Presses and techniques for 1/2" HEX broaches

I was looking at getting a hex broach when it dawned on me that not only would it obviously not fit in our 1-1/2 ton arbor press but also would need quite a large one at that.

Edit: With a 18"+ length Why was I thinking 18"! Thanks Ty. 11-7/8" it is. I guess I was looking at 7/8" hex broaches for some reason? Anyway back to the question.

I’m wondering what other teams have and where to source it from or do you even need a press? Also has anyone used a rotary broach and thinks it would be viable for FRC?

Where did you find an 18" long hex broach?

Worth mentioning that you can also pick it up from AndyMark: http://www.andymark.com/product-p/am-2204.htm

If your team has an adjustable table drill press that’ll probably do the trick. You can lower the press to the height you need then lower the chuck. If you need to push for a few extra inches you can even put the broach inside the chuck.

Many teams don’t have one but if you have a lathe you can use a powered-down lath to press the broach.

We go to Funky Monkeys to use their homemade press, or to the local community college where they have a very large press.
I would highly recommend against using a drill press to do it. Going to aluminum is hard enough with an actual arbor press, and using a drill press will likely damage it.

Using a drill press as an arbor press is a great way to find yourself in need of a new drill press, and an arbor press…

You can use a sufficiently large lathe, buy it’s still no replacement for an arbor press. We have a Grizzly 3 ton arbor press and it has been fine. I would not recommend anything smaller than 3 ton. There’s been a few things we’ve broached where I’ve found myself hanging off the handle to get it through. Also worthy of discussion is the fact that you need a suitably strong table or stand to bokd it to.

Would one of these work?

I have one at home (different brand, 25 years old)…doesn’t everyone?

We use almost the exact same one. It works, but there is no easy way to make sure the broach is completely centered.

Also, it takes like 10,000 cycles of the hand lever to broach one thing. It gets very annoying, and takes us way too long. Does anyone else have experience with this, and do you have a good technique?

What the heck are you guys broaching?

I have access to a large 6 ton press in our machine shop but we us a small 1 ton press from Harbor Freight and it easily broaches 1/2 hex in all the material we have used for FRC.

A good sharp broach should have little trouble with aluminum or even cast iron in a small press.

It looks like you could just swap out the bottle jack for an air over hydraulic one. It won’t be blazing fast, but a lot less annoying than pumping the handle a bazillion times.

Many of the ram ends on those presses are threaded under the cap, if so you can fabricate a custom broach holder, which will maintain the broach being straight. Think of it as a block that is drilled out to the 1/2 round blind hole so that the broach will be supported, then attach it to your press.

As for the 10,000 cycles to broach, you could always convert your press to pneumatic using one of these (or similar) http://www.harborfreight.com/10000-psi-air-hydraulic-pump-98318.html

Assuming you have air power in your shop it might save you some handle pumps.

Greg

I actually brought home a 3.5" dia 14" stroke pneumatic piston form my summer job, with the intention of converting our press for broaching, but nobody took me seriously, so nothing got done. And now nothing will before build season… :confused:

And we actually made a little piece to go on the end of the hydraulic ram, but it is not long enough to hold the broach straight, just in the center of the ram.

I calculated that that cylinder only puts out about 1000lbs of force on 100psi. Were you planning on adding a lever arm or something, or is that enough to force a broach though?

I feel like I’m missing something. What’s wring with just using the 1/2" shank on the bottom of the broach to keep it straight? Is that not good enough?

Keeping broaches straight is something that is hard for students (and some mentors) to do without a fixture or jig. Over many year I have seen students kill tons of sprockets, gears & hubs due to a crooked broach). The thickness of the part you are broaching and the material plays a big part in this (the thicker the better).

I honestly have no idea. I wish I knew, because then I might pursue it further.

We broached some HTD 5mm pulleys that were 1/2" wide, and a few of them came out crooked. This was probably due in part to poor technique (and execution), but I would not trust most of our team members using our current setup for high-speed applications. (where the broached piece is running at high speeds)

All the presses I’ve seen that use bottle jacks have very sloppy tolerances that allow the ram to shift position laterally. It is virtually impossible to get a consistent result without constant fiddling with the broach/part, even with a fixture.

In general, if you know that whatever you’re inserting the shank into is perfectly perpendicular to the table, that is a suitable means of aligning the broach.

To the earlier question in the thread, rotary broaching is viable, but it is also finnicky to get a good fit. We have been using a rotary broach for 5 or 6 years now, but almost every rotary broached part we make, we run a push broach through afterwards to eliminate the “twist” you get in the hex profile due to the way rotary broaching works. The nice thing is no alignment is necessary for this, as the existing hex guides the broach.

I would HIGHLY recommend against using anything with bearings to broach (a lathe, drill press, mill, etc). You can brinnell your spindle bearings and destroy them.

I have an old two column press that came out of maintenance shop from the Masonic Temple in Detroit, probably circa 1920’s. Works like a charm!

http://www.practicalmachinist.com/vb/attachments/f38/112939d1406518134-large-arbor-press-arbor-press-10.jpg

Back in the day 1678 would use the knee and turret of our bridgeport to broach 1/2" hex by putting a piece of 80/20 with a central hole underneath and raising the table.

Buy yourself a properly sized arbor press(or modify the arbor on one to have a deep hole and do it in 2 stages). Thank me later.

Also,

Make sure you hole is true; I prefer a drill and ream to size. You must also lubricate the broach for best results. In my home shop (where the press is) I have used diesel fuel, Kerosene, WD-40, or fine spindle oil. If you slightly back off the ram before each stroke, the broach can recenter itself and stay true to the hole. If you are broaching items thinner than the distance between the teeth on the broach, use a scrap piece with the same hole size to make up the distance and keep the broach running true.

DO NOT WIRE BRUSH A BROACH AS YOU WILL DULL IT. DO NOT RUN IT IN BACKWARDS EITHER!

We just purchased a 3 ton ratcheting arbor press off eBay for $168 (plus $98 shipping) that has sufficient stroke for our hex broach. The press isn’t a Dake but should suffice for what we need to do and about 1/10th the price.