Small Surface Grinder Part 9 - S02E31 

In any work environment, supervision is paramount. Your supervisor just happens to have four legs, a tail and a coat to die for! What a lovely cat!

Good to see that you continue working on the surface grinder. Many good things have been already said in the posts below, like low end torque, inertia, continuous use, vibrations/damping, dust, whipping shafts at high rotational speeds (not an issue in Z-axis, super low rotational speed while grinding), bearing runout, ... Since you use ball nuts, be aware that they can slip under load (if stepper is at 0 current, not breaking). The Z-axis will slip down, due to its weight if stepper motor is inactive (0 current). The way I see it, backlash is of less concern on a grinding machine, used for standard grinding operations (different for a mill or lathe, or for "special" grinding jobs). For example, in practice you don't want to jog the Z-axis up and down while grinding. You want to feed it down until you hit the final dimension and surface quality. Due to the weight of the Z-axis, its bearing will stay pre-loaded and backlash is less of an issue (your linear rails in Z also help, close to zero stick-slip). Consider the feedback but decide fast i.e., do you want to take the feedback into account, yes or no? A YES is ok, but also is a NO. An operating machine "teaches" you what is going on in reality. That reality can be quite different from theoretical, limited engineering knowledge :) You will discover problems but having the operating machine in front of you, you will likely see more options how you can overcome a "problem", by creating a better feature or higher performance in the end. If you stay with conventions and wisdom, you will stand still. New paths can lead you to new places ... Good luck!

As far as dust mitigation and Labyrinth seals go, the little bit you'll be using it, you could air purge the cavity of the spindle with shop air compressor and an inline oiler, that's what the big boys do. You could even purge the motor housing with a small blower fan.

You might want to machine a case with a huge heatsink for the motor. Where you also can mount a nice pc fan. Or maybe just a water cooled system? There might be existing ones for those motors. Grinders produces insanely small dust particles that get EVERYWHERE and fly through the room. Sealing up that motor is not that hard but you need to cool it. I love that you guys do this project together and I cannot wait to see the end result! By the time you are finished you will have learned so much and aquired new skills that are worth A LOT.

That motor, if enclosed will overheat, they are designed to work with a certain amount of cool airflow, and to get that you need either ventilation or a heatexchanger of some sort. Also, the bearings on them don't last particularly long. Consider getting a RC inrunner with a waterjacket, commonly used on boats.

Normally that shaft is hardened and ground, concentricity is everything in grinding surface and cylindrical. Not being critical , love what you guys are doing!

You need to allow for thermal expansion of the AC Bearings. They will heat up in use and expand. Your nut will restrict the expansion, placing increasing pressure on the ball to race interface. Eventually the bearings will seize. What I use is a PTFE washer which maintains pre-load pressure, but compresses when the AC Bearings expand. Others use belville washers or high durometer ORings to perform the same function. In the real world of spindle design, run the AC Beraings in oil circulated by a pump through an oil cooler. This maintains a lower temperature and limits thermal expansion.

Cars often use sealed angular contact bearings for their rear wheel bearings, particularly if it is rear wheel drive. My BMW E30 has those, and they cost only about $80 for a pair of SKF bearings. I don't know your budget for the bearings, but sealed bearings are worth using taking into account their durability. Just a thought, might be worth looking into. Thanks for the free content, guys.

Love the project. One thing that I would consider is attempting to sensor the motor (look up adding hall effect sensors to brushless motors) because while not nearly as bad as attempting to use the motor for an electric bike (personal project) the wheel of your grinder has a significant rotational inertia when compared to that of the airplane prop that it is designed to turn. Might be worth looking into to avoid cogging.

Hey, the project looks like it's coming together well👍, with the design for the grinder mount I wouldn't weild it, I'd mount the bearing tube assembly inside of a big split cylinder clamp similar to how the inventables x carve type machines grip the spindle router, there's almost zero load in that axis on a surface grinder. Looking forward to seeing more 🙂👍🔧

aaaaand with that caliper slice you have one upped ThisOldTony. The setup. The payoff. The timing. It was all perfect.

