Friday, February 12, 2010

Brace Yourself

Our friend Kiko is a bit of a luddite. He asked me if I could make an adapter for his bit brace so he could use 1/4" hex screwdriver bits. Being lazy I checked to see if such adapters are available and indeed they are. Lee Valley tools has them for $8.50. So Kiko ordered it. I decided to try making one anyway.

There isn't a standard for bit brace tang dimensions as far as I can tell. Easiest way to measure the taper was with my vernier protractor. All the bits I measured have different tapers.

Here's another way of measuring.

Measure twice...

or thrice.

It seemed that 10 degrees was a good average so I selected a 5 degree angle to support the work.

Then I drilled out some 1/2" tool steel to be a press fit on the hex circle of a magnetic bit holder.

And reamed it for a slip fit on the outside diameter of the holder for about 1/4".

Then I pressed the holder into the steel.

I knew it wouldn't run true so I checked it against an indicator and whacked it to get it within about .005" which is way more precise than needed.

I then turned a taper at the other end.

I set up the mill with the angle clamped in the vise.

Then put a 5C collet block in the vise against a stop.

It was a simple matter of milling a flat, turning the block 90 degrees and milling another flat.

About halfway done.

I then turned down the shank so it was smaller in diameter than the tapered section.

And it works.

I figured that since I had the mill and lathe set up I'd make another adapter.

Turning the other end 3/8"
I used a die to make 3/8"-24 threads. The tailstock chuck keeps things square

And a drill chuck threads right on.

More milling...

And turning...

And I have a nice adapter.

I gave them to Kiko and he gave me a wooden spoon.


Woomat said...

Hi Nick

I read your last post with interest as I have a similar problem of needing to hold brace bits in a normal drill chuck. I don't what to cut the brace tang's off yet. Any ideas?

Nick Carter said...

If you don't want to cut the tang off? Hmmm...I'm not sure if there's a way to do that. Possibly you could find another bit brace and remove the chuck & shaft and adapt a shank to it that will fit your drill chuck? The tang is usually around 1/2" square so any adapter you put around it means it will only fit in the larger drill chucks.