Keyway for 3/4 shaft ----Arghhhh

[Abner]

Cutting a 3/16 keyway in 3/4" CR shaft steel using an end mill. I keep breaking end mills.

It was recommended in - Machine Shop Trade Secrets to make a hexagonal single flute end mill for this.

McMaster has M2 HHS 3/16 drill rod. Could I cut a piece and grind a 1/2 way through flat and use that instead of the whole hexagonal shape.

Suggestions?

[whoski]

breaking EMs

flutes are packing with chips. use cutting oil and compressed air to blow chips out of keyway/flutes.

[Ken_Shea]

Slow the feed down and be sure you have the rotation correct for the cutter.

There are other aspects of end milling a keyway but you have to get past the breakage first.

[lakeside53]

yes, blow out the chips...

[Toolguy]

Keyway Cutting

There are 2 flute endmills with straight flutes made just for cutting keyways.
They work pretty well.

[Ken_Shea]

Not as yet mentioned,
The RPM, cutter material, Carbide or HSS and diameter, # flutes.

Given this, some recommended rpm and feed can be suggested.

[Forrest Addy]

Is it time for my keyseat cutting lecture?

[RB211]

Is it time for my keyseat cutting lecture?

Yes, if not for the OP, for the rest of us

[oldtiffie]

Seems so.

Thanks for the timely offer Forrest

Seems so.

[Ken_Shea]

Is it time for my keyseat cutting lecture?

I vote wait till we get some answers to the end mill breakage. then absolutely

[Ken_Shea]

OK Forest, we've waited long enough for Abner, you have my attention.

[Carld]

Abner, just what kind of endmill are you using. You mention a home made hexagon endmill and getting some 3/16" drill rod.

Why don't you buy a real 2 flute 3/16" endmill and get the job done?

[John Stevenson]

One thing I have not seen mentioned.

You state ENDMILL
Is it a modern centre cutting one? or one with the pip in the centre to allow all the 4 flutes to be ground ?

If it's the older one with the pip in the middle, that's your problem.
You plunge down and the cutter leaves a pip proud of the work, when you traverse sideways that pip breaks the cutter.

For accurate keyways you need a 2 flute or 3 flute cutter CENTRE CUTTING to hold tolerance on width, a 4 flute will cut over size.

[DICKEYBIRD]

I had a similar problem a while back and ended up grinding a single point HSS tool to do the job. It worked great!

Here's a link that shows the tool itself:

http://bbs.homeshopmachinist.net/showthread.php?t=37136&highlight=BROACHED

Maybe more work than you care to do but it got me out of a jam on a weekend job.

[gcude]

You can watch how Tubal Cain does it:

http://www.youtube.com/watch?v=5PeadD3sPNA

You will see that he recommends locking your Y axis.

Hope this helps.