Idea for you to think about... In heavy industry where seals cant be machined perfect because it is either too big or it would get destroyed to fast we often use positive air pressure. The idea is to get a seal as good as you can then run an air line in to the sealed air to create positive air pressure inside and keep the dust out. You would have to filter the air but it would also give you some cooling as a plus side. Just an idea to ponder over. Let me know if you need more specifics.

You can also grind the spindle in place it’s common on ultra precision machines

About grinder post - I think it will be extremely difficult to bore that bearing beds. As far as you gonna go pretty deep to the post there will be not enough rigidity of your mill plus boring rod. I'm still not sure about dimensions but seems that more than 100 mm. If you will share my doubts I will suggest you to use old school method to do the trick on the lathe. You need mount the grinder post instead of toolholder (I'm not sure how it is in English) and install long rod as bore in the lathe with back support so the rod will go though grinder post. Then you need to mount cutter to this rod and use longitudinal feed to cut the bearing bed. Then mount cutter to other end of the rod and make other bearing bad. The advantage of this method - detail is fixed, one installation of detail. Disadvantage - it is pretty painstaking process to install the detail right (on the vertical axis) and you need custom cutter. To create the cutter you could use cylinder cutter or peace of speed-cut steel.

I would move the motor and mount it so the belt is on the back. #1 Because you would have the spindle bearings completely enclosed #2 ease of belt replacement (no complete disassembly to replace the belt) #3 gets the motor away from the grinding wheel. #4 gives you the ability to change the pully ratio (overdrive/underdrive)

While your being all cool and building a arbor from scratch, I'd recommend building a spieth nut or similar for the back, this allows you much better control of preloading ours spindle bearings, with out messing up all that hard work when you come to tighten up the nut. I've made a simpler one for my mini mill, worked out awesome. If you need more info let me know

Hi Guys, Yes you do need the bottom bearing mount for the ball screw, they work together normally one bearing is fixed and the other floats just a little. Also consider some of the z fold way material to protect the z axis from the grinding dust. (The same cover that is on your z axis of your mill). Also the motor that you have selected is not a good option, it doesn't have any real "precision", considering getting a water cooled spindle and vfd kit from ebay. As you said it's a hobby motor, they are not designed to run at 8,000 rpm with that much rotational mass. Especially if your going to put a cover over it. When machining the spindle shaft housing once it's altogether it might fit on your lathe, remove your 4 jaw chuck and use a face plate.

A few comments on spindle design: 1. it's harder to make, but well-worth adding a standard grinding wheel taper to the spindle nose so you can use grinding wheel arbors. That way you can balance wheels off the machine and don't have to re-blot grinding wheels every time you change wheels. 2. Don't use that backside conrad bearing to preload the spindle axially. As the spindle warms up, it will grow axially relative to its housing and the bearings will lose their axial preload, and/or the grinding wheel will move towards the operator. Neither are good. I strongly advise setting the backside bearing to float axially (for thermal growth/shrinkage), and using your "labyrinth seal" on the front of the spindle to preload across the outer races of the angular contact bearings (which are better at taking thrust loads anyways). That would be a much more traditional and proven spindle design, while improving accuracy, rigidity, and bearing life. 3. You definitely don't want a thrust bearing on the back of the spindle as this bearing needs to take the belt sideload. 4. Designing the back spindle bearing to float axially also saves you the trouble of having to match the overall length of the spindle and housing (between bearing shoulders) and reduces the complexity of machining the spindle housing. Lastly it simplifies the spindle install steps, EG you can install all bearings on spindle, then insert combined bearing+spindle assembly into housing.

