Heat treating machined aluminum gear case
Heat treating machined aluminum gear case
(OP)
I am getting ready to machine an approximately 8" x 12" gear case out of 6061-T6 extruded billet (3" thick billet). I will be removing a lot of material to create basically a shell case of about 0.2" thick, with stiffening ribs and bearing pockets.
I would like to maintain fairly tight tolerances for proper shaft alignment and proper sealing of the case halves. What kind of stress relieving processes should be performed? Should stress be relieved prior to, during, or after the machining process? How does this affect the T6 heat treat that has already been performed on the material?
I would like to maintain fairly tight tolerances for proper shaft alignment and proper sealing of the case halves. What kind of stress relieving processes should be performed? Should stress be relieved prior to, during, or after the machining process? How does this affect the T6 heat treat that has already been performed on the material?





RE: Heat treating machined aluminum gear case
RE: Heat treating machined aluminum gear case
RE: Heat treating machined aluminum gear case
why not just rough machine
stress relieve
then finish up
T6 will machine easily
RE: Heat treating machined aluminum gear case
RE: Heat treating machined aluminum gear case
Does this make any difference?
What are advantages and disadvantages of rough machining, letting sit for 2 weeks, then finish machining?
RE: Heat treating machined aluminum gear case
according to the old MIL-H-6088 which is now obsolete
replace by AMS-H-6088 -T6511 is aged extrusion.
Did you receive certifications? what is the requirement.
do you need -T6511 ?
can you return the material or is it rough cut?
it just time if you have it.
an other suggestion is to
rough machine
re anneal to T4 condition
re solution age T6
finish machine
there of course would be added cost for re heat treating.
best bet like swall said buy in T4 condition
then age to T6
RE: Heat treating machined aluminum gear case
Let's say I do method 1) from swall above (rough machine equally from both sides, then finish machine)
How many times should I flip back and forth? 2? 4? 8?
Any ideas on how much distortion I might expect? 0.001" change in flatness across the mounting face? .01"? 0.1"?
RE: Heat treating machined aluminum gear case
RE: Heat treating machined aluminum gear case
My recommendation to let the part rest for two weeks before final machining is based on ASM metals handbook version 8 (~1970). 30 years ago we used this method it for a very accurate gear pump aluminum case. Therefore, using swall recommendation for rough machining sequence and the two weeks rest may be sufficient.
Are you the machinist or you give it to a third party?
The clamping method is also a major factor in the machining process. The clamping method should be such that it will minimize the stresses on the part.