Lots of problems milling in a lathe that are overcome by taking it gently, perhaps very gently.

The main limitation of milling on my mini-lathe was insufficient rigidity in the top-slide rather than motor power. That is anything other than a light cut caused the slide and work to move, plus there's a risk of an end-mill shifting in the chuck when the going gets heavy.

I'd try a fly cutter provided there's enough travel to accommodate it. Lack of travel is the other big problem with lathe milling; smallish jobs only.

Please tell us how you get on. Before milling machines chaps did it all the time. It's a real test of ingenuity and technique. To my shame I wimped out and bought a milling machine.

Dave

Edit: I see John Haine posted while I was typing.   Yeah, wot he said!

Edited By SillyOldDuffer on 09/07/2017 12:46:44

It's probably the same reason why many would find it easier to drill a smaller hole before drilling a much larger hole. There's simply less work for it to do.

Michael W

Yes indeed but the booby trap is that a lathe cross-slide isn't designed to deal with milling forces. Normally the cross-side pushes a single-point tool against the work. The force on the tool is pretty much in one direction and the cross-slide is engineered to deal with it. Also, because the force is unidirectional, any slack and backlash in the system are taken up and held as the cut is applied. It's a stable arrangement that works well.

Milling applies dramatically different forces and it doesn't help that a milling cutter has much bigger cutting edges than a lathe tool. Because the tool is spinning, so is the direction of the cut. The cross-slide is forced down, right, up and left repeatedly. It is pushed hard in directions the lathe designer never took seriously. And any slack in the screws and gibs will allow enough movement to cause trouble.

The best way to get a feel for what works and what doesn't on your lathe is to try it. It's very educational!

Dave

I just used a 3-jaw.

There is really no fundamental difference in the construction of the slides between a lathe and a mill in my experience. The biggest differences appear when you get to the headstock in terms of collets and drawbars rather than a chuck, and the arrangement and movement of the slides is obviously different.

If anything, a modern lathe relying on a polyform bedway slide is more rigidly constructed than a simple vee groove simply to counteract the twisting motion Imposed on the saddle during rack feed. Probably one of the main reasons why my Clarke never had a rack and pinion feed (simply directly bolted to the feednut and handle.

(You may have seen the post on my failed experiment with a rack/pinion feed, due to the reason outlined above, though I think I may have found a clever workaround, it'll work this time I think!) 

As far as I know my mill uses vee groove slides, one thing I would agree is that with a mill it's a lot heftier than the cross slide though, as the travel tends to be far shorter on a lathe. In theory with a sensible set up there is no reason why he couldn't do milling on a lathe, I have milled a cast iron piece on the lathe before and found I could take quite a cut with it.  Just make sure those bolts are done up tight on the vise, Nigel! 

Michael W

Edited By Michael-w on 09/07/2017 21:04:15

If your trimming that lump off your vise as shown in the other thread then bandsawing or even hacksawing off the majority of what needs to be removed first will make the job far faster and easier on the machine. With a flycutter in the lathe you will or should see the tool cutting on the backside of the cut once you get across the job far enough but it will be by a very small amount. That's quite normal and doesn't indicate a misalignment of the headstock. It's mostly caused by the cutter flexing and not taking 100% of the cut that was dialed in.

Before the influx of the much cheaper offshore benchtop mills started and with tough times for many in the UK even up into the 1960's due to the war few had the luxury of having any sort of a mill in a home shop. The very small BCA jig borers sold for almost 4 times what a then brand new Myford Super 7 was selling for. The old Model Engineer magazines show some extremely complex milling tasks all done on the only machine tool many had in the shop, there lathe. For anyone trying to do the same today I can't recommend the Workshop Practice book Milling in the Lathe highly enough.Even having a vertical mill it can still teach a lot. I have a Bridgeport clone yet still bought a large Palmgren milling attachment for the lathe. It's rare, but some jobs such as milling, drilling, boring or tapping the ends of long bars can still be done easier while using that milling attachment and the lathes headstock much like a horizontal mill. Boring between centers with the work on the lathes cross slide for work that fits is still a more accurate and better but slower method for through bores than a vertical mill is with a boring head.