Eggascope kaliedascope

[Lyle]

I bought some of the subject kits and have turned one up. It is OK, but have a small problem with drilling the hole for the kit.
I was advised that the hole needed to be 13/16. They didn't have one but recommended a 20mm would be the go.
So got one and the hole it bores is too tight for the kit bushes and the kit parts by about 0.6mm. No big issue I just sanded out the hole until the bushes fit (a fairly snug fit).
But I thought that since the recommendation said 13/16 I bought one figureing it would be the right size.
Now the problem is that the 13/16 is actually 20.6mm which is ever so slightly larger than the kit bushes. This causes the bushes to be a sloppy fit when turning and you need to really tighten the bushes down hard to stop the job slipping. With the problem of the job being out of round after turning, giving the kit a poor fitup.

So is there anyone who knows how to 'fix' this.
Anyone else out there turning these and have this problem?
Is there an 'in between' drill bit 20.4mm????
Or do I just grin and bear it and continue to sand the hole for a good fit to the bushes?

Thanks
Lyle.

[Tim the Timber Turner]

Grind down an oversize spade bit to drill, or ream out the 20mm hole?

The sucess of reaming with an spade bit would depend on the accuracy of your tailstock alignment.

Another thought is to drill a smaller dia hole say 16mm and then make a step drill from a spade bit the required 20.6mm, then grind a 16mm step onto the bit which would follow the 16mm hole.

Depends how handy you are at metal working.

Cheers

Tim:)