From my measurements: OD mic'd 1.433"
That would likely be 1-7/16" diameter, however it is also 36.5 mm. The thread pitch gauges at 18 TPI (.0555") and 1.4 mm (.0551")
So, 1-7/16 - 18 (inch)
Or, M36.5 x 1.4 (metric)
By measurements these appear to be interchangeable. I am sure 1-7/16 - 18 is available. Not sure about M36.5 x 1.4 mm.
I know 1-7/16 - 18 will definitely work, quite frankly either will work. I would bet on 1-7/16 - 18 (inch).
Hope this helps, DT's website doesn't. They don't elaborate on how their/ EI's suppressor attaches, or whether the threads on the brake are even used. EI doesn't show this either, but does list two available threads (not these) Do you know of anyone having a suppressor that attaches to this brake?
My Alpha 50 is supposed to be M25x1.5. It is smaller than my DT408 which is M22x1.5. Makes me wonder if Elite Iron sent a direct barrel thread in a different thread instead of the over the brake threads?
Your measurement shows 1.175" on the minor diameter (=29.845mm) if we assume it it 1.5mm pitch (29.845+1.5=31.345mm) it woul appear to be M31 x 1.5
On the .896 minor diameter (=22.758mm) assume 1.5 pitch (22.758÷1.5=24.258mm) this one looks like M24 x 1.5
EI's website shows the Alpha to be direct thread attachment and either 1"-14 or 7/8"-14. They must do something special for DT.
Both websites lack a lot of information!
I have sent a info request to DT about their 50 suppressor and mounting, as well as the threads on the OD of the brake, what they are intended for.
I too want a suppressor that attaches to the brake.