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broaching
- Thread starter MHW20
- Start date
Dabbler
ersatz engineer
rotary broaches take little pressure. each corner cuts independently. There is also a slight slicing motion on the sides similar to scraping. They cut very slowly but need little pressure. I'd guess that 1" would be about .010 per minute. but that broach would cost $$$$... The cut would take 90 minutes to 2 hrs.
instead of going to the final answer, I'd cut a 1" hole with a twist drill, then plunge cut with progressively better holes by plunging with centre cutting end mills, 1/2" and 1/4" . If I were doing only one hole in mild steel (you didn't specify the material) then I'd be inclined to make a carbide chisel and 'scrape' the rest: probably an hour or 2 to finish it. (HSS will do as well, especially if you have a 1/2" blank - it will require sharpening every 20 minutes/80 cuts or so) Cleaning up the corner takes the longest time. You can use a medium soft hammer to drive the cutter.
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instead of going to the final answer, I'd cut a 1" hole with a twist drill, then plunge cut with progressively better holes by plunging with centre cutting end mills, 1/2" and 1/4" . If I were doing only one hole in mild steel (you didn't specify the material) then I'd be inclined to make a carbide chisel and 'scrape' the rest: probably an hour or 2 to finish it. (HSS will do as well, especially if you have a 1/2" blank - it will require sharpening every 20 minutes/80 cuts or so) Cleaning up the corner takes the longest time. You can use a medium soft hammer to drive the cutter.
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Dabbler
ersatz engineer
John N had a great idea for a hardy hole, but his would work for you as well.
Get a 1" drive socket: You can even pick them up used cheap, as few want them. Drill a clearance hole, and then counter bore the hole for the socket so it is just below the surface. weld it in, and grind off the excess. a cheap drill, a boring head (if you have one or can borrow one) and a welder is all you need...
Get a 1" drive socket: You can even pick them up used cheap, as few want them. Drill a clearance hole, and then counter bore the hole for the socket so it is just below the surface. weld it in, and grind off the excess. a cheap drill, a boring head (if you have one or can borrow one) and a welder is all you need...
Who is John N?
That's a bit of metal to remove. Depending on what what exactly you are trying to achieve, like modifying an existing plate for some purpose vs. making something from scratch, how accurate the surfaces need to be, surface finish, how strong etc..... maybe there is an alternate technique to build it up from smaller sub-components & either bolt together or weld. Here is example sketch using 2 parts where the slot could be milled yielding 3 of the 4 surfaces. Or you could make it out of 4 blocks with surfaces just face milled. Food for thought
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Tom Kitta
Ultra Member
Drill the hole. If you have a shaper and proper attachment cut it out square. If not, drill the hole anyways and using small endmill remove extra material till you have small round corners and manually square it.
I usually cheat and do a simple U shape on the mill and weld to it the top of U made of flat stock.
You could also broach it with cheaper and commonly available brioches for key making but you would have to build a jug for that.
If this is some soft metal like aluminium you could use lathe as manual shaper. Not sure i its worth it with 2" of mild steel.
Square broach in 1" size new would be 100s of USD - I would guess like $500+. https://www.mscdirect.com/product/details/00307645 and that maxes out at 2" of mild steel. You may get used one for say $200+ - that is my guess as the biggest I saw were 1/2" - much more $$$ then just regular broach. Getting 1" HSS and making your own broach is also expensive as even short piece of 1" HSS blank is not cheap not to mention time consuming. If material is aluminium you could try using hardened alloy steel but still time consuming to make your own.
I usually cheat and do a simple U shape on the mill and weld to it the top of U made of flat stock.
You could also broach it with cheaper and commonly available brioches for key making but you would have to build a jug for that.
If this is some soft metal like aluminium you could use lathe as manual shaper. Not sure i its worth it with 2" of mild steel.
Square broach in 1" size new would be 100s of USD - I would guess like $500+. https://www.mscdirect.com/product/details/00307645 and that maxes out at 2" of mild steel. You may get used one for say $200+ - that is my guess as the biggest I saw were 1/2" - much more $$$ then just regular broach. Getting 1" HSS and making your own broach is also expensive as even short piece of 1" HSS blank is not cheap not to mention time consuming. If material is aluminium you could try using hardened alloy steel but still time consuming to make your own.
The only thing about end milling is the material is 2" thick working within a 1x1" pocket if I understood the dimensions. So an EM with that mount of flute length is probably going to be a larger diameter which leaves even more un-machined fillet in the corners to do my hand. Or if the corners are not critical, just the flats, then 4 holes could be drilled on the intersections. Well, I think more information would yield better possible solutions. So far we have discussed about 25K$ worth of machines. LOL
Tom Kitta
Ultra Member
I was thinking of milling it from both sides - so just 1 inch end mill stick out.
He could drill on 4 corners a bit further out - i.e. place the drill center at the exact spot the 1" ends - if you can live with the "extra" 3/4 holes in the material. I think this is what PeterT means by at "intersections".
For rotary broaching this would get ultra expensive and I believe the limit is only 1.5" not 2" - so maybe had to be done from both sides. Setup would cost AFAIK more then single square broach.
Getting someone else to cut the hole - i.e. farm it out could be an option.
He could drill on 4 corners a bit further out - i.e. place the drill center at the exact spot the 1" ends - if you can live with the "extra" 3/4 holes in the material. I think this is what PeterT means by at "intersections".
For rotary broaching this would get ultra expensive and I believe the limit is only 1.5" not 2" - so maybe had to be done from both sides. Setup would cost AFAIK more then single square broach.
Getting someone else to cut the hole - i.e. farm it out could be an option.