Re: Girling AR Calipers - help required
Posted: Wed Aug 18, 2021 1:31 pm
Regarding the flex of period AR calipers (causing wedged shape wear of the pads and premature change requirements), I was sorting through the parts of my GTS project and realized they were marked with the alloy type : LM4
I checked around a bit e.g. http://www.nortal.co.uk/LM4/
" Heat Treatment
This alloy's response to heat treatment is dependent on the presence of Magnesium; therefore for such treatment, the Magnesium content should be near the maximum.
A very considerable increase in mechanical properties is obtained by Solution heat treatment and artificial ageing.
LM4-TF (fully heat treated) -Heat for 6-16 hours at 505-520°C, quench in hot water and heat for 6-18 hours at 150-170°C and air cool.
If bending or straightening of castings is necessary, this should be carried out after the solution heat treatment, since in this state the castings exhibit greatly increased ductility.
"
so wondered if there is a way to find out whether the period calipers were originally heat tempered or still held that temper, then if re-tempering could be attempted (esp. after being machined into a finished part: would that likely alter the specs and tolerances rendering it useless ? )
I checked around a bit e.g. http://www.nortal.co.uk/LM4/
" Heat Treatment
This alloy's response to heat treatment is dependent on the presence of Magnesium; therefore for such treatment, the Magnesium content should be near the maximum.
A very considerable increase in mechanical properties is obtained by Solution heat treatment and artificial ageing.
LM4-TF (fully heat treated) -Heat for 6-16 hours at 505-520°C, quench in hot water and heat for 6-18 hours at 150-170°C and air cool.
If bending or straightening of castings is necessary, this should be carried out after the solution heat treatment, since in this state the castings exhibit greatly increased ductility.
"
so wondered if there is a way to find out whether the period calipers were originally heat tempered or still held that temper, then if re-tempering could be attempted (esp. after being machined into a finished part: would that likely alter the specs and tolerances rendering it useless ? )