheel fabrication:** Waterjet-trepanned disks cut from depleted standard bench/surface grinding stones and bonded to steel shanks with epoxy.

---

[06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) Fabricating a 1-Micron Granite Bed and Control Features

Achieving one-micron precision requires an exceptionally rigid, thermally stable, and straight machine bed. Gelbart built the bed assembly economically using precision granite parallels—readily available commercial granite bars that are lapped parallel on all four sides to within one micron over their entire length. He bonded two pairs of parallels together using epoxy to create two structural "T" sections, which were then bonded to form the central guide channel of the bed.

To ensure proper geometric alignment, the assembly was clamped upside down onto an inspection-grade granite surface plate with calibrated gauge spacers defining the central way gap. Once the epoxy cured, the opposing guide ways were flat, coplanar, and aligned to a single micron. Because epoxy adhesives perform well under pure shear but fail under tension or peeling, through-bolts clamp the granite structure under permanent mechanical preload. Gelbart explains the structural logic: “Because like all adhesives epoxy is very strong in pure shear mode but it's very weak in other modes so by holding the parts under compression the only stress the epoxy is subject to is shear which tries to cut them apart but all other stresses are taken up by the compression on the bolt.”

In addition to full CNC automation, the machine includes digital readout (DRO) scales and manual controls so it can function as a conventional manual lathe if computer problems arise. The carriage also features a dedicated pneumatic tailstock lock and an overhead inspection microscope aligned with a live video monitor to inspect tiny cutters and workpieces in real time.

- **Bed material:** Commercial granite parallels ground/lapped to 1 µm across all four faces. - **Epoxy joint protection:** Heavy structural bolts keep epoxy bond lines under continuous compressive preloading. - **Manual override:** Dedicated digital readouts (DRO) allow manual turning operations independent of the PC. - **Visual assistance:** Integrated optical microscope displaying live magnified imagery of the cutting zone on a video screen.

---

[08:25](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=505s) Live Demonstrations: Thread Cutting and Precision Cylindrical Grinding

Gelbart puts the machine through two machining demonstrations. The first operation showcases single-point external threading under CNC control. Through the integrated video microscope feed, the monitor displays a high-magnification view of the sharp cutting tool engaging the workpiece. When the cycle resumes, the camera clearly captures fine metal chips curling cleanly off the tip as the synchronized axes sweep across the part.

Before running the grinding operation, Gelbart highlights a critical detail on the spindle nose: a pair of radial adjustment screws built into the chuck body. Regarding their utility when re-chucking parts, Gelbart notes: “These two screws allow you to zero the run out of the chuck to zero and that's very useful when you have to take a job out do some operation and put the job back in you can re-adjust the run out to a reference surface to zero.”

The second demonstration illustrates multipass CNC grinding. Gelbart activates the cutting fluid system and spins up the high-speed grinding spindle. Because the coolant delivery is precisely metered to a small, targeted stream, there is virtually no coolant splashing inside the work envelope. The grinding wheel traverses into the programmed position, feeds in smoothly across several passes, and begins peeling off spark-free microscopic metal layers with complete stability.

- **Turning demo:** Single-point CNC threading monitored under the live video microscope. - **Runout calibration:** Dual opposing adjustment screws allow chuck runout to be dialed down to absolute zero against an indicator. - **Grinding demo:** Multipass outer-diameter grinding with low-splash, low-volume targeted coolant flow.

## Notable quotes > [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) Like all adhesives epoxy is very strong in pure shear mode but it's very weak in other modes. — Dan Gelbart

## Mentioned Dan Gelbart, James Midgley, Skinner Chuck Company, eBay

## Video description Home built high precision air bearing CNC lathe and grinder having 1um (0.00004") accuracy.

[Source](https://www.youtube.com/watch?v=sFrVdoOhu1Q)

中文简报

盖尔巴特用自制空气轴承数控车床加工出1微米级零件 通过在预受压花岗石平行规上利用二手空气轴承悬浮所有轴，无需手工研磨即可直接切削加工出气密、无摩擦的配合件。 丹·盖尔巴特（Dan Gelbart）展示了一台从零开始自制的数控机床，兼具车削和外圆磨削功能，精度可达1微米。最初的演示是一个无需任何手工研磨的自作用空气轴承活塞组件。该设计通过采用二手半导体级空气轴承主轴、改进型防水斯金纳（Skinner）式卡盘，以及由商用花岗石平行规在螺栓永久预压下粘接而成的床身，消除了摩擦和磨损。系统采用与詹姆斯·米奇利（James Midgley）共同开发的定制数控软件，并配备了手动数显表（DRO）介入功能和检测显微镜，可支持灵活多样的原型开发工作流。盖尔巴特在最后演示了高光学放大倍率下的实时单点车螺纹，以及经校准实现零跳动、平稳且少飞溅的精密磨削。 丹·盖尔巴特展示了一台自制的车削与外圆磨削两用数控机床，加工精度可达1微米（0.00004英寸）。 (0:06) 所有主轴和拖板均悬浮在加压空气轴承上，采用的是单价约200美元的二手半导体制造用主轴。 (3:48) 机床床身由商用花岗石平行规用环氧树脂粘合成T型截面制成，并通过贯穿螺栓施加了持续的受压预载。 (6:20) 工件夹持采用了一种基于已停产的斯金纳设计改造的防水卡盘，配有径向调节螺钉，可将卡盘跳动调整至零。 (2:00)

