Another PM-833TV thread!

M.T. Pockets

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I know there's already a number of posts and threads about the 833T and TV but I figured I would start one too. The plan for this thread though is not necessarily to talk about the mill itself, its to talk about getting it moved and setup for homegamers such as myself. From what I've found online most people that buy a mill this size will put it in their garage or pole barn using an engine hoist or something similar. My machine is going in my walkout basement and because of this I was originally put off by the size, weight, and 220v power requirement, and almost went with something smaller. So this thread is about the first steps of my journey with my new PM-833TV and will hopefully be some help to some other hobbyists out there that would like 800lbs of milling machine in their basement.

Day 0
I received my mill on a Friday afternoon from Holland freight. The guy that delivered it was very nice and helpful and I could tell he knew what he was doing because he didn't drive the truck into the powerlines in front of my house like a lot of people do. After unloading it off the truck, and with me pushing, he was kind enough to haul it up my driveway and set it down in my garage. I tipped him $20 for the help and being a good chap. I then uncrated the mill, checked for missing parts, and saw that all was good.

Day 1
I started the day early with a trip to the metal shop to pick up a couple more pieces of steel for the mill stand and a few 2x4s. There's no way I could take this thing down to my basement in one piece, so the plan was to build a makeshift gantry crane out of 2x4's and a tractor supply special chain hoist so I could move it in pieces. I don't necessarily recommend building a gantry crain out of scrap 2x4s unless you know what you're doing. I happen to have a PhD in mechanical engineering and did the calculations to make sure this thing wasn't going to collapse in on itself. I'm also a solid 200lbs and was doing pull-ups on the thing to test it first. Renting, or even buying, an engine hoist is probably a better option but I'm cheap.

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With the gantry crane built I started taking parts off the head to lighten it up and reduce the changes of breaking something. Removing the motor and some other parts made the head a lot lighter and it was fairly easy to remove. And by the way, Matt at Precision Matthews, if you're reading this, change the socket head screws that bolt the motor mount to the spindle casting to hex head cap screws. There's barely any room to get an allen wrench to fit in there without getting it stuck. With most of the things removed I then wrapped the head with a 3000lb tie strap and connected it to the chain hoist. After putting some tension on the chain with the hoist and then undoing all the bolts the head slid right off.

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I didnt get any pics of it but I dropped the head down onto plywood with the column mating face down. I then put some other wood around it that was screwed in place to help support it. After that, I secured and picked it up with my milwaukee hand truck and rolled it down the hill to one of the sliding doors of my walkout basement and in she went. I don't have a good way of weighing the head but if I had to guess I would say it was ~100 - 130lbs with the motor removed. While having a walkout makes this easier, I feel it still wouldn't be too difficult to do this with stairs. I would however want an appliance dolly rather than a generic one like I have. A second hand would also make it a bit easier.

With the head in the basement next up was the column. The column easily unbolts from the base with 4 large, I'm guess M12??? bolts and detaching the line from the one-shot oiler. To lift the column I used two tie straps around the z-axis saddle moved all the way in the top position. I used two 150lb straps for this, one on each side of the lead screw. Ideally I would rather have used much higher rated straps as I'm pretty sure this part weights more than 150lbs but I at least had two of them and wasn't moving it far. Once secured the column lifted up pretty easily and I set it down one some more plywood. I also noticed there was some copper shim stock between the column and base, I assume to do some tramming from the factory. Just as before, I secured it to my hand truck and went down the hill to my backyard and then in the basement. The column is substantially heavier than the head was, if I had to guess I would say 200 - 250lbs. Still movable by one person but if I was moving this thing down a basement stairway I would absolutely want an appliance dolly or a second set of hands.
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And thats as far as I got for Day 1. Tomorrow I'll be moving the table and then hopefully the base. After that, I need to built the stand it will sit on which will also have a few challenges.
 

7milesup

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I like the gantry crane idea. I had to chuckle though when I saw the casters under the crane. Shouldn't they be used under the mill stand? LOL

Congrats on the mill and nice job so far.
 

M.T. Pockets

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I had to chuckle though when I saw the casters under the crane. Shouldn't they be used under the mill stand? LOL
Yeah they will be eventually. I ordered specific casters from amazon for this but apparently their delivery has been delayed...
 

