Plane screw

[Speedy Builder5Participant @speedybuilder5]

Just been asked to make a 7/32" 20Tpi BSW screw for a STANLEY wood plane. No real problem, screwcut then chased.

Question. Why would a manufacturer choose 7/32" x 20Tpi when the norm for this size is 24Tpi. Admittedly, the thread was in cast iron, but then, that was one of the reasons for the BSW verus BSF ?

7/32" was a non prefered size as it jumped from 3/16" to 1/4"

BobH

[Speedy Builder5Participant @speedybuilder5]

Peculiar Whit screw

[Clive HartlandParticipant @clivehartland94829]

Screwing into cast iron the coarser the thread the better, a finer thread is easily stripped out.

Much the same as in aluminium, a fine thread will be pulled out if under load whereas a coarse thread will hold in the soft metal. Of course Stanley have done this thread from year dot so why should they change it, if it breaks or is lost they have you for an expensive replacement or as you are doing making one.

Clive

[JasonBModerator @jasonb]

Actually its a fraction smaller than 7/32" they used #12-20 which is 0.216" and 9/32"x 24. You can buy taps and dies in these non standard forms from some of the specialist handtool suppliers.

Have a read of this PDF all about their threads

Edited By JasonB on 15/10/2013 18:34:12

[Andrew Moyes 1Participant @andrewmoyes1]

Record did it too…

**LINK**

Andrew M

[Speedy Builder5Participant @speedybuilder5]

Thanks for the info guys – You can always rely on someone on this site coming up with the answer.

BobH

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