Quality of bolts

[Doehring]

Hi friends,

on top of most oem suspension's bolts there are numbers like 6, 7, 8 or 9. .I assume these are indicating the strength of the bolts. Unfortunately I can't find out how these numbers match the ISO-Standards where for metric screws/bolts

are defined by 5.8, 6.8, 8.8, 9.8 or 10.9. Does someone of you know the "translation" ?

What for instance is the quality of the 4 bolts that fix the rear crossmember to the link mount brace and the 4 bolts that fix the link mount brace to the body ?

I think too weak bolts are dangerous, esp. at the suspension !

Thank you in advance

Rolf

[John Coffey]

Those numbers have nothing to do with any SAE, ISO, or DIN fastener standards. They may have something to do with a JIC fastener standard but I'm not sure. Way back then, OEMs bought fasteners in such volume that they could specify their own fastener standards and thus delete any standardized markings on the heads.

When building suspensions under these cars I use class 10.9 fasteners or clean up and re-use good factory fasteners.

[AZ-240z]

Those numbers have nothing to do with any SAE, ISO, or DIN fastener standards. They may have something to do with a JIC fastener standard but I'm not sure. Way back then, OEMs bought fasteners in such volume that they could specify their own fastener standards and thus delete any standardized markings on the heads.

When building suspensions under these cars I use class 10.9 fasteners or clean up and re-use good factory fasteners.

John,

Do you happen to have a copy of Wick Humble's "How To Restore Your Datsun Z Car". On pages 97 and 158 Wick explains the relationship of those number, which he calls ISO, to Datsun Bolt-Torque Specs. Basically he says these ISO numbers bear no direct relationships to SAE numbers as they relate to torque value, but indicate a lower torque value than the SAE numbers.

I need to find out how to copy and paste and will try later if you don't have this book.

Dan

[Doehring]

Thank you, that will help. esp. as I got the mentioned tableau in between.

Rolf

[Carl Beck]

This might help:

http://euler9.tripod.com/bolt-database/22.html

#

ISO metric fastener material strength property classes (grades). As given in ISO 898-1, ISO metric fastener material property classes (grades) should be used. For example, fastener material ISO property class 5.8 means nominal (minimum) tensile ultimate strength 500 MPa and nominal (minimum) tensile yield strength 0.8 times tensile ultimate strength or 0.8(500) = 400 MPa. (In a few cases, the actual tensile ultimate strength may be approximately 20 MPa higher than nominal tensile ultimate strength indicated via the nominal property class code. Consult Table 10, below, for exact values.) Many anchor bolts (L, J, and U bolts, and threaded rod) are made from low carbon steel grades, such as ISO classes 4.6, 4.8, and 5.8.

#

See the bottom of the page for the table.

FWIW,

Carl B.

[Doehring]

Dear Mr. Beck,

your reply is most interesting, THANK YOU.

Do you agree with me that this thread is important to all of as we sometimes use the wrong bolts for our suspensions. As 10.9 bolts are difficult to get even here in Europe where the metric system is normal, we mostly use 8.8 bolts. Esp. at the front suspension there are 10.9ers at some places needed. I started thinking about that when I worked on my suspensions. Looking at the heads of the old bolts I saw the markers 4, 7 and 9 (or 6 ?) and I didn't know what metric bolt is the right to replace the OEM bolt.

Some of the bolts get an impact from the side, we call that "SCISSOR EFFECT". Someone told me, that a high strength like 10,9 is more sensible - and by that dangerous - to that cutting effect than 8.8 . Is that right or wrong?

Rolf

[BRYCE818]

Speaking of fasteners, can anyone recommend an on-line store where I can obtain correct yellow zinc-plated, hex head/phillips drive capscrews & bolts? Any help would be appreciated by this Zeophyte.

[Carl Beck]

Dear Mr. Beck,

your reply is most interesting, THANK YOU.

Do you agree with me that this thread is important to all of as we sometimes use the wrong bolts for our suspensions.

Hi Rolf:

We would really need a Mechanical Engineer, with experience in this area to get factual information.

Most certainly - Fastener selection is based on a number of criteria, but having the strength to do the job assigned, is most certainly one of the most important.

As 10.9 bolts are difficult to get even here in Europe where the metric system is normal, we mostly use 8.8 bolts.

