What's new
What's new

Boring deep holes efficiently on the lathe

Miller13

Plastic
Joined
Jun 21, 2014
Location
UK
I have a project which involves boring delrin and aluminium to 20mm dia, and to a depth of 35mm.

The way I do it at the moment is centre drill > 10mm drill in a Dickson MT1 tool holder > 12mm drill in the tailstock > 8mm CCMT boring bar (12 to 16mm) > 12mm CCMT boring bar (16 to 20mm).

The problem is when I get to boring, I have to pull out 3 or 4 times to evacuate the swarf. Even when I'm near the end with a bit of clearance inside, I'm still holding my breath not to catch some swarf between the inner bore and the tip and ruin the finishing pass. This is an aluminium and plastic issue due to the chip coming off in one long string.

What's a good way to approach boring, and would I be better to get some SDUCR 07 boring bars? The tip has a lot more clearance to the wall, but they start at about 13mm minimum bore.
 
I'm assuming this is a blind hole, otherwise why would you not just slam a 19mm/3/4" drill in there then bore?

If blind, then I would try a center-cutting 3/4" endmill. Such a tool can make a hole, just not as efficiently as a drill.

Regards.

Mike
 
I don't really like C insert shapes for boring bars except for roughing. If you can tolerate having the insert rotated about 10 or 15 degrees negative lead, it would not be too bad. So I typically finish bore with T inserts. These are kind of old school, but they work, giving you that precious few thousandths of extra bar clearance, less chatter, and still able to approach a flat bottom bore or shoulder.
 
I would probably lose the center drill, I don't think it's pulling it's weight.

1. big drill (split point).
2. 3/4 end mill flatten the bottom of the hole, open up to 3/4"
3. boring bar finish pass
 
I would probably lose the center drill, I don't think it's pulling it's weight.

1. big drill (split point).
2. 3/4 end mill flatten the bottom of the hole, open up to 3/4"
3. boring bar finish pass


+1 for this method.

Another thing to try is zip tie a long skinny tube (like a piece of auto brake line) to your boring bar. Hook the other end to your air hose. It should force the chips out of the bore during the cut.
 
Great stuff, thanks!

I happen to have an MT3 ER32 holder, I can put that to good use in the tailstock and switch over to DCMT for boring.

Lathe is Harrison M250 and yes, it's a blind hole Mike.
 
I have a project which involves boring delrin and aluminium to 20mm dia, and to a depth of 35mm.

The way I do it at the moment is centre drill > 10mm drill in a Dickson MT1 tool holder > 12mm drill in the tailstock > 8mm CCMT boring bar (12 to 16mm) > 12mm CCMT boring bar (16 to 20mm).

The problem is when I get to boring, I have to pull out 3 or 4 times to evacuate the swarf. Even when I'm near the end with a bit of clearance inside, I'm still holding my breath not to catch some swarf between the inner bore and the tip and ruin the finishing pass. This is an aluminium and plastic issue due to the chip coming off in one long string.

What's a good way to approach boring, and would I be better to get some SDUCR 07 boring bars? The tip has a lot more clearance to the wall, but they start at about 13mm minimum bore.

I'd start with good 18 or 19mm drill like others but even with existing tooling there is lot extra steps you take. Center drill-12mm drill-12mm boring bar skips half of the tooling with same results.
And SDUCR boring bar is much better for not mangling chips. Preferably with internal coolant channel so you can use pressurized air or coolant to help evacuating chips.
 
...If blind, then I would try a center-cutting 3/4" endmill...

Yeah, you want to blow as much material out of the bore with one tool. A 3/4" endmill would leave you
with about 37 thou for cleanup with the boring bar--perhaps a little less if you account for a bit of wobble.

Such a tool can make a hole, just not as efficiently as a drill.

Still way more efficient than the multiple passes the OP describes...
 








 
Back
Top