doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Whitworth threads

Pooch, do you know who made your A&N? Good chance it was Webley & Scott. And if it was, you may well be in luck. You might be able to find a gunsmith with a W&S bolt that will fit.

I'm with Rocketman. Find the closest available size, run a tap through and be done with it.

If it is an old Webley they used several thread forms if it is not a BA then the closest you may get is to look at it as a metric thread but with a Whitworth form of 55* not 60*.Basically the metric standard thread will probably do the job as it may well measure up as MM size .

I'm pretty sure it is a webley & Scott as the gun really has the appearance of a William Evans which is a W&S made gun.

For whatever it's worth the standard form of a US thread is not a sharp V. The normal form of a 60� US thread has the crest of the external thread flattened by 1/8H (H= height of the theoretical sharp V) & that of the internal thread flattened by �H. The normal "Tap" drill size or the normal pitch diameter for the external thread will ensure that neither ends up as sharp V.
Though somewhat dated now I have a set of thread spec book which I had to acquire when going through my machinist apprenticeship back in the 1960's.
If anyone has a specific thread they would like more info on let me know & I will look & see if it is covered. They do cover several British threads (including Whitworth) as well as metric & many unusual US threads even including light bulb threads.
Although not "Exact" a working solution for a tap drill for a 60� thread is to subtract one pitch length from the nominal diameter & then use the closet drill size possible. This will apply to either metric or US pitches, but remember that with US threads being given a TPI the pitch length is 1/TPI. Thus for instance a �-20 thread would have a pitch length of 1/20 or 050". A workable tap drill would thus be 200".

FWIW Whitworth bolt heads are the same size as metrics. It would not surprise me if the diameters were metric as well. I have nothing anymore to check for thread pitch but I'm guessing that would be TPI. And metric threads are the 55deg thing too. At least on bikes and motorcycles. Sorta like one from column A, one from ..................

have another day
Dr.WtS

I needed a tap when working on an Enfield sporter. These folks have a great assortment of tools and fasteners => www.britishfasteners.com

Thanks Wonk it's great to hear from you again. I know you are likely in pain because of Hillary's loss, but at least you haven't gotten on TV like these lame brain has beens and never wases to tell the Electors how to vote and blame Hillary's loss on the Russians and not the voters.

By the way I have converted from Browning to Italian style O/Us. I hate to admit it but you influenced me.

WTS: True metric threads are 60 degree just like US threads. There have been a number of different British thread standards used over the years, including Whitworth. There was a standard for cycle threads and one that is frequently used on models, British Association (BA) which is actually a metric thread.
Miller is correct that the US threads are technically flat on the top and bottom, but in my experience most are lathe cut with sharp Vees to eliminate the need to grind a special tool for each TPI to be cut..

Tom;
True, I have lathe cut threads with a sharp V tool. Note this will leave the sharp V Only in the root of the thread. When you get to the proper pitch diameter the crests will still have the flat. When you drill or bore the hole to the proper size for the internal thread those crests also will still have the flat. I have also lathe cut threads where it was a "Requirement" to put the proper flat on the tool for the part to met specs, just depends on it's designer & the use for which it is intended.
All the standard metric threads I am familiar with do have 60� V's. The Whitworths I am familiar with all had English pitches & 55� angles.
Mauser rifle barrels were fitted with a Whitworth thread having standard English pitch. Many have been rebarreled by US Gunsmiths with lathe cut threads having a standard 60� thread. They simply chased the thread until it would thread into the receiver & apparently no problems resulted from this practise.