Problem with Little John Mk2

[Stephen RowleyParticipant @stephenrowley13300]

I have just bought a Ragland Little John Mk2 which is in very good condition.

After fitting a replacement motor, setting up the variable speed control and giving it a few drops of oil I fitted a new tool in the tool post and a length of Brass in the chuck, I took my first cut only to discover that the cut got deeper the closer the tool got to the chuck.

I checked everything I could think of bed ways etc but I can not get it to cut true.

Anyone got any idea of what could be the problem?

Steve

[Stephen RowleyParticipant @stephenrowley13300]

Will not cut true.

[SillyOldDufferModerator @sillyoldduffer]

Might be something or nothing. How flexible is the brass rod? It could be bending away from the tool at the tailstock end, which it can't do so much as the tool gets closer to the chuck. The effect matches your description.

As a very crude rule of thumb, metal should not protrude more that 2.5 times it's diameter from the chuck. Any longer than that and the end should be supported by a tailstock centre. Very long work and it's time to support the work with fixed or travelling steadies.

If you have a DTI try applying it to the end of your test rod and measuring how far you can push the rod sideways with you thumb. You might be surprised how bendy a stiff metal rod actually is.

Hope it's that; some of the other possibilities are much more sinister.

Dave

[Pete RimmerParticipant @peterimmer30576]

What diameter was the part you've done your testing with Steve? It might be nothing more than the brass bar is bending away from the cutting tool but as you get closer the chuck the spring in the part is less so it's forced to cut deeper.

Run your test again with something of fairly large diameter but not too long – say 1.5" diameter with only 3" sticking out the chuck. Take a light surface cut and see what result you get.

Edited By Pete Rimmer on 25/02/2018 08:49:58

[Pete RimmerParticipant @peterimmer30576]

If you run the test cut again with a larger diameter part and you're still getting a taper then take a look at this video done by a friend of mine a year ago. He doesn't mention how or if you can adjust the spindle angle but I could ask him for you if it turns out you're turning a taper due to a mis-aligned headstock. Many lathes can be adjusted on the clamp bolts:

https://youtu.be/OfjVroJxs9U

 

Edited By Pete Rimmer on 25/02/2018 09:03:20

[not done it yetParticipant @notdoneityet]

Have you followed the installation instructions on page 5 of the manual? Quite important that you do, before using it in anger. If you have done that, it will be cutting parallel and your problem is likely as above.

[HopperParticipant @hopper]

Posted by Stephen Rowley on 25/02/2018 07:48:21:…

…a length of Brass in the chuck, I took my first cut only to discover that the cut got deeper the closer the tool got to the chuck.

By how much? A couple of thou? 10 thou? 20 thou?

Over what length? And what was the diameter of the brass?

If it's just a couple of thou, it might just be a matter of shimming the mountings of the lathe bed to get it set straight.

If it's more like 20 thou, you might need to look at headstock bearing adjustment and alignment.

Or if the brass bar is long and thin, it might just be flexing away from the tool at the far end.

All this is presuming you used no tailstock centre, as you have not mentioned it. However, if you did, then the problem may just be a simple matter of tailstock alignment adjustment.

[Stephen RowleyParticipant @stephenrowley13300]

Thank you all for your replies.

I used a 3/4" osd by 3" brass bar as it was close at hand.

I have now tried a 1" osd test bar with my dial gauge on the tool post, over a length of 4" I get 41 thou on the dial gauge.

I put the brass bar into my other lathe and did the same test. it showed the tool had cut 29 thou into the brass over a length of 2"

I have added so photographs of the lathe to my album.

Steve

Edited By Stephen Rowley on 25/02/2018 11:36:47

[Tractor manParticipant @tractorman]

The Raglan 5 inch bed is adjusted by twisting the bed using two bolts that act on the base of the tailstock end foot. If the lathe isn’t bolted down and set up properly it wont turn parallel.
I doubt the headstock is out of line.

[Stephen RowleyParticipant @stephenrowley13300]

We are just loading up the cups of tea then we are going to unbolt the lathe and with the use of lasers and digital levels we are going to check the whole thing and hopefully fix the problem.

This is a very nice lathe and so much better the my Chester's 920.

Steve

[Tractor manParticipant @tractorman]

You need to turn a test piece rather than use levels and lasers. There’s no short cut to getting the bed right I’m afraid.

[not done it yetParticipant @notdoneityet]

You don’t need lasers and particularly fancy equipment to set up these lathes – no more than they used 50 years ago.

A trial cut of a couple of thous. on a test piece, plus a micrometer, to measure the diameter of the cut,9 is all you need to check it. Adjustment is equally simple and reliable.

[BC ProfParticipant @bcprof]

Many many moon ago I was fortunate enough to be able to attend an engineering evening class at a a local College of FE. ( remember those ) The instructions from an excellent engineer went something like this " You old boys have it easy with your little lathes not like these things ( he was leaning against a large DSand G at the time ) Put it onto its stand or onto a good solid bench, not a bit of 1/2" plywood . Bolt down the headstock . Put the largest diameter bar that you can fit into the chuck .the longer the better. Lock the spindle . Wind the carriage as far away from the chuck as you can get it . Fit a DTI and adjust it so that you can easily see the dial . Lock the carriage to the bed and then slowly tighten the bolts at the tailstock end . you should aim to get no movement of the DTI . You now have the lathe in place with no strain on the bed . Remember when an engineer talk about levelling a lathe its nothing to do with it being horizontal . You can have it at 45 degrees if you want although I would not recommend trying it with on of these ( D S and G ).

Now do you test turning . Assuming that the headstock is in line you may need to shim the tailstock end but for what you do you probably wont need to .

I have used this method on every lathe that I have owned over the past 50 yrs

Brian

[Neil WyattModerator @neilwyatt]

Very useful post, Brian.

My approach is to only fit the tailstock bolts finger tight. I think Mike Cox uses a resilient mount at the tailstock end.

Neil

[Stephen RowleyParticipant @stephenrowley13300]

Well thank you all for your advice. The lathe is now running true.

The problem turned out to be an accumulation of several things from the wrong size shim, the motor and the floor.

But all is now will and I have a very good lathe.

Thank you all

Steve

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