Drilling SAK pivot holes

[jdindadell]

First post so go easy on me....

I need to enlarge a few sak tool holes from 2.2 to 2.5mm.  Will a cobalt bit work?

I can set the tools up in my mini mill, clamped square and true.  I have read that slow speed and constant firm pressure are required.  Just wondering if a cobalt bit will be a waste of time.  If so solid carbide looks like my next choice, but what style should I use?  118 or 135 deg?  The shorter screw machine style bit would be my preffered type for rigidity.  Those come in 135 deg with a split point.  Not sure if that will matter as I am just enlarging an existing hole.

Any help will be greatly appreciated.   I have read quite a lot here and have found this forum very helpful.

[jdindadell]

And a few pics of my 1st build...  Everyone loves pics!

[Syph007]

Welcome to the forum!

You do really need carbide bits to drill out the holes properly.  The point pitch doesnt matter too much as its just the outer part of the drill doing any cutting anyhow as you are widening existing holes.  Other drill bits really dont have a chance at cutting hardened steel.

If you are only needing to widen a couple of holes though some people just make do with a dremel and some conical grinding bits.  With those you just grind a bit, and test fit, then repeat.   

Cheers!

[jdindadell]

Thanks for the info Syph, I read your alox thread and it certainly spurred me on to do a few mods.

I will pick up a few bits.  Looks like either 39 or 38 wire size would be close to the 2.5mm brass rod.  I do not have a pin gauge set handy, how much slack should I leave?  It does seem like the tools are not drilled to the same size as the scales and liners, they do seem looser to me.