Home made rotating centre

Hi All

Years ago I made a rotating lathe centre using a crowded needle roller bearing at the front with a ball thrust bearing behind. The outside diameter was just below 1" diameter as this avoided the restriction of the then conventional rotating centres featuring a large diameter body. This proved to be very useful over the years so recently I gave it a makeover and reground the point. I had a similar needle bearing and thrust bearing so I made another centre for my Stepperhead lathe. The reduced diameter body can retract into the tailstock barrel for maximum access. The reduced diameter point was just to see if it would be advantageous. The points can be exchanged if required. After doing all this I looked on Ebay and found that you can buy these quite cheaply, Ah well. I have added a couple of pics in my album.

Alan

> After doing all this I looked on Ebay and found that you can buy these quite cheaply, Ah well.

Never a good idea to do that

Neat in the execution. I assume Stepperhead is continuing to earn its keep then?

Neil

At least you know the quality of the one you built, and not hoping that the eBay cheepy will live up a “fit for purpose” usage

Neil,

"Neat in the execution. I assume Stepperhead is continuing to earn its keep then?"

Yes, I used it to make the Morse taper by setting the X and Y axes to cut the taper and I also ground the points after hardening them using the milling head with a diamond grinding wheel.

Alan

Alan

What is that you can buy quite cheaply on eBay, is it the 'points' or do you mean a complete revolving centre?

If its points what should I search for?

I like your self built one it looks really neat.

Ian P

Some notes on these type of centres.

I have one with needle bearings in, a commercial one actually made by Jones and Shipman and TBH it's the worst centre I own, if it wasn't so handy being low profile I'd bin it.

The problem is unless you can control the bore and press fit of the bearing very accurately you cannot control radial movement. The J&S one when used leaves a finish akin to fine knurling every time and if I swap to another centre it cures it.

Even a simple centre with two deep groove bearings has control over radial load as when axial load is applied it pushed the balls back akin to an angular contact bearing.

The Locatelli production wood lathes have a hydraulic tailstock in that as the tool moves towards the headstock it reduces pressure so the long wooden 'spindle' it id turning isn't under too much pressure and you finish up wearing it

Unfortunately this means they often have too much pressure on at the start of a cut and they burn bearings out quite a lot.

After a while we changed the front bearing from radil bearing to angular contact thinking this would cure the problem but all it did was to extend the life by a few months.

Then we swapped the angular contact to a taper roller which was a bad move as not seen a centre for repair in the last 4 years

John,

I made this centre about 40 years ago and it has been fantastic and never given rise to any of the problems you seemed to suffer. The hardened steel centre has a close running fit even today. It has been used and abused and very rarely lubricated. It does not suffer from chatter or affect the surface finish. Just does its job.

Alan

Ian P this is what I found on Ebay

http://www.ebay.co.uk/itm/2MT-SMALL-BODY-REVOLVING-CENTRE-FOR-MYFORD-LIVE-CENTRE-/370825984005?hash=item5656f37805:g:bzgAAOxyHE5RqKa6

Alan

That RGD live centre looks quite neat so thanks, I thought it was the replaceable points that were on eBay but I could not find any.

Relying on the (albeit very high) precision fit a needle roller bearing for a spindle carrying work being machined does not seem like good engineering practice but as you have found, it does work in practice!

I have an MT2 live centre with its front bearing being a crowded roller type, however the inside diameter of the outer race has the benefit of being adjustable.

Ian P

Ian,

May I suggest that you read through Nick_G's thread **LINK**

MichaelG.

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[Alan] ... Yours looks a superb job.

Michael

Not your fault, but the link is almost 'pointless'.

I probably read that thread when it was current, now however with the passage of time, the images that would have allowed it to make sense do not appear.

I will stick to the live centres I already have.

Ian P

Sorry, Ian

... I assumed that photographer Nick would manage his photos better than that.

Here is the missing point:

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MichaelG.

Michael, thank you for that here are the details of my version, discuss

Alan

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Alan,

Whilst yours lacks the ultimate finesse of the Gepe equivalent, it is obviously beautifully made and properly proportioned.

The commercial offering is badly designed, and uses poor/unsuitable materials. QED

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MichaelG.

I find a live centre an invaluable tool but if you want a really accurate job and no doubts a fixed centre can't be beaten, it's just a bit more messy

I suspect the answer is in "The problem is unless you can control the bore and press fit of the bearing very accurately you cannot control radial movement."

Alan's setup lets him work to very fine tolerances.

Neil

For completeness ... here are some details of how Gepy does it.

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apologies for the typo in my previous post

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MichaelG.