WM180 draw bar

Hi All.

I've made a simple draw bar to retain MT3 collets in my little Warco. The smack on the bar (with soft hammer) to eject the collet seems mechanically insensitive and can't be good for the headstock bearings.

Is knocking the collet out like this OK? I'm contemplating making a fancy draw bar, capable of ejecting the collet without a knock but it would be quite a lot of work if it's unnecessary.

All opinions welcome.

Cheers, Gareth

Its what I do on my Omnimill to release tapers from the quill, not that I change tooling that often. I always lock the quill and the smack with a plastic faced hammer is always good and hard - no tap tapping.

As it seems to be standard practice on a mill (in the absence of a posh actuated draw bar) are mill spindle bearing arrangements designed to take it?

I haven't looked but I'm fairly sure the WM180 has taper roller bearings which are probably well up to it and I'm worrying unnecessarily.

I suspect that compared to the hammering they get taking a substantial cut it's quite benign. If you are using finger collets, don't overtighten the drawbar and don't leave the collets tight when you've finished. I discovered long since that I get many fewer skinned knuckles if I take the cutter out before making a new setup!

It's only a small lathe so cuts are never that heavy but I do think you're right though. Good advice about not leaving the collet tight or cutter mounted. Just the sight of a gleaming end mill makes me picture the plastic seats in A&E department.

Think I'll stick with the hammer for now. If the bearings suffer, it wouldn't be a bad thing to renew them with less Chinesey replacements anyway.

Thanks.

FWIW, as Apprentices on big Cincinatti vertical mills, we used to hot bthe drawbat for INT40 and INT50 arbors with a 7 lb lead mallet.

But would not commend such aheavy mallet for hobby machines.

1. Don't overtightem Morse taper tooling (It is self gripping so doesn't need a lot of clamp load )

2. Don't clamp the quill, so that it can give alittle when knocking the end of the ndrawbar (Only slacken by a thgread or two, for the sake of the threads )

3 R8 tooling having a faster taper, will need less end load to break the taper than Morse Tapers.

If you are really worried by this either make up a self ejecting drawbar, of that is possible, or make up an extractor which locates on the top of the quill and only exerts force on the drawbar.

A M6 thread can exert quite enough force to eject most Morse Tapers, unless overtigytened. Evem then, when fully tightened, a light tap will usually breaknthen taper.

Howard

Typos again!

Edited By Howard Lewis on 24/03/2023 18:11:12

The top of the spindle has been modified on some MT type mills to retain the drawbar so that it pushes the tool out. Unfortunately it may have to be removed and turned in a lathe, and the splines allowing the quill to move restrict the size at the critical top. You could look inside the spindle for a step just above the Morse taper, but there will not be much compared to R8 spindles, I have made two of these self extracting.

Thanks for all the replies. I think I need to clarify - the WM180 is a lathe, not a mill.

Holding cutters or stock in tapered collets is very much a secondary mode of operation.

I know for sure that small lathes with ball-race spindle bearings can be damaged by smacking a draw bar. I think mine has taper rollers which are more able to take the knocks, but I still don't feel great about hitting it.

Lots of milling advice, but for a lathe, I would suggest the best advice might be to save up, get a mill and lose the vertical slide.

I rarely use a taper in my lathe spindle, but have twice the between-centres on mine. I’ve never used the vertical slide that came with mine.

But, yes, a soft mallet is about the only way to release the tape, unless a means of pushing it out is made up. I expect the collets require to be quite tight for use with endmills.

If I was starting out, I would buy an ER chuck - but that available space is always the issue with a tiny lathe.

Sorry about mistaking it for a mill. If there is any of the spindle sticking out of the left end of the headstock, you could turn up a split clamping collar that could be used with a drawbar. It would be easy to remove when not in use. I have an er collet plate which is used on the lathe as well as the collets which are made especially to fit in the spindle. They have steeper angle tapers and are easy to remove. The er plate shares the same collets that the mills use and is easier to use than your Morse tapers.

My lathe and mill both have a 3MT taper and it normally only requires a slight tap on the end of the drawbar to loosen the tool in the taper. If it is too tight, I use this tool that has opposing wedges.

Details can be found in the August, 2015 edition of MEW **LINK**

I use a couple of wedges (home made) to wedge out the taper, if more than a reasonable tap with a soft mallet does not remove the MT. I actually have a couple of pairs, for space differences between tools and spindle. Never yet failed me, on my 2MT mills.

One important point re tapers is that of not fitting a ‘colder’ taper into a ‘warmer’ socket. After the usual gripping of the joint it will then be ‘shrink-fitted’, as well, as the temperatures equilibrate. That tiny effect will fix the shaft in the socket sufficiently to make extraction more difficult. A very cold taper into a well-warmed machine is a definite recipe for trouble.

At present, I only have a set of MT3 collets to go in the spindle (and a dead centre). I don't have a MT3-to-ER collet chuck or anything similar. So, if it was really stuck, I couldn't use wedges to aid extraction.

I may buy (or more likely make) a flanged ER chuck which seems the most versatile for holding cutters and/or longer pieces of stock. Downside is the runout that is often introduced by collet, chuck or clamp nut. At present there is zero runout (that I can measure) with a cutter in a morse collet.

I'd never considered cold collet vs warm spindle - that's a great tip.

I'll carry on with a plastic hammer for now but do have a decent idea for a sort-of-self-extracting draw bar. There is no "spare" spindle at the rear so I'll have to replace one of the castellated locknuts with an internally and externally threaded collar.

Thanks again to all above.