Several years ago, on ebay, I bought a couple of German military truck
surplus air reservoir tanks.

These tanks have 3 threaded holes. Two are at one of the heads and
the other is mid-way along the cylindrical portion.

I would like to plug these holes and drill and tap the plug so that it
will take standard American air fittings. The objective is to create
a dry air tank to run a plasma cutter and/or air tools.

I'm not a machinist and I don't have any measuring tools. So I'm not
sure about the diameter of these holes but I'm pretty sure they're
M20x1.5 or M21x1.5. I have found European sources for blind plugs in
these dimensions but have not yet found a source in the USA.

A 7/8" bolt will not fit in the hole and a 3/4" bolt will not touch
the sides. This is my basis for thinking the holes are 20 or 21mm.
The thread pitch seems fairly fine so I'm guessing it's 1.5mm.

I'm open to suggestions as to other approaches to plumbing the tanks
so that I can use standard compressed air disconnects with them. I
weld but I don't consider myself competent to weld on pressure
vessels.

Any thoughts?

Thanks,

Vernon

On Jun 12, 7:45*pm, Vernon wrote:
Several years ago, on ebay, I bought a couple of German military truck
surplus air reservoir tanks.

These tanks have 3 threaded holes. *Two are at one of the heads and
the other is mid-way along the cylindrical portion.

I would like to plug these holes and drill and tap the plug so that it
will take standard American air fittings. *The objective is to create
a dry air tank to run a plasma cutter and/or air tools.

I'm not a machinist and I don't have any measuring tools. *So I'm not
sure about the diameter of these holes but I'm pretty sure they're
M20x1.5 or M21x1.5. *I have found European sources for blind plugs in
these dimensions but have not yet found a source in the USA.

A 7/8" bolt will not fit in the hole and a 3/4" bolt will not touch
the sides. *This is my basis for thinking the holes are 20 or 21mm.
The thread pitch seems fairly fine so I'm guessing it's 1.5mm.

I'm open to suggestions as to other approaches to plumbing the tanks
so that I can use standard compressed air disconnects with them. *I
weld but I don't consider myself competent to weld on pressure
vessels.

Any thoughts?

Thanks,

Vernon

Here is a link to a European supplier: http://www.farnell.com/datasheets/42155.pdf

This plug is made of brass. If it fits my tank would brass be
suitable material for drilling and tapping so that I can use standard
SAE air hose fittings?

Thanks,

Vernon

Vernon Tuck wrote:
Here is a link to a European supplier: http://www.farnell.com/datasheets/42155.pdf

This plug is made of brass. If it fits my tank would brass be
suitable material for drilling and tapping so that I can use standard
SAE air hose fittings?

Thanks,

Vernon
They don't look thick enough to tap. Notice the extra "depth'
where the threads are now.
...lew...

On Jun 12, 9:56*pm, Lewis Hartswick wrote:
Vernon Tuck wrote:
Here is a link to a European supplier: *http://www.farnell.com/datasheets/42155.pdf

This plug is made of brass. *If it fits my tank would brass be
suitable material for drilling and tapping so that I can use standard
SAE air hose fittings?

Thanks,

Vernon

They don't look thick enough to tap. Notice the extra "depth'
where the threads are now.
* * ...lew...

I was worried about the same thing. Since posting, I've found this:
http://www.grainger.com/Grainger/items/5MUE5

It is a drain plug used on various cars during the 70s and 80s.
Grainger has a pack of 5 for $15. I may try to order a single one
from a local auto parts place to make sure it is the right diameter
and pitch. If so, the idea would be to chuck 'em into a lathe, drill
out the center, then countersink and tap a hole into which to thread a
standard air hose quick disconnect fitting.

V

On Sat, 12 Jun 2010 18:13:36 -0700 (PDT), Vernon Tuck
wrote:



I'm not a machinist and I don't have any measuring tools. *So I'm not
sure about the diameter of these holes but I'm pretty sure they're
M20x1.5 or M21x1.5. *I have found European sources for blind plugs in
these dimensions but have not yet found a source in the USA.


