clickspring patreon

Spare Parts #13 - Making A Square Broach

🕑 Added 2016-03-10 01:04:41 +0000 UTC

Comments

Jerry Vella

thanx for the response Chris, i didn't even consider distortion from differential hardening but it would definitely show up in a part like this, good to know how well the heating tray works, looking forward to your next vid, cheers

Clickspring

Hey Jerry, I wondered the same thing about whether it would quench fast enough, but it came out glass hard from the tray, so no need to take it out any sooner. The whole mass cools down fast enough that it doesn't seem to matter. It wouldn't form scale if you were to take it out just before the quench though, so you could do that if you wanted to without consequence, and that might be required if the part was much larger. This broach is so thin that it quenches very easily. It also occurred to me that it might introduce distortion because of the heat differential on the inside surface, but it seems to be fine. Same result with the recent hands, so I'll continue to use it. Cheers mate :)

Jerry Vella

Hey chris, great video as always, was just curious if if would be better to remove the piece from the heating tray just before quenching it to cool it down faster and improve the hardness, would it still build up some black scale if it was exposed for just a second? or are you getting it sufficiently hard with it still in the tray?

Clickspring

Cheers Al!

Al McKague

Nice video! I have no idea what I'd need to put a square hole in, but there must be something .... thanks

Clickspring

Hey Paul, I agree with you its a far more effective way to do this than the wire - its now on the to do list! The current one would probably be a bit wasteful of boric acid and gas for something small like a screw, but I think maybe a set of trays from 1/5th size, 1/2 and then the current one would be a good idea. Another video?

Clickspring

Thank you PJ! I started with an offcut of 3/16" ground flat stock, milled it to shape as you suggest, and then lapped it to the final surface finish and dimension. Have a great day mate :)

PJ

Great camera work Chris! Better all the time! Did you start with 5-6mm RB and mill it to dimension or 4-6mm sq stock and mill it to get the 3.4mm square first? Pretty odd size, can't wait to see what it is. Thanks Much! ~PJ

Paul Busby

Awesome. A surprise new video. As always, great work and a real joy to watch. Looking back to the beginning would that heat treat tray have been a good idea for the screws and other things you have done compared to the wire method. The tray seems a lot easier and reliable. The only problem now is when this and the previous video pop up on the subscription feed making me think even more new video's are released. Really looking forward to the next clock video.

Clickspring

Hey Ken, yes it will need to be hardened. Even though brass is quite soft to machine, when under compression like this it will quickly distort the annealed tool steel, and dull the cutting edge. Even when hardened and tempered, a carbon steel cutter still has a finite life before sharpening is required, even if its used exclusively in nice soft brass. Cheers mate, Chris.

Ken Condal

Great tip, Chris! I'm curious if the hardening would be necessary if you were only going to use the tool to make one or two broaches in brass.

Clickspring

Cheers Dan!

Clickspring

Hey John, yes tempered to a medium straw just after the heat treat.

Clickspring

Hey Paul, yes absolutely. Especially when you consider that often the holes are non standard dimensions to suit a particular need. I wouldn't like my chances of finding a 3.4mm square broach at an affordable price! Cheers paul :)

Dan Cowsill

Very cool Chris. Thanks for posting!

Clickspring

Hey David, in this case I just did my usual thing of using a gentle heat while resting the part on some ceramic wool, a thin cross section part like this tempers very quickly. But it certainly wouldn't hurt to use the tray. Cheers, Chris.

David Rysdam

Are you using your bluing tray to temper? Would be a great way to get a nice even temper.

Paul Grodt

Quality broaches can be crazy expensive. But they are often made from pretty high grade steel. If you are just doing stuff with brass and maybe mild-steel, even taking the cost of labor into account, this sort of thing might still end up saving you money!