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  1. #1
    Join Date
    Mar 2013

    BT30 spindle built from scratch, with ATC possibility.

    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.

    Attachment 244004

    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.

    Attachment 244006

    Attachment 244008

    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.

    Attachment 244010

    Attachment 244012

    Latheing a small part for the gripper.

    I made this out of Orvar, too.

    Attachment 244014

    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!

    Attachment 244016

    Attachment 244018

    Some hours later...

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

    Attachment 244020

    Attachment 244022

    Turning the shaft around and boring out the shaft.

    Attachment 244024

    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.

    Attachment 244026

    Attachment 244028

    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.

    Attachment 244030

    Attachment 244032

    Attachment 244034

    Attachment 244036

    Attachment 244038

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

    It is made of Uddeholm Impax Supreme.

    Attachment 244040

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

    Attachment 244042

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

    Attachment 244044

    Attachment 244046

    Surface grinding the parts to tolerance on both sides.

    Attachment 244048

    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.

    Attachment 244050

    Then off to the cylindrical grinder.

    Attachment 244052

    Mmmmmmmm... Ground parts!

    Attachment 244054

    And they fit, too!

    Attachment 244056

    Attachment 244058

    Attachment 244060

    Attachment 244062

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

    Attachment 244064

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

    Attachment 244066

    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.

    Attachment 244070

    Attachment 244068

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

    Attachment 244072

    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.

    Attachment 244074

    Ground some small parts for the gripper.

    Attachment 244076

    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.

    Attachment 244078

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

    Attachment 244080

    Attachment 244082

    Attachment 244084

    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.

    Attachment 244086

    Attachment 244088

    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.

    Attachment 244090

    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).

    Attachment 244092

    Attachment 244094

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

    Attachment 244096

    Attachment 244098

    Attachment 244100

    Attachment 244102

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

    Attachment 244104

    Attachment 244106

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

    Attachment 244108

    Attachment 244110

    Attachment 244112

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

    Attachment 244114

    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.

    Attachment 244116

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

    Attachment 244118

    Attachment 244120

    Made some drive dogs, they are made of Impax.

    Attachment 244122

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

    Attachment 244124

    Attachment 244126

    Attachment 244128

    Attachment 244130

    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.

    Attachment 244132

    Attachment 244134

    Attachment 244136

    Attachment 244138

    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.

    Attachment 244140

    Attachment 244142

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

    Attachment 244144

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

    Attachment 244146

    Attachment 244148

    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!

  2. #2
    Join Date
    Mar 2009

    Re: BT30 spindle built from scratch, with ATC possibility.

    Wow.Beautiful work.Makes you appreciate what goes into the making of a spindle.As you say you have the machines and more importantly you know how to use them.Thank you for the pictures.
    What improvements did you make from the first spindle you made?

  3. #3
    Join Date
    Nov 2007

    Re: BT30 spindle built from scratch, with ATC possibility.

    Intense tools and skills you have going.
    My spindle has like 3 bellview set washer stack, I see like 15 in your drawing.
    Anyway very impressive work.

  4. #4
    Join Date
    Jan 2005

    Re: BT30 spindle built from scratch, with ATC possibility.

    Now how much for one?

  5. #5
    Join Date
    Mar 2013

    Re: BT30 spindle built from scratch, with ATC possibility.

    Thanks guys, I'm glad you like it so far! Right now the housing is being wire-EDM'd. I'll show a pic in a day or so.

    shedbob, About the design, here is the new vs the old one. Quite the difference if you ask me, hehe. Not only that, the shaft was made from some unknown steelbar, non tempered, the taper compared to the bearing seats had a lot of run-out, back-bearing no pre-loading, and so on...

    Attachment 244800

    mountaindew, I use 93 springs, 3 stacked parallel in 31 groups. At 50% compression one spring generates around 1000N force, I need around 3000N force, that's why I use 3 in parallel. I can't compress the spring more than 75% for maximum lifetime, the compression length between 50% and 75% is 0.125mm. I need around 3.5mm stroke + some safety margin, that's why I chose 31 stacks, that way I'll get around 3.9mm stroke and a force of 3000N.

    hjl4, Sorry, but it's not for sale.

  6. #6
    Join Date
    May 2005

    Re: BT30 spindle built from scratch, with ATC possibility.

    Amazing build, thanks for showing it in such a detail...!

    ● Distribuidor Syil en Argentina ● "www.syil.com.ar" ●

  7. #7
    Join Date
    Jan 2005

    Re: BT30 spindle built from scratch, with ATC possibility.

    I kind of figured "Not for sale".
    But if you made more then one, I bet you people would be interested.
    Business potential?

  8. #8
    Join Date
    Mar 2013

    Re: BT30 spindle built from scratch, with ATC possibility.

    PEU, Thanks man!

    hjl4, Well, the thing is it would've been just as expensive or expensiver as a "real" BT30 spindle. The amount of time i put into this spindle is huge! And because more or less all the stuff i do is in manual machines it doesn't go quicker to make one or 10 spindles. And one more reason, I don't want to "mass produce" stuff for others at my job, I got the great privilege to use the machines after work, I wouldn't want to loose that for anything.

  9. #9
    Join Date
    Mar 2013

    Re: BT30 spindle built from scratch, with ATC possibility.

    When I got to work this morning the wire-edm had only run halfway, started it again after work. It SHOULD be done tomorrow morning.

    Click image for larger version. 

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  10. #10
    Join Date
    Oct 2010

    Re: BT30 spindle built from scratch, with ATC possibility.

    So we share that Privileg great
    Question do you do wire EDM at home and if Yes is it a build or bought one ? EDM is now on my List ..

  11. #11
    Join Date
    Mar 2013

    Re: BT30 spindle built from scratch, with ATC possibility.

    Tkamster: Lol, I don't own a wire-EDM, my job got one. :P

    Here we go! Wire-EDMing done!

    Attachment 245044

    Started machining the first bearing seat, got really bad surface finish, but that doesn't matter, will grind it later. :P

    Attachment 245046

  12. #12
    Join Date
    Mar 2013

    Re: BT30 spindle built from scratch, with ATC possibility.

    Time for another update!

    Milled the back bearing seat in the housing today, left some material for grinding.

    Attachment 245116

    I also made a "clamping plate" for the grinder/housing for better clamping when grinding.

    I MIGHT start the cylindrical grinding tomorrow, if not then i'll do it in 2 weeks.

    Attachment 245118

    Attachment 245120

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