Reading summary

Dan Gelbart presents a custom-built, dual-purpose CNC lathe and cylindrical grinder capable of achieving one-micron machining tolerances using air bearings and a granite bed. Gelbart demonstrates that ultra-high precision can be realized outside industrial cleanrooms by combining structural granite parallels and surplus industrial spindles with custom software. Granite Bed Fabrication and Compressive Preload (6:20) Gelbart constructed the machine bed from commercial granite parallels that were factory-lapped parallel on all four faces to within one micron over their entire length. To assemble the central guideway without custom casting, pairs of parallels were bonded with epoxy into structural T-sections while inverted against a precision granite surface plate, using calibrated gauge spacers to set the gap. Because epoxy adhesives perform well under pure shear but fail under tension or peeling, Gelbart fitted through-bolts to maintain permanent compressive preloading across the granite structure. This arrangement ensures that operating stresses act only in shear along the glue lines, preserving coplanar guideway alignment to a single micron. Frictionless Air-Bearing Ways and Spindles (0:06) Every moving assembly—including the saddle, cross slide, tailstock quill, main workhead, and grinding head—rides on pressurized air films to eliminate friction, mechanical wear, and stick-slip. Rather than manufacturing air spindles from scratch, Gelbart sourced surplus air-bearing spindles originally intended for semiconductor manufacturing equipment on eBay for approximately $200 each. To showcase the practical utility of extreme geometric accuracy, Gelbart presents a matched piston-and-cylinder pair machined without secondary lapping. When its air vent is covered, the assembly behaves as a self-acting air bearing that spins freely without physical contact or oil lubricant, a condition Gelbart notes can be verified with an ohmmeter showing continuous infinite electrical resistance across the rotating parts. Sealed Workholding and Shop-Fabricated Tooling (2:00) To handle abrasive grinding swarf and cutting fluid, Gelbart adapted an obsolete Skinner Chuck Company design that remains completely watertight across all jaw openings. The jaws are driven internally from behind via drive pins, preventing swarf from entering the radial slots. Radial pin holes drilled directly into the chuck face permit internal and external clamping from 0 mm to roughly 200 mm without changing primary jaws, while radial adjustment screws allow an operator to dial runout to zero when re-chucking parts. The geometry accommodates long workpieces with a tailstock quill extending roughly 300 mm to yield a maximum center distance near 600 mm, while the cross slide provides enough travel to alternate between turning tools and the grinding spindle. For internal grinding, Gelbart avoids costly commercial mounted points by using an abrasive waterjet cutter to trepan custom wheels from worn bench grinding stones, which are then bonded to steel shanks with epoxy. Integrated CNC Control and Live Machining Verification (8:25) Because off-the-shelf control software could not support the hybrid turning-and-grinding architecture and specialized machine hardware, Gelbart partnered with Vancouver engineer James Midgley to program a dedicated CNC software package. The machine also integrates digital readout scales for manual operation, a pneumatic tailstock lock, and an overhead inspection microscope aligned with a live video monitor to inspect tiny cutters and parts in real time. Gelbart verifies the machine through two machining tests: single-point external threading monitored live on the video feed to confirm clean chip formation, and a multipass cylindrical grinding sequence. The grinding spindle operates with a targeted, low-volume coolant stream that prevents splashing and misting while taking stable, microscopic passes across the workpiece. Gelbart illustrates that one-micron tolerances and self-acting aerodynamic fits can be achieved economically on a compact footprint, though building such a system requires careful structural preloading, access to surplus air spindles, and specialized fabrication methods such as waterjet-cut abrasive tooling and bespoke CNC software.

