Need to cut a small keyway

[jmarkwolf]

I need to duplicate this keyway on another shaft. The shaft mild steel, diameter is 0.625in nominal. The key dims are 0.118in wide x 0.5in long x 0.080 deep.

Looks like the original was cut with an endmill, but all I can envision is a lot of broken endmills and ruined work if I were to try this with such a small diameter tool.

Can someone please advise the proper tool and procedure?

 

[Larry$]

Get a very short endmill, mount the endmill far up into the collet, take shallow cuts, blow the chips out as you go. Ideally using an endmill slightly smaller than the slot width so you can make a clean up pass down each side.

 

[MrWhoopee]

.118 is 3mm. Are you sure that shaft isn't .629 (16mm)? I'd be looking for a stub length 3mm endmill, maybe order a couple of them.

 

[brino]

I usually ramp down into them, even with a centre cutting endmill.
It seems to feel/sound better than trying to plunge then feed.
Brian

 

[epanzella]

Center cutting end mill. Plunge the ends to define the length, peck the middle out and clean up.

 

[Smithdoor]

I need to duplicate this keyway on another shaft. The shaft mild steel, diameter is 0.625in nominal. The key dims are 0.118in wide x 0.5in long x 0.080 deep.

Looks like the original was cut with an endmill, but all I can envision is a lot of broken endmills and ruined work if I were to try this with such a small diameter tool.

Can someone please advise the proper tool and procedure?

View attachment 476951

I start with a next smaller end mill to ruff out the keyway. Then finish with correct size.

You find trying to in step the end mill will waver around and by time finish you have a larger keyway or one does fit key.

Remember high speed and slow cuts or will eat end mills.

Dave

 

[mmcmdl]

All of the above and I always use a 3 flute end mill .

 

[Red96]

FWIW, I made a new leadscrew for my compound out of 12L14 (I know, shoulda used a better steel) and cut a keyway like that with a 4 flute 2.5mm end mill. It cut just fine doing .025" DOC and a slow hand-feed. YMMV. As mentioned above, you don't want to use an 'on-dimension' end mill, or the slot will come out slightly wider than you intended. 3-flute mentioned also sounds like good advice.

Used that same mill in some 1018 to cut out a triangular seat for a carbide insert. Mill didn't break or give any issues.....until a hold down bolt on my rotary table decided to occupy the same space when rotating the table. Plink!

 

[epanzella]

The dreaded "PLINK"!

 

[GT-6 Racer]

No problem to cut this keyway. 2 flute stub end mill. Spin it fast, 3800 rpm for mild steel and an uncoated HSS end mill. As Larry says air blast continuously. 10-15 thou per pass, more if free cutting steel. I do lots of 2mm and 3mm keyways for the robotics kids parts.