# Centre Drills



## JimM (Jun 11, 2009)

When using centre drills to create a mounting point for a lathe centre - how do you know what size drill to use

Is it simply a question of using the largest that you can for the stock or is it more scientific than that ??

Cheers


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## Maryak (Jun 11, 2009)

Jim,

IMHO it's more the opposite, the centre hole should be the smallest that will adequately carry the load with a view to the finished diameter, especially if it is visible in the finished job.

Others may have a different approach.

Best Regards
Bob


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## Mainer (Jun 11, 2009)

What Bob said -- elegance dictates small center holes.


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## kvom (Jun 11, 2009)

The "scientific" answer is that a given size will support a maximum weight safely. For model-size work a 0 or 1 center drill is going to be good for almost everything, and a 00 may be needed for very small stock.


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## Blogwitch (Jun 11, 2009)

Now here is something to get your brains working, and it has been discussed on here before.

If you are doing straight between centre turning, then you will have no problems using standard centres or standard centre drilled holes.

But what happens when you come to do taper turning between centres.

The angles between the centre hole and the centre don't match up quite right. Or do you just ignore it because the error is so small?

John Stevenson showed an elegant solution using a ball bearing as a centre support, as it will always sit perfectly against the sides of the centre drilled holes.

Or do you go to the expense of buying the curved face centre drills that overcomes the problem from the other way around.







Discussion time.


Blogs


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## gilessim (Jun 11, 2009)

Just a thought here, a centre drill makes a slightly more refined center punch mark for your drill bit to follow, the very small ones break quickly if you go in hard with them if your tail-stock is not perfectly aligned, you just need to touch a a little point and that should be enough to drill into.

Giles


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