Best choice of spindle taper?

[JST]

I have a small milling type spindle to make, for a specialty purpose. It will be taking end mills (in holders, most likely), and stub arbors to take saws and cutters of various types.

The open item at present is the spindle taper. There are a number of possible choices, each with positives and negatives. It is a definite advantage if the taper is self-releasing, like the NMTB tapers.

Due to space restrictions, it probably does not have room for anything as large as an MT3, or NMTB30 taper in the spindle end. I'd like to keep the spindle not much over 1" diameter, and it can't be very much more than 5" long. The MT3 is longer than desired, isn't self-releasing, and is too large in diameter, while the NMTB30 is already too large in diameter. R-8 is out as it is even bigger.

Digging in the Machinery's Handbook, I found NMTB10 and NMTB20 tapers. Of course, they are nearly perfect. Trouble is, nobody seems to ever have used them, and no holder or tooling of any sort is available in those sizes. Smallest is NMTB30, and even that size is limited in available tooling. No help there.

I could potentially use a 3C collet. But they aren't as stable as an end mill holder, and are no help on arbors at all.

Rolling my own seems to be the worst idea, followed closely by using a "standard" for which I would have to make all tooling, such as the NMTB10 or 20.

I keep coming back to the MT2 as the best of a bad lot. End mill holders, collets, and even arbors are available. But that taper is self-locking, and requires beating to get it out of the spindle. Not good, or at least not desirable.

Have I missed any viable standard tapers that might fit the bill?

 

[J Henricksen]

Have you considered making a taper and locknut for the ER series collets? ER25 might fit and they are compact.

 

[Limy Sami]

I'll 2nd that, for small / light machines it's the only way to go, had ER20 running in a home made EN24T spindle for 12+years with no trouble at all, my only regret is that I didn't make it ER25.

Take care. Sami.

 

[ztarum]

If you are making the MT2 spindle from scratch, why not make the drawbar captive. By that I mean that you should make it so when the drawbar is rotated counter clockwise it actually forces the collet out. My Deckel FP1 uses such a system with MT4 and it works pretty well.
No beating required.

An ER system native to the spindle would be a good idea too.

 

[Brian@VersaMil]

To take all the fun out of your project, have you ever thought of just buying a ready made Morse #2 Spindle, complete with a drawbar, that forces the tools out of the spindle.

VersaMil makes two versions of a #2 spindle, for both a milling head and right angle head. I even STOCK them, along with every #2 Morse taper toolholder you can imagine. www.versamil.com

I also stock 3# Morse, 30 NMTB, 40NMTB and 50 NMTB spindles, along with a variety of machine tool housing castings.

 

[Glenn Wegman]

Why not make a spindle to accept Royal quick change tooling. That way it would have a male end on it rather than female so the 1" diameter and 5" length would not be a problem.

Didn't I see a thread on here recently where someone made 50 pcs of quick change tool holders?

Glenn

 

[beckley23]

Look in some of the catalogs for straight shank collet holders. They should be available in DA, TG, ER etc.
Harry

 

[jkilroy]

I'd vote for giving Brian a call and buying one but if making one is part of the fun then how about a straight 3/4 hole with weldon style set screws like a endmill holder? You could use 3/4 straigh shank ER holders. You could also modify existing hardware pretty easily back to a 3/4 shank as well.

 

[JST]

It isn't the "fun" of it, but assuming that somewhere the other stuff is actually listed on the Versamil site (couldn't find any of it other than limited price list), I'd be over budget after a few arbors.....

As for spindles, maybe he has them. Couldn't find them, and yes, I have to ask, so no I can't afford it.

ER is a nice collet, but not over-nice as an arbor..... I assume the collet would hold the arbor to hold the cutter....

 

[matt_isserstedt]

What about something like a router collet? Straight shanks of 1/4" and 1/2" are very common.

I would say that's a very tight grip as the spindle speeds are at least an order of magnitude more than a mill.....but consequently the cutting loads might be smaller too since the feed-per-tooth is fairly small too.

Might even be able to salvage your spindle from a junked router (bad motor)...maybe a local tool repair shop might have one (???) and then just fit up the bearings.

 

[Brian@VersaMil]

My web site just has the LIST price of new machines and attachments. I have at least 200 #2 Morse taper toolholders. If you're interested in what a spindle would cost, give me a call.

Making a ONE off spindle for the average shop, is quite a bit of work. Every spindle I make, gets turned, heat treated and ground. I use a CNC lathe for turning the spindles, which even for a small run- two or three spindles, is fairly quick. I can just call up a program, use mostly the tools in my turret, and whip out the blanks. But I always run a batch of spindles, so heat treating doesn't kill me, and the grinding of the spindles can be done more than one at a time. But no matter how efficient I try and be, each spindle ends up with at least two hours or more in it, from start to finish. Larger 40 or fifty taper spindles are more like 10 to 12 hours each. However the fifty taper spindles can lose 75 pounds from start to finish.

If you wanted to just use your spindle for small endmills, I'd agree with the other posters on using a collet-but you did mention you want to use end mills and slitting saws and probably side mills. They certainly require more beef than a small collet. If I had my choice, I'd make it with an R-8 taper. Not too big, great availability of toolholders. I'm tempted to make a small milling head with one. But alas, it seems bigger than what you want.

 

[JST]

Yeah the R8 is bigger than the spindle!

The MT at least gives a collet option, as well as fairly available tooling.

But the self-ejecting idea is good. I can definitely see the MT2 with a reversible ejecting drawbar.

Due to the short spindle, flex of the drawbar when pushing would be minimal, even if it were thread sized for the whole length. Excellent idea, thank you.

Inquiring minds want to know...... Did ANY machine builder ever use the NMTB 10 or 20? They apparently went to the trouble to define them, you'd think they might have been wanted for something.

Maybe vertical heads..... anything that takes an MT2 would take the NMTB10, maybe the 20. Lots of heads take MT2

 

[jim rozen]

Well if it won't do R8, that leaves out my
suggestion: 5C collet!

Jim

 

[Thermo1]

My old Brown & Sharpe milling machine has a knock-out bar that came with the machine. It is a bar about 1/2" diameter, with a steel ball about 2" in diameter on one end. You put it in the spinde, whack it once or twice, and out comes the tool in the #10 B&S taper. Never had a problem removing a taper shank tool.

Thermo1

 

[Doozer]

Another vote for ER25 or larger. ER's are very nice.

--Doozer

 

[jim rozen]

" I can definitely see the MT2 with a reversible ejecting drawbar."

Oh. You should inspect a b'port M head
then. That's how they do it, the drawbar is
captive to a nut at the top of the spindle.
The nut has a coarse left hand thread to
attach it to the spindle. So basically
once you loosen the drawbar to remove the
tool from the MT2 collet in the spindle, you
just keep on loosening, and the drawbar turns
from a 'puller' into a 'pusher' and ejects
the collet out the bottom.

Jim

 

[JST]

Ah.... nice..... As you surmised, I do NOT have a B-port. Never ran one.

I really hate beating on a spindle. Even the knock-out bar (mine is a length of brass rod) bothers me if I have to bang it hard.... Bearings don't like that, although roller are more tolerant than ball bearings.

 

[cmiller231]

I believe Index mills had a self ejecting design . or at least so i was told . Don't know what model number though. Chris