This puzzles me about forged pistons

[Mignon]

Ahbefive said:

Indeed, your ignorance on the topic is shining brightly.

I think you've probably irritated enough people in here for one visit. Isn't there a muddy hole in the ground you need to get back to while the grown ups discuss engines?

[stevieturbo]

Inline__engine said:

M12 coarse vs M12 fine. or they could just be chinese

Maybe it's M12-0.2

Do Chinese use tape measures horizontally or vertically ?

[littleredrooster]

stevesingo said:

An 86mm bore is a hole in a block which is 86mm in diameter +-the manufacturing tolerance.

An 86mm piston is an 86mm piston in name only. It is designed to fit in an 86mm bore, less the designed running clearance. It does not measure 86mm in diameter.

HTH

Edited by stevesingo on Wednesday 12th September 08:29

Yes - just I already said on Tuesday...

[littleredrooster]

Ahbefive said:

...an M12 bolt does not fit in an M12 hole. It's a very different type of engineering but engineering all day is what we do.

Sorry but an M12 bolt actually does fit in an M12 hole. Unless you mean spanner sizes, the way amateur engineers may describe things.

Ahbefive said:

Now I am asking for your expert knowledge on what exactly I have said that is wrong and why.........

Over to you...

[PhillipM]

What the hell is an M12 hole?

A 12mm hole maybe.
If that's the case an M12 bolt will drop straight in it because they're always a tenth or two undersize.

[PaulKemp]

My M10 x 1.5 thread pitch tap has an 8.5mm pilot drill

[garagewidow]

PhillipM said:

What the hell is an M12 hole?

A 12mm hole maybe.
If that's the case an M12 bolt will drop straight in it because they're always a tenth or two undersize.

Ah,..the thread might but the shoulder could be o/s slightly,enough to bind in the hole.

Now,a 12mm setscrew will indeed fit/screw into a 12mm hole right up to the head.

[PhillipM]

Nah, shoulders are always undersized too, even on precision ground shoulder bolts they're generally a hundreth of a mm or so undersize.