Introduction: KEG LATHE

I have found instructions on how to convert kegs, using reciprocating saws, grinder, and plasma cutters. But in my experience, kegs which are ground or sawed generally produce uneven or oval openings. Plasma cutters on the other hand produce outstanding openings; unfortunately I don't have many friends who have them at their disposal. So I came up with a different way of cutting the opening. In essence, I have created a hand turned lathe for a keg. It cost me around 30 dollars, but depending on your own personal inventory of tools, the cost may be higher or lower. The project took about 3 hours which included the construction, cutting out the opening and smooth out the edges.

Note that working with tools and metals always have the potential to cause harm, therefore I explicitly state that none of this information is guaranteed NOT to make you suffer an injury, lawsuit, material economic loss, time in jail or impotence. I refuse to take any responsibility for anything that happens to you as a result of using the advice stated in this instruction set. In short if you feel responsible enough to take on the project, then you are responsible enough to deal with the consequences of your own actions.

Step 1: Tools Used on the Project

The image below has been color code to help you identify what each item is and when each item is used. Yellow designates the set-up process (Phase 1), Green the cutting process (Phase 2), and Blue the clean up process (Phase 3). The Brown color denote items which are used in more than one phases.

A: Small Vise
B: Marker
C: Saw
D: Drill bits
E: Tape Measure
F: Screw driver bit.(use the one which match your fasteners)
G: Lathe Tool Holder.
H: Wrench sized for Tool Holder
I: Tool Steel Lathe Bit
J: Pliers
K: Half round steel file
L: Aluminum Oxide Sand Paper
M: Aluminum Oxide Spindle Sander
N: Drill/Screw Driver
O: A paper towel.

Other tools "Not Shown":
If you are using an unaltered keg you may need a pair of needle nose pliers, and a firm rubber mallet.

Step 2: Keg Prepping

For this project, I have been given a keg that someone tried to convert. The original fabricator cut out the opening and then chose to abandoned the project because of their poor results. The illustrations have been based off of this keg. If you happen to be converting an unmodified keg, many of the steps in this project will still work, however you must prep the keg in order for you to work on it.

An unmodified keg, will need to depressurize and the stem should be removed. First depressurize the keg by depressing the center plug. Placing a towel over the end may save you from getting drenched when the keg gasses out. Once the keg has been depressurized, remove the snap ring from the inner lip of the center hub, and then simply remove the tube assembly. Once the stem is removed, you may want to rinse the interior in order to cut down on the smell.

If your keg will be subjected to high temperatures, you will want to inspect the lower lip for vent holes. Recently, a keg exploded during a brew session, apparently enough pressure built up during the boil to fracture the lower ring, causing the pot to spill it's contend and destroy the burner. Luckily no one was hurt. So please take a look, if you do not see the holes, get a new keg or drill some holes in the ring.

Step 3: Phase 1.0: Basic Set-up

The first thing you will need to do for this project is find some place to work. I have chosen my work bench, as it has a plywood surface, which allows me to fasteners items directly to it. When setting up your lathe, have the keg handy, you will need it in order to adjust the placement of the casters and vise. I have provided the general dimension which I used for this project, depending on the size of your vise, casters or keg your dimension will change.

Frame A:
I first started by scribing a line from the center-line of the vise to the back of my bench. Next I mounted the casters 4-3/4" off the centerline and check for clearances. In order to check for clearances place the keg on the rollers and check to see that the keg is stable. The four rollers should be running on the flats of the keg at all times. Look to see that the keg is not touching any unwanted surfaces such as the vise and the table top. You will also want to check whether the tool and bit will fit in the vise and reach the cutting surface. If you should run into a problem, make the corrections and recheck the clearances.

Frame B:
Cut two pieces of 2x4 at 20 inches in length these pieces will act as the top roller supports. Center the pieces on the rollers and transfer the distances back to the boards. Next mount the remaining casters on the center of the two boards.

Frame C:
This image is strictly filler material; the image shows the rollers in their mounted configuration.

Frame D:
Find a piece of wood large enough to tie the two rollers supports together. I mounted the two rails at 13", if I were to make this lathe again; I would align the rollers to match the lower ones. Currently the rollers are at a slight offset which seemed to cause instability when I turned the keg on the lathe.

