Hello Drains,
"All this is soooo much easier than using Whitworth sizes, which bear absolutely no relation to the real size,"
You mean that 5\16 BSW isn't a 5\16" fastener? And better still the spanner size is what the bolt diameter is (As long as you read the BSF size so a 5\16"BSF spanner fits a 5\16" BSF or BSW fastener (Unless you come acros pre-war fasteners which use a spanner marked 1\16" larger.)
I hold my head in shame!
......I do recall conversations with old engineers about wartime head sizes being smaller, as an austerity measure (whilst raking through old boxes of bolts and coming across vaguely wrong-looking ones)- just BS then?
Which idiot thought of the imperial numbering for BA threads and the drill sizes, its opposite to everything else, largest drill size 1 is the largest approx 1/4" dia, number 60 drill is small.
You need to drill a hole in imperial, you need to have a butchers at chart to find the drill size!
Unfortunately i have to work with both.
Fine Thread Vs Coarse Thread
Fine threads have a larger Tensile Stress Area than coarse threads.
Example 1/4-28 - 0.0364
1/4-20 - 0.0318
Everything else being equal - bolts with fine threads are stronger in tension than bolts with coarse threads.
Fine threads are stronger:
Quote:
Fine Thread Vs Coarse Thread
Fine threads have a larger Tensile Stress Area than coarse threads.
Example 1/4-28 - 0.0364
1/4-20 - 0.0318
Everything else being equal - bolts with fine threads are stronger in tension than bolts with coarse threads.
http://www.mechanicsupport.com/artic...eStrength.html
Reply With Quote
Oh never mind
Didn't realise the different head size was a war thing. I've only had experience of BSW/BSF threads on my Rileys made from 1946 to 1955, UNF & UNC were creeping into British Cars from the mid fifties. Landrover were still using BSF in the 1980s. From what I've seen BSF heads were one set of sizes, it was the Whit screws that had different heads. Also a Whit nut could be a different hex. size to the bolt it was screwed on to. I was told this was so you could use both ends of the spanner at the same time.
My first set of spanners, Elora, bought in 1968 were marked in BSF & Whit sizes. AF (for UNF/UNC) were also in the shops but metric unheard of.
That was the very early (1948-1950) series MM cars with the sidevalve engine. The A series engined cars have the typical A series AF UNF thread imperial fixings on the engine and BSF on the body (seat, door hinge, wing bolts etc). Plus some BA screws! Oh, and past owners have added metric to the mix too.Hello all,
seeing the reference to Morris; at one time, due to buying a French engine company, Morris engines had metric fasteners but with Whitworth head sizes. Confusing?
Alec
That was the very early (1948-1950) series MM cars with the sidevalve engine. The A series engined cars have the typical A series AF UNF thread imperial fixings on the engine and BSF on the body (seat, door hinge, wing bolts etc). Plus some BA screws! Oh, and past owners have added metric to the mix too.
I've even seen woodscrews used holding metalwork together