Something to think about with the small DC drive motor you are using is there is not much rotating mass to overcome the drag the grinding wheel will see as it hits different heights of the stock to be ground. I would test that motor to see how much force is required to stall the motor out as that is a big issue with smaller surface grinders. If it doesn't take much force (relative to the motor HP) to stall out a surface grinder motor then you will be limited to very light grinding cuts (both for depth and width). Also, my experience is that many of the DC electric motors get their horsepower rating due to very high RPM's, which means the torque component is low. Obviously, as you have already stated, you will get some of the torque back by gearing down the motor speed, but it isn't the same as having a higher torque rating motor to begin with. If you still want to use the DC motor, my recommendation is to put a fairly heavy flywheel on the back side of the spindle shaft so that you have some rotating momentum to overcome the stall force when the grinder hits high points on the ground stock. You could even add a braking system on the flywheel to slow down the spindle at the end of a grinding session. Neat to watch you guys at work on this and the other projects and best of luck.

I am a little late to the party since I just discovered this channel the other day. That being said, if you want to make tapping your holes a little easier, and with less chance of breaking a tap by having it misaligned, especially on one off parts such as this, drill a hole and then tap it before you move the mill in any direction. It works so much better than using a tap guide block, especially when using a tap guide in the check such as the one you are using.

take a look at the Harig spindle design with a bearing/spindle sleeve that slides into the spindle housing. eliminates the need to pull complex dimensions with little tolerance on a hard to turn piece. and you can add the ability to tram in the axis of your grinding wheel.

It’s about time you guys got cracking on this again can’t wait for the machining to start!!!

I am so excited to see the creation of this motor mount! I can barely wait!

Awesome stuff! For the ball-screw end support bearing, yes, its not necessary, but increases the critical speed before buckling/shaft whip, since its for height adjustment, probably not worth worrying about since screw RPM will never be high. On the bearing arrangement for your spindle, the main forces from grinding are likely radial, not axial, so less need to constrain axially. Would recommend roller bearings for higher radial stiffness, along with angular contact to constrain axially. Might add to your cost, but stiffness of ball contact vs roller contact is significantly different, lots of papers on it. Looking forward to the next episode!

no joke i was just thinking about your project when I was in the shower. went out grabbed a coffee, sit down to work and sure enough bam, new video. nice.

I may have missed it, but you’ll need a way to hold the shaft while you put on or take off the bolt holding the wheel on.

Best intro ever, can't believe I've missed out on this channel for so long

Changing belts is going to be hard, you allways need to think about maintinence when you are building something

Something people don't understand about these hobby RC motors is that they are designed for 5 minute RC races or for extreme forced air cooling like you would get in an RC plane or drone. So yeah, they can handle 1KW for 5 minutes, or constantly if they are in a wind tunnel. Honestly you should either limit the power to a fraction of the motor's rating or you should get a water cooled version, they aren't that much more expensive (you can easily make your own water cooling jacket with that lathe). There are also some inrunner motors with internal fans that would be a bit better off. BTW, the functional difference between high KV motors and low KV motors is the shafts are thicker because they are intended to run in a high torque low speed regime rather than a high speed low torque regime like you would see for a propeller or drone. The small bearings on the higher KV motors might not withstand the radial load forces and the thin shafts may deflect.

The surface grinders I have used, all had left hand threads for the spindle nut that retains the grinding wheel. Also, vibrations must be avoided at all costs, so I would consider single point threading for all threads on the spindle, which are ground on most surface grinders. You might get away with it as planned, but It's just my two cents added. Be careful, and good luck.

One of the few good things I have bought from HF is their large 2hp dust collector. You could use the suction through a cyclone/metal trash can to collect chips and blow the filtered air into your clean areas. HF also had a smaller dust collector last I went into the local store. Do not use one with an aluminum fan, they can burn, I have read.

