Bicycle Mechanics - TA Crank Pedal Threads

My poor old Sidi shoes from 1988 slit up so I am trying to mount a set of platform pedals on the bike to ride around until I find a replacement. I took off my Time pedals (original version) and the Welgo pedals did not want to thread in. I got the threads in 2-3 turns and the resistance was so high I was afraid I could strip the threads. Is there more than one thread type for pedals? I thought all premium pedals since the 60's used the same 9/16 inch thread. I used to have Campy NR pedals in these cranks with no problems so I don't think it is a specific French thread kind of problem.

My poor old Sidi shoes from 1988 slit up so I am trying to mount a set of platform pedals on the bike to ride around until I find a replacement. I took off my Time pedals (original version) and the Welgo pedals did not want to thread in. I got the threads in 2-3 turns and the resistance was so high I was afraid I could strip the threads. Is there more than one thread type for pedals? I thought all premium pedals since the 60's used the same 9/16 inch thread. I used to have Campy NR pedals in these cranks with no problems so I don't think it is a specific French thread kind of problem.
Although it would be unusual to find a metric thread crank from the late 1980s, both Zeus and TA offered metric (14 x 1.25M) threaded crack arms for a long time -- maybe TA still does. What were your old pedals? Any markings on the pedal spindle? Any markings on the back side of the TA arms? I seem to recall that a "W" mark near the square spindle hole indicated French thread, but I can't find any confirmation of this in my Sutherland's. All my TA cranks have the "W" but I know I retapped some or all of them from metric to English over the years as the supply of metric pedals dwindled.

I checked the crank arm and there is a "W" mark near the spindle hole like you said. The TIME pedals were made in France c.1988 when clipless pedals were new. Your suggestion to look at the pedal for any markings made me take some WD-40 to the offending TIME pedal for some archeological rust and grime removal and I found a "9/16-20" stamped on the pedal spindle. Now I am really stumped. What is going on?

I checked the crank arm and there is a "W" mark near the spindle hole like you said. The TIME pedals were made in France c.1988 when clipless pedals were new. Your suggestion to look at the pedal for any markings made me take some WD-40 to the offending TIME pedal for some archeological rust and grime removal and I found a "9/16-20" stamped on the pedal spindle. Now I am really stumped. What is going on?
Tight threads. Run a pedal tap through the arms to clean them out. Your LBS ought to have a set, otherwise they run about US$36 (http://www.biketoolsetc.com/index.cgi?id=594510960559&d=single&c=Tools&sc=Taps/Dies/Handles&tc=Taps&item_id=PA-TAP6).