Drilling square hole

[kraits]

Square Hole Drill-bit - YouTube

[Pete F]

Thanks for posting that. I'd heard that the holes produced by this method weren't as good as broaching, but they certainly look ok in the video!

Here' some more information on how this process works if anyone is interested.

Pete

Linearly Independent: Drilling Square Holes (http://linearlyindependent.blogspot.com/2008/07/drilling-square-holes.html)

[Dave J]

These have been doing the rounds on different forums over the last 12 months or so, and I think it was on HSM that a guy home made one of these and it worked fine.
He had a website with lots of bits and pieces, but I cant remember his name.
Found it
Making a rotary broach and cutter (http://www.docsmachine.com/projects/rotarybroach/rb01.html)

Here is a video of how it works
How to Drill a Square Hole - YouTube

And here are some links to read all about them with some good pictures of the insides.
Don't care if it's Chinese - I want one of these... - The Home Shop Machinist & Machinist's Workshop Magazine's BBS (http://bbs.homeshopmachinist.net/showthread.php?t=50217&highlight=square+holes)

Rotary Broaching - The Home Shop Machinist & Machinist's Workshop Magazine's BBS (http://bbs.homeshopmachinist.net/showthread.php?t=27232&highlight=square+holes)


Dave

[Pete F]

I think rotary broaching is actually a different principle to that shown above. IIRC, with a rotary broach, the broach is held stationary on the work and "wobbled" by an eccentric, hmm, not sure how to describe it, I'll say "cam" but I'm sure somebody will shoot me down for that as it's not really a cam at all. Anyway, an eccentric "plate" behind the broach that wobbles the broach from side to side and drives it through the pre-drilled hole. I intend to make one of these, but just haven't had time ... hence why I'm typing while sitting in Tokyo!

On the other hand the one above is a "Harry Watt" drill bit. As I understand it, that rotates pretty much like a normal drill bit, BUT the drive to the specially shaped drill bit ALSO rotates. It's really tricky to describe, but I think it showed it on the video in the link. Imagine getting your drill press quill, mounting that offset on a plate, and also turning that around in a circular shape. Ok that's a really crap description, sorry you'll just have to look at the videos. Google "Harry Watt", he was a clever dude. Edit: Oh, just watched that video, ok, yes that would be another way to rotate the drive, run it through a fixture with universal joints so the axis of the drive is changed. Very cunning. Anyway the point is rotary/wobble broaching, and Harry Watt drill bits work on quite different principles, so may be confusing when intermixed in posts. Both pretty clever, but as mentioned, I've heard the former is better for a number of reasons.

Pete

[joe greiner]

More here: http://www.woodworkforums.com/f170/drilling-square-hole-142303/

Same link as kraits BTW.

Cheers,
Joe

[RayG]

One of the cleverest tools I've seen is called a two legged parser, it's operated with a bow, and can drill holes of any shape.

Peter McBride (aka Lightwood) made one a while back, I believe it takes a bit of practice, but works a treat for something so simple.

Two Legged Parser (http://www.petermcbride.com/parser/)


Regards
Ray

[Dave J]

Pete you are probably right as I think I saw couple of different ones while looking for that link. The one you describe is I think like the one John Stevenson posted a cross section view picture of in one of the links I gave.

Dave

[Pete F]

Pete you are probably right as I think I saw couple of different ones while looking for that link. The one you describe is I think like the one John Stevenson posted a cross section view picture of in one of the links I gave.

Dave

Yep, the first link is an excellent piece by Doc on making a rotary broach, however the Youtube video you posted on how it works is actually a Harry Watt drill which is quite different. The "I don't care if it's Chinese..." link is also a Watt drill, at least as far as I read into the thread, while the final thread is a rotary broach.

From what I understand the finish from a rotary broach is typically better, and it can obviously broach any shaped holes desired. Personally I'm only interested in hex and square, but the shape is dictated simply by the cutter. On the other hand a Harry Watt can only drill square holes if that's the way it's been set up, and I believe they're slightly rounded in the corners. However it is a true drill. A rotary broach is better understood if called by its other name, wobble broach, since that's all it does; wobbles and gradually shaves the surface much like a miniature shaper.

Pete

[Abratool]

To Pete F
When you get back from Tokyo etc we will have to meet up to do the case hardening thing.
regards
Bruce:)

[franco]

MEW had an article on the principles of the Watts type drills, and on making the cutters for them in the December 1991/January 1992 issue.

Frank.