Truss Screws: A custom application

[JSGAuto]

Hi All,

I am looking to make a truss head type slotted screw for a custom application, stainless steel. Of course I can't seem to find what I am looking for.

the screw would have to have a head of 20mm OD, with a 9mm sholder leading to a 6mm thread. The goal was to find a slotted screw that would meet the head size and have enough material to customize the part.

I have found on McMaster a truss head screw with a .823 head, which is a bit on the large size and would have to be turned down to fit this application. (although a bit on the pricy side)

Would you have any idea where to look for this sort of thing? Most of the catalogues/online don't list the head size. Or a better way to go about this?

Thanks
Jim

[Fasttrack]

How important is the head size and shape? Couldn't you get a coarse 10mm truss head screw and turn down the threads to give you a 9mm shoulder and then turn down the 6mm part and thread it? A 10mm coarse bolt gives a minor diameter of 9.06 mm so that should work. To get a 20mm OD you might have to turn down the diameter of the head, but as long as that didn't interfer with the phillips "cross", it shouldn't matter too much. Just a slightly different profile to the head.

Stainless is a pain to work with though... forming a 6mm thread on stainless might be tough.

You don't need a metric bolt if your going to remachine it anyway. Maybe you can find a 1/2 screw cheaper than the metric ones. The minor diameter on the 1/2" screw is 9.9 mm. I think its going to be tought to find such a big truss screw anywhere, though.

You may need to get an ordinary 6mm truss screw and thread a 9mm OD "spacer" to be your shoulder (you'd thread the inside of the spacer for the 6mm threads) or just buy some stainless stock and make one from scratch. Just make a conical head instead of domed and use a slittig saw for the slot.

[pcarpenter]

The adjustment screw for my Bridgeport Y feed nut was completely missing when I got my mill. It made it look like it had a completely worn out feed nut when in fact it and the lead screw had been recently replaced. These were a truss head with as I recall 1/4-28 thread and a head maybe .75 diameter and 3/16 thick. The head thickness and especially the diameter were critical as the head clamps on the end of the feed nut to squeeze the two halves together. There is also a second small screw, maybe 8-32 that overlaps part of this large head with its head. this screw locks the big one from turning (and falling out....it was missing too).

In any case, the diameter was critical and this was an odd item available as an overpriced proprietary item. What was not critical was that it was slotted. So, I took a 1/4-28 SHCS a little longer than original and turned a threaded washer the thickness and diameter of the original screw head and threaded it onto the SHCS, up tight under the socket head. Loctite or silver solder will hold it. I now reach in with a long allen wrench to do the adjusting instead of a big flat blade. I don't know if making one this way would work for your application or not.

Edit-- if it needs to be flush on top, you could even countersink the washer head a bit, running the socket head down into it a bit. Then chuck the works in the lathe and face off the excess socket if needed.

Paul