Help identifying bolt size

[jreacock]

Hi. I usually have a load of bits left over after taking things apart, but this time, I've got less than I started with.
Does anyone know the bolt size (diameter, thread and length) that I've identified by the yellow circle?
The two plates that the bolt goes through seem to be under a bit of tension, and make it quite hard to see the thread. I'm hoping that they will sort their positioning out when I fit the bolt, but it won't be difficult to cross thread it as it is - especially if I try the wrong one.

Thanks.

[jreacock]

Thanks to Mark at BetaBoyz - it's an M10 fine - just in case anyone else ever has this query.

[mangocrazy]

Just a thought - I'd heartily recommend the purchase of a metric screw pitch gauge so that you know exactly what thread pitch you are dealing with. I know for a fact that there are at least three different M10 thread pitches (may well be more) and metric fine in M10 can refer to M10 x 1.00 and M10 x 1.25. Buy one of these and there is no more guesswork:

http://www.ebay.co.uk/itm/Sealey-20pc-Metric-Screw-Pitch-Thread-Gauge-0-4-6mm-Folding-Leaves-/221612033486

With that and a cheap set of digital vernier calipers you can be absolutely precise over the size of screw or bolt you need to order.

[Dermist]

I thoroughly endorse the above comments regarding a screw pitch gauge. 

I use a Chinese one which for weekend warrior use is perfect.  Also, it was only 99p! 

http://www.ebay.co.uk/itm/2017-NEW-Screw-pitch-gage-60-degree-Stainless-Steel-Metric-Thread-gauge-1pc-/302185530733?hash=item465ba9456d:g:NioAAOxyaTxTQ8br

If I used it day in day out then it might not stand the test of time.

It is amazing how many fine pitch threads there are on these cars.

Regards
Dermist

[jreacock]

Hi - yes, these kinds of tools are very useful to avoid damage. Problem I had here, was that the engine bolt hole was quite obscured by the two support plates, and it was impossible to get the calipers into. A parts book would be great for this kind of thing. Does such a document exist?

[Dermist]

Ahh I see your problem, i.e. obscured view of the thread.

The other alternative, and this is something that I am slowly amassing, is fine threaded nuts.  I keep one of each size and mark them up so as not to loose them and have to hand for reference / trying on a bolt / stud.

In my experience of a Dedra engine the fine threads used throughout are:

M8x1.0
M10x1.25
M12x1.5

Compared to standard 'coarse' threads which are:

M8x1.25
M10x1.5
M12x1.75

If the nut doesn't go by finger pressure, then further investigation is required.

Next level is to get some taps for the above threads, Carbon steel ones are perfectly ok for this as you are just cleaning out / repairing a thread form.  If you start creating a new thread then High Speed Steel taps and dies should be used.

Again cheap eBay ones are fine for simple cleaning out purposes.

Regards
Dermist

[jreacock]

Indeed. I've had to buy a few taps for cleaning out head bolt threads, brake calipers, etc. whilst I've been doing the car. M10 fine was one of them. Not to mention some heli-coil kits.

I've added the thread gauge to my EBay basket. It'll be useful for when I do the next one. Can't have too many tools.

[Leo HPE 1979]

IT IS m10*1,25 METRICAL FINE