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Vice Jaw width dimensions

BT Fabrication

Titanium
Joined
Nov 3, 2019
Location
Ontario Canada
Well not sure if this is a dumb question, I have always wondered why the odd size widths and dimensions on standard 6” vice jaws?
5.969”, is it just my picky part of why isn’t it just an even 6”?
I could guess they are trying to save $ by using standard size stock and machining them down to size
 
ok, here's my stupid guess. If you start with a 12' bar and chop it into 6" lengths, you need to account for the blade width or the last one will only be about 5" long
 
I'm guessing it started based off metric dimensions. 151.5mm = 5.9646" then spec a tolerance of +/-.5mm? As I have jaws that measure from 5.960"-5.976"
 
But that then begs the question, "Why 151.5mm and not simply 150.0mm?"

Get real. They cut 6" pieces. Mill them to around 5.972" or 5.973" and then grind them to a final 5.969". That was probably how the prototype was made a gazillion years ago and that final dimension went on the drawing so every vise since then was made with jaws that size. No body in the US did metric back then. They barely use metric today.

A 12' piece of stock would be 144+ inches. Add the saw kerf for each 6" piece and they are 6.125" each. That gives 23 pieces with about 3.1" of scrap. They live with it or make smaller parts, perhaps for something else. That's one possible scenario, anyway.



I'm guessing it started based off metric dimensions. 151.5mm = 5.9646" then spec a tolerance of +/-.5mm? As I have jaws that measure from 5.960"-5.976"
 
I'm guessing it started based off metric dimensions. 151.5mm = 5.9646" then spec a tolerance of +/-.5mm? As I have jaws that measure from 5.960"-5.976"

LOL!.. "guesses" are about the only thing left in the modern economy as still go cheaply, ain't they?

Without leaving the keyboard... eleven out of - whups - seventeen - of my vises. In the US. And both in Hong Kong.. are metric made.

Damned if I can be bothered to go measure a single one of them though.
I just "run what I got". Same as wimmin'

What "problem" was the question meant to SOLVE, anyway?

Yah need to make a jaw, yah make it to fit the need. In ALL respects. Regardless.

Same as... n'er mind.
 
Well it’s much easier to measure 1” from each end manually instead of having all these fancy DRO options.
Maybe it’s just the carpenter experience, why measure over 5” when it’s easier to measure 1”, etc.
like when guys take a 4x8 sheet of ply to cut a 45 “ wide piece, they measure 45” over instead of just the 3” that come of because the sheet is exactly 48” wide.

Measuring over lets say 9/16 from each end is a pain if it was a 4” long part centered in the vice, now you have to remember the 0.031” difference on one side to the other if you lined it up with a 1” block from the one side.
Something that just made me wonder why.
 
Well it’s much easier to measure 1” from each end manually instead of having all these fancy DRO options.
Maybe it’s just the carpenter experience, why measure over 5” when it’s easier to measure 1”, etc.
like when guys take a 4x8 sheet of ply to cut a 45 “ wide piece, they measure 45” over instead of just the 3” that come of because the sheet is exactly 48” wide.
Well.. No. We measure WHICHEVER portion is OUR "critical need". Could be either one.

I don't TRUST a sheet of goods to be on-spec. Most especially if tongue & groove, damaged, maybe trimmed for some earlier tasking.

Likewise I might measure "relative" to a vise jaw at ONE end, but wouldn't confuse the jaw with a length-standard, otherwise. I have plenty of THOSE - rectangular gage block set extensions, not just rod-type standards or even "well known" parallels or ground blocks that one CAN trust.. but stil "vets" now and then, even so..

None of them get confused for vise-jaws, either.

Yah. I can see an advantage to it, some work, to make jaws or liners so they COULD be part of hasty setup measure - could even engrave them with divisions.

Mostly we keep metrology separate from workholding if only because it is not meant to "bear a load" in any way that might degrade accuracy, longevity, or both.
 








 
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