This listing is for a set of 4 Raised (i.e. Domed) countersink petrol tank location screws, to fit Douglas 2 3/4hp models. The underside of the head has the correct taper to match the frame lugs and the thread profile is the unusual and non-standard 7/32" x 24 tpi thread particular to this Douglas model.
These screws are CNC machined in Stainless Steel and the heads are lightly polished - looking very similar in appearance to the original Nickel Plate finish of this period - and if I say so myself, quite pretty.
Like many of the fasteners on early Douglas motorcycles, unusual threads were used - possibly so customers had to go back to Douglas themselves when they needed replacement!
The screws used on early flat tank Douglas 2 3/4hp models are an example of this - they being 7/32x24tpi. They also have a 90 degree countersink which these screws have. As part of rebuilding my own 1919/20 Douglas 2 3/4hp bike, I have manufactured a batch of these screws for other owners. In making and checking these screws - I fitted them against the original petrol tank I have for my 1919/20 bike (still with original paintwork), as well as another restored tank of approximately the same year. I also checked them against a 3rd, much earlier 1912 tank I have in my possesion - which is of the earlier/slimmer construction used on Douglas 2 3/4hp models from approx 1911-1919. The screw threads of our screws fitted all 3 petrol tanks. Both early and later Douglas 2 3/4hp petrol tank types are shown in the accompanyning photogs. Sorry, I am not sure which year this screw type were first fitted, or which year it was replaced - but I would expect it will probably fit all Douglas model petrol tanks from @1911-@mid 1920's, possibly later. If not sure, feel free to email us on email@example.com
I have manufactured these screws with a thread length of 0.440". Frankly, I expected to have to make them with a longer length - but in checking all 3 original petrol tanks I have (i.e. a 1912 tank, a @1919 tank and a @1920-21 tank) - I found that making the screws any longer would mean them 'bottoming out' in at least one of each tank holes.
The head shape is lightly domed and is 0.420" diameter, which is wider than modern commercial screws but fits nicely against the original Douglas frame countersink. I have looked at various pictures of original and restored Douglas models of this era and cannot find a picture that clearly shows an original screw, but have made the heads of these screws to a profile that looks appropriate and correct for a bike of that era.
Final point if wanting to fit these screws - if your original threads are damaged or full of dirt (as some of the threads on my tank were), Tracy Tools (https://www.tracytools.com/) can offer a 7/32x24tpi tap in both taper and plug size, which is extremely useful for recovering the thread before fitting these screws.