Hand drilling in two soft metals

mfairleigh · Oct 22, 2020

My first post here and I hope such a basic question isn’t deemed silly here.

I have an air compressor that is leaking at the outlet fitting. This fitting is a 1/4” brass nipple, splined (not threaded) into an aluminum manifold. The leak is between the brass and aluminum. The nipple has some type of epoxy on it, apparently used as a sealant, that has failed.

The manifold is no longer available so if I screw this up the whole machine is ruined.

My thought was to drill & tap for a 3/8” to 1/4” brass reducer, then nipple out from there. But that will mean cutting the old nipple off at the manifold, drilling out the rest of the nipple, then drilling up to 9/16” for the 3/8” pipe tap.

I’m concerned about the drilling procedure. Should I increase the hole in small steps, or one big Hail Mary bite? With two different materials I’m concerned about not being able to keep the hole straight. Specialty bit(s)? Overthinking this?

I’m trying to follow photo instructions. The arrow points to the location of the leak. While there appears to be a gap between the nipple and the manifold, it’s no more than 1/16” deep so new sealant won’t get enough grip to hold pressure.

I’m losing sleep on this one

so any advice will be appreciated!

Mike

Rob F. · Oct 22, 2020

Use wicking loctite, maybe even from both sides if you can. Be sure to clean it as well as you can first.

If that fails then you can drill and tap it.

Is that the air outlet? If so then put a short flexible hose on it that ends at some sort of solid bracket or regulator. This is to keep any loads from you pulling or tripping on the hose from stressing this joint.
Like when you have 100' of hose out and need one more inch to get to the valve stem on that flat tire, it's OK, the hose will stretch that much and at the same time be side loading your compressor fitting....

DDoug · Oct 22, 2020

mfairleigh said:
My first post here and I hope such a basic question isn’t deemed silly here.

I have an air compressor that is leaking at the outlet fitting. This fitting is a 1/4” brass nipple, splined (not threaded) into an aluminum manifold. The leak is between the brass and aluminum. The nipple has some type of epoxy on it, apparently used as a sealant, that has failed.

The manifold is no longer available so if I screw this up the whole machine is ruined.

My thought was to drill & tap for a 3/8” to 1/4” brass reducer, then nipple out from there. But that will mean cutting the old nipple off at the manifold, drilling out the rest of the nipple, then drilling up to 9/16” for the 3/8” pipe tap.

I’m concerned about the drilling procedure. Should I increase the hole in small steps, or one big Hail Mary bite? With two different materials I’m concerned about not being able to keep the hole straight. Specialty bit(s)? Overthinking this?

I’m trying to follow photo instructions. The arrow points to the location of the leak. While there appears to be a gap between the nipple and the manifold, it’s no more than 1/16” deep so new sealant won’t get enough grip to hold pressure.

I’m losing sleep on this one so any advice will be appreciated!

Mike

A few questions:
1. What POS compressor is this ?
2. What tools do you have at your disposal ?

Bobw · Oct 22, 2020

9/16 straight up. Take your time.
As a general rule, drills aren't happy opening up
holes that are close to their size, 1/3 to 1/2 diameter
is about as big of a pilot as you want, and you should
already have that.

If it goes oversize, not really a big deal, you are putting
a pipe thread in there, you've got a ton of wiggle room on
size. You can go way over and still be fine.

DDoug · Oct 22, 2020

Bobw said:
If it goes oversize, not really a big deal, you are putting
a pipe thread in there, you've got a ton of wiggle room on
size. You can go way over and still be fine.

Huh ? I see a pot metal boss, that looks kinda thin as it stands.
Your going to drill that out "a ton" ???
What am I not seeing here ?

Hardplates · Oct 22, 2020

digger doug said:
A few questions:
1. What POS compressor is this ?
2. What tools do you have at your disposal ?

LOL

I think it's safe to assume an pneumatic drill is out of the question.

I think a new compressor might be a serious consideration.

Bobw · Oct 22, 2020

digger doug said:
Huh ? I see a pot metal boss, that looks kinda thin as it stands.
Your going to drill that out "a ton" ???
What am I not seeing here ?

I'm *assuming* there is enough meat there for a 3/8 pipe.

mjr6550 · Oct 22, 2020

Are you sure the fitting is not threaded into the manifold?

As Doug said, I would be concerned with how much metal if left. It is probably a cheap compressor, so maybe not much to loose if it does not work.

