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-12AN drill bit size for bulkhead fitting

7K views 12 replies 9 participants last post by  Gmsmkr 
#1 ·
I have a -12AN bulk head fitting. What drill bit size do I need to use to tap the hold for that thing? I've Googled it and got several answers. I gave up and decided to ask the experts. Thanks in advance.
 
#4 · (Edited)
Mcmaster has one for $60 - I'm sure you can find one cheaper.

BTW, if you 45° bevel the hole, turn the thread off the seal area, use the appropriate AN o-ring, it will seal. Think o-ring fuel fittings. Your threads will be wetted so consider corrosion - think dissimilar metals, water, alky, or modern pump gas


But you gotta ask yourself - How bad do you want to do this :)
 
#5 ·
Thanks for the replys.

It is a bulkhead fitting with a nut that goes on the back. I'm not screwing the bulkhead fitting into the hole itself. The nut will go on the backside.

I have a new set of valve covers and I wanted to put the bulkhead fitting in them to attach my vacuum pump hose. I just was having trouble finding the drill bit size online.

I'm just hoping that Harbor freight has a cheap one since it will be a dang near one time use for the drill bit.
 
#8 · (Edited)
Thanks for the replys.

It is a bulkhead fitting with a nut that goes on the back. I'm not screwing the bulkhead fitting into the hole itself. The nut will go on the backside.

I have a new set of valve covers and I wanted to put the bulkhead fitting in them to attach my vacuum pump hose. I just was having trouble finding the drill bit size online.

I'm just hoping that Harbor freight has a cheap one since it will be a dang near one time use for the drill bit.
I went through this when I built new lug nuts for my Rail (11/16" stud). I bought the tap from Speedway Motors. They have a pretty good selection of bits and taps.
Rob
 
#7 ·
Take a dial caliper and use the narrow tips of the caliper and measure the bottom of the thread then take a few thou off that number or go to the next common drill size down. The reasonably thin aluminum will tap pretty easily.
Personally, if it were me, I'd drill and tap a slug of aluminum and weld it to the cover, it'll be a lot stronger than just trying to thread the thin cover.
Rob
 
#10 ·
"It is a bulkhead fitting with a nut that goes on the back. I'm not screwing the bulkhead fitting into the hole itself. The nut will go on the backside."


Is there room for the nut on the underside? Will the end of fitting hit rocker's or stud girdle? Will nut work it's way loose and fall in?

X2 on Unibit, lots of future uses for that tool.
X2 on welding fitting, won't come loose, won't leak, not as tall after installation, internal baffold can be used under it.
 

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#12 ·
Do a google search for "welding shop" in Georgetown, IN. something close will pop up. I wouldn't trust JB Weld to hold the weight of the hose or seal for the long term.
There are AN tank fittings that are best suited for this application but any fitting can be used, you just need to remove (sanded or wire wheel) the colored or clear anodizing before welding. I drilled the hole the same size as the I.D. of the fitting so the fitting sits on the surface not into it, it welds better this way.
 
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