精炼阅读摘要

机械设计发明人Dan Gelbart展示了他自主制造的高精度车磨一体CNC机床，该机床利用预压花岗石床身、气浮支承与定制控制系统实现了1微米（0.001毫米）的加工公差，并免除了精密配合件所需的手工研磨工序。 气压配合验证与1微米超精密加工能力 (0:06) Gelbart通过一套加工完成的活塞与气缸套件验证了机床的1微米（约40微英寸或0.00004英寸）加工精度。该活塞装入气缸后处于无间隙且无明显晃动的滑动配合状态，在没有机油润滑的条件下可顺畅滑动。当用手指按住气缸顶部的气孔时，配合面呈现气密状态并立即浮起活塞；手动旋转时，内芯与外套可极长时间无阻力旋转，构成了自作用式动压空气轴承。 针对传统高精度密封件需要反复手工研磨的痛点，该设备加工出的工件无需研磨即可直接从机床取用。Gelbart指出，该配合件在运转时由于不存在机械接触，因此无需润滑油且不会产生磨损，其物理机制与电脑硬盘中的空气轴承相同。该非接触特性可通过欧姆表在旋转工件间进行电性能检测，显示为持续的无穷大电阻。 花岗石平尺与螺栓预压胶接床身结构 (6:20) 为保证机床的刚性、热稳定性与平直度，Gelbart采用四面平行度达1微米的市售商用花岗石平尺构建床身。装配时，将花岗石平尺倒置并压紧在检测级花岗石平台上，利用精密量块标定间距，随后通过环氧树脂胶接成两个对称的T型结构，固化后形成高平直度、共面且间隙精度达1微米的导轨基座。 针对环氧树脂在力学上抗剪切强、抗拉伸与剥离弱的特性，Gelbart在床身结构中引入通孔螺栓提供持续的机械压缩预载。贯穿螺栓承担拉应力并保持构件紧固，使胶接缝主要承受剪切力，从而保护胶层不脱胶。此外，机床床身配备了实时视频显微镜以监测微型刀具切削，并保留了独立的数显表（DRO）与手动控制装置，以便在电脑故障时作为手动车床运行。 全气浮运动导轨与半导体二手主轴应用 (3:48) 为彻底消除机械摩擦、爬行现象与导轨磨损，该机床的工件主轴、磨头主轴、拖板、横向滑板及尾座均浮动在加压空气膜上。Gelbart并未从毛坯加工专用主轴，而是以约200美元的单价从二手市场采购了半导体制造设备淘汰的二手气浮主轴，以低成本实现了微米级回转精度。 机床尾座套筒具备约300毫米的伸缩行程，当套筒完全收回时，紧凑机身的有效顶尖距可达到近600毫米，便于容纳较长工件或穿轴棒料。横向滑板同样配置了大行程，前推时可为常规车刀提供切削空间，后拉时则可完全避开加工区域，以便高速磨削主轴切入工件。 密封式斯金纳卡盘与定制双模CNC控制 (2:00) 市售标准CNC控制系统无法兼顾车床与磨床的双重硬件架构及特殊配置，为此Gelbart与温哥华软件工程师James Midgley合作开发了专用CNC控制软件，统一控制车削与磨削循环。 工件夹持系统改装自已停产的美国斯金纳卡盘设计。传统卡盘的径向卡爪槽容易吸入冷却液和磨削碎屑，而该卡盘采用背面驱动销驱动卡爪，卡爪本体在不同开度下均能遮蔽径向导槽，维持完全防水密封。由于精密加工切削力较小，卡盘端面直接开设有销孔，通过插入模块化定位销，无需更换主卡爪即可夹持0至200毫米直径范围的内外圆工件。主轴端部还配有径向对顶微调螺钉，便于在重新装夹时将参考基准面的径向跳动调零。 自制水射流砂轮与车磨实切过程演示 (8:25) 针对内圆磨削所需特种砂轮价格高昂且规格受限的问题，Gelbart利用水射流切割机直接从报废的标准外圆砂轮片中套料切割出定制磨盘，再用环氧树脂胶接在钢制轴柄上。这种制作方式使内圆磨削能够直接选用市场上各类标准外圆磨料材质。 在加工实切环节中，Gelbart演示了CNC单点外螺纹车削，机床集成的视频显微镜在屏幕上清晰呈现了刀尖平稳卷出细密金属切屑的微观过程。随后的外圆多刀次磨削演示中，高速磨头配合精准计量的低喷溅冷却液流切入工件表面，砂轮微量进给剥离金属表层且全程无火花，展示了整机在切削加工中的动态稳定性。 该机床证明了结合二手工业气浮核心组件、预应力天然花岗石胶接与定制控制软件，能以有限预算自制出达到1微米精度的车磨复合机床。不过，由于气浮支撑本身的刚度限制以及较小的微米级切削力特征，此类设计主要适用于超精密轻负荷精加工，而非重切削开粗作业。

