Enlarging the spindle bore on a Unimat DB200?

[yukon_rose]

The spindle bore on my DB200 is just over 0.250". I would like to bore it out to as large as I can and still leave it functional.

Suggestions and/or concerns please.

Gary

 

[pavyan]

If you mean EMCO UNIMAT DB200, be careful: there may be a small amount of material there (e.g. rear bearing). Besides, it is a old, good, branded machine - so the spindle is probably hardened/tempered in mass or case-hardened. This will make it difficult or even impossible to enlarge the bore (perhaps to a maximum of ~8,5mm, i.e. like an "inlet" of the spindle).

So, there is a question: is it worth the risk, 6.35mm only to 8,5mm? I don't know.

I am posting a drawing of the headstock from a very useful website https://www.lathes.co.uk/unimat/

 

[markba633csi]

I would leave it alone- if you want a bigger spindle get a bigger lathe is my advice

 

[pavyan]

I think additionally, there is another danger: it is a hardened element (and ground, has a bearing race), so there may be stresses in it, but balanced stresses. After removing some material inside, this balance may be destroyed, which may cause the spindle to bend - especially in the rear, thin-walled part.
What would be the effect - it is easy to imagine.

I think that the risk of failure (even partially damage to the spindle) is too high - I would not do this upgrade too, because it may turn out to be a downgrade.

 

[markba633csi]

Agreed, and considering that the Unimat has a tiny work envelope and is lacking some important features like threadcutting (unless you have the expensive attachments) even a small mini lathe or an Atlas would be an easy upgrade path

 

[Ulma Doctor]

Pass on boring the spindle, get a steady rest if you’re doing long work