Thumb screw

I’ve often thought it might be handy having one with a hex socket in it for some projects but couldn’t think of a durable way of securing the two parts. How do you think this may have been done, just glued/thread locked together?

That would seem the obvious choice

MichaelG.

If they are both metal, they could also be silver soldered/brazed or welded, depending on size.

Arbour pressed? couple of tons

edit, handy idea btw

Edited By Ady1 on 21/09/2023 19:34:51

The thumb screw looks thicker than the head of the screw. So drill and tap to the knurled rod to suit thescrew size and then counterbore for the head. Screw the screw into the thread with some Loctite and jobs a good un

90% of off-the-shelf socket capscrews are straight knurled on the outside of the head for the top 3/4 of its depth. Make the counterbore the same size as the un-knurled portion of the head and press fit together. It would act like a rudimentary splined joint.

It may but if the 1/4 of the height not knurled is that at the bottom of the head, pressing it in might broach the hole to the o.d. of the knurling, so rather defeating the object.

I'd be inclined to tap the hole through the knob and screw the Allen screw into it with hard-setting thread-lock on both thread and knurled bit, ensuring none ends up on the working part of the shank.

Yes agreed, the bottom part of most high tensile cap head socket screws (that isn’t knurled) is the widest part. I use mainly stainless ones though and I’ve never seen one that was knurled. I think I tried knurling one years ago and pretty sure the attempt failed. Maybe it’s time I tried it again?

It must depend partly on the manufacturer. I have a large number of recently purchased M4, M5, and M6 stainless cap screws that have knurled caps, among others of the same diameter that are not knurled. Some of the knurled ones have a manufacturer’s mark: “THE”.

I think I’m right in saying that grade 8.8 cap screws tend not to be knurled, whereas the 12.9 ones do. I’m not sure about grade 10.9 ones, as I don’t have any I’m aware of.

Both milled and non-milled types are available in stainless steel, frequently from the same manufacturer although not many suppliers seem to offer both types.

The use tends to depend on the preference of the purchaser. Non-milled are frequently specified where the heads will be on display, e.g. on the face plate of electronic equipment, and are often polished. Milled seem to be more often used in machinery - cars, motorbikes, outboard motors etc. Perhaps this is so you can get hold of them with a pair of multigrips when you don't have the correct size hex key available . Sorry Sir it wasn't me .

Make the screw, straight knurl the outside and create the hex socket with a rotary broach.

But then I have already made my rotary broach.

regards Martin

I would be inclined to drill down the joint between the head of the cap screw and knurled outer piece and lock the two together with a suitable size of pin.

Brian

Hex heads are tuff, If I have to turn one down I use carbide

Surely there's no need to go overboard on this? Just how much torque is a thumbscrew expected to apply? I would have thought that there was sufficient grip between the knurled part and the socket bolt by the application of Loctite or similar or press fit or even heat/freeze fit. But then, I've been wrong before and will, no doubt , be again.

Like Martin Kyte, above, I'd make it in one piece and then broach the socket afterwards if integrity is an issue.

John

I did something similar for the gib locking screw of my Centec mill. The BSW socket headed locking screw for the Y-axis is rather long and inaccessible, making it rather cumbersome to use with a standard hex-key. I made the illustrated extension from a lump of aluminium. The mating part is a round force-fit into the hex socket, which works very well.

If you watch from about 18:30 this is how this chap makes his.

Edited By Dalboy on 22/09/2023 11:02:37

I must have nearly a thousand cap head socket screws in M2.5, M3,M4, M5, M6 and M8 in stainless steel, some of them marked THE and none of them are knurled. I’ve actually never seen one before. I use mainly Kay’s, Boltbase and GWR. I should add that I generally only use Metric fasteners so perhaps that’s why?

All my stainless cap screws, whether knurled or smooth, are metric.

I should add that I’ve not been overly impressed with the quality of the knurling on most of the High Tensile (Black) socket screws I’ve bought in the past. Poorly formed and not very deep. The exception to this were those manufactured by Unbrako and the straight knurling on them was a piece of art in comparison.

Here’s an Unbrako knurled A2 skt head cap screw: