Another PM-833TV thread!

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


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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.
 
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.
 
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.
 
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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