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Thread: PM1022 lathe CNC Conversion

  1. #21

    Default Re: PM1022 lathe CNC Conversion

    I'm in Fusion. Nice to see I won't be the first! I'll be checking out your conversion thoroughly.

    OP, photos are working in 17, 18, 19.



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    Default Re: PM1022 lathe CNC Conversion

    I just posted my CAD files on grabcad. https://grabcad.com/library/precision-mathews-pm1228mv-lathe-conversion-1


    The bigest problem I had was getting a ballscrew in the saddle. The largest that would fit is a 1204 and it is TIGHT. I went with direct drive at the rear of the sadle to keep everything out of the way in the front.



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    Default Re: PM1022 lathe CNC Conversion

    OP, photos are working in 17, 18, 19.
    Yes, pics OK ...



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    Default Re: PM1022 lathe CNC Conversion

    Hugh, as you have found, the ways protruding into the ballnut slot is a problem. The only solution is to mill a pocket into the underside of the cross sllide. That is what I did on mine. Mine is a PM1228, but it looks very similar. Also, you could easily extend the ballnut slot forward by a bit so that you can get the 5" of travel back. I did not do that but probably should have.

    PM1022 lathe CNC Conversion-x-axis-ballnut-mount-jpg

    PM1022 lathe CNC Conversion-cross-slide-bottom-jpg

    Here is my solution for covering the ways. I made a sheet metal channel that slides into the T slots for the front and rear of the cross slide. Since the X axis motor is on the rear, on my lathe, the rear channel is longer. This works really well because they can easily be removed by loosening the set screws so you can access everything.
    PM1022 lathe CNC Conversion-cross-slide-assembly-covers-sensor-bar-jpg
    PM1022 lathe CNC Conversion-cross-slide-front-cover-assembly-jpg

    Attached Thumbnails Attached Thumbnails PM1022 lathe CNC Conversion-cross-slide-bottom-jpg   PM1022 lathe CNC Conversion-x-axis-ballnut-mount-jpg   PM1022 lathe CNC Conversion-cross-slide-assembly-covers-sensor-bar-jpg   PM1022 lathe CNC Conversion-cross-slide-front-cover-assembly-jpg  

    Last edited by maxspongebob; 10-11-2020 at 11:32 AM.


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    Default Re: PM1022 lathe CNC Conversion

    Hugh, also, by positioning the X-Axis screw in just the right Y plane, I was able to us a direct drive on the X axis instead of using a belt. You might be able to do the same.
    Here is a bottom view of my sadle assembly.




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    Default Re: PM1022 lathe CNC Conversion

    Thank you for the info. I haven't looked at your grabcad drawings in any detail. But the number of parts gives me hope as my part number increases. Not a trivial project. Yours looks very nice, congratulations.

    Thanks.

    I also have a 1204 ball screw for the X. My decision was based on what others have used for 10" lathe conversions, mostly G0602. It is an incredibly tight fit. Others have had to cut most of the ball nut flange away and mine will be the same. I'd have guessed the 12" lathe would have a little more room, guess not. I'm going to put the stepper on the front of the machine tucked under the apron with a timing belt drive. Like you I want to keep the motor from sticking out too far. For me space is critical.

    Quote Originally Posted by maxspongebob View Post
    I just posted my CAD files on grabcad. https://grabcad.com/library/precision-mathews-pm1228mv-lathe-conversion-1


    The bigest problem I had was getting a ballscrew in the saddle. The largest that would fit is a 1204 and it is TIGHT. I went with direct drive at the rear of the sadle to keep everything out of the way in the front.


    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    maxspongebob:

    I think I can sneak the X ball nut in without cutting a pocket into the cross slide. It is very tight and I may still have to, but hopefully not. Cutting a pocket would give more meat for the cap screw holding the ball screw nut to the cross slide to bite into. This would be nice. But I can't raise the axis of the X axis screw, at least not with the 9x24x7 angular contact bearings I plan to use. The bearings would interfere with the cross slide.

