In this instructable I'll show you how to make a vacuum bag stem (also called a vacuum breach valve/unit). These are important in vacuum bagging because taping the hose on the seam of the bag is a recipe for leaks and disaster.

This adds on to the excellent guide on vacuum bagging basics
It also goes well with the bicycle-turned-vacuum pump guide if you want to do some hand powered vacuum bagging, or the great tire-inflator-turned-vacuum-pump guide.

Step 1: Gather your parts

You'll need: 
4 3/8" steel washers
2 3/8" ID, 7/8" OD neoprene washers
1 1/8" F nut (dunno what they're called)
1 1/8" M to M threaded tube connector (the shorter the better)
1 1/8" F NPT to hose connector
Vacuum bagging plastic sheet/film
<p>I just ordered a valve on amazon with a hand pump. It is usually used to keep whine fresh, but i got 4 &quot;valves&quot; and a small pump for around 10$. They are nearly identical to the ones used by Roarockit.</p>
<p>solder (or weld) the washers together to make handling it all easier</p>
<p>great instructable, purpose driven, simple enough for anyone to do. </p><p>If I may ask, would this not be a port instead of a valve? And am I to assume that this is for a short term project use - such as vacuum forming, or impregnating a fluid in a material such as with carbon fiber? </p><p>Would it be possible to create a valve by cutting an extra piece of rubber that opens during the draw out, but closes against the other washer to generate a seal; such as one would find in a blacksmith's bellow's?</p>
<p>You're absolutely right, it is a port instead of a valve. It should be called a vacuum connector or a vacuum port instead. </p><p>And you're right! It is for short-term project use like vacuum forming or vacuum bagging carbon fiber or fiberglass. </p><p>I haven't given the rubber seal much thought. The trick is that the flap would need to be on the outside, not the inside to let air go the right way. </p>
??? <br>how air isn't sucked in through the valve ? <br>Does it has a flap inside or something ? <br>The hose connector is hollow, no ?&hellip; <br> <br>Don't get the idea at all !&hellip; <br> <br>sorry&hellip;
You're right, it doesn't have any sort of one-way valve on it. The trick would be to leave the hose on for the duration of time that you need a vacuum.
Ah ! OK !&hellip; <br> <br>Thans for posting.
What if you place another washer outside and clamp the plastic in middle of them? it should stop any leak... <br> <br> //////////// &lt;---- neoprene washer <br> ----------------- &lt;- plastic <br> //////////// &lt;---- neoprene washer <br> <br> <br>It should help for a better tighting...
Hmm that is a good idea, and what I think I'm doing, if I read your comment correctly. The plastic is held on both sides by neoprene washers, and outside of both of those are two steel washers which distribute the tightening pressure from the three brass fittings.
mmm this cant work in the way you have described or shown. How does the air not flood back in when you remove the hose? there needs to be some kind of oneway valve. can you show this working?
You're absolutely right! I was using drcrash's <a href="http://www.instructables.com/id/make-a-manual-vacuum-pump-for-under-%2420-by-convert/" rel="nofollow">manual vacuum pump</a>&nbsp;which has on it a one way ball valve.&nbsp;<br> Though that doesn't fix the problem of air flooding back in when I remove the hose. I just leave the hose on and maintaining the vacuum for as long as I need it and then remove the hose.&nbsp;

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