TAP SIZE

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norvillnh

norvillnh

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Tap size: Banjo bolt threaded hole on the head of a 75 Commando. Threads needs a bit of cleaning up. I need to get the correct tap for the diameter and thread.
Also need to know who sells this. Thanks
 
I don't remember the size but you can get individual taps and dies here as well as most other tools, fasteners, thread repair, and other things you might need: https://britishfasteners.com/ I'm not affiliated with them, just a customer.
 
Something like this might be worth a shot using a suitable bolt.
It would depend on the state of the thread and where the deformation is.


You can fix near anything with a little careful metal forming.
72+ year old screws.

TAP SIZE TAP SIZE
 
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For Metric fasteners, this type of chaser works well, without cutting bigger. Is there something suitable for the Whitworth threads?
Failing that, a bolt with a notch filed in it has worked for me when afield and cleanup is needed.
E5EBF4BD-978B-4E0B-B344-E7163642A9CF.jpeg
 
The very beginning of the threads, is preventing the banjo bolt from starting to screw in.The threads are undamaged beyond the beginning, Somehow, the start of the thread got slightly damaged when the head was off, don't know how. The banjo bolt is not damaged, it easily screws in on the left side. I ordered the tap. 73+ year old doing the re-assembly, could be the problem. :mad:
 
I am going to have it looked at by someone with much more experience on fixing this problem.
Thanks all
 
norvillnh said:
The very beginning of the threads, is preventing the banjo bolt from starting to screw in.The threads are undamaged beyond the beginning, Somehow, the start of the thread got slightly damaged when the head was off, don't know how. The banjo bolt is not damaged, it easily screws in on the left side. I ordered the tap. 73+ year old doing the re-assembly, could be the problem. :mad:
Click to expand...
In this situation a tap will work best, but only run the tap into the damaged threads and no further, then chase the threads with a good bolt or thread chase.
 
Like Time Warp said taps can very often make matters worse, especially when they are brand new . Their sharpness makes it difficult to start them and they often get cocked or start cutting a new thread out of whack with the original. I would only use a taper, fed in slowly by hand without a wrench and see if it will pick up on the original.

In the past I have successfully used a thread gauge held in Mole grips to "scrape" the threads back to shape. Doable on a bench, but not so easy on the bike I guess.
 
concours said:
For Metric fasteners, this type of chaser works well, without cutting bigger. Is there something suitable for the Whitworth threads?
Failing that, a bolt with a notch filed in it has worked for me when afield and cleanup is needed.
View attachment 83860
Click to expand...
I have BSF & BSW thread chasers, I've have had these for many years as needed for my old trade. But like most things you don't see them for sale anymore
I concur with Concours use a new bolt/setscrew with a grove cut with hacksaw at 90 degrees to the threads and if the hole is blind smeared some grease on the threads to collect the debris
 
But if the banjo bolt won’t start neither will a slotted bolt surely?
 
Time Warp said:
It would need a starting taper as per the video in Post # 5.
Click to expand...
I took a look at that earlier, but the link you posted just goes to a bunch of “slotting threads” videos. Was there a particularly helpful one?
 
cliffa said:
I took a look at that earlier, but the link you posted just goes to a bunch of “slotting threads” videos. Was there a particularly helpful one?
Click to expand...

That's odd, when I click on it it goes to a whole page of how to make a thread chaser video's from a bolt under 'Make a thread chaser YouTube search.

TAP SIZE
 
Sorry, yes they are but I didn’t see any about tapering the bolt. Maybe I missed it.
 
So, Concours came over and fixed the thread, but he noticed something I did not. The threaded hole for the banjo had been hit with something hard that put a dimple on each side of the opening, pushing the starting threads in. That's why I could not start the bolt. He strightned out the threads, then filled in the dimples with JB Weld, smoothed it out flush with the rest of the surface and tomorrow I will put the oil lines back on. I don't know who, how or what hit the surface. When I get it all set and running, I will update on the repair.
 
norvillnh said:
So, Concours came over and fixed the thread, but he noticed something I did not. The threaded hole for the banjo had been hit with something hard that put a dimple on each side of the opening, pushing the starting threads in. That's why I could not start the bolt. He strightned out the threads, then filled in the dimples with JB Weld, smoothed it out flush with the rest of the surface and tomorrow I will put the oil lines back on. I don't know who, how or what hit the surface. When I get it all set and running, I will update on the repair.
Click to expand...
Nice one Concours !!
 
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