Tiny-a$$ Counterbores?

Erin Burke

Erin Burke

KnifeMaker...ish
Joined
May 19, 2003
Messages
1,330
Does anyone know whether it is possible to get a counterbore with a cutter diameter of 1/8" and a pilot diameter of 3/32"? I can't find anything that small on MSC, Enco or McMaster-Carr. Right now I am just eye-balling them in with a 1/8" end mill.
Erin
 
Maybe a single end drill mill would do the job?
Drill-Mill-2NHF6_AS01.JPG
 
I make them all the time for seating screws. Just take a drill of the desired size and chuck it in a drill press/flex shaft/mill and apply a diamond file to the lower part. It should take less than a minute.
After the pilot is shaped, Put the drill bit in a in vise and use a small diamond file to set the cutting edge by hand.
Knifekits sells them pre-made for drilling screw seats in handle material.
 
Wow, thanks for all of the responses.

delbert ealy said:
Take a 1/8" bit and make one yourself, 2 or 3 minutes with the grinder should do it.
Click to expand...

A 1/8" bit seems fairly small to shape on my belt grinder accurately. Would you mind sharing your technique for this? I'm a little slow, so photos or sketches would go a long way in helping me to grasp how to do this.

melsdad said:
Are you doing this on a milling machine, or a drill press?
Click to expand...

I'm using as small Sieg X3 benchtop mill. The mill is equipped with 3-axis DROs, so normally what I do is drill all the appropriate holes (w/ XY coords), then go back and lay down the countersinks with end mills. This works OK, but it seems like there can be a couple of 0.001" variance when switching from drilling (w/ chuck, locked Z axis and unlocked quill operation) and milling (w/ collets, locked quill and unlocked hand-wheel control of Z depth of cut). I've started using piloted counterbores for my larger holes (1/4" & 3/16") and they have been really slick. I'd like to be able to do the same for 1/8".

bladsmth said:
I make them all the time for seating screws. Just take a drill of the desired size and chuck it in a drill press/flex shaft/mill and apply a diamond file to the lower part. It should take less than a minute.
After the pilot is shaped, Put the drill bit in a in vise and use a small diamond file to set the cutting edge by hand.
Knifekits sells them pre-made for drilling screw seats in handle material.
Click to expand...

I've heard of folks making their own, but I can't picture in my head how to set a 0.015625" cutting edge by hand (0.015625" being half the difference between 1/8" & 3/32"). I guess I'll need to pull out the magnifier and give it a try...

Erin
 
Put the drill in your collet and a diamond file or "stone" in your vise. Turn the mill and run it by the diamond file on the long axis, keep making passes untill you have what you want.
 
ib2v4u said:
Put the drill in your collet and a diamond file or "stone" in your vise. Turn the mill and run it by the diamond file on the long axis, keep making passes untill you have what you want.
Click to expand...

Thanks Jim. I see how that takes down the diameter of the pilot to the desired dimensions, but doesn't that leave the cutting edge of the larger-diameter counterbore essentially flat. I guess I'm just confused how to dress the newly created cutting edge so that it actually cuts. It sounds like a lot of folks have done it successfully, so I'm probably making things more complicated than they need to be. Thanks again.
 
Erin Burke said:
Thanks Jim. I see how that takes down the diameter of the pilot to the desired dimensions, but doesn't that leave the cutting edge of the larger-diameter counterbore essentially flat. I guess I'm just confused how to dress the newly created cutting edge so that it actually cuts. It sounds like a lot of folks have done it successfully, so I'm probably making things more complicated than they need to be. Thanks again.
Click to expand...

Erin,
Since you will be reducing the diameter of the bit, the cutting edge at the tip will not be affected, the only thing you will need to be careful of is getting the corner sharp, that will become the cutting edge and it will act like a 2 flute end mill. The ground portion will not have to do any cutting.
As far as the grinding of the bit goes I use a new 400 grit belt, hold and rotate the bit in my fingers while applying pressure on the belt. This may sound impossible, but it is an offshoot of sharpening drill bits, which I also do on a 400 grit belt on my bader BIII. I have been sharpening bits that way for over 15 years, talk to any machinist, they do it all the time.
Del
 
Erin Burke said:
Thanks Jim. I see how that takes down the diameter of the pilot to the desired dimensions, but doesn't that leave the cutting edge of the larger-diameter counterbore essentially flat. I guess I'm just confused how to dress the newly created cutting edge so that it actually cuts. It sounds like a lot of folks have done it successfully, so I'm probably making things more complicated than they need to be. Thanks again.
Click to expand...

You are indeed correct Erin, in regards to the cutting edge of the major diameter aspect of the CB ending up flat after reducing the pilot diameter. The best way I've found to add "relief" to that cutting edge is just like you suggested, magnification and a small flat diamond file or stone :thumbup: ;)


:cool:
 
David Wesner said:
You are indeed correct Erin, in regards to the cutting edge of the major diameter aspect of the CB ending up flat after reducing the pilot diameter. The best way I've found to add "relief" to that cutting edge is just like you suggested, magnification and a small flat diamond file or stone :thumbup: ;)
Click to expand...

Thanks David! :thumbup:
 
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