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Lubricant for tapping upward into aluminum

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I'm asking because my search found this old thread here, on tapping aluminum:
I'm starting a new thread because that one is from 2017.
I need to tap (upward) 3/8"-16 threads into an existing 5/16" hole in an aluminum casting.  I'll be tapping 1/2" into a blind hole, so the shavings will not come out the back.
The interesting part, is that I'll be tapping upward into the hole.  The casting is part of the frame of an aluminum bodied car, so I can't remove the casting and put it on a workbench, to tap downward into it.
So liquid will run down out of the hole, away from the cutting edges.

What lube would be good here?
Most of the lubes I've seen suggested for cutting aluminum are quite thin and will run right back out the hole.
WD-40 has a good reputation for use in cutting aluminum, but it's runny.
One suggestion in the linked thread was Vaseline, another was KY jelly (really!).
Any other suggestions on this?


I already know I need a sequence of taps: taper, plug, bottoming, to put threads in the bottom of the hole.  Depending how that goes, I also will have some self threading bolts, which should cut all the way to the very bottom (top!) of the hole.  And I know I need to cut in about 1-2 turns, then back out, to get the shavings out.

ethanol, it doesn't really matter that it is runny, the tap just need to be "wet"

Super Tapping Fluid from CRC is a spray with foamy texture. Of course if you apply too much it turns liquid

Stray Electron:
  It's not going to really matter if the cutting fluid is runny or not, just as long as you get it up inside the hole where the cutting action is taking place. The reason why it doesn't matter is because that you need to back the tap out (about once per revolution?) and clear the cuttings off and re lubricate the tap.  Kerosene is a good lubricant for tapping aluminium. WD-40 is mostly kerosene and will work also. I would get a small container of kerosene and dip the end of the tap in it and get the threads started and then periodically back the tap out and wipe or brush the cuttings off of it and then redip it in kerosene and then go back to tapping the hole. 

   As your tap gets deeper in the hole and the nearer that you get to the bottom of a blind hole, the more that you need to clear the chips from the tap.  The LAST thing that you want to happen to jam the tap with chips and have to it seize in the hole!!   If some chips cling up inside of the hole you could use something like WD-40 in a spray can with one of those long thin tubes on it and spray that up into the hole to relubricate the material and to help blow some the chips out of the hole.

  I would use WD-40 or kerosene before I'd use Vaseline!  Vaseline is sticky and will probably make the chips cling to the inside of the hole and to the tap.  You want them to fall out and get out of the way of the tap.

  Do NOT use any kind of chlorinated solvent for lubricating aluminium when you're using steel tools! 

I think that foam stuff is good, IDK if they have it for aluminum but the one that CRC sells for drilling is excellent. But it does drip you put a bucket under what you are doing because it makes a mess

I used it to drill aluminum without problems and probobly tapped some holes too, I don't think it was a problem. I would only worry about it if you are doing alot of holes like in production

I bet even that wd40 foam gel spray would work

its like shaving cream that is less stable (the CRC one), the wd40 gel spray might even be a bit less stable, I think the CRC holds foam shape better

if its upside down I would just spray it into the flute of the tap while working periodically


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