I have looked at the dimensions for the SR30 rails and the diameter of the holes in the rail are 7mm. I have not seen 7M bolts around. I was hoping to be able to use Tnuts and extrusions to mount my rails but I have not seen any Tnuts that use 7M bolts.

Anyone have a solution to this?

7 mm pass through hole, or threaded?
if it is a hole in the rail with no threads, just use M6 bolts or 1/4 inch bolts with t-nuts.
You can always enlarge the holes if need be too.
If it is threaded to a wierd pitch, drill out to the next size up and re-tap (providing the metal is not hard)

Good luck

Yeah,
Forget metric, I used 5/16-24 in SR25 rails with room left over.

Just check the fit with a spare inch bolt of known dimensions.

Ken

I'm playing with some thk SR15 rail on 1020 extrusions, I ended up buying m3 shcs and a few feet of blank t-nut stock from 80/20, cut to how you want to use it then drill and tap to match the holes (some say that using the solid t-nut stock full length of the rail will help keep the rail closer to true flat)

OR... you can do like some of the others said and just use inch based bolt, in that case convert the hole size in the rail to inch and use a screw chart (http://www.engineersedge.com/screw_threads_chart.htm) or tap chart on www.engineersedge.com to figure out what you need to use to screw the thing down

keep in mind I'm guessing that your rail sections have counter sunk fastener holes in them, if the rail is tapped for bottom mounting... that changes everything, for that I'm not sure how you are going to attach it