Okay, first off, I've been building this spindle for a few months already, but only got a buildlog on a Swedish forum, then I thought wny not share this build with you guys too!

For you who wounder, I work as a tool maker for mold injection, that's why I have access to all the machines.

Oh yeah, almost forgot, I'm making this spindle because milling spindles really fascinate me. I have a small chinese bench-top mill that I re-built to 99% and made a new BT30 spindle for (that was ~1½ year ago.) But the design and my job wasn't that great. (Because I didn't have enough knowledge and not access to good enough machines) But with the first spindle I learned a lot, so now move on to the next one!

Let's start with a section view of the spindle design. I might make some minor changes to the design through out the build tho.

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Manufacturing time!

When the spindle is done, I need to measure the run-out of the tool taper somehow. So I started making a "test bar". I used Uddeholm Stavax for the test bar because it is a rust-resistant tool steel which can be tempered.

I lathed the shaft to nominal diameter + ~0.4mm, which will later be removed with the cylindrical grinder. Then I turned the part around and lathed the tool taper, bored and tapped the hole for the draw-bar.

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Then I started making the rings which will offset the angular-contact bearings(for added stiffness) and also the rings to adjust the pre-load in the back roller-bearing(the bearing have a tapered seat on the axis, so the harder I tighten it on the bearing seat the less clearance it will have, or in my case, preload.)

The rings are made of Uddeholm Orvar Supreme(2242), it is a good "all-round" tool steel.

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Latheing a small part for the gripper.

I made this out of Orvar, too.

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Now, let's get serious and start making the spindle shaft!

For the previous small parts I used the smaller lathe, now for the shaft i used the heavy-duty one! I actually like the smaller one better, but for this job the bigger one is better suited.

This, too is made of Orvar, quite a big chunk of tool steel!

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Some hours later...

Annnnnd it's done! Well, operation 1 atleast. :P

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Turning the shaft around and boring out the shaft.

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Making the labyrinth-seal for the front-bearings. I made the play around 0.2mm/side.

These 2 are made of Stavax, because it is rust-resistant.

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I lathed the front-lid for the spindle and drilled the holes for mounting. But I accidentally f*****-up.(got the hole and head clearance off-center to each other) To fix it, I used the sinker-EDM(sure i could've fixed it in the mill/drill-press, but it looks muuuuch better EDM'ing it! ). Cylindrical ground a electrode for me to use.

The front-lid is made of Stavax too, for it's rust-resistant properties.

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While the sinker-EDM was running I made the drawbar in the lathe.

It is made of Uddeholm Impax Supreme.

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I sent all the Orvar and Stavax parts off to tempering! Now there around 52HRC hardness. Nice!

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Now the precision work begins! For higher parallelness, I began with grinding the magnetic table.

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Surface grinding the parts to tolerance on both sides.

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The spacer rings between the front AC-bearings need to have a really tight parallel tolerance, I measured the parallelism against a flat-surface and a 1µm dial-indicator. I measured the parallelism to 2µm on the bigger ring, on the smaller one it is 1µm. Yeah, I'm happy with the result.

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Then off to the cylindrical grinder.

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Mmmmmmmm... Ground parts!

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And they fit, too!

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Measuring the axial-play in the labyrinth seal, turned out perfect!

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Some ground and "to be ground" parts for the gripper assembly.

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Time to grind the spindle shaft!

First of all, I started grinding the tapered bearing-seat for the roller-bearing and measuring the taper in the measuring machine.

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Some hours later, it was finally done! And my god it is beautiful.

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Next up, the test bar! Ground in a single clamping to get 0 run-out.(or atleast verrrryyyy little run-out)

Made a short video confirming this.
https://www.youtube.com/watch?v=I8nkFkNeFhU

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Ground some small parts for the gripper.

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I bought a roller bearing and some lock-nuts for the spindle.

The roller bearing is a SKF NU 208 ECKP-C3, (I wanted a bearing with lesser play, but the only one they got was with C3 play, oh well.) This bearing is kinda special too, because of it's tapered bearing seat (1:12 taper).

The nuts are SKF KMT 10 and SKF KMT 8, high-precision locknuts.

I already got 2x SKF 7210 BEGAP AC-bearings from my previous spindle build, I'm re-using those.

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Time to grind the thread for the lock-nuts! Yes, I said grind...

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When the ATC is in progress, you want a stream of air to clean the taper, made a small hole (~1.3mm) through the drawbar to get that stream of air.

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Just for fun, I tried mounting the AC-bearings and the spacer rings and check the run-out of the bearings.

Yeah, I'm quite happy with the result.
https://www.youtube.com/watch?v=JG0BBG3qgeU

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Ground the tool taper - check.

Run-out of the bearing seats was around ~1-2µm.

Feels like the run-out of this spindle is going to be really minimal. My guess/hopes are around 10µm, 200mm out from the taper(that's the length of the test bar).

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Time to sinker-EDM the large hole in the spindle for the drawbar assembly.

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And sinker-EDM the thread to hold the gripper assembly in place.

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A huge chunk of Uddeholm Impax, will be the spindle housing! Raw material weighs 23.3kg!

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First tempo done. Should weight around 16-17kg.

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Did the next tempo in the CNC-mill. Milled in the height and front diameter +0.2mm saved for grinding.

Also drilled 2 holes thru the whole housing, those holes will be used as starting-holes for the wire-EDM.

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Ground 2 electrodes to sinker-EDM the space where the gripper opens.

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Made some drive dogs, they are made of Impax.

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Milled the electrodes for the "drive dog track" for the spindle.

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Milled and sinker-EDM some drainage tracks for the front-lid, so liquids don't enter/get stuck in the labyrint seal.

Then I polished it.

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Time to fit the roller-bearing. Right now there is ~0.07mm radial play in that bearing, but I want a preload of a few µm. That's why the bearing seat have a 1:12 taper, the harder I tighten the nut the more the inner ring expands. That's why I need a spacer ring, ground to tolerance beneath the roller bearing so I don't over-tighten the nut and get too much preload.

I used a dial indicator with 1µm resolution to check the radial clearance in the bearing, then I tightened the nut more and more until I got a pre-load. Then I measured the distance beneath the bearing with gauge blocks.

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Lathed, ground and sinker-EDM the gripper, All that's left is to split it in the wire-EDM.

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Just for fun, I assembled most if the stuff I could. I can promise you, this is a sturdy piece of metal!

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Well, that's a few months work up til' now, hope you like it so far!

I'm going to start wire-EDM earliest next week.

If you have any questions or design improvements(It might be a little late for that now but one of the reasons I'm making this spindle is to learn something), feel free to tell me!