The perfect ME Lathe

[JasonBModerator @jasonb]

Peter a few comments on teh above

 

As the topslide can be positioned anywhere along the cross slide its is easy to cover the full face of a large item, I skimmed the 10″ faceplate no problem.

 

Would have to double check the travel but the later models have the leadscrew cover which does limit travel slightly.

 

It all depends on how much screwcutting you want to do, on that traction engine, about 1500hrs work I only needed to turn the 1/4x16tpi square thread brake screw & nut. Lets face it most models will have standard tpi or pitchs specified and there is far less to go wrong with a banjo and changewheels than a stepper motor and sensors on the spindle.

 

Speed wise the flywheel and final drive on the TE were both 9″ OD no problem turning them at 200rpm as I’ve said before forget the books on our size lathes and go by what feels and sounds right. They do suffer a slight loss of torque on large dia work at lower revs, on the 9″ stuff 0.025depth of cut was about as much as it was happy with more on the facing cuts as the feed is halved. Mine will actually run at about 45rpm and I don’t find stopping at the end of a thread a problem.

 

J

[Peter G. ShawParticipant @peterg-shaw75338]

Jason,

Fair enough, if it works then ok, but as a beginner with not much experience I have to start somewhere and reading Tubal Cain’s charts is a start. I take your point that your experience is that it is ok.

 

When I bought my present lathe, I did a lot of research looking at things like speeds, physical capacities eg slide travel, weight etc. What this showed up was that more expensive machines had lower speeds and more travel which was one of the reasons why the Myford was so expensive. Unfortunately, I knew enough to know that I did not know enough, if you get my gist, otherwise I would, perhaps should, have bought a S/H Boxford which had lower speeds of around 40rpm. Which is why I bought my present lathe as a new machine being, as I thought at the time, the best available taking everything into consideration.

 

In respect of screwcutting under power, I once tried it at 250rpm and frightened myself silly. That was on a Hobbymat. On the present lathe I have tried at 125rpm, better, but the major problem is that of inertia, ie it does not stop dead. As it happens, I have recently successfully cut a 30mm long thread but even so, I have had to switch off the motor and hope the inertia got me to the right point as otherwise I ended up turning the chuck by hand, or whipping the cross-slide smartly backwards at the appropriate time. If I had a much lower speed, say in the teens or perhaps 20’s, I would have much more time plus the inertia (if I’ve got the phrasing right) will be less, hence it will be easier to stop at the correct point.

 

 

Regards,

 

Peter G. Shaw

[Alan JacksonParticipant @alanjackson47790]

I proposed and built a design for an ideal Model makers lathe in MEW151,152&153. This seems to incorporate many ideas suggested in this thread. It also has a top slide that can be positioned anywhere on the cross slide, which was described in detail in MEW 119,120 & 121. It was mistakenly referred to as a CNC lathe but is much more than that as it can work equally as well in manual, powered driven axes or full CNC axes. The idea is that the operator can choose (and even mix ) these operations together to get a range of versatility which is not possible with existing available machines.See this 

http://www.lathes.co.uk/stepperhead/

Alan

Edited By Alan Jackson on 28/09/2011 11:56:49

Edited By Alan Jackson on 28/09/2011 12:04:53

[John McNamaraParticipant @johnmcnamara74883]

Hi All

For a long time I had a very early (Pre war) flat belt driven Colchester with change gears. I fitted it with a DC motor and speed control not a modern VFD. The variable speed allowed me to screw cut up to a shoulder with relative ease. The DC Drive was an enormous help. That together wit a quick flick of the cross slide handle and I was able to job the job with little effort.

My current lathe is a German VDF Heidenreich and Harbeck RO 80 it does not have a VFD and the headstock is driven directly with no belts. It does however have slow speeds down to 25rpm. This lathe is about 25 years old.

A feature that is extremely useful is the wet multi plate clutch(s) and a reversing gear set that are engaged by the forward and reverse lever. This gives the same functionality as a clutch driven car. The main motor runs continuously when the machine is turned on. you can throw the leaver for an abrupt start or reverse or ease it in. I am assuming here that common sense will prevail and that a Machinist would not deliberately slam the lathe into reverse at high speeds. I am sure it can take it but I do not intend to try it. This machine has a DIN taper spindle with 4 bolts so there is no risk of the chuck coming off a thread. from the inertia of reversing. Threaded spindles should be a thing of the past.

The apron hand drive handle also has a movable graduated dial. Having set the cross slide dial to zero at the start of the cut and the saddle hand wheel dial to the stopping point. I am ready to cut the thread. So I engage a low gear, have one hand on the reversing lever one hand on the cross slide handle, make the first cut until the saddle hand wheel reaches the zero point, at which point I flick the cross slide handle to withdraw the tool and throw the clutch to reverse the machine. I mostly cut metric threads and so I usually leave the half nuts engaged unless it is a long thread.

I think an ideal lathe should have this setup if mechanical. Or a VFD that is capable of slow speeds (Not all are), without having to shift belts, a soft start and the ability to reverse while running with ramp up and ramp down so the machine is not subjected to stress.

Also a large graduated apron feed dial is a must.

If any member has a similar machine please IM me it would be good to compare notes.

Cheers
John

Edited By John McNamara on 28/09/2011 14:26:09

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