Hearnshaw 5/32 sash mortise chisel ?

[Ray Selinger]

At the fleamarket I picked a couple of what I thought were 1/8" mortise chisels.One of them I bought as a bundle, MillersFall #14 jack,a tanged E.A.Berg 1" bench chisel and a sash mortice chisel for $25 When I got home I looked closely at my finds. The English Hearnshaw instead of being 1/8" was 5/32". I don't think that size was mistake, rather it was deliberate.It's a well made chisel, with the classic English pattern beech handle and a octagon flare on the tang. I worked as a millwright and we did some welding, from a distance you could see the difference between 5/32 and 1/8 welding rods. So the toolmaker was likely aiming for that size.Any special reason for that size? It took some googling to find Hearnshaw. 1871-1958

[John Schtrumpf]

I have no clue, but I use a 3/16" mortise chisel for 5/8" thick stuff. So maybe a 5/32" chisel is used for 1/2" stuff. :D

[John Vernier]

I have a reprint of the 1889 Sheffield list, which was a standard illustrated price list used as a wholesale reference for all of the Sheffield edge tool manufacturers. Under mortice chisels (sorry, mortice with a c in this case), it lists 1/8 and 3/16 sizes, but not 5/32. Is that definitive? Not really, since individual manufacturers could make unusual products, or make to special order. On the other hand, I have a fair selection of older English chisels - firmers, paring and mortise chisels - and they rarely are sized to accurate 1/16 increments, although that seems to be how they were sold.

I've heard that edge tools were ground to size by eye, so the measurements were merely nominal. I know what you mean about the toolmaker being able to see the difference between 1/8 and 5/32. I used to do quite a lot of work with sheet metal, and you develop an eye for very small increments after a while; but that doesn't mean they were necessarily trying to hit exactly the numbers we think they were. I wonder if tools were intentionally left on the fat side, so that a user could, if desired, grind to a precise thinner size if needed. It might be handy to have firmers, mortise chisels and plow plane blades which match, for instance, but only the very fussy workman would go to that trouble. On the other hand most of the time the exact width of your chisels (or of your mortises) isn't important within 1/32. I was taught to always cut mortises first, then tenons, because whatever the size of your chisel (or your hollow-chisel mortiser or your router bit), you go with it and cut your tenons to fit.

[Mike Henderson]

Most of the older chisels that I have are nominal in size. That is, a 1/2" chisel is never really 1/2" - it'll be a bit larger or smaller. It's only the modern chisels that are accurately sized. I doubt if that chisel was intended to be 5/32". It was probably intended to be 1/8" (4/32").

I just went and checked the sizes of a set of Ward Pigsticker mortise chisels that I have. They measured out as follows: (all of these chisels were probably made in the late 1800's)

5/32" (which would be used as a 1/8")
7/32" (which would be used as a 3/16" or maybe a short 1/4")
1/4 +1/16" (which would be used as a 1/4")
3/8 + 1/128" (which would be used as a 3/8")
3/8" exact
1/2+1/16" (which would be used as a 1/2")

Apparently, they just couldn't make the chisels that accurately, or it didn't matter that they weren't exactly accurate.

Mike

[I also have a set of Swan bench chisels and a set of Witherby bench chisels (both antique). They are all nominal in size.]

[Jim Koepke]

Just to throw a little jam in this sandwich, 5/32"=4mm. Maybe it was sized to sell to the market on the continent.

My recollection is England didn't go metric until the late 1960s.

Most likely it was just because exact size wasn't an important feature.

jtk

[Mike Henderson]

I traveled to England quite a bit in my job. There were a lot of imperial measurements still being used. I wonder if they'll ever go completely metric. Here's (https://en.wikipedia.org/wiki/Metrication_in_the_United_Kingdom)a Wikipedia article about it.

Mike

[Ray Selinger]

Thanks. If the chisel had been a Marples, I would have said it dated from between the wars or earlier. I have seen chisels that were off size, I have a poorly made, you could tell by the uneven bevels, an unnamed Swedish socket chisel that was intended to be 3/4":D Even the Swedes screw up. It was meant to be that size, it's bang on.Since it's sash mortise, I was wondering if there was a glass thickness size ? I guess it's a question answered by someone a couple of generations back.The questions around old tools are fun.