Milling in the lathe

I'm primarily an aircraft modeller, though I'm also interested in steam engines etc. My current build is a large scale Tiger Moth which I bought as a bit of a project - There are several undercarriage parts missing from the kit which are going to need slots of varying size milled in order to complete them.

I have an Emco Compact 8 lathe which has proven excellent for turning some of the parts I need, so I was considering fitting a vertical slide to it as a stopgap measure, just to allow me to get the Tiger Moth parts made. At this stage, I don't really want to pay out for a 'proper' milling machine, though that may happen in the fullness of time.

My real question is what are the limitations on milling in the lathe? The biggest 'problem' I can see is that of controlling depth of cut when the saddle only has the apron handwheel to move it. Perhaps anyone using a vertical slide would care to comment?

Gordon

Hi Gordon,

A standard vertical slide will only move up and down. Your best option is to lock the saddle in position and use the tool slide. It should be fitted with a micrometer adjustment on the dial which will allow you to accurately set the depth of cut.

Paul

There should be a small stub of the lead screw poking out the right hand side of the leadscrew support at the tailstock end of the lathe. You should be able to turn up a simple disc that can fit over this retained by a grub screw to act as a handwheel and put some basic graduations around the rim depending on if you have a metric (most likely) or imperial lead screw.

Then all you need to do is engage the half nuts and manually turn the leadscrew as your fine feed.

I had the earlier geared head version teh Emcomat8.6 which actually came with a handwheel fitted. Managed to do all the milling for the traction engine in my avitar with that and a Myford vertical slide fitted to the cross slide

Just out of interest, Jason. How long have you been doing model engineering? Theres so much stuff you know and have done.

Michael W

Got a Unimat 3 when I was 15 so that makes it 35yrs if you don't include a bit of plastic and RC before that. I'm not in the engineering trade either, just a hobby.

Paul - I take it by 'tool slide' that you mean compound slide? If so, that gets removed in order to permit the vertical slide to be fitted.

Jason - I guess that fitting a simple dial to the end of the leadscrew is a possibility - will investigate further.

I was also think that fitting a simple, single axis, DRO to the lathe carriage would work, though I'm not sure about how it might be fitted.

Yes you do get a bit of backlash which needs to be allowed for. If you are only measuring small amounts which for depth of cut is likely then a simple plunger type dial gauge is often easier to fit when and where needed.

pic of a 8.6 with its handwheel from lathes.co.uk

You may be able to rig up a temporary arrangement witha digital caliper clamped to the carriage and the tailstock.

If you're into electronics you could try this**LINK**

If I wasn't so modest (developed by self and Paul Middlehurst) I'd say it was just the thing!

I found milling on a mini-lathe to be very limited in comparison to a real mill.

The size of the part that can be milled is reduced because what can be mounted is constrained by the dimensions of the slides. Likewise cut lengths are limited by how far the slides can travel - not far.

Holding the work firmly enough in the limited space can be a challenge. And if the tool is held by a chuck it tends to unscrew into the work - not good.

With all that sorted, I found milling on a lathe needed extra skill and patience because the set-up isn't particularly stiff. I was only successful when taking very light cuts. I would probably have done better with more practice.

In conclusion, milling with a vertical slide on a small lathe was hard going for this beginner. Although useful up to a point, the limitations confirmed that - for me - a real mill was needed. As always much depends on who you are and what you're doing. Many people do great work with vertical slides.

Dave

Thanks, Duncan [and Paul]

That looks very useful !!

... and easy

MichaelG.

A better option might be an angle plate with the compound slide fitted to it. If a lathe doesn't have a T slotted cross slide the width that can be milled is usually seriously reduced. Ideally the gross slide needs to be in the middle of it's max travel and the vertical slide centred on the lathes centre line. If fixings are limited an angle plate might be a suitable size to position it correctly. One the other hand they are easy to mount on a piece of plate and offset that way. It would also be best to have fixings that don't allow the slide to twist under cutting loads. T slotted cross slides help a lot with that aspect.

It also helps if the slides vertical travel is centred around the lathes centre height.

A lathe face plate can be used for some "milling" operations. 4 jaw chuck too. Things can be clamped to a face plate or if the don't cause problems on the finished item pulled back onto it with screws from the back or even a draw bar through the spindle. I've done that a few times when there isn't a chuck big enough. The draw bar needs to run pretty accurately down the centre of the spindle other wise parts might work loose. I didn't bother but it's best to make a sleeve to fit both the spindle and the draw bar.

The only problem with all really is that lathes are usually designed to face a bit of a dish. Not much of one and on small parts it probably wont matter. If some one was working on a rotary table casting some lapping might be a good idea. It complicates things when blocks are turned up too as right angles need to be clocked up to suite - it is possible to clamp an angle plate onto a face plate to do that sort of thing but do add weights to balance things out. There are some about that have a radiused end on one side to help with that. If bought I would be inclined to check that it really is a square angle plate.

John

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The parts that will need milling are not very large, so I think the range of movements I'll be able to get on the various slides will be more than enough. Here's a pic of the parts which need some milling done on them - the aluminium leg ends are sized to fit into a 1/2 inch brass tube. Milling cutters will be held in my ER32 collet chuck. There's nothing very heavy duty involved either, so I think I'm going to obtain a vertical slide and give it a go. I'll look into buying a milling machine at a later date when I have a bit more cash to spare.

Duncan - An interesting project - It might just fit the bill if I can find the parts at reasonable cost.

Thanks for the help and advice!

Edited By Gordon Tarling 1 on 12/09/2016 17:27:43

If you have a quick change tool post bits that size could be done in that which would give basic vertical adjustment then the otherf two axis via the lathe.

A micrometer saddle stop is a useful aid, not only for this operation. Often the adjustment you want to make with the saddle is "two thou more" rather than a specific position or length and the micrometer is good for this. However there is a cheaper way for a bit of temporary work. Make some kind of fixed stop, a clamp or whatever and interpose a feeler gauge with all the leaves between it and the saddle. When you decide you want 5 thou more depth of cut adjust the feelers and reset.