Chinese milling adapters for a mini lathe

[bigmini]

When I purchased my lathe, I also bought one of those milling adapters like this one:



Whether or not I use it with the plate I made to allow it to work full width, the thing flexes and chatters something awful .

I use an ER25 collet system to hold the slot drills, and despite running very low speeds, making sure the teeth were cutting and not rubbing, tightening up gibs on the cross slide and locking down all the locks, I was able to obtain a more accurate finish by chucking the work in the 4 jaw and facing it instead.

In fact, there is visible movement back and forth of the top of the adaptor as the end mill cuts.

The problem is less pronounced when cutting aluminium rather than steel, but it doesn't go away. Is this adapter a waste of space fit only for the bin, or is there more I can do to stiffen it up?

[andyf]

I don't like mine much either, Bigmini - see http://andysmachines.weebly.com/the-vertical-milling-slide---criticisms.html . But as you will see from lower down that page, another Andy gets along OK with his, and mine is often borrowed by a mate who uses it on his Myford, though he says he only takes very shallow cuts.

I think the wobble is probably due to the distance between the work and the lathebed, which boils down to overhang even though some of that is verical rather than horizontal, coupled with slop in the slides (locking your carriage down might help) and the fact that the milling slide is only held down by two or three closely spaced 6 or 8mm bolts. 

Andy

[bigmini]

Your lathe looks like a smaller version of mine Andy. Mine is a Titan TL210(8x16), which is basically a stretched mini lathe, but with some extra goodies like a threading dial and proper headstock bearings.

I've actually made the adapter plate to a similar design to the Little Machine Shop one. Mine is much thicker (around 15mm) to make it as rigid as possible. Yes, I had to relieve it underneath to clear the oil ports and cross slide nut. I also drilled the holes in it to move the VMS back closer to the cross slide, sacrificing the ability to rotate for supposedly better rigidity. I plan to use the same plate to mount other stuff on the cross slide as well, so eventually it will be full of holes.

I was reluctant to drill and tap the cross slide itself because it is actually quite thin.

I like the idea of cutting off the sides of that stupid vise. Then I could drill and tap what's left to take the vise or a backing plate to hold clamps.

So far, I get better results holding things in the toolpost if they'll fit.

[maybecnc]

I don't have that milling attachment. I do milling with the compound vertically. Instead of a cast iron angle adapter I use a solid 50x50x90mm steel block to hold the compound. Have made a small face plate, drilled and tapped, that is bolted to compound.  It does the job but I hope not for much longer. A mill is on my purchase list.

Lathe cross slides aren't usually truly square to the lathe bed and that may be a cause for some of your problems. Don't mill feeding the cross slide from front to back. Mill always feeding it from back to front.

[andyf]

Hi bigmini,

There does seem to be a family resemblance, but I think yours may originate from a different Chinese factory. Mine came from an outfit calling itself Weiss Machinery (doubtless in an attempt to give it an air of German respectability) and their "8x16" has their hallmark curved front to the headstock and gear cover.

I think some basic designs for various People's Lathes must have been prescribed in the past, so we now see variants of those designs from Chinese manufacturers. For example, Ketan at Arc Euro Trade says that the ubiquitous "7x12 mini-lathes" by Sieg and Real Bull are all adaptations of a old Russian or East German machine.

I appreciate you don't want to drill holes all over your cross-slide, but if your lathe has the same awkward method of swivelling the topslide as mine originally did, the forces involved in milling must exert some considerable leverage on  the clamp disc within the cross-slide. Thus, it might be worth drilling/tapping a single M8 hole in the rear LH corner of the cross-slide so the back of your adapter plate can be secured to counteract both the twisting force and any tendency for the plate to flex upwards.

Andy

[Bogstandard]

I think your major problem is taking things a little too far. That vertical slide is a mighty big lump to have on such a small bed, but should still be able to be used, after a fashion.

Many years ago, when money was really tight and small machinery, like hobby mills, just weren't available, a vertical slide was the only real way of getting some semblance of milling done in a home workshop, and during it's time, people managed to perfect it's use and some marvellous creations were produced using them.

But like everything else in the machining world, you have to get to learn to use it correctly. Whatever is relevent to a milling machine must be used with this attachment. Rigidity of the workpiece and a full understanding of the complexities of milling cutters and their uses. Just sticking a cutter into a collet chuck and hacking away at a lump of metal held in the vertical slide will be doomed to failure. Climb milling is usually the first stumbling block, followed by attempting to take too heavy a cut or too fast a feed. Climb milling is easily solved, DON'T DO IT, as to the others, that is a matter of yourself learning how far you can push the limits of the attachments before you start to get unsatisfactory results. With a milling machine, you might be able to take a 50 thou cut, but using a vertical slide, you might find you can only take 2 thou, it all depends on rigidity and setup.

So play about with it a little longer and find both it's and your limitations, and maybe you will find a way for yourself to get good results, but on no account will it ever be as easy or as fast as using a true milling machine.


Bogs

[DavidA]

maybecnc,

...Lathe cross slides aren't usually truly square to the lathe bed ..

So how do you manage to take a square cut across the face of anything if your cross slide isn't square to the centre line of the lathe ?

I would have thought that the first thing needed when setting up the lathe is to attain this squareness.

Dave.

[maybecnc]

So how do you manage to take a square cut across the face of anything if your cross slide isn't square to the centre line of the lathe ?