Detailed notes — zh

## Background 本视频由 Dan Gelbart 于 2015 年 3 月 6 日发布在 YouTube 平台。视频简介表明，内容展示了一台加工精度达到 1 微米（0.00004 英寸）的自制超精密气浮数控车磨一体机。 ## TL;DR Dan Gelbart 详细拆解了他完全从零开始自制的一台 1 微米精度数控车磨一体机，并通过一组无需润滑即可无接触悬浮旋转的动压气浮活塞缸体直观证明了微米级加工公差的价值。除车削与磨头主轴采用半导体行业二手气浮拆机件外，全机各运动轴滑台均为自制气浮导轨，机身床身则巧妙采用花岗岩精密平尺通过环氧树脂胶接并辅以预应力螺栓紧固构建而成。该设备还整合了 James Midgley 开发的定制 CNC 软件、全封闭防水且可调跳动的特制卡盘、切削显微监控摄像头以及手动双模操作冗余。视频最后进行了超精密螺纹车削与外圆磨削的现场切削演示，印证了整机在减振、刚性与精度控制上的卓越性能。 ## Atmosphere & style 整体氛围严谨深邃、沉稳洗练，散发着顶级老派工匠与极客工程师特有的从容与纯粹。Dan 的讲解不带一丝浮夸营销气息，语言平实却句句切中结构力学与精密机械加工的底层本质。从指尖转动活塞时气浮无摩擦旋转的静谧手感，到显微镜头下刀尖平稳剥离游丝般金属切屑的微观特写，整段展示带给观众一种令人屏息凝神的精密机械美感与极度舒适的沉浸体验。 ## Bulletin - [00:06](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=6s) Dan Gelbart 自制了一台加工公差达到 1 微米（40 microinches）的高精度数控车磨一体机，各运动滑台与主轴全线采用气浮轴承以彻底消除摩擦与磨损。 - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) 机床床身利用市售商用花岗岩平尺搭配环氧树脂胶接而成，并通过高强度贯穿螺栓施加预紧力，确保胶缝仅承受纯剪切应力以维持长期尺寸稳定性。 - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) 设备核心的主轴与磨头单元采用了来自半导体淘汰设备的二手气浮主轴，单件成本仅需两三百美元，大幅降低了超精密设备的制造成本。 - [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) 机床搭载了在任意开度下均能保持水密并支持径向跳动调零的定制卡盘，并集成了显微摄像系统与手动双模运行机制。 ## Key takeaways - [00:06](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=6s) 1 微米加工公差可直接实现无需人工研磨的自润滑动压气浮配合，内外构件旋转时完全无机械磨损且电气绝缘。 - [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) 商业数控软件无法满足车磨复合及特殊机械控制需求，系统由工程师 James Midgley 进行定制开发。 - [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) 卡盘采用受 Skinner Chuck 启发的全开度水密结构，并通过驱动销与卡爪遮蔽设计彻底阻绝冷却液和碎屑侵入。 - [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) 卡盘卡爪预留插销孔，无需拆换卡爪即可快速完成内外径夹持切换，装夹直径覆盖 0 至约 200 mm。 - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) 全机大拖板、中托板、尾座、车削主轴与磨头主轴全面应用气浮轴承，实现真正的无摩擦进给与运转。 - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) 尾座具备约 300 mm 的顶针行程调节能力，使小型机床在顶针完全缩回时顶尖距达到近 600 mm。 - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) 车削与磨削两套高精度气浮主轴均来自二手半导体废旧设备，在 eBay 上以两三百美元的极低成本购得。 - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) 横向滑板具备大行程移动能力，既能容纳外圆车刀架与磨头，也能拆换为夹头或螺纹直装式内圆磨削构型。 - [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) 可通过水刀切割废弃大砂轮并用环氧树脂胶接至轴柄上，自制具备高端磨料特性的非标内圆磨削砂轮。 - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) 床身利用四面平行度在 1 微米以内的花岗岩平尺在基准平台上倒置胶接成 T 形双轨，确保了优异的共面度与开槽精度。 - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) 床身结构利用贯穿螺栓施加预压应力，使环氧树脂层仅承受其最具优势的纯剪切力，消除了受拉和剥离失效风险。 - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) 控制系统支持无缝切换至带 DRO 数显标尺的手动车床模式，防止软件崩溃导致停机。 - [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) 机床集成了带视频输出的微型显微监视系统，可实时在大屏幕上放大监测刀尖进给与微小切屑形成过程。 - [08:26](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=506s) 卡盘侧面配备双径向微调螺钉，可在工件二次装夹回装时将基准面的径向跳动彻底校正为绝对零跳动。 - [08:26](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=506s) 超精密磨削加工通过微量受控的冷却液供给，配合高刚性气浮磨头实现了微米级平稳磨削且无冷却液飞溅。 ## Detailed walkthrough ### [00:06](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=6s) 1微米精度的自制车磨一体机与气浮活塞演示 Dan Gelbart 展示了一台由他完全从零开始自制（scratch built）的超高精度数控车磨一体机。这台机床能够实现 1 微米（公制 1 µm，折合英制单位约百万分之四十英寸，即 40 microinches）的切削、车削和磨削加工公差。