NIce stuff... Been following this as I was half halfheartedly thinking of doing something like this too (small older SG's are hard to find nowadays). As other folks have already said, I think cooling might be an issue along with torque plus also think of the flywheel effect a large fat induction motor gives you to damp out any oscillation of speed changes (which could have an effect on your surface finish). On the bottom bearing for the Z axis, I agree with others, the thing will only be rotating when you make a down feed but... Think of the of the resonance of the unsupported shaft end, if it can resonate (which it will at some stage), it could also get into your surface finish. These things can be very finicky and even the tiniest little parasitic vibrations can show up in your surface finish. Another thing to think of is the expansion due to heating of the motor mount / spindle bearing / housing, with different expansion co-coefficients of your materials you could have some unwanted /unexpected increase / decrease in pre-load on your A/C bearing pair. Never worked with modern SG's but on the old J&S machines I used to run, we had to warm the spindle by running the wheel for an hour or two to allow the whole cast iron structure to normalise in temp before we could get it to hold to under a tenth. One last little snippet mentioned by "nraynaud1" about a wheel crash/Emergency stop, it could be an issue if you have RCCB / ELCB / fancy circuit breakers. I discovered on my BF35Vario mill this week, that reversing the X table traverse before the thing had stopped spinning (motor spindle that is), managed to create enough back EMF, that tripped my main breaker in my place (not just it's own breaker but the entire panel). More power to your elbow(s), wll done, I am itching to see this up and running...

freaking LOVE the CAD modeling timelapse!

Deformed lock nuts are probably made round then hydraulically pressed to deform them, so that they are slightly off round, and therefore grip tightly.

You should consider designing your shaft to accept standard grinding hubs Standard taper is 3” taper per foot, I have a couple hubs I can send your way

you can bore that spindle barrel between centers! mount the 'finished' spindle barrel to the lathe saddle. bore it with a great big boring bar that is turning between centers on the lathe with cutting inserts in fixed locations, then you just traverse the part across the tool. Your lathe should have the necessary bed length to pull this off if your spindle isn't longer than half the bed length. like so: i.pinimg.com/originals/83/7c/00/837c00221136fb9ee59d1259b2805e9d.jpg Back in the day this is how they did engine blocks, the lathe's own spindle, and other things you would never want to spin up in a chuck.

For the shaft, I would get all bearing fits .001 over the fit size then polish with emery to final fit sizes. Also on the bearing housing..I would weld it all together and mount in a four jaw chuck, bore the housing under sized then grind to final size. I made an adaptor so my die grinder can mount to the tool post, then with a small grinding wheel attached you grind your fits.Its crude but works and can achieve finishes to the ten thou range. Its extra work but worth a shot...then you will have a cheap tool post grinder as well.

The unsupported ballscrew on the spindle head will be OK. Traverse speeds are slow and the stepper is connected in line. If using a pulley and belt then the tension would pull sideways on the ballscrew and be bad for the main ballscrew bearings. Be aware though that these ballnuts have about 50 microns of backlash so either make sure the spindle assembly is very heavy and stays in contact with the workpiece, or add an additional ballnut to provide pre-load. When you inserted the stepper into the coupler it looked like it bottomed out in the coupler before the motor was seated. This will put axial loads onto the stepper bearings and wear them out. Just check it is clear, or shim the motor away. As for the spindle - I don't think a boring head in the mill will work. Reach is too far and you can't measure progress. Better to set up for line boring in the lathe. The spindle housing is bolted stationary to the cross slide, and a large diameter bar is passed through the pilot bore with a cutting tool, then supported between centres (driven by a drive dog). This is then used to cut the journals at each end. Here is one of my videos machining my spindle housing as an example: www dot youtube dot com slash watch?v=sYhDtuqzf2I

For Unified inch screw threads there are six standard classes of fit: 1B, 2B, and 3B for internal threads; and 1A, 2A, and 3A for external threads. All are considered clearance fits. That is, they assemble without interference. The higher the class number, the tighter the fit.

No technical knowledge to add but beautiful design work. Really enjoy watching. Can't wait for the next episode.

My worry is cooling of the motor without getting dust into it. This will be interesting to follow.

I know you have already finished this project, but did you think of the way the wheel will be turning in relation the bolt that holds it to the shaft. You are going to need left-handed threads on the inside of the shaft to keep the wheel from spinning off of the shaft. The wheel turns in a clock wise rotation causing the bolt to unloosen and coming off at maximum speed. By using left handed threads the bolt tightens up when the wheel rotates. Unless you spin the wheel counter clock wise the bolt will be ok as it will tighten the bolt.

When machining the housing, try to put on some counterweights that you later cut off to make the whole assembly more balanced in the lathe.

