Hi,

I have just come to take the brake backing plates off my english axle, to find it is held on with four allen head bolts, of unknown size.

the wheel nuts were metric, but these allen key bolts seem to be a funny size. anyone know what size they are? As the world of imperial measurments is a dark and mysterious place for me....

Thanks!

Should be 5/16" UNF set screw bolts ie normal 1/2" AF heads not allen screws.
And they should be fitted using springs washers.

here is a pic
Rescued attachment 101_0596.JPG

http://www.namrick.co.uk/browse.asp?PCID=5

Hex Set Screws (NB Set screws NOT bolts)
Bright Zinc Plated to BS 3382, (High Tensile Grade ’S’’

5/16" dia
3/4" or 7/8" Long

MUST use washer under the heads 1 plain & 1 spring.

See http://www.namrick.co.uk/browse.asp?PCID=13
Rescued attachment 1_2.gif

Silly question - cause i've wondered this often.

Does it make a difference if you do
plain washer, spring washer, bolt head
or
spring washer, plain washer, bolt head?

To me the risk is the spring washer may mark the peice you're putting hte bolt in, but you're also more likely to have the spring washer bigger than the bolt head so i'd suggest the latter is better. Am I right?

(i know spring washers aren't classed as being very good by some people)

Spring washer should be in contact with the bolt head, plain washer goes between the spring washer and the surface you are bolting.

Main purpose of a spring washer is to stop the bolt undoing.
A plain washer spreads the load to reduce the stress directlt under the bolt..

In this case washers are essential mainly to be 100% sure the bolt isn't thread bound and the thin metal plate that holds the bearing in dosen't distort.

Looking at your picture the allen key bolts "look" like 7mm, may be wrong but worth a try. HTH Ray