DIY Milling Machine Part 1: The base and concrete parts 

Thanks for all the suggestions in the comments. I decided to scrape the surfaces and everything looks fine so far. There will be a video about that soon :)

Awesome project Alex wish you luck with the problem solving!

Great to hear you're not giving up on the project. There are always setbacks, though this seems like a big one, there is a way through. Looking forward to seeing what you decide to do.

I can guess how badly you felt when you started finding faults in your massive project. Hope you find a good, quick and not overly expensive fix.

I remember Stefan Gotteswinter describing use of a two-component epoxy for machine alignment, the way he did to tram his vertical milling machine. It's what I'll likely be using to build my own traveling gantry machine which, I have to say, I'm patterning after yours. It's a privilege to watch these - I'm grateful for the insight your videos have given.

The machine looks great! What a suprise! Thanks for sharing. Hope everything further goes well.

Hope you solve the problem. Best of luck! Looking forward to this great project.

Lovely that you explain how to hoist heavy parts to the downstairs milling mahine.

The best thing I heard from you in this video is "I won't give up". 👍

Wow, finally someone talking about the leveling problems they are having, and how crazy it actually is to get these things corrected. Thank you for this video, as I am having the same problems with my lathe build, and all of the videos out there doing these builds make them look so simple, but it really isn't when it comes to the fine tuning and leveling... Huge pain in the ass!

Life is a challenge Alex , good luck, Terry from Scotland

If you are confident that your left rail is straight then move the indicator base to a left cart, remove the right rail and start with your highest point and start working it down and measuring as you go. You don't have to scrape. I remember an amateur scraping video where he used a Dremel with a sanding drum for roughing in. Maybe just a stone with some WD40 by hand like someone else recomemded.

Can't wait to see the next video. Great job. Scraping really isn't that difficult, just time consuming.

Hi Alex, I really like your machine! You could make your own lapping tool by drilling a hole in the centre of your base between the rails. Get a piece of 5mm steel plate cut to a diameter large enough to cover all your steel mounting pads and place a hole in the centre so you can insert a pivot pin. Cast a concrete slab onto your circular plate maybe 5 or 10 cm thick for some weight and to stabilize the steel disc. Have the disc turned or surface ground flat. Now coat the disk and your mounting pads with lapping compound or valve seating compound and turn the disc a number of times by hand until you see your mounting pads have been flattened across the majority of their surfaces. You could also ask to borrow a granite surface plate from a machine shop. If you know where the surfaces are too low, coat those with a thin layer of slow curing epoxy. Cover the granite surface plate with plastic and the turn upside down and place on top of the mounting pads. The weight of the surface plate should force the epoxy to only fill the low spots. Hope this gives you a workable idea and good luck with the rest of your build!

Here is an idea if you can get one of the rails true with shims you could attach a bench grinder on the rail (maybe use the second rail as another axis to attach the bench grinder on) and grind it flat. Then reverse it and grind the first rail flat. Then use a flat piece of granite or iron with a precision level to check it. Just make sure you level your machine before you start using some geometry on the column. This idea is based partially on the jank o grinder from nyc cnc so watching their video may help.

great video! i've start getting the materials together for my build in australia :) thanks for the insights

Hi Alex, very impressive project! If the error is soo small, like you say, 10microns or less, yo can try to solve with fine sandpaper and trial and error, but its very time consuming.

hey alex, i made a CNC, i had the same problems as you, i grinded both with a big granite surface plate, i glued two 80 grit belt grinder paper and grinded by hand pushing back and forward 1000 times, eventually i had nearly 0.05 on 600 or 700mm length

Hey Alex! You are pioneering a new field with new problems. Don't worry you'll figure this out. :) One suggestion I have: Ever see how woodworkers flatten large slabs of wood that cant fit in a planer? They use a sled to make the surface even. I'd say you have the talent to make a very precise machining sled which attaches to the sides. You'd then be able to bring both surfaces to the same height with a cheap hand router since the depth isn't that much (< 0,5mm)

Yes, scraping! Always the best solution. You will be an expert by the time you get that all square :D

Awesome project. In order to decrease time for scraping you can try to use Zedex or any other competitor's product. It is a polymer. Easy to scrape. And can be glued on top of your inaccurate surfaces.