These seem to be intended for use as conduit fittings, but the threads
are right:
http://www.sealconusa.com/strainreli...0_1_2_npt.html
http://www.novamaxindustrial.com/adapters.htm

McMaster has some as well, but a quick look showed only very expensive
high pressure SS fittings there.

4822T45
Extreme-Pressure SS Threaded Fitting M20 X 1.5 Male X 1/2" NPT Female
Adapter, 5000 PSI
In stock at $46.63 Each

--
Ned Simmons

On Jun 12, 11:46*pm, Ned Simmons wrote:
On Sat, 12 Jun 2010 18:13:36 -0700 (PDT), Vernon Tuck

wrote:

I'm not a machinist and I don't have any measuring tools. *So I'm not
sure about the diameter of these holes but I'm pretty sure they're
M20x1.5 or M21x1.5. *I have found European sources for blind plugs in
these dimensions but have not yet found a source in the USA.

These seem to be intended for use as conduit fittings, but the threads
are right:http://www.sealconusa.com/strainreli...m/adapters.htm

McMaster has some as well, but a quick look showed only very expensive
high pressure SS fittings there.

4822T45
Extreme-Pressure SS Threaded Fitting M20 X 1.5 Male X 1/2" NPT Female
Adapter, 5000 PSI
In stock at $46.63 Each

--
Ned Simmons

I found the M20-1.5 drain plug in an auto parts store. They were kind
enough to let me try it on the tank. It was too small. They also had
a drain plug in M22-1.5. I now know that is the correct diameter and
thread pitch. However, the shape and mass of that drain plug were
unsuitable. At $12 a pop (and I need 3 of 'em) it turned out to be
too expensive, also.

After going back to google again and again I think I have correctly
surmised that PRESSURE WASHER HOSE FITTINGS will work. They're the
right diameter but I'm not sure they're the right thread although from
the picture it looks about right. So I bought 3 fittings for $3.00
each. Not only are they pressure rated they're also made of brass.
That strikes me as a good thing so they won't get frozen by rust
developing between the fitting and the tank.

The fittings I ordered are both male, 22mm at one end and 3/8" at the
other. I am hopeful, but probably delusional, that the smaller thread
will fit a standard air hose quick disconnect.

I have learned that 22mm bolts, when available, are ridiculously
expensive. So if these fittings don't work I will probably launch the
tank into near earth orbit.

Thanks,

V

"Vernon Tuck" wrote in message
...
On Jun 12, 11:46 pm, Ned Simmons wrote:
On Sat, 12 Jun 2010 18:13:36 -0700 (PDT), Vernon Tuck

wrote:

I'm not a machinist and I don't have any measuring tools. So I'm not
sure about the diameter of these holes but I'm pretty sure they're
M20x1.5 or M21x1.5. I have found European sources for blind plugs in
these dimensions but have not yet found a source in the USA.

These seem to be intended for use as conduit fittings, but the threads
are
right:http://www.sealconusa.com/strainreli...m/adapters.htm

McMaster has some as well, but a quick look showed only very expensive
high pressure SS fittings there.

4822T45
Extreme-Pressure SS Threaded Fitting M20 X 1.5 Male X 1/2" NPT Female
Adapter, 5000 PSI
In stock at $46.63 Each

--
Ned Simmons

I found the M20-1.5 drain plug in an auto parts store. They were kind
enough to let me try it on the tank. It was too small. They also had
a drain plug in M22-1.5. I now know that is the correct diameter and
thread pitch. However, the shape and mass of that drain plug were
unsuitable. At $12 a pop (and I need 3 of 'em) it turned out to be
too expensive, also.

After going back to google again and again I think I have correctly
surmised that PRESSURE WASHER HOSE FITTINGS will work. They're the
right diameter but I'm not sure they're the right thread although from
the picture it looks about right. So I bought 3 fittings for $3.00
each. Not only are they pressure rated they're also made of brass.
That strikes me as a good thing so they won't get frozen by rust
developing between the fitting and the tank.

