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Carbide countersink speeds and feeds

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Norman.paz13

Plastic
Joined
Aug 30, 2019
I have got some parts that have two holes laser cut to 1/2". I need to put a 5/8" countersink on the holes.

I am running a 3/4" carbide 90° countersink, on a bridgeport clone.

How fast should I run the countersink ?
 
It comes down to stiffness of the setup in my mind. If you're holding the parts loosely (be careful!) then run very slow and watch your fingers. If you're fixturing the parts so they can't move and have a short overhang tooling setup, you can go faster.

So (roughly) back gear lowest speed on a BP for the first, perhaps second or third from slowest with a well fixtured, stiff setup.

Especially if using single flute, don't "bounce" the cutter into the work, bring it in slowly and smoothly so the cutting edge can engage without being damaged. Multi-flute tools are more tolerant of rough handling, but not by a lot.
 
Milland said:
It comes down to stiffness of the setup in my mind. If you're holding the parts loosely (be careful!) then run very slow and watch your fingers. If you're fixturing the parts so they can't move and have a short overhang tooling setup, you can go faster.

So (roughly) back gear lowest speed on a BP for the first, perhaps second or third from slowest with a well fixtured, stiff setup.

Especially if using single flute, don't "bounce" the cutter into the work, bring it in slowly and smoothly so the cutting edge can engage without being damaged. Multi-flute tools are more tolerant of rough handling, but not by a lot.
Click to expand...

The part will be clamped in a vise. It is a 6 flute countersink
The last time I tried this I was running about 300 RPM.
I got about 140 holes, then the countersink got dull, had to send out to resharpen.

I don't know if that's the expected life of the cutting edges or I was doing something wrong. (running too slow or too fast)

I am hoovering the countersink above the hole, and letting the quill feed lower it and engage the work at lowest setting .0015" per rev.
 
Norman.paz13 said:
The part will be clamped in a vise. It is a 6 flute countersink
The last time I tried this I was running about 300 RPM.
I got about 140 holes, then the countersink got dull, had to send out to resharpen.

I don't know if that's the expected life of the cutting edges or I was doing something wrong. (running too slow or too fast)

I am hoovering the countersink above the hole, and letting the quill feed lower it and engage the work at lowest setting .0015" per rev.
Click to expand...

I think the feed is too slow. Also, the "crust" from the laser may be affecting your tool life.
 
Norman.paz13 said:
The part will be clamped in a vise. It is a 6 flute countersink
The last time I tried this I was running about 300 RPM.
I got about 140 holes, then the countersink got dull, had to send out to resharpen.

I don't know if that's the expected life of the cutting edges or I was doing something wrong. (running too slow or too fast)

I am hoovering the countersink above the hole, and letting the quill feed lower it and engage the work at lowest setting .0015" per rev.
Click to expand...

I would be trying about .008"/rev. I've never had much luck feeding those multiflute carbide csinks slow.
 
Mike1974 said:
I think the feed is too slow. Also, the "crust" from the laser may be affecting your tool life.
Click to expand...

I have had this argument with everyone in my shop. I know A36 can't be heat treated.

But any laser cut edge, tears up cutting tools like crazy. I'm currently doing research on what affect the heat and CO2 gas has on the edge of laser cut parts.

I will try increasing the feed.

Thank you.
 
The carbon from CO2 will aid in hardening the surface with the plasma current. We used to run plasma cutter with nitrogen gas, the nitrogen would harden the surface glass hard. It's just a couple of thousandths thick but enough to tear up tooling.
 
Why are you using the quill feed. You will get a better feel for what is happening with your chamfer if you hand feed it. Also, from my experience using carbide tooling in a Bridgeport type machine you will have more problems with chatter wrecking your tooling than wearing them out.
 
Big B said:
Why are you using the quill feed. You will get a better feel for what is happening with your chamfer if you hand feed it. Also, from my experience using carbide tooling in a Bridgeport type machine you will have more problems with chatter wrecking your tooling than wearing them out.
Click to expand...

Tried using a HSS countersink, it countersunk 3 holes, and stop cutting just rubbing. Bought a new 6 flute HSS countersink and the same thing happened, about 3 or 4 parts before stop cutting just rubbing. I was goin about 500 rpm.

Tried the same two countersinks on a scrap piece of A36 with a drilled hole, not laser cut, and they worked fine.

I was using the quill feed, because I thought having consent pressure from the machine would give a better result on finish. i will try using just the quill.

thank you.
 
4GSR said:
The carbon from CO2 will aid in hardening the surface with the plasma current. We used to run plasma cutter with nitrogen gas, the nitrogen would harden the surface glass hard. It's just a couple of thousandths thick but enough to tear up tooling.
Click to expand...

Thanks for the info. Very interesting, and good to know.
 
Run 2000 RPM F.08 and if it sounds bad decrease the RPM. Correct RPM for that tool is around 1k-2k with that radius engagement in mild steel. G82 cycle with 10 rotations dwell for best result.
 
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