It is an UNC screw, I have bought a set (20 pieces, 12 US $ in total) of 10-24, 3/4" long in stainless steel ones from AliExpress, works fine.

Are you sure? I was sure they’re M5
they look verrrrry close to the imperial surf ones.
But they are a tiny bit fatter

I can look at one tmr at work

Be handy to check mark thx..

i tried some m5 screws and they're a touch too big or thread is not right so i stopped. Fcs was about right but not tight which could be from use. Was thinking m4 but like kris says the thread matches the fcs screws so i agree with him they're 10-24. i’ve ordered both m4 and 10-24 unc 24tpi. Have to fill and tap one screw hole to repair previous owners damage. My gut is the simmer slot box screws with the heads are m4, the grub screws are 10-24.

thing to also note is the allen key size for the grub screw head is not metric… using a metric key chews out the heads. So an fcs tool which is imperial is needed to adjust grub screws.. fcs tool was the perfect fit for the heads.

Rango said..
In my v3 flywave they are m4 x17mm.Seems they get corrosion so I,ll treat with Tefgel.

Thx Rango .
To confirm v3 uses grub screws too.

From left to right
New 10-24unc
Existing slot box screw
New m4

10-24 unc 24tpi is the repacement grub screw

Nope. 4.9mm would be the closest but if you go metric the thread is wrong..

So you need 10-24 which is the fcs grub screw diameter. FCS is only 10mm long though. Simmer needs 3/4in length.

If your boxes are worn you could go to m5 and work the new thread through as anything metric is the incorrect thread.

Hey, I’ll check my spare box tomorrow, I did have some spares just incase. If not I get my new gear around September so can have them added in to my order for you. If you are in desperate need I’d shoot Simmer an email and see if they can do something for you. They have helped me out with spares in the past without going through the web shop,

Appreciate the offer jason.
Won’t need as i’ve got a bunch here i just bought at a local nut and bolt shop..

as an aside, i put the existing ones through a rust wash and retapped all the holes. All bar one are working like new now..although i plan on spraying with silicon spray.

1 of the 10 holes took a little more work and needed to be overdrilled so i’ll epoxy that and retap it. Board will be literally as good as new after that.