Old Webley screwsSeptember 9 2017 at 4:25 AM
|Peter (Login aussiepj)|
Response to UK Webley Thread Pitch ??
I am sorry that I may have mislead those who read this post; maybe 12000 miles from home or old age did not help! But ALL FASTENERS FOR THE PATRIOT ARE 3/16" IN DIAMETER AND NOT 1/4" AS I ORIGINALLY WROTE. FORE END AND FRONT TRIGGER GUARD SCREWS ARE WHITWORTH FORM WHILST THE REAR GUARD SCREW IS BRITISH BSF FORM. I have a couple of British Patriots and the two screws on the fore end are 3/16" Whitworth (the difference between UK Whit. and SAE coarse is usually only thread angle and threads per inch very often the same but not always. I used mushroom head hex drive to replace mine. Torque is 24 inch pounds. The front trigger guard is also 3/16" Whit. as well; here I replaced mine with a countersunk hex drive screw, torque is again 24 inch pounds. The rear trigger guard screw (long) is 3/16" BSF thread 32 TPI (I think the tread pitch is correct but cannot check as I am not in Australia ATM). However this longer screw screws into the alloy compression cylinder end cap and is better replaced as follows. Five mm metric fine thread is that close in thread pitch and diameter to 3/16" BSF; difference is approx. 32TPI (BSF) to 31.75 TPI (metric) and OD of the metric is only a few thou. larger in diameter. What I do is to run a 5mm metric fine tap into the end block (very easy to do and you will not damage anything) but much deeper than the existing thread. Doing this you can use a 5mm metric fine countersunk hex drive 45mm long, much longer than the original (BSF possibly very difficult to get) that will provide a superior fix than the original. Again 24 inch pound torque; all screw are High Tensile. You can use high strength thread locking adhesive on the two fore end screws but ONLY a dab of medium strength on the guard screws. Do not use high strength adhesive on the guard screws! If you want, using a 1/4" Whit. finishing tap you can get a few extra threads on the compression tube for the front screws. Doing this you might have to get 1 1/4" long screws and cut them a little shorter. I think the original screws were 1 inch long. Doing this you replace all the Phillips screwdriver head screws which are not high tensile and near impossible to torque to the correct torque . Hope this helps.
aussiepj in Europe ATM
As Rob Best posted American UNC thread form should work in a pinch as a substitute for British Whitworth being that the only difference is likely to be a small difference in thread angle but as I wrote above, 5mm fine (0.8mm thread pitch) very close to British BSF.
|This message has been edited by aussiepj on Sep 12, 2017 3:59 AM|