Schumacher Procat screw list

[QuackingPlums]

I was asked to upload this here, so here it is!

This is a list of screws used as per the manual with my list of modern screws that I used to replace them when I converted them all to hex heads.

Note that the UNC screws are NOT as coarse a thread as the original self tappers, but they work fine in mine. Use a little CA if you want to be extra cautious!

EDIT: Ok, why isn't this working? Am I allowed to upload a PDF?
EDIT 2: Ok, PNG it is...

[Peakey]

Can I ask the screw size for the replacement for example 2/56 unc 3 1/6 button will be a m3 3/16 long is that right or am I missing it?

[QuackingPlums]

Can I ask the screw size for the replacement for example 2/56 unc 3 1/6 button will be a m3 3/16 long is that right or am I missing it?

The old Schueys somehow managed to avoid metrification - M3 screws must have been a luxury because you only got a handful and these were reserved for fixings that required a matching M3 nyloc or a tapped metal hole. All other screws were of the self-tapping variety - even the gearbox bearing holders (which went into the gearbox sideplates) were self-tappers. Must have been cheaper I guess.
The other annoying thing was that they were all slot-driven, so the opportunity to slice up your hands was immense - especially on cold Wednesday race-nights!

When I put this together my aim was to find suitable screws for a Procat runner - using sensible drivers like hex or torx and more common threads that can be readily obtained from non-specialist hardware shops. The aim was not to provide a like-for-like replacement if you're restoring a vintage model.

Essentially I've replaced all the self-tapping screws from the original kit with UNC style screws, which are not self-tappers but will hold quite well providing your plastics/metal plates aren't stripped.

To find a current day replacement, first lookup the Schumacher part number reference from the manual, then look it up in the grid - the first and second columns are the part number and description from the Procat manual. The replacement screw I have used will be in the third column, followed by page number references and quantities used if you want to order a full set.

So in answer to your question, the No.2 3/16" self tap pan head screws (as used in the eccentric bearing housings) can be replaced with 2/56 UNC 3/16" button head screws. When I replaced mine I chose to go hex head all the way as I was fed up of my flat-blade slipping out of the slot screws and slicing up my hands. But it's up to you.

I hope this helps - I put this together AFTER ordering my set of screws so there's a possibility I have missed something. Having said that, this post has been up for almost three years and nobody has complained yet...

[Peakey]

Thanks plums I've taken to the method of removeing the screws getting the caliper out measuring them an ordering what I think is sutible. And so far it's worked out quite well I've been replacing all mine with hex heds from kayfast1 on eBay good quality next day delivery and well priced.

Like you say much esier with hex heads

[terry.sc]

The old Schueys somehow managed to avoid metrification - M3 screws must have been a luxury because you only got a handful and these were reserved for fixings that required a matching M3 nyloc or a tapped metal hole. All other screws were of the self-tapping variety - even the gearbox bearing holders (which went into the gearbox sideplates) were self-tappers. Must have been cheaper I guess.

Schumachers previous cars used metric machine screws throughout.
The reason Schumacher used self tappers in the CATs was because they are the screws designed for the job. machine screws won't hold into the soft plastic of the original CATs as well as self tappers do as self tappers cut their own deep threads as they screw in. A lot of the problems with them are caused by screws being removed them just screwed back in, meaning over time they gradually cut away the plastic due to multiple threads being run into the holes, done properly you should screw the self tapper back into it's original thread so it doesn't cut another one. As for the tiny screws holding the bearing holders onto the gearbox side plates, screwing into thin sheet metal is exactly what self tappers are designed for.

Machine screws are quite often a better choice when screwing into modern glass and carbon reinforced plastics, the much harder material holds the smaller threads much easier with much less chance of pulling out than machine screws into soft plastics.

[QuackingPlums]

Yes, I didn't mean that they should have used machine screws into the plastics, but that when compared to the machined metal posts of my Kyosho Optimas (which were of the same or slightly earlier generation) it felt like a cheaper option to have plastic posts and self-tappers. In fact I remember swapping out the square deck posts for a set of spare Optima metal ones after one too many cross-threading incidents.

I was always happy that a single Meccano screwdriver could be used to completely strip my Cats down, though I won't ever miss that flat blade slipping off those cheese heads and into my soft fleshy hands...