You should try to find surface grinding . But you need to do slot 1-2mm for grinding wheel out. In this case you ca made very accurate surface and side support.

Impressive build! Have you considered using steel filled machine epoxy such as DWH to set the linear rails on to achieve perfect accuracy? This could be a good solution for you and much faster than scrapping.... All the best.

I have read most of the comments previously written up until now. Maybe you can shim with something more pliable (easy to deform), like copper or tin. If you are able to fix the issues you can use the same method in conjunction with some adhesive like others have suggested. Just my two cents of thoughts. I'm sure you will figure something out. Good luck!

Hi Alex, hope your doing well. been watching for a long while, since you were building your first mill. Sorry to see that your having this problem. First it should be said that this error is actual quite small about .001 thousand twist total. Matthew here in the US state of Wisconsin, 40 years career machinist. Wish you were closer id jump in the car and come give you a hand. The error looked much worse than it is because as you have your indicator set up it magnifying the error by 8 x., but its probably enough to cause the block to bind up when all 4 blocks are bolted up tight. The best way to fix is to hand scrape, the scraper that i use i made from an old file with a small piece of carbide held in with a small clamp. For a master look for a hardened and ground parallel 1 inch by 2 by 12 long. Should only take a couple of hours to straighten it out, don't know if its just the one on the right or both. Ill check back later to see if you found this, post any questions if you have them. Oh ya celifane off a pack of cigs is .0005. good luck. Matt

Thanks for sharing your lessons learn, I plan to build my own machine soon and your video is a good help. The problem with casting with wooden forms like plywood, is that the pressure of fresh concrete can move your parts, wood is compressible and easily warp. The better way as a lesson learn you can use rigid form like steel plate reinforced by steel rods and nuts in betweens. Epoxy grout is also better alternative and can pour slowly by layer to reduce pressure.

Have you thought about lapping the surfaces? If you watch Tom Lipton's videos on them, you can likely build your own laps.

Great work Alex, what type of concrete you use, and what are its technical specs Thanks, 👍

There is shimming stock called onion skin available on ebay. As thin as .0002 inches. CNC4XR7 used it on his linear rail conversion.

Awesome project! Don't despair. Scraping isn't hard to learn. I learned to do it in less than an hour. The only challenge is scraping multiple sides, but your scraping job is among the more simpler challenges. You only need to ensure the bed and column ways are perpendicular. I would get a large flat granite piece. You can get them for cheap from a kitchen counter fabricator. If you still want someone to help you, try contacting Stefan Gotteswinter. Btw, he demonstrates another method where he uses epoxy as a "liquid" shim.

Have you tried contacting Stephan Gotteswinter? He definitely knows scrapping very well, although that might be too big of a project for him. Maybe he knows someone with a big surface grinder that can help you. Greetings from Portugal. Looking forward for more progress on this beast.

I would use a surface plate and scrape the surfaces for flatness and parallelism

Could you CNC the bottom of the linear rail, instead of the top of the steel inlay? Much easier to get that to a machine shop. Or failing that, add a ~3mm spacer bar between rail and inlay on both sides, machined to compensate for the inlay's imperfection?

Hello. Congratulations on your work. Can you tell us what brand of linear rails did you put on your machine ?

Looks amazing Alex, could have warped a lot worse. Build your own surface grinder and grind it on the spot.

... or you can collaborate with somebody who have some experience in scraping and proper tools. it may be a good variant overall. ( 1. you don't need to move your machine 2. you learn and practice in scraping 3. you get more content for youtube )

how % difference and means to performance of your machine from using linear rail guideway @ 25mm instead of those bigger you use now ?