    I did find in the stock lathe the cross slide hits the X axis bearing block before hitting the front of the saddle pocket. In my design I've extended the bearing housing to give more cross slide travel. Then to get all the travel back I'll have to cut the front of the pocket out some. That does leave a path for swarf to get into the ball screw and nut. I haven't found a way to put wipers on this X ball screw so this could be a problem. I've been thinking of a rubber flap connected to the cross slide. However, the cover you came up with may be the best solution. Thanks.

    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    Hugh, I just went with a 10x18x5.5 thrust bearing instead of AC. I was forced to raise the CL of the screw up .108" to get the bottom of the nut to clear the ways. That forced me to use a smaller diameter bearing.



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    Default Re: PM1022 lathe CNC Conversion

    I have a sketch of the conversion shown in the first picture below. The red box to the left goes where the headstock gearbox is on the stock lathe. Details on this soon. The bearing block on the right contains the thrust bearings for the Z axis. Still some details to work out here. And the red "box" where the apron was on the sock lathe just contains the ball screw mount for the Z axis. That ball screw nut mounts on the right side of this box.

    PM1022 lathe CNC Conversion-solid-2-jpg

    The large hole seen on the right side is for a telescoping spring screw cover. Like these. The problem with retrofitting these to an existing lathe is they take up 2 or 3" of saddle travel near the headstock. A problem when working close to the spindle. But here the apron is empty so I hope to build a recess that accepts the telescoping spring when compressed. Will be slick if it works.

    I think the details on the X axis are worked out. The second picture below shows an assembly. The 1204 ball screw nut is a very tight fit as others have noted. Like they, I plan to severely cut the ball nut flange to gain space, leaving only two mounting holes in the top flange. As others have, I'll build a bracket, here in green, that the nut mounts to and in turn mounts to the cross slide. The numbers say it'll fit but who knows.

    PM1022 lathe CNC Conversion-solid-3-jpg

    The stock bearing block is replaced with a new version shown in green. It mounts to the saddle as the stock block did, but whis an extra mounting hole (at the bottom, easily seen in the third pic) to go into the apron box. It's longer than the stock block for more cross slide travel and contains the angular contact bearings with grease seals. The light blue bearing retainer (light blue) bolts on the end of this block to compress the bearings OD solidly to the block. The motor mounting plate also bolts to an outer ring of this bearing block. The short NEMA 34 stepper is mounted to this plate.

    The third picture shows the same parts in a cut away.

    PM1022 lathe CNC Conversion-cut-1-jpg

    The fourth picture shows a close up view of the bearings stack. The inner spacer rings (dark gray shown as full rings) are clamped solidly with the inner races of the bearings to the ball screw shaft. The clamping puts force between a shoulder on the screw, these spacers, the bearing inner races, the timing belt pulley and retaining nut. The outer rings (shown in gray but cut away) clamp the outer bearing races to the bearing housing. The clamping force goes from the bottom of the bearing housing bore, through the spacer rings and bearings, to the bearing retaining cap. So the outer races are solidly clamped to the bearing housing. The outer red rings are grease seals, lightly pressed in, aren't in the load path for inner or outer bearing races. The trick is to get the two spacers between the bearings races sized to give a slight pre-load and prevent backlash. They will be adjusted upon assembly. If I could afford matched angular contact bearings I could just clamp them together and count on zero backlash, but alas.

    PM1022 lathe CNC Conversion-cut-2-jpg

    I just need to pull out detail drawings for these parts and I can start making them. I'll probably finish the Z axis design and order all the material at once. I find the steel store here is very lacking in materials and it'll be less expensive to order online than drive to Phoenix. It looks like through mail order free machining steel, 12L14, is only slightly more expensive than A36. 12L14 is so nice to work I'll probably go this way for most parts with aliminium plate for the box sides and motor mounts.

    Anyway it's a start. If you see anything amiss please let me know. It'll be much easier to correct now than after parts are made.

    Thank you.

    Attached Thumbnails Attached Thumbnails PM1022 lathe CNC Conversion-cut-2-jpg  
    Last edited by currinh; 10-26-2020 at 12:30 PM. Reason: Correct Pictures
    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    I have some more details worked out. The first attached picture shows the overall conversion. Not much change since the last picture but more detail filled in.