M.T. Pockets

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Day 3
I started working on the mill again bright and early this morning around 11am and by 2pm I had moved the rest of it into the basement. The first item of the day was to remove the table. I did this by using a 1/2in eye-bolt fastened to the center of the table. I used one of those flanged nuts for the T-slot in the table.

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Then came figuring out how to get the table off... I thought it would easily just slide right out like other mills I've worked on but not this one. The parts that the bearing blocks mount on to hit the lead screw nut when trying to slide the table off. I had to remove the gib first to allow the table to be lifted up a bit first before it would clear the lead screw nut and come out. BTW, my table probably had half a pound of cosmoline on it that I cleaned off first. One off, I tilted it sideways on some wood and on the hand cart it went to the basement.

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Next was the scariest part of this entire process, lifting the base. PM gives you 4 eye-bolts to lift the base with which are grade 8 which is nice. Whats not nice is that they fasten from the sides and not the top which I don't understand. For those that don't know, you should NEVER use eye-bolts at a 90° angle like this (although I did). Eye-bolts are meant to be used in tension, maybe with a ~30° angle on them but thats it, they should never have large bending moments placed on them. Anyways... I used two of the eye-bolts to lift the base vertically and placed it on the hand truck, saddle facing the driver. I used lots of wood on this one and taped it around the ways to make sure not to damage and precision surfaces. I didn't get any other pics of this part as my but was pretty puckered.

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Moving the base to the basement was pretty easy, not even as bad as the column. If you needed to move this part down stairs with a hand truck, like the other parts it would be very doable with one person.

And that was it, everything was in the basement by 2pm. Then literally about 3 minutes after I finished everything my casters for the gantry crane were delivered.

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Typical amazon... but I guess I can't blame them they're probably backed up delivering pallets of toilet paper to everyone. I still bolted the casters on to the gantry just to try them and they are very nice! The thing rolls a lot easier and smoother than the leveling casters I had on there before. I've come to really like this gantry crane and I think I'll keep it around for a little while before I take it apart and turn it into shelves.

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Thats about it for day 3. I spent the rest of the day taking my power sander to mill scale on steel square tubing for the machine stand. Hopefully I'll get to cutting and welding after work tomorrow.
 

M.T. Pockets

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I started making the frame today. Got as far as tacking a big rectangle together. I sure wish I had a bigger fixture table.
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M.T. Pockets

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Continuing work on the frame, heres some pics!

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I used the gantry crane to save my back when moving the thing around.

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M.T. Pockets

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Its been a busy past couple days during the quarantine. My state has issued a shelter in place order so its left me lots of time to stay at home and work on projects. Tuesday after work I start putting the mill on the frame, including wiping off all the shmoo and adjusting everything. I have a big I-beam that runs along my basement ceiling with a beam trolley and a chain hoist attached to it. This makes lifting heavy stuff a breeze if I can get it under the beam.

First part of setting up the mill was putting the base on the freshly painted frame. After drilling the holes and bolting the base down with some 5/16 x 7in bolts, I found that I need to shim one of the corners by 0.024in to get it proper and level. I also left one of the bolts just a little snug instead of torquing it down all the way as to not distort the y-axis ways.
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Next up was the table which went on fairly easily. I found that for the y and x axes, the gibs were way way out of adjustment from the factory. The gibs also don't seem to have that much angle on them, at least now what I'm used to seeing, and need quite a bit of adjustment to get them set proper.

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I then spent a good half hour cleaning most of the cosmoline shmoo off the column before hoisting it onto the base. I cleaned the shmoo off with denatured alcohol and then covered the parts with a thin coat of Mobile 1. I also spent a good amount of time cleaning and scrubbing the base and bottom of the column so they wouldn't have any paint or dirt between them. When taking the mill apart I noticed there was a ton of junk between the two parts which would make the column a nightmare to tram.

