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mountainman
June 14, 2007, 16:15
I need to flat bottom a .413 diameter hole with a boring bar to a depth of about 2". I'm doing this on a boring head. anoyone got any suggestions. I was thinking about taking a 7/16 min bore brazed carbide bar 2.25 DOC and sharpening it down to .375 min bore. Is that doable, or is there anything I should be careful of?

yovinny
June 15, 2007, 20:42
I'm not going to be much help with the boring head, as I dont think mine has even left my tool box in probably 10 years, but I have another thought.

Know anyone or have a grind shop around you'r area that sharpens mill's ?

It would be relatively simple for them to grind a 7/16's end mill down to .413 for ya.

NoNotAgain
June 16, 2007, 18:25
Originally posted by mountainman
I need to flat bottom a .413 diameter hole with a boring bar to a depth of about 2". I'm doing this on a boring head. anoyone got any suggestions. I was thinking about taking a 7/16 min bore brazed carbide bar 2.25 DOC and sharpening it down to .375 min bore. Is that doable, or is there anything I should be careful of?

Vinny has the right idea, but you can purchase a 10.5 mm metric reamer for around $20 from McMaster-Carr.

part number 8851A45 $19.37 Each

mountainman
June 17, 2007, 07:26
Here's the deal, I got the walls to the right Diam using letter gauge drills. ( Holes ususally drill oversize and you just have to know how to expect that except with reamers) But I have that 118degree bettom, I just need to flat bottom that bore. The end mill seems nice idea. I got a Sherline and a grinding hand piece that I turned into a grinder tool holder on my QCTP. Being as I am cutting alum, I'll try turning something out of drill rod.

yovinny
June 19, 2007, 04:45
Since it's in aluminum, if you have some experience and something to grind drill's on. Maybe you can just get away with regrinding the drill flat, like a 2 flute end mill ?

mountainman
June 19, 2007, 07:47
got any pics of one of those regrind drills. I usually stay away from the boring head as much as possible.
Here's the thing do, I can regrind 135 deg for a starter hole and teh problem is that the hole is usually off center and way oversized I'm suspecting that my angles don't come out equall :? ( I'm gonna hold out for a drill doctor). I take it that this wouldn't be a problem on say anything over 3/8" diameter? got any suggestions.
John

Edgsmth
June 19, 2007, 09:44
Originally posted by mountainman
got any pics of one of those regrind drills. I usually stay away from the boring head as much as possible.
Here's the thing do, I can regrind 135 deg for a starter hole and teh problem is that the hole is usually off center and way oversized I'm suspecting that my angles don't come out equall :? ( I'm gonna hold out for a drill doctor). I take it that this wouldn't be a problem on say anything over 3/8" diameter? got any suggestions.
John

If you started with an undersized drill, say 3/8 with a factory point and after center drilling you should be able to get fairly close even with a hand sharpened drill. I've sharpened countless drills and it is tough to hit dead center, that's why even a factory point will drill oversized. By drilling a pilot hole you will stay off the point and finish with the outside lead edges of the drill, sort of like using the drill as a face cutting reamer.