Holding End Mill on small lathe

Hi,

I'm trying to work out whether I can make some small parts by milling on my small lathe. I am imagining holding an end mill, maybe 8mm to 12mm in diameter, in the headstock, and mounting the metal block to be machined on the cross slide. I can them move the workpiece on either horizontal axis using the slides. I will have to reply on making packing pieces of the required thicknesses to get the workpiece in the right place vertically.

My question is, how do I mount the end mill into the headstock? As far as I can see my headstock has an MT1 taper (at least, it is 11.1mm diameter at the wide end, which is too small for MT2). The options that I can see are to buy an end mill with an MT1 taper (but I can't find one), or to buy some kind of collet or collet holder that will fit into the MT1 taper.

This is assuming that holding the mill cutter in a chuck will be unsatisfactory.

What do you recommend?

Thanks - Rowan

All the pundits will tell you that you can't hold a milling cutter in a lathe chuck. You can if you're prepared to take very small cuts with small (say 1/4" diameter or less) cutters. The danger is always that the cutter will "walk out" of the chuck and dig into your nice job. I've often gone the small cutter in a drill chuck route, but always been prepared for disaster. I've seen cutters walk out of chucks - it was a 2" diameter slot drill and I'd nothing to hold it with except the lathe chuck. Horrible idea,despite taking the smallest cuts I could... I used a different idea completely, .

Alternatives for holding cutters is to make yourself a cutter holder; this can simply be a length of decent-sized steel bar with a grub screw to hold the cutter in the lathe chuck. You also need a flat that you've previously ground on the cutter for the grub screw to bear on. Not ideal.

Best solution is to get (say) an ER16 collet chuck. They are available with parallel shanks, which can be gripped in a 3-jaw. You will only be able to hold relatively small cutters with that, but if your lathe is only 1MT that's probably all it will cope with.

A cutter with a 1MT on one end should be axially restrained with a draw-bar to stop it coming out of engagement.

It also sounds as if you could do with a vertical slide for milling!

Dont try to hold endmills in a chuck, they are quite likely to slide in/out. An ER collet works, and is what I have been using so far, or there are end mill holders for standard size endmills.

Easiest way to manage the y axis is with a vertical slide attachment.

What is the lathe?

Cheers, Colin

Three jaw chuck and put paper round the endmill to help grip. Copper foil is good but you are less likely to have any.

Why is it better to make a holder or buy a collet chuck and mount this in the 3-jaw chuck? I would have thought that the whole caboodle would be just as likely to work its way out of the chuck as the cutter on it's own would. It seems to me that I need to avoid using the chuck altogether, and use something that fits into the morse taper. This is presumably either an end mill with a Morse taper all as a single tool (are these available?), or a collet that fits directly into the Morse taper, like this:

or some kind of collet chuck with an MT1 taper on the end.

My lathe is a small Portass, probably made between the wars. I'm not sure exactly what model - it doesn't seem to have a plate on it.

I'd welcome any further advice on the best way of doing this. For example, does one need to do something to take up the backlash in the cross slide to prevent chattering?

Thanks - Rowan

FWIW obtain an ER collet chuck, and suitable collets.

Don't know of any 1 MT shank ER collet chucks, so you may need to buy an ER chuck with a plain shank, and then grip that in the lathe chuck. Which size of chuck, and collets, that you buy will depend on the size of cutters that you want to hold. ER11 will hold upto 7mm shank, ER16 up to 11mm shank,and ER20 upto 13 mm

DON'T fall prey to the temptation to holding a milling cutter in a Drill Chuck. The cutter may well "walk out" of the chuck, and you may damage the drill chuck.

HTH

Howard

I've been milling with endmills, slotdrills and boring bars (often used as flycutters) held in a 3-jaw for 20 years or more. If you tighten the chuck properly, they never pull out. It's much more important to lock the carriage to stop it getting dragged chuckwards if using spiral mills.

I'm using a Warco WM250V with a Myford swivel vertical slide for milling. I find an 8mm. carbide 4-flute endmill is particularly good - seems to retain sharp flute-lips forever. I've used it on mild and silver steel, brass, alli and titanium.

I think you'd be better with some sort of vertical slide to give you a proper third axis, but if you're reasonably careful and don't get too greedy I don't think there's any problem holding the mills in a decent 3-jaw.

The photo you show is a "finger collet" which would do the job fine, if you can get one with an MT1 shank. Aha! You can, the excellent Arc Eurotrade stock them here. Only however in metric sizes. Needs an M6 drawbar. Frankly if your lathe is small I wouldn't use over an 8mm cutter and probably 6 would be better.

The problem with holding endmills in the lathe chuck is that they are very hard, and will not deform slightly to take up any misalignment of the jaws. This means that if your chuck jaws are slightly "bell mouthed" due to wear the cutter can worm its way out of the chuck. Putting some soft material between the jaws and the shank would probably solve the problem, but you need to tighten the chuck very hard to make sure the material deforms enough.