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Before putting the spindle on I trammed out the column kinda quick and dirty using some 123 blocks bolted to the table. I figured it would be easier without the spindle and as I later learned I was right. I needed about 3 thou of shimming on the front of the column and about 8 thou on the right side. That got me to within a half a thou in each axis over the 3in distance of a block which is good enough for what I'm doing. It was also at this point that I became a bit disappointed with the z-axis. As with the other axes, the z-axis gibs were way off and needed very large amount of adjustment. I also found that the tolerances between the z-axis saddle and ways were pretty sloppy. I could physically twist and tilt the z-axis saddle and produce about 5 thou of movement on the DI as its setup in the picture, and this was after setting the gibs. I've got the gib set rather tight so I'm hoping it wears in a bit and I can remove some of this slop down the road. I know this isn't a high dollar machine but I was hoping for a bit more.

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Next was putting the spindle back on and tramming it, this was painful... I normally will tram the x-axis first and then the y but I quickly found thats not possible on this machine. The weight of the spindle cants the z-axis saddle quite a bit and of then of course causes the spindle to be pitched forward. Again this was after adjusting the z-axis gib and making it tight. I used two 5 thou shims at about 5 and 7 o'clock between the spindle and saddle to make sure I had a good sized triangle. The spindle is still pitched forward a tad but I'll fix it later when I need to face mill something.

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M.T. Pockets

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Now for this next part, any of you electricians or people with OCD will want to look away. To power this machine, I wasn't able to run a new 220V circuit in my basement as my electrical box is almost maxed with my solar panels, car charger, and all my other hippie stuff. However, it just so happens that I have a 220V 60amp outlet in my kitchen for installing an electric stove. And it just so happens that I have a gas stove. And it just so happens that what ever numb-nuts electrician that wired this outlet drilled their first hole in the wrong place, so there's a random hole in the floor next to said outlet. And it just so happens that directly underneath this hole is the location that I wanted to put the mill. Its like it was meant to be!

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Sometimes my genius even amazes myself.

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After that, I flipped the breaker back on and its alive!

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At this point I was rather tired and sick of working on this thing but I wanted to try making some chips before calling it quits. I don't have my hold down set yet, you know because of covid-19, so I drilled a hole in a piece of aluminum and bolted it to the table. About 1400rpms and a quick pass later, first chips!

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I'll be back at it after work tomorrow. Next steps are to wire in a power switch so I don't have to use the breaker to turn it off and to make some hold downs for the vice.
 

M.T. Pockets

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Yesterday I added a power switch to the VFD control box. Its a simple 250V 16A switch I had sitting around that fit the bill nicely, it breaks both neutral and hot for power leads.

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I also started making some hold downs for my toolmakers vice that I bought 2 years ago but never used. Got both the hold downs made, now just need to make some T-nuts and we'll be in business.

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While playing with the mill I noticed that at higher RPMs it got really loud, and I don't like loud things. It wasn't the motor or the spindle making the noise, it was the fan, so I got rid of it.

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Upon closer inspection its a straight blade fan thats meant to work in both directions, which makes sense, but also makes it a lot more loud due to vortices and etc. I doubt the motor really needs the fan for this type of application and I'll just remember to keep an eye on the motor temp.

I also made the chip tray out of some dead tree flesh. I made the tray really big and wide cause I like my chip trays how I like my butts. I did a flood coat of polyurethane on it to help stop if from absorbing oil and coolant.

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parshal

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That fan is pretty loud. Without the spindle cover on top and in a cold shop the fan output is darned cold.

Good job so far!
 

M.T. Pockets

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Just about done with setting up the mill. I got the face plate bolted back on, its in its final location in the shop, just need to button a few more things up. Today I took about 1/2in off the draw bar because its way to long. Was a bit of the pain setting it up in the lathe since the hex head is bigger than my lathes bore.

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Playing around with the mill some more I measured about 0.001" to 0.002" of run out in the spindle depending on which collet I used and I think thats pretty good for this type of machine. I also ran some passes with a 2in face mill and was rather surprised by the results. The picture is with a pass taking 0.010" DOC and I'm getting rainbow surfaces that are silky smooth to the touch, a lot better than I was hoping for. I've used 2,000lb knee mills that couldn't give me results like this. And yes, I know my spindle tram is off.

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So with all the inspections and playing done I started on my first part with the mill! This is a control panel for a telescope I've been building that I've been waiting for about 6 months to make. Its too big to cut on my CNC mill so I've been waiting to get this one in finish it. It's been so long since I ran a manual machine I forgot how nice it is just to turn some handles and not have to deal with software, looking at g-code, or push a bunch of buttons just to make a simple cut.

