Rota Broach - thumbs *way* up

[yossarian19]

My sainted mother bought me a set of Rota-Broach cutters for my birthday. If you haven't heard of it before, it's a hole cutter for sheet / plate material. Not a drill bit, not a hole saw. It's unique as far as I can tell.
First use was 7/16" holes into 1/4" plate mild steel. The supplied chart told me 900 RPM.
At 600 RPM, they screeched a little. Experimenting with feed rate (pressure on the drill press handle) I really punched it in there - and these things *devoured* the plate. Under 15 seconds per hole. The holes were round (not oval like I usually get with a twist drill) and with a very minimal amount of blow-through finishing the hole. Rota-broach recommends stick lube for these cutters; I was using 5w30.
With a more substantial lube & a press that could nail 900 rpm (mine is 600 or 1100) I'm guessing these perform even better.
As it is, I'm still VERY pleased with these tools. MUCH faster / cleaner job than with a drill bit. Definitely worth the $$ if you do much of any fab with plate or sheet metal. Available on Amazon, too.

 

[old_man]

They look like they may be just the cutter for mitering tube.

 

[2stix]

the design of the rota broach is actually for cutting sheetmetal parts at their spot welds. the holesaw type cutter has a spring loaded centering pin to keep it cutting just around the spot weld. they come in sets or you can get them individually. 1/4" to 1/2". you cut the first sheet and the back sheet pulls away leaving just the spot welded area. very useful in automotive restoration since you can save the panel and not drill holes into it. you just have to grind the spot weld off.

old_man. they do have these heavy duty cutters in larger sizes such as 1.5" but you will probably have to get them from a machinist supply house. the smaller rota broach (normally a set from 1/4" to 1/2") are designed for fast cutting, and the larger ones are designed for machine work. these are way too expensive to be used for mitering tubing. you are much better off getting regular bimetal hole saw cutters.

 

[markw]

They only go up to 1.5" from Blair. They work really well for drilling holes in up to 1/2" metal. One of my favorite tools. If you fab or work on a jeep at all, you owe yourself a set of these. I thought I had posted them up in the tools section before. Anyway, here's a video where I punched through 1/4" plate with a 7/16" hole for my bumpstop plates to use with the prothane stops.

https://www.youtube.com/watch?v=wxzPwu2JUgc

 

[xcm]

How long do these guys last?
And do they die a fast death when you let someone ignorant to feed speeds use them, like spot weld cutters do?

 

[yossarian19]

For my set, it's too early to say.
They are "supposed" to last much longer than drill bits & you are supposed to use a stick lube with them.
I use 5w30 with no problems.

 

[markw]

I've had a set for the better part of a year. My neighbor has had a set forever. Blair makes them for Blue point and the other truck brands. He's busted a few, but those were always doing freehand vs a drill press.

 

[XJEEPER]

On my list of tools to buy.......soon.

 

[91AzXJ]

They look sorta like a fluted mill bit

 

[ftwelder]

They are called "annular cutters" and the Rota-broach products are awesome. They will last a long time if you break them in properly and avoid interrupted cuts. (covered in part by 2sticx)


I don't known who invented these things but I have used them in Hougan magnetic drills on 1" HR plate and to remove automotive spot welds in a kit from Snap-on tools. They are a no-brainer for punching holes in sheet but you can't really "get creative" like you might with a bi-metal hole saw or it will explode.

 

[GSequoia]

The Blair spot weld cutter, a derivative of the Rota Broach, is an incredibly useful tool.

The tool cuts around the spot weld, leaving it in place for re-welding. It does so quickly (typically about five seconds per weld). You start by center punching the weld. Then you set the tool's spring-loaded pilot on the punch mark. You then push down with the drill and run it at 500 rpm. You stop when you feel it break through the first layer of steel.

The cutting heads are a consumable. They are two-sided, when you trash one side you spin it off, flip it, and put it back on. The teeth are relatively fragile, if you catch the bit on something you will snap off teeth.



PS - Yes, that drill is older than you.