Grillo wheel stud thread pitch and PCD

[texanjim]

Hello, I've got a technical question that I'm hoping someone might be able to help me with.

I'm going to make up some wheel weight hangers to fit over the studs on my Grillo G85D (I'm in the UK so can't buy from Earthtools).

My basic idea is to get a disc cut from 4mm steel, with the 4 stud holes and a 25mm hole in the center. I will then weld a 25mm diameter bar into the center hole, welding from behind and around the diameter. The disc will then slot over the studs without removing the current nuts, then attach with 4 additional nuts.

I can't just remove the 4 existing stud nuts and secure with them, as the large hub nut in the center protrudes and would mean a more complicated build, (I'm learning as I go, so trying to keep things simple). The existing stud nuts are pretty much flush with the hub in the center, and the studs appear long enough to fit the 4mm disc and have room to tighten a new nut over the top.

So my first question is does anyone know the thread pitch of the wheel studs? I have an M12 nut here that appears to be a course thread, and this does not fit. Looking up the fine thread specs of metric nuts, there is a 1.50 pitch and 1.25 pitch. Before I order, does anyone know which it would be? If it helps, the nut is the same size and thread as the 2 that secure the tiller to the PTO flange.

Secondly, does anyone know the PCD of the bolt pattern on the Grillo? I can get a disc cut here:
CUSTOM CUT MILD STEEL FLANGE - VARIOUS THICKNESS'S & DIAMETER - MULTI LISTING | eBay
I can of course just measure as accurately as I can to get the PCD, but just wondered if anyone knew or had worked this out themselves.

Any help gratefully received!

 

[oldmech]

Hi! Nuts are 12mm 1.25. I make two sets. I use mild steel flat bar(cheap). 4 mm thick is enough . For bolt pattern . I hit a little bit with one hammer a heavy paper on the four bolts. I put the paper on steel bar I punch and drill the holesl Good luck! Oldmech

 

[texanjim]

Thanks Oldmech! I had ordered a thread pitch gauge as they aren't expensive, but you got there first so have ordered a pack of nuts 1.25 nuts.

I had thought about using flat bar, but wasn't sure if it would be strong enough. Did you use just one piece bolted to 2 studs, or did you weld a cross? Also, did you surface weld the rod that holds the weights, or drill a hole and weld from the back too?

I really appreciate your help.

 

[oldmech]

Hi! I use a flat steel plate about 5 .in or 125mm square . Easy to find center you trace two lines from four corners and you have a cross. Good help for bolt holes also. I drill a small hole in center as 5mm and an other in the shaft 25mm x 225mm. So I can weld the shaft in perfect center . I just weld around. We have over 5mm space by nuts for the weld. You can drill a 25mm hole and weld under. Shaft must be well center and well aligned.
Good luck! Oldmech

 

[texanjim]

Thanks Oldmech. That sounds like a simpler, and cheaper option. If it's working for you then I'm sure it'll work great for my needs.

I've ordered all the bits, so will have a go at putting it all together when they arrive.

Many thanks

 

[texanjim]

Just taken delivery of a thread pitch gauge, and can confirm that you're right on the money, the pitch is 1.25. Thanks again Oldmech