DD socket

[alsinaj]

I need to make a socket to drive a DD shaft 5/8" in diameter and 3/8" between flats. The only way I can think of to do this without making a broach is:
take a piece of round bar of somewhat greater diameter and length than the desired finished dimensions
bore a 5/8" hole through it
mill off top and bottom, leaving the desired 3/8" in the center, and also leaving the excess length intact at both ends
braze plates onto the milled flats
turn the assembly to finish outside diameter and part off the excess at both ends

Is there a better way?

[kitno455]

Buy a 5/8 DD steering coupler, and weld it onto your assembly.

allan

[alsinaj]

kitno455: Thought of that first, but found only 3/4" couplers. Do you have a source for 5/8" couplers? Thx. J

[MikeL46]

Why can't you mill it out with a 3/8" endmill? The rounded ends won't match, but the flats that transfer torque will be fine.

Mike

[Norman Bain]

Is the intended purpose of the socket coupling a "sliding fit over the shaft" or "fixed clamped"?

You had better tell us if the coupling is to be used in automotive steering; if so then the result will need to be well made.

If is just to drive a shaft on your yard tractor; then the approach you describe will work just fine. If is a sliding coupler then I expect that is should be hardened to improve longevity.

[JRouche]

Here is a simple one. 1" round bar. Drill to 5/8". Cross drill two opposing holes (1/4" or less depending on needed strength). Insert 1/4"(or smaller) rods into holes to create a 3/8" gap inside of the 5/8" hole. Weld outside of pins to secure. JR

[alsinaj]

Norman: The purpose is a sliding fit over the shaft. Not automotive. Not a lawn tractor, but close. Want to use the augur drive on my snowblower as a PTO to drive a big "manual" winch. The input shaft on the winch is DD shaped.

JRouche: That would work. I might take the OD up to 1 1/8". Only concern is that the contact between the input shaft and this "female DD" socket will be reduced to two points, one on each rod. That will probably result in the rods and/or the input shaft getting buggered up quicker than the approach using flat plates, where at least in theory there would be two line contacts.

[alsinaj]

MikeL46: I think you may have the key to the answer, i.e., that the female part doesn't have to match the 5/8" radius on the input shaft. A rectangular opening 5/8" x 3/8" would work just fine. That can be made by making a U-shaped part with a 5/8" wide by 3/8" deep channel in it, and welding a plate on top to close the channel.

[BCRider]

MikeL46: I think you may have the key to the answer, i.e., that the female part doesn't have to match the 5/8" radius on the input shaft. A rectangular opening 5/8" x 3/8" would work just fine. That can be made by making a U-shaped part with a 5/8" wide by 3/8" deep channel in it, and welding a plate on top to close the channel.

What about two pieces of channel welded down the middle of the "flats"? And if you use a radius corner cutter you could avoid the stress concentration that would otherwise occur at the square corners.

It wouldn't be all that perfect but if you have a two flute HSS endmill with chipped corners you could grind and match up by eye some 1/16" radii on the corners. I bet it would be close enough to provide that reduced stress concentration points in the corners.

[Norman Bain]

... The purpose is a sliding fit over the shaft. Not automotive. Not a lawn tractor, but close. Want to use the augur drive on my snowblower as a PTO to drive a big "manual" winch. The input shaft on the winch is DD shaped...

More questions as to the layout:

* Is the winch to be attached to the snowblower.
* Is there to be a universal joint or two between the PTO and the winch.
* Is there expected to be need for some lateral movement in the driveshaft length.
* If there is to be lateral movement is that going to be managed in between the universals or at the DD connection.

I expect that the design will come out (evolve) as you work at it and the fitting at the DD shaft will become less of an issue.

To add to the options (hopefully without over complicating it all) ... it might an option to weld a different fitting to the male DD shaft. Not welding onto the shaft itself; but rather to the end of the shaft so that the weld on the coupling can be ground off to the remove that coupling later if needbe.

[wtrueman]

Even easier. Get a piece of the 1/2 inch flat bar used for concrete forms. Clamp it around the needed shape, tack weld and grind as nessary. I have used this for a quick fix. Good luck.

[ironmonger]

Drill a 1/2 hole is a suitable length of 1" round stock.
Make a tapered drift that has the desired cross section in the middle, for one time use it can be mild steel. I'd prolly make it .020" over size. (SWAG)
Heat the bored stock to a cherry red or a little hotter and drive the drift through the 1/2" hole.
Weld it to your shaft to drive the winch.


The profile, as far as the ends are concerned, looks like this






You will have to make the cross section look like whatever shape you want.
If you make the drift, bring it over and I'll heat it and drive it through for you

[alsinaj]

Norman: Good thought, but the input gear of the winch is driven by the DD shaft, so I don't want to change the end of the shaft in a way that would prevent me from removing the gear (which, in turn, would prevent me from disassembling the winch). It is a 2-speed winch, with speed selection being accomplished by sliding the input shaft longitudinally. On my snowblower, the "PTO" is an 8-inch v-belt pulley mounted on the augur assembly. The winch assembly, which will be a bolt-in replacement for the augur, therefore needs to include its own input pulley. Since the input pulley is stationary and the winch input shaft slides, there are two choices:
1) the input shaft and pulley don't move, and the rest of the winch slides sideways to change speeds, or 2) the winch and the input pulley don't move, and there is a sliding joint between the input shaft and the pulley. I've been working on solution 2) because I haven't yet thought of a way to mount the winch so it can slide accurately between two secure positions. Maybe I haven't thought about it hard enough.

Ironmonger: Thanks for reminding me that machining isn't the only way to shape metal. IMO, yours is the easiest solution so far, and at least as strong as the others.

[Norman Bain]

What is it you are trying to achieve. That is, are you creating a recovery winch (like a 4WD winch) or are you trying to create a mechanism to "tow" tree branches and the like towards the winch from places you cannot get to.

Regardless I have it the winch should be fixed; and fixed solid enough to handle the towing stresses. Seems like you will wind up mounting the winch inside the metal shroud where the auger once sat. Is that area strong enough?

How about a picture of the actual snowblower; or a link to one very similar.

[Arcane]

Why can't you mill it out with a 3/8" endmill? The rounded ends won't match, but the flats that transfer torque will be fine.

Mike

This would work as well as anything and is very easy to do on a mill. If you really have your heart set on matching radii on the ends of the slot, they do make 5/8" round files. Buy (or borrow ) one and grind two flats accurately on opposing sides so it's 3/8" thick and simply file the ends to shape.