面对普通人最常产生的疑问——“为什么有人会需要一台精度达到 1 微米的机床？”，Dan 用加工现场的一个实物零件给出了直观解答。 ```mermaid flowchart TD accTitle: 动压气浮活塞圆筒配合示意图 accDescr: 展现活塞与缸体在1微米配合公差下的密封与无摩擦自浮动机制 A["高精度气缸与活塞<br>(配合间隙达到微米级)"] --> B{"密封顶部排气孔?"} B -->|"未密封排气孔"| C["完全顺滑滑动配合<br>(手感极其宽松自由)"] B -->|"按住密封排气孔"| D["绝对气密状态<br>(活塞被空气弹簧托住)"] C --> E["旋转测试"] E --> F["产生动压气浮效应<br>(Self-acting Air Bearing)"] F --> G["像滚珠轴承般无摩擦长久旋转<br>(欧姆表检测电阻无穷大/无接触)"] ``` Dan 拿起一组在该机床上加工出来的精密气缸套与活塞组件进行动态演示。活塞滑入缸体内时表现出极度顺滑的间隙配合（sliding fit），手感非常宽松自由；但一旦用手指堵住顶部的排气孔，整个气缸立刻呈现出完全的气密性，内部空气被死死锁住。更为神奇的是，只要随手旋转外筒或内部零件，零件就会像安装在滚珠轴承上一样长久且毫无摩擦地旋转。Dan 解释说，这实际上形成了动压气浮轴承（self-acting air bearing），正如机械硬盘中的气浮轴承一样，运转时内外表面之间根本没有任何机械接触，用欧姆表测量可以证实两者电气完全绝缘。针对这种配合精度，Dan 评价道：“so in other words if you made a bearing like this this bearing will never need lubrication and never wear out because there is no contact between the inner part and the outer part you can verify that with an OM meter while they turn it's the same idea as air bearing in a hard drive or air bearings and other self-acting air bearings devices”。如果是用传统方法，工匠必须耗费大量时间进行极其繁琐的人工研磨（lapping），而且很难保证批次公差；而在这台超精密机床上，零件刚下机床就已经达到了这种极致配合。 ### [02:00](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=120s) 定制CNC系统与特殊的防水卡盘设计 为了打造这台机床，Dan 亲自完成了全部机械硬件的从零制造。机床虽然是全功能的 CNC 设备，但数控软件部分并未采用现成的商业软件套件，而是由来自不列颠哥伦比亚省温哥华的软件工程师 James Midgley 专门定制开发的。Dan 指出，常规的数控软件之所以无法胜任，是因为这台机器兼具车床与磨床的双重功能，同时还整合了多项非常规的特殊机械控制要求。 在机械结构上，该机床的卡盘设计极为罕见，其灵感源自已停产的一家老牌美国厂商 Skinner Chuck 的经典设计。这种卡盘最核心的特点是：无论卡爪张开到什么开度，卡盘内部始终保持完全的水密性（watertight）。冷却液和碎屑根本无法侵入卡盘机构内部。水密结构是通过驱动卡爪的驱动销（drive pins）实现的，卡槽本身在任何移动位置下都被卡爪本体严密遮蔽。 - **小负载插销夹持**：由于整台超精密机床主要面向微切削和小负载工况，卡盘的卡爪上预留了插销孔，可通过插入定位销直接对外圆（OD）或内孔（ID）实施夹持，操作人员无需拆换卡爪即可完成内外夹持切换。 - **宽泛夹持范围**：结合标准卡爪夹持与插销扩展，该卡盘能够牢固装夹直径从 0 到约 200 mm 的各类工件。 关于为何拒绝现成软件并重构机械，Dan 表示：“The reason I couldn't use a standard software package is this machine is both a lathe and grinder and has some other special features so I wanted to have a customized CNC package.” ### [03:48](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=228s) 气浮导轨、半导体二手主轴与内外圆磨削配置 全机各运动轴向全面采用气浮轴承（air bearings）。床鞍大拖板（saddle）、中托板/横向滑板（cross slide）、尾座（tailstock）乃至主轴和磨头全部悬浮在气膜之上运转。Dan 特别指出，由于气浮轴承供气时存在一定的噪音，他在讲解前半段特意未通气。 ```mermaid flowchart LR accTitle: 气浮系统及主轴配置架构 accDescr: 机床整体运动轴与半导体拆机二手气浮主轴的布局 subgraph GuideWays["运动滑台导轨 (全自制气浮)"] G1["大拖板 Saddle 气浮"] G2["横向中托板 Cross-slide 气浮"] G3["尾座 Tailstock 气浮"] end subgraph Spindles["主轴单元 (半导体二手气浮)"] S1["车削主轴 Main Spindle"] S2["磨削主轴 Grinder Spindle"] end GuideWays --> MachineBase["花岗岩精密床身"] Spindles --> GuideWays ``` 机床尾座同样浮动在气浮轨道上，其顶针轴具备极长的行程调节范围：从顶针完全缩入尾座体内到完全伸出，行程长达约 300 mm。这种构型赋予了小型机床惊人的装夹适应性：当顶针完全缩回时，顶尖距（center distance）接近 600 mm，这在同体量的小型车床上极其罕见；若工件为长棒料并可穿入尾座内孔，所能容纳的加工长度还会进一步增加。 整台设备中仅有两个核心部件并非 Dan 纯手工制造：即车床主轴与磨头主轴的气浮轴承。这两套单元全部来自于半导体设备领域的淘汰二手拆机件（surplus semiconductor machinery units）。Dan 透露，半导体行业大量使用高精度气浮主轴，在 eBay 等二手交易平台上只需花费两三百美元就能买到这种性能顶级的二手气浮主轴，性价比极高。 在磨削加工的扩展性方面，横向滑板具备超长的行程行程： - 向前移动滑板时，可为标准车刀刀架留出足够的车削回转空间； - 将横向滑板整体后移，则可让出充裕的空间布置磨头。 - **内圆磨削改装**：外圆砂轮可以方便地拆卸，更换为内圆磨削安装座。用户既可以通过筒夹夹头（collet adapter）夹持小柄径内磨砂轮，也可以采用带螺纹直接拧在主轴端部的直接安装式（direct mount）专用内磨砂轮，以获得更高的刚性。 - **砂轮水刀切割法**：对于非标尺寸的内磨砂轮，Dan 介绍了一种绝妙的自制技巧：只要有一台水刀切割机（waterjet cutter），拿一块磨损报废的大型废砂轮，用水刀直接切割出所需任意直径的小砂轮片，再用环氧树脂（epoxy）胶粘固定在轴柄上。这种方法能让自制内圆砂轮直接享受到市面上各类高端外圆砂轮的丰富磨料材质特性。 关于零件采购与成本，Dan 直言：“The only two parts here which are not made from scratch is the air bearings for the main spindle and the air bearings for the grinder spindle which are Surplus semiconductor Machinery units which are very cheap you can buy those on eBay for a couple of hundred bucks each because a lot of Machinery in the semiconductors is air bearing based.” ### [06:20](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=380s) 花岗岩平尺环氧粘接床身与手动/显微辅助功能 想要实现 1 微米的综合加工精度，必须依赖两条铁律：超高刚性精度的导轨床身与超精密的主轴系统。主轴可以通过二手半导体气浮件解决，而床身的微米级制造则蕴含着精妙的结构力学设计。Dan 采用的方法是购买商业化的花岗岩精密平尺（granite parallels）。这种平尺成本并不昂贵，但其四个工作面在全长范围内的平行度天然保证在 1 微米以内。 ```mermaid flowchart TD accTitle: 花岗岩床身组装工艺 accDescr: 利用花岗岩平尺、环氧胶接与预应力螺栓制造微米级床身的步骤 A["采购4面平行度达到1微米的花岗岩平尺"] --> B["在精密花岗岩平台上倒置组装"] B --> C["加入极精密间距规 (Precision Spacers)"] C --> D["使用环氧树脂 (Epoxy) 胶接成'T'形结构"] D --> E["双T型组合构成导轨床身并固化，确保两导轨共面"] E --> F["贯穿高强度螺栓施加预应力预紧"] F --> G["胶层完全处于受压状态 (Pure Compression/Shear)<br>消除受拉与剥离应力"] ``` Dan 将两根花岗岩平尺用环氧树脂粘结成一个“T”字形结构，再将两组“T”字形平尺组合固定，构成了机床的双轨床身基座。组装粘接时，整个床身倒置在一块高精度的花岗岩平台上，中间垫入高精度测块/定距垫片（spacers）。待环氧树脂固化后，两个平行的主导轨滑动面能达到绝对的共面（co-planar）状态，中间的导轨开槽间距公差也严密控制在 1 微米之内。 更为关键的是胶接接头的受力设计。在结构上，Dan 使用了粗壮的大直径螺栓贯穿床身，使花岗岩粘接缝始终保持在强力预压（compression）受力状态。Dan 解释了粘接力学的基本原理：“because like all adhesives epoxy is very strong in pure sheer mode but it's very weak in other modes so by holding the parts under compression the only stress the epoxy is subject to is shear which tries to cut them apart but all other stresses are taken up by the compression on the bolt”。通过这种螺栓机械预紧力，环氧胶缝彻底避免了剥离应力与拉伸应力，只承受其最为擅长的纯剪切应力，确保了床身数年如一日的超高尺寸稳定性。 辅助配置与冗余设计： - **手动双模系统**：即使数控电脑系统发生软件崩溃或故障，这台机床也能无缝切换为带数显标尺（DRO - digital readouts）的手动精密车床使用。 - **尾座气浮锁定旋钮**：用于定位后机械锁紧尾座。 - **集成显微镜检测系统**：机床上集成了一个带视频输出的电子显微镜，在进行微小精密零件加工时，可将显微镜头对准切削区，实时放大并将刀尖切削状态投射在操作面板的监视器屏幕上。 ### [08:26](https://www.youtube.com/watch?v=sFrVdoOhu1Q&t=506s) 现场加工演示：高倍放大车螺纹与外圆磨削 完成了硬件构造与设计理念的梳理后，Dan 接通气源与电源，开机进行现场加工动态演示。第一项演示任务是超精密螺纹车削。数控系统加载预设的螺纹切削宏程序后，Dan 启动了机床上的高倍显微摄像头。屏幕上实时呈现出车刀刀尖与工件表面接触的超高清微观画面。随着程序执行（点击 Resume），可以极其清晰地观察到微米级车刀刀尖平稳吃刀、薄如游丝的细小金属切屑均匀剥离脱落的全部运刀轨迹。 第二项演示是多道次精密外圆磨削（multipass grinding）。在开机前，Dan 补充指出了卡盘上的另一项精巧设计——偏心跳动微调机构（runout adjustment）。卡盘侧面设有两个径向调节螺钉，操作者通过调校这两颗螺钉，可以将工件装夹后的径向跳动彻底校正为绝对的零（zero runout）。Dan 强调，当工件需要拆下机床执行其他加工再重新回装二次加工时，该功能具有不可替代的价值，可快速将基准面的跳动精确对零。 磨削过程如下展开： 1. 预先录入多道次步进磨削程序； 2. 开启磨削冷却液供给泵； 3. 启动高转速气浮磨头主轴； 4. 进给机构切入，由于冷却液流量控制得极为微小精准，高速旋转下机床周围几乎没有任何液体飞溅； 5. 伴随着均匀平稳的切削接触，砂轮开始在微米尺度上精准剥离金属表层。 Dan 边展示边提醒观众注意细节控制：“Notice that there is very little splashing from the coolant because the coolant flow is quite quite small now it's starting to grind”，以直观流畅的切削过程印证了整台机床在刚性、减振与气浮精度控制上的优异性能。 ## Mentioned Dan Gelbart, James Midgley, Skinner Chuck, eBay ## Video description Home built high precision air bearing CNC lathe and grinder having 1um (0.00004") accuracy. [Source](https://www.youtube.com/watch?v=sFrVdoOhu1Q)

