Taper crimp

[fiver]

hey now I just got drilling triangle shaped holes down pat.

 

[KeithB]

I used to tell my students that there were four things that drills didn't do in metal:

1. Drill round holes.
2. Drill straight holes.
3. Drill holes the right diameter.
4. Drill holes with good interior finishes.

That's why they invented reamers...

 

[Pistolero]

Ah. the old Indian chief Soh Cah Toa raises his valuable mnemonic head again! I always teach and use it.

As to flexibility - yep, everything is a spring, NOTHING is rigid, although some things are a lot closer than others.

Bill

 

[Pistolero]

+1 for KeithB's comments. Yep, ream if you want a real cylinder as your hole. The hole will
have one more lobe than the drill has flutes - since most holes are drilled by two flute drills,
they are actually rounded triangles.

When we needed to drill really good holes at work, we used gundrills with internal coolant delivery.
Single cutting edge, and they tend to cut far straighter and rounder holes, often good enough as is,
but if you want it really to a dimension and surface finish, you need to ream and lap. Just like barrels.

Bill

 

[Brad]

I tend to team after drilling to a smaller size. If I don't have the right size reamer I drill undersized and bore close to finished size with a boring bar. Final sizing is often achieved with emery on a split rod and time.

 

[smokeywolf]

I skipped drilling triangular holes; went strait to drilling square holes.

 

[Brad]

There is always a show off.

 

[Pistolero]

I have a drill for drilling square holes in wood.....never saw it done in metal!

The two flute normal twist drill drills a triangular hole, so that guy used a three flute
(and VERY trick) drill to drill 4 corners, and said he would use a 5 flute to drill a
hex hole.

Pretty slick!

Bill