[H.O]

That's not a bad idea! I will have to look into that, the space is pretty tight in there and the ball-joint will have to hold up for the ~3kN force that springs asserts on the drawbar while clamping the tool.

Thanks!!
/Henrik.

[gbowne1]

I would like to see other versions of this same exact spindle design made. I'd be interested in a 40 or 50 taper NMTB, CAT or BT. Heck I'd even pay someone to make me one exactly like the one in this thread, except in my taper.

That brings me to the next couple questions. What's the difference between CAT and BT? Is this a ISO or DIN specification?

Thanks,
Greg

[H.O]

The taper is the same but there are differences in the flange. On the BT the flange is symetrical, the groove for the toolchanger "fingers" is located in the middle of the flange axially and there are two notches for the spindle drivedogs located 180° appart. I think that on the CAT the groove is offset axially and there's either only one notch for the a drivedog (I'm certanly not sure about that) and/or there's an extra notch in the flange for locating the tool in the tool-changer carousel OR there might be two drive-dog notches notches but of different size.

[gbowne1]

Henrik,

I've just read somewhere else that the other difference is the thread. One is a metric size, the other is a SAE.. like 5/8-11.. the other difference is the flange.

I don't have the capabilities to build this spindle, but I definitely would pay someone.. even if I have to buy the bearings and the materials needed to make this for me.

I'm not really a metric guy.. I'd prefer a SAE size.. but someone a few years back gave me some old CAT45 holders to use as bookends. but I've seen here at least in my area that 40 or 50 taper CAT or BT are pretty common.. at least at the shops I visited. Altho.. I'd love to be able to use a 2" endmill .. I do have one.. just one.. a Weldon the kind with the wavy edge flutes. I don't see myself using more than a 1" dia that I have.

The Lyndex/Nikken Rep offered to sell me a complete set of whatever I want to use, complete with all the pull studs I could ever want.. plus a few extras. While I have some Centaur ER32 collets, I mostly use TG100/100TG collets from Kennametal/Ericson.. in a Ericson NMTB 40 holder.

I originally planned to put the spindle I chose into a old BP J-Head casting bore that I have laying around. But I think I'll just make my own like you did.

I'm planning my toolchanger to be a side mounted carousel..

BTW, How is your coolant supplied/delivered? Through spindle or located around the head?



Think if I paid you enough you could make me one, If I bought all the supplies?

[H.O]

Hi,
Yeah, you're right, the BT has metric thread for the pullstud, M12 for size 30, M16 for size 40 etc.

Regarding the coolant, I don't have any...I "manually" spray the coolant on the work from time to time. Anyway the spindle is not designed for thru spindle coolant.

This little machine of mine is not really up to the task of fully supporting a spindle like this. What I originally was aiming for was repeatable tool-changes and at the time I was planning for another machine build which will not happen since I now got a larger knee-mill.

If you've read thru the thread you probably know that I'm not up to the task of building these for others, I'm not even sure it works at all.... Besides, I don't have the machinery to do so at home so I'll have to squeeze it in when the machines at works are available etc. So, I'm sorry but I'll not be able to make one for you...

[TAPIAL]

Hi,

This is my first time writing something on the forum and saw what you put information regarding tool change it is briliant.

Thanks

Ashok Kumar

[Adamj12b]

Well its been a few months since your last update. Has there been any progress? How do you like the knee mill?

-Adam

[H.O]

Hi,
No, no progress on the spindle project :-(

The current status is that the spindle itself is stright and runs true. When fitting a tool and pulling it up in the taper with a threaded instead of the gripper type drawbar the runout is very reasonable, below 0.01mm.

When using the gripper type drawbar something goes wrong and the runout is totally unacceptable. My theory, as I've written before is that the drawbar pushes radially on the top of the tool making it "tilt" in the taper. So close, yet so far away - frustrating. Someday I'll open up the drawbar tube even more and see if that helps.

Progress is being made on the knee-mill although it a slow project. I'm getting there though, I'll make a thread here in a while.

/Henrik.

[Herbertkabi]

hi Henrik,
I have a new Hommel SK-30 spindle - bought few months ago because want to build ATC direct drive Spindle.
What is different SK30 v.s. BT30 ? I see a lot of SK´s in ebay.de, only one BT :-(
Why SK has this grinded cylindrical part on the end of cone ? Can I just cut it?
I did not find any dimensions about your drawbar, especially OD of ball-gripper - can you give?
Seems I have to enlarge the centre hole diameter (1/2" long bore and 18mm wheres cone ending) of my Hommel Spindle ... its damn hard :-(
Regards,
Herbert

typical SK:
http://cgi.ebay.de/Spannzangenfutter...1%7C240%3A1318

[H.O]

Hi,
The kind of SK holders you are reffering to are the ones used in manual machines. They have an internal thread at the top that the drawbar threads into in order to pull the tool up into the spindle.