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I've only got a couple ops done on the first part with this machine but so far I'm very happy with it. Its exceeded my expectations in most ways, although fallen a bit short in others. Overall I'm actually a little surprised at how capable it really is. I'd say its performance is closer to the old bridgeports I used in uni and a lot more capable than the other mill/drill imports I've used in the past.

Next steps will be to add a DRO and a x-axis power feed. I ordered one of the cheap import DRO's with an LCD screen off of amazon today from a US distributor so we'll see if that arrives within a month with everything going on. I don't have high hopes for the reader and if the scales work OK I'll probably throw something together with one of those touchDRO kits. Until then, its counting dials turns for me.
 

Ed W

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So for the “$64 question”: how well does it cut at low speeds, say under 100 rpm?


Sent from my iPhone using Tapatalk
 

parshal

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So far I've only cut aluminum on mine and the only thing I've done at low speed is tapping. That's at 50 RPM, the slowest speed possible. I've managed to break a couple by speeding it up. But, to your point, I've had the spindle stop dead tapping at 50 RPM a couple times.
 

M.T. Pockets

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I haven't tried anything under 100rpm yet. There isn't much I do at that low of speed and prefer to hand tap my parts. At a few hundred rpm where I've done some face milling and drilled some 0.75in holes its done just fine. If low end torque does become a problem Ill replace the spindle motor with a servo motor or something and gear down the belt more but so far no issues.
 

M.T. Pockets

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Well the YIHAO-GO DRO finally came in. This is one of the many cheap chinese one offs of amazon and so far its not as terrible as I was expecting. The installation was a bit of a pain but its on there and doesn't look like its gonna fall off.

For the x axis I put the scale behind the table as I eventually plan to add a power feed and want to be able to add the switches for that to the front. I made a simple bracket out of some 3/4 Al angle and used the screws for the way covers to mount the slider.
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The z axis was fairly straight forward. Drill some holes, tap some holes, align the scale, tighten the screws to the scale, done.
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The y axis was a PITA. The geometry of the base and saddle does not make it easy to mount the scale, at least not if you want the slider pointing down. I fabricobbled a bracket and some standoffs that I mounted to the back of the saddle which then connects to one of the brackets that came in the kit. Since the base has a draft on it I had to bend an angle into the L bracket to get everything to be parallel. I then used some aluminum shim washers to get everything lined up correctly. It took about two solid evenings to get this done and working right.
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While fitting the scales I also mounted a collet holder I 3D printed. A bit unusual looking but I think it came out pretty nice. Its doesn't look like it in the picture but z axis fixing knob thing is not in the way of removing the collets.
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Then came along mounting the DRO reader. This was pretty easy, hardest part was just making sure it was in a spot that wouldn't get in the way of the z-axis crank or quill handle. I opted to spend the extra $20 to get the LCD screen instead of the standard segment displays. The last time I used a DRO it was an Acu-rite VUE and before that an Acu-rite Millpwr and yeah, this is a pretty big step down in every way. I'm not planning on making any money with this machine so this will be good enough for now. I bought the entire DRO kit with scales for less than the price of a single Acu-rite scale so I can't really complain.
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And here it is all said and done. I tested each of the axes against a dial indicator on a magnetic base and then quickly realized why you're not supposed to do things like this for non-relative positioning. I then stuck the DI in the vice to evaluate the accuracy of the z axis, it was spot on over 0.9in. I then compared the x axis and y axis scales to the screws and dials of the mill. If you believe the machine dials (which I'm not entirely sure I do) then each axis has an error of about 1-2 thou over 10in. This isn't great but I didn't exactly pay for Acu-rite or Renishaw scales here and this kind of accuracy is good enough for the casual hobbyist. You can adjust the linear error in the YH800-3 Counter if you dare. I'll test them later against some Mitutoyo calipers which I do trust and see how they do.
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I still need to route and clean up the cables which I'll probably do this weekend.
 

M.T. Pockets

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A bit off topic, the crate the mill shipped in was made out of a surprising large amount of wood. I'm a hippie and hate wasting material so I turned the wood from the shipping crate into some planter boxes that I'm going to grow some squash in. If nothing else it at least let me practice my skills for the upcoming apocalypse. I was even able to re-use a lot of the nails that were used in the crate.

