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Lapping Pivot Holes.
- Thread starter Andybrock
- Start date
- Joined
- Jul 27, 2003
- Messages
- 5,667
What I have found is that every hole is different. You need to think on your feet.
Every drill bit not identical to the next one of the same size.
Always under-drill before you ream.
Example - I have some fasteners that mic out at 1/8" - .125.
I under drilled the hole with a #31 and reamed out with 2 different PRECISION reamers that also mic out at .125.
The fastener would not go in the hole.
I had to order some .126 reamers for things to work out.
Now, maybe if I had spent some time lapping, it might have worked out.
My point is, do what you have to do for things to work.
Set your lap at its most loose setting and see if it improves things. I only lap if I need to to make things work.
Knife making just ain't all cut and dried.
Every drill bit not identical to the next one of the same size.
Always under-drill before you ream.
Example - I have some fasteners that mic out at 1/8" - .125.
I under drilled the hole with a #31 and reamed out with 2 different PRECISION reamers that also mic out at .125.
The fastener would not go in the hole.
I had to order some .126 reamers for things to work out.
Now, maybe if I had spent some time lapping, it might have worked out.
My point is, do what you have to do for things to work.
Set your lap at its most loose setting and see if it improves things. I only lap if I need to to make things work.
Knife making just ain't all cut and dried.
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
- Joined
- Aug 20, 2004
- Messages
- 37,911
I find a reamer does the trick 99 out of 100 times. Now, you may need several sizes of reamers, but one will end up doing the job just right.
Do you drill undersize, HT then ream to size with a carbide reamer?
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
- Joined
- Aug 20, 2004
- Messages
- 37,911
Usually, yes.
Things that lead to a better pivot and blade fits:
Buy all your pivots from the same source. Buy in batches that will give you enough to use for a year or so. The precision parts are a far better choice than the cheaper ones.
Pick a size for your pivot and stick with it. If you go with .1870", then get your drills and reamers accordingly. Measure the pivots when they come in and order your reamers and drills accordingly. Best choice is to use a supplier that checks their product and takes guesswork out of the equation. They often sell drill bits and reamers that fit their pivots.
I always buy drills from the same supplier I get pivots and Corby bolts, if they offer them.
Buy your reamers and pivot hole drill bits in carbide. Money spent here pays for itself.
Chuck at AKS has this note:
Our 3/16" pivots are machined to .1870 (+.0002" -0.0000"). We recommend knifemakers use a .1875" reamer. The pivot has raised shoulder of .1875" so it can be press fit into the liner.
(So, I would use a .1870" carbide drill bit for the holes.)
Measure with a good quality micrometer. A HF plastic micrometer is fine for checking stock thickness and blade height ... it is no good for checking pivots.
If possible, use a mill to drill and ream the holes.
If pivot consistency is a problem, a brass lapping tool can help. Go slow.
Make sure the two sides of the blade are parallel !!!! If they are off by more than a few thousandths, there will be alignment issues. This is why most folder makers use a surface grinder to finish the blade blanks after HT.
Practice on some scrap stock that you hardened. Drill and ream many holes until they fit right every time ... then try it with blades.
Things that lead to a better pivot and blade fits:
Buy all your pivots from the same source. Buy in batches that will give you enough to use for a year or so. The precision parts are a far better choice than the cheaper ones.
Pick a size for your pivot and stick with it. If you go with .1870", then get your drills and reamers accordingly. Measure the pivots when they come in and order your reamers and drills accordingly. Best choice is to use a supplier that checks their product and takes guesswork out of the equation. They often sell drill bits and reamers that fit their pivots.
I always buy drills from the same supplier I get pivots and Corby bolts, if they offer them.
Buy your reamers and pivot hole drill bits in carbide. Money spent here pays for itself.
Chuck at AKS has this note:
Our 3/16" pivots are machined to .1870 (+.0002" -0.0000"). We recommend knifemakers use a .1875" reamer. The pivot has raised shoulder of .1875" so it can be press fit into the liner.
(So, I would use a .1870" carbide drill bit for the holes.)
Measure with a good quality micrometer. A HF plastic micrometer is fine for checking stock thickness and blade height ... it is no good for checking pivots.
If possible, use a mill to drill and ream the holes.
If pivot consistency is a problem, a brass lapping tool can help. Go slow.
Make sure the two sides of the blade are parallel !!!! If they are off by more than a few thousandths, there will be alignment issues. This is why most folder makers use a surface grinder to finish the blade blanks after HT.
Practice on some scrap stock that you hardened. Drill and ream many holes until they fit right every time ... then try it with blades.
Thanks Stacy,
I’m in the UK so I have to buy my bushings from your side of the pond, usually K&G. I’m trying to get away from lapping, again being over here nobody sells pivot lapping tools so again have to import.