[RCHolic]

Just an FYI.

The industry standard for imperial thread sizes to be called out are in this form:

Nominal size x Threads per Inch x Length.

For metric screws the industry standard is slightly different. If you want a coarse thread you call it out like this:

Nominal size x Length. (Coarse thread is understood)

If however, you need a fine pitched thread on a metric screw then it is called out like this:

Nominal size x Pitch (length of one full thread) x Length.

I have been "talked to" by people who think otherwise and expect the pitch of the thread to be called out ir-regardless. But I am simply following the design standards.

To make it simple, if you are dealing with a metric thread the first number is always the nominal size of the fastener and the last number is always the length. If you have a number inbetween then you need to be more careful of what you ask for, because you always get what you ask for but not always what you want.

[voyager_663rd]

This is going a bit further than my original question which was just about lengths. I have not gone out to try to find anything yet although I'm sure that the LHS would have them. As anyone else would, I was just trying to find them cheaper than what the LHS would sell them for.

I really appreciate the offers made here. However, I couldn't accept them because I haven't actually tried to physically find what I need yet.

These 4 bolts were to replace the existing ones I have for my rcv. The rcv is somewhat shorter than a conventional engine and in order to have the prop extend past the cowl, I need to add a 3/4" maple engine spacer (ie: block of wood) to the firewall. That effectively doubles the length of bolt needed (goes into a metal backing plate that has built-in blind nuts--not really blind nuts but threaded collars that are fastened to the backing plate).

Again, I appreciate your offers. I was just looking for info so when I do go to the store, I will know what I want and won't look like a total idiot asking for something that doesn't exist.

[abcool]

Hi voyager try home hardware in town i was lookng for some bolts earlier in the year to refastner the muffler on my engine i know they carry 4 mm crappy tire didn't.or at least not long enough to be useful.

[voyager_663rd]

You know Alan, you are absolutely right. I have found stuff in there that NO ONE else had.

Plus it's great to patronize local stores. The folks at HH really go out of their way to help too.

[moo]

I have been "talked to" by people who think otherwise and expect the pitch of the thread to be called out ir-regardless.

one more 'talking to' couldn't hurt!

how about the DIN number, material, diameter, length

DIN 912 A2 M 4X50

[RCHolic]

You most certainly can get into the nitty-gritty, but unless you are designing something that is critical, the assemblers generally only want the basic callout so they can grab whatever they have in the shop. But I do agree that if the entire callout was used then there can be no question as to what is to be used, but everyone needs to be a little flexible in order to get along and get the work out.

P.S. If we were talking rocket science here then you most certainly need a more detailed callout.

[Guest]

Ok, lets get specific.....

Straight from the Machinery Handbook....the bible of anyone doing mechanical design...pg 1774, 26th edition.

Metric Screw Thread Designations

Metric screw threads are identified by the letter (M) for the thread form profile, followed by the nominal diameter size and the pitch expressed in millimeters, separated by the sign (X) and followed by the tolerance class separated by a dash (-) from the pitch. ie: M6x1 - 4g6g

The simplified international practise for designating coarse pitch M profile metric screw threads is to leave off the pitch. Thus a M14x2 thread is designated just M14. However, to prevent misunderstanding, it is mandatory to use the value for pitch in all designations.

Are we all happy now

Voyager, just go look for an M4x50.

[Vulcan1]

If you really want to get into it you could also get into what side of the big pond they come from. I really hate the system for metric bolts and screws as they still are not standardized to me especially the smaller sizes. You may think they are but ask the heli guys why they have to sometimes order special threads when they lose one.
M4 is usually the standard for Home or other suppliers to have in stock, but anything smaller your best bet is a bolt supplier. I also when purchasing small sizes like to get stainless steel as they last a lot longer and will take more torque. The only problem is they don't shear like the hardware store types and if you use it for like muffler mounting could tear the ears off or worse take a chunk out of the side of the engine. They are usually grade 5 or less and the allen type are 8 and up.
To make things easier you could also tap it out to 8/32 or 10/24 and in the end will probably save a trip.
Just my opinion on this as I know the different grades and types but they get confusing in the small sizes. Maybe when they get done there so called conversions the sun will come up in the west also. Oh Heck thats mother nature and they have already played havoc with her.
John

[moo]

M6x1 - 4g6g

CAN/CSA-B78.2-86 7.18.1.3 (page 35)

I have a photocopy of the CSA standard for dimensioning and tolerancing technical drawings, but the machine shop would call me stupid for such over-specifying.

M6 x length would be acceptable to 99.5% of this audience, and if I cannot find the length, I cut it with my dremel*.

(* actually a Black and Decker rotary tool)

Brafasco is good too, I seem to remember a minimum charge there.

[Noin]

You guys have too much time on your hands.

Check out the thread labelled CL-215 game and go have some fun.