Hey guys I recommend you to mount a bracket with the ball bearing at the end of the screw. The reason would be the forces applied whilst grinding that my bend the axis depending in the material you are working at. For a best rigidity I really recommend the opposite bracket. Regards and awaiting ansiously for this peace of machine to work.

I’m thinking positive pressure into the motor housing to cool it and mitigate dust intrusion. Perhaps the output port on the housing should be a tube to get it away from areas where dust might enter while air source is off. Use the compressor with small nylon line and push fit connectors. They are good for very high pressure and you can crank up the air to keep the motor cool. Perhaps the exhaust air could be used for something as well.

WRT the bottom bearing block, I am curious too, in solid analysis it's hyperstatic, but in the springy world it make the carriage stiffer when you are towards the top of the travel. It's a bit counter intuitive, but if the nut is close to a single bearing, the play allows the free end of the screw too move a lot, that's where a extra bearing stabilize it in a radial motion. In any case, the axial motion must be blocked on only one side, the extra bearing should be axially free.

Those BMW annular bearings can possibly be adjusted tighter by popping out one of the inner races (after measuring play) and thinning it. The clearance is determined by the mating surfaces between the two inner races. I do not know the standard play since I have only disassembled ones that had failed. Bearings need to have room for the lubrication film so do not make them too tight or they will run hot and possibly ruin the bearing. Best to measure play before and after break-in and assess performance before adjusting them. Bearing companies generally have engineering manuals that specify rotating speeds, static and dynamic loads, temperature, dimensions, and a host of others.

Note that the N5065 motor you are using is rated with a peak output power of ~1kW and that is not its continuous rating! If you try and run it under that load continuously (or even a 50% duty cycle) you will smoke the motor in under a minute. However if you run the motor with forced air cooling you can greatly increase its continuous output. I measured the temperature rise of this motor under different cooling conditions in the following link: discourse.odriverobotics.com/t/testing-forced-air-cooling-with-a-5060-motor/483 Since you already have compressed air on hand you could probably use that instead of fans and get even more effective cooling. Assuming you are using the 48V odrive keep in mind you will also need quite a large DC power supply (>20A) or similar battery storage if you want to use the motor at 1 kW for seconds at a time. If you have any questions regarding odrive feel free to stop by the odrive discord channel.

As far as putting a bearing on the lower end of the z axis, it depends on how fast you plan to turn that screw. If it will be turning slowly you don’t need a bearing but to turn it fast to achieve fast axis feed rate you definitely need a bearing on both ends. If not it will whip around so to speak and introduce noise and vibration. It can also cause you to loose steps, reducing the accuracy of the move.

I really admire your ambition with this project. But I must mention that at this point of your project, your choice of a coarse thread and the use of a hex nut instead of a bearing locknut, will create issues when it comes to bearing preload and spindle balance

In all the production CNC machines I have worked on normally X and Y axis are floating on one side but Z usually always has a thrust bearing on the bottom and a ball bearing up top to stop any whipping action of the screw. The way I understand it that allows the bearing to take up some of the weight of the axis so it is not all converted to an axial load on the motor. In most machines I have worked on Z axis is also driven from the bottom and includes a brake and some sort of gear reduction but you are also talking about a ball screw about an inch and a half in diameter and an axis total weight of several hundred if not several thousand pounds. Going to a top drive with a small servo and no brake I would put a thrust or angled bearing on the bottom to hold some of the axis weight or almost all of the axis' weight will be hanging off the one bearing on the top and that did not look like an angled bearing. The other option would be replace the top bearing with an angled bearing. I also see you decided to use a bellows style coupling instead of a lovejoy style. That type of coupling is going to be prone to breakage on any axis with some weight to it from metal fatigue or in the case of plastic just deformation from the axial load. I'm not sure what the axis weight is currently but the spindle section you designed looks like it will be 20 or 30 pounds all by itself with that much 1/4 inch plate. I'm guessing maybe 40 or so pounds total axis weight with the wheel installed. Almost all that weight will be hanging off one ball bearing and then converted to axial load on the coupling. You will have a lot of flex in the bellows during movement.

howdy fellers! I heard you mention a milling operation for the IDs on the housing after they've had the weld work done. I think a boring head would do what you want, but it looks like your z travel on that little mill might not give you enough throat. If that's the case, you might have a little better luck with a turning op. As long as you have a lathe with enough swing; a grooving bar might just do the trick.

