The tutorial is how to take a sheet of HDPE, UMHWHDPE or other suitable material and make a small piston with a floating o ring seal using a drill press. I was asked to produce a small piston, so I took the opportunity to turn it into a photo tutorial.
The piston on the right is destined to become someone's piston hybrid. I can't wait for the photos and a video of the finished product.
The construction of the middle piston was photographed for this tutorial.
To limit the number of photos per post this will be a double post.
Tutorial - Making a small o ringed piston on a drill press
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Technician1002
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- When the piston fits, stop. If the arbor was centered better, the flat side would be smaller or gone. This is the end of part 1.
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- After several passes the piston is starting to take shape. As it becomes smaller, keep track of the diameter.
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- A suitable cutting tool is clamped to the drill press table. I used a wood chisel. The rotating block is lowered past the cutting tool taking off a small amount in each pass.
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- The arbor is nothing more than a bolt with the head cut off. This is screwed into the hole.
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- The block is tipped on edge and drilled for an arbor so it can be attached to the drill press.
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- A suitable size piece of plastic is cut using your favorite saw. For a long piston the material can be turned edgewise. This tutorial will show that procedure.
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- These pistons are made using a sheet of 1 inch UMWHDPE. The piston on the left is 2 inches tall and 1 inch in diameter. The piston in this tutorial is 1.37 inches tall and 1.06 inches in diameter. It has a flat side from the original surface.
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- Updated photo with the finished pistons. From the left is a long piston with no seals. A traditional barrel or chamber sealer with face gasket and o ring, and a QDV style for a Marshmallow Cannon type piston with 2 rings.
Last edited by Technician1002 on Tue Nov 30, 2010 3:47 am, edited 10 times in total.
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Technician1002
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To cut the groove, a sideways cut needs done. A drill press vise works great to hold a small cutting tool that can be used to cut into the side of the piston.
The groove in a piston for an o ring is called the gland. For a floating o ring the gland is deep enough that the o ring does not receive any cross sectional squeeze. The gland is wide enough the ring has some wiggle room, so it is free to float. This prevents it from becoming stuck down in the gland.
The ring is slightly larger than the ID of the cylinder so it gets some peripheral squeeze to fit. The air pressure holds the o ring against the side of the gland and pressure under the ring tightens the seal with pressure against the cylinder wall. These work great as a dynamic moving seal on a piston.
Edit: Added photos of the finished pistons.
The groove in a piston for an o ring is called the gland. For a floating o ring the gland is deep enough that the o ring does not receive any cross sectional squeeze. The gland is wide enough the ring has some wiggle room, so it is free to float. This prevents it from becoming stuck down in the gland.
The ring is slightly larger than the ID of the cylinder so it gets some peripheral squeeze to fit. The air pressure holds the o ring against the side of the gland and pressure under the ring tightens the seal with pressure against the cylinder wall. These work great as a dynamic moving seal on a piston.
Edit: Added photos of the finished pistons.
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- Here is a close up photo of the business end of the drill bit used to cut the gland. It is cut like a mini chisel.
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- The last steps are to trim the ends of the piston. The area by the bolt is trimmed so a washer can be used for the piston face seal. The arbor bolt hole can be used to hold the washer.
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- Cut the gland so the o ring can drop into the grove without force and just deep enough so the ring can fit without any protrusion. This ensures the ring will not get any cross sectional squeeze.
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- Our target o ring is selected to fit inside our cylinder with just a slight squeeze of the ring. It is the right size if it will hold it's position in the cylinder without falling out.
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- The tool is secured in a drill press vise and the vise is moved into the side of the piston. The groove is first cut too narrow and too shallow. It is easier to make it larger later than to make it smaller.
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- To cut the gland a small cutting tool is needed. I simply made one using an old drill bit. I cut an edge with a small grinding wheel. Look at the left end of the drill bit.
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- A proper size seal is cut from a sheet of rubber using a hole saw. It is cut slightly large and then the edges are trimmed on the drill press to size just like the way the piston is made.
Last edited by Technician1002 on Fri Oct 29, 2010 6:44 pm, edited 1 time in total.
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jakethebeast
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good tutorial, now peolple has less excuses when they say they cant make a piston hybrid 
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LovableAirGuns
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couldn't you use a flat head screw driver in stead of making a mini chisel?
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Lockednloaded
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great tutorial btw, but just a little side note:
I'm grateful for the piston you sent me, but unfortunately, I don't think this stuff is exactly "5x hybrid material" upon the first shot at 5x, the material behind the o-ring was mangled beyond all salvageability. The bumper was a coiled 1/4" air hose then a 1/4" thick rubber washer. thanks for the help, but I think I'll have to stick to bolt+washer pistons
I'm grateful for the piston you sent me, but unfortunately, I don't think this stuff is exactly "5x hybrid material" upon the first shot at 5x, the material behind the o-ring was mangled beyond all salvageability. The bumper was a coiled 1/4" air hose then a 1/4" thick rubber washer. thanks for the help, but I think I'll have to stick to bolt+washer pistons
I love lamp
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Technician1002
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A mini screwdriver could be used, but I use my mini screwdrivers as um screwdrivers. A dull drill bit was a better choice for me to grind to a sharp cutting edge.
Thanks for the feedback on the piston at 5X. I was not sure on how it would hold up to that abuse. Feel free to post damage photos. Knowing what works and what doesn't is what this thread is all about.
Thanks for the feedback on the piston at 5X. I was not sure on how it would hold up to that abuse. Feel free to post damage photos. Knowing what works and what doesn't is what this thread is all about.
Tech,
You'll get to your piston shape faster, and with less tearout, if you cut the corners off the square before you start to spin it on the drill press.
As so:
You'll get to your piston shape faster, and with less tearout, if you cut the corners off the square before you start to spin it on the drill press.
As so:
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- cut corners.jpg (17.9 KiB) Viewed 24221 times
If you can't fix it, you don't own it.
Hey tech, on a external website you discussed in a build log how to merge two or more pieces of plastic together, for construction of a piston.
Since i can't find the link again can i ask what kind of plastic this was?
Also do you have any idea if UHMWPE or Nylon is able to be melted and molded in one piece (in your own home).
Since i can't find the link again can i ask what kind of plastic this was?
Also do you have any idea if UHMWPE or Nylon is able to be melted and molded in one piece (in your own home).
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Crna Legija
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i know you can with HDPE just heat up both sides till they get a clear layer on top then press them together.
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Technician1002
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It was HDPE. The other stuff was tried and failed. The photo you are looking for is on this page;
https://inteltrailblazerschallenge.wiki ... +brag+zone
And the photo of them being squished.
and the finished piston.
https://inteltrailblazerschallenge.wiki ... +brag+zone
And the photo of them being squished.
and the finished piston.
Tech, if you are using UHMW, you don't need a rubber sealing face. As long as both the piston face and corresponding face are square and free of nicks or cuts, the UHMW will seal very well. I did this for my hybrid piston cannon and it never leaked.
Of course, I had access to a lathe, so I was able to machine clean faces. That being said, it would be worth a shot, as if there is no rubber sealing face, it can never be blown out the barrel!
Of course, I had access to a lathe, so I was able to machine clean faces. That being said, it would be worth a shot, as if there is no rubber sealing face, it can never be blown out the barrel!
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