"'D' profile Gear bore Forming?

A set screw is the only reasonable option if you want to use the flat, but I don't blame you for looking for something better. The $30 solution is a Trantorque coupling -- see McMaster 5926K11. A much cheaper option (about $2) is a 3/16" clamp collar screwed to the face of your gear and tightened on the shaft. McMaster 6435K51

If it's a big cut for the "D", how about milling the hole with a 1/16" mill. You'll have to go wide on the ends of the flat. It'll be slow, it'll be hard to do without an NC machine, and it'll look funky, but it'll put a flat where the flat's supposed to be and put support behind the shaft where that's supposed to be.

If it's a shallow flat on the shaft, then Mr. Simmons suggestion of a set screw is a good one. Use the right type -- I only recently learned that set screws suitable for going against soft round shafts (cup type) are exactly wrong for going against flats (you want one with a flat end). The things you learn by hanging with mechanical engineers...

Or make your own broach from O-2 drill rod :-).

============ The single flat D appears to be a driving method that was developed early in the industrial revolution and is in the process of being replaced with the double D as this allows for balanced machining/less drift.

Much will depend on the material and set-up [and required accuracy] but many years ago in producing an automotive part I found out that the single D shape was hard to hold to an exact location. The solution at that time was to form an oversized blank, broach the hole, and then use the d-hole to locate from for the required concentricity/axial runout.

If you have a small volume, no tooling, no press, etc. you may want to consider OP [outside processing] by a broaching house such as

Rotary broaches are available for the double D.

several others Thus you should be able to produce the blank in one operation at the cost of slightly longer cycle time. Be reminded that there will be a *SLIGHT* twist or helix in the formed hole which could be a problem, or could make a nice snug press fit depending how you look at it.

The standard D type broach tools are available from

setting down when you check prices.

Another low volume alternative could be a bushing with the D hole that you press fit /loctite in the blank.

also see

{about 1/4 down page}

Good luck and let the group know how you make out.

You could broach a key slot and press the key against the D with the setscrew. Make the key a light / medium press fit in its slot and the gear shouldn't shift. A key this small can be adjusted to fit with a small hammer.

Jim Wilkins

JR,

You have an "old" gear with the correct hole/hub?

If so.. turn the old gear to a size that you can bolt or braze or weld (or fastening method of choice) to your blank before ya cut it.

--.- Dave

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HVAC motors commonly use fairly wide flats, some 1 and some 2 at 90 degrees, with round fan hub bores and setscrews. Some of the single flats seem to be nearly to the center of the shaft. So I would try a round bore with one or more setscrews.

Don Young

If the flat is that deep, perhaps round hole with a D-shaped insert pinned to the gear would work (much easier if the gear has a boss).

Just out of curiosity, did the determination involve a finite element analysis on the nylon molding or did you just slap it on and watch it merrily split apart?

Thus, new gear.

Best regards, Spehro Pefhany

Sure. Cray computer and all. Actually, I just used my onboard engineering prescience to 'see' the hub failing. The project isn't to the point where I can actually run the drive under load. JR Dweller in the cellar

Spehro Pefhany wrote:

-

Ok JR,

Now that we have a bit more info...

Round hole, then silver brase in the "flat"... make flat from round stock the proper diamter flattened with method of choice, mill,file,grind...

--.- Dave