Another possibility if the two surfaces are close to flat would be to lap them in. You can get large old cast iron laps for not too much money on ebay, and use it across both surfaces at once to even out the twist. Just start with a more aggressive grit lapping fluid to move more material

Usually I'd mount the carriage in a vice and indicate bottom of the rail to see if groves are parallel to mounting surface first. If they are the error can be caused either by one rail going up or twisting away (and it's probably the latter as you said). Instead of scraping you could just stone the surfaces, applying more pressure and spending more time on the high side. If it really is twist, then indicated 0.1mm means "only" 0.02mm to be removed.

How did you manage to get good and true holes on drill press without cross table? I could never get serious precision on drill press.

Hi Alex, very impressive project! I am building one soon, i am finishing my CAD file. Can you tell me what aggregate you used, like what size of sand and in which mixing ration ? Thanks !

They can't steal it, that's for sure! :-)

Is it Possible to make a temporary grinding tool that mounts to the one good rail to machine the surface of its pair. it would not be exact with such large overhang but would bring the run out much closer for scraping. I wish you luck and hope for the best.

Have you considered using a large thick panel of plate glass, glue a sheet of automotive sandpaper and then use it to rough lap then fine lap the rails?

Hi! Thank you for VERY interesting videos!! I did need to see them to trust that tis kind project is possible to do bt one man, thank you again!! Where did you find those linear bars? I cannot find these from anywhere, please help me..!!

Hello! Serious project! Is the information private? What concrete or mixture did you use to make the machine bed? Have you noticed any deformations or changes in the geometry of the machine over time?

You have a Typical modern day way of thinking and solving problems . You have to many options . Today people have a tool to do anything . You have the answer to your problem. Scrape it you will be surprised it will take you a lot less time and work than hauling that back outside . It is a slow process but you will learn and appreciate it more. Scrape measure scrape measure. Every machine tool of old was hand scraped. I'm retired now but my fist accurate item to make was a one inch cube out of cold rolled steel cut from a 1.25" plate, I was about 16.The only tools we were allowed was a hacksaw and one file. For ever one thou you were out of square from all sides, was one mark off. Good luck with your project it looks awesome.

Hello, awesome project. I would appreciate if you are be able to share with recipe of epoxy granite and which resin did you. I look forward to hearing from you.

Don't worry about the surface in the base, just take the rails off and grind them to match the base. Instead of small shim, surface grind more on one side of the bottom of the rail.

Awesome project. Would you mind to share the link where to buy the linear rails like your or their specs? I can't find them in this size. Thanks a lot.

Scrapping steel is a massive undertaking grinding is your only feasible option

You could have used industrial steel section box those sizes as horizontal/vertical beds. Drilled, tapped plugged & machined; then filled with Granite concrete aggregate or concrete. The concrete idea will be constantly moving about like a machine shop floor. In answer to your problem make a x-z axis plate 3" /75mmm thick flash ground of graded steel commercially available - take your guide rail system off x/z and fix to the machined plates 3 mm deep slots as soft mallet fit ~ and drill and tap and locate your linear guide rail/s system. [ reason is that the concrete hasn't the inertia power under the creeping process of settling concrete to warp steel plates. Steel cover plates stronger than concrete. ] I hope this of an idea for you Sir.

Nice project Alex. I look forward to seeing it progress. Forgive me if this has already been asked but what concrete have you used? I've been researching how ordinary portland cement corrodes steel and your remarks about how it "flows" tells me this isn't just any old concrete :)

Looks amazing, can you share the recipe of concrete?

