Choosing a lthe

Edited By Bob on 07/08/2009 12:16:29

Thanks for the advice Bob but the questioner was John Hinkley above.

Edited By John Hinkley on 20/08/2009 19:42:09

I know this is an old thread but...

Similarly to John, I'm new to hobby machining and like him, there isn't much of a selection of 2nd hand or new lathes in my area (I live in a small town in South Africa). I ended up getting the BV20 too and I'm pretty pleased with it so far. The only real trouble I've had is with the headstock spindle which keeps on working loose (especially when I do facing for some reason) and has to be tightened regularly. I'd love advice on how others deal with this issue, by the way.

Other than that, I'm pretty happy with it.

M

Hi Mark,

What do you mean with: "headstock spindle which keeps on working loose". Is it the chuck that is coming loose or is it the bearing preload? A photo might be helpful.

Thor

Hi Thor,

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What do you mean with: "headstock spindle which keeps on working loose". Is it the chuck that is coming loose or is it the bearing preload? A photo might be helpful.

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It is the bearing preload. The rear of the spindle is threaded and there is a spindle lock nut held in place by a flanged washer. This, in turn, pushes up against a disk directly to tighten the spindle (I wish there were a washer between them!). The metal disc itself is quite a loose fit inside the bearing cover plate. When it is loose, the spindle is very loose with both lateral and axial play.

But here's the problem: if I tighten the lock nut up enough to remove axial play, then the lateral play remains. I can see and hear the movement when I wiggle the chuck end.

But if I tighten the lock nut enough to remove both the axial and lateral play, then it is VERY tight. The machine turns but eventually the pressure of the locknut on the spindle disc grinds away the metal on the disk. In the picture the screwdriver points to the raised edge where the wear has taken place. Once the metal has worn away, the spindle is loose again and the process starts all over. At first, in my inexperience, I thought "gee this is a really poor design, but heck, I guess it must be normal".

it's a new lathe, so I don't suspect the bearings. I haven't removed the spindle or the bearings but I've peeked under the bearing covers and there isn't anything really obvious to see there. As far as I can tell, the bearings are ok (??).

So obviously, this is bad, bad, bad!!! As a temporary fix, I've put a rubber washer around the metal disk to improve the fit. This reduces the lateral play of the metal disk and this reduces the lateral play on the spindle substantially. Thus, I only have to tighten the lock nut to remove the axial play and hopefully not put too much pressure on the metal disk.

All thoughts welcome. I'm curious how others have gotten past this really hmm... nasty ... design.

(Sorry about the wobbly photos: I was using my phone camera and it was a bit dark.)

best

Not familiar with this lathe but seems there is something wrong. Usually there is two end nuts,one for adjustment and one for locking. .What's the grooved diameter behind the nut ? where is the drive to the spindle? Apologies if I've read this all wrong.

This does not seem right at all. There should be no wear as no stationary parts should contact rotating ones, other than the balls or rollers in the races.

On my different but similarly arranged lathe the set up is that two locknuts on the end of the spindle press a cylindrical spacer against the inner race of the tailstock bearing. A circular cover is fixed over the bearing to shield it from dirt.

From the pictures I think you may have things assembled wrongly. temporarily remove the circular plate held on by three screws. This should go on last and should not be in contact with any of the rotating parts, it is only a shield. If you are adjusting the lock nuts up against this disc instead of the bearing you will have problems - big ones.

Can you post a sharp picture of it with that round cover removed, ideally one end on and one side one?

Neil

Edited By Neil Wyatt on 13/06/2014 11:36:27