| Author |
Message |
    
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 697
Registered: 07-2002
| | Posted on Monday, June 18, 2012 - 05:04 pm: | 
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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? |
todd_vidgen
Senior Member
Username: todd_vidgen
Post Number: 228
Registered: 03-2008
| | Posted on Monday, June 18, 2012 - 05:42 pm: |
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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 |
bcm
Advanced Member
Username: bcm
Post Number: 31
Registered: 11-2009
| | Posted on Monday, June 18, 2012 - 05:58 pm: |
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JB,
I've replaced head studs on many St Lawrence engines, all 7/16x14tpi.
Barry |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 698
Registered: 07-2002
| | Posted on Monday, June 18, 2012 - 06:04 pm: |
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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. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 699
Registered: 07-2002
| | Posted on Monday, June 18, 2012 - 06:11 pm: |
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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. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 700
Registered: 07-2002
| | Posted on Monday, June 18, 2012 - 06:29 pm: |
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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) |
bcm
Advanced Member
Username: bcm
Post Number: 32
Registered: 11-2009
| | Posted on Monday, June 18, 2012 - 06:35 pm: |
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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 |
bcm
Advanced Member
Username: bcm
Post Number: 33
Registered: 11-2009
| | Posted on Monday, June 18, 2012 - 07:31 pm: |
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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 |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 701
Registered: 07-2002
| | Posted on Monday, June 18, 2012 - 08:13 pm: |
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This is one of the very early engines, drip oiler, rear timer. |
bcm
Advanced Member
Username: bcm
Post Number: 34
Registered: 11-2009
| | Posted on Monday, June 18, 2012 - 08:50 pm: |
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JB,
Probably Whitworth.
Barry
http://www.britishfasteners.com/index.php?crn=262&gclid=CO6ftNaJ2bACFUgDQAod0CFh 3A |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 702
Registered: 07-2002
| | Posted on Tuesday, June 19, 2012 - 12:46 pm: |
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It would be interesting to see if they used Whitworth, if they switched, and when. |
bcm
Advanced Member
Username: bcm
Post Number: 35
Registered: 11-2009
| | Posted on Tuesday, June 19, 2012 - 03:03 pm: |
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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 |
bcm
Advanced Member
Username: bcm
Post Number: 36
Registered: 11-2009
| | Posted on Tuesday, June 19, 2012 - 03:10 pm: |
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JB,
One way to determine if Whitworth would be to remove a 1/2" capscrew and check if 12 or 13 tpi.
Barry |
todd_vidgen
Senior Member
Username: todd_vidgen
Post Number: 229
Registered: 03-2008
| | Posted on Tuesday, June 19, 2012 - 06:02 pm: |
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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 |
keith
Senior Member
Username: keith
Post Number: 357
Registered: 02-2002
| | Posted on Wednesday, June 20, 2012 - 11:54 am: |
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Before standardization, various US manufactures used 1/2-12. |
richarddurgee
Senior Member
Username: richarddurgee
Post Number: 2859
Registered: 11-2001
| | Posted on Wednesday, June 20, 2012 - 01:37 pm: |
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*
Complete Tool Kit to handle all the various sized
nut and bolt heads for 100 years !
* |
ernie
Senior Member
Username: ernie
Post Number: 1507
Registered: 01-2002
| | Posted on Wednesday, June 20, 2012 - 02:04 pm: |
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Hammer too |