The BT has the exact same taper as the SK but they lack the cylindrcal part at the top so they are shorter in order for a pullstud to be fitted that matches the drawbar mechanism in the spindle.

As long as the taper size is the same, ie. 30 in your case and you don't actually have an ATC it doesn't really matter if you buy BT30 or CAT30 or ISO30 toolholder, they all have the same taper and all you need to do is to get the correct pullstud that fits both the holder and gripperin the spindle.

I'll look up the dimensions you asked about tomorrow and post them here.

/Henrik.

[Herbertkabi]

Thanks,
In principle I like to build something lesser, I´ll finish this spindle of course, but I like smaller one much more and ATC self-evident. Just high speed spindles I have built up till boredness.
Is #30 taper the smallest industrial one or does exist something like #20 ???

I took appart one cooked off 85k rpm ATC spindle, german made - it had very tiny taper (size like er11 collet) ultra miniature pullstud and drawbar mechanism - impossible to replicate, and for too tiny endmills. I need up to 12mm. Im making small parts from 7075, my machine runs 12 hours per day, 6 days in week, every day most of all use 1/8" endmills, then bit biggers up to 6mm, Only my fly-cutter has 7mm shank. Spindle runs up to 45k but most of all 30k RPM, use coolant naturally ;-)
When trying to find something about tapers from Google ... its maddening - every trademark has own style,DIN, ISO or something else ...
I saw in youtube someone built his own small size BT style taper/spindle and ATC - was nice but Im not sure about precision when all this stuff is grinded in local workshop - at least myself I dont have good choices for grindings when question is about 0.000 angles :-(
Regards,
Herbert

[Jason3]

Hi Herbert,

How about ISO20? I 'borrowed' this pic from www.maritool.com - very nice products, they'll look after you. ISO20 is about 1" long in the taper I think.

Will you show us your spindle once you've built it?

Best regards,

Jason

[Herbertkabi]

Yes, thank you! Will buy one as prompt as possible. They accept PayPal?
We have EUR 150 tax-free limit - so I need to calculate what to buy to not to pay stupid customs ... stupid because takes huge lot of time



Hereby some wonder finds:
http://www.cnczone.com/forums/showth...threadid=76317
03-22-2009, 07:56 PM BobWarfield speaks that CAT, BT, NMTB = 16 degrees 35 minutes 40 seconds,
But ISO 30 and ISO 40 taper angle is 8° 17' 50 "
http://www.schaublin.ch/catalogues/PO053-060.pdf
as well as ISO 20 and ISO 25 taper angle is 8° 17' 50 "
http://www.schaublin.ch/catalogues/PO044-050.pdf

Does it means that ISO taper angle does not fit with BT/CAT/SK ?????????????????????

8° 17' 50 " = 8.2972222

Regards,
Herbert

P.S.
Good and useful pdf files, very seldom so perfect draws
http://www.schaublin.ch/e/catalogue_po.htm

[H.O]

Hi,
As far as I know all size 30, 40 etc holders has the same taper (7:24). If you look at the numbers you quoted (8° 17' 50" and 16° 35' 40") the second one is exactly two times bigger than the first. So it's probably just a matter of how the drawing was made. The first one is the angle between the center-line of the tool and the taper while the second number is the angle between two "sides" of the taper - it's still the same angle.

For my kneemill, which has a size 40 DIN2080 spindle I regularly, buy DIN69871 holders and then fit an adapter instead of a pullstud - works perfect.

And to answer you question about my gripper, the OD is 19mm, ID is 11.5 and was designed to fit 45° pullstuds. (There are A LOT of different types of pullstuds available too.....)

/Henrik.

[Herbertkabi]

Thanks, Hendrik,
When BT30 ball-gripper ID is 19mm then I can make it easily - just boring from two sides.
cheers,
herbert

[Jason3]

Herbert, my apologies - it seems ISO20 has a longer taper than I thought, sorry for the wrong information. I hope it will still work for you. Those are great drawings, nice to see full detail for the spindle bore and gripper as well! Yes, Maritool does accept paypal.

Henrik, would there be any chance of changing your ball type gripper for the split 'finger' type? I just wondered whether that might be easier to get it to pull the tool holder up evenly with that type perhaps.

What do you guys think of the possibility of making our own tool holders by rough turning, then hardening, then finishing by hard turning (rather than grinding)? I know they're usually made from alloy steel, hardened to about 54rc, but don't know exactly what grade steel is best.

