Myford ml7 lathe problems

[fastjohnrsParticipant @fastjohnrs]

Hi I've been having problems with my lathe since I recently got it, it seems to be cutting material in an eccentric, I put this down to a faulty 3 jaw chuck not running true, so put my 4 jaw chuck on got some 10mm silver steel which I assume will be reasonably true/parallel, using a dti I got the material true to within 1-2 thou, I turned the chuck via the drive pulley, touched the silver steel with my cutting tool, when turning the chuck the tool was marking the material and when turned 180 it was missing the material, I'm pretty baffled by this, I hope that someone can point me in the right direction to the solution to this problem and its just me being an amateur thanks in advance for any help.

[fastjohnrsParticipant @fastjohnrs]

[Neil WyattModerator @neilwyatt]

Simple answer, if the tool is just skimming the work it will pick up eccentricities of well below a thou. You need to spend more time truing up the work. If you want to turn dead true to the external diameter you need to get the DTI showing as near to 0.000 error as you can get it.

Neil

[NobbyParticipant @nobby]

Hi
It seems to me the lathe is is wobbling . Is it on a firm base ? , Or they maybe a problem with the belt drive
Make sure its nice a level longways & X ways
Nobby

[NobbyParticipant @nobby]

II would have thought there would be more respond's to this . Have a look on U tube There a a few items on there
about leveling
Nobby

[John HinkleyParticipant @johnhinkley26699]

I am neither Myford owner, nor expert, but I would go back further in the drivetrain and check that the spindle wasn't either bent or not running true for some other reason. To paraphrase what Sherlock said – eliminate the obvious and see what's left! (I don't think he actually said that, but he would have done if I'd written it. )

Good luck,

John

[Gordon WParticipant @gordonw]

All lathes and all chucks will be eccentric, it's a matter of how much. If the spindle is bent this will show if a long piece of straight bar is put in the chuck ,the end will move in a circle. This is unlikely. If the 3 jaw is running out, most are, you have to machine all concentric diameters and square faces at on setting. Try turning a test dia. and then checking with DTI. For light test cuts it won't matter about aligning and bolting down etc.

[Kevin FParticipant @kevinf]

How much material do you have protruding from the chuck ? Also is the material that is to be machined supported by a revolving centre ?

[Neil WyattModerator @neilwyatt]

We know the material is "true to within 1-2 thou" and the tool was set so it "touched the silver steel with my cutting tool".

It sounds to me like it's a simple case of the tool set to graze a slightly eccentric workpiece – cutting one side and not the other is exactly what I would expect in these circumstances.

Beginners often don't realise that 1-2 thou is quite a large amount when dealing with concentricity.

Neil

[Kevin FParticipant @kevinf]

Posted by Neil Wyatt on 27/12/2014 13:41:53:

We know the material is "true to within 1-2 thou" and the tool was set so it "touched the silver steel with my cutting tool".

It sounds to me like it's a simple case of the tool set to graze a slightly eccentric workpiece – cutting one side and not the other is exactly what I would expect in these circumstances.

 

The reason I asked about how much material is protruding from the chuck jaws ,was because the material could've been clocked up close to the chuck and the tool could have been touching the material 50mm or so away from the chuck jaws ,if the chuck jaws aren't square you'll get a bigger run out the further away you go from from the jaws .

I doubt very much that the spindle is bent , there's a possibility of play in the spindle bearings ,but without more info or seeing the lathe first hand and carrying out a detailed examination we can only offer a number of possibilities at this stage .

Edited By Kevin F on 27/12/2014 14:41:15

[fastjohnrsParticipant @fastjohnrs]

Hi guys thanks for all the advice and suggestions given, I have tightenend the spindle bearings as there was a bit of movement in the spindle due to this, also I removed the chuck and clocked the spindle it's seems to be spot on, maybe I need to true it up a bit better in the 4 jaw chuck to 0.000 thou, also I could be doing with ensuring it is level on the bench, also maybe I'm expecting to much

[RobboParticipant @robbo]

Did you lock the cross-slide when taking your measurements? Slight play in the feedscrew/nut can give an error if you nudge it when taking stationary measurements.

[john lavinParticipant @johnlavin61025]

Hi new to the forum so may not come across very clear.

I have bought a Myford ml7 which I intend renovate , I have done a bit of stripping down but have come to a stop.

My problem is with the gear box and leadscrew I dont know how to separate them,they are joined by a sleeve about

three inch long with two roll pins which I considered to be one for the leadscrew and one for a stub from box.

With the pins removed I fully expected to just slide the leadscrew away from the box but I was wrong I am hoping someone can put me back on track. Thanks for any advice. John

[steamdaveParticipant @steamdave]

Are you a member of the Yahoo group for Myford lathes? If not, you should consider joining; there are lots of knowledgeable folk there who would be bale to help you (not saying they aren't knowledgeable here, also).

https://groups.yahoo.com/neo/groups/myfordlathes/info

Dave
The Emerald Isle

[davebParticipant @daveb17630]

If it's a Myford gearbox the leadscrew passes through the gearbox, there is a gear behind the inner cover, both outer and inner covers have to be removed to get at it, also remove the R/H leadscrew bracket which should be secured with 2 screws and 2 dowels. Make sure the clasp nuts are open then carefully withdraw the leadscrew to the right.There is an earlier gearbox which looks similar to the later one except the output gears are fitted under a cover on the right side of the gearbox. I've seen a few machines with the leadscrew joined just ahead of the gearbox. The joint is both tight and pinned, it's probably best to treat it as a solid leadscrew. If the joint won't pass through the clasp nuts you will need to slide the saddle off the end of the bed.

[HopperParticipant @hopper]

Yes, that pinned sleeve joint on the leadscrew can be nigh on impossible to get apart. I heated mine with a large propane torch as hot as I cared to and still it did not come apart. As I did not want to be pounding on a precision unit such as the leadscrew I just left it together in one piece. Better to follow the advice above for removal.

[Billy BeanParticipant @billybean67480]

I am currently speaking to Myford ref purchase of a new lathe.

For spare parts , technical advice, drawings, etc, you will find Myford extremely helpful.

myfordinfo@aol.com is the e-mail or 01422-885766

BB

[john lavinParticipant @johnlavin61025]

Thanks for replies from,

Steamdave, DaveB, Hopper, & Billy Bean, I will go along the sugested route and remove them intact.

I also intend to look at Yahoo lathes info, thanks again John.

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