Standard thread size on metric bolts?

[exSRAaron]

Stupid question, but what size is standard on motorcycle bolts? 1.25 or 1mm thread size? I'm guessing 1.25 but i wanna make sure.

[ReconRat]

The thread pitch will vary depending on the size (diameter) of the screw or bolt. There isn't a standard thread pitch in metric, like there is in SAE (24-coarse or 32-fine). If you see a 7mm or 8mm bolt with a 1.00 pitch, and a 7mm or 8mm bolt with a 1.25 pitch, it's because the metric standards had some mechanical errors when first developed, and had to be corrected. *cough* Last time I checked, there are over a dozen (more like 20) current metric standards for threads, versus one SAE standard. I'm guessing at 7mm or 8mm, because I think that's the one with the 10mm wrench head, that got changed. Old motorcycles will have the old standard pitch, and new motorcycles will have the new standard pitch. Supposedly the screw and/or bolt heads that have the little dot on them, are the new ones. But it's not always there. There are common standards, and I'm going to try and find a simple chart...

(pause for googling...)

ok, this will have to do, it's sorted by Tensile Strength:

http://euler9.tripod.com/bolt-database/23.html

It mixes in SAE, but look at the adjacent SAE equivalents, and see that typically a 24 thread per inch is coarse thread, and a 32 thread per inch is a fine thread. The metric equivalents do not use two standards. Instead each metric size is a strength equivalent. So the metric pitch could be anything.

Did this make sense? Yes, there are a lot of odd sized metric threads that will not work for your motorcycle. So be careful, when matching and using metric hardware.

edit: ok, I like this chart better;

http://www.carrlane.com/Catalog/index.cfm/29425071F0B221118070C1C513906103E0B05543B0B012009083C3B285357474A2D020609090C0015312A36515F554A5B

Notice that per ISO/ANSI metric standards, there are additional thread pitch available for some diameters. Having two pitches for one diameter in metric, satisfys the strength requirements when trying to handle both coarse and fine equivalents. It's not likely that you would find them mixed on a motorcycle, unless it's a component that was manufactured by a sub-contractor.

Edited March 11, 2009 by ReconRat

[exSRAaron]

thanks!

[Earache]

Most 10mm bolts are 1.25 pitch (considered "fine") on Japanese bikes. The typical pitch on a 10mm is 1.50.

8mm are usually 1.00 pitch

6mm are usually .80 pitch

Get yourself a pitch gauge - they're really inexpenive and save you a lot of grief.

See: http://www.wttool.com/product-exec/product_id/17025/nm/Metric_Screw_Pitch_Gages_Starrett_

This one costs a bit as it's a Starrett, you can get them for about $6 at most hardware stores.

[exSRAaron]

Most 10mm bolts are 1.25 pitch (considered "fine") on Japanese bikes. The typical pitch on a 10mm is 1.50.

8mm are usually 1.00 pitch

6mm are usually .80 pitch

Get yourself a pitch gauge - they're really inexpenive and save you a lot of grief.

See: http://www.wttool.com/product-exec/product_id/17025/nm/Metric_Screw_Pitch_Gages_Starrett_

This one costs a bit as it's a Starrett, you can get them for about $6 at most hardware stores.

It seems like getting M8 in 1.00 pitch is harder then 1.25? MSC only supplies the screws I need in 1.25

[ReconRat]

yeah, pitch gauge, very useful. I sometimes cheat and get out the tap and die set to match them up, heh.

edit: I don't mean re-cut them! I mean use them to check the pitch!

Edited March 11, 2009 by ReconRat

[Artmageddon]

Recon, you are just full of handy dandy info. Not only do you answer questions, but you give the reasoning and technical data to back it up.

I think that is just really cool of you to do. You've already helped me out a few times!

The thread pitch will vary depending on the size (diameter) of the screw or bolt. There isn't a standard thread pitch in metric, like there is in SAE (24-coarse or 32-fine). If you see a 7mm or 8mm bolt with a 1.00 pitch, and a 7mm or 8mm bolt with a 1.25 pitch, it's because the metric standards had some mechanical errors when first developed, and had to be corrected. *cough* Last time I checked, there are over a dozen (more like 20) current metric standards for threads, versus one SAE standard. I'm guessing at 7mm or 8mm, because I think that's the one with the 10mm wrench head, that got changed. Old motorcycles will have the old standard pitch, and new motorcycles will have the new standard pitch. Supposedly the screw and/or bolt heads that have the little dot on them, are the new ones. But it's not always there. There are common standards, and I'm going to try and find a simple chart...

(pause for googling...)

ok, this will have to do, it's sorted by Tensile Strength:

http://euler9.tripod.com/bolt-database/23.html

It mixes in SAE, but look at the adjacent SAE equivalents, and see that typically a 24 thread per inch is coarse thread, and a 32 thread per inch is a fine thread. The metric equivalents do not use two standards. Instead each metric size is a strength equivalent. So the metric pitch could be anything.

Did this make sense? Yes, there are a lot of odd sized metric threads that will not work for your motorcycle. So be careful, when matching and using metric hardware.

edit: ok, I like this chart better;

http://www.carrlane.com/Catalog/index.cfm/29425071F0B221118070C1C513906103E0B05543B0B012009083C3B285357474A2D020609090C0015312A36515F554A5B

Notice that per ISO/ANSI metric standards, there are additional thread pitch available for some diameters. Having two pitches for one diameter in metric, satisfys the strength requirements when trying to handle both coarse and fine equivalents. It's not likely that you would find them mixed on a motorcycle, unless it's a component that was manufactured by a sub-contractor.

[Earache]

It seems like getting M8 in 1.00 pitch is harder then 1.25? MSC only supplies the screws I need in 1.25

Go to McMaster-Carr - they have it all: www.McMaster.com/

If you need it right now, go to the local Fastenal store. They have a decent selection of stuff in stock and can get almost anything in 1 day.

[exSRAaron]

K thanks guys, I'm gonna check out fastenal tomorrow. theres one right down the road. Very helpful group here!

[ReconRat]

I take back the idea of only one pitch used on a motorcycle. Some bolts are sometimes different, for a reason. Like I said, have to check first.

Typical "fine" metric thread used like on a Flange Hex machine screw (bolt) typical of a headbolt, etc;

M5x.8mm

M6x1mm

M8x1.25mm

M10x1.5mm

M12x1.75mm

M16x2mm

Typical "coarse" metric thread used like on a standard hex machine screw(bolt), typical of a body part, etc;

M5x.8mm

M6x1mm

M7x1.25mm

M8x1.5mm

M10x1.75mm

M12x2mm

M14x2.5mm

M16x3mm

Typical metric thread for phillips panhead and allen head machine screws;

M5x1mm

M6x1.25mm

M8x1.5mm

and variations of anything, who knows... lots of variations for special.

note: a screw is a fastener threaded all the way up near the top, a bolt has a shank of unthreaded shaft, used for shear applications. But not everyone or every hardware catalog will agree with that.

edit: it was late, so I make this clear. This list is typical of what would be found in a local hardware store. It won't be exactly what is found on a motorcycle. I don't think the pan head screws would have a different thread than the bolts. On a motorcycle all the thread types would be the same almost everywhere. I don't really remember finding mixed thread types for an individual size of screw or bolt.

Edited March 11, 2009 by ReconRat
added stuff