More collet and milling tools confusion.

I need to be able to mill the occasional slot and rebate in (as far as I can predict) aluminium. The sort of jobs will be appropriate for a Super Mini Lathe.

I am looking all over - including my Metal Workes's Data Book and this Forum and the longer I look, the more information I am getting - on a divergent path at the moment. I can't decide which way to go.

If I only need a small range of end mills then is there any reason not to buy an MT3 direct collet of a particular size and then use only end mills that will fit in that? Is the advantage of an ER system just that it is easy to swap tools? eBay and other places are just bombarding me with options.

I am further confused by the discussions about tapping the drawbar to release the collet. If it is a real cause for concern then how come there is not (apparently) a system on offer which would include a draw bar and release mechanism? Engineers have been extracting tools and collets for hundreds of years. What could have changed?

If that is all you are doing then a collet in te hspindle will do, just make sure you can get the carrage and therefore the work close enough as a small cutter may only sick out of the collet 10mm or so.

Hi Andrew

One disadvantage of using a MT collet in the spindle was highlighted a few days ago, sometimes the milling head prevents access to machine any recess on the job. Using a collet chuck reduces this access question in most cases and yes changing the collet/tool size can be achieved without removing the chuck from the spindle taper.

Emgee

Edited By Emgee on 08/10/2018 13:13:43

The need to tap a collet draw bar to remove a cutter etc is a known action on many machines evan an R8 on a Bridgeport mill which releases easier than Morse taper is not necessary a problem unless you need to hammer heavily. I would use an ER collet system as it gives you more reach and cutter holding closer to support of the ways and spindle, better reach.

David

The other option if you need a bit more reach and like to see what you are doing is to use a "weldon" type holder which are quite reasonably priced, these are R8 ones but you can also get MT variety. The only downside is they don't work well with FC-3 Cutters unless you grind a second flat further up the shank.

Edited By JasonB on 08/10/2018 13:40:05

You might find that a cutter held in an MT3 collet won't reach your workpiece as the carriage on a mini lathe cannot be brought all the way toward the chuck due to the location of the motor. If so, an ER collet chuck would give slightly more reach (and let you use the collets for turning as well).

Brian

I'm not surprised you're a bit confused! What you're planning is a little off the beaten track.

Firstly, although milling on a mini-lathe is certainly possible, it's far from ideal. My experience was quite frustrating - the tool-post has to be unbolted and replaced by a milling vice. Then work has to be clamped on a smallish milling vice after which the length of cut is restricted by the distance the lathes saddle can move front to back. Also the rate at which metal can be removed is constrained by the lathes lack of rigidity.

One awkward decision is how best to hold the milling cutter. I simply used the 3-jaw chuck. Normally a 3-jaw isn't a good way to hold a milling cutter, but because milling is already constrained by the limitations of  the lathe, it worked well enough in practice. An advantage is any size of cutter can be used.

ER Collets provide a much better grip on the milling cutter, and also reduce run-out. So, on a mini-lathe you could unbolt the 3-jaw chuck and plug an ER32 chuck direct into the spindle. Unfortunately, because the taper is designed for quick-release, there's a risk the chuck will come loose unless nipped in place with a drawbar. You can get ER32 chucks that bolt firmly on to the lathe - these usually require you to turn a backplate to fit them, but don't need a drawbar.

The main problem with collets of any type is that you need one for each size of cutter, and the whole set up soon gets expensive. I tried an MT shanked milling cutter holder - it works fine, but in my case, didn't suit because of the range of milling I wanted to do. I used it without a drawbar and found removing it problematic. (Done with a hammer and rod from the other end of the spindle.) Without a drawbar the stupid things either come loose or stick solid.

Tapers, as you say, were invented to speed up tool changes. The simplest way of holding a taper secure and releasing it is a screw-in drawbar. Plenty of other systems are available at extra cost, but the drawbar has stood the test of time and it's cheap.

Quite a few people dislike the idea of hitting a drawbar to unstick the taper in case it damages a bearing. Actually, provided the drawbar wasn't overtightened, it's not necessary to pound on it. A sharp tap is sufficient and I don't think there's any chance of damaging a bearing. The concern might have a basis of fact in that some chaps believe religiously that anything done up with a spanner should be good and tight, ideally finishing off by hammering on an extender. Tapers only need to be nipped. If overtightened, they do have to be hit hard, and that could cause damage.

For what it's worth, I abandoned milling on my mini-lathe rather quickly. Fortunately I had the money and space for a milling machine. However, with care, practice and a delicate touch it's certainly possible to mill of a mini-lathe. Try holding the milling cutters in the 3-jaw, take gentle cuts, and see how you get on. I think you'll find that you can make it work and that holding the cutter is the least of your problems.

I'll be interested in what others say. I'm no expert because I took the cowards way out!

Dave

Edited By SillyOldDuffer on 08/10/2018 14:17:23

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The essence of the problem is that the Morse taper is rather too shallow for the job: It was designed to be 'self-holding' in a drilling-type situation [longitudinal thrust], not for milling, and not for split collets.

If used for milling, it is wise to use a drawbar because the side-loads can loosen the taper.

