Bolt Diagnosis

[Gazz]

https://scontent.flhr2-1.fna.fbcdn.net/v/t1.0-0/p480x480/92514442_10158087897027768_9032131256426430464_o.jpg?_nc_cat=103&_nc_sid=8024bb&_nc_ohc=l-wFj4JMnbQAX-MQcPV&_nc_ht=scontent.flhr2-1.fna&_nc_tp=6&oh=d25a4e68c70325682677976b55d30d12&oe=5EB4F216

https://scontent-lhr8-1.xx.fbcdn.net/v/t1.0-0/p480x480/92667940_10158087895687768_7024624930520039424_o.jpg?_nc_cat=109&_nc_sid=8024bb&_nc_ohc=mbUceU6UOEkAX9iZmyI&_nc_ht=scontent-lhr8-1.xx&_nc_tp=6&oh=b7c1e1105749ae45fa2b34ae5ce6b1a8&oe=5EB47F72

Could someone please advise what size of bolt I need to order in terms of pitch, etc?

[stinkwheel]

Looks like an M4 x 16mm button head set screw.

However, the head seems unusually large, possibly specific to that piece, so you might want a flange head to get the width (although it isn't actually a flange-head). Depending on the application. So you might want ot tell us what and where it's off.
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[Gazz]

Its the bolt to hold my bike seat down.

You need to wedge an allen key underneath the cushioning of the seat to feel for the head and then push against the seat material while turning the allen key to get the seat off. Very time consuming finding the head of the bolt, so I'm looking to either get longer bolts or an eye bolt to make the process a little easier.

A lot of guys on the Triumph forum just take the bolts out altogether.

I done something similar a few years ago with the fairing of a dirtbike to get quick access to the battery for charging.

There's a few eye bolts advertised on ebay, etc that doesn't specify the thread pitch. Are all m4 bolts a standardised pitch?

[Riejufixing]

[Kawasaki Jimbo]

£5 gauge.

[Bhud]

It's always nice to have a tray on hand full of nuts and bolts. Whenever I go down to B&Q, I fill one of those little bags with various sizes and lengths of hex-head bolts. 6 or so of short and long M4, and of M5, and of M6, etc.
For non-structural applications such as your seat-retaining bolts, I don't have a problem with using shiny zinc-plated bolts from the hardware store. It's ridiculous just buying them one at a time "on need" unless you're after something specific (usually the big ones, e.g. M11, M14).

[WD Forte]

I'll have 50p each way bet its actually an M5x16
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[Raffles]

Crap pics Gazz but I'm going for M5 standard pitch.
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[Riejufixing]

[stinkwheel]

[Riejufixing]

[stinkwheel]

[steve the grease]

It looks a little bit offset to the left, I'd go with M5.
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All the above is my personal opinion, you can see my lips move, but I'm talking out of my arse.
I've been riding, and fixing , bikes for 50 years, in that time the more I learn, the less I am absolutely sure of.....

[ZebraDriver]

Be careful if your buying bolts from B&Q. I was helping someone recently with a small project and he had bought some M5 bolts in one of the wee packets from there. We had to tap holes in the parts he was making when we tried the bolts he had bought they wouldn't fit, after checking we discovered that the bolts were M5 x 0.9 (and were labelled as this). I've never seen M5 x 0.9 before and its not a recognised size...….

[-]

There are 6 threads to every 5mm, and 18 to 15mm, so i'm going for M5X16mm with a 0.8mm coarse thread.
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[MCN]

It's not 4mm
It's 5mm with 0.8 pitch


https://www.carbidedepot.com/formulas-tap-metric.htm
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Riejufixing]

[WD Forte]

Looking at it another way
M6 for lightweight fixings yep we've all seen that lots of times
find em everywhere.
M5 for trim and even lighter fixings, yep seen that
M4?
Dont know every bike of course but
I cant recall ever finding an M4 on a bike unless it was
part of say an instrument/switch assembly.

Special thread just to hold a seat on? why?

Can I have my five ponds in deliverable food coupons please?
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bikers smell of wee

[Bhud]

[WD Forte]

To stop all this quibbling and dickering I decided to
measured it myself with proper tape measure and its an M20x70

M4 my arse

photographic evidence

https://imgur.com/8Qo72J0.jpg
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bikers smell of wee

[stinkwheel]