Cutting Pulley Keyways - Without a Broach

[rwm]

I just did this. I used a shop made boring bar type tool with a shop ground HSS bit. Here are pics:

I use a zero rake with about a 7deg clearance angle on the end. The side clearance was guestimated and was probably only a few deg. Set screw in the end holds the cutter.





I just went back and forth with the carriage advancing the cross slide as needed. The whole operation took about 5 minutes once I was set up. You should give this another try with a different cutting geometry.
I could see a blind hole not being quite so easy but still possible. A blind hole will be even harder with a broach however! ; )
Robert

 

[kb58]

I've made keyways simply by milling them. While they end up with a radiused top (or bottom), it doesn't matter since the key can't go there anyway. I've had zero problems with them.

 

[C-Bag]

I know you don’t want to hear this but an arbor press turned out to be a totally handy thing for me for pressing in and out bushings and bearings,(much easier and better than the old vise method) and shafts, straightening all kinds of things, like gibs and of course broaching. I bought a basic set from Shars also and have been making my own guides. Also buying broaches as needed off eBay.

 

[ericc]

It should not be that bad in aluminum. Use the sharpie trick on your tool to make sure that it isn't rubbing anywhere. What is bad is to cut a key way in steel using this method. I've done it, though. Make a consumable "top hat" that plugs the hole and drill a hole right on the edge between the plug and the hole. This will get a lot of the metal out. Then, the boring tool doesn't have to eat too much. By the way, the "top hat" can be used again if you don't lose it!

 

[Earl]

I really do appreciate all of the comments and suggestions. My lathe is a Grizzly g0709, plenty rigid for this kind of work. I have no desire to cut another one unless sheer boredom sets in and I cant find anything else to do! I have lots of respect for you guys that make this process work for them. It just didn;t work for me. I tried several grinds starting with almost no relief at all and ending up with what was in the picture. I believe the the real issue with my tool was the amount that it flexed. The pulley is 2 3/4 deep. A shorter pulley may have yielded better results. The project is complete, not as I planned but it is workable. Thank you all.

 

[rwm]

I am glad you got it done. Your lathe should handle this no problem. I have in the past cut a keyway 3" long with a 1/2" bar.

I think there may be some confusion about rake angle and relief angle? Relief angle is almost unimportant in this application as long as it is slightly positive. Rake angle is critical and should be near zero. The last pic you showed had a very high rake angle. I just post this for any one else who might want to try this. Also for your next pulley!
Robert

 

[hman]

I used a Grizzly G4000 lathe to cut a blind keyway in an aluminum arbor. I'd cross drilled into the bore where I wanted the keyway to end, to allow the shavings to break off at the end of the cut. See post #711 at

Potd - Project Of The Day- What Did You Do In Your Shop Today?

For several years I’ve made very frequent use of a Delta 1”x30” belt/5” disk sander. Never had much success with the disk part, so I turned an aluminum arbor/adapter and mounted a 6"x1”x1” Scotch-brite wheel in its place. This wheel is absolutely the cat’s meow for deburring, polishing, and...

www.hobby-machinist.com

 

[Bi11Hudson]

Before purchasing a broach set, and a shaper, and other questionable methods, I cut keyways with a hacksaw. Stacking several blades made short work of the pulleys. I cleaned it up, after a fashion, with a three square file. I have tried the method you describe with a lathe. If the cut won't fit the machine, it's a null idea. The pulley I was making did fit. But it took longer than my patience lasted, whereupon I reverted to the hacksaw and file. I still don't have metric broaches, so use a smaller broach and open it up with a file. The broach set cost a lot, way too much, but has saved a lot of time over the years. The hacksaw I still have around, the pins have been drilled out for stacking. But nothing in my shop gets thrown out.

.

 

[rwm]

I have given some thought to making a broach. Shouldn't be too hard.
Famous last words....
R

 

[WobblyHand]

I used a parting blade as a cutter, and cut a blind key way in a cast iron handwheel. It was difficult and tedious, but it did work. I mounted the blade horizontally rather than vertically and used the carriage to cut the slot. The build up of swarf in the key way was a challenge. I solved part of the challenge by slightly shaping the key. Also cut a keyway in 12L14 the same way. Both were blind so to speak. I took small cuts. The HSS parting tool had no problem cutting if one took small bites. If you got greedy, it would dig.