Homemade Fire Piston




Introduction: Homemade Fire Piston

I am an engineer and I like to build things. I am well versed in drafting and solid modeling and ...

I live in lovely Ol' Seattle. It likes to rain here tons, specially during winter, fall, and spring. When it rains, I like to dink around in the machine shop at my place of employment. I am also an avid hiker and camper, so this project fits right in with my interest. I designed and constructed a fire piston on the lathe at work.

A fire piston works like a diesel engine, take air, compress it fast, and Boom. There is no boom, just embers if you use the right fuel.

Step 1: Prep and Materials

This is not my first attempt to make a fire piston, my second time actually. The first time I made this I based it off of Makes Clickspring fire piston. It would work but it would not always seal; too many parts. So I designed my own using solidworks to model it up. You can view the schematics in the attached pdf. One of the tolerances is incorrect; .495 +.003 -.005 (not .050). Make any design changes you want, but the diameter of the piston and cylinder bore need to have a tight tolerance or the fire piston will not work.

Items you'll need are the following:

  1. 1"od x 5" long aluminum rod
  2. 1"od x 5" long bronze rod (I used a scrap piece of metal from a casting at work)
  3. 1/2" od x 3/8" id o-ring (buy some spares just in case)
  4. Lathe and turning bits
  5. Center, 1/4", 3/8" 29/64", and 1/2" drills
  6. Cutting Fluid
  7. A drop of oil or lube
  8. A fine file

When working with a lathe, make sure you have long hair tied back and necklaces taken off, you don't want to be sucked into a lathe. If your using the lathe properly you wont need any ear protection but you will need safety glasses to protect your eyes from flying metal missile chips. Refer to the provided pdfs for the dimensions that I used.

Step 2: Cylinder: Face It and Drill It

I suggest that you make the cylinder first so you can test the piston fit without taking the piston off the lathe when you make it. First chuck up the aluminum bar, give the exposed end a nice finish cut. After you establish the finished face drill into it with the center drill first, then the 1/4, then the 3/8, then the 29/64, and finally the 1/2. Once the hole is established, check the finish on it. If it is smooth move on, if it is rough, I would suggest using a 1/2" reamer to clean it up. Mine was nice and smooth. Throw a center stock on that new hole and move on.

Step 3: Cylinder: Turn It Down to Size

Take some layout ink and mark the length to cut on the rod. Start cutting away. Each lathe is different on what it is capable of, mine is old so any cutting pass greater than .040" will stall it. Take rough cuts up until you reach an od of .890. The last pass will be a .015 finish cut and I would suggest the use of a powerfeed feature if you have one, will give you a really nice surface finish. I used a feed rate of .0015" per revolution for the finished cut. The cylinder should be nearly done now.

If you want to add some decorative grooves, now is the time to add them before we part this puppy off. I put six grooves in at no particular dimension, just 3 on either end. Looks nice.

Part it off, flip it and finish turn that puppy to its finished length.

Step 4: Piston: Facing and Turing

Chuck up the bronze bar, put a nice finished face on her like the cylinder. Use the center drill and drill to a depth at roughly 3/16-1/4. Put the center stock onto it and begin the turning process. Turn it all down to finished diameter of .875". Use the layout paint to establish the length of the smaller od. Cut away until you get to about .015" above the finished diameter. Finish turn the piston similar to how the cylinder was turned.

The next step is the most crucial, using a parting tool or groove cutter, cut the groove for the o-ring. If you have little experience cutting grooves, I suggest taking small cuts and checking the o-ring fit with the cylinder as you get closer to the finish dimension. It should be a nice fit such that when you put the cylinder on the piston, you should feel back pressure. The cylinder should be pushed back out by the trapped pressure when released. If you are at the finished dimension and cant get a seal, try changing out the o-ring. If that does not work, then either the piston or cylinder will need to be remade.

If you get a good seal, part off the piston, flip it and face it to the finished length.

Step 5: Extra Steps

I decided to add some holes to my design to attach some paracord to. I drilled a 7/32 hole in the piston and a 3/16 in the cylinder. Clean off the layout ink with a light sanding or filing.

