Drilling pivot holes

R

Random Mutant

Joined
Oct 18, 2001
Messages
59
1. On a precision folder, do you drill the pivot hole before or after heat treat? I would imagine that drilling before heat treat would mess up the hole with scale, or change the dimesions slightly. Drilling after heat treat would require tempering the area at a higher temp.(no big deal w/ a torch).
2. How hard should the pivot area be?
3. Do you drill pin holes in fixed blades before or after heat treat? I would think they would require less accuracy, therfore before would be ok.
 
There is no reason not to drill beforehand. If you are sending the blade out to heat treat to someone like Paul Bos it will come back with practically no scale on it. He uses an inert atmosphere in his ovens and wraps the blades in SS foil to minimize scale formation. If you're doing it yourself, you still don't lose very much even in an oil quench. In short, don't worry about it and save yourself the money for carbide bits and the risk of screwing up the hardening with your selective tempering.
 
On a percision folder you cannot just drill a hole! It has to be drilled slightly undersize and then precision reamed, a drill will not drill a round hole, espically if it is a little dull. all holes in blades are drilled before heat treat! And fixed blade holes are just as precision as a folder blade, you can guess where to put it, but they have to be equally spaced and countersunk. The holes are not affected by scale, you just ream them again and the scale is removed. If you tried to temper a folder blade to drill the hole that area would be softer than the rest of the blade and wear faster on any type of folder, liner lock, slipjoint or lockback.
Hope this helps,
Chuck
 
A word of caution: If it can go wrong....it will!
The pivot hole properly drilled and reamed and having both sides of the blade parallel and 90 degrees to the pivot hole are the most important factor in making it work right
 
Thanks for the replies.
When I spoke of less accuracy required in fixed blade holes, I was thinking of size, not placement. I figured that a pin would expand during peening, while a pivot wouldn't.
I was considering trying a folder, but with my meager shop, maybe I will stick to fixed blades for now. (Reamer? I figured a drill bit would be good enough!)
The more I learn, the more respect I have for you guys.
BTW, I have been doing my own heat treat with a torch and some firebricks, small blades only for now. I would like to try some bigger blades and send them out when my skills get up to snuff.
 
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