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DIY metric dial conversion and feedscrew upgrade on ML7

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Shaun Belcher20/09/2021 06:22:01
65 forum posts
23 photos

Firstly, I should start off by saying i literally have zero experience with lathes and/or machining other than what we did at school and even then they never taught us anything about using them.

I recently purchased an ML7 that was in rather poor condition, and seen serious abuse, but for the most part still has a fairly good bed with little wear that I can tell.

The feedscrews were totally shot, and one handle had been re-attached with a pin put through rather than threaded on.

Dials were sloppy and imperial, so decided my first project on the lathe should be to make some upgrades if nothing else!

Photos are sorta self explanatory, but basically I machined some dials out of stainless which was a very difficult job, having gone through several CCMT diamonds to cut these out!

End result was well worth it however and it now runs on a roller bearing that should stop wear on the face of the casting.

I made my dials similar to other designs people have shared on here, they are yet to be engraved, but have fitted it for testing out.

I made new bronze nuts and got my neighbour to machine the rest of them out on his CNC mill.

The threaded rod is an off the shelf item that costs next to nothing and is a standard 2mm pitch trapezoid threaded rod at 10mm diameter.

Im 99% sure this is what myford solutions are making their feedscrew kits out of, all I had to do was machine the ends down to the correct size and tap the threads.

 

See photos below:

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And just something to be careful of when machining stainless, you get heaps of steel wool that needs to be kept away from the chuck or this happens!

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Edited By Shaun Belcher on 20/09/2021 06:51:37

Nigel Graham 220/09/2021 09:55:20
1784 forum posts
22 photos

Good work!

I must admit I would have used aluminium-alloy for the new dials, but replacing the originals with readable ones is a big improvement anyway!

Some tips.....

Don't let stringy swarf built up as much as that like that. (Some other metals, and some plastics, also behave like that, depending to some extent on the tool used.) For all but the finishing-cut, I pause frequently to break the ribbon, wind the saddle well clear and let the swarf fall clear. If necessary stop the lathe and brush the swarf safely clear - I use a worn-out paint-brush.

They seem rather long overhangs for the work. Did you use a tailstock centre on that length of bronze? The snag as you probably found is that the top-slide then runs up against the tailstock, necessitating either excessive tool overhangs or swivelling the top-slide - the latter of course denying using its own leadscrew and dial without a lot of trigonometry.

Ady120/09/2021 10:07:29
avatar
4827 forum posts
724 photos

Looks great, you'll be really chuffed

Shaun Belcher21/09/2021 01:09:11
65 forum posts
23 photos
Posted by Nigel Graham 2 on 20/09/2021 09:55:20:

Good work!

I must admit I would have used aluminium-alloy for the new dials, but replacing the originals with readable ones is a big improvement anyway!

Some tips.....

Don't let stringy swarf built up as much as that like that. (Some other metals, and some plastics, also behave like that, depending to some extent on the tool used.) For all but the finishing-cut, I pause frequently to break the ribbon, wind the saddle well clear and let the swarf fall clear. If necessary stop the lathe and brush the swarf safely clear - I use a worn-out paint-brush.

They seem rather long overhangs for the work. Did you use a tailstock centre on that length of bronze? The snag as you probably found is that the top-slide then runs up against the tailstock, necessitating either excessive tool overhangs or swivelling the top-slide - the latter of course denying using its own leadscrew and dial without a lot of trigonometry.

I only really went with stainless because it was harder wearing and keeps a good shine, aluminium would have been far easier to machine.

Your right about the overhang, I have no idea how far is too far, but I did end up using the tailstock when I could, especially with the stainless.

Main problem I found was I didnt want to cut it down smaller as I feared I would have less material to work with in the chuck, since you loose alot just with the bit you have to waste in the chuck itself. Perhaps there are other ways around this, but the biggest issue i found (particularly with smaller parts) was that the tailstock gets in the way of the saddle/crossslide when you try and make a cut.

Yes you definitely need to be careful of the swarf, stainless seems to be the worst metal ive ever dealt with, it helps if you stop cutting periodically to reduce the length of the swarf that comes off, I was being a bit careless here, but had been cleaning it up at times, there was a huge pile on the floor that filled a couple of bags and it was razor sharp. What actually happened on this photo was a long piece of swarf spun on the chuck and then picked up the rest of the stuff i had sitting on the bench and it flung everywhere. I got showered in the stuff.

It also came off the lathe when cut extremley hot.

I dont think i had the greatest tooling either, my HSS parting tool would not cut the stainless at all and just melted and i needed to use a hacksaw instead.

I have just been getting by with a boring bar with a CCMT tip.

Need to find out whats the best kind of tooling to use on this too.

Nigel Graham 212/10/2021 22:53:16
1784 forum posts
22 photos

Yes, that is always a problem, the material lost by having to cut a billet from a longer stock bar! I've sometimes lessened the waste by using a fixed steady but it's more clutter on the lathe.

The problem of the tailstock obstructing the top-slide is by no means confined to the Myford lathes. (I own both an ML7 and a Harrison L5 - same difficulty on both.)

I wonder if the stainless-steel you were using was one of the less free-cutting grades. I think what happened there was work-hardening. The tool needs to keep cutting. Let it rub by pause or by the edge wearing on a material prone to work-hardening, and the material will win.

It's even more of a problem with a delicate thing like a parting-tool, for which sharpness, tool-setting and rigidity are particularly important. Also, for an HSS parting-tool the edge must be square across. If ground at an angle to the lathe axis, the cutting edge length hence swarf width exceeds the blade and kerf width, greatly increasing the risk of jamming. (Moulded carbide parting inserts are not only square-tipped but also have a chip-breaker groove along their tops.)

Also keep the tool and work well lubricated with cutting-fluid. I apply it with an old paint-brush.

'

if you turn a stringy material, watch where the ribbons are going.... Machining phosphor-bronze one day, I was happy to see the very long helices were falling to the front of the lathe, but failed to spot one exploring the back of the lathe until "POP!", and that was it. It had found a gap past a rather inadequate guard, and wormed itself into the 3-phase motor I'd fitted. Though it did not damage the motor it wrecked the inverter!

Martin Connelly13/10/2021 08:48:24
avatar
1938 forum posts
207 photos

As well as too much tool overhang wood packing under the tool is also a bad idea but I think you figured that out as later there was metal packing under it. You will probably need to build up a stock of suitable pieces of shimming to get good centre height on the tool.

Holding the leadscrew directly in the chuck jaws was probably not best practice either, some packing such as aluminium or copper would have helped avoid marking the threads. A piece of copper pipe with a slit cut along its length for example.

Most 3 jaw chucks are not good for holding parts concentrically, there is usually some runout. For a lot of jobs this does not matter but for a leadscrew where you want the turned part to be concentric to the thread it is important. A better option would have been to set it up in a 4 jaw independent chuck. You may have set this up correctly and have no problems in the future but if you find you have regular banding at the screw pitch when facing off that would be something to look at. I know you may currently be constrained by the tooling you got with the lathe and not yet have a 4 jaw chuck but these are some of the things you will find you need to consider in the future.

Enjoy your new pastime.

Martin

Richard Millington14/10/2021 08:09:19
38 forum posts

Nice job, for the tool shims - if you can find some metal pallet strapping cut it up to length with tin snips.

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