Step 6: Finished Product

Put the o-ring on the piston and apply a couple drops of oil or lube. Do some compressions to lube up the cylinder and tie some paracord to her. This project took me a little under 4 hours to make start to finish; I did it in one sitting.

To use this guy, you will need to use it in conjunction with some char cloth. Put a little piece of char cloth in the opening of the piston, load it, and compress it really fast and hard. Repeat until you have embers burning. Does not work with paper, only char cloth. I will post a video and update this guy when I get some char cloth. Happy making, I hope you guys add this guy to your survival kits, I know I will.

UPDATED 2.17.2016 - Added a video of some embers burning and updated the pdf drawing.



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    25 Discussions

    Try lint from the clothes dryer instead of char cloth

    I've always been interested in aluminum lathing. This is very fascinating stuff. Nicely done.

    2 replies

    thanks. I always enjoyed working on the lathe versus a mill.

    I forgot to tell you that you did a great job on your fire piston, I'm sorry I didn't mention it in my response earlier.

    That is a lot of work to get something to start a fire. When I'm backpack camping on the trails or at a campground, a simple 9V battery, steelwool with magnesium shavings works sooooo easy. The weight of the battery isn't much, neither is the steelwool.

    2 replies

    Sure steel wool and a 9 volt battery will work but for those that don't know, don't carry them in the same pocket. A match will work even easier, and a magnesium and a cerium rod and steel is another way, and I like my flint and steel striker but I also like the fire piston. Sure there's an easier way to start a fire, but why not learn every way just for your own knowledge or use it as a teaching tool for children and adults. If you have access to a lathe or a drill press learn how to make them and share your knowledge with others. A fire piston is a very simple engine that works just like a diesel engine, except with a different fuel source. I've worked with the scouting program for years and most all are intrigued to learn and see the different types of fire starters out there, you can really see the wheels turning when they get a turn at a lathe or mill or a simple electric drill.

    A 9v battery is good -until it goes dead. On the other hand, if you are stranded out in the wilderness in a vehicle, you can start a fire with the car battery and any light bulb from the vehicle or even a piece of steel connected in series with the battery using any conductor of sufficient length. You have to use caution though, shorted batteries (even 9v)can overheat rapidly when used this way and can explode.

    Char cloth is cotton cloth that is burned halfway to ash and it acts like charcoal but made of cotton so it lights easyly.

    Ah ok, I see something posted below on how to make it. I still don't know what it is though.

    I'm not a machinist, but your instructible caught my attention... Cool.

    Is it my imagination, or is the cylinder 1/5" and the piston 0.875" ?

    I make my own char cloth, if I ever get my act together I'll try to upload how. So I gather that this has something to do with starting a fire? Never seen something like this, I'm a steel and flint guy my self (when I want/need to well mostly want) It this supposed to be easier than flint and steel?

    Why wouldn't you use a steel dowel to the length you need? The tolerances on those are less than 0.0002" which should be close enough for anyone, just ream and hone the hole, you could do this with nothing but a drill press and vise and leave the bottom of the hole with a small taper before the flat bottom and go from there? If you get it right there is no real need for an O-ring, the seal will be great with just a thin film of oil from a drop on your fingers!

    1 reply

    that's that's a good idea. I'll have to try it when I can scrounge up some more scrap metal to play with.

    I like this project! I'm a retired Tool & Die Machinist, and now that I have time to make my own projects in my little home machine shop, I'm always looking for worthwhile projects. This is one!

    I didn't notice if you left any clearance in the bottom of the cylinder for the piston. Is there any or does the piston bottom out in the cylinder?


    1 reply

    There is about a 20 thousands clearance at the bottom. The drawing has the nominal dimension the same for both with complimenting tolerances but it is wise to either increase the depth of the bore or decrease the length of the piston.

    thank you! i have been looking around for a while for print sizes on a fire piston, and you have them. thank you for posting this- a machinists guide to making a fire piston.

    Very cool, but not exactly 'homemade'; maybe DIY, or shopmade, as most people (me included) do not have access to a metal lathe.

    Otherwise, good job, and you might consider marketing them.

    i have no access to lathe ,do you sell these