Maybe find a similar one on Craigslist and swap the manifold. Then you will have some spare parts for when the next part breaks.

mfairleigh · Oct 22, 2020

digger doug said:
A few questions:
1. What POS compressor is this ?
2. What tools do you have at your disposal ?

Yeah it’s a 25+ year old DeVilbiss-made craftsman DIYer machine. I know. But otherwise it’s a 1-owner machine, well maintained and in great condition (aside from the fact it’s leaking...).

Been a tool hoarder for 40 years, but haven’t begun to get into real metal work until recently. So I guess it depends.

And I’d love to drop for a new 80 gallon 2-stage, but that won’t happen right away.

DDoug · Oct 22, 2020

mfairleigh said:
Yeah it’s a 25+ year old DeVilbiss-made craftsman DIYer machine. I know. But otherwise it’s a 1-owner machine, well maintained and in great condition (aside from the fact it’s leaking...).

Been a tool hoarder for 40 years, but haven’t begun to get into real metal work until recently. So I guess it depends.

And I’d love to drop for a new 80 gallon 2-stage, but that won’t happen right away.

hobby-machinist.com is the place for you !

You still did not answer question #2

mfairleigh · Oct 22, 2020

mjr6550 said:
Are you sure the fitting is not threaded into the manifold?

As Doug said, I would be concerned with how much metal if left. It is probably a cheap compressor, so maybe not much to loose if it does not work.

Maybe find a similar one on Craigslist and swap the manifold. Then you will have some spare parts for when the next part breaks.

Yes. Since the nipple has flats I too assumed it was threaded, and about ripped the flats off with a flare nut wrench before realizing you can barely see the ends of the splines (zoom in).

I’m also concerned about having enough metal left. That’s one of my reasons for posting here, because it won’t take much slop in the drilling to ruin it.

If I could find another manifold I’d just go for it. But they’re like hen’s teeth.

Rob F. · Oct 22, 2020

Go re read post #2.

mfairleigh · Oct 22, 2020

digger doug said:
hobby-machinist.com is the place for you !

You still did not answer question #2

OK, I’ll take it over there. I’m not sure if you’re asking for an inventory of my tools, or what. If there’s one I need that I don’t have, I’ll consider getting it.

I appreciate everyone’s replies. I’ll give each one more thought, thank you.

mfairleigh · Oct 22, 2020

Rob F. said:
Use wicking loctite, maybe even from both sides if you can. Be sure to clean it as well as you can first.

If that fails then you can drill and tap it.

Is that the air outlet? If so then put a short flexible hose on it that ends at some sort of solid bracket or regulator. This is to keep any loads from you pulling or tripping on the hose from stressing this joint.
Like when you have 100' of hose out and need one more inch to get to the valve stem on that flat tire, it's OK, the hose will stretch that much and at the same time be side loading your compressor fitting....

This compressor sits in a basement shop, plumbed via rigid copper to two reels, one in the same shop, the other in the garage. Thank you for the suggestions.

Rob F. · Oct 22, 2020

mfairleigh said:
This compressor sits in a basement shop, plumbed via rigid copper to two reels, one in the same shop, the other in the garage. Thank you for the suggestions.

By plumbed to rigid copper do you mean to say the ridgid copper is connected directly to fitting on the compressor?

mfairleigh · Oct 22, 2020

No it’s connected to the copper by a 4’ rubber hose.

Illinoyance · Oct 22, 2020

It looks like a pretty simple manifold. If you screw up the existing one you could make a new one without much difficulty. Just don't try to make it look like the original. Another option would be to use a bunch of pipe fittings to make a manifold. Try the advice in post 2 before trying to modify the manifold.

mfairleigh · Oct 22, 2020

Illinoyance said:
It looks like a pretty simple manifold. If you screw up the existing one you could make a new one without much difficulty. Just don't try to make it look like the original. Another option would be to use a bunch of pipe fittings to make a manifold. Try the advice in post 2 before trying to modify the manifold.

Very interesting idea. Thanks!

dian · Oct 23, 2020

loctite 290.

DDoug · Oct 23, 2020

dian said:
loctite 290.

On many of these consumer grade compressors, that manifold get's quite warm.

I re-did one with ward 3/8" pipe fittings.
No more problems.

Hand drilling in two soft metals

Plastic

Diamond

Diamond

Diamond

Diamond

Stainless

Diamond

Aluminum

Plastic

Diamond

Plastic

Diamond

Plastic

Plastic

Diamond

Plastic

Stainless

Plastic

Titanium

Diamond

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