Square holes?

Drill 4 small holes in the corners and one big one in the center, then file the remaining material (assuming its not a blind hole).

Or, if the material is thick, make a round hole and put 4 setscrews in from the side to make it effectively square.

Or make the part in two halves and mill a 1/4" wide by 1/8" deep slot in each, then braze or weld back together.

Or, if sheet metal, drill round hole and make square with nibbler.

Suggest tie the chicken closed with cotton butcher's twine--also it's a = good idea to truss the legs and secure both them and the wings onto the = carcass or they will overcook in addition throwing the whole mess off = balance.

"Dave, I can't do that" wrote

Get or mill another piece of 1/4" square stock to use as a form. Bend a piece of stainless TIG rod into a U, lay it over the form and hammer and squeeze it into 3-sided contact. Continue winding the ends around the square and hammering them in, to make a square spiral long enough to grip the rotisserie shaft. Bend the ends into prongs.

You may have to experiment with an oversized form as the stainless will indent its corners unless it's hardened. I would NOT use a lathe bit; they can shatter.

jsw

The classic way is to use a lathe--drill a 1/4 in hole then stroke it out with a shaper that you've made out of a 1/4 drill blank.

The way I do it is to drill a 1/4 inch hole and have at it with a square file. Just did that last week except the hole was 1/2 inch square . I needed to unscrew a flapper valve and had poor access. So made a plate that could be screwed to the valve and used a 1/2 inch drive ratchet to turn the plate.

=20 Dan

get a rotary broach - there are some inexpensive ones for small holes like you want.

You can get 1/4" rods made for rotisserie use in most home improvement stores, look in the BBQ stuff.

Making the collars is easy. Get some 1/4" ID square tube that will slide over the rod. Make up a couple plates that have adjustable prongs and weld those onto the square tube. To lock them in place use shaft locks and drill a clearance hole through one flat of the tube for a longer wing screw.

Or make a cup style basket like

What I would try-

cut a disk of stainless about 3/16" thick and 3"-4" across, drill a

9/32" hole in the center and make your own round-to-square broach to finish forming the corners. assuming you have a hydro press of course...

then you could drill more holes spaced around the outer edge of the disk, and make & press "tines" into them for the food holding.

this way the whole part wouldn't have any fasteners to come loose, and it would be easy to clean.

If you make the parts from sheet stock. just drill the four corners, chisel-shear an X between them and fold the tabs out to form the square hole.

Louver slots on curved surfaces made similarly:

jsw

BINGO!, great idea I didn't know. This is why I wade through all the flotsam on RCM, I get a gold nugget every now and then.

PT, would I dare put a "D" shaper bit like this in my CNC mill and cycle the Z axis to shape out a square hole?

One step farther, I'm building AR15 lowers and the magazine pocket needs to be nearly square. Use this idea in the CNC mill to finish the corner?

Karl

I just buy the 30% lowers from Tactical Machining. Proper broached magwell and not much else done on them. Costs like $15 more than 0% forgings.

Normally I would use a slightly different form and index 4 times but you could also make up a square tool and get away without having to index at all.

Yup...mill a bit oversize first and then chop the corners away using a form tool.

I would be concerned trying to do this on a CNC mill unless you can lock the spindle brake, otherwise the bit could rotate as you try to use the mill as a shaper. I also think you will find you don't have a way to index the spindle to the orientation you want.

I think you would be much better served putting a cheap X-Y table under a manual arbor press and doing the pseudo-shaping that way, or just getting 30% lowers to start with.

There is no need to index if you use a square tool that has back-taper ground on all four sides--also very little rotational force is generated if you are cutting two corners at the same time and so as long as there is some sort of cam that locks the spindle during M19 you'll be fine.

A single axis slide under any industrial quality post drill will work, too.

I'll check that out, but I already bought five 0% lowers from DSA. Went along with a *GREAT* deal for DPMS parts kits.

"The Kid" is programming AR10 from billet as my next job. Anyway, deep square pockets are in my future. This route should be way quicker than using the Bridgeport slotter. I may still use the slotter if this takes much run time at all on the mill.

Karl

Heh, I bought five 30% lowers, built three myself, taught shop class to a friend who built another, and now everyone I know wants to build one. My next order will be for 10 more 30% forgings.

It seems I'm a fairly good shop teacher, I talked a friend who had never run a mill before or had any shop class through completing a 30% lower in one long day. Another half day for CNC engraving and anodizing.

If / when I get a decent CNC machine I'll probably try some there, until then I'm using the manual Bridgeport and my little CNC mini mill does fine for engraving.

Thanks Steve, I like your suggestion best. I had thought of the drill and file method, but decided it would probably not turn out square enough. The cup basket looks like a great idea but at 40-bucks EACH END, not gonna happen. {grin}

The drill and broach also seems like a good idea and I could use a

1/4" HSS lathe tool-bit blank as I have some of those.

Thanks to everyone who offered suggestions.

Dave

At the risk of perpetuating and OT ramble to my post, what are 0% and

30% castings?

Dave

This refers to the % complete of an automatic rifle lower. The lower is the only part that ATF registers. If its 80% or less complete you don't have to register the part. That is you're just buying a hunk of metal. 80% units were very popular till ATF decided the parts being sold were more than 80% complete. Now, lowers with less work done are more popular. The 0% units I bought are just a raw forging of AL - no machining done.

Karl