From: Fred Martin (mung@in-touch.net)
Date: Fri Apr 25 2003 - 14:47:05 PDT
Well, Ryan, if you want to talk about thread strength, why don't you
mention about the buttress thread...it is about a 45* on one side and
straight on the other side. Have you ever taken that old american made
vice of yours apart to oil the threaded shaft in it? Well, a lot of 'em
had butress threads because they don't get any atronger than that...or
maybe you bought one of those foreign made ones...grin...they won't have
them. Another one is the square thread (read strong) and the modified
square thread which we call an acme. Some of the vices have it...and
other things as well. We used to have to cut those acme threads in the
bonnet (I think thats what we called it) of certain valves...sea water
fire valves to be exact and they had a double pitch...in other words two
threads wrapping around the shaft or inside of a hole. We always knew
when one of those jobs came in the shop (older fellows) and if they
assigned it to one of the young hotshots...some dude would wait till he
was cutting inside of the hole and would take a 4 pound hammer and toss
it in the air to land behind him on the steel deck. You better not be
grinning when he turns around. Of course...no one knew anything. <G>
Fred Martin
Ryan M Gill wrote:
> At 3:40 PM -0400 4/25/03, Fred Martin wrote:
>
>> Ryan...thats fine if someone wants a Brit car or a French car (I think
>> they have a system called Lowenhurst(sp)in France) and if you get out
>> the machinists handbook and look, there are other systems. Some of the
>> engine lathes of today will cut SAE, metric and a system called
>> modular...I don't know about this system... But we are
>
>
> Whitworth is inherently stronger as it has better stress curves on the
> threads compared to SAE. Its curved across the roots and crests of the
> threads. Both BSF and BSW have a 55 degree pitch (UNF and SAE don't!).
>
> I don't really see how different thread rates make things hard. There
> are short and long tons still now. People still sell wood by the cord,
> wheat by the bushel, Nautical speeds are still Knots (not KPH) and most
> things are still measured with ounces, pounds and tons.
>
> Metric isn't inherently better in any respect as far as measurements go
> excepting for the ability to do easier math (is that a bonus or does it
> promote dumb-ing down?).
>
> Perhaps I have to think in so many modes (there's also BA/British
> Association for small machine screws) that I don't see the difficulty in
> also thinking in metric when I'm working on my Honda's (3 Hondas, 1
> Subaru, 1 Chevy, 2 Daimlers, and a shared Humber).
>
> To me, all it really means is that I need more tools...
>
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