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Another tapping problem. (burrs)

Another tapping problem. (burrs)

Another tapping problem. (burrs)

(OP)
I've got a 55 mm circular part, notched on the OD in 4 places, with a 40.6 mm hole threw the middle.  The hole requires a M42 x 1.5 D9 thread.  The tap I tested is 6 flute (straight), TiN coated.

I may be running about 100 RPMs fast as the machine only has two speeds.

I keep getting a rather large burr (0.5mm-0.8mm or so) on the bottom of the part when the tap comes threw.  The part has a 0.8 mm chamfer on each side before tapping.

Any suggestions are appreciated.  Thanks.

RE: Another tapping problem. (burrs)

What is the thickness?

RE: Another tapping problem. (burrs)

(OP)
Sorry 4.5 mm.

RE: Another tapping problem. (burrs)

Are you doing this on a lathe?  Milling machine/drill press?

What is rotating at 100 rpm?

Regards,

Cory

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RE: Another tapping problem. (burrs)

(OP)
Basically the machine works like a drill press. (its a custom machine)  The part sits in a fixture on a 4 station rotating table. Load, chamfer, tap, unload.  The Chamfer on the one side is stamped in  the press.  The OD is has four 4.5mm radius slots for a spanner wrench, also keeps the part from rotating during tapping.  The tap manufacturer recommended a tap speed of approx 165 rpm.  The lowest we can currently run is approx. 265/270.

RE: Another tapping problem. (burrs)

What is the workpiece material?

Are you sure the burr isn't there after drilling/chamfering?

Regards,

Cory

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RE: Another tapping problem. (burrs)

(OP)
The material spec calls for 1008-1010 hot rolled, descaled and oiled.

Actually, I havent checked for a burr after chamfer.  I'll look into it next time I run a trial. (prob Monday)  We currently run 3 other similar parts on this machine with diameters from 32-36mm though.

The center hole is stamped out, so there is a little burr on one side.  That burr side is the one that gets chamfered though.

Thanks

RE: Another tapping problem. (burrs)

Can you find a spiral-flute tap in the size required?

RE: Another tapping problem. (burrs)

(OP)
That is one option I have been looking into.  I have a straight flute tap that I haven't tried yet.  If it doesn't work I will try the spiral flute.

What are the advantages to spiral flute?  Chip removal?

RE: Another tapping problem. (burrs)

Due to helix angle, the cutting edge is advancing at an angle to the workpiece, and this helps to reduce burrs.  Also, you can usually run a spiral flute tap at higher speed than straight flutes.

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