Having started work on the next project (MX5 - say it quietly or else someone will say h*irdresser) I've been surprised by the number of nuts and bolts which have stripped.
OK some are quite rusty but it's a suspicion I've had before on bikes - are Jap metric sizes slightly smaller than European?
Either that or maybe my sockets are wearing out!
Anyone-else found this?
Cheers, Pewe

The head size is smaller!!

When i took apart my nissan engine i found all the bolt heads are smaller, so what would normally be a 13mm across the flats would be 12mm and so on

isn't that weight saving?

These days all manufacturers use flange bolts the hexes of which which are generally either 2 or 3 mm smaller AF than preferred standard hex bolts as a result you need all the metric socket and spanner sizes in 1mm increments between 6 and 24mm.

When dealing with flange bolts if you encounter one you even suspect of being slightly tight or rounded it pays to switch to using an "Irvine Bolt Grip" socket at an early stage.

A set of Irvine Bolt Grip sockets and with the extra expansion pack should be on everyone xmas list.


[Edited on 28/11/11 by britishtrident]

quote:

---

Originally posted by britishtrident
These days all manufacturers use flange bolts the hexes of which which are generally either 2 or 3 mm smaller AF than preferred standard hex bolts as a result you need all the metric socket and spanner sizes in 1mm increments between 6 and 24mm.

When dealing with flange bolts if you encounter one you even suspect of being slightly tight or rounded it pays to switch to using an "Irvine Bolt Grip" socket at an early stage.

A set of Irvine Bolt Grip sockets and with the extra expansion pack should be on everyone xmas list.


[Edited on 28/11/11 by britishtrident]

---

Metric threads are metric threads. Assuming you're talking about stripping threads as mentioned in the OP, not rounding heads, you might be coming across the difference between metric coarse and metric fine, of which there's a few depending on bolt size. The Japs have a love of metric fine threads due to the higher clamping forces available with smaller bolts (finer pitch means more shear area on any length of bolt, generally). Get yourself a thread ID kit.

I think the OP may have been talking about rounded heads, rather than stripped threads...

The only thing I've noticed over the years is that when you look at something and think it's roughly 10mm or 8mm etc, because that would be a common size to us, it's sometimes a 7mm etc etc...

Surely no-one's daft enough to blindly use a tool of the wrong size because the head should be a different size for that diameter? You put it on and give it a wiggle to check, it would take a pretty ham-fisted approach to just use your "normal" size and round everything. And even if you rounded one, you'd check against the next, surely? Whereas it's really easy to get thread pitches confused and it seem like just a slightly stiff fastener, then trash it, if you don't realise there's multiple thread pitches of the same size fastener?

Oh, well, I don't know, that's how I read it. On re-reading it you might be right.

[Edited on 28/11/11 by coyoteboy]

Don't be surprised if you find A/F fixings amongst the metric ones...

When I stripped down my Mikuni bike carbs I found several items that had imperial dimensions, e.g. 5/16" - not "about 5/16" - exactly that dimension, to within a thou. There were many other pieces like that. All the fasteners were metric threads, but some of the slotted heads were imperial diameters.

Very odd...

aint you got that running yet?

quote:

---

Originally posted by David Jenkins
Don't be surprised if you find A/F fixings amongst the metric ones...

When I stripped down my Mikuni bike carbs I found several items that had imperial dimensions, e.g. 5/16" - not "about 5/16" - exactly that dimension, to within a thou. There were many other pieces like that. All the fasteners were metric threads, but some of the slotted heads were imperial diameters.

Very odd...

---

I believe it's because the Americans helped to rebuild the Japanese industries after the war - they inherited a lot of US measuring systems in the process.

Don't forget 8mm is only 3/10ths of an inch away from 5/16"!

a lot of jap bolt heads are dished in the centre (apparently to save weight) i think they collapse under load once they have rusted a bit, i always use hex socketts which helps
keith

Actually meant rounded off the nuts but some bolts did strip as well.
I think the comment about the Yanks helping to re-build Jap industry explains a lot.
Also interesting to note that the Irwin stuff being American uses 3/8" drive rather than 1/2 or 1/4.
Just in case any one-else is looking at these sets the sockets which I've found available and their equivalents are as follows (rounded up to the nearest decimal point):-
5mm,
5/16 = 7.9mm
3/8 = 9.5mm
10mm
7/16 = 11.1
1/2 = 12.7mm
13mm
9/16 = 14.3
5/8 = 15.9
16mm
11/16 = 17.5mm
3/4 = 19.1mm
That's the basic Irwin set plus the Expansion set.

Screwfix show an 11mm but unless they are having them specially made I reckon that will be the 7/16 one.

Looks like Santa's coming early!
Thanks guys, Pewe