Making a "Cruciform Key" (4 sided)

I recently bought a used steering-wheel lock (a generic brand like The Club). It came with one key, I'd like another. As shown in the picture, this uses a 4-sided key. Visited a local locksmith, who told me it's called a cruciform key. He could not cut one, nor even find a blank.

With my lathe and mill, I could easily make a blank, but he was [for some reason?] not allowed to cut keys using customer-supplied blanks. Given that I only paid $3 for the club and key, I'm not planning to pay many times that for custom locksmithing.

So, amidst all my other projects, I reckon I'll make my own key from a scrap piece of 3/8" steel rod. I'll do some CAD drawings, which can also provide me templates for each of the four unique blades' notches. Turn the rod to the major diameter, mill to make the blades, then mill/file to do the notches. Asked the locksmith about required tolerances; he thought it wouldn't need real precision, about 5 thou.

Before I start, any comments/suggestions?

Greg

It'll be an interesting project. I have cut my own keys in the past but I started with pre-made blanks.

It doesn't look like there is any complicated warding involved, cross shaped cross section aside. You might look at obtaining/ making a cutter similar in profile to what the commercial machines use. A Woodruff key cutter would be a good starting place. Other than that, you just have to replicate the position/depth of each cut. The width shouldn't be too critical. Should you over-cut one position, You can fill in with solder or braze. You might actually want to use brass rather than steel as it will be easier to work. If you have some machinist's wax, you could make an impression of the original to check your cut.

I am more confused that the locksmith could not make it. Looks more like à pre year 2000 locksmith. Could not even order it with his suppliers. Weird.
Wether à key is one, two, or three sided four sided should Not mak à technical difference, just rotating the key in the clamp would be enough.
I made keys even with needle files in à distant past. I would say just follow the normal lathe or milling procedures an you would be Ok mak is from harder material than your averige, hard brass would be recommended.



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When I took a correspndence locksmith course in the early 70s, one of the exercises was duplicating a key with a small round file. Just not that big of a deal.

Thanks! All good points. I've considered brass, maybe I have some on hand.
Not all that much metal needs to be removed when cutting the wards, so I'll likely use a narrow slitting saw to mark the ward positions and depth, then Dremel cutting disk and needle file to final shape - using template wax and/or the wax method RJ suggests.

I have a couple of locks by Papaiz (Brazil) like that, note that one leg of the cross is thicker than the others, which makes it easier to get it in the right way around first time (on the Papaiz locks the four sides are different)

Dave H. (the other one)

If you can make a functioning blank, go ahead and cut the key with a needle file as close as possible, Ink it then twist it in the cylinder looking for where a pin is hitting the blank. Continue this until it spins and your done. Impression cutting is quite difficult. I imagine that a four sided key might make it nearly impossible, so hopefully your initial trace and cut will work. Otherwise, call the company, give them the serial number, and perhaps they'll sell you a key!

Thanks, Jonathans, I was already thinking of doing your ink method. And there is no serial number or company. This was a cheap Chinese generic club that I got at a second-hand store, so I'm on my own.

wawoodman said:

When I took a correspndence locksmith course in the early 70s, one of the exercises was duplicating a key with a small round file. Just not that big of a deal.

Click to expand...

I did that too. Still have the stuff in the upstairs closet.