Blade straightening question

Stuart Davenport Knives said:
I really need to make myself one of those carbide tipped hammers.

Jason, one thing I noticed about yours, the carbide end mill looks flatter than others I have seen that have a more rounded tip to them! But it got the job done!
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I don't remember exactly , but it was a video about a knife factory. I'm 100% sure that they used a ball shape.
 
Stuart Davenport Knives said:
I really need to make myself one of those carbide tipped hammers.

Jason, one thing I noticed about yours, the carbide end mill looks flatter than others I have seen that have a more rounded tip to them! But it got the job done!
Click to expand...
Bc mine started as a 3/16 end mill. I chucked in in the drill press and used a diamond stone to round it off some. I also experimented with hitting on the corners vs the domed flat and can't tell a difference yet.
 
JT who used to do heat treating before family took president was perfecting using a sewing machine to straighten blades. I wish he was still on here. Awesome dude. I miss his informative posts. Think about the force of a sewing machine dinging a metal blade. THAT'S all it takes. I successfully straighten blades with tiny taps. Yes it leaves SMALL dings that are easily grind off in final grinds to make it a blade.
 
I have used a few different straightening hammers. My current favorite uses an Ultra-Hard C2 Tungsten Carbide Ball 3/8" Diameter, the ball can reasonably be purchased from McMaster and then inserted into the head of a peening hammer.
 
Seedy Lot said:
I would like to say that blanks are always flat in my world but obviously I had to persuade a few of yours to straighten up.
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I'm a big believer in the end justifies the means..... :D
 
Be really careful bending blades to straighten them if you don’t know the hardness. Under 60rc your reasonably safe but thickness also plays a role as well. All we use is surface peening to straighten blades and 99.999% of the time it solves the problem. There have been a few that I had to straighten using “3 pins and the vice” but thy where San-Mia with a soft jacket. If your using a forge to heat treat the hardness in the blade could have a large variation from tip to tang. But most carbon steel blades if you clamp stright when you put it in for the first temper it will come out straight. After the first temper your going to have to counter bend it with pins, pennies exc to get it to come out stright. But that first temper is like magic if you can get it straight then temper it at or above 400°.
 
I always read about the carbide tipped hammer....but i have concerns in terms of stress introduces into the hardened blade. In fact i have cracked 4 blades using such a device...3 blades probably because i was hammering the thin edge....but 1 blade cracked at the tang...so it certainly seems to be not as harmless as one would think. What are ypur experiences over time?
 
I have not had an issue since I went to a 3/8 tungsten carbide ball peening hammer and have used it on probably 50 blades.

When I was using a smaller diameter tc rod set into a hammer I had 2 issues peening a blade straight and both cases it was striking to close to the spine and since the peening rod was small in diameter it was making a much deeper dimple.
 
the.flying.gearman said:
I always read about the carbide tipped hammer....but i have concerns in terms of stress introduces into the hardened blade. In fact i have cracked 4 blades using such a device...3 blades probably because i was hammering the thin edge....but 1 blade cracked at the tang...so it certainly seems to be not as harmless as one would think. What are ypur experiences over time?
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I use a carbide chisel or carbide tip hammer regularly, for several years now with great success
Only cracked a blade one which was aeb-l and because I was trying to correct an area that was too thin, and I was tired and frustrated,

I'd say the details matter...what kind of steel? how thin was your edge ? how hard are you hammering?

for me It's a proven tool :)
 
the.flying.gearman said:
I always read about the carbide tipped hammer....but i have concerns in terms of stress introduces into the hardened blade. In fact i have cracked 4 blades using such a device...3 blades probably because i was hammering the thin edge....but 1 blade cracked at the tang...so it certainly seems to be not as harmless as one would think. What are ypur experiences over time?
Click to expand...
What are you laying the blade on to hammer? I cracked a blade when laying blade on anvil. Now I put wood under blade using 3/8" carbide ball and haven't had any issues. Don't hit too hard, just hard enough to leave small dimples. Don't try to straighten with 4 or 5 blows, use many small dimples.
 
I've done enough straightening now that I feel comfortable commenting. I always make sure I do one temper cycle before straightening. So far I've had success with a combination of peening with a carbide tipped masonry bit (yeah, I'm a cheapskate) and slightly overcorrecting with shims and clamps in subsequent tempering cycles. The latter can try your patience, but if you're persistent and creative it can work.
 
Guess i was hitting too close to the cutting edge or too hard when i cracked the tang. Will try wood but not sure if the anvil was causing or contributing to the cracks
 
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