Questions - especially for John D

I've got some new bolts for my bottom arms - the outer end 4 off 7/16" x 3" long.

They have 3 raised lines pointing towards the centre of the head, and a capital letter "L" between 2 of the lines. Is there any way of knowing what spec they are?

Also, the bracket they screw in to is threaded, is there any point adding the nut as well, apart from it acting as a lock-nut?

Cheers

I would definitely use the nut, without it there's nothing to stop the bolt undoing !!

These are the markings found on imperial bolts.



I'm not sure what the 'L' signifies but if they really are only Grade 5 I would not advise using them.

Since they are in single shear I went for the strongest bolts possible and bought NAS aerospace spec bolts. Make sure you get the grip length correct. They should tighten securely into the swivel hub bracket. You should also definitely use the nuts on the inner end to lock them in place.

Thanks for the info guys.

It does look like they are grade 5. I'll use them for now cuz it won't be driven in anger for a few weeks, then swap them before MOT.

Grade 5 is generally considered equivalent to the familiar 8.8 grade. Grade 5 is actually fractionally stronger.

Iain

For comparison these are the tensile strengths of the different bolt grades.

SAE Grade 5 120,000psi

SAE Grade 8 150,000psi

AN (aerospace) 125,000psi

NAS 1300 series (aerospace) 160,000psi

NAS 6200 ans 6600 series 180,000psi

In addition to their high tensile strength NAS bolts also have a safer 'fail' mode in that they will bend before they break unlike normal HT bolts which are brittle. They are generally more corrosion resistant than normal HT bolts too.

NAS bolts are sized in increments of 1/16" in both their grip length (un-threaded length) and their diameter.

They are ordered by a part number. The first 2 digits are the bolt series, the second 2 digits are the bolt diameter in 1/16" and the final two digits are the grip length in 1/16" so a bolt with a part number of

NAS 1306 - 24

would be NAS series 1300 measuring 3/8" diameter (6 x 1/16") and would have a grip length of 1.5" (24 x 1/16").

The length of the threaded section is the same on all NAS bolts except the 1100 series which have a shorter threaded section for a 'K' nut.