Lathe Help - not running true

[Alex779]

Hi, I am new here. A friend suggested this was a good place to get help with a problem I am having.

I have a Record Power/ Coronet lathe. I have had it for a few years and have done quite a bit of simple turning. Last week I bought a new chuck and it has identified a problem with the lathe.

The drive shaft is slightly out of true. As such the chuck 'wobbles' by about 1mm up and down as it spins. This means that I am having problems spinning work round (the main reason I bought the chuck) and also in re- mounting.

Is there a fix?

Here is a pic, I think it is a coronet Number 1, but confirmation would be great.

 

[CHJ]

Assuming you have a solid bronze front headstock tapered bearing, has it been kept regularly lubricated and is it adjusted correctly to take out any slack in the taper fit?

 

[paulm]

I think that model has a normal bearing Chas, the phospor bronze bearing being on the CL3 ? Might be mistaken on that though.

 

[Dalboy]

Check for ear in the ball bearings if you hold the chuck can you lift it up and down which will give an indication to the bearing condition. Does the shaft wobble without the chuck.

Assuming you have a solid bronze front headstock tapered bearing, has it been kept regularly lubricated and is it adjusted correctly to take out any slack in the taper fit?

This one has ball bearings front and back Chas.

 

[Alex779]

I can't see any movement, it doesn't actually wobble now I look at it. it looks like the shaft coming out of the lathe is slightly bent....

 

[Alex779]

I think I can see the same effect in the safe without the chuck, but because it is so much closer to the bearing it is less pronounced.

 

[TFrench]

Do you get wobble with anything fitted in the morse taper in it? I had a similar problem with a cheap chuck adapter - bought a nova one and problem disappeared.

 

[Alex779]

Ok, I hadn't thought of trying that. So, i put a morse tapered drill chuck in and made up a little jig with a screwdriver held against the barrel of the chuck. At a distance of around 100mm from the bearing I get a full 1.5mm of lateral movement.

 

[CHJ]

Thanks for the 'edification' on the bearings, I have no personal experience with the various models only ever assisted someone in cleaning up and adjusting a scalded bronze unit..

 

[Alex779]

So, is my conclusion that the shaft is bent accurate? I'm struggling to work out an alternative.

If this is the case, does anyone know the exact model so that I can search for a replacement?

 

[sunnybob]

Remove everything you can from the shaft, and do the same trick again holding the pencil / screwdriver lightly to the shaft.
Or, even better, do you have a dial gauge and stand? if its the shaft then you need to replace the problem part.

If it is just the chuck that wobbles, You can find the low point, mark it, and slip a piece of paper in between the mating surfaces at that point. It might take a few attempts to get the paper in the right position, but its a very old trick to square up a chuck.

 

[Finial]

It could be the spindle, but more likely to be the chuck. Runout on a chuck could be due to the insert not being tight and properly seated. But check the internal morse taper is clean and check the taper on the drill chuck for any damage. Either might cause runout in your test. If there is looseness at the bearings the lathe would be almost unusable.

When you are sure the problem is in the spindle you might try lightly skimming the chuck mating surface on it with a scraper. But before you do that perhaps you could try the pencil point test on the chuck mating surface. There could be a burr that stops the chuck seating. That could be an issue on the chuck insert too. If you see something there perhaps you could fix it with a smooth file.

It takes a lot to bend a spindle, but if someone ran a badly out of balance bit of wood at high speed that might do it. If it is bent you will have to replace it. Change the bearings at the same time.

 

[CHJ]

Looking at the image posted and others of the spindle nose elsewhere I would suspect the problem with the chuck is down to it relying on the thread alone for alignment.
There appears to be no Register for the chuck to align on.

If trueness of spindle is correct as it leaves the front bearing then I can only suggest that a chuck insert with a longer rear collar that extends along the plain spindle nose is the only way you are going to get truer running.

Is the spindle nose by any chance bottoming on the chuck thread before it is fully engaged on the spindle?

 

[Alex779]

so i did some more tests this evening and the threaded part of the shaft is definitely not running true. however, i used a scraper to dress the seating face of the spindle and visually the chuck now looks much better. i'll turn a few things tonight and see how it looks later.

 

[boomerang bender]

I have a just acquired coronet major (red painted) and bought a live centre tail stock and when when i present the tail stock to the head stock there is an offset of about 2mm low between centres i am thinking there must be some wear on the bushing on the head stock i also acquired 2 spare bushings. is there some adjustment to bring the alignment true and is it is it critical that both points should meet exactly to turn accurate work. Many thanks for any replies.

 

[CHJ]

…….. is it is it critical that both points should meet exactly to turn accurate work. Many thanks for any replies.

Not critical for between centres turning, Has to be way out before you will have troble with drive centrs not gripping.


Is critical if you use your chuck to drive between centres work or drilling from the tailstock.


In the latter case it's not just that the centres touch, they must align in both axis if a drill is to follow the centre line of the work and rill to size.


See this old post for more details