Google Watts Bros works.
Hi , just curious how some of you guys drill square holes in a lathe and/or mill machine ?
Any special tools that you have made and would like to share some of the information and your own experience in drilling square holes??
square hole drilling "http://www.youtube.com/watch?v=9qEhyQfbImY"]YouTube - square hole drilling
"http://www.youtube.com/watch?v=270qEZKXAfQ&feature=related"]YouTube - How round is your circle?! www.howround.com
Google Watts Bros works.
The More I Learn The Less I Seem To Know
how big and how many?
The first way to deal with a square hole is redesign. They are a slow work and a bit out of the ordinary so in general its poor design to use them if at all avoidable. My work is home shop work, not production, so for the onsey and twoseys i've had to do i've done it by
1) fabrication. weld/braze up a sq internal shape, machine the outside round and loctite/braze in place
2) broach, bought or homemade (which is much friendly on the wallet)
3) file. very accurate work can be done this way, especially if you use a male master with some blue on it to do the finish fitting
4) shape; either in lathe, shaper or mill; a cutte cuts the corner via reciprocating motion
may be others i'e forgotten about
for any volume a rotary broach or traditional broach would make sense
one detail the video(s) don't show is that the rotary drilling motion will not make a true square. the corners will have a weird fillet left in them. This subject came up years ago at the last shop I was at. One guy found a pretty detailed paper explaining the epicyclic motion that is the principal of this motion. The motion will generate a square movement (like with a scribe) but when a cutting edge (like with a boring bar or gundrill) is rotated through the inside of the same motion it (for lack of better words) "flares" and blends the direction change. Think of it this way, when boring a hole (round) a chip is being produced by the shearinig action of the cutting tool. If you could generate a truly square path, you would smash this chip and cutter into the wall of the next side of the square. The only square shapes (or polygons) that I know of that can be generated by rotary motion are external forms. Such as polygon machining on some swiss type screw machines.
Thankyou for the vital words,amazing when one uses the correct ? wording the search results can be more rewarding.
Square-Hole Drill in Three Dimensions
"http://www.youtube.com/watch?v=AWKW50d0oBM"]YouTube - Square-Hole Drill in Three Dimensions
Watts Brothers Tools floating chuck for drilling square and hex holes
Square broach or planer.
A few thoughts...
I suspect there are very few people who drill square holes. I have not used the method you demonstrated but I am familiar with it through literature. I have read about it in some of the older (antique may be a better word) text books I have collected. I think it is a process that is not well known and the tools are obscure relative to other cutting tools.
It was more efficient than I expected and is something I might try if the opportunity presented itself.
I was so intrigued by the second video I went the same day and purchased 'How Round Is Your Circle?'
The rotary broach method would probably not put anymore stress on the bearings of a machine than an ordinary twist drill. If you think about it the twist drill must push the material from the point to the lip before a chip can be formed. As drills increase in size the web thickens, thus increasing the amount of axial thrust required to move the material. This is true with point relieved drills as well.
Just my random thoughts...
Mcgyver's point about the 'hammering' action could be valid. I think it would depend a lot on the machine size versus the rota-broach size; a machine spindle and chuck has a lot of mass so it is not going to feel the hammering from a small broach, not much anyway.
Actually on a CNC machine I might be more concerned about the Z axis ball screw.
An open mind is a virtue...so long as all the common sense has not leaked out.
Rotary broaching does not generate any sort of hammering action unless one programs a peck cycle for the z axis feed (in a cnc). Typically feeds are held constant to keep the cutter advancing at a force greater than the shear strength of the material. Squares can be tough on the machine though depending on size and material
Shown rather crudely at the bottom of the page here: