Flat Screw?

My machine shop opinion (I'm not an engineer) is it wouldn't be very strong, and could prove to be a bitch to assemble. I guess it all depends on what you expect from the item.

Harold

I've seen screws like this, but I'm blowed if I can remember where. They worked (operation and assembly) very well - surprisingly so - but I seem to recall that they had thread contact for more like 90 deg total, a little more than you are specifying.

Lateral stability? Depends on the orientation of the force. Excellent to poor, I'd suggest. (sorry).

Try it on a sample. I think you'll be pleasantly surprised.

Jeff R.

Sounds like a tap to me, but I'm just an engineer.

Richard

Grin! A tap, but with very limited side support. The typical tap, even a two flute, has greater engagement which helps keep the tap in alignment with the hole. He's talking, at most, 80 degrees total of engagement of the diameter. That's not much to help keep it straight between sides. He'd have a far better shot if it was more than 90 degrees per side. You'll get a better understanding of what I'm talking about if you try to tap a hole free hand using a two flute tap. It brings into sharp focus why hand taps generally have four flutes.

Harold

--Sounds like an inside-out application for a Formdrill. If you could redesign the part so that it threads onto a stud then it becomes easier. Alternately you could spotweld a threaded stud onto the bottom of your part and use that to thread it into the hole.

It's similar to an old style (1940s) doorknob spindle. A threaded piece of square stock.

Cheers,

Kelley

Paul What you have described is the "thread" that is used on the old Winchester Model 12 shotgun.

JRW

Kelley Mascher snipped-for-privacy@comcast.net

That's what I was thinking--having had a knob just pull free of one.

Threads, flutes, and a set screw. It must have been someone's quick fix that made it into general use, somehow--a cheap way out, for mass production. Frank Morrison

A couple of points here. The threaded square shaft for door knobs has been around much longer than the 1940's. Also the system works fine if you keep the set screw tight. The flat sides of the square spindle allow you to set the screw every 90 degrees. This permits the knob to engage the bearing surface of the escutcheon and allow it to be used on various door thicknesses and trim options.

Much much longer indeed. My house has those on the original doors, and it dates back into the late 1800s.

It's tought to keep the setscrews tight, especially in a teenager's room door.

etc.

Next stop is red locktite.

Jim

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