The fittings I ordered are both male, 22mm at one end and 3/8" at the
other. I am hopeful, but probably delusional, that the smaller thread
will fit a standard air hose quick disconnect.

I have learned that 22mm bolts, when available, are ridiculously
expensive. So if these fittings don't work I will probably launch the
tank into near earth orbit.

Thanks,

V
You might like to try 1/2 inch BSP (British Standard Pipe) fittings which
are 14 TPI 55 degree thread and 21.3mm or 27/32 in OD. BSP is used in many
countries including Germany, but USA is not one of them. If this is the
size, you may be able to find a suitable BSP-NPT adapter or else retap the
holes to 1/2in NTP which is 14TPI 60 degree thread and a slightly larger OD
IIRC.
--
Regards,

Chas.

(To email me, replace "xxx" with letters tango papa golf.)

On Jun 14, 5:37*am, "Chas" wrote:
"Vernon Tuck" wrote in message

...
On Jun 12, 11:46 pm, Ned Simmons wrote:





On Sat, 12 Jun 2010 18:13:36 -0700 (PDT), Vernon Tuck

wrote:

I'm not a machinist and I don't have any measuring tools. So I'm not
sure about the diameter of these holes but I'm pretty sure they're
M20x1.5 or M21x1.5. I have found European sources for blind plugs in
these dimensions but have not yet found a source in the USA.

These seem to be intended for use as conduit fittings, but the threads
are
right:http://www.sealconusa.com/strainreli..._npt.htmlhttp:...

McMaster has some as well, but a quick look showed only very expensive
high pressure SS fittings there.

4822T45
Extreme-Pressure SS Threaded Fitting M20 X 1.5 Male X 1/2" NPT Female
Adapter, 5000 PSI
In stock at $46.63 Each

--
Ned Simmons

I found the M20-1.5 drain plug in an auto parts store. *They were kind
enough to let me try it on the tank. *It was too small. *They also had
a drain plug in M22-1.5. *I now know that is the correct diameter and
thread pitch. *However, the shape and mass of that drain plug were
unsuitable. *At $12 a pop (and I need 3 of 'em) it turned out to be
too expensive, also.

After going back to google again and again I think I have correctly
surmised that PRESSURE WASHER HOSE FITTINGS will work. *They're the
right diameter but I'm not sure they're the right thread although from
the picture it looks about right. *So I bought 3 fittings for $3.00
each. *Not only are they pressure rated they're also made of brass.
That strikes me as a good thing so they won't get frozen by rust
developing between the fitting and the tank.

The fittings I ordered are both male, 22mm at one end and 3/8" at the
other. *I am hopeful, but probably delusional, that the smaller thread
will fit a standard air hose quick disconnect.

I have learned that 22mm bolts, when available, are ridiculously
expensive. *So if these fittings don't work I will probably launch the
tank into near earth orbit.

Thanks,

V
You might like to try 1/2 inch BSP (British Standard Pipe) fittings which
are 14 TPI 55 degree thread and 21.3mm or 27/32 in OD. *BSP is used in many
countries including Germany, but USA is not one of them. If this is the
size, you may be able to find a suitable BSP-NPT adapter or else retap the
holes to 1/2in NTP which is 14TPI 60 degree thread and a slightly larger OD
IIRC.
--
Regards,

Chas.

(To email me, replace "xxx" with letters tango papa golf.)

I am delighted to report that I found the perfect fittings at northern
tool. These are brass fittings apparently intended to be threaded
into the ends of pressure washer hoses. Both ends are male, one
being M22-1.5 and the other, 3/8 NPT. Thus, I am able to screw them
into the tank and thread a standard female quick disconnect air hose
fitting onto the smaller end. I will be able to charge the tank and
purge/drain it by simply plugging hoses into it.

Isn't google great?

V