    PM1022 lathe CNC Conversion-full-jpg

    The Apron is made of three aluminum plates. The sides are 3/4" while the front is 1/2". The 3/4" plates are so the outside edges match up with the saddle edges. The three pieces are held together, and to the saddle, with socket headed cap screws. The first attached apron picture shows the headstock side. The brown part bolted into the apron is a recess for the telescoping lead screw cover. It will likely be a three piece fabrication of lighter steel. The second apron picture shows the tailstock side. Here the Z ball screw nut is mounted to the right side of the apron, the yellow piece just visible. The brown part mounted on top of the ball nut is a retainer for the tailstock side telescoping spring cover. Flat head screws are used as the face of this retainer needs to be flat.

    PM1022 lathe CNC Conversion-apron-1-jpg
    PM1022 lathe CNC Conversion-apron-2-jpg


    Attached Thumbnails Attached Thumbnails PM1022 lathe CNC Conversion-full-jpg   PM1022 lathe CNC Conversion-apron-1-jpg   PM1022 lathe CNC Conversion-apron-2-jpg  
    Last edited by currinh; 10-26-2020 at 12:31 PM. Reason: Correct Pictures
    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    I've also worked out the headstock "box". This holds a NEMA 23 motor and bearing for the free end of the Z ball screw. The box is made up of four aluminum sides (in red below). I'm not sure the front is needed but it does add some rigidity and serves as a belt cover. The bottom and left side are open. I thought it prudent to put in a cooling fan which is a 60mm muffin fan. I've found 110V fans of this size so I should be able to easily route power to it. The front will need to be removed to adjust the belt tension. Once the front is off just pull the motor outward and tighten the screws from the outside. The slots for four socket head cap screws can be seen on the right side. The bearing block is shown in green. It has an extension tube to retain the telescoping spring lead screw cover. All sides are 1/2" AL except for the front which is 1/4". It's all held together with socket headed cap screws but for the front which uses button headed caps.

    PM1022 lathe CNC Conversion-headstock-1-jpg

    The second picture of the headsctock is shown without the front, top & right sides. The NEMA 23 is bolted to the motor mount with no adjustment. The adjustment, as above, is gained though screws holding the motor mount to the right box side. This aluminum motor mount is just a hollow box with cuts for the belt. The box back, if all goes well, will bolt to the headstock casting using the same taped holes which originally held the gearbox. The box top will need to be bolted to this back before assembling to the head stock.

    PM1022 lathe CNC Conversion-headstock-2-jpg

    The third picture shows the bearing arrangement at the headstock. The deep groove ball bearing (red) is pushed up against a shoulder on the Z ball screw (screw not shown). The clamping force goes through that shoulder, the bearing inner race, and the 40T pulley. It is clamped solidly with a nut on the end of the ball screw. The bearing is free to move axially in the bearing retainer (green). This bearing keeps the ball screw in line and resists the side load from the timing belt, but doesn't resist axial motion. The axial motion is resisted at the tailstock end.

    PM1022 lathe CNC Conversion-headstock-3-jpg

    It is coming along.

    Thanks.

    Attached Thumbnails Attached Thumbnails PM1022 lathe CNC Conversion-headstock-2-jpg   PM1022 lathe CNC Conversion-headstock-3-jpg  
    Last edited by currinh; 10-26-2020 at 12:33 PM. Reason: Correct Pictures
    Hugh Currin


  12. #32
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    Default Re: PM1022 lathe CNC Conversion

    The last piece of the design is the bearing housing at the tailstock end.

    PM1022 lathe CNC Conversion-tailstock-1-jpg

    The brown tube is a recess for the telescoping screw cover and is simply screwed to the bearing block. It will likely be a fabrication of two steel parts.

    The base of the bearing block (green) is too long to use the existing taped holes in the lathe bed casting, they would hit the bearings. So, a spacer (red) is put between the base of the bearing block and the bed. It is bolted to the bed and then the bearing block is bolted to it. It's held to the bed in the same manner as the original, two socket headed cap screws and two 6mm taper pins. I doubt I can match the taper pin holes well enough so probably just line up one. I could drill out the holes for 1/4" dowel pins. This would make it hard to replace the original, which hate to do. The bearing block is designed to bolt to this spacer with two socket headed caps and two 3/16" dowel pins.

