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Large internal keyway

cuttergrinder

Hot Rolled
Joined
Mar 16, 2007
Location
Salem,Ohio
This may be the biggest internal keyway i ever cut. 5" wide by 1 3/4. 19" tapered bore
 

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I used a 3" carbide facemill to rough it out. The keyway is 22" long
 

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These kind of jobe are about all we use this old boring mill for. We have about 5 right angle heads for it of different lengths and sizes. We have other g&l boring mills that are much nicer to run.
 
When machining large keyways in tapered members you must account for the difference in the "m" dimension at each end of the taper. The keyway is NOT to be parallel to the side of the bore it cut on, it will be deeper at the large end of the bore. This is a bit counter intuitive and took me a minute to wrap my head around the first time I was faced with it.
 
Ah that's a baby keyway. :D Wish I had some photos of the ones I used to cut on the planer. And yes they were internal. About 4" wide and probably 8+ feet long. Probably not too many guys here will have done internal keyways that long on a planer.
 
I havent done any that long but i have done some on the planer. We have a 20 footer. We did one then the customer had it heat treated. The key got tighter after heat treating so i had to set up a grinder on the end of planer bar and grind the keyway to size on the planer . That was fun.
 
When machining large keyways in tapered members you must account for the difference in the "m" dimension at each end of the taper. The keyway is NOT to be parallel to the side of the bore it cut on, it will be deeper at the large end of the bore. This is a bit counter intuitive and took me a minute to wrap my head around the first time I was faced with it.

I indicated the bore at the center line but when i got it roughed out, it was cutting .040" deeper on the small end. I then indicated the bore right along the side of the keyway and bumped it around until it was true there.
 
Yep, if set parallel to the tapered bore edge, the key will be deeper at the small end, not the large end. And I bet it was fun fuzzing a smidge out. Good times. The long keyways on the planer were done with a long ~6" diameter bar of which one end was mounted to the floor on top of a post bolted to a base set flush in the concrete with a pivot at the top of the post. The other end was mounted to the planer head. Tool was mounted in the bar.
 
Yep, if set parallel to the tapered bore edge, the key will be deeper at the small end, not the large end.

Yeah, I was trying to say the part must be offset so as to cut deeper at the larger end to compensate for the difference in the "m" dimension, but I didn't say it very clearly. Hard to describe without a picture!:cheers:

And I bet it was fun fuzzing a smidge out. Good times. The long keyways on the planer were done with a long ~6" diameter bar of which one end was mounted to the floor on top of a post bolted to a base set flush in the concrete with a pivot at the top of the post. The other end was mounted to the planer head. Tool was mounted in the bar.

Done similar, only with the bar supported in a bushing at the far end of the part. Bar stays on center, obviously, and tool is held in a small slide attached to the bar and is advanced in at each stroke and adjusted sideways for keyway width. A PITA but got the job done.
 
I went from 1 extreme to the other. Today i had to poke out some 3/16 blind keyways in some shafts that had a .760 bore. The keyway had a radius bottom and were .200 deep. I poked these on the cnc mill.
 

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I did a set of metric keys something like 24mm wide, 26mm deep about 12” long. It’s been a long time. . .

They were going to sink them on an EDM at work. But had calculated over 30 hours of burn time.

A friend and I did them on my shaper in a little over an hour.

Oh, they were blind.

We each got a $5 lunch token. Last thing I did to help that company out.
 
The long keyways on the planer were done with a long ~6" diameter bar of which one end was mounted to the floor on top of a post bolted to a base set flush in the concrete with a pivot at the top of the post. The other end was mounted to the planer head. Tool was mounted in the bar.

Trying to see this in my mind. Your part was clamped to the table and the bar was held stationary, through the bore, by the head and a fixture off the table at the end of the planer. Is that right? In effect you were only using the table for movement and making the cut by adjusting the tool attached to the bar?
 
Yes, mostly. Part moved to and fro with the table, bar stayed still, far end attached to post bolted to floor and the near end to the head on the rail. Raising the head on the planer raised that end of the bar and the tool as well, in the expected ratio. Far end of the bar pivoted at the post. Adjusting depth of cut was done by moving the planer head. The pivot at the far post end was a ball joint with a through hole for the bar to accommodate movement of the head in any direction. At the head end was a universal joint type of setup mounted in the toolpost.
 








 
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