An Enhanced X2

Very nice. Looks like you are getting very close
 
I am thrashing on what to do with the head rotation. I'd like to use a worm gear to make moving the head exact, but the design is a mess for a hobby project. I may just dump the gear part. The cost of 6" diameter stock is also daunting. I'm not sure how my little HF bandsaw will do cutting 6" rounds either. I wonder if I can get away with using aluminum instead of cast iron.
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If it's any help, I dragged back a nice bandsaw from Michigan that'll easily handle 6" stock.
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This weekend is full up with things to get done, but I should be around during the week and next weekend. Finally getting time to get back into the shop!
 
I am thrashing on what to do with the head rotation. I'd like to use a worm gear to make moving the head exact, but the design is a mess for a hobby project. I may just dump the gear part. The cost of 6" diameter stock is also daunting. I'm not sure how my little HF bandsaw will do cutting 6" rounds either. I wonder if I can get away with using aluminum instead of cast iron.
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How about using a blank back plate for a lathe chuck? https://www.amazon.com/South-Bend-L...8-1-spell&keywords=southbend+blank+back+plate
 
It has been a fun 2 weeks. I ordered 2 6"X1" aluminum disks for the rotation. I shouldn't have.

Getting the worm/gear set into the saddle was getting to be a bit tedious, then I discovered the real problem. The bolt track around the fixed disk for a +/- 90deg rotation would require a full circle slot. I would need a T-slot milled into the fixed disk to do that. I should have looked at the available T-slot bolts before ordering the metal. The slot would make the outer lip way too thin to reliably clamp the moveable disk. Moving the slot into the disk was not an option because the T-bolt would foul the spindle box. The clamping power of smaller bolts is suspect. I have since discovered motor mount problems, so I'm glad I resisted the temptation to order bigger metal. The question became, do I really need +/- 90? The motor control box is on the left side of the head. The control box would prevent the spindle from getting very close to the table, so counterclockwise rotation was not very useful. Only rotating clockwise reduced the required slot down to 120deg. That would give me 10deg counterclockwise for tramming purposes and 110deg clockwise for horizontal operation.
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The object in the center is an acetal axle.

I turned up the studs in only a few minutes on the lathe running at 560rpm. I love my threading clutch.
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This is the test fit before I reduced the saddle to put the spindle back in the center of the table travel.
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The motor problem I mentioned before? The original motor mount would put the motor where the aluminum disks are. I will have to make a belt drive conversion. I had planned to do that eventually. I guess eventually has become soon.
 
So when it rains around here, it pours. The spindle bearings make noise. There is a clicking sound when the spindle is rotated by hand. I checked preload and investigated the transmission gears, but it is the upper bearing that isn't smooth.It sorta sounds like there is a loose ball that is rattling around inside. The mill has been terribly noisy for some time. I always assumed that it was gear noise. I'm glad that I found it before it seized up. New bearings are pretty reasonable. I suspect that it is shipped with ABEC-1 bearings judging by what LMS wants for replacements. I ordered ABEC-3 bearings to replace mine. They should be here Friday.

Tonight I took the spindle apart. It went reasonably well.
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The new bearings arrived! It was a lot easier to put them in than I had feared. The saddle, rotation plates, and spindle box are now intimately connected. On to the belt drive!
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I have been working on the belt drive.
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I had to attach the left ear to an aluminum angle. I could have waited until I could get a larger piece of plate for the base, but I'm getting impatient with the delays. The motor mounting plate is not shown. It was a seat of the pants project. In making the plate I was lucky to plan far enough ahead to notice that the drawings from other belt drive projects were for a different motor than I had. At least the mounting holes for my motor didn't match what I had down loaded. Once I had the motor mounted, I turned my attention to the pulleys. I knew that the pulley designs that I had should fit, but the rotational addition made space tight. I made the motor pulley first. It was the most space restrained. At that point I came up against the metric conundrum us Americans face with these machines. I needed a pulley bore for a 9mm shaft. I could fake that with a #T drill. The thing I couldn't fake was the key slot. None of my imperial size broaches would work, and a $40 broach from the far East hurt my cheap skate mentality. Fortunately we had a get together of Florida machinists and Mr. Ogberi fabricated a a tool to cut the keyway on his S/B lathe. It worked.
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With the pulley mounted on the motor, and the motor on the head, It looks like the original spindle pulley design will work just fine, We started the spindle pulley at the meet, but I will have to finish it on my G602 tomorrow. And then, yes, there is another metric keyway to cut. At least the next one is 5mm and the bore is big enough to swallow a standard cut off blade.
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The finished pulleys -
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I had to do some fudging to get the spindle pulley to work. The main problem is the low cost (cheap) way that the Chinese locked the spindle nut. They used a set screw that bore against the spindle threads instead of a lock nut. The pulley needs to sit up higher with my motor mounting arrangement. Here is what happens to the set screw -
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Can't see it, can you? I can make up a spanner to tighten the nut but there is no way to lock it in place. I considered using a thread locker, but I'm nervous about depending on it to keep the 4Krpm pulley on. My plan is to put a steel, keyed washer that is left over from pulling the original bearings, between the top bearing and the pulley. That will raise the pulley enough to clear the deck of the motor mount base. Then on top of the pulley I will put a keyed spacer from the unused gear stack on top of the pulley. The nut can then be run on and the set screw is accessible and able to grab the spindle. -
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The belt drive is now ready for a belt and testing. That will have to wait until the belt arrives in the mail. A 2L130 is too short and a 2L150 is a little too long to work with the motor pulley to head clearance. A 2L140 turns out to be special order.

The stain on the pulley drawing is not rust. It is BBQ sauce. You central Florida machinists missed out on some fine food.

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I have been working on the Z axis drive. My original slap together conversion of the X2 used the rotating nut, fixed screw design used by Daniel Kemp. I decided to look at other designs since I had the chance to start over. The fixed screw, rotating nut designs are much simpler to execute, but they all have what I consider a serious fault. The screw extends into the swarf generating area. The lubrication on the screw would retain metal particles. The Asian 1605 series ball screws that I am using do have a wiper of sorts, but they aren’t very effective. The X and Y axis are mostly protected by the saddle and table, but the Z axis is not easily covered. The rotating nut is more complicated to execute, but the screw stays above the head and therefore out of the primary swarf cloud.

The axle and bearing stack that carries the drive gear and the ball nut has a problem with backlash in the Kemp design. In the cross section drawing, red represents the axle, blue the retainer plate, and green the thrust bearings. The only way to adjust the pre-load, or lack of, is to change the length of the axle by putting shims between the axle and the retainer plate. That is a bit inconvenient when trying for minimum end play (backlash) and adjusting for wear.

Cnc z axis mount.jpg

A better way to handle fixing the axle would be using the same way the X and Y axis do.A single nut with set screw or even a double nut that would allow adjustment to eliminate backlash. The top of the axle where the gear and screw will mount is 2.5, the axle is 1.25”, and the threaded portion is 1-14. I didn’t have a nice piece of 2.5” round bar laying around, so I shrunk fit the axle to the top. I heated the top to 275F and froze the axle for an hour. It dropped in a little over half way before seizing up. Being prepared for such an event, I whacked it twice with a #2 hammer to seat it.
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