I do have a small (up to 1/4") broach cutting set purchased on a whim "that I might just need that some day" and I have used it a few times but most of the time I need something bigger and a "custom sized" single use broach can be made very cheaply in an hour or so with a piece of appropriately sized high speed steel cutter blank, a bench grinder or sander to cut the initial side angle and a Dremmel to cut 3 or 4 biting teeth. Incidentals needed are a bit of slotted "guide" shafting and a hyd press to push it through.
The "biting teeth" can be, but don't need to be relieved deep enough to contain all the cuttings in one push as most workpieces we have to slot can be turned over. The broach can be pushed a bit until you think the "relief" area is full, then turned over, pushed out, cleaned, turn back over and start again...it works, I've done it a couple of times. I use a shop 20 ton press now but the first time I did this I used 2 fire bricks under the workpiece for clearance for the broach to be pushed into and a 4 ton bottle jack for a power source. I set the whole issue up under a 1 ton pickup bumper for a "pressure point" anchor....sure was a mickey-mouse set-up but it worked.
Actually home made "single point" broaches have been used by "home shop, kitchen table gunsmiths for years (since the 1840's that I know of) to cut rifling in gun barrels and if they could do it with their equipment that far back we should be able to do just as good a job with ours now. Two of the best "cut rifling" barrel makers in the world right now are both in Ab. and both use their own home-built rifling cutters.
It sure is interesting how a visit to Ron's grainery/shop 30 years ago could solve a problem a couple years ago...I remember thinking, when I built the first broach cutter I needed, that if Ron can cut rifling that will hit a postage stamp at 500 yrds then I sure as he!! can cut a groove to turn a gear hub.