BUT ... it is all-too-easy to over tighten the drawbar and [because of the shallow slope] jam the Morse taper in its socket : whereupon the thumping begins !!

The steeper tapers are much better suited to the milling situation, and as split collets.

MichaelG.

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P.S. Myford's special collets were an attempt to improve the situation.

Ideally, if the budget, and space will permit, it would be better to use a milling machine. I tried a Rodney milling attachment on my Myford ML7 and did not like what it was doing to the lathe, so bought a Mill/Drill. (All that I had space for, and a major part of the budget). Still have it, and use it.

Would really like to have a machine with a dovetail column, but cannot be bothered with the hassle of selling the Warco Economy, It does the job, although a little less convenient than a current machine; but no real major problem,

I am pursuing a hobby, not piecework rates.

So, if possible, buy a Milling machine, bearing in mind the likelihood of wanting to do larger work in the future.

Afterthought.  Although I have four MT collets, 99% of the time use ER 25 collets in both Mill and Lathe.

Howard

Edited By Howard Lewis on 08/10/2018 14:57:52

If you want to use milling cutters on your Lathe then this type of collet chuck may be better.

**LINK**

It doesn’t use a draw bar and you can also use it for holding stock as you can pass material through the head stock.

You could use finger collets in the headstock but it’s not so convenient having to unscrew the draw bar and knock the collet out.

Historically they used to use collet chucks like the Clarkson Autolock designed specifically to hold milling cutters in a mill but they have lost favour. You can still buy them though, plenty on the second hand market. Google Clarkson Autolock chuck for more info.

The only limit on what you can mill on a mini-lathe is what you can fit on it:

Fly cutting...

Roughing out T-slot:

Roughing out dovetail:

Setup for t-slots:

And the end result:

Any questions, Dave?

Not that I know much about it and I am probably missing something but if the work piece is aluminium couldnt the cutters be held in the lathes 3 jaw.

Cross posts, Neils pictures beat me to it.

Edited By Ron Laden on 08/10/2018 19:19:15

Ron, there is said to be a risk of the cutter pulling out of the 3-jaw no matter what is being cut particularly if a deep cut is taken. But I made that Minnie in my Avitar on the lathe and all the milling cutters were held in the 3-jaw without incident. Maybe I was just lucky?

.

Yes, but ... unless you have an extraordinarily good 3-jaw, they will perform as single-flute cutters of larger than specified diameter.

MichaelG.

Yes, in this picture the dovetail block is clamped directly across the tool-post.

My question is: why don't I think of tricks like that?

The late great John Stevenson often suggested underperforming machinists should take up knitting. Now where did I leave my needles...

Dave

Maybe not luck Jason, more likely the fact that that you are obviously a very skilled machinist. I find it amazing that you produced the Minnie on a lathe, I doubt that luck had very much to do with it.

Thanks for yet another useful list of comments. The lack of reach for a basic 3MT collet is something I hadn't considered (well you don't do you?) so something a but longer would be good.

A flange fitting system could also give me problems, I think because I would also need a backing plate

I have already found my new four jaw chuck very good. Getting it well centred is not quick but has given me an encouragingly small runout and, with a bit of ingenuity with the four jaws in odd positions, I managed to put a dovetail (male) on a 10mm, 30mm square piece of aluminium with it. The carriage lock I made, plus other measures that you guys suggested seem to have stopped the chattering and singing on that exercise. My point here is that it could be worth trying to use a cutter in that chuck, at least to try things out. I am waiting for one of the milling slides that Warco have on back order. The spec of that seems better than others that are available and it looks the same basically as one that's on offer from India.

Some great pictures above - I'm a great believer in 'unofficial techniques' and I certainly need some more odd studding and bolts for me to get inventive with. I basically got into all this in the hopes of producing some affordable hardware for my Astronomy / Astrophotography. The simplest stuff is not cheap and I have not been over impressed with the basic Engineering of many parts. It seems to be way behind the optics, which can be stunning.

Andrew, I have been thinking of getting a collet chuck for my Amadeal CJ18A lathe, so have been looking at different suppliers to see what is available.

I think that this one should fit directly to your lathe:

https://www.warco.co.uk/lathe-collet-chucks/256-er-25-lathe-collet-chuck.html

Similar ones seem to be available from all the usual suppliers in sets with collets.

One advantage of using the MT3 collets that hasn't been mentioned ( or I haven't noticed it ) is the rigidity of the set-up due to the minimal overhang. I imagine the ER chuck bolted to the spindle flange would be as good, and I intend to get one some day, but if you're on a tight budget it is one more expense. MT collets are cheaply available, probably because few people use them

I suspect the affordability of ER collets and sets is due to the huge volume sold, not the other way around.

I suspect if there were problems with using ER for milling I would have used my Osborn Titanic II posilock more than two or three times, and maybe even got a set of collets for it ... (used so little I can't actually remember if the collet set I have is metric or imperials!)

I would always recommend the ER system for two reasons: First, it's much more compact than locking collets systems so the overhang and 'lost headroom' isn't enough to worry about and second the flexibility and affordability given by the collets having a working range, which makes them ideal for precision workholding as well as holding cutters.

Neil