How do I attach something to a square shaft???

set screw, roll pin, small screw in from the end. the trouble may be the square hole.

Easy with a matching square hole and a set screw.
Use a deep well socket for the hole (which track you were already on) and match the O.D. of the socket to the round hole in what you want to attach.
If you want to drill and tap a set screw hole in the socket you will need to heat it with a torch to anneal it first.
Otherwise you might also just drill a hole for a roll pin to attach it, but this would require a hole in your shaft.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

You could still put a normal round hole hand wheel on it. Just buy one with a hole slightly larger than 1/4”. Or buy a 1/4” hole and drill it out to the exact size that will slip over the square.

-- Steve

Grizzly.com has some handwheels with and without holes in them. You can get one with a 1/4” hole, or
drill a hole and use a good small triangular file to make the hole square and fit over the shaft. Reid supply.com
also has quite a bit of interesting hardware.

-- As ever, Gus-the 75 yr young apprentice carpenter

This isn’t a wheel or crank but the A/C business used a wrench that had a square hole in it to open valves for many years. It has a ratchet mechanism in the end. Turn it over to reverse.

http://www.hardwareandtools.com/Valve-Keys-and-Handles/

-- http://lawoodworking.com

Yes Loren, I was just about to suggest valve wheels, but you beat me to it.
The McMaster Carr folks have these as well; for more money of course.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

Crank has the idea. Just use a Square Hole drill bit and problem solved!

http://www.bing.com/videos/search?q=square+hole+drill+bit&FORM=HDRSC3#view=detail&mid=2E737F5A32845A3E3A362E737F5A32845A3E3A36

-- HorizontalMike -- "Woodpeckers understand..."

You might be able to find something here
I have used this company a few times with good results, they have lots of good stuff.

Find one of these in the size you need and weld what ever handle you want on it.

-- Perform A Random Act Of Kindness Today ... Pay It Forward

Maybe one of these will work.

http://www.mcmaster.com/#hand-wheels/=ozxcnl

-- Tom Finnigan - Measures? We don't need no stinking measures! - Hmm, maybe thats why my project pieces don't fit.

Thank you for all the suggestions!

Well, Reids and McMaster don’t have hand wheels with 1/4” square holes, only with round holes. I could get one with a slightly smaller round hole and file it straight. Sounds like a work-around in a way though… there must be a better solution.

Drilling a square hole—that video was great, I don’t quite understand how it works, but if a square-hole-drill really exists, I will go for it (could even make mortises with it??).

Then again, using a 1/4” square socket and welding something on it, that sounds like the most reasonable solution. I just don’t have a welder… maybe I could ask my old teacher to help me do that.

I have looked at valve wheels, but I really would prefer something that’s larger and easier to turn.

I sent an email to Carrlane, who make handwheels with optional custom holes… no 1/4” square is listed officially as an option, but they may just do it for me.

Ideally I would prefer a hand-wheel that just fits, as opposed to mocking something up. $20-30 is not the end of the world for a custom fit hand-wheel that will sit tight as opposed to some mocked up version that may not sit well….

the square hole drill does exist lol but it would be quite an investment in tooling for one hole. get a blank handwheel from any one of several suppliers drill a 1/4” hole. take a piece of 1/4” keystock and round an short section of one end for a pilot. heat it up hot enough to melt the material you are working with and push it through the hole. drill and thread the handwheel for a set screw. how big

I wonder if there is another line of logic you can follow here. Just how much cranking force is required to move your linear slide? Is your box joint jig going to require that much force to advance? I assume, perhaps wrongly, that the forces acting on the handle would not be that great as to require a steel handle. Would not a crank made of a good hardwood carry the necessary forces? You could incorporate the quarter drive socket easily or a mortise combined with an opening saw kerf and a couple of counter bored nut and bolt sets. A carriage head bolt and nut set towards the business edge of the crank which is fitted with a knob or handle would be a nice addition for ease of turning as well as a rough visual marker as to the crank turn amount.

Talk to a machine shop about what you want. If you have a well equipped shop in your area they might be able to broach that 1/4 inch hole for a reasonable amount. If you can’t get a shop with a broach, have a socket modified and welded to the wheel. When you buy the wheel make sure it is something they can easily weld and want to weld. If the socket were shortened and drilled before the weld procedure it would probably be easier. by shortening the socket it would make the wheel more stable. If you can get Carrlane to make it then it would probably be the cheapest.