Watch out using the Chinese bearing blocks. I have found that most of them ship with regular deep groove bearings, instead of Angular contact bearings.

Hey Guys, change the Bearings!! The idea of oblique roller bearings is good but at the Moment you are Not able to tighten them. And take a Roller bearing at the end

Y'all do realize thats not the Z axis on a grinder. Its Y. In the case of a small surface grinder like this one the Y axis moves the wheel head up and down. In any 3 axis system the Z axis is the spindle. On a grinder Z motion will be the table moving in and out. X is table traverse back and forth.

Great video as always. 1) The belt arrangement is going to be a PITA if you need to change it, kind of like a lathe headstock. I was also concerned that the opening would allow grindings to collect inside tube and get to bearings. 2) Cooling was also a thought of mine, hopefully that motor is TEFC. Suggestion: Have shaft extend through plate with a pulley on the other side. Mount motor on that same side so belt can just slip over pulley. This would also shield motor from dust, allow open cooling, and allow tube to remain completely sealed.

Love that hand tap guide, have just about all the tools, but not that one!

You're going to need some pretty good cooling on that motor if you want to be able to load it down for an extended period of time.

Cool stuff, thank you for video. Hard soldering of premachined pipe could be strong enough with direct comparision to welding. It could potentially make machining process easier (18:26) - just grind, clean and remove oxides with few seconds acid treatment (last step is most important - degreasing bath). In theory one could just grind it and degrease it. Support surfaces must be rounded before soldering - smaller thickness of solder with better fitting makes better strength of joint. Rounding could be made with some cheap grinding plate, cut to necessary diameter, or sanding paper glued to wooden pipe. Soldered parts should be preheated- it simplifies, and shortens whole process. I bet that, soft soldering will be good enough;) More over I find room temperatures modern glues as really amazing in joining rough parts (60-70% of steel hardness). Roughing is easily attainable with longer metal pickling. Post Scriptum: I've been just guessing, I am not an expert.

Love the show I think it's totally awesome you guys are making this stuff by yourselves but I do have one thing to say if I got the order to make that spindle and spindle housing I would make everything first then assembled then weld and not just weld all of it in one sitting I would start by tacking everything first let it cool completely then in a Criss-Cross pattern began welding and again going slow using only tig and little by little but that's just my opinion I've made many many parts like that before and that's how I always do it but you might find a better and easier way of doing it also the long boring bar is a good idea until you go and try it lol I can never get enough room on the ways and never enough rigidity out if the bar if you find a way please show it off I'd love to learn it. Anyways love the show guys

If your z-axis ballscrew has a bend to it (like my cheap ebay ballscrew did) adding the bottom bearing block can cause a situation where your leadscrew can bind. You might want to use an indicator to measure any runout at the bottom end of your z-axis ballscrew through the entire length of travel before installing a bottom bearing block.

With those large gussets, it looks like overkill and a dust trap. The tube the shaft is in is also a dust trap and the gussets will just funnel dust into it. You have the opening for the belt, so at least some opening in the bottom to allow you to blow out whatever gets caught in there otherwise it will pile up and get into those bearings.

Fun stuff. Here’s a couple thoughts for ya: -rear spindle bearing should not be setup for thrust. Front AC bearings handle all the thrust and most of the axial load. Rear bearing is just to help support moment loads and maintain stability. If you load it in thrust, you overconstrain the shaft and heating/cooling effects will likely kill the bearings in short order from all that stress. - I’d go away from a post machining step on that housing. Welding induces stress and post machining will unbalance it. Expect weird distortion at that point. You could anneal prior to machining, but why not do more of a bolt together arrangement so you can turn the housing conventionally? Not to be a Debbie downer on it, but it really does make things much more challenging, both for dimensional stability and machining setups. - bearings will be operated at high speed... what’s the plan for lubrication? Unsealed bearings may not contain grease very well. - that motor seems like it wants to be located farther from the wheel ;) magnets and ferritic grit in close proximity. Yikes. That will be challenging to cover. Anyhow, you mentioned this, just thought it with reiterating. Have fun!

