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Please help me to identify this bolt

avivz

Cast Iron
Joined
Jan 28, 2009
Location
Israel
The upper bolt is "normal" 3/8 UNC bolt.
The lower bolt is a machined bolt which came out of a milling vise that came with my Elliott Omnimil, however I don't know if it's original vice by Elliott or not.

The pitch is the same in both (16 TPI), same as for the major diameter.
In the blacl bolt, the hex head width is bigger by about 47.25 thou (1.2mm).

std. UNC nut will not fit on the back bolt, but the original nut which came with the black bolt will fit on the UNC bolt.

I succpect it's BSW, but a metric guy like me never came accross BSW screws :)

bolt.jpeg
 
It's hard to say with the damage to the threads on the black screw. Anything is possible. Your location is Israel. Could it be that UNC hardware is not very available and someone made their own replacement fastener?

3/8" is one of those weird sizes that doesn't have a close metric substitute. M10 might not even fit the hole. M8 will be very very loose fit. It's basically the whole next UNC size down--5/16.

A custom made screw would be my guess. The marks on the hex suggest that was hex bar when it started and maybe that's just what they had.
 
This predicament frequently arises in machinery produced prior to 1970, it amplifies significantly when handling top-tier machines and virtually becomes a guarantee if the machine hails from European origins. To put it plainly, in the economically fragmented world before the 1970s, where global competition was rarely feasible, companies had the luxury of crafting their own fasteners, tailored precisely to their requirements. In practical terms, this implies that if you were to crack open a 1950s European lathe, you'd encounter peculiar pitches, and unusual dimensions, all entirely foreign to today's standards, but adapted to its role in the machine. So yes you can call it "custom", but not random either since it is from the manufacturer's standards, which are probably somehow accessible.

Since they frequently made their own fasteners it is also possible that they tried to follow a specific standard, but lacked the ability to repeat the standard accurately in a production setting. (so just a shit bolt)
 
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The upper bolt is "normal" 3/8 UNC bolt.
The lower bolt is a machined bolt which came out of a milling vise that came with my Elliott Omnimil, however I don't know if it's original vice by Elliott or not.

The pitch is the same in both (16 TPI), same as for the major diameter.
In the blacl bolt, the hex head width is bigger by about 47.25 thou (1.2mm).

std. UNC nut will not fit on the back bolt, but the original nut which came with the black bolt will fit on the UNC bolt.

I succpect it's BSW, but a metric guy like me never came accross BSW screws :)

View attachment 408768
Strange, in my long UK experience BSW and UNC nuts and bolts were fully interchangeable. If the original black bolt is .375" in diameter the thread doesn't seem to be cut to full depth as there is quite a bit of land on the outside diameter, that would explain why a UNC nut doesn't fit.
Tony
 
To be Whitworth the roots and crests of the threads should be round. In something like a machine tool, I'd expect a produced Whitworth screw to have proper form. Judging from the flat but, too-wide crests, it looks like UNC that was not cut deep enough.
 
Many great answers. Some more info-
These bolts are used to tighten the vise body to the swivel base. So most of the thread except for the end is untouched. As the bolts come with a set of washers and nuts of the same black colour, knowing local machinery in Israel no one would bother to do so. It seems to be original.
The upper part of the thread is unattached, so the lightly flat crest seems to be original as well and not flattened from damage.
The idea that the bolts were paired with M10 nuts seems to be correct. I just checked and M10 nut will go all along the damaged part of the thread (also makes sense in local terms :( )
The hex is in exact size to fit a the slot in the base of the swivel. Standard UNC 3/8 bolt cannot be used as the hex is too small. Luckily, M10 bolt will fit into the holes, so I just need to cut down the hex to fit in the slot. This seems to be the easiest solution.
Another option would be ordering std. BSW 3/8 bolt which seems to have exactly the right hex size. However, these are not available locally and would cost much more. Any other ideas are welcome.
 
Many great answers. Some more info-
These bolts are used to tighten the vise body to the swivel base. So most of the thread except for the end is untouched. As the bolts come with a set of washers and nuts of the same black colour, knowing local machinery in Israel no one would bother to do so. It seems to be original.
The upper part of the thread is unattached, so the lightly flat crest seems to be original as well and not flattened from damage.
The idea that the bolts were paired with M10 nuts seems to be correct. I just checked and M10 nut will go all along the damaged part of the thread (also makes sense in local terms :( )
The hex is in exact size to fit a the slot in the base of the swivel. Standard UNC 3/8 bolt cannot be used as the hex is too small. Luckily, M10 bolt will fit into the holes, so I just need to cut down the hex to fit in the slot. This seems to be the easiest solution.
Another option would be ordering std. BSW 3/8 bolt which seems to have exactly the right hex size. However, these are not available locally and would cost much more. Any other ideas are welcome.
How expensive could it possibly be
 








 
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