You can add some epoxy resin... there are some made just for shimming machine parts, super sturdy, super hard, can solve your problem

Its look pretty

Build two dams or troughs around each of the mates (ply/mdf with a release agent works) and pour about 3~5mm deep and low viscosity epoxy grout on them, make your own grout with epoxy and carborundum, aka silicon carbide, 600 grit, an extremely fine and hard dust. You need to choose a very thin epoxy with a slow set up time and pack it with the grit but not so much that it becomes a mastic paste, it needs to flow still, aim for the consistency of warm black honey. It will flow to perfect flatness, I.E as flat as the curvature of the earth which for the spanned distance is certainly more than good enough. If you connect the two troughs with a channel between them at each end you will also achieve perfect parallelism between the two. This is how it is done with extremely large machines with rail mounts too large to mill, and also, my own. Premade mixtures also exist, look up epoxy bearing grouts like chockfast, nordbak etc. P.S. You can coat your rail mount bolts with melted beeswax and screw them into your mounting holes prior to the pour, they will release after it sets leaving a nice wax coated hole.

You can correct the error by CNC program

Hi Alex. Can you tell me exactly where you got Nanodur cement from and how much it cost? Same with the additive used in the recipe. Thanks.

Just remove your rails and install a precision ground plate about 25-40mm thick and re-fix your rails to that.You will loose some spindle height but it will be flat.You can use longer screws to fix through your rails through the plate into base rails.You can shim the plate to it's final position and then epoxy it so it becomes rock solid with your base.The epoxy cement will act as grout to fill in the gap between the plate and your base rails.

Hi Alex! I have question regarding thermal expansion: Is there potential problem with combining UHPC concrete with steel parts (or is it cast iron?) in it? Something like a "bimetal" effect? Thanks! Milan.

Hi Alex , love your project, saw the title and thought you were building something to mill concrete 😂, I have never thought of this idea of an actual concrete machine , what is the reason for choosing concrete ?

I don't think this is a big issue. Although you read approx 0.1 mm deviation on the dial indicator, we're talking about a deviation of approx 0.01 mm on the guides foundation. If you're sure that the origin of the deviation is the foundation twist of one guide (and not an overall flatness error), I think this won't affect too much to machine accuracy.

Take the rails off and hand scrape the table below until it’s flat then remount the rail.

I do hope you found your fix! Even if it consists of taking it back to the machine shop.......next time check the work before you go home! Lol

how the hell did that happen?? werent those surfaces milled in place at the exact same time in the exact same fixture? the machine looks incredible soo far, im jealous.. I guess that .2mm would irk me also , seeing as how everything else was going well.. I wonder if you could surface grind the tops of the linear rails and correct the issue , or would the side ball guides still cause it to ride high? subscribed

How about working a calibrated granite surface plate inverted onto the rails with fine grit water paper ? Blue the plate up first just like you would if you were going to scrape it, then just work it back and forth. Then scrape to final flatness. Might just work. ( I read below that the inlays have edges. maybe just grind those off before you start, then you would have to make some other plan for alignment) good luck

Where did you buy the rails?

It would be nice if you explained why you used UHPC rather than epoxy granite. Which is better in terms of accuracy in the long run for a precision CNC machine?

Achei uma ideia excelente usar concreto comum para a base da máquina. É barato, relativamente fácil, mas o concreto não é ruim pra absorver vibrações? E o concreto quando curado não contrai, deixando as partes chumbadas com uma brecha? São dúvidas que eu queria tirar, pois tenho interesse em fazer como você fez, mas tenho estás dúvidas. Muito obrigado, e agradeceria mais ainda se vc pudesse me responder, obrigado.

Hi, is concrete dimensionally stable enough for such purpose? I know it shrinks during the curring process, but don't know for how long. Maybe this is the reason of warping? Many use epoxy granite for CNC bases, as it is maybe superior material, but I suppose it's too expensive for such big machine.

Maybe Grind the botton of the rails ? Dont mill it ....put it in surface grinder. Or make few mm /cm flat steel / aluminium bar as a shim :) (or just make 1 big few cm thick steel plate) for me second option is the best idea becouse even if u make if wrong on 1 side ....u can remake it :)

Hello Alex, I'm currently designing a cnc gantry mill with the sole purpose of machining steel and aluminum. Roughly a 20" x 20" x 10" machining envelope. I will use concrete like you to add mass and rigidity. I really like your cnc machine do you have a design of it? My biggest worry is will my gantry be rigid enough. I am thinking of sharing my design now for collaboration from other builders. Did you collaborate with others to fine tune your design? Great job on the mill and thanks for sharing... Mike - Plus8Precision

Hi! Any news yet ? If you lived in sweden I would help you face it. I would probably take it out again and mill it with a large facemill and also check it with a dial indicator before I remove it from the machine. Easiest would probably be a large knee mill.

Can you give some information where you bought your UHPC? myuhpc or durcrete? Did you think about shrinkage over time? UHPC tends to do this unless it's been annealed (48h at 90°C) Very nice project!

Very impressive build! What is the linear rail size on all Y, X and Z-axis? I understood the square profile is 50x50 so the rails must be 35mm? Also what is the brand of the rails.

Hi Alex, great project! Can you give us more details about concrete recipe? Is it possible to make/find all ingredients somewhere else or only buy from specific company?

Hi Alex, are you able to share your CAD files? I’m planning a very similar build and it would be a great starting point! I’ve already checked out your friend Sebastian’s project. Thanks!

What size are those rails?

If it's a twist. Buy a reasonably sized surface plate, and some fine grit sandpaper. Tape the sandpaper to the surface plate. Lay the surface plate across both rails. Elbow grease. Not perfect solution, but effective.

I've seen several videos! but I can't know what kind of concrete or epoxy is used because nobody shows them in detail, and what about sand? and cement?

I don't know if you've solved this yet, but maybe this could work: Alternate version of scraping it in. But hire someone to create an ultra precise hand scraped (or if good enough, ground) master to match the rail mounting surfaces (as they are meant to be) and have them ship it to you. That way you can expand your geographic radius of who can help you. Then you take over and blue the master, run it along the mounting surfaces (both the flats and walls) and clean them up until they are perfect (or good enough). This would require less metrology tooling on your end, and less effort and skill in scraping. Also things of this mass are flexible, especially on the scale that you wish to achieve precision, so moving it out of your basement and back can reintroduce errors, even if the gridding or milling you do again is better than the first time. So leaving it in its final resting spot is best to then scrape it in. Ignore everyone saying to touch the rails. These rails, no matter how expensive, are not designed to be perfectly straight or flat or whatever. They rely on your mounting references to achieve straightness and parallelism. The only true relationship between surfaces on the rails are the bottoms, one side, and the bearing races at any "2d cross section" (because again, they can be ever so slightly twisted or bowed). Any other surface is not useful as a reference. that is an incredible job so far, i understand the feeling of finding out your reference surfaces are not up to the job. a few months back i "finished" a CNC router only to have the gantry immediately rack and kill the ball nuts on both Y axis'. Of course I was using aluminum extrusion and aiming for a level of precision 1 to 2 orders of magnitude lower than you. But spending a year designing and building only to get so close to done and then catastrophe is heart break. I agree, do it right, and do it once. Good luck

remove the linear rails, have the bottom of the rails machined in a way that will correct for the discrepancy? Or add a block of steel between the body of the machine and the rail and have this machined to correct for the twist instead of having the entire block machined.. this way you don't have to take the whole concrete slab to the big milling machine again. What you think?

THIS MACHINE IS INSANE ! ( in a good way ) Is this UHPC or "normal" Concrete ?? and Greetings From Finland

Stefan Gotteswinter might be able to help you out but in sure you already asked him

What size linear rails are you using?

Hi Alex. Great build so far, following along on RU-vid and on Instagram. Just a question, I have been thinking. Of doing a cnc with epoxy granite, but after seeing your build, thought that the concrete route might be a cheaper route seeing that epoxy is very expensive. Just wondering how you were able to get the mixture for the concrete to have the right strength for what you are using It for. Also is it a special type of concrete or can I use the 52N concrete for the mix? Anyway. Hope you can help. Cheers.

