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Discussion Starter · #1 ·
Just got the frame back on my 65 Bonneville after powder coating and need to re-cut some of the threads. Can anyone tell me what the thread sizes are for the holes indicated please. thanks.:grin2:
 

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Here's what the parts book say for my 1969;

Oil Tank Mount
21-1822 / S1822
Bolt
UNF 5/16-24TPI X 1/2 U.H

Fender Bracket Mount
14-0113
Bolt
UNF 5/16-24TPI X 9/16 U.H.

Don't know if they are the same but trying to help.

The positions are exactly the same on my frame but 4 years can make a big difference.

Check your parts book and see if the numbers are the same.
 

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1 You do not cut new threads. You need a rethreading tap


2 If the holes that are goobered up are for the oil tank mounting bracket and rear fender bracket all three points use the same bolt (82-0929). That bolt is a 5/16" X26 CEI thread 1/2" long


K
 

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Hi,

1 You do not cut new threads. You need a rethreading tap
+1. The existing threads are still there, just full of baked-on powder-coating.

Equip yourself with either a full set of three taps or definitely #2 and #3 and, if you can afford it, a ratchet tap wrench.

Start by turning the the #2 tap in the hole with either your fingers or the tap wrench without any force; the taper of the tap will pick up the harder existing thread in the softer powder-coating and start to clear out the latter. When the #2's gone as far as it can, use the #3 to finish the job. Test with a bolt. :thumb

2 If the holes that are goobered up
For any other threads, read the fastener part number from the parts book and look it up in http://stainlessbits.com/link12.html for the thread.

Bookmark the site 'cos it's more useful than a tenner you didn't know you had 'til you found it. :)

Hth.

Regards,
 

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Discussion Starter · #6 ·
Thanks all for the help - i took Stuart's advice and recut them with some new shiny taps. Not sure how much use they will get but only a few quid each so not too bad. Had bookmarked the link as suggested and expect to use it often - great tip.
 

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Here's what the parts book say for my 1969;

Oil Tank Mount
21-1822 / S1822
Bolt
UNF 5/16-24TPI X 1/2 U.H
..............
'

Okay 5/16 diameter threads at 24 threads per inch. But what's meant by the term "1/2 U.H."???
 

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He hit the "." instead of the "/" looks like. I just mounted my tank and the bolt was around a 1/2" or so. Didn't measure it since it was the bolt I unscrewed when removing it.

My threads may be different from the OP's but I doubt the changed the depth of the hole.
 

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Hi,

In the past I've seen thread chaser kits available from a few vendors.
No idea what's meant by "thread chaser" but, if all you can do with the bits is clean out existing threads, it'll be false economy. We're dealing with assemblies that four, five or more decades old and, although we revere and care for them now, most have survived periods when spares were difficult or impossible to get and several owners with a wide variation of mechanical skills.

Upshot is that sooner or later, you will have to repair an existing thread or cut a new one. If you bought something that can only clean out existing threads, worst case is it'll break in the hole you're trying to to repair or cut the thread. Then it'll cost you far more than simply buying good-quality HSS taps 'n' dies would've done in the first place. And you'll still have to buy a good-quality HSS taps or die.

First time you have to do anything to a thread, buy the good-quality HSS tap or die. The number of times it'll save your arse in the following years, you'll have long-forgotten the cost of it.

'Cycle Engineering Institute'. It's a standard set of threadforms you'll find widely-used by Triumph for threads into iron and steel before the change to Unified threads from the late 1960's (e.g. the O.P.'s bike was built in '65). Threadform is also known by the abbreviations 'BSC' ('British Standard Cycle') or just 'Cycle'. While most of the the threads on your bike are the aforementioned Unified, it does have a few CEI threads and fasteners - e.g. those into the cylinder block.

Hth.

Regards,
 

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Hi,


No idea what's meant by "thread chaser" ........
Okay one of my spark plug holes, the threads were messed up to where threading the spark plug into it was difficult. One pass with the chaser cleaned everything up. The chaser is like a tap but not aggressive enough to tap new threads. It just straightens up the old ones.

(EDIT) Here's a google on thread chaser sets fyi:

https://www.google.com/search?q=thread+chaser+set&ie=utf-8&oe=utf-8

http://www.summitracing.com/search/part-type/thread-chaser-sets
 

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..........If you bought something that can only clean out existing threads, worst case is it'll break in the hole you're trying to to repair or cut the thread. Then it'll cost you far more than simply buying good-quality HSS taps 'n' dies would've done in the first place. And you'll still have to buy a good-quality HSS taps or die...................
And thread chasing doesn't require much torque. However if it does, then it's time to use the tap and dies. 8)
 

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Discussion Starter · #18 ·
OK, just found some more that need re-threading/cleaning but can't find them in the parts book . They are threaded holes to receive bolts that secure the hangar plates for the rear footrests - see pic. (No21 in the parts book is a CEI 5/16 but also shows a nut and washer but my frame is threaded?) Any thoughts or help gratefully received. thanks
 

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OK, just found some more that need re-threading/cleaning but can't find them in the parts book . They are threaded holes to receive bolts that secure the hangar plates for the rear footrests - see pic. (No21 in the parts book is a CEI 5/16 but also shows a nut and washer but my frame is threaded?) Any thoughts or help gratefully received. thanks
Those holes should be through holes, not threaded. A bolt/washer/nut secures them to the frame bracket.
What year is your bike?
 
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