Best Way To Cut Tapered Key Seat

carlquib

carlquib

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I need to cut a new tapered gib key keyway in a splined clutch hub. What is the best method, make a new bushing with the correct angle machined into the bushing or just use my existing plain bushing with a tapered shim to get the angle I need? I haven't ever had to cut one of these before and machinery's handbook was a little weak on the details other than giving me the proper angle. It is a 1/2" key going into a 2" bore.

Hello, my name is Brian and I'm a toolaholic
 
Is the bore tapered? Don't know why I asked, but the tapered seat sounds unusual at best.
 
No, it is s straight bore. Just the keyway has 1/8" in 12" taper. The tapered gib key is used as a locking element. I have been around them for years but haven't ever had to cut one.

Hello, my name is Brian and I'm a toolaholic
 
I've never done one of these before, but I'm gonna vote for the tapered shim. I think it will work. The only problem with either method is pushing straight down on the broach. I would guess that you would have to tilt the hub to the correct angle.
 
I think that is exactly what I am going to do. While I have the grinder set up to grind the shim I'll grind a washer to the same angle to set the part on while it is in the press. I think I'll try the first passes without the shim and then put my tapered shim and washer in for the finish pass. Wish I knew what the standard procedure was for cutting these. Usually in the past I have just had to repair the shaft and then just replace the sprocket or pulley.

Hello, my name is Brian and I'm a toolaholic!
 
Jim Dawson is right in that the cutting pressure must be in line with the travel of the broach.
Turn a bushing and mill the broach slot at the needed angle and at a depth that will keep the broach from cutting too much material.
You may need to make two bushings to get the proper depth without overloading the broach or cut the slot deeper and use more flat broach shims to get the full keyway depth.
The bottom of the bushing can be machined to the correct angle, a larger diameter can be turned on the bottom for better stability, or it can be mounted on a tapered bottom plate (Best).
Since the broach will start it's cut at one side of the hub, it might want to dig in and cant, so care must be taken.
Jim
 
Agreed with the other posters as to what is the practical for you to do in this instance; In industry these tapered keyseats were done on a keyseater with a tapered shim behind the cutting tool, at least that was done with the single tooth machines, such as the Mitts & Merrill that was in the shop that I apprenticed in, and in my shop before I sold out and retired, it could machine a 1" wide keyway through a 12" long bore, the one in the apprentice shop could do 2 1/2" through 24" of bore. The tapered shim simply was placed in the cutter slot behind the feed wedge and the cutter bar. I have made broach plugs for tapered bores, and they work fine, just have to hold the part so that the broach is in line with the press ram. Gib keys are not so easy to fit, best to cut the keyway a little shallow, and machine off the bottom of the key to fit at the proper seating depth.
 
Does anyone know a good method to center the keyway in a bore when using a shaper to cut a keyway? In a large bore, I line the cutter up even with the middle of the bore and then use an inside mic or telescoping gauge to center up. On smaller bores where I don't have that much room I just blue the bore and then carefully adjust the cutter until it is touching evenly on both sides of the cutter. I would still like to find a faster more accurate method.

Hello, my name is Brian and I'm a toolaholic
 
Centering round work in a shaper isn't something I've done but have given it a bit of thought.
Perhaps a indicator mount could be built to go into the fit of the lantern tool post.
It would need a tapered bearing,preloaded, with the indicator mount on the rotating end.
That would at least give center to the tool post. The rest would have to be worked out with measurements and math.
The wear on that gear doesn't look healthy.

WOW You got a shaper. That was the best way to get it done.
 
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