Air manifold casting project

I'm trying to get the air compressor rigged up in my shop; been working at it for a year or two. It's wired up, runs, and it has a place to live in the shop. The plumbing part has been dogging me. Couldn't find a decent air manifold anywhere I looked but, gee, how hard can it be to make one of those?

I'm stymied to make a 5/8" x 5" long cylinder core. I wound up using a 1/2" copper tube hoping it would dissolve into the aluminum when casting, at least partially.

The first try at casting came close but there were large cavities surrounding the tube. Then I got some petro bond and tried again. Boy, it sure looks good to me! Compared to the first try.
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Drilled and tapped a few pipe threads, added the hardware and I'm done.
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Except it leaks. See that black mark? Right there in the corner is a pinhole leak. Should'a gated it better.
Do you think JB Weld will fix it?
When I try again, I won't use copper tube because it causes machining problems. It didn't dissolve one bit.

 

Maybe if you drill a hole at the pinhole, and then fill it with jbweld.
I am not sure if just using jbweld on the surface would hold up.

 

I'd weld that pin hole.
It's under high pressure, correct?

 

I'm pretty sure the leak is a result of porosity in the Al. If you look close at the pictures you can see a path from the sprue to the pin-hole. The copper tube had a patina, to say the least, so it might have been gassing right where the last of aluminum was filling the mold. Gating this part differently will likely solve this problem. I just threw the pattern in the sand and almost forgot to put a gate in. I was pretty excited to just be able to try the new sand.

 

It's been about four hours and the pressure has drop from 120 to 30 psi. This is tolerable for the short term but, unacceptable as a permanent solution.

 

What kind of pressure and volume are you looking for? Would something like this work for you?

I use something like this for CO2 distribution with my kegerator system. You can find them on eBay relatively affordably.

 

That looks pretty much like I was wanting. Seems simple enough to make my own, right?

 

Tried dipping the manifold into shellac. Still leaks. I'm gearing up to make some 5/8" core dowels. It's funny how all the information regarding making core dowels assumes you have a split core box. I want a dowel longer than a drill can make a hole, approx. 6 inches. I may need to make a plane that can cut desired half round grooves. Is that how the old tymers did it?

 

search for "stanley core box plane"


Beautiful complete one here on Ebay... Beware of sticker shock
https://www.ebay.com/itm/Antique-18...351902?hash=item48a2e1cb1e:g:L7oAAOSwRgJXjsW-


V/r HT1

 

The ID of 1/2" pvc is 0.60 the difference of 0.025. If it doesn't have to be an exact 5/8 you could tamp a pipe full then use a Dremel to split it open.

 

And if you use a piece of PVC for a core box, you can slit it down one side only, ram the core, and then pry the slit open slightly at the center of the slit to release the core (saves having to use a 2-piece core box).

 

I see now how the old tymers made core boxes for core dowels. Sticker shock? Oh boy are they expensive.

 

If you need to drill a long 5/8" hole, here are a few options I would consider:

A bell hanger bit would cut a 10"+ hole
https://www.amazon.com/MAGBIT-786-1...96&sr=8-4&keywords=bell+hanger+drill+bit+5/8"

A reasonably competant machinist could braze a stem onto a 5/8" Silver and Deming bit. https://www.amazon.com/Quality-Spee...8&qid=1509027378&sr=1-5&keywords=5/8"+s+d+bit

Hand-driven woodworking auger bits cut 8 to 10 inches. https://www.amazon.com/Steelex-Plus...1&sr=1-15&keywords=5/8"+auger+bit+woodworking

Power auger bits would do the job: https://www.amazon.com/Shop-Tek-806...id=1509027440&sr=1-14&keywords=5/8"+auger+bit

 

Thanks, Melterskelter it helps to know the names of these tools such as the bell hanger bit. I've been passing on the idea of using a long bit because I don't feel confident drilling a long, straight hole.

 

I think any of those bits would cut a "straight enough" hole. Use a drill press and the hanger bit. That would probably be the easiest. The resulting hole would be pretty straight even drilled into end grain of wood. I doubt you could see any curvature over its length. If you are real fussy, cut a 7 inch hole and lop of the first inch since it is in that first inch that most of the runout would occur.

 

Maybe I'm missing something. My drill press has a 2-1/2in stroke. No matter how long the drill bit, I can drive it only 2.5 inches. I've tried flipping the work piece end for end, which should give me a 5" long hole but, there's always a misalignment and a step where the two holes meet. It's not the curvature over the length that worries me, it's the skew (though curvature will not be good either).
This particular problem of drilling a hole in the end grain has been haunting me for several years. I'm planning to make something for the wood lathe to solve this problem but I'm a good ways off from completing that project. There will be pictures.

I bit the bullet and purchased a set of core box router bits.