Milling in lathe

Ever since I was nine years old I have have been intrigued by Curly's writings.

And all I know came from his instuctions.

In early days he did not own a milling machine and his directions for coupling rods and other tasks needing milling were carried out on the lathe using an end-mill and vertical slide.

He said nothing about drawbars to stop the end-mill from being drawn out and I have not yet found any complaints in those days (M.E. of 1930's) about this happening.

Today, however, we must use collets and drawbars if we pick up an endmill.

So, why?

What's the difference between holding an endmill in a chuck on the lathe and likewise on the mill?

And, yes, I have graduated to a large collection of endmills and the necessary collets and drawbars to retain them.

But I still have my vertical slide (now unused and sitting in it's box) and often think of the days when I first tried milling coupling rods in the lathe.

Many thanks everyone.

richard2.

Chuck gripping geometry. Lathe chuck grips directly sideways with no endwise force derivation so the end mill stays put.

Drill chucks draw the jaws down an inclined plane to derive the gripping force. Endwise push as when drilling increases grip so long as the drill doesn't slip. Endwise pull as can occur in milling reduces grip by moving end mill and gripping jaws out up the inclined plane until clearances are taken up. Grip is reduced which may be enough for the end mill to come loose. When cutting you have a combination of sideways vibrations and endwise push'n pulls repeating two or four times as fast as the spindle is turning. For maybe minutes at a time. No wonder the thing tends to shake loose.

Theoretically collets could have same sort of problem but the gripping area is much larger, clearances in the drawbar thread much smaller and tightening forces from the drawbar higher so generally tends not to happen. Can be a problem with small collets on small machines tho'. Especially with hand tightened drawbars. My old BCA was a forever pulling out cutters if normal cuts were attempted.

If screwed shank cutters in Clarkson et al holders try to slip they screw themselves outwards pushing the collet harder against the end cap increasing grip until slipping stops.

Clive.

As Clive says.

But also a vertical slide on a lathe is a flimsy affair that doesn't really allow more than light milling cuts. It will do the job but you have to be gentle. In comparison a milling machine exerts far more force and a firm grip on the cutter becomes vital.

Dave

Carbide cutters would have been unknown and HSS may have been too expensive. So it's possible that the cutters were carbon steel with softer shanks, like drill bits. So the chuck would have gripped a bit more than on modern HSS and carbide cutters. Plus of course the teeny cuts already elucidated.

Andrew

The chuck not to use is a Jacobs chuck with a MT arbor, and probably a Jacobs Taper into the chuck it's self, this set up is not designed for a side load as in milling, and will in a very short time fall out of it's taper. a lathe chuck is fixed to the mandrill in a positive way, so that's no problem,you just have to ensure the cutter does not move in or out, and with the light cutting done on a lathe vertical slide this should be no worry.

Ian S C

Many thanks everyone.

Now I know the why and wherefore.

An aside - I am awaiting delivery of a new Warco VMC VARIO mill.

Anyone have one and could comment?

Many thanks

Richard 2

I too have a Warco VMC, older than the Vario. A very good machine not as sturdy as the Bridgports at work but quite sufficient in the home workshop. I looked carefully at chuck options and chose the R8 version which I have never regretted. This version accepts screw-in , Clarkson type, cutters which never slip or tilt and are as good as any industrial chucking arrangement.

Jerry

I would like to add a couple of observations about LBSC's writing.

It was a very sparse writing style in comparison to most modern ME writers. He never/rarely mentioned problems, assuming the reader was competent to anticipate, avoid or work around them. A great deal was left for the reader to work out for themselves. I have a TEE reprint of the articles describing the 'Rainhill' build. 14 pages covering the boiler, chassis, cylinders, wheels, reversing gear and tender. That is not a great deal of description by modern standards. No one part is adequately detailed by modern engineering standards, either, but there is enough info for anyone competent to make the loco & get it running.

The other side of the sparsity of his writing is the confidence he instilled. As problems are not mentioned, they cannot possibly exist. So, with the blithe confidence of the truly ignorant, either you fall into every bear pit there is, or you sail through and nothing goes wrong.

All-in-all I enjoy reading his work, but would rather make a Greenly design. Greenly was a real engineer & has all the explanations at his fingertips - he knew his stuff to a depth that feels lacking with Curly. However, Greenly sometimes lost sight of the fact he was making a model & ifull size practice is not necessarily transferrable to a model and his writings lacked the self-confident 'bounce' of LBSC's.

Regards,

Richard

I have no problem with end mill cutters moving when held in my 75-year-old three-jaw lathe chuck. I regularly use it for cutters ranging from 6mm to 20mm diameter and milling up to 1" thick steel plate.

I have more problem with the flimsy Myford double-swivel vertical slide moving under heavy cuts. Jobs bolted straight to the cross slide table or a solid angle plate may be cut with gay abandon.

It is very much a "make do" situation though. I'm sure there is a small milling machine in my future, just can't quite see where the funds come from at the moment though!

It perhaps should be noted that 'Curly' did temd to make loco's that were on the smaller end of the size range and that in consequence the cutters he would have been using would have been of correspondingly small diameter. So small cuts, high speeds, slow feed and small cutters would all have reduced the issues faced. As for collets, on a Myford he would certainly have had the availability of spindle nose collets which would have been as secure as gripping an end mill in a modern ER collet on a vertical mill with a fitted drawbar.

In fact for Myford style collets, considering the fact that the lathe spindle is effectively the main part of the collet fixture with a collet closing nut on the spindle nose probably more so.

regards Martin

Fifty years ago it was common to use end mills with a taper shank ; I still have some with various shapes such as gear, tee slot and angle cutters with a Browne & Sharpe taper for which I made a No.2 Morse to No.4 B&S sleeve. I seem to recall seeing Morse taper cutters too. Colin

In my 20s I got a fair amount of experience milling on Bridgeports and a biggish Varnamo vertical (which I much liked), and I still use a Bridgeport copy in the shop I work in as a volunteer.

But all my hobby milling work is done on a Warco WM250V lathe with a Myford double-swivel vertical slide. The Warco crosslide is wider and therefore a good deal more rigid than the Myford Speed 10 I used to have, so quite a range of milling ops are possible with this combination. Most of the above writers' comments are very valid within context - you do have to learn not to be greedy with your cuts, you do have to watch for the cutter moving in a 3-jaw, and it is a make-do solution. But that's what engineers are supposed to do - find a way to do what you want with what you got!

So far, I still dunno if my wanting a dedicated miller will ever be strong enough to justify finding the extra space for it, even if the funds are forthcoming.

Edited By Mick Burmeister 1 on 28/06/2017 11:13:25

I did my first milling in the lathe ( an old Edgar) 45 years ago with the milling cutter held in the three jaw chuck and a bit of brass shim between the cutter and the jaws. No problem with the cutter pulling out.

Russell