Broaching keyway w/o an arbor press
I have little experience with broaching.
I want to broach (1) key way in a cast iron pulley, 1" dia bore with a 3/16" keyway.
If I buy a broach and bushing normally meant to be used with an arbor press, but don't have a press, what are my odds of getting a good result? I do have a hydraulic press, and since I'm only doing one speed is not a real issue. I also have a 17" drill press and Wells Index 847 mill if they could be used.
Not that I've done a great deal of broaching, but I've done some. I'll tell you how I have done it and I'll probably get wacked by some people here for telling you. Place the hole to be broached between two sturdy work tables just enough to clear the hole. Take a hand sledge hammer and a good size brass drift to protect the broach, begin by tapping to start and as the broach engages the hole and settles in you'll need to increase your hammering as needed. Then put the shim in and repeat. Use a little oil on the broach to make it happy.
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Last edited by 67Cuda; 10-31-2008 at 10:32 AM.
You can trivially create a keyway using nothing but a
lathe and a HSS toolbit. This one was done this way:
That's steel, cast iron would be easier.
if you're careful the hydraulic press is fine. Broaches are pricey and fragile - that's why the arbor press is best, because you can feel the action. Hydraulic you can't feel and it can apply way more pressure than is needed so if something is slightly askew it'll snap the broach...but like i say, it can be done with care. at the beginning I would s top every so often and release the pressure and resume, that's how i do it on the arbor press to make sure there's no lateral forces (ie what was straight up and down with no pressure might have move slightly askew with pressure, if that makes any sense)
Gregsy, The teeth on a broach are extremely brittle and are very likely to break if shocked by hammering. Your best bet is to set up the broach and sleeve with your hydraulic press. Use plenty of oil and watch where the broach is heading. If the sleeve goes into the hole very tightly, it will squeeze the slot for the broach and cause your broach to move inward and each tooth will take too much of a chip. This could cause breakage of the broach. To avoid this problem, be sure the broach slides freely through the slot when the sleeve is inserted into the hole. You will also have long life for your broach if the axis of your broach is lined up with the axis of the press ram. Best of luck. WWQ
I've made internal keyways using a bit held in a lathe toolholder cranked back and forth with the carriage (3/16" in steel), and also by pushing a broach with the tailstock ram (3/32" in brass).
For a one-off, I'd certainly do it as a shaper job. You can grind a cutter and put it in your mill. Use the quill to cut the keyway, moving it by hand.
There are many posts here about using either a lathe or mill as a hand powered shaper for small projects like keyways.
I use a hand pump hydraulic press, and not broken any teeth. For the price of a broach and bushing even on ebay, you can have someone broach it for you and then go out to dinner with the change. In a pinch, mail to me and I'll do it N/C.
Are you sure about the 3/16, mostly 1/4 key for a 1" shaft.
I have done it by using the knee on a mill to crank the part up past the broach. Make a plate to hang off the back of your table to hold the part. Butt the broach up against the V ways of the Ram. Get a nearby child to crank the knee crank and broach away. For a one off small key in mild steel this is pretty effective.
I know a guy who hammers them through also and reckons he`s never broke any.Was quite indignant when I told him it was not accepted practice.On getting to know him I discovered he does lots of things that`s not standard practice but the way he taught himself.To be fair I could not fault any of the work he turned out.
Thanks everyone. I might have to skip this whole process and buy a new pulley - upon further inspection I found that there had been enough wobbling of the pulley on the shaft that the bore is a little oversized. I think it would work if I put it back with a new key, but I might not bother with the risk of having it come apart again in a year. The pulley is $66 new so I can't get too involved in a fix.
Shux...I hate whn the price of something new makes it not worth the fun involved in building one!!!
Originally Posted by GregSY
I was going to suggest that you simply use the hydraulic press. I have an arbor press...sitting right next to a hydraulic press. People that have been working in the shop for a few years have asked....what's that??? pointing to the arbor press. We broach keys in the hydraulic press all the time. Just use plenty of oil, and make sure that everything is straight. You can't "feel" a hydraulic press per say, but when you use one enough, it sort of becomes an extension of you arm. You get to know the way things sound and look, and you sort of sense the "feel" in other ways.
Here is a slotter example built by Evan that would work for you, or some variation of his design. Then you would have it for the next slot you need to do...
If you pulley shaft hole is slightly our of round, bore it and use a proper sized shim and a new key... half the fun of making stuff work is saving the money that you can use for something else... all you need is the time
Here's one I made for my Aloris AXA. It keeps me from having to take the compound or toolpost off
Cutting keyways without broaches
Being a machinist for 30 years, I have broached keyways using a Highspeed toolbit ground to the size required. Turn the tool on its side and install into a boring bar. Adjust the boring bar for correct height and set gear train on the slowest speed to prevent lathe spindle from turning. Using the carrage hand wheel crank back and forth engaging tool bit .001 though each time (remember to back tool bit away from workpiece when retracting). You will accomplish a good keyway every time. This has also been done on 316SS material at work.
The above is to put a keyway into a shaft sleeve about 1 inch long to prevent sleeve from rotating. I mill a woodruff keyway in the sleeve then broach the 1 inch long keyway into the woodruff key.
works every time. Only takes about 8 to 10 minutes in stainless, less for softer material.
I like that and I just happen to have made some extra BXA blanks.
Lots of interesting ideas, but again, with only one to do and limited time I can't get too wild. In fact, I was so busy today I didn't even have time to even try to order one.