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Jaw pins on a 974 1/2 B Parker vice

Paul1963

Plastic
Joined
Nov 22, 2023
I'm new here And I have this 974 1/2 B vice And the jaws have the 2 pins. But they look like nails. And I want to know what type of material the pins should be. I would imagine a hardened steel. So I want to learn What exactly should be done to keep these jaws secure on the vice?
 

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How and what the pins are made of is determined by what Parker originally designed. Ideally, the pins would fit solidly with what is known as a 'body bound fit". This would mean the jaws and jaw plates were likely line-reamed together when the vise was made. Or, very good drill jigs were used when the parts were made so the holes lined right up. I would check to see if the holes for those pins are line-reamed thru. I would also check to see if the holes are not reamed for tapered dowel pins.
Tapered dowel pins would have the big end on top, and the taper of the pins wedges tight. I.E., the taper pins are 'self retaining'. Some investigation with drill shanks or other round steel rod to determine hole diameter and whether the holes are tapered is the first step.

If the holes are tapered, tapered dowel pins are standardized. As long as the tapered holes have not been damaged by loose pins/hard usage, getting replacement pins can be done easily. First off, determining taper pin size has to be done, and information from a "Machinery's Handbook" or online will put you on that track. Getting the pins is something done thru McMaster Carr. Tapered pins would tend to draw the jaw plates into seating on the vise jaws and lock them in place.


If you find the holes are straight bores, no taper, it remains to determine the size of the hole. I use Starrett "small hole gauges" and a micrometer for this sort of measurement. The small hole gauges are expanding balls that capture the diameter of a hole. You then use an outside mike to get the hole diameter. This measurement is important as the pins for the jaw plates have to be a solid fit. I suspect the jaw plates (serrated parts) are hardened, and the vise jaws are cast malleable iron (soft). If someone was using the vise with a loosely fitted pin(s), heavy work and movement of the jaw plates relative to the jaws could do some damage to the holes in the cast jaws for the pins, though probably not too likely.

If the holes are straight bores (no taper) and micrometer readings show them to be a common size (decimal equivalent of a fraction of an inch such as 0.250"), then I'd make the pins out of drill rod. Drill rod is precision ground tool steel. I'd get a piece of O-1 drill rod and make the pins from that. File or turn a chamfer on the bottom ends of the pins so they 'find their way in' easily. At the top end of the pins you can go with what some old time mechanics called a 'Boston Fit'. Take a sharp center punch and put a few light punch marks in the top 1/4 to 3/8" of pin length. As you drive the pins home, the raised metal around the punch marks will lock the pins in place. Leave a little extra pin length projecting beyond the tops of the vise jaws. File this off flush to match the curves of the jaws. Done.
 








 
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