If you use an ultrasonic cleaner, I have found that they work very well at getting in all the nooks and crannies of a die. Just remove the decapping pin, and drop the two pieces in the cleaner. Just be sure to re-oil EVERYTHING when done as the ultrasonic does clean every single surface.
It depends on how clean your brass is before sizing. When I notice some crud is getting on cleaned resized or finished brass it is time to clean all the dies. The dies for seating and crimping would need to be cleaned more often if you are loading lead bullets. I load just about all jacketed bullets and only clean all the dies at one time. Often when I need to clean one set I just clean all of them at the same time. Solvent and a bore brush does a pretty good job. I'm not using Lee dies. I use Dillon and RCBS but have no reason to think it wouldn't work for dies from any manufacture. Some dies do rust faster than others. A light application of oil on the outside slows that down. After oiling the inside I do run a dry patch through just like I would a gun barrel prior to shooting. The patches are on on old bore brush to help make contact with the sides of the die more positive.
I use a clean shoptowel on a small diameter dowel and spin the die by hand that usually will do the job. If they start to rust, into the tumbler they go for the day. Youd be suprised how nice the look when finished, then lighltly oil outside a nd return to die box.
I inspect each die with a bore light before set up in the press.
If they need cleaning - then they get cleaned.
If I am using lube then I clean after use.
I clean my dies with a towel on a dowel, I have no interest in starting over with a die that is not broke-in. I like the smooth finish, 100% contact is not a rough, burnished cross hatch finish.
There are exceptions, like ketone, aldehyde, phenol and carboxyl acid.
If brake cleaner was dangerous, I'd surely know it by now.
Been using it just about ever since it came on the market.
Before that it was kerosene and tar remover mix, followed by a mineral spirit wash.
I take the dies apart when I change calibers on the press...and clean them ( solvent and a patch is usually all they need )..../ but I only use a light "spray lube" ...Dillon spray lube on my cases...( just a little spritz goes a long way to make the press run smoother - don't need more than that in my view).
When I load one caliber....its usually 40 boxes or so ( call it 2,000 rds )...dies and press get cleaned...put dies and that toolhead back on the shelf so they're ready to go next time.../ change calibers and move on ....
Thing about brake cleaner (which I've learned from working on my motorcycles) is to make sure it's safe for o-rings...if not I would remove the rubber o-ring/spacer on the bushing. Same for the seating die if you use it on them. It's pretty toxic stuff!
We live in a "throw away society" . . . when your dies get dirty, send them to me and buy new ones . . . . :roll eyes:
I de-prime on a single stage with a universal de-priming die - and load on a Lee Classic 4 hole turret. Since I use the universal de-priming die, I remove the de-priming rod from my sizing dies. I just use a q-tip with solvent to clean as necessary. A bore brush would work well too.