[StuBeeDoo]

I've got a couple of cars with stripped threads in body posts.  I assume the simple answer is to use over-size screws, but can anyone suggest what size to use, please?  I never know how to measure screws.  

The cars in question (at the moment.....) are a Team Slot Celica and an SCX Cordoba.

Thanks in advance,
Stuart.

[Savage GT]

If you have some Vernier's , measure the screws width across the threads.
If it is 2.2mm for example, you could try a 2.4mm screw (if the post has enough diameter to allow this without weakening it).

Another alternative is to fill the post with epoxy (my personal favourite being JB Weld Cold Weld), stick a thin rod/piece of fuse wire/cocktail stick down the hole to smear it around and remove to leave a slightly smaller hole.
Once dry you can re cut the thread with the original screw, or if required carefully open up with a pin vise drill to a little smaller than the screw.

[Nonfractal]

I find a smear of thin superglue worked into the body post with a pin works well
Allow it to dry thoroughly then gently reinsert the screw a turn at a time, backing off half a turn each time.
Collared screws are a good upgrade, NSR or slot.it brass are my go-to screws.

The nsr screws have threads cut into the shaft diameter, the slot it screws have threads larger than the shaft diameter.
Try nsr first then slot.it. 
AlanW

[rallyhub]

A simple and effective solution is :
Remove a piece of insulation from a 230 Volt electricity wire and push it into the drilled hole of the body post.

Hub

[Kevan]

Oversized screws will split the body post.

I use Alan's method, superglue smeared round the inside of the hole, a dash of activator and Bob's your uncle.

[StuBeeDoo]

Thanks for all the replies, chaps.  

[Scuderia_Turini]

A couple of times I have been able to use a set-screw type of the same size rather than the original self-tapping type. The finer set-screw thread  will find a different path in the body post.

Leo

[Kevan]

I prefer M2 Torx screws

[KensRedZed]

British Standard Whitworth bolts for stripped threads! 

Hard to find though.

[mickey thumbs]

If the post is toast (cracked or stripped beyond hope, Slot Car Corner in the US sells these repair kits. You can easily make your own. Brass tubing to slip over post, flanged, threaded receiving thingie and screws.