Cutting a keyway the hard way.

[GunsOfNavarone]

Hello All...
As I am doing the ELS mod to my lathe, I have 2 aluminum pulleys I need to cut 5mm key ways into. I have nne of those tool holders that hold a piece of HHS at an angle where you use mill/lathe under no power and just slowly fat man it into the aluminum. I'm pretty sure there are people here that have winged it in many different ways.I thought abot drilling a 4mm hole about 3mm down from shaft hole, get a very small hacksaw blade and connect the dots. There would be a lot of filing...but it would remove a chunk.
Any ideas?
Thanks everyone.

 

[benmychree]

You could cut a open slot in the end of a piece of round stock and silver solder a piece of HSS into it, sharpen the correct width and do the job in the lathe. The heat of silver brazing will not remove any significant amount of hardness from the HSS.

 

[markba633csi]

Drilling out most of the material then filing to fit is certainly doable- I've done it too. You can grind the back edge of a broken hacksaw blade to make it fit the pulley bore and cut nearly all the way, then use a small triangular jeweler's file to finish. Make sure you have lots of light on your work area, it really helps.
-Mark

 

[GunsOfNavarone]

@benmychree You think silicon bronze would be ok? It's about 800* melting point...I could braze onto SS rod, I just don't have any HSS, but I have some broken taps/drill bits!

 

[Buffalo21]

Drill bit and the $20 Harbor Freight pneumatic air file

 

[mickri]

Search is your friend. https://www.hobby-machinist.com/threads/cutting-keyways-in-a-pulley.1050/ A Mr Pete video

A Halligan142 video

 

[GunsOfNavarone]

The diameter of the hole in pulley is 14mm, I kinda kicked around in the shop looking to see what I have to attempt it by that plunge method. The broken tap I have is 5mm at widest point. I have 10 and 8mm stainless rod. Just need to super glue it all together now...and a crash course in HSS grinding. Let's see it's the relief side that points East correct?

 

[mikey]

Would using an end mill work. Most keyways inside pulleys don't require a precision fit at the top of the key.

 

[GunsOfNavarone]

@mikey so instead of a dill bit then clean up with a file, you're saying just use an end mill, leave it round at the top where the keyway meets the pulley's keyway?
You're a moderator around here? I think you need to write an 1500 word essay why we don't do that around here...

 

[kb58]

@mikey so instead of a dill bit then clean up with a file, you're saying just use an end mill, leave it round at the top where the keyway meets the pulley's keyway?

This is what I did. And if the outer corners have to be square, use a file.