I guess having a spindle to put the tool holders in is the first step

Best regards,

Jason

[Herbertkabi]

Herbert, my apologies - it seems ISO20 has a longer taper than I thought, sorry for the wrong information. I hope it will still work for you. Those are great drawings, nice to see full detail for the spindle bore and gripper as well! Yes, Maritool does accept paypal.

Henrik, would there be any chance of changing your ball type gripper for the split 'finger' type? I just wondered whether that might be easier to get it to pull the tool holder up evenly with that type perhaps.

What do you guys think of the possibility of making our own tool holders by rough turning, then hardening, then finishing by hard turning (rather than grinding)? I know they're usually made from alloy steel, hardened to about 54rc, but don't know exactly what grade steel is best.

I guess having a spindle to put the tool holders in is the first step

Best regards,

Jason

Yeah - ISO 20 I already ordered, now the main question is how I can make spindle for. I can do a lot of different things, 100% autodidact like I am, but 0.0000 precision angles - oh dear! - I dont like it but now is time to go to some top specialist, hat in hands, humbly stooped
At first I will make some working models to see how sure this ball-gripper works.
There is few problems with Hendrik´s Gripper replica - normally every toolchanging includes a short but intensive blowing with pressured air to keep taper clean - I try to do it via hollow drawbar, but my ISO 20 drawbar has only 6mm diameter ...
Second problem is I need ISO 20 HAUSER Retention knobs (art. 89-12808 page Po 50) ... but those wont fit with ISO 20 toolholder thread ...
perhaps Retention knobs could be self made ???
... and so on ... and so on ...
and finally Im starting like you to think about to make all this stuf myself (or ordered from able workshop).
Today again I saw one video wheres tiny x-taper toolholders was made as one piece with retention knobs and spindle was just hollow shaft ER20 ... so the taper angle was ER20
... on the video it works well - how in real life? - who knows ...

Cheers,
Herbert

[H.O]

Hi Jason,
I went for the ball type gripper because I thought it would be much simpler to make. I don't really know how I would go about making a finger type gripper but I don't see any reason one couldn't be fitted instead of the ball type one.

I'm pretty sure that the actual problem on my spindle is that the deep narrow bore where the tube for the drawbar and gripper is mounted isn't perfectly straight down the spindle shaft (drilled and reamed). Thus the gripper isn't 100% axial with the pullstud so it presses the holder to one side. The runout is dramatically less when I only put three balls instead of four in the gripper - I've thought about using it that way but I'm not sure....

Regarding making your own toolholders.....Everything is possible but is it worth it? I mean, $50 for a BT30 end-mill holder and $75 for an ER16 collet chuck from Mari-tool - and that's good quallity tools (or so I'm told). You can get size 30 holders on EBAY for half that price and they are probably better than what at least I'm able to churn out. But, then again, anything is possible and if you have the tools for the job why not give it a try.

/Henrik.

[Jason3]

Herbert, the modified ER20 collet chuck is an interesting idea. That might be able to be easily made without any precision tools perhaps. Have you a motor in mind for your ISO20 spindle - would it be direct drive, or belt driven? What is the target speed?

I'm curious how the tool holder is removed from the taper on a normal VMC ATC setup. The BT30 holders on my mill certainly don't drop out by themselves, they always need a thump on the drawbar to dislodge them. Assuming this is normal, could the gripper driven by the air ram have enough travel to also knock the holder out of the taper, or would this be impractical with a belleville washer setup?

Henrik, you raise a good point asking whether it is worth making tool holders. I have some Maritool products including a few BT30 holders and they're very nice indeed, and the cost although not insignificant, would not be ongoing. Re-thinking, perfecting the spindle itself should perhaps come first.

With your spindle, how about taking the pull stud out and trying it with a normal threaded drawbar? That might at least let you determine for sure that is where the problem lies, and might let you use your spindle... (Edit - I take that back, I see you did try that already!)

Best regards,

Jason

[H.O]

Hi Jason,
Yes, when using a threaded rod as a drawbar the runout is very low so the problem, for sure, is with the gripper. Mine is designed so that the gripper knocks the top of the pullstud to push the holder out of the taper.

It was a bit tricky to come up with the right number of belleville washers giving large enough travel yet provide enough force. In theory I have 3000N when the holder is seated and it takes 4500N to compress the stack of washers enough for the gripper to completely let go of the pullstud. The required stroke for this is ~6mm and the distance between the top of the pullstud and the "roof" of the gripper is around 4mm so it effectively pushes the holder out.

I'm still working on converting the kneemill I got and I need that to make the parts to fit this spindle to my smaller machine. If I ever get around to it....

/Henrik.