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Author: Gus Mahon ~ Gus Mahon Homepage)

Posted By: acannell and camarobutcher

Alright, so here's my writeup on making a Grainger valve with part numbers and pictures.

A-86 1/8 ID Barb x ¼ FIP
A-85 1/8 ID Barb x ¼ MIP
A-732 ¼ FIP Both Ends

True Value Hardware
376775 ¼ x ¼ 90 degree mender (barb is actually 1/8 with ¼ overall width) $2.79

HB0176 #76 HSS Wire Gauge Bit $1.55

Control Devices Inc.
5Z763 ¼ NPT Male VR Series Vacuum and Pressure Relief Valve, a.k.a. Grainger Valve

48935K25 ¼ NPT Male Brass Adjustable Vacuum/Pressure Relief Valve, a.k.a. Grainger Valve $7.70
44555K142 .17 x .17 90 Degree Barb $1.77
5346K51 3/16 ID Barb x ¼ FIP $14.58 per 10 pcs.
5346K82 1/8 ID Barb x ¼ FIP $14.83 per 10 pcs.

To start off, I’ll tell you where you can get all the parts. I also included prices when I had them. Watts parts are available at Fleet Farm, Home Depot, and Menards. I could only find the ¼ x ¼ 90 degree mender at Neu’s, and that is their part #, not sure of the manufacturer. I checked Fleet Farm, Home Depot, Menards, True Value, and Neu’s and only Neu’s had it. Neu’s also has the wire bits that you will need to drill the .02” hole which is a #76 bit. True Value only had bits that went down to #60, which is not far enough. Control Devices is the brand of Grainger that I bought and I got it from a member on this board. I don’t believe McMaster-Carr deals with customers directly, but with businesses who have accounts, so you will have try to find a local business that can order from them. The last two parts from McMaster-Carr are only sold in packs of 10, but if you order from a business, I bet you could get just 1 or 2. I found those part numbers on Gus Mahon’s page and verified that they were all correct and that none of them had changed. The Watts part numbers I got from an online catalog on their website. For some reason when I typed in the part numbers in the search box it wouldn’t find the products. Now if for some reason you can't find the parts with the part numbers I listed above, just look for a part with a description like the ones I gave you. FIP is female threaded and MIP is male threaded. The threaded fittings are all going to be for a 1/4" thread, even though it is actually larger if you were to measure it.

So this is the Grainger valve. You can get it from McMaster-Carr #48935K25 or Control Devices Inc. #5Z763, or from someone on this board.

So now, unscrew the valve and make sure the ball is seated in the threaded end of the valve, if not switch it so it looks like this. Next, screw on the threaded barb Watts #A-86 or McMaster-Carr #5346K82 for the 1/8 barb or McMaster-Carr #5346K51 for the 3/16 barb. Gus Mahon used the 3/16 so the 1/8 vacuum wouldn't blow off at higher boost levels, but I used the 1/8 barb up to 14 psi without any issues. I looked everywhere and couldn't find either of these female threaded fittings like in the picture. So what I did, instead of using a female barbed fitting, I used a male barbed fitting with a female pipe coupler. You will see what I mean in the pictures below. The male barb is Watts #A-85 and Watts #A-732 for the female coupler.

Now you need the tiny .02 drill bit, also known as a #76 HSS Wire Gauge Bit. I got it from Neu's part #HB0176. Here is a photo for size comparison.

Now you need to take the 90 degree fitting from McMaster-Carr #44555K142 or you can get it from True Value #376775 and drill the hole in it. So take the tiny ass drill bit and put it in a cordless drill. Set it up in the teeth of the chuck so that it only drills halfway through the side of the 90 degree fitting. Try not to put too much pressure on the bit when drilling or it will snap. I suggest buying 2 or 3 bits from the start. After you drill the hole, take a hammer and pound the fitting into the top of the Grainger valve. Try to make sure it goes in straight. I unscrewed the top part of the Grainger valve from the rest of the assembly and set it on a block of wood when I pounded the fitting in. When you're done it should look like this.

Screw the top of the Grainger back into the rest of the assembly and the finished product should look like this.

Here is what mine looks like. It looks a little different but works the same. The 90 degree fitting wouldn't go all the way in but it doesn't leak boost. I suggest buying two of the 90 degree fittings too because they are kind of brittle and might break when you pound it in to the top adjusting part of the valve. You can even see the tiny ass hole I drilled.

That's basically it. Screw the valve together to increase boost and apart to decrease boost. The valve should adjust boost from 0-20 psi. If you can get all the parts from McMaster-Carr, you should be able to make the valve for around $13-$14. I got the smaller pictures from Gus Mahon's page.

acannell said:
if you have a dremel its much easier since it spins much faster than a cordless drill and you can use special circuit board drill bits that have a big shank.

mcmaster sells .020" drill bits with a 1/8" shank that are perfect for dremels.

p/n 2841A81 , $4.92 each

cuts through brass like butter at 30,000 rpm :)

~ Rest In Peace Gus Mahon ~
And thank you for sharing your knowledge for those who came to this sport after your tragic accident. Forever Missed, Never Forgotten.
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