12-28-2016, 01:14 PM
I have a set of cobalt twist drills I bought for a 'good' price a number of years ago. I've come to the conclusion that the 1/8", 3/16", 1/4", 3/8" and 1/2" were probably properly heat treated but that the rest may not have been. Evidence: those are sharp and stay sharp through long use in 'mild steel'. When resharpened, they last.
The rest, however, seem to dull at the slightest use in any ferrous metal. When resharpened, they last through maybe 1/8" and then dull again.
Can anyone recommend a good set of twist drills, preferably cobalt but HSS okay, that's not one of the $230 sets you see industrial supply sites?
The rest, however, seem to dull at the slightest use in any ferrous metal. When resharpened, they last through maybe 1/8" and then dull again.
Can anyone recommend a good set of twist drills, preferably cobalt but HSS okay, that's not one of the $230 sets you see industrial supply sites?
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