Ice water
Thats right,ice water.
I have seen this subject come up on forums several times & cant keep this secret anymore.
I first heard of this back in 2005 while shooting at Hawks Ridge & I dont think they will mind if I pass this information along to you here today.
Get a bowl or a small cooler & fill it with ice & water. Put your K&M neck turning tool with the carbide mandral in the ice water.
Now while your turning tool is getting cold,expand your necks with the expander that K&M makes for the case/caliber that you will be turning.
Do not substitute this mandral for other brands as they are made for each other.
The idea of the ice is to reduce the heat induced by friction on the mandral & cutter while turning.
The water serves as the only lubricant you will need if you use carbide mandrals.
Pull the turning tool out of the water & turn your case.
Put the turning tool back in the ice water while changing cases so the mandral can cool off as it was when you started turning the previous case.Then turn the next case in the same manner.
This will make very consistant necks without galling your brass & clean up is as easy as letting your cases dry over night.
For the most consistant necks I turn to .001" of what I need on the first pass then go back & finish them on the 2nd pass in lots of 50 pieces using the same method, this will produce a case neck consistant to .0001".
Everyone I know who has tried this method is still using it today, it works.