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St. Lawrence bolt threads

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jb_castagnos
Senior Member
Username: jb_castagnos

Post Number: 697
Registered: 07-2002


Posted on Monday, June 18, 2012 - 05:04 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

George Coates repaired a cylinder for us, the damage was in the threaded area for the head stud. I don't have it back yet. He said it's not 7/16th x 14, possibly metric. 7/16th is 11mm, I was wondering if they used metric or whitworth threads. Anyone ever had to replace a bolt on them?
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todd_vidgen
Senior Member
Username: todd_vidgen

Post Number: 228
Registered: 03-2008
Posted on Monday, June 18, 2012 - 05:42 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Hi JB
There are 3 11mm metric threads that I know of
Metric Coarse 11x 1.5
Metric Fine 11x 1.0
11x 0.75
Metric coarse works out to about 16.6 tpi
Is it possible that some one back in the mists of
time has inadvertently "cleaned up" the stud holes
with the wrong tap?
Cheers ,Todd
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bcm
Advanced Member
Username: bcm

Post Number: 31
Registered: 11-2009
Posted on Monday, June 18, 2012 - 05:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

JB,

I've replaced head studs on many St Lawrence engines, all 7/16x14tpi.

Barry
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jb_castagnos
Senior Member
Username: jb_castagnos

Post Number: 698
Registered: 07-2002


Posted on Monday, June 18, 2012 - 06:04 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Thanks Todd, I don't have the cylinder here yet, George told me 7/16 wouldn't screw in but 1/4". I know whitworth uses a different thread angle, I believe 55 degree, thought maybe that's what they used.
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jb_castagnos
Senior Member
Username: jb_castagnos

Post Number: 699
Registered: 07-2002


Posted on Monday, June 18, 2012 - 06:11 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Barry, did the studs screw in easily or did they have to be forced in? When I put the exhaust adapter on my St. Lawrence I used 5/16th bolts, I remember them being tight, ran a tap through them. I've never dealt with whitworth, I'll have to search and see how close they are to standard bolts.
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jb_castagnos
Senior Member
Username: jb_castagnos

Post Number: 700
Registered: 07-2002


Posted on Monday, June 18, 2012 - 06:29 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Below is a chart with Whitworth threads. 1/2" uses 12 threads per inch instead of 13, the thread angle is 55 degrees which should make the depth of thread a little shallower, making them hard to screw all the way in. Did Canadians use Whitworth?

Whitworth size (in) Core diameter (in) Threads per inch Pitch (in) Tapping drill size

1/4 0.1860 20 0.05 Number Drill 9 (5.1 mm)
5/16 0.2414 18 0.0556 Letter Drill F (6.5 mm)
3/8 0.2950 16 0.0625 5/16 in (7.94 mm)
7/16 0.3460 14 0.0714 Letter Drill U (9.3 mm)
1/2 0.3933 12 0.0833 Letter Drill Z (10.5 mm)
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bcm
Advanced Member
Username: bcm

Post Number: 32
Registered: 11-2009
Posted on Monday, June 18, 2012 - 06:35 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

JB,

This is a new and interesting subject.

Whitworth is also 7/16 x 14 same as UNC, difference is 55 vrs 60 degree angle.
It's possible that St Lawrence,a Canadian Company employed British threads in 1905 thus used Whitworth.

As I think about this, I probably chased the threads with a UNC tap.

Barry
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bcm
Advanced Member
Username: bcm

Post Number: 33
Registered: 11-2009
Posted on Monday, June 18, 2012 - 07:31 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

JB,

St Lawrence probably changed to UNC at a later date, maybe 1920, thus my engines are UNC threads. If yours is an early St Lawrence, probably used Whitworth ... same tpi as UNC , different thread angle.


Barry
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jb_castagnos
Senior Member
Username: jb_castagnos

Post Number: 701
Registered: 07-2002


Posted on Monday, June 18, 2012 - 08:13 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

This is one of the very early engines, drip oiler, rear timer.
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bcm
Advanced Member
Username: bcm

Post Number: 34
Registered: 11-2009
Posted on Monday, June 18, 2012 - 08:50 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

JB,

Probably Whitworth.

Barry

http://www.britishfasteners.com/index.php?crn=262&gclid=CO6ftNaJ2bACFUgDQAod0CFh 3A
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jb_castagnos
Senior Member
Username: jb_castagnos

Post Number: 702
Registered: 07-2002


Posted on Tuesday, June 19, 2012 - 12:46 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

It would be interesting to see if they used Whitworth, if they switched, and when.
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bcm
Advanced Member
Username: bcm

Post Number: 35
Registered: 11-2009
Posted on Tuesday, June 19, 2012 - 03:03 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

JB,

All my older St Lawrence engines, probably 1920s are UNC.

Interesting reading here: I think this supports the notion that St Lawrence used Whitworth at the beginning, maybe other Canadian manufacturers as well.

http://en.wikipedia.org/wiki/British_Standard_Whitworth

Barry
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bcm
Advanced Member
Username: bcm

Post Number: 36
Registered: 11-2009
Posted on Tuesday, June 19, 2012 - 03:10 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

JB,

One way to determine if Whitworth would be to remove a 1/2" capscrew and check if 12 or 13 tpi.

Barry
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todd_vidgen
Senior Member
Username: todd_vidgen

Post Number: 229
Registered: 03-2008
Posted on Tuesday, June 19, 2012 - 06:02 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Another interesting aspect about whitworth,is their
Spanner sizing IE: a 1/4 inch whitworth spanner is
wider across the flats than a half inch a/f spanner
by nearly a 32nd of an inch .Whitworth use the bolt
shank diameter to identify what spanner to use and
name the spanner size as such.
Todd
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keith
Senior Member
Username: keith

Post Number: 357
Registered: 02-2002


Posted on Wednesday, June 20, 2012 - 11:54 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Before standardization, various US manufactures used 1/2-12.
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richarddurgee
Senior Member
Username: richarddurgee

Post Number: 2859
Registered: 11-2001
Posted on Wednesday, June 20, 2012 - 01:37 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

*

Complete Tool Kit to handle all the various sized
nut and bolt heads for 100 years !













coe


*
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ernie
Senior Member
Username: ernie

Post Number: 1507
Registered: 01-2002


Posted on Wednesday, June 20, 2012 - 02:04 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Hammer too

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