Crankshaft oil plug screw

APRRSV · Oct 4, 2020

Hi all,
I wonder if anyone knows whether this oil plug set (grub) screw, timing side crankshaft, is available somewhere with an allen head instead of the flat slot screwdriver head. It is Norton part # NME4591 or new # 067600. I quickly buggered mine trying to remove it and had to drill and blast

. It is 1/4 x 26 tpi. Not sure of the thread angle.

Thanks,
Ed

kommando · Oct 4, 2020

A 1/4 BSF allen grub screw is 26 tpi but wrong thread angle, out by 5 degrees. Its not doing anything but blocking off the end of an oilway so use a sealent on the thread.

APRRSV · Oct 4, 2020

kommando said:
A 1/4 BSF allen grub screw is 26 tpi but wrong thread angle, out by 5 degrees. Its not doing anything but blocking off the end of an oilway so use a sealent on the thread.

Thank you Kommando for the quick reply. Are you saying that a 1/4 BSF will thread in even though the thread angle is incorrect?

Ed

kommando · Oct 4, 2020

Should do, if it feels a bit tight then that's better anyway. I suspect most 1/4" cycle bolts supplied nowadays are cut 1/4" BSF.

tonybsa · Oct 4, 2020

If BSF is 5degrees out on the thread angle.Then the correct angle is 60 degrees,which if I remember right makes the correct thread UNF,as it is the only imperial thread with a 60 degree angle(same as Metric).the rest are all 55 degrees.

L.A.B. · Oct 4, 2020

tonybsa said:
If BSF is 5degrees out on the thread angle.Then the correct angle is 60 degrees,which if I remember right makes the correct thread UNF,as it is the only imperial thread with a 60 degree angle(same as Metric).the rest are all 55 degrees.

CEI/BSC (Cycle) thread is 60 degrees.

1/4 UNF is 28 tpi.

APRRSV · Oct 5, 2020

If anyone is interested, I found 1/4BSF x 1/4 Allen head grub screws at BA Bolts in UK. 37 pence each.

Ed

Crankshaft oil plug screw

APRRSV

kommando

APRRSV

kommando

tonybsa

L.A.B.

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