Fasteners are designed to clamp something together. The loads or stresses that the assembly will have to bare, determine to a large extent the strength of the fastener required. For example, if the strength required equals one 10.9 grade bolt - the engineer might prefer to use two 8.8 grade bolts, because of common availability or cost considerations - if space allows two bolts, or if the load/stress is better distributed.

Esp. at the front suspension there are 10.9ers at some places needed. I started thinking about that when I worked on my suspensions.

If a 10.9 grade bolt is required - and if they are hard to find in your area - the best course of action is to order the bolt from the manufacturer (NISSAN OEM Parts).

Looking at the heads of the old bolts I saw the markers 4, 7 and 9 (or 6 ?) and I didn't know what metric bolt is the right to replace the OEM bolt.

Agreed. That is a problem. 4, 7, 6/9 could well be a manufacturer (the consumer in this case) specific code. With very large consumers as found in the auto industry, it is not uncommon for the manufacturer to define their own unique set of standards. Usually one or two fastener suppliers will produce products to meet the consumers specifications.

For example - "4" or "7" might refer to both the strength of the bolt, as well as any protective coatings and finishes applied - that Nissan specified at the time.

Some of the bolts get an impact from the side, we call that "SCISSOR EFFECT".

We call it Shear - the shear strength of a bolt is usually some percentage of its minimum tensile strength. Keep in mind that when two parts are bolted together - the side loads are carried by, or distributed across the parts themselves. The bolt doesn't carry the entire load. (ME's jump in here... if my general comments are completely out bed. This is just my perceptions from working with ME's and reviewing FEM results/reports etc. ).

Someone told me, that a high strength like 10,9 is more sensible - and by that dangerous - to that cutting effect than 8.8 . Is that right or wrong?

Rolf

I'm not sure I understand the question. Let's put it this way - the higher the tensile strength of the bolt, the more clamping force it can apply and hold. Higher clamping forces can sustain higher shear loads ( I would guess??).

Interesting discussion - but as I said - we really need an M.E. with specific knowledge and experience in this area.

FWIW,

Carl B.

[John Coffey]

As 10.9 bolts are difficult to get even here in Europe where the metric system is normal, we mostly use 8.8 bolts.

Try Wurth in Germany. It is a bit difficult to find some specific suspension bolts in class 10.9. The M10 1.25 pitch bolts that are most commonly used under the 240Z are common in class 8.8 but hard to find in class 10.9. Tacoma Screw Products has these bolts and nuts in class 10.9: http://www.tacomascrew.com/

Someone told me, that a high strength like 10,9 is more sensible - and by that dangerous - to that cutting effect than 8.8 . Is that right or wrong?

Probably wrong. There's a big gap between less sensible and dangerous. Without knowing the original strength of the fastener you cannot say what class of fastener is sensible or dangerous in a particular application.

[240ZX]

IIRC, the metric 10.9 bolts John is referring to are on par with an SAE grade 8 shear style bolt....very strong!!!!

Tom

[five&dime]

Bryce. Check the last two posts I made in this thread. I am not sure if he can help with suspension bolts but I would bet he can.

http://www.classiczcars.com/forums/showthread.php?t=30989&page=2

[z-spec]

Dear Mr. Beck,

your reply is most interesting, THANK YOU.

Do you agree with me that this thread is important to all of as we sometimes use the wrong bolts for our suspensions. As 10.9 bolts are difficult to get even here in Europe where the metric system is normal, we mostly use 8.8 bolts. Esp. at the front suspension there are 10.9ers at some places needed. I started thinking about that when I worked on my suspensions. Looking at the heads of the old bolts I saw the markers 4, 7 and 9 (or 6 ?) and I didn't know what metric bolt is the right to replace the OEM bolt.

Some of the bolts get an impact from the side, we call that "SCISSOR EFFECT". Someone told me, that a high strength like 10,9 is more sensible - and by that dangerous - to that cutting effect than 8.8 . Is that right or wrong?

Rolf

Rolf , overhere in Niederlande ( NL ) you can get whatever you need , i have a suplyer called FABORY , they have every thing in metric 10.9 12.9 with 1.25 and 1.00 mm pitch in hex and inbus , if you want i can sort out a catalog for you , Regards Adrian ,