KTM Tank Car Truck screw sizes

They used funky shouldered screw with a spring; might have some about, odd size - metric, maybe. I just re-tap to whatever in both cases and not worry about it.

Precision scale used to have screws that I think matched those holes for the trucks.     I think they came with the springs too.     The coupler mounting screw is just a common very small metric screw, if metric is common!   It might be a 1 MM  x some length, say 4-5 MM.    

I found and downloaded a copy of the PSG&Frt car catalogue as of 2018.     Attached is the page with the screws for truck mounting.   It appears they have/had 2 styles and the they 3 MM.

Thank you for your responses. This is interesting. So based off the PSC catalog, which part number would work best for these cars? I don't have a tool to measure the size here.

Well I think this means it is probably a 3 MM screw.    so any 3 MM screw would work, it just may not be shouldered.    You could try you local hardware or hobby shop and see if you can find a 3 MM screw by say 8-10 mm long.    See if the threads match.   

The other question is what type of trucks do you plan to use and how big is the hole in the truck bolster?    It may make sense to change the hole size and tap it.   2-56 screws are very common in US made O scale and even to some extent HO.

Given that most brass trains and many diecast trains use metric fasteners why not buy a few assortments from Amazon or eBay. Among others I have are 1000 screw, nut, washers 1mm to 1.8mm for about 7 bucks shipped. Larger sizes readily available for small money. Just search on metric screw assortments.

Pete

A common issue with older KTM USH, Max Gray metric machine screws is that they weren’t made to later ISO metric thread standards.  I recall a US Hobbies news letter announcing a shift to  ISO threads on future models.  The shouldered truck mounting screws in the PSC catalog are in compliance with ISO standards and will cross thread when you attempt to put them in older brass car bolsters.  When I run into this issue I usually  retap the bolster to the next larger English screw Size.  A piece of tubing that tightly fits over the new screw and cut to length provides the “shoulder”.  With the wide variety of screws used on O gauge models over the years having an assortment of metric and English machine screws in small parts bins comes in handy.  I buy long slightly long sizes and  cut them to the needed length.

Bingo, you may see a pitch variance in metric (threads per cm, or threads per mm of length.)  Sometimes the pitch is off the wall, proprietary, or country based.

Keystoned Ed posted:

........retap the bolster to the next larger English screw Size. 

Yes.  Just set a standard in your shop and for your roster and stay with it. There's very rarely a real need to do otherwise.