Better to try with the mill's quill or even a drill press though a hydraulic press is preferable.. Though it is a long keyway and you will have a lot of teeth engaged that will take quite a bit of effort and may well clog the gullets of the teeth so you might have to withdraw the broach part way through to clear out the chips.

Can you shorten the key slot as 70 mm is long and a normal broach may not bee able to produce a size slot that length. Looking at the shaft the key could be recut further down. The norm is to create a relief diameter to clear the slot depth just beyond the key seat. Alternative is to create a separate keyed bush and retain it with screws into the longer bush. Just a thought on alternatives.

Machine tools such as lathes and mills are not presses, which is what you need to force a broach through metal. Don't even try it. You risk damaging your tailstock or mill. Find someone with a hydraulic press or make up something with two lengths of fine threaded rod of stout diameter and two stout steel plates, one to hold the job in place, the other to bear on the broach.

A small arbour (arbor?) press is not expensive and a better tool for the job than the lathe or mill. Once you have one you will find it useful for all sorts of jobs. a 1/2 ton one from china starts at about £35 shipped on ebay, with 1 ton "shipped from UK" at under £50.

Robert G8RPI.

There is a pre owned 3 ton arbor press on Ebay at the moment £80 which has 300mm of travel.

A push broach will work fine but care is really needed. When we had long bore to keyway we usually made up a sacrificial bush (of the same material!) then drill a hole of the right size through the assembly. This removed most of the material leaving the broach to square things up.

The length of the broach will be the problem and need an extension so what we did was grind the top end of the broach to a diameter then machine the extension piece to fit on to it. This meant everything was in line and we didn't have to juggle and hold bits with a hand under the press ram!

I once broached a steam engine pulley that was about 9 inches long with a 1/2" keyway through an 2 1/8" bore with no problems.

Hi, I wouldn't think a 5mm Broach wouldn't take too much to push through, however I've never done it in brass and it may be prudent to do more passes than normal by using thinner shims, which are easy enough to make, thinner shims may help stop the Broach digging into the brass, but as I say I've no experience of broaching brass.

Below is a photo I did through a steel pulley 1" thick with a 1/8" Broach with my No. 4 flypress, which was no bother at all.

Headroom is the thing, both my 1/8" and 3/16" Broach's are 6 3/4" long to give you an idea, but the effective height is about 6" above anything I need to broach because they will sit into the bore about 3/4" before the fist cutting edge starts to touch.

Regards Nick.

The other way to ease the load is to push a smaller width broach through first, I have done this several times when I could not be bothered to make the trip to my friend with the hydraulic press, just shim the smaller one so it cuts to the same depth as the larger. Doing it this way I have done 40-50mm long keyways 3/16" wide in cast iron flywheel hubs with just the old Naerok drill press to push them through with.

If on the lathe then using teh carrage to plane the keyway would be my preference to the tailstock but turn a runout groove part way down teh bore then you only need do about 25mm length. These four 3/16" wide ones on the left are all 1" long and in steel just planed with the carrage.

Similar can be done on the mill using it like a slotter, quicker if you have a quill than just a knee.

Just had one thought, you could drill a hole at the end of the required key position and slot into that rather than going all the way through.