Step 4: Phase 1.1 Basic Set-up:

Frame A:
Frame A, shows an image of a finished side supports. To create these pieces, cut the horizontal member to the same size as the bridge piece, in my case 13 inches. In order to determine the length of the vertical pieces place the upper roller assembly on the keg and level it. Next take a measurement from the bottom of the runner to the mounting surface of the lathe. Once you determine the distance remove 1/8 of an inch. This gap will provide a method of tensioning the keg to the rollers and will help in the controlling the cutting path of the lathe.

Frame B:
In this frame size counts, if you happen to have long enough screws ignore this step. For us the less fortunate, drill some hole about 3/4 of the way through the horizontal pieces. These holes will be used later to mount the supports to the table.

Frame C:
Once the pieces have been cut and assembled, soft fit all the pieces around the keg. The upper roller assembly should have a little slop and the legs should be square along the side of the keg but not touching. When you have finished making the adjustments, secure the side supports by drive four screws through the lower side supports into the table.
To mount the upper roller assembly, drill a hole on each end of the cross members, these holes should allow the mounting screws to fall through. Make sure that the holes line up with the vertical leg supports as you will be securing the assembly to it. The final step will be to secure the assembly to the support legs. As you are screwing the assembly down check and see if the keg spins freely. You will want to apply enough pressure to spin the keg, while restricting the up, down, and side to side motion. In my experience the tighter the better, but this will make you work harder. Remember if you need more adjustment you can always cut off a little more off the side supports.

Step 5: Phase 2.0: Setting Up the Cutting Tool

In this step we will set up the lathe tool in order to cut through the top of the keg. You will need to have an good idea of the opening you wish to have. So measure your lid, heat exchanger or what ever else you wish to put in the pot.

Prepping Steps:
Prior to mounting the lathe tool in the Jaws of the vise, take a measurement from the inside edge of the keg to the other. Subtract the required opening from the previous measurement and divide by two. Use the resulting measurement and place a mark on the keg to signify the approximate opening.

Mount the tool bit in the tool holder. Remember to mount the cutting edge in such a way as to allow the bit to cut when the keg spins. See Frame B for a close-up.

Frame A:
Take the tool holder containing the bit and place it into the vise. Gently tighten the tool so you can make your final adjustments. When setting up the tool try to position the bit on the centerline of the keg.

Frame B
Using the opening marking, move your bit as close to the dot as you can. When adjusting the bit try to get it as close to 90 degrees off the cutting surface. You will also want to adjust the bit in a way that will allow only the tip to touch the metal. Once all your adjustments have been made tighten the vise down so as the tool will not move. Also check to see that the bit is secure.

Step 6: Phase 2.1: Turning the Keg

This is the step that will make you sweat. When rotating the keg it is important to use smooth motion. You will also need to pull the keg towards yourself in order to have enough pressure on the bit to cut into the surface.

Frame A:
First rotate the keg slowly in order to create a light scribe line. If you look carefully at the image in Frame A you will see a light scribe line. Although the zoomed up image in frame A is poor, it shows a line passing through the mark which designates the opening. If you are unhappy with the cutting path make the adjustments and re-scribe the line, otherwise continue with the turning process.

Frame B:
Start spinning the keg at a faster rate, after a while the ridge will start to deepen and widen. It is not uncommon for the tool to jump out of the forming groove. When this happens stop rotating and move the bit back to the path. The close up in Frame B, shows how the groove is forming. Take notice the line above the red dot this is one of those malformed paths. It occurred when I was rotating the keg with a jerking motion. Some of these groves can be cleaned during the final phase of the project, but others will not.

After a while you may notice that the bit is not cutting efficiently, remove the bit and see if it needs to be replaced or redressed. During this project, I needed to replace the bit and readjust the tool, by making these changes I was able to significant decrease my keg spinning.

Frame C:
It will take about 15-30 minutes to break through the keg, when you do stop rotating the keg. At this point the metal should be thin enough to fracture along the cut. I was able to use pliers to break the piece free, by giggling the metal back and forth. If you have an unmodified keg, use a firm rubber mallet to strike center hub. You should start seeing the metal fracturing along the grove. When using the methods above, be careful not to bend the metal which forms the opening.

Frame D:
This is what the piece looks like after it has been removed. Be warned this item has a very sharp edge and should be handled with care.

Step 7: Phase 3.0: Edge Maintenance

Edge Maintenance is essential once you have cut the hole into the keg. At this point the opening will have razor sharp and must me dulled. I leave the keg in the lathe while cleaning up the edges; this allows you to rotate work the edges quickly.

Frame A:
This is how the keg will appear once the kegs lid has been removed. In many cases when you remove the lid there will typically be some residual beer left inside. Due to the keg's condition when I received it, I was able to give it a quick rinse prior to starting the cut.

