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I don't think any of the original screws were 4mm. I have had no problems with the 3mm fine pitch screws, and as long as the hole wasn't stripped to begin with they should be good. -Jeff

I think the old Schumacher screws were self tapper #4s, which translates to something like 2.8mm over the thread. I used UNC 4/40 button heads in my Cat rebuilds, which held ok as they're slightly bigger despite having a finer thread. If you can get hold of 5/40 button heads then that's probably better for stripped holes but I couldn't find any.
I uploaded a list of screws I used to replace all my rusted Schuey ones in the scans section - that might help you.

QuackingPlums wrote:I think the old Schumacher screws were self tapper #4s, which translates to something like 2.8mm over the thread. I used UNC 4/40 button heads in my Cat rebuilds, which held ok as they're slightly bigger despite having a finer thread. If you can get hold of 5/40 button heads then that's probably better for stripped holes but I couldn't find any.
I uploaded a list of screws I used to replace all my rusted Schuey ones in the scans section - that might help you.

Excellent, thanks! I will take a look