Source quotes

[6:20] Dan Gelbart: Like all adhesives epoxy is very strong in pure shear mode but it's very weak in other modes.

Original transcript

[0:06] hi this is Dan Gart with a short video [0:09] of a scratch built very high Precision [0:13] lays and grinder as a machine you're [0:15] looking at can cut turn and grind parts [0:19] to a tolerance of one [0:21] micron for those of you are used to [0:23] Imperial units 40 millions of an inch so [0:27] the first question which comes to mind [0:29] is why a fellow need a machine Accura to [0:31] one micron and it turns out there's a [0:33] lot of jobs where you need a machine [0:36] like this and I'll show you one example [0:39] like here is a cylinder and a piston [0:43] which is made on this lace and you can [0:46] see that the Piston is a complete [0:49] sliding fit in the [0:51] cylinder it it's completely loose fit [0:54] now if I seal off the air vent on [0:58] top you can see it's completely [1:02] airtight and another nice property [1:05] because it's so accurate if I spin it it [1:09] spins freely as if it's on ball bearings [1:12] but it spins like a self-acting air [1:14] bearing and the same is true if I spin [1:17] the inner piece it will spin [1:19] frictionlessly for a long time so in [1:22] other words if you made a bearing like [1:23] this this bearing will never need [1:26] lubrication and never wear out because [1:28] there is no contact between the inner [1:30] part and the outer part you can verify [1:33] that with an OM meter while they turn [1:35] it's the same idea as air bearing in a [1:38] hard drive or air bearings and other [1:40] self-acting air bearings devices so this [1:43] is one example of a part that if to do [1:46] it without a machine like this you'll [1:48] have to do it by time consuming lapping [1:51] and it'll be quite hard to get parts to [1:54] fit to the Tolerance on this machine it [1:56] comes out like this straight of the [1:58] machine [2:00] so now let's go over the piece by piece [2:03] how the machine is built because it's [2:05] actually not that difficult to build a [2:07] machine like this so this is a full CNC [2:12] machine I built the machine itself from [2:14] scratch but the CNC software was done by [2:17] somebody else an engineer by the name of [2:20] James midley out of Vancouver BC the [2:24] reason I couldn't use a standard [2:25] software package is this machine is both [2:28] a Las and grinder and has some other [2:30] special features so I wanted to have a [2:33] customized CNC package so just let's go [2:35] over the machine part by part because [2:37] there's a lot of parts of this machine [2:39] which are different than a normal CNC [2:42] machine and then I'll run it to see how [2:44] it works so let's start with a Chu the [2:47] chu is an unusual design it's based on a [2:52] extinct American design by a company [2:55] called Skinner Skinner Chuck and what is [2:58] unique about this Chuck that at any [3:00] opening it stays completely watertight [3:04] so when I open the jaw's or close the [3:06] jaw the Chuck will stay completely [3:09] watertight now uh this is done through [3:12] Drive pins which Drive the Joe's and the [3:15] slot is covered with the joy itself [3:17] something else about this Chu that [3:19] because this slay is designed for very [3:22] small loads I can grip Parts through [3:26] pins so I can insert pins in the chu and [3:30] I can grip Parts on the ID or the OD [3:33] without having to change Jaws so these [3:36] pins give the chu a very wide range plus [3:40] a regular gripping range of the Jaws so [3:43] this Chu can grip anything from zero to [3:45] about 200 mm [3:48] diameter something else which is [3:50] different about this L is a tail stock [3:53] the tail stock which is also on air [3:55] bearings of course H has a very long [3:58] travel all the way from the center being [4:01] inside to the center being fully [4:03] extended about 300 mm now this is [4:07] interesting because it allows you to [4:09] have a very long Center distance for a [4:11] very small LA because when the center is [4:14] inside I have almost 600 mm Center [4:19] distance which is quite a lot for a [4:21] small L like this and even more if a the [4:24] bar can go [4:25] inside now all the parts you see r on [4:29] airb bearings as you'll see in a moment [4:32] I'm just not turning it on yet because [4:33] air bearings are a bit noisy so this [4:36] floats on air bearings this whole saddle [4:39] flows on air bearing the crosslight [4:42] floats on air bearing the main spindle [4:45] and the grinding spindle are all on air [4:47] bearings now the only two parts here [4:50] which are not made from scratch is the [4:52] air bearings for the main