Metric sizes in machine screws and bolts. M7 seems very rare.

[rick]

You sure it is M7 .. and not another thread form This is not far off 17/64 ... could it be an imperial thread, many items made in Japan or US still use imperial sizes.

[Bill Wright]

You'd pull the wall down before you snapped two M6 bolts.

Bill

[Bill Wright]

You'd pull the wall down before you snapped two M6 bolts.

Bill

[David]

Hole isn't threaded.

Just trying to get a bolt/set screw with a snug fit.

Cheers

Dave R

[David]

I did think that larger diameter bolts backed up by washers would spread the load over a larger surface area and be more difficult to pull through the wood panel.

For example an M1 bolt would probably pull straight out, M2 less so etc.

So going for the largest possible diameter of bolt seems sensible where possible.

Cheers

Dave R

[David]

Just to add to other responses, the holes in the bracket are counter sunk.

It isn't about the shear strength but about spreading the load around the area of the nut on the back of the wood panel.

M6 looks O.K., but M7 would be nicer. Just not a lot of it about.

Cheers

Dave R

[Dave Plowman (News)]

Would probably best to use something larger than washers to spread the load. But at the end of the day the strength of the panel is the limiting factor. Same as with a plasterboard wall, it would make more sense to fix to the uprights etc that the panel is fixed to.

[The Other Mike]

While M7 is standardised at three different pitches it's not a preferred size, M3 M4 M5 M6 M8 M10 M12 etc are preferred sizes under ISO 262

The only place I've seen an M7 in widespread use is on the first motion shaft extraction thread on a GM 1980's gearbox where you could remove the end cover from the gearbox, remove a sheet metal cover plate underneath the clutch, press the clutch pedal, clamp the clutch and cover plate to the flywheel with u-clips, withdraw the first motion shaft, and unbolt the flywheel and clutch as one, drop it through the hole in the bellhousing and thus change the clutch without removing the gearbox / driveshafts etc. An easy 30 mins for a complete clutch change vs three or four times that after they changed the design to a solid bellhousing.

[Bob Minchin]

I had one of those. Brilliant idea! no wonder it did not catch on. I even made a 36mm x 1/2 square socket to remove the cover. In order to get an M7 bolt for the job, there was one of several nearby on the engine(bell housing?) that could be borrowed.

[newshound]

Penny washer!

[Dave Plowman (News)]

It certainly sounds a good idea - and I've never heard of it before. But do wonder how much effect having a hole in the bell housing large enough to remove the clutch would have on engine/box rigidity?

[Clive George]

Drill it out to 8mm?

[charles]

or for something American