"half-dollar"/"50 cent piece" Was: Recovering the ROM of an IBM 5100 using OCR

Fred Cisin cisin at xenosoft.com
Mon Jul 1 17:11:51 CDT 2019

> Oh, but we are proud of our unremembered heritage, and fiercely resist
> change.  We still use Fahrenheit.  And efforts to "go metric" have made
> little headway.

On Mon, 1 Jul 2019, dwight wrote:
> Not every thing makes sense to go metric. Clearly bold sizes are better 
> off in fractional sizes. Also for wrenches. I have to have 13, 14 and 15 
> mm wrenches. A 9/16 would have covered the entire range. I have a spot 
> on my car that I need a 23mm offset box wrench. What a pain.

I find that an SAE set of wrenches and a metric set of wrenches tend to 
need similar quantities.

German cars switched from 14mm to 13mm heads for 8mm bolts about 5 
decades ago.
Japanese use 12mm heads on 8mm bolts, and 13mm and 15mm are rare on 
Japanese cars.
Unless you are dealing with vintage stuff - 10,13,15,17,19 for German 
cars;   10,12,14,17,19 for Japanese cars
16mm, 18mm seem rare.  Whitworth is finally rare
Yes, once you get above an inch, sizes are less standardized.

9/16 doesn't cover everything.  It could, if you provided appropriate 
punishment for any use of a 17/32 or 19/32 bolt head.
1/4-20 bolts use 7/16" heads, which is about 11mm.  But lately, I have 
encountered some 1/4-20 with 10mm heads!   (Chinese specification change)

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