    PM1022 lathe CNC Conversion-tailstock-3-jpg

    The last picture shows a cut away of the tailstock bearing block. The brown spring recess is simply screwed to the bearing block with flat head screws. The arrangement for angular contact bearings and grease seals is the same as described for the X axis. The bearing outer races are clamped solidly to the bearing housing using spacer rings and a bearing cap. The inner races are clamped solidly to the ball screw using inner spacer rings and a nut on the end of the ball screw. Again, backlash and pre-load are adjusted by the size of the inner and outer spacer rings between the bearings. Those to be adjusted upon assembly.

    PM1022 lathe CNC Conversion-tailstock-2-jpg

    Lots of details in here. I've pulled detail drawings from the solid models in enough detail to hopefully build from. I'm sure there will be errors and unforeseen problems once I start making parts. But I've done all I can on paper so those problem will have to be corrected in the real world and revised on the drawings.

    I have most of the large components in hand, motors, bearings, seals, ball screws, etc. I also have most the the material ordered, if not found in the scrap bin. Time so see how much trouble I'm in. :-)

    Thanks for coming along (if anyone is).

    Attached Thumbnails Attached Thumbnails PM1022 lathe CNC Conversion-tailstock-1-jpg   PM1022 lathe CNC Conversion-tailstock-3-jpg   PM1022 lathe CNC Conversion-tailstock-2-jpg  
    Last edited by currinh; 10-26-2020 at 12:34 PM. Reason: Correct Pictures
    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    Having the drawings for my conversion in hand I went to the shop and started construction. The first order of business was to make a "plug" to mimic the X Bearing Block to check alignment.

    PM1022 lathe CNC Conversion-xalign-1-jpg

    This aluminum plug is a snug fit to the hole at the front of the saddle for the X lead screw. I bored and reamed a 1/2" hole through this plug. Then a piece of drill rod fits through with little slop. I then measured (and measured and measured again) the clearance. The alignment angular wise is off slightly. The main offset though is a shift to the right side of some 0.075".

    I also drilled a scrap piece of aluminum to see that the bolt circle on the drawings matched that on the saddle. It didn't. It was off far enough that the bolts would not fit. I decided to put points on two set screws and transfer the saddle holes to the X Bearing Block. (This turned out to work well.)

    PM1022 lathe CNC Conversion-saddlebolttest-jpg

    I then started to build the X Bearing Block. I cut the basic shape on the lathe starting with the "spigot" that fits into the saddle hole for alignment. I then transferred the mounting holes from the saddle drilling those on the mill. Then mounting on the saddle allowed a line to be marked on the block where the saddle lines up. I then cut the block flat on top to this line using the mill.

    PM1022 lathe CNC Conversion-xbearingblock-1-jpg

    A mounting plate was cut on the lathe which the bearing block was mounted to for boring the inside clearance and boring the recess for mounting for the bearings.

    PM1022 lathe CNC Conversion-xbearingblock-2-jpg

    Since the alignment of the lead screw hole in the saddle was off some 0.075" I offset the holes and bearing mount bore to the right. This picture shows that it was moved enough to be visible.

    PM1022 lathe CNC Conversion-xbearingblock-3-jpg

    It turned out upon inspection to be some 0.090" offset, a little too much. I did this by offsetting the mounting plate in the four jaw chuck and bored. On the mill I centered on this internal bore and drilled the holes for the bearing cap and motor mount bracket. You can see the holes in the front of the bearing block are all shifted left.

    PM1022 lathe CNC Conversion-xbearingblock-4-jpg

    Stupid me, I should have offset the spigot on the bearing block rather than offsetting the holes in it. But if I start re-making parts at this point I'll make no progress at all. Maybe remake it later when I'm bored (ya right!). It will be solid and workable, just look a little off.

    The original bearing block sits up above the saddle stopping the cross slide from moving forward. The new block allows the cross slide to move over the bearing block giving additional travel (or recovering some travel lost to the ball nut assembly size).

    I cut a fake ball nut assembly from aluminum. It's the size of the nut and mounting bracket with a reamed 1/2" hole where the ball screw will sit.