Dave, on lathes you don't and you shouldn't expect it to work that way. If you check lathe specs, even Hardinge say it is not truly square. On the cheap Chinese ones the error may be is a bit bigger so the problem is increased.
To mill square on a lathe there is the need to use the DTI to check part alignment for cutting on each face. Many times I do a first cut just to check how far it is from square and then realign the part to finish the job.

The reason to mill on a lathe always feeding the cross slide from back to front is to ensure the milling cutter will be cutting to side. If feeding cross slide front to back the end mill is forced to remove metal at the front of the end mill, and then it is easy to see the end mill bending as you feed cross slide. And it will wear end mills on a flash.

Anyway, perfect results shouldn't be expected milling on a lathe. But if one has the trouble to improve lathe fittings until he gets very reasonable / good results milling on a lathe, then he gets a heck of a good lathe that will make quite good lathe work.

Jose

[lordedmond]

Its not that the slides are not square

when a lathe is set up correctly the cross slide is set up to face slightly concave by about a tenth ,they do that to ensure the face cannot be convex ,
 but in practice it would make no difference in milling, I have built two loco's using that very same setup , ok it was on a ML7 but is was still a vertical leaning curve with cutter walk outs into the bargain


But it did work had to shuffle the rods along to mill the entire length



Stuart


look like you posted as I was typing

[DavidA]

Jose,

Can't say that I agree with you entirely.  I would expect (and get ) my old lathe to track square to less than 0.0005" across the face plate. And also checked with a dial guage.  Maybe that's not dead square,  but it's close enough and the lathe is about 50 year old.
If your trying to square the end of, say,  a bit of 50 X 10 mm bar by clamping it on the cross slide then I was always told that you get the edge facing you to run true to the lathe centre line then you can clean up the end with an end mill using the cross slide. If your cross slide isn't somewhere near,  then the end won't be square.

My concern was that you must also be accepting this error when you are facing off a job in the chucks.

If it works for you,  then ok. Just me being picky.

Dave.

[philf]

Jose,

Can't say that I agree with you entirely.  I would expect (and get ) my old lathe to track square to less than 0.0005" across the face plate. And also checked with a dial guage.  Maybe that's not dead square,  but it's close enough and the lathe is about 50 year old.
If your trying to square the end of, say,  a bit of 50 X 10 mm bar by clamping it on the cross slide then I was always told that you get the edge facing you to run true to the lathe centre line then you can clean up the end with an end mill using the cross slide. If your cross slide isn't somewhere near,  then the end won't be square.

My concern was that you must also be accepting this error when you are facing off a job in the chucks.

If it works for you,  then ok. Just me being picky.

Dave.

The recommended way of testing the squareness of the cross-slide to the spindle axis is to grip a parallel lightly in a 4-jaw chuck. You then clock one end of the parallel, rotate the spindle through 180 degrees and clock the other end. You then need to tap the parallel until, when rotating through 180 degrees, you have exactly the same clock reading. You can then set the parallel horizontally and run the clock along the parallel. The recommended limit is 0 - 0.0005" hollow or concave on a 12" diameter (or 0.015mm over 300mm dia.) for a tool room lathe.

I haven't tested my lathe but know that, just by clocking the faceplate, I would expect a much lower runout than 0.001" - this is because I machined the faceplate on the lathe. I expect that the faceplate is slightly hollow or concave which, if it's not perfectly flat, is how it should be. Just clocking the faceplate, therefore means very little unless you know that it's perfectly flat and rotates with zero runout.

A perfectly square cross-slide is fine but the difficulty in achieving this means that most will be made to turn a concave surface for practical reasons.

This level of out-of-squareness wouldn't be noticeable on a 10mm end mill held in the spindle of the lathe. You may notice problems with a 12" fly-cutter. It's analogous with most vertical turret mills which won't have the spindle tramming perfectly with the table.

Phil.

[maybecnc]

I referred the out of square possibility because bigmini and myself have both small Chinese lathes. For many posts I have read on several related forums there are cases of out of square cross slide far from the worst spec you can imagine. If for a general purpose lathe is 0.02mm over 300mm, for a toolroom lathe 0.01mm over 300mm and for a Hardinge toolroom lathe 0.005mm over 230mm, one year ago I have read that one found on his small Chinese lathe 0.25mm over about 70mm of cross slide travel. In such cases it is a real problem for any milling work.

Mine has now about 0.015mm over 100mm and that will be fixed soon. And believe me, I would love to put my hands on a good old small lathe! Until that day I'll be improving the one I have as needed.

Jose

[bigmini]

Thanks all for the responses. I guess I'll have to accept the limitations until the Minister for Finance says I can afford an X2 or an X3. Perhaps if I make her a steam engine  . So far it's pretty much been tooling and mods for the lathe itself, and fixes for other stuff.

In the meantime, I did find early on (after breaking the tooth off a cutter) that climb milling was a no-no. I've never attempted to figure out how far out my cross slide is, but that's next. It would certainly explain the little row of circles I get when milling . It does mean I need to check how flat the pieces I faced in the chuck actually were.

I can still get a reasonable result on aluminium, but 1020G steel seems to be a problem with anything larger than an 8mm cutter.

For making keyways and flats on small shafts, it's easier to remove my QCTP and clamp the whole thing on centre in the 4-way toolpost.