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7milesup

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There is probably some sort of chemical in that wood, coming from Taiwan and all which will kill you when you eat the squash. Or not.
 

M.T. Pockets

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I'm about 5 parts in on this mill and I'm realizing the spindle lock issue people are having. I too kept on having end mills get pulled and drill bits spin in their collets because I couldn't tighten the drawbar enough. I 3D printed this spindle wrench to help tighten the drawbar and it works fairly well. Its just a prototype for now, I'll eventually make one out of aluminum or stainless. Solidworks file attached for anyone that wants to make their own.

FYI, the ID is slightly larger than the 23mm it should be. This is to make room for the hex head of the drawbar.

spindle wrench.png

My other major challenge that I'm going to give some attention to is backlash. Its not terrible, better than other Taiwan made machines I've used **cough** "JET" **cough**, but I still want it better. I'm too cheap for ballscrews so I'll need to find another alternative. I'm able to keep backlash at 2-3 thou on my Taig, maybe I'll look into copying that.
 

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7milesup

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So do you use this wrench with the mill in low range. It has been strong enough? I have ABS and Taulman Nylon. What did you use?
 

M.T. Pockets

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My mill doesn't have a low range, its got the belt and pulleys. So far yes, its been strong enough. I made it out of some PLA I had laying around and used some thick walls and 25% infill on the print. I don't expect it to last forever, just to prove that the geometry works.
 

7milesup

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Oooops. Yes, forgot about your belt drive.
It will work good on mine then. Thank you.
 

Kiwi Canuck

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MT Pockets, nice work on getting your new mill setup and the DRO install looks good.

I noticed that you have the red shipping spacers still installed between the read head and the scale in your photos, did you remove them or leave them in?

Also why is backlash an issue now that you have a DRO installed?

David.
 

M.T. Pockets

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Thanks Kiwi, I left the spacers in as the manufacture describes them as "wipers". Didn't think it would hurt to leave them on.

The backlash isn't an issue with the DRO, its always been an issue, mainly because I want to do climb milling without breaking stuff. I haven't messed with the leadscrew nuts yet so that will be step one.
 
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mksj

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I do climb cutting quite a bit, never seemed to be an issue to have a few thousandth of play which is pretty much the norm even for a new machine. Ball screws can get away from you with climb cutting, ok for CNC but not so much for manual. Also a function of your gibs. Nice build on the stand/install.
 

M.T. Pockets

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Thanks mksj. For the backlash, we're not talking a few thou here, were talking about 10-15 thou in the x and y. Way more than there should be and I've had a 1/2 end mill already grab a few times. I'd like to get it down to a few thou like I have on my Taig which I think is doable, just needs some tuning. I agree about the ballscrews, I don't want them on a manual machine. Worst case is I buy pre-loaded lead screw nuts but that probably wont be necessary.
 

M.T. Pockets

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It took a few hours but I got the backlash fixed, or at least better. I was originally measuring about 10 thou on the x axis and about 15 on y. After a lot of measuring and fiddling I found it was due to a combination of preload on the lead screw bearings and backlash in the brass split nuts.

As shown in the picture below, the preload on the bearings comes from the #70 screw, there's no separate nut for it. After torquing the x and y handle screws to about 15 ft-lbs, using my calibrated arm, the backlash from the bearings came down to about 0.5 thou. I also noticed that these don't appear to be angular contact bearings, just regular radial bearings. After adding the preload the bearings feel a bit gritty and I don't think they will last all that long. If/when they do fail I'll try to replace them with some angular contact bearings.

Capture.JPG

The other large source of backlash was the split nuts. They both needed to be tightened a pretty good amount. I didn't need to tighten them all the way but they're not that far from it. They're made from casted brass (which isn't a bad thing, these are cheaper to replace than lead screws) so not sure how long they will last before needing to be tightened again. These will probably eventually get replaced too.

After making all the adjustments I'm down to about 2-3 thou for both the x and y and the table feels a lot less loosy goosy, although a bit gritty because these radial bearings aren't meant for axial load. I'm going to cut some mild steel on it this weekend and we'll see how she handles climb milling now.
 
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