Re: Take me through bolt sizes or at least how to work it ou
If your just working on your bike you will probably only find a few fine pitch bolts, all the other will be coarse, so you
simply ask for MX. I can only think of two fine pitch things, bottom bracket[M8x1.0mm] and derailleur hanger[M10x1.0mm].
Thinking about it shimano spindles are 1mm pitch as is the bolt holding the freehub on.
Metric thread standards generally have 4 pitches[I think there is 4 for most large sizes], like M10x1.5mm which is coarse, the fine pitches are 1.25mm, 1.0mm and .75mm.
I have only seen a few <M8 fine pitch threads on cars and bikes, they were on tubes in instruments and things like that.
So If you can assume any M6 is 1mm you have a 1mm thread gauge. so you check a M8 and if it's not 1mm[but is bigger]
it's 1.25 mm and so on, so you can check metric pitches with a few bolts. M8 and M10 fine I haven't ever seen less than 1mm pitch even though it is a standard.
If it's an imperial thread you want to check and you don't have a thread gauge, well lookey here I have picked three random bolts, I can recognise the threads in each case, but her's a simple way of checking them. rub an oily finger over the thread and roll it on a bit of paper and measure it! I have done the three threads and you can guess what thread they are.
OK it's a bit of a mess, you can see where I rolled the threads on the paper and to the left of the series of lines is the overall diameter. to the right, underneath the lines is the number and near that is the length[.0005inches was a bit optimistic] I didn't have my eagle eye lens glasses so wasn't as accurate as usual; it's surprising how close you can get.
At the bottom is what the threads are, no idea why the 6 of 16 looks like an 8;-)
The three random bolts were in fact recognisable, a bolt from a citroen caliper[M7], a rod bolt from a 429 ford engine[1/2 UNF]
and a Norton tappet adjuster[5/16 cycle].
if you want a PDF of the Zeus book pm me.