Frame B:
I typically use a half round file to knock the jagged edges quickly. Start working the keg, and rotate it as you go along. Some areas may be raised to slightly out of round, the file will help you smooth out these inconsistencies. Once you are satisfied that you have filed down the sharp edges move on the next step.

Frame C:
Now that all the sharp edges have been removed, you can use the sand paper to sand out the marks left by the file.

Frame D:
In some cases when turning the keg the bit may jump the ridge and create a burr on the top surface. I have found that these areas can be difficult to smooth out when using sand paper and a sanding wheel is helpful.

It is important to note that stainless steel can rust once the outer coating of chromium has been broken. That is why stainless steel needs to be properly pacified after it has been cut or welded. If you wish to know more on the topic of pacification of stainless steel, look to our friend the internet for help.

Step 8: The Clean Up....

The title says it all. In reality there isn't much mess from the cutting process. I use my shop vac to clean up the debris. You may need to spend some time on the inside of the keg removing any filings that may have fallen in. Using a mild detergent and rinsing throughly should do the job.

Step 9: Things I Would Change.

Over all the project went smoothly, however if I had to do it all over again, or had a cool time machine, I would change the following:

I would make sure to mount the upper and lower rollers in-line and move the rollers out board as far as I could. Keep in mind that you need to use the handles in order to turn the keg, so you wouldn't want to move the support piece so far out as to interfere with your knuckles. I feel this will cut down the frequency of the bit slipping out of the groove.

Gloves... definitely gloves. I went to a festival my daughters, and left with some angry children. It seems as though I have developed the uncanny ability to pop balloons simply by touching them. You won't believe how many slivers I have found imbedded in my hands.

I would choose a different bit, something like a threading or undercut bit. The one issue I see with this bit is wear. If you are unable to redress the bit then you may want to consider a square bit that has the ability to cut from either end. Do not use a carbon bit, they will fracture often. They work great in one direction, but because we are turning by hand any reverse the motion on the bit it will cause it to break. I only recommend using tool steel.

Step 10: Get a Keg Legally.

Is this legal?
It is not legal to get a keg by paying the deposit on it, and then assuming you can do whatever you like to it. These things cost a substantial amount of money to the local and commercial breweries. Paying a $10 or $20 deposit is by no means an excuse for cutting one of these things apart.

Additionally, costs incurred by breweries are simply passed on to consumers via higher prices, so you are doing the entire beer-drinking community a dis-service by cutting one of these things up. Do everyone a favor, and buy one from a documented, legal source.

There has also been a movement by the corporate breweries to enact legislation in some states to protect their assets. You should check to see if these laws will effect you.

Try to find a keg through a legal channel. Kegs can be purchased from companies like Sabco or Tosca. You may also be able to find kegs from salvage yards, although these kegs may not be in the most pristine shape, they do function well as brew kettles.

Step 11: FAQ:

A converted keg can be used to brew beer, fry a turkey or even cook corn. Let your imagination run wild. My plans are to brew 10 gallon batches of beer. These kegs once converted, would then be called a Keggle.

Adding a Motor:
I'm sure you could add a motor, However I never felt the need to go through the trouble. If you use the right bit, you will quickly cut out the opening. At the end of the day I feel it's balancing between functionality and practicality.



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    42 Discussions

    Hi all : I have modified a few stainless steel kegs, making stills ( leagal in NZ, for home use ), and brewing vessels. From my research, they are heat treated, after robotic welding, and will handle up to 90 PSI. If they are modified, and any welding done on them, they should NEVER again be used as a pressure vessel. When cutting & tig welding, to "stack ), to increase volume, I use a modified el-cheapo vice grip, with a piece of steel banding, with holes drilled, about 40mm apart, using a uni-bit. Clamped around the circumferential weld site, this allows for quick & easy tacking, prior to welding.

    crapflinger asked my question, so I'll just leave this comment:


    There ==> A place, as in "over there"
    They're ==> They are, as in "they're to young"
    Their ==> Belonging to them, as in "enact legislation in some states to protect their assets."

    Sorry, but I can't help myself.

    Otherwise, a very detailed and well done instructable. Good pictures. Great step by step. You included what problems we would run into. Good example of how to post here.

    10 replies

    two ==> one more than one, as in "now there are two comments on grammar"
    to ==> towards, in so far as, as in "working to rule"
    too ==> in excess, as in "they're too young"

    Sorry, it looks like you can't help yourself

    SMACK! ==> The sound my hand makes against my forehead when I realize I made a grammar mistake while correcting grammar!