    PM1022 lathe CNC Conversion-xalign-2-jpg

    It is a little tight now on the right side. I may have to open the slot up some 0.020" or so. That shouldn't be a problem. But it fits very will to the bottom of the cross slide and clears the Z ways. That's good news.

    I'll probably put a drill on the end of the 1/2" drill rod to drill the back of the saddle. Seems like an easy wasy to align that hole. The ball screw would then extend through the saddle. This would positively prevent the ball nut from winding off the screw. It would also give end to support the ball screw, although I doubt it needs it.

    So moving along slowly.

    Thanks.

    Attached Thumbnails Attached Thumbnails PM1022 lathe CNC Conversion-xalign-1-jpg   PM1022 lathe CNC Conversion-saddlebolttest-jpg   PM1022 lathe CNC Conversion-xbearingblock-1-jpg   PM1022 lathe CNC Conversion-xbearingblock-2-jpg  

    PM1022 lathe CNC Conversion-xbearingblock-3-jpg   PM1022 lathe CNC Conversion-xbearingblock-4-jpg   PM1022 lathe CNC Conversion-xalign-2-jpg  
    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    I made some progress, mainly with the X ball screw. I decided the best way to machine the end of the ball screw was with my tool post grinder. I made this some 20 years ago when I needed to machine the end of another ball screw, for a knee mill conversion. It worked well then but has seen little use since. For this job it worked very well.

    The disadvantage of grinding is that it is a very slow process. With some 0.002" at a time it took awhile. But the advantage of grinding is that it is a very slow process. Taking a thousands off at a time is quite possible in sneaking up on a bearing press. Nice finish too. The alternative would be lapping. That process is even slower but likely more precise, it gives a constant diameter, while a tool post grinder is limited by the accuracy of the lathe. Lapping also gives a very nice finish.

    PM1022 lathe CNC Conversion-grinder-jpg

    I used AL soft jaws in a three jaw chuck on the lathe. More to prevent marring the screw than for precise alignment. i.e. I didn't re-machine the soft jaws. I first chucked the screw close to the jaws and ground the end for threading. I may have been able to use a cutting tool once through the ball screw threads, but I just used the grinder. Once to 5/16" I used a die to thread the end. The screw was case hardened as the die was able to thread the end. (Others have found the same). I then re-clamped the ball screw and machined a length for the bearings. The picture above shows part way through this. The picture below shows the results.

    PM1022 lathe CNC Conversion-xmachined-jpg

    They keyway was cut for a 3/32" key. Less than 1/8" so I needed to use a 1/16" end mill. Slow going, with baited breath, as my mill doesn't have the speed for small cutters. Cutting the slot raised a burr which had to be taken down with emery paper to allow the bearings to again fit. But all turned out well.

    The ball screw is a hodgepodge of dimensions. The bearings are 9mm ID forcing that section to be metric. To not mess with change gears, or buy a new die, the thread is 5/16-24. Finally, to use the broaches I have, for the pulley, I made the keyway 3/32". So a 3/32" keyway in a 9mm shaft. I will need to make a bushing for a 9mm bore, but not buy a new broach.

    I also made the bearing spacers. For these I cut about an inch of tube from solid steel with the correct ID and OD. One the the inner rings and one for the outer. I ground the OD of the inner rings as they need a good finish for the grease seals to ride on. Then cut off rings of the correct width. The middle rings, between the bearing races, will likely have to be adjusted for backlash. But for now they are ready for initial assembly.

    PM1022 lathe CNC Conversion-xspacerrings-jpg

    In the picture one grease seal is pressed into place. I forgot to pull the second seal out for the picture, but it will fit as the one shown does.

    Next the ball nut assembly and bearing cap. Feels like good progress.

    Thanks.

    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    I decided to re-make the X bearing block. It was off sideways some 0.050" which may have worked. However, I also decided to drill a hole in the back of the saddle for the lead screw to extend through. If the first bearing block wasn't functional, or I decided to remake it later, the hole would be in the wrong place. That would require quite a bit of work to plug and re-drill. So a new block.

