D bits

[firebird]

Hi

How do you make 'D' bits for making flat bottomed holes? Do you bore out with the 'D' bit or drill first and then flaten it? John has already explained the art of hardening silver steel in the tips and tricks section.

Cheers

 

[Hilmar]

Fb,
if I had your E-Mail address I could send you a page wit instruction on how to make on.
D bits are not for making flat bottom hols. They are more for making straight and precise holes.
Hilmar

 

[gilessim]

you can make a sort of d-bit for flat bottomed holes , depending that they are not too deep, but they need to be made from a smaller diameter than the hole size ,just turn a slight taper, say about 5° on the end, grind the end square with the taper and set the taper over paralell with the workpiece with as little as possible sticking out of the toolpost and go in, I've used this on brass and ally , but with steel it would probably chatter, but as I said, this really only works for fairly shallow holes, I hope you can visualize what I'm on about...Giles P.S. yes ,in this case you would drill out to near size first

 

[Shadow]

Redrawn from George Thomas' book "Model Engineer's Workshop",page 94