The Folding Knife (& Switchblade) Forum The materials, techniques and the designing of folding knives. |
12-12-2012, 07:30 PM
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Steel Addict
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stainless steel pivot pin on slip-joint
I'm having trouble making stainless pivot pins disappear in stainless bolster on my slipjoints. I've practiced quite a bit, and can hit the pin hard enough to fill the hole. But when pinning a knife, I have to smack the pin so hard to fill the hole that the knife freezes up. Not totally, but it really messes up the action. I do use a tapered reamer to prepare the hole. I even tried annealing 416 pin stock - I don't think it did anything. Any advice?
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12-12-2012, 08:46 PM
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there is a fine line between tap tap tap... ah just right, and tap tap tap oh horse apples!!
there are also other considerations. you say you can hit the pin hard enough to fill the hole. are you "penning" the pin, or "upsetting the pin? if your tapping the pin with the round end of the hammer in a circle path around the outer edge and thus moving the metal around, that's penning as i understand it. If your hitting the pin with the flat part of the hammer straight down, that's "upsetting" the pin. upsetting makes the pin swell and get tight in the hole. that can help in a loose fit, but you have to be very careful about doing it.
also... how long is your pin before your start? you may not be leaving enough pin to do the job.
Erik
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12-12-2012, 10:20 PM
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I'm trying to hammer around the edge to create a head. Then one firm smack straight down on the pin head to tighten it.
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12-12-2012, 10:36 PM
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my guess is the last smack is where your getting in trouble. the hammering around the edge is good and done right will suck the liners together. the last smack is not only flattening the head of the domed pin, but swelling it too. try leaving the last smack off and maybe work just a bit more with the penning.
Erik
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12-12-2012, 11:01 PM
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here is a short video on pinning, show some of the basics.
Erik
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12-13-2012, 09:12 AM
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Quote:
Originally Posted by rebglass
I'm having trouble making stainless pivot pins disappear in stainless bolster on my slipjoints. I've practiced quite a bit, and can hit the pin hard enough to fill the hole. But when pinning a knife, I have to smack the pin so hard to fill the hole that the knife freezes up. Not totally, but it really messes up the action. I do use a tapered reamer to prepare the hole. I even tried annealing 416 pin stock - I don't think it did anything. Any advice?
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Hi, Reb.
I've moved from using a tapered reamer to using a drill just one size larger at the top of the hole, maybe 1/16" or so deep into the bolster. For instance if you use a 3/32" pin, use a #41 drill at the top.
Leave only 1/2 a pin diameter showing on each side. Longer pins may bend.
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12-13-2012, 09:24 AM
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Quote:
Originally Posted by Don Robinson
Hi, Reb.
I've moved from using a tapered reamer to using a drill just one size larger at the top of the hole, maybe 1/16" or so deep into the bolster. For instance if you use a 3/32" pin, use a #41 drill at the top.
Leave only 1/2 a pin diameter showing on each side. Longer pins may bend.
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I'll try anything you recommend, Don, but I'm afraid of not being able to swell that hard stainless pin that much.
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12-13-2012, 09:44 AM
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416 isn't that hard. just tap, tap, tap.
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12-13-2012, 09:50 AM
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As you peen, keep moving the blade. You'll find that each series of peens tightens the joint. When you feel the blade tighten without any play, That's when you stop and clean up the head on the grinder. If the edge still shows, very easily tap around the edges of the pin with the ball end of the hammer (1/4 lb.)until the edges disappear. This won't usually tighten the pin, it simply blends the edges of the hole with the pin material.
Use a heavy solid steel anvil of some kind to back up the hammer blows.
Last edited by Don Robinson; 12-13-2012 at 02:47 PM.
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12-13-2012, 03:04 PM
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Quote:
Originally Posted by rebglass
I'll try anything you recommend, Don, but I'm afraid of not being able to swell that hard stainless pin that much.
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The difference in size is only about .002", Reb. Easy to peen. You have to look real hard to see it in the top of the hole.
3/32" = 0.0937
#41 = 0.0960
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12-13-2012, 05:17 PM
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Quote:
Originally Posted by Don Robinson
As you peen, keep moving the blade. You'll find that each series of peens tightens the joint. When you feel the blade tighten without any play, That's when you stop and clean up the head on the grinder. If the edge still shows, very easily tap around the edges of the pin with the ball end of the hammer (1/4 lb.)until the edges disappear. This won't usually tighten the pin, it simply blends the edges of the hole with the pin material.
Use a heavy solid steel anvil of some kind to back up the hammer blows.
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I'll keep trying. That last bit - ball peening after head has been ground off - may do the trick.
Thanks for the help.
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12-13-2012, 05:18 PM
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Quote:
Originally Posted by Don Robinson
As you peen, keep moving the blade. You'll find that each series of peens tightens the joint. When you feel the blade tighten without any play, That's when you stop and clean up the head on the grinder. If the edge still shows, very easily tap around the edges of the pin with the ball end of the hammer (1/4 lb.)until the edges disappear. This won't usually tighten the pin, it simply blends the edges of the hole with the pin material.
Use a heavy solid steel anvil of some kind to back up the hammer blows.
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One more thing. Do you use shim stock between blade and liner when peening? I do (.004), with blade in open position.
Rebecca
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12-13-2012, 07:18 PM
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It's a good idea to use a shim,but I don't bother. If the blade gets too tight I just drive the pin down hard on each side using a punch until it loosens.
Yes, use a shim. It also helps to torque the blade and handle as hard as you can with your hands.
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12-13-2012, 07:22 PM
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Quote:
Originally Posted by rebglass
I'll keep trying. That last bit - ball peening after head has been ground off - may do the trick.
Thanks for the help.
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If you haven't been doing that, It's probably why you had a problem. It's nearly always necessary. Often I have to repeat peening the edges of the pin/hole and regrinding a few times before the edges disappear.
I hope this helps.
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12-15-2012, 07:23 AM
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I've been told to have the blade in the half open position with the shim stock when peening. You have more support with the liner material to keep everything even.
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advice, anvil, back, bee, blade, drill, easy, edge, flat, hammer, handle, knife, making, material, pinning, pins, pivot, stainless steel, steel, video |
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