sharpening carbide?

Charlie Mike

Charlie Mike

Sober since 1-7-14 (still a Paranoid Nutjob)
Knifemaker / Craftsman / Service Provider
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Nov 1, 2000
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I've finally dulled my 3/16" fluted carbide drill bit. Is there any way to sharpen it back to health?
 
Having worked for Kennemetal...it takes a diamond stone/wheel to sharpen carbide. (be it nickel/tantalum/titanium/silicon or tungsten) Its equally grievous to polish...albeit diamond compound is easier to come by.
 
It's prolly best to buy a new one I think.
 
Invest a lot of time and talk to a few old timers who have been sharpening drill bits for years and understand the dynamics and you will be well ahead of the game in a few years in the money you save on the purchase of new bits.
 
drill-doctor 750 has a diamond wheel and will sharpen carbide. So long as your bit is 118 or 135deg.
 
cm, send me a pm if you dont find someone to sharpen it. i have a 1/4" carbide drill i chip every now and then i have to resharpen.
 
This is one reason why I suggest folks avoid carbide drill bits. For most people, they don't stay sharp any longer than a good HSS bit (it requires a rigid setup with controlled feed to avoid chipping them), they're too expensive to just throw away, and due to their high hardness and chippy nature they're hard to sharpen. I usually only use carbide drills in abrasive applications like plastic.
 
i tried a good cobalt drill set up in the mill to drill a hole in that 1075 john deere steel i use and it never made it a 1/16" before going dull so carbide was my only choice.
 
I'm with Nathan here. Yes they can be sharpened but most do not have the right tool to actually get the benefit from a carbide drill. When I need to put a hole in hardened steel I use a carbide endmill. They are not that expensive and cut through a hard piece of knife steel really well. But you still need a rigid set up. A drill press wont cut it. You will break the endmill if it is not rigid enough. If you plan properly you should never need to drill hardened steel. Good HSS will drill most any steel if you use the proper speed/feed and lube. Cobalt is good but I have not been able to justify the additional expense over the HSS.
 
The mechanic that taught he how to sharpen carbide bits used a soft wheel meant for sharpening carbide drills, it did not take many carbide bits to eat one of those grinding wheels and he sharpened them free hand, the ones he sharpened always cut better then the bits did when new.

Nathan: in your experience are stress raisers emanating from round holes drilled in soft steel that will be hardened later greater or lesser than those drilled in hard steel?
 
Ed, I have no idea.

Just speculating here, but I would think the combination of higher cutting forces and lower ductility seen when drilling hardened steel would be more likely to generate small cracks.

Residual stress caused by small localized yielding caused by cutting forces in a soft steel would be erased in heat treat.



+1 on using a carbide endmill to put holes in hard steel. I did this a while ago to prove it could be done. Carbide endmill and a fine helical toolpath to get around the "dead zone" in the center of the cut. Notice the fine finish and the healthy cutter.

hard3.jpg


I used this technique a few days ago to remove a broken tap (reduced to fine powder) from my subplate. (Machine tapping with a hand tap = not my best idea...)
 
Unless you have a wheel to sharpen carbide and the skill to sharpen it, I'd recommended saving it and buying a new on. Scrap carbide brings good money.
 
Nathan,
I always keep small .093 or .125 carbide end mills just for broken taps. Sometimes it's quicker than the tap zapper or a drop EDM. +1 on the helical.
 
What do you mean, you don't sit there with a tini set of needle nose pliers trying to untwist the tap? Balderdash!
Nathan the Machinist said:
Ed, I have no idea.

Just speculating here, but I would think the combination of higher cutting forces and lower ductility seen when drilling hardened steel would be more likely to generate small cracks.

Residual stress caused by small localized yielding caused by cutting forces in a soft steel would be erased in heat treat.



+1 on using a carbide endmill to put holes in hard steel. I did this a while ago to prove it could be done. Carbide endmill and a fine helical toolpath to get around the "dead zone" in the center of the cut. Notice the fine finish and the healthy cutter.

hard3.jpg


I used this technique a few days ago to remove a broken tap (reduced to fine powder) from my subplate. (Machine tapping with a hand tap = not my best idea...)
Click to expand...

JBS TOOLMAKER said:
Nathan,
I always keep small .093 or .125 carbide end mills just for broken taps. Sometimes it's quicker than the tap zapper or a drop EDM. +1 on the helical.
Click to expand...
 
kungfumo said:
What do you mean, you don't sit there with a tini set of needle nose pliers trying to untwist the tap? Balderdash!
Click to expand...

Well of course I did. But honestly, in the history of tapping holes, has that ever worked? Ever? I also did the old tap on it with a punch thing. But that never works either. Sometimes if you can get pliers on you can coax it out. And I could get pliers on it. But no dice.
 
Well, I guess I've just been very lucky. I have used a lot of carbide bits. I have found them excellent for the applications they are designed for. They definitely do not work well in soft metals. As well I do sharpen them free hand but then only use them for holes that do not require accuracy. There aren't many of those needed are there. I find a brand called Ford to be reliable. Frank
 
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