    It was machined as the first was. Here also I bored and reamed a 1/2" hole for the lead screw. This also allowed a length of 1/2" drill rod to locate the axis of the lead screw. A drill was mounted in the end of the drill rod and a hole drilled through the back of the saddle.

    PM1022 lathe CNC Conversion-drillsaddle-1-jpg

    PM1022 lathe CNC Conversion-drillsaddle-2-jpg

    I enlarged the hole to a clearance fit for the ball screw. That will positively keep the ball nut from running off the end.

    The half round block to mount the ball nut to the cross slide was machined. I mounted the ball nut to this block and machined both as a unit. That ball nut is HARD. I used a 3/8" carbide endmill and don't think I did it any good. But it hacked the material away slowly. I tried tape to keep chips out of the ball nut but wasn't happy with that. I finally put modeling clay on the ends to keep chips out. This worked better. Hopefully I didn't harm the ball nut before this revelation.

    PM1022 lathe CNC Conversion-ballnut-jpg

    I put the assembly together several times for measurements.

    PM1022 lathe CNC Conversion-assembly-1-jpg

    I finally ended up cutting as much as I dared off the ball nut and block. The number of threads for the screw holding it to the cross slide was down to about 3 and cuts were getting close to the screws holding the block in place. This wasn't quite enough to bring it level with the cross slide. I ended up cutting a pocket about 0.025" deep into the underside of the cross slide.

    PM1022 lathe CNC Conversion-saddlepocket-jpg

    Once these were aligned the fit was quite good. I blued up the ball nut block and marked through the cross slide screw. That gave a right-left orientation for the cross slide screw threaded hole. The fore-aft hole location came from the drawings. Here is the ball nut assembly installed in the saddle.

    PM1022 lathe CNC Conversion-ballnutinstalled-jpg

    You can see in this picture that the ball nut aligns well with the slot. Also that where is little room on either side, some 0.050". The hole, marked from the cross slide, isn't in the middle of the block or middle of the slot. It surprises me the alignment is off this far.

    Below is a picture of the bearing block with bearings and pulley installed. You can't see the bearings but they are in there. I'm amazed it fit together without having to adjust the spacers. I still need to cut the keyway slot in the pulley.

    PM1022 lathe CNC Conversion-bearingblock-jpg

    The motion is smooth end to end. Very happy about that. It doesn't seem to have any backlash, but I'm poor at checking a few thousands without an indicator. I'll get around to checking, and adjusting, if needed when complete.

    The cross slide will move forward, over the X bearing block, until it hits the bearing retainer on the front. The ball nut assembly hits the front of its slot about 1" before the cross slide hits the retainer. You can see in this picture, with the cross slide all the way back, where the slot ends.

    PM1022 lathe CNC Conversion-saddlegap-jpg

    I plan to cut this slot further forward about an inch to gain travel. That would put the X travel about where it was originally. I'll put some covers over this open slot to keep most chips away from the ball screw and nut. The solution that maxspongebob gave above in this thread looks like a good solution.

    I need to make the motor mount to bolt on the front. Besides that, and a few details, the X axis is complete. A very tight fit but I'm happy about how it's turning out.

    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    A little more progress. I was able to make the X motor mount for the NEMA 34 stepper. If you're doing a cnc lathe conversion you likely already have a cnc mill. If not I suggest you convert your mill before doing the lathe. I find a cnc mill more useful, in general, than a cnc lathe. As with this part, a cnc mill will help greatly in doing a cnc lathe conversion. Sadly, a cnc mill would also be a great help in doing a mill conversion.

    The mount was machined from a 4"x6" piece of 3/8" aluminum stock. I put this in a vice on the mill and drilled the holes for mounting to the bearing block. Also drilled and reamed a 1/4" hole for alignment. The counter bores were then done using a G-code program. A second program was used to cut the inner stepper mounting slots. I'm using CamBam to generate G-code from a 2D DXF drawing.

    PM1022 lathe CNC Conversion-x-motormount-1-jpg

    The part was flipped so the back could be machined. The part was located on the 1/4" hole and a 0.07" pocket machined for the stepper.