No matter how well you think that motor is sealed it's gonna attract steel dust. If you weak it air tight then your motor gets no cooling air.

On the ball screw, I'd mount a bearing at the bottom for vertical support, else you'd have all the weight of the grinding wheel assembly hanging off one bearing and unless that is a thrust bearing, it may end up failing.

Man, you guys do all the stuff I've thought about doing but was unsure about. I'm glad you're trying the brushless motor! I figured there had to be some reason people didn't use them, because they're ridiculously powerful for the price. I guess we'll see; the naysayers probably haven't tried it themselves.

Get some T handles keys for your torx and Allen screws... it would make your life so much easier XD

Do you have a lathe with enough swing for that bearing housing with the gussets ? If the answer is no: Do you have enough stroke and headroom on your mill to bore it there with a boring head ? And last: Do you have a boring bar that will do that depth without chattering ? If I had limited machine capacity I would have made the housing from square stock and bolted it to the gussets. That way it would be a smaller piece to bore.

I agree with a couple o the suggestions in other comments. A lock on the z axis is a good idea, especially for surface grinding. Electrically, they are fairly trivial to wire in to the system. Additionally, the bottom bearing is mostly to keep the ball screw from whipping. You likely won't have many rapid movements on the z axis so this shouldn't be a problem, on the other hand, the bottom bearing won't hurt anything and may in fact increase the rigidity of the ball screw set up.

I know im super late to this party, buy for operations like precision bearing fits in home made spindles, brazing is a great option for gussets, supports, plates etc. that need to be attached after the fact. If done right, brazing is near or equal strength to welding, plus you can mitigate any kind of warping to your spindle housing

There's speed limitations on using a lead screw with a single support. That's a fairly slow moving axis isn't it?

I would definitely add the bottom bearing. It would add a lot of rigidity to the grinding wheel assembly which would be beneficial if there are going to be large impact loads when grinding contact is made. Only drawback is mounting it aligned well enough with the top bearing so that it doesn't lock up.

You also might want to look into a way that you can look the Z axis. Even extremely small movements during grinding will be visible. A locking system might help with the last finishing pass.

Aww Yis! New PA vid! Easter is the best!

The shaft needs to be hardened and after that surface grind it by machine to be accurate. If it's not hardened it time the vibrations will affect the threads and the bearing area.

Invest in transfer punch set instead of using the drill to locate the holes.

r u gonna use cooling liquid for grinding or just dry grinding i would seal and coat everything bc you will have quite some dust everywere if u grind dry More than grinding with the big angle grinder You will inhale silica sand and the sand will destroy all your bearing surfaces and roller bearings even with dust covers And you will ruin every heat treatment on parts except u drive ultra carefull and slow with taking little material and pause for letting it cool down (witch will also influence your measuring and accuracy by heat shrinkage)

Use the bottom baring. Just thinking of rigidity, repeatability and you already have it. Plus you stated it'd be an easy quick mount up. So mine as well, just my thoughts.