spindle and [4:55] the air bearings for the grinder spindle [4:57] which are Surplus semi conductor [5:00] Machinery units which are very cheap you [5:02] can buy those on eBay for a couple of [5:04] hundred bucks each because a lot of [5:07] Machinery in the semiconductors is air [5:09] bearing [5:11] based so the travel of the Cross light [5:14] is long enough that I can move it [5:17] forward and have enough room for lace [5:19] tooling or I can move the whole crlight [5:21] back and I have room enough for the [5:23] grinder I can also use it in internal [5:26] grinding this grinding wheel comes off [5:29] as you will see later and I can put [5:32] internal grinding mounts for example I [5:35] can put a colet adapter here to hold [5:38] with collet internal wheels or I can put [5:41] direct Mount internal grinding wheels [5:45] which are threaded right on the spindle [5:46] for more rigid Wheels which can go [5:49] inside and these are actually made to [5:52] suit the job so these internal grinding [5:55] wheels are made to suit the job and if [5:57] you have a water jet cutter they're very [5:59] easy to make all what you do is take a [6:01] used up grinding stone and cut out any [6:04] size of wheel you want with a water jet [6:06] cutter then you just mount it with epoxy [6:10] on the shaft so you and this way you [6:13] have access to the full range of wheel [6:15] materials which are available for [6:17] external wheels so now some other things [6:21] I want to explain is how to get to the [6:23] accuracy because to get to one micron [6:26] accuracy you need to start with a very [6:28] very good B and very good spindles I [6:31] explained that the spindles you can buy [6:34] surplus the bearings but I want to [6:36] explain how you can make a bed accurate [6:38] to a micron so it turns out you can buy [6:41] quite economically Granite parallels [6:44] which is just a bar of granite which all [6:47] four sides are parallel to a micron over [6:50] the whole length and you build up the [6:52] bed by bonding with [6:55] epoxy one bar to another bar to form a t [7:00] and two of those t's to form a bed of [7:03] course when you glue it up the whole [7:05] thing is flipped upside down on a granny [7:08] table and this there is very accurate [7:10] spacers put inside so once the epoxy [7:13] cures this surface and this surface are [7:17] co- planer and the Gap here is accurate [7:20] to a micron now the glue joints are held [7:24] under compression by these bolts this [7:28] big this big thing is a head of a bolt [7:31] which holds a bed under compression [7:34] because like all adhesives epoxy is very [7:38] strong in pure sheer mode but it's very [7:40] weak in other modes so by holding the [7:44] parts under compression the only stress [7:47] the epoxy is subject to is shear which [7:49] tries to cut them apart but all other [7:51] stresses are taken up by the compression [7:53] on the bolt now this lce has another [7:56] feature that if anything goes wrong with [7:58] the software you can use it as a manual [8:01] a with digital readouts so these are the [8:03] readouts for manual a mode and that's [8:07] about it this is to lock the tail stock [8:10] another item which is convenient is a [8:12] built-in [8:13] microscope which you can place when you [8:16] want to do small work you can place here [8:18] and see it displayed here so this is a [8:21] general overview and now we start up the [8:23] machine and we show it work okay so now [8:26] I'll just demonstrate one job is cutting [8:28] a thread this is all programmed here to [8:31] cut a thread you can see through the [8:33] video camera looking down a magnified [8:37] cutting action this is the tip of the [8:39] cutting tool so if we push resume you'll [8:43] see it cutting a thread here you can see [8:46] the chip coming [8:48] off and you can see all the motions [9:08] okay okay now we can stop [9:15] it okay now we'll do a grinding example [9:19] so we program it for multipass [9:23] grinding turn one one thing I forgot to [9:26] mention before that this Chu also has a [9:30] run out adjustment these two screws [9:34] allow you to zero the run out of the chu [9:36] to zero and that's very useful when you [9:39] have to take a job out do some operation [9:42] and put the job back in you can R adjust [9:45] the run out to a reference surface to [9:47] zero so it's now set for grinding we [9:50] turn on the coolant turn on the [9:53] spindle and start grinding [10:05] so it's still not touching the metal in [10:07] a few seconds it'll start taking off [10:13] metal notice that there is very little [10:16] splashing from the coolant because the [10:18] coolant flow is quite quite small now [10:22] it's starting to grind