Broaching

stern

stern

Active User
Registered
Joined
Apr 2, 2013
Messages
230
I have been doing a lot of digging on line to learn about broaching, as sometimes Im stumped by not being able to cut a key way (not so fun with a file in steel :(). I have seen "broaching sets" sold, but no mention of what machine it fits ??? Example

http://www.accusizetools.ca/products_details.asp?big=3&small=10&proid=339

I have looked at rotary broaching, but most of what I would use it for would be key ways and making square holes. I have dug around to see if there are any "home made" ones, but so far nothing. What I know about broaching could probably fill a thimble, but the more I read the more Im getting. Would like to make something as I just cant justify spending a crap load for a real machine. Was wondering if I could make one to fit a press (something I want to build anyway), just not sure if anyone has ever done this.

So, if anyone has any ideas or advise I would appreciate it, and in the mean time going to keep hunting online for info :)
 
Broaching is best done on an abor press or shop press. In softer metals you could drive them through with a hammer.
 
Agreed: The set shown is a usual type set for use in arbor presses. I don't like the idea of hammering them through,but if I had to,I'd use a bronze mallet. HSS could chip easily where hammered. Be careful to make sure the broach is driven STRAIGHT down,or you could break the broach. And,progressively insert shims to deepen the keyway you are cutting. Too much cut at one time will break them too.
 
I use an arbor press and set it up to cut the common sizes. I broach the insides of the gear to accept the key and use a key cutting bit in the mill to cut the shaft at the proper location and depth. There are several sets available for various size keys and they range from quite small to pretty large so you can pretty much buy a set that will work within a certain size range without having to buy the giant and little tiny ones jus to get a medium sized one for say a 1/2 shaft. Hope this kind of helps, if you still need help don't hesitate to holler and we will be glad to try and explain it better.

Bob
 
There are special arbor presses that are made to hold broaches and have extended travel, but they are not required to broach, any arbor press that has the range and capacity will work. I have a Dumont Minuteman set that ranges from 1/16" to 1/8" plus a 3/16" broach and that covers most of my broaching requirements, in fact I just had it out last week cutting a 3/32" keyway in a part I made. The process is pretty simple, you just insert a bushing into the hole to guide the broach, coat everything thoroughly with a good sulphur based cutting oil and push the broach through. Then you shim the broach out a bit with one of the included shims and push it through again to complete the cut. I have used a brass or lead hammer to broach aluminum and brass, but don't recommend it. Broaches are extremely hard and brittle and will easily break, so the steady push of an arbor press is best.

Tom
 
Last edited by a moderator:
All good advice down below. I do a good bit of broaching. Cutting oil helps and pre-drilling a hole just slightly smaller than the size of the broach as close as possible to the bore really helps.

A hydraulic or arbor press is a must. Get it lined-up perfectly flat. I also made little tabs of metal with a square divot that fits the pressure-end of the cutter. It's much less likely to move around as you're applying pressure. Wear safety goggles. The cutters are probably in the 65-70 Rockwell range and they can and do fracture and pieces will go flying.


Ray
 
When broaching I stop and release pressure on the broach several times this lets things get realigned as you go and stops binding. Make sure you catch your broach when it drops free, I hang a burlap bag under my press because my arms are not that long.
 
Thanks all for the info and clips, as it sure helps to "see" the process in action (all I found during my search was large high speed machines). Didnt realize that the broaching could be done at a very show speed (like the hand arbour) but seeing it done on that and a hydraulic press (something I want to build) sure makes it clearer. OK, dont laugh now, but before today and reading these posts I wondered how I would secure the work ..... yea, feel stupid, but 10 seconds of video clip and my brain went AH-HA :)

Now that its a lot clearer I know I can make the hydraulic press I wanted and with no real mods (except a hole) and use it to broach. Thanks all, love this place, always learning something new :)
 
You must log in or register to reply here.
Back
Top