Broaching question, key way size vs arbor press size

WobblyHand

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Need to broach some 5mm key ways in some 14mm bore aluminum pulleys for my Teensy powered electronic lead screw project. Tried holding the pulley in a lathe chuck to manually broach, but the pulley kept popping out of the chuck. The thin steel edges of the timing pulleys are not easy to grip. Manual broaching isn't easy on a lathe due to the limited mechanical advantage and it is hard to get the correct widths.

However, this year, I have a 3T arbor press. Can a 3 ton cut the key way for me? I don't have any broaches, but I could buy a small kit, if it would do the job. Is a 3 ton adequate for this? (5mm broach in a 14mm bore). If it is easy, that would be good to know. Likewise if you know it would be difficult, please tell me. I presume as the broach width goes up the force required increases. Likewise if the material is steel, it probably requires more force. If it is effectively impossible with a 3 ton, I will have to find another approach - maybe finding someone to do it. Thanks.
 
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It's probably less the tonnage than the total height of your work. The work plus the broach have to fit within the capabilities of your press. Should be easy enough for you to check that.
 
It's probably less the tonnage than the total height of your work. The work plus the broach have to fit within the capabilities of your press. Should be easy enough for you to check that.
Thanks. I will go check that in a couple of minutes. Like right now!
 
With the pulley on a spacer plate and a cap on the ram, I measure 9" of clearance. If I turn down the cap and spacer, I could have 10". The 4 & 5mm broach are 172mm long to that fits no problem. The 6mm & 8mm are 298.5mm (11.75") long. Probably going to require some mods to use the bigger broaches. Got to measure things better to be sure. The ram does have a 12mm diameter hole in it, that gives me a little more height. Since I need the 5mm for this, think I will get the kit. Thanks for the info!
 
Your press is more than up to the challenge. Good excuse to buy more tools increase your capabilities.
Think I will be limited for the larger (11.75") broaches. Doesn't really look like they will fit without some strange modifications to who knows what, either the broach or the ram. The small ones with fit fine.
 
Not that you need it but I think one one of the common ways to get a bit more capacity (height) out of an arbor press is to just suspend a small secondary table beneath the existing foot of the press. Kind of like a stirrup if you need to visualize something. The press itself isn’t modified, just the relative position of the support for the work.

-frank
 
No problem... I've broached 1/4" keyways in aluminum and brass on my 3 ton press and 3/16" in mild steel...

As has been mentioned, the height capacity is the biggest concern.

-Bear
 
All of the above . I think the longer broaches are C broaches and a 3 ton is more than capable Wobbly .
 
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