    PM1022 lathe CNC Conversion-x-motormount-2-jpg

    I flipped the part again and mounted to a piece of 3/4" plywood using wood screws. The holes for these screws were aligned to keep the part square. Also it was dialed in using a test indicator as the screws were tightened. Zero was again found using the 1/4” reamed hole. A G-code program cut the outside of the part, stepping down for roughing and one full depth cut of 0.005" to finish. The elongated hole for the stepper shaft and pulley was also cut. It also used a roughing step down with one finish pass.

    PM1022 lathe CNC Conversion-x-motormount-3-jpg

    The motor mount came out well, but not perfect. I used holding tabs on the outside and in the elongated hole. I forgot the stock was nearly final size so there was no need for tabs. It only added three stubs that needed to be filed away, as seen below. I also forgot there is a pocket from the other side, so the tabs on the elongated hole were cut in air. Thankfully the center of this hole didn't jam the tool and cause problems. Finally I put a chamfer around the outside. I did this on the fly, without a good drawing. I thought of not chamfering the top as it's a real close fit to the bearing cap. But I'm too lazy and didn't make another cam file. The 0.075" chamfer was a little heavy and cut real close to the upper C-bores. But it did knock off the outer sharp corners which is what was wanted. The faces were left alone. It’s not a show machine and the surface finish would be only visual, no problem. Trivial concerns, but something to remember next time around.

    PM1022 lathe CNC Conversion-x-motormount-4-jpg

    PM1022 lathe CNC Conversion-x-motormount-5-jpg

    Finally the X axis assembled.

    PM1022 lathe CNC Conversion-assembly-jpg

    I still need to put a keyway in the upper pulley. Also need to bore the lower pulley to fit the stepper. I may want to put larger pulleys here. They looked right on paper but seem small in the real world. The numbers say the stepper should skip steps before the belt breaks, but it does look small. We'll see.

    I'll have to put a hold on this project for awhile. Too much going on. Will pick it up in earnest in a few months.

    If anyone is following along, feedback is welcome.

    Thanks.

    Hugh Currin


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    Default Re: PM1022 lathe CNC Conversion

    I am following. Just one comment.

    When you install the pulley on the motor, with that bracket, will the pulley have a setscrew, and will you be able to tighten it? If the setscrew is on the inside next to the motor, the mounting plate may get in the way.

    Also, looks like a 3D printed cover would work well for that pulley. Do you have a 3D printer?



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    Default Re: PM1022 lathe CNC Conversion

    Quote Originally Posted by currinh View Post
    PM1022 lathe CNC Conversion-drillsaddle-1-jpg


    I absolutely love this drill. They don't make em like that anymore.



  19. #39

    Default Re: PM1022 lathe CNC Conversion

    I have a similar 1/2" drive drill. It's like 60 years old. There's a reason why they don't make them like it anymore, it's slow as sin. But I guess it's still going strong...



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    Default Re: PM1022 lathe CNC Conversion

    max:

    Thanks for coming along. The original thinking on that motor pulley was to fix it with set screws before mounting. The elongated hole was large enough for the 20T pulley to fit through. In design I discovered the the hub was too small to bore out on this 20T pulley. So I switched to a 30T, problem solved. But I just checked and found the 30T won't fit through. However, the 30T hub is still too small to bore out and still put set screws in. The current thinking is to drill through the pulley teeth for set screws. I think this'll work fine, there are more than enough teeth in contact. So yes it is a problem, good eye. :-)

    As I said the pulleys now look small. I may replace them with larger, but the problem you note is still there. If the hub was large enough I could use something like a Fenner Trantorque locking hub. I've had good luck with these and poor luck with set screws. They are real expensive, but It may be the final solution.

    I think you may be right about the 3D printed belt cover. I don't have a 3D printer but this sounds like an excellent justification to get one. Thank you.

    Quote Originally Posted by maxspongebob View Post
    I am following. Just one comment.

    When you install the pulley on the motor, with that bracket, will the pulley have a setscrew, and will you be able to tighten it? If the setscrew is on the inside next to the motor, the mounting plate may get in the way.

    Also, looks like a 3D printed cover would work well for that pulley. Do you have a 3D printer?


    Hugh Currin


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