10V crankshaft is (IIRC) 9/32" diameter so a bit tricky to bore.

Sir Harold of Hall has a nice description of this work (I made a built up crankshaft for mine so didn't face this issue). I've used one of these jigs since though, I think I drilled and reamed it in the 4-jaw.

Neil

Edit- added Harold's link.

Edited By Neil Wyatt on 23/01/2015 21:14:04

Hi Hamish,

Long thread may gave the impression a d-bit is more complex than it actually is.

You just need to take just under half of the thickness off of a bar of the right diameter for a distance of about two diameters, then as it isn't for flat-bottomed holes, set the rest on your grinder at ten degrees and angle the d-bit at ten degrees and grind across the end to create the cutting point.

If you use silver steel you will need to harden and temper it, but is perfectly possible to grind one from an HHS toolbit (or an HSS drill blank).

Neil

Edited By Neil Wyatt on 24/01/2015 12:37:24

If you take off over half the thickness it will cut on the side which you don't want. You need to reduce it to just over half the thickness, say 10 thou over, then it will cut true to size. But, yes, it's much easier to do than describe.

Russell.

Another way is to make a tool makers reamer, either HSS, or silver steel. If the hole to be reamed is brass or aluminium, a piece of the shaft that's going to fit the hole may do OK. Cut the slope about 20*.

Ian S C