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I've got a consumer-grade, 18 gauge pneumatic brad nailer that just blew a gasket. It's a discontinued model with no repair parts available.

The gasket I'm referring to, labelled as part 9 on the left side of the diagram below, goes between the head cap (part 8) and the housing for the piston (part 30).

enter image description here

For scale, it's about 2.25" x 2.5", a little over 1 mm thick, and about 1/8" wide (the thickness of the housing wall). It feels like it might be polypropylene. The gasket tore apart in use, allowing air to leak out too fast for the gun to be useful.

A replacement gasket needs to have a few characteristics:

  • The thickness needs to be very close to the original to provide proper clearances for the components inside.
  • The housing wall is only 1/8" thick, the shape is skinny and complex, and there's not much surface area. The gasket shape needs to be precise to accurately mate with the whole contact surface. The material must be soft enough to compress and seal surface irregularities, but rigid enough to not flex out of the gap under pressure.
  • It must handle 100 psi without ballooning out or tearing.

Is there a common sheet or caulk-like gasket material that would be suitable for making a replacement?

As supplementary insight, if any reader has attempted a similar repair, based on that experience, is a gasket of this type, tolerances, and complexity even practical to reproduce at home?

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  • Have you tried that great big giant online auction site
    – Alaska Man
    Sep 1, 2020 at 0:12
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    Many auto stores have sheets of different gasket material and different types of Permatex sealants. You might want to check there.
    – JACK
    Sep 1, 2020 at 0:28
  • @JACK, yeah, auto stores are a good source for a range of materials. The problem is knowing which material would be suitable for this situation. It's a little different from a typical gasket job, like on an engine. Unfortunately, the products don't list whether they will work for these requirements. It may be why the gun manufacturer used molded plastic rather than a more typical gasket material.
    – fixer1234
    Sep 1, 2020 at 0:43
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    I am suggesting to just search the model number on the site and see what pops up. You never know, there are parts for all kinds of things or units sold for parts. You could search for parts on the internet as a whole, there may be some old parts place that has New Old stock gasket.
    – Alaska Man
    Sep 1, 2020 at 0:52
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    i've used hot glue to fix something like this where parts were not available.
    – dandavis
    Sep 1, 2020 at 16:47

4 Answers 4

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I have found sheets of neoprene rubber, silicon rubber and the high temp stuff that looks like card board on line. On my nail gun senco they wanted ~22 for the replacement gasket plus shipping , I tried silicon sheet two soft blew out, neoprene rubber sheet it has held up I ordered a bunch of thickness but ended up using 1/16” exacto knives are really handy for cutting the neoprene. I should note I did try the high temp paper first as I had some for making gaskets for my compressor. Those blew out before it got to pressure. I think the neoprene 12” square was only 3 or 4$ I would give that a try.

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I ended up using Elmer's glue, but not in the way that likely jumps to mind.

I had tried cutting the gasket from a sheet of HDPE from beverage containers (Solar Mike also suggested that). The cutting job was tougher than I imagine neoprene or EPDM would be. Tried several times. The HDPE didn't have a smooth surface and didn't conform under pressure enough to seal.

Before investing more time trying to cut out another gasket, I tried a different approach. I patched up the old gasket and used it to make a silicone mold (silicone caulk plus a little starch to speed curing). Now I can make as many gaskets as I need to test materials and replace homemade ones that fail.

I tried hot melt glue first. Something that thin is too rubbery and flexible.

Long story short, I cast PVA glue (Elmer's). The gasket is just over 1 mm thick. I filled the mold with glue. When it dried, it was a small fraction of the thickness. I just repeated the process, building a lot of layers. The glue has enough surface tension that you can overfill the mold without the glue running off. Eventually (I forget how many layers, but a bunch), I had a PVA gasket.

It isn't as rigid as the original (that might have been ABS), but fully cured PVA glue is a slightly soft plastic that's a bit flexible. It conforms to the surface under pressure and is stiff enough to not balloon out.

The one I molded is still working. I have no idea how long it will hold up. But when it fails, I can make another one with minimal effort using the mold.

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Yes, a sharp knife, cutting board, steady hand, good marking out, patience and of course suitable material.

Made gaskets for many things using paper, card, plastic etc

One source of plastic useful in the past was a milk container, but temperature is a consideration.

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  • So it's reasonable to cut a matching gasket of this style by hand with some material, and if it's a suitable material, it should work; sorta passes the sanity check that it could be made at home. Any thoughts on the meat of the question, what would be a suitable material? Lots of materials can be used in some circumstances. Paper or cardboard wouldn't hold up. I had thought about an HDPE jug but it isn't rigid, thick, or smooth enough.
    – fixer1234
    Sep 1, 2020 at 7:22
  • I have a dozen different sheets of gasket materials some like cardboard or whatever and some out of neoprene different thicknesses a sharp knife and patience you should be able to make it, all purchased online not very expensive. +
    – Ed Beal
    Sep 1, 2020 at 7:35
  • @EdBeal, most common gasket materials won't work for this. It's a very thin rim of material with no lateral support, that fails if it moves, and it's under 100 psi.
    – fixer1234
    Sep 1, 2020 at 8:13
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    I have made the gasket for my senco framing nailer out of neoprene. It is almost the exact same part. It doesn’t get hot so the neoprene in my case works just fine. If it got hot I would the high temp cardboard like stuff. The neoprene although hard is pliable and when squeezed it has held up for years. I run my gun at up to 120 on old wood.
    – Ed Beal
    Sep 1, 2020 at 8:23
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    @EdBeal, that sounds like an answer to the question. Why don't you post it.
    – fixer1234
    Sep 1, 2020 at 8:42
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Just replaced a similar part with a gasket made from 3mm EPDM “flat mat” from Bunnings. You can get a 450mm square for about $12. Get a white dress makers pencil or similar to mark out from the old gasket. Cut the screw holes with a hole pinch by removing the base and line up the hole from underneath. Cut out with large scissors and an exacto knife. Because this stuff is compressible, you can adjust the final thickness with the bolt tension. Takes 5 min to make.

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