Guess no mineral concrete for these? And not precision ground but milled?

Hi Alex; let me tell how I would tackle this situation hoping that maybe you would find something useful in my explanations . 1) I would look for the ''best'' spot along the inlays where I could find 3 points, and I will explain the reason for them in a short while; these should be 2 points on 1 inlay and another 1 point on the other inlay. Where about these 3 points could be found is debatable. They could be found at either end of the inlays or, why not, right in the middle of the inlays. These 3 points should be chosen so that to be as close to one another as possible. More precisely: if , say, your X axis is 500 mm, I would choose the first point at 240 mm on the LEFT inlay (measured from the Z axis outwards), the second point at 260 mm on the LEFT inlay as well, and the 3-rd point at 250 mm on the RIGHT inlay; 2) Say that your X axis inlays are 300 mm spaced apart from one another; I would make a rectangle out of ordinary steel, about 500 mm /300 mm and I would drill/insert 3 bolts and cap nuts (semi-spherical nuts) at precisely 240 mm and 260 mm on one longer side and at 250 mm on the other longer side of the rectangle; 3) I would attach on this rectangle as many dial indicators as I could afford, perhaps at least 4 dial indicators on either side, spaced apart evenly and I would place the rectangle on the 600/430 granite plate that you already have; 4) I would set all the dial indicators to zero and than I would transfer the rectangle on to the 3 points on the inlays described earlier; this way , the lack of coplanarity becomes measurable and you can start scraping the inlays because you would know where and how much. Here is the thing: it wouldn't make much of a difference if it was in the middle of the inlays or 100 mm in or out, provide that you would place the rectangle every time in the same spots. What matters is for the 3 points to be as close to one another as possible because it is this closeness that makes it a viable solution. Have fun !

I figured out how to make it perfect bud! First pick the 2 rails that are PERPENDICULAR TO EACH OTHER...2nd put your indicator on THAT RAIL,,run it all the way down the bad side writing on the rail and a pc of paper the amount it is out INCREMENTALLY and mark front and back etc. After you figure out exactly were it is (hopefully not wavey) you can flip it over and shim exactly what the error is and mill the bottom....make sure you machine the HIGH RAIL !!! HAHA,, i would ether hold it in a few vices with jacks under it or on magnets. Hope this helps! I really wanna build my own as well but cant decide on a size yet...ive done large custom machining on mazaks ,Nicolas correa's, n Cincinnati's for the last 14yrs,,n 12yrs in job shops making little parts before that. Remember measure once,,cut twice! Haha!

Surface grinder.

Hi Alex, Nice project. What was your concrete recipe?

Hi Allex, would you like to Share the the drawing of this project!! We can try to learn something! Please..

Awesome project Alex! Can you please tell me the manufacturer of the concrete you used for the base?

Hast du es mittlerweile gelöst?

Nice machine, why not just strap a grinder on a cross slide, and mount it to the z axis then surface grind the 0.1mm off. Use a paint pen and paint the ways, then grind both. It's like surface grinding on a tool grinder.

Why concrete instead of epoxy granite?

A linear guide is statically over-determined. _Four_ linear guides even more so. The dial-gauge test proves nothing. You should not be using the rZ-position from the linear guide in the first place. Are you _sure_ that the rails are not coplanar (ignoring the rotation-direction)? You could test this by having a laser-pointer on a carriage with three (not four!) balls, two resting on one rail and one on the other. When you slide the carriage on the rails, does the laser-pointer deviate substantially? If so, your recourse is to shim the second rail to make it parallel. In any case, the carriages on the linear rail must be decoupled in all but 5 DoF total (e.g. 2 + 2 + 1 restricting degrees) if you hope to achieve precision at all. Dan Gelbart has a nice video-series on RU-vid, and has designed and built his own ultra-precise lathe. Perhaps some inspiration there?

Perhaps shim with epoxy?

Maybe you could use Diamant Plastik. Stefan has a Video about it for tramming his Z Axis.