Cutting a keyway with a hacksaw

[Mike BR]

I worked out a new (to me, at least) way to cut a wide kerf with a hacksaw -- in this case to cut an internal keyway in a gear hub.

First, I ganged two blades in the saw and cut a kerf to the appropriate depth.  Then I took one of the blades out and reinstalled it upside-down (teeth toward the saw frame).  I found a piece of sheet metal a little thinner than a hacksaw blade, cut an narrow shim, and placed it against one side of the kerf.  Then I put the saw back in the kerf, with the reversed blade against the shim.

The shim forced the live blade to cut beyond the edge of the existing cut; the reversed blade rode along the shim without destroying it.  I went to a couple of progressively thicker shims until I got the kerf thickness I needed.

It didn't do as neat a job as a keyway broach (If I could afford one of those), but I cut a keyway in about 10 minutes that I think would have taken close to an hour if I had to use files small enough to fit in the bore.

[Frosty]

That'll work. Is a broach that hard to make?

Frosty The Lucky.

[JHCC]

Mike, could you show us some photos or a sketch?

[Mike BR]

 

I can't seem to find my earlier post -- hopefully that isn't a sign.  But here are photos of:  The ganged blades in the saw; the first kerf; the saw with one blade reversed; the saw with one blade reversed in the cut with a shim; and a shot of a partially completed second cut, where you can hopefully see how the tooth-down blade is widening the kerf on the right-hand side.

 

Sorry for duplicate photos and poor organization -- can't figure out how to fix that.

Mod note: we cleaned it up for you

 

[Scott NC]

  I learned a new technique.  Thank you.  This should also be in the "Tips-N-Tricks" section.

 

Mod note: Moved. Thanks for the tip.

[Frosty]

Pretty slick Mike, well done. I love adding new stuff to my mental tool kit. 

Frosty The Lucky.