1. Good choice putting the Z motor on top - from what I understand, putting it on the bottom leads to binding in the Z axis because the screw is under compression (instead of tension with the motor at the top). 2. Given that this is a grinder, there'll be no rapid Z movements, so there's no reason to use the bottom bearing. That would primarily be used to control screw whip, but with small and slow Z movements that's not a concern. 3. I agree with the other comments about coming up with some sort of locking mechanism for the Z axis. You don't want that wandering around at all during grinding. 4. I would highly recommend using a 3-phase AC motor and VFD instead of that RC motor. I've looked into using RC motors as spindles for things in the past, and for the cost of a sufficiently-powerful RC motor + power supply + ESC + other misc parts, you're basically at (or even above) the cost of a 1.5kW 3-phase motor + VFD. The AC motor has much more torque and (especially with a VFD providing variable speed) doesn't need high-ratio gearing/belting like an RC motor does. Plus, AC motors tend to be type TEFC (totally enclosed fan cooled), which makes grinding dust not a concern, unlike an RC motor. It'll be much easier to keep the AC motor outside the spindle housing where it can cool itself easily vs. trying to engineer a sealed housing for an RC motor that still provides enough cooling. In short, using a 3-ph +VFD will solve a lot of engineering and maintenance problems that using an RC motor will cause. There are VFDs that will take 120VAC power (if that's all you have available, I'm not sure, or there are 240V VFDs) an turn it into 3-phase 240V for the motor.

Yes, as much support as possible, prevent wear and tear, wouldn't be too much extra work and worth it in the long run!

Remember that most RC motors only achive their rated power with lots of cooling. Would probably be better to get something like a 2 kw motor and down rate it.

probably should secure the lower end of the ball screw because it mounted on a big vibrator. why no taper and hub for the grinding wheel? since you dont have alot of mass in the machine a balanced wheel is going to be critical, you could also do all of your operations between centers the whole frame looks like it just needs alot more mass you've built in lots of problems with the grinding particles, linear bearings, ballscrew and motors. maybe you should try to box in the table and use a vacuum as a way to control the dust

The only reason to have a lower bearing is to keep ball screw whip to a minimum. The top bearing should have some kind of axial thrust component, AC bearings, tapered rollers, blablabla. Being that it's a z axis on a surface grinder, I don't see a lot of rapid z traverse moves. You should be fine.

Nice So far! As for motor cooling, simply sleeve the motor with copper and convert it to liquid cooling then motor is mostly sealed. Do you think there will need to be a way to remove play out of the angular bearings once they have gotten warm? Perhaps some sort of set screw to place some pressure on them from an access hole (unless they are press fit).

You should probably add something to balance the grinding wheel. Also how are you going to machine your bearing housing? It's not a good idea to weld on something you've machined to tolerance and want bearings inside, so ideally you'd have to weld it up and then turn it on the lathe. Might be easier to just make it from a big square of steel or aluminum.

I just realized after part 9 that he uses microfiber towels to protect the parts from spatter. LOL

if you omit a load-bearing for the ball-screw, then the radial bearings in the Z-stepper will be holding the weight of the entire Z axis axially. something radial bearings aren't supposed to. I couldn't see if the included bearing was a radial or axial bearing, but you should definitely add a propper thrust-bearing (axial) to the bottom of the ball-screw, but don't constrain it in XY directions, as that will over-constrain the screw.

How will you cool the motor if it's sealed off from the dust? Looks awesome - looking forward to the next installment.

encase those motors boys!!!!

Adding a bearing block in the bottom roll over constrain the z-axis. Depending on the stiffness of the rails supporting the Z axis, the any run-out in the ball screw could cause movement of the z-axis in x or y axis. Just like z banding on a 3d printer.

Just a suggestion: Rotate the motor 180 degrees, increase the spindle shaft length, 3D print a fan and shroud that would push the air to the motor and at the same time, get the dust away from the motor.

Fine, left-hand thread for the arbour bolt?

Also you have now milling machine...if that centerpunch not going in, you can reworkit that piece to fits well...

Good luck with a level of the precision.

you should build in a way to clean of and shape your grinding wheel when its smeered up or eroded/grinded away

My concern with the small motor is how much torque it will be able to handle under the load of grinding. Even the slightest variance could impact the finish.

Cone see me in Chandler AZ, we can throw everything on the surface grinder. For freeeeee Make Everything square. I have a Okamoto 12-24DX at your disposal

I would think adding the bottom bearing would add some much needed Rigidity to this Beautiful Design! Have a Great Day Guys! Happy Easter!

Many CNC mills do not support both ends of the ballscrews on the vertical axis.

The spindle calls many-many questions! Better check how its done on industrial grinders. IMHO