    SMACK! ==> The sound my hand makes against my forehead when I realize I made a grammatical mistake while correcting grammar! :-p

    "They're ==> They are, as in "they're to young"


    To ==> Preposition. "I'm going to the market."
    Two ==> The number 2. "I have two apples"
    Too ==> In excess of something. "I have too much time, so I correct people's grammar"

    Yea, Mister_Caipirinha already pointed out how much of an idiot I am! :)

    Lol, guess I should scroll down and read all the comments next time...

    No. When you do something as stupid as I did here, you deserve to have it pointed out however many times it gets pointed out. I mean, how much more of an idiot can you be thatn to say "You're an idiot because you did something that I'm doing right now!" I know that my treatment of fredan was not as harsh as calling him and idiot, but it still works out the same in the end!

    Thanks for the input, grammar and spelling have always been my kryptonite.

    Mine as well. That's where the pet peeve comes in. It took me so long, and I had to work so hard, at getting over the There/They're/Their and Your/You're things (and now the To/Too/Two!) that it became a pet peeve for me to see them used wrong. But, if you have a kryptonite, that makes you Superman!

    What are you guys doing with these? I seem to be lost as to why you want kegs opened up

    trust me, you don't want to use a threading tool to cut a piece of metal. it seems like a good idea at the time, but it isn't, and this is the enwisened tone of experience talking. the finishing is also a bad idea. I'm an engineer and I have worked in a machine shop, and of these your best bet would be the grooving one. just turn your tool holder so that the front of the tool is parallel to the face of metal to be cut, and the blade is facing against your rotation, i.e. if you are spinning keg clockwise, and tool is at bottom of keg, the sharpest part of the blade should be to the left. it will definitely turn out better no pun intended, it should take less time, and be easier on you and your tools.

    1 reply

    oops. I put left. I meant right. sorry mate, I miss small details from time to time.

    As a Keg is designed to be emptied standing up, you can tip it on its side to depresurize. This will take the lifter snorkle out of any liquid left in the bottom of the keg. This is assuming your not using a keg thats more than half full.

    I had a good curb side find 3 years ago, a complete but old Shop Smith that will swing a 16 1/2" object. The Vari-drive pulley system was stuck with a bolt missing allowing the pulley to jam against the frame tubes and trip the motor overload. I added a bolt and washer, all is well. Added a live center with a machined step sleeve that fits into the filler neck. A 1/4" metal disc 14" diameter is threaded, bolts thru the Shop Smith's 6" aluminum face plate to become one with the Shop Smith's spindle. This steel disc fits past the rolled bottom of the keg's edge. On the disc I welded three 1/2-13 nuts. Thru the nuts are long allen bolts with a point to bite into the bottom kegs skirt above the rolled base lip to center and turn true plus drive the keg. With the vari-drive at the lowest setting plus the use of a 20 amp autotransformer the rpm's become rather slow. I did use a lathe parting bit in a tool holder to cut 10" open tops into my kegs. A plate with a tool post arm that is "U" bolted to the Shop Smith's frame tubes. A smaller open top allows for a lot less open surface area for less wasted boil off hence more net bier. For cutting a keg body a 10" vertical and horizontal rotary table with a crame mount and the same live center for the filler end with the keg horizontally mounted on the Bridgeport Mill. With the hand crank rotary table for cutter feed speed control. A 1/4" stubby carbide 4 flute cutter leaving five 3/16" long uncut sections to keep the cut apart keg sections together until all mill cutting is completed. Later cut the five 3/16" bridges and dress flat. This way kegs can be extended to higher volume plus a light tight gap to be Tig welded later. The Shop Smith can also be used to polish kegs which is useless as they will be insulated anyway. Function before beauty when dealing with your taste buds. Your lathe idea parallels what I came up with instead of a grinder as I wanted a narrow machined gap to reuse the cut top as lids again, just add SS tabs. A great idea your lathe built, congrats. The only complaints are from those that did not machine their keg lids off, just using grinders. Cheers and hats off to your project. member.

    Very good idea using the rollers. This idea can be used for cutting other Cylindrical items

    Could a commercial keg like this, with a hole cut in the bottom and a valve added, be used to brew a batch of beer and then turned right side up and put in to a kegerator system for force carbonation and serving? What would you use to seal the new hole in the keg and have it stand up to pressure? Thanks

    1 reply

    I don't feel it would be feasible due to the heating issues you would have with the seals for the stem