Burning out drill bits left and right

drilling problems...
I work in a machine shop, a few tips try using motor oil as opposed to regular cutting/drilling oil, it stands up to the heat beter and flows chip away from the tip easier. try to find cobalt tipped/cobalt coated bits I dunno why they work better but they do, also you might try drilling several holes building up to your finished size as opposed to boring the finished hole all at one shot. Good luck

:confused:
 
i think spilt point cobalts are best, they dont walk as easy and stay cooler becuase of the the 4 slots. i use cobalts, drill before heat treat and have no trouble drilling carbon or stainless steels, but D-2 is still a pain in the @ss and so is BG-42, i donno what to do about them. they're my two favorites to use. oh btw i use cutting oil too.
 
Everyone is saying great stuff here. Cobalt bits rule :) But I think there is another issue at hand. I know from personal experience, when I buy 1095 or 1084, more often than not, it is NOT fully annealed, the outer third is fairly soft, but that middle third is rock hard, killing hacksaw blades, drill bits, bandsaw blades, etc. This is a frusturating problem, esp when u burn out 2 cobalt bits trying to drill 1 hole. it happened to me. I think we need to start stressing steel quality to whoever supplies the steel to the people and the knife supply houses so they know we dont like steel that is hard in the middle. TKS rockwell tested their steel after i called them about this problem, they said it was 10 rockwell. But how deep does the test go? if it tests the surface, how can they be sure it is annealed fully???
 
Taz,
I had the same experience with some 1084 I bought in Oregon from a reputable supplier. I only do stock removal at this time, and also suspect that the steel is all ready somewhat hardened near the center, as delivered to my door. I tried to be very careful with my drilling and still had problems. I think some of the spot annealing techniques mentioned here may need to be put to use. I also bought some 5160, but haven't tried to drill it yet.
 
hy guys,

I recently read a book on the forging of tools (it was called 'the modern blacksmith' or something similar. There i found an interesting trick so drill holes in a hardened sawblade. I haven't tried it yet, so i don't know what it's worth. The author suggests cutting the head of a nail, put the nail in the drill press and drill on the spot of the sawblade where you want the hole. The friction will heat the blade and will locally anneal it, allowing for easy drilling with a regular bit afterwards. Any remarks?

What puzzles me is the fact that, as far as i remember, annealing has to do with the rate of cooling (being rather slow in order to soften the steel). So i would think it's necessary to cool down the blade very slowly . Or is this heating just enough to thouroughly temper the sawblade to a 'drillable' temper? Comments and thoughts are welcome...
 
Tim,
You are right, to anneal you bring to a certain temp and slow cool in a furnace, to normalize you heat to critical or a shade above and air cool.I normalize 4 times after I forge and then slow heat to critical the first time I quench.(quench 3 times and only edge quench)
I very seldom have any problems drilling and every blade I've tested has bent beyond 90 degrees with out a crack or a break, and rebounded
to about 25 or 30 degrees when released.I do believe that the extra normalizing cycle really makes the different and saves on sanding belts.
 
hy boxton,

Is it possible you forgot to mention the annealing? This is what i do when forging 5160 and o1 (i have to admit only having some knowledge with these steels, played around a bit with 52100, but am not a specialist):

1) forge into shape
2) normalize 3 times (heating to critical temp and aircooling)
3) annealing 3 times (heating to critical temp, cooling in wood ashes)
4) rough grinding
5) edge quench (3 times) in a mixture of fat and parafin
6) tempering 3 times at 200°C (2h a time)
7) final grinding and polishing (a leave my blades thick before heattreat, decarburised steel is removed with final grinding)

see ya,

tim
 
Hi Tim

No I don't anneal, heat to critical 4 times and air cool (normalize)
just be super careful not to over heat.I was told by a mastersmith years ago in order to anneal properly you need to control the heat in a furnace when cooling so I just air cool, the refinement of the grain after forging is more important.Anyway my steel is soft and easy to drill.
It works for me, what I do might sound stupid to others but we all have are own technics and opinions. Have a good one.
 
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