Ed Tipton Posted April 8, 2009 Share Posted April 8, 2009 I recently had quite a problem with drilling the pin holes in the full tang of a knife. I had annealed the blade, and it was softened, but when I tried to drill out the pin holes, it work hardened so badly that I ruined two drills before getting the holes all the way through the tang. I thought about drilling the holes when the blade is still hot, but I am concerned about the holes shrinking too much. I am sure others have had similar problems and I'd like to know how this was accomplished. I drilled them on a DP, but I admit that I was not using a lot of pressure. Would drilling the holes more aggressively have prevented the hardening? This was done on a kitchen knife where I was using tension pins for the handles. Quote Link to comment Share on other sites More sharing options...
MRobb Posted April 8, 2009 Share Posted April 8, 2009 What speed were you drilling at? If you drill too fast your bits heat up too much and get dull quick. Adding a little cutting oil will help also. Quote Link to comment Share on other sites More sharing options...
cardoso5fr Posted April 8, 2009 Share Posted April 8, 2009 There is various reason possible about the problem to drill the hole. 1 Your drill bit was old, or have cut something as titanium. 2 The speed of drilling is too fast as it has been said by Mrobb 2 The annealing was too fast and the heart of the steel piece is always more or less hard. 3 You have used a steel as O2 which is almost an air hardened steel. If the annealing is faster than 20 Quote Link to comment Share on other sites More sharing options...
Dodge Posted April 8, 2009 Share Posted April 8, 2009 Proper feed and speed is essential. Generally, the smaller the bit the faster the speed and feed. I used to run drills after I could no longer stand to weld. A lot of the drilling was on CNC, but much by hand at a drill press. As a guide, we drilled 1/2" holes in mild steel, dry at 500 rpm, 7/32" at 900 - 1000 rpm. (Side Note: we had a special internally cooled 3/8" bit that we ran on the CNC at 3400 rpm and a rediculously fast speed. Through 2" plate in about 4 seconds ) The secret to hand feeding on a drill press is getting a feel for the cut. Let the machine do the work. You will burn up more drills with too light of a feed than too fast of an RPM, but you can't hang on the feed handle either. Too heavy a feed is bad but in my experience, too light is worse. AND as has been mentioned before, a cutting fluid such as cutting oil, or water soluable is never a bad idea. Quote Link to comment Share on other sites More sharing options...
chrisfrick Posted April 8, 2009 Share Posted April 8, 2009 What kind of drill were you using? HSS, Cobalt, Ti coated, etc.? I have had very, very good results with Cobalt and that's pretty much the only thing I use now. Aside from that, Dodge hit it on the head--use the proper speed and feed for the drill and the material and a cutting lube helps too. Quote Link to comment Share on other sites More sharing options...
jsurgeson Posted April 8, 2009 Share Posted April 8, 2009 Couple times I have hardened a blade and by accident left out one of the holes needed for something or other. Drilling a hardened piece of N690 is all but impossible, did not have any fancy special bits, so did this. Took a standard masonry bit with tungsten insert of the correct diameter, ground a edge as close to a standard edge as I could, and used that. No good for very accurate drilling but with semi decent edge, correct pressure, right speed, you will drill it and it wont burn out, might do a bit of screaming but it will work. Quote Link to comment Share on other sites More sharing options...
Don A Posted April 9, 2009 Share Posted April 9, 2009 I found a bit made by Irwin that was not carbide, but had a carbide insert (basically a masonry bit, as well). I was able to drill through un-annealed planer blades with it. But still mind your speed and lube. Quote Link to comment Share on other sites More sharing options...
MattBower Posted April 9, 2009 Share Posted April 9, 2009 What sort of steel are you using, and exactly how did you anneal it? Quote Link to comment Share on other sites More sharing options...
panzertank27 Posted April 9, 2009 Share Posted April 9, 2009 new to blade smithing but cunstruction half my life. ive found you get what you pay for with bits .cobolt makita seems to be the best ive used and of course proper slow speed and i use 3 in 1 oil as lube. ive used this on unannealed leaf spring slow and careful. oh and if drilling big holes start with a smaller diameter and progress up. Quote Link to comment Share on other sites More sharing options...
viking-sword Posted April 9, 2009 Share Posted April 9, 2009 I used to experience the same problems but not so much anymore as I slowed down my pace of doing things just a bit. I used to just step up and grab a bit, chuck it up, and drill away, though I did make sure my speed of press was correct. Now , I take the time and examine a drill bit carefully each time I use one, making sure the angles are even and as sharp as can be. I also like to do a quick stoning and polish on the cutting edge, ( I usually sharpen with a drill doctor, which leaves a course grind), so I stone, using the same pitch and angle, and smooth out the course surface, and then put it on a finishing stone so that it's almost polished and man do they cut well. It's almost theraputic watching the bit do the very best it can. Aside frome that, make sure your tang is level, and , if your still buning up bits on an even semi soft tang then you need to slow the speed of the press down. It's important to go by the proper feed and speed tables. Thanks for letting me babble on, Wes Quote Link to comment Share on other sites More sharing options...
Dodge Posted April 9, 2009 Share Posted April 9, 2009 ... Now , I take the time and examine a drill bit carefully each time I use one, making sure the angles are even and as sharp as can be. I also like to do a quick stoning and polish on the cutting edge, ( I usually sharpen with a drill doctor, which leaves a course grind), so I stone, using the same pitch and angle, and smooth out the course surface, and then put it on a finishing stone so that it's almost polished and man do they cut well. It's almost theraputic watching the bit do the very best it can. Aside frome that, make sure your tang is level, and , if your still buning up bits on an even semi soft tang then you need to slow the speed of the press down. It's important to go by the proper feed and speed tables. Thanks for letting me babble on, Wes I agree. Sharp bits just make life easier :D Quote Link to comment Share on other sites More sharing options...
nitewatchman Posted April 11, 2009 Share Posted April 11, 2009 I have had good results spot annealing the area where a hole is to be drilled on hardened metal. I do this by shaping the end of a carbon arc gouge rod to a flat point of the diameter I want to anneal. The metal is then polished so that the tempering temperature and spread can be judged by color. I then firmly ground the metal to a battery jumper cable clamp with a piece of copper between the clamp and part and place the carbon in the other clamp. Place the carbon firmly against the metal and have a helper attach the cables to a 12volt truck battery. The metal under the carbon point will rapidly heat likely turning red directly under the point. The helper can throttle the heat by removing the clamp from the battery to control the heat. Watch the color change areound the carbon. This can also be done without a helper if the carbon can be clamped against the metal but resist the urge to place the energized carbon against the metal. It will likely burn a chunk of the metal out. I have used this method to spot anneal hard rifle receivers so I could drill and tap for scope mounts. Quote Link to comment Share on other sites More sharing options...
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