Machine a precise hole through solid carbide

Erin Burke

Erin Burke

KnifeMaker...ish
Joined
May 19, 2003
Messages
1,330
Hey guys,

I am considering the idea of building a carbide-faced lapping tool for pivot bushings. Is there any way to drill a relatively precise hole (say 0.257" - Letter size "F") through solid carbide (1/16"-1/8" thick)? Can this be done cleanly in a mill with some sort of diamond burr? What options exist?

Thanks in advance... Erin
 
Three letters EDM. Diamond tooling may be able to but it's not an easy process 1 don't think a diamond burr will drill well.
 
I have no idea as to what a lapping tool is but if your wanting to fasten the carbide to another piece of steel you might want to consider some type of epoxy.
 
Laps typically are not made of the hardest thing you can find laying around.

How about a piece of cast iron and some diamond lapping paste?

Dave
 
A sinker EDM will get a hole in it, I'm not sure of the accuracy. A wire EDM is precise, but you have to have a hole in it first( to feed the wire through).
 
Some of the new WEDMs can peck a hole with the end of a wire. Plunge EDM can be quite accurate.

When lapping, the lap is to be softer than the thing being lapped or the abrasive embeds in your part and cuts your lap. Though I expect you're using the carbide to hold your part and sanding the end. If that is the case, carbide is appropriate.

You may be able to find a carbide drill guide bushing that will do what you want it to do for a lot less money than a custom carbide part. Look up drill bushing at MSC.
 
Nathan the Machinist said:
Some of the new WEDMs can peck a hole with the end of a wire. Plunge EDM can be quite accurate.

When lapping, the lap is to be softer than the thing being lapped or the abrasive embeds in your part and cuts your lap. Though I expect you're using the carbide to hold your part and sanding the end. If that is the case, carbide is appropriate.

You may be able to find a carbide drill guide bushing that will do what you want it to do for a lot less money than a custom carbide part. Look up drill bushing at MSC.
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That makes a hell of a lot more sense - duh. I need to quit posting while in a cold-induced fog!

Great idea on the bushing, too. :thumbup:

Dave
 
Nathan the Machinist said:
Though I expect you're using the carbide to hold your part and sanding the end. If that is the case, carbide is appropriate.
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Yeah Nathan... that's what I'm talking about. I'll have to work on my terminology. :D I was thinking about something similar in concept to the jigs that Bill Vining has pictured in THIS THREAD... except with a carbide face to minimize wear on the tool.

Erin
 
Erin,
Another way is to purchase some Ferrotic. It is a machinable carbide about 35Rc be for heat treatment. Machine it to the shape you want and then Heat treat it. At my last job I used it a lot for wear guides. Finish hardness is about 72Rc.
Just food for thought and other applications too!!!
 
I have all the needed edm machines at work to do what you need. If I can be of any help let me know.
 
JTknives said:
I have all the needed edm machines at work to do what you need. If I can be of any help let me know.
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Wow... thanks Jarod. I'm just in the pre-design (conceptual phase) now, but when I'm ready to try a proto, I'll certainly touch bases with you. Thanks.

Erin
 
I would contact Carr-Lane and buy a carbide bushing that is the size you need and insert the bushing into a steel holder. They offer stock or custom made carbide bushings with 4 decimal place accuracy.
 
What size pivots are you folks using? I use 1/8 on my small folders and 3/16 on the large folders. MSC has barrel laps for both sizes. I buy presision stainless dowel pins and drill them for the appropriate pivot screws. I drill my blade hole and ream .001 undersize. After heat treat I lap the hole with a 400 grit compound until the pivot slips in nicely. Works quite well and gives the folder a nice smooth action.
 
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