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How can I broach a 7/8" square hole in a 3" diameter blind flange inexpensively

nc5a

Cast Iron
Joined
Jan 4, 2013
Location
Alaska
How can I broach a 7/8" square hole in a 3" diameter blind flange inexpensively

I have a small job coming in the shop in a couple days and I don't have the proper size broach to do the job. And, the job isn't big enough to warrant buying a new or even a used 7/8" square broach (even if a good used one could be found). I have 6 of these square holes to broach and I believe the flanges are carbon steel. The tolerances are reasonable as I believe they are simply square drive holes.

One idea is to drill holes then square the corners with a jig saw or scroll saw, then finish with files. Another is to drill the holes then mill them square with a 3/16" end mill, then file the corners square.

How would you do it if you didn't have a 7/8" square broach?
 
Do you have a shaper or can find one for sale cheap? I keep one around for occasions just like that. My friends like to laugh and say you can make anything but money with a shaper but the few times I've put mine to work it made a pretty penny.
 
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Yea for 6 holes I would lay em out and walk the mill around em. File the corners and done.
 
Do you have a shaper or can find one for sale cheap? I keep one around for occasions just like that. My friends like to laugh and say you can make anything buy money with a shaper but the few times I've put mine to work it made a pretty penny.


I have a shaper but it's not working at the moment otherwise I'd probably use it.
 
There are companies that sell round steel sleeves with square holes broached through them. Try MSC or your favorite mill supply company. The sleeves can be cut to length and silver brazed into a round hole in any steel part that needs a square hole. They are typically used to make boring bars and crank handles and are very cheap compared to buying a broach, a slotter or a shaper.

Green Bay Manufacturing $19.30 each for 4.25" long x 1.313" dia.

Larry
 
There are companies that sell round steel sleeves with square holes broached through them. Try MSC or your favorite mill supply company. The sleeves can be cut to length and silver brazed into a round hole in any steel part that needs a square hole. They are typically used to make boring bars and crank handles and are very cheap compared to buying a broach, a slotter or a shaper.

Green Bay Manufacturing $19.30 each for 4.25" long x 1.313" dia.



Larry

Good Idea, many thanks.
 
I have a small job coming in the shop in a couple days and I don't have the proper size broach to do the job. And, the job isn't big enough to warrant buying a new or even a used 7/8" square broach (even if a good used one could be found). I have 6 of these square holes to broach and I believe the flanges are carbon steel. The tolerances are reasonable as I believe they are simply square drive holes.

One idea is to drill holes then square the corners with a jig saw or scroll saw, then finish with files. Another is to drill the holes then mill them square with a 3/16" end mill, then file the corners square.

How would you do it if you didn't have a 7/8" square broach?
Send it down the road to someone that is qualified/tooled properly.

You can't doo every job that comes along, be helpful to your customer
and suggest someone else.
 
Be careful doing slotting using a mill by vertical plunging.
Spindle stopped, you will generate point loads on your spindle bearings.....Might never become a problem, but it could be an expensive hole in the end...

Do this at times on my CNC Deckel, but i made a clamp that fits around the quill and takes the thrust loads rather than the spindle bearings.
Cheers Ross
 
Be careful doing slotting using a mill by vertical plunging.
Spindle stopped, you will generate point loads on your spindle bearings.....Might never become a problem, but it could be an expensive hole in the end...

Do this at times on my CNC Deckel, but i made a clamp that fits around the quill and takes the thrust loads rather than the spindle bearings.
Cheers Ross

Good point, he mentions wanting to make a clamp in the video. His clamp would also clamp the spindle to the quill to hold the spindle from rotating.
 
But can you make money doing it that way ?
I would for 6 of them. For much more than that better tools would be needed.
For one I would get out the hammer and chisel, then file. (after using the small end mill to get a rounded corner square) But only because I do not have the broach like in the vid.
I would service the customer so they keep coming back, new guy might keep them.
 








 
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