If your taper was MT2 then you could buy an ER collet chuck to fit, which you would need to hold in with a drawbar. I haven't seen any of these with an MT2 shank though. You can get parallel shank ER chucks - see the Arc website for example - which you could hold in your 3 jaw. As it will have a longer shank of larger diameter than your cutter, probably it would be safe, also the shanks are softer and will deform a bit. Whether you want to go to this trouble

Milling cutters with Morse shanks are rare - morse shanks are really for drills and reamers.

You need to make sure that you feed into the cutter, so the cutting force pushes the work away from the cutter. If you do that the slide backlash should not be a problem. If the cutting force pulls the material into the cutter it will be a BIG problem. If you have space and the job isn't too big a vertical slide will make life easier - adjusting the vertical height of the cut by packing will be rather fraught!

You should buy a MT1 - ER 16 or 20 collet chuck - they are sold on ebay-UK and banggood according to my quick google. You will need to manufacture a drawbar - some threaded bar, nuts, and appropriate washers will do the job if you cant be bothered making it pretty!

Workholding should be done with a milling slide mounted on your cross slide - which will give you adjustment in both x and y - again available from the usual suspects.

A good finish will be achieved with a consistent feed rate - if your lathe doesn't have power cross-feed you can make an adapter for your little crossfeed windy thing and a variable speed battery powered screwdriver/drill to achieve consistency.

Take small light cuts, go slowly, and use lubricant.

Don''t be tempted to put the milling cutter in your 3 jaw or a drill chuck! If you don't know what you are doing you will likely screw up the workpiece or the endmill or both.

My experience of lathe milling was disappointing. It's not so bad I'd dismiss doing it out of hand, but it's pretty poo compared with a proper milling machine.

Holding the milling cutter in a 3-jaw lathe chuck will be the least of the problems encountered. Lathes aren't designed to deal with milling forces on the cross-slide, so the whole shebang lacks rigidity and lack of travel limits the size of job that can be tackled. And even with a proper milling slide, work-holding is cramped and awkward.

However, it can be done. In practice I didn't have a problem with cutters pulling out of the lathe 3-jaw, but that might be because lack of rigidity restricted my depth of cut so much that the chuck wasn't tested severely. An MT spindle mounted Jacobs chuck sort of worked, but I felt it lacked beef. Bad option compared with the lathe chuck.

I also bought a couple of 6 & 10mm MT milling tool holders to fit direct into the lathe spindle and made a drawbar out of studding. Less run-out than the 3 jaw, but otherwise lack of cross-slide rigidity meant the cut-rate couldn't be increased.

I experimented on a mini-lathe. Necessary to have the gibs extra tight. The same sized job would have been more successful on a heavier machine, but the bottom line is lathes aren't good at milling. But hey ho, any port in a storm!

Dave

Edited By SillyOldDuffer on 14/03/2020 18:09:53

Just got a small metric set from chester at a fiver a pop

The big problem with milling is stopping the cutter from gradually going walkies into the workpiece

That's the sort of thing I was thinking of buying. Have you used them yet? Any input on how well they worked, or things to be aware of? I will probably just buy the 8mm one for now, since I think I can do the job in hand just with an 8mm cutter.

Thanks - Rowan

I managed OK with them in either a drill chuck or lathe 3-jaw, made two Stuart engines and the Minnie in my avitar before I got a milling machine so OK if you take your time.

Finger collets like you illustrate or a backplate mounted ER16 collet chuck would be preferable as they will hold better and should have less run out.

Got to screw it up properly but I'm well pleased, I work my gear pretty hard

needs a 6mm drawbar, I use threaded bar from B+Q

Some mini lathes do not have a full depth morse taper in the headstock but if yours has I'd opt for a MT1 ER 25 as the range of collets is larger than ER 16. My Boxford has an ER40 on a back plate but it is a bigger lathe.

If your lathe is small enough to warrant an MT1 in the spindle, I would personally opt for an ER11 collet chuck with MT1 shank. Like this:

Link to ER11 chuck.

That way you can use cutters up to 7mm diameter without fear of overstressing the lathe. Anything bigger and you will be tempted to take deeper or more aggressive cuts which exceeds the equipment's capacity.

John

Edited for spelling!

Edited By John Hinkley on 14/03/2020 19:52:33

Consider getting the Workshop Practice Series book 'Milling in the Lathe' by Tubal Cain.

Neil

I did consider an MT1 collet chuck but it adds yet another weakness into the system in a high stress scenario on a hobby lathe

On the plus side, it's far more convenient and more flexible

Edited By Ady1 on 14/03/2020 22:05:15

Re finger collets - they have to be ‘bumped’ out to remove - unless you have/make a drawbar with forced extraction. Depending on the type/quality of the spindle bearings, they may not hold up too well if the collets need to be tightened in excessively and ‘bumped’ out often. I like tooling that can be extracted with wedges, rather than ‘bumping’ excessively hard.🙂

.

... an unfortunate side-effect of using the shallow-angle Morse Taper

MichaelG.