New PM-25MV Mill

macardoso said:
I also wrestled with the mill size question. I purchased my G0704 from Grizzly when I was just starting out in the hobby and had outgrown my Sherline "mini mill" (micro). The machine out of the box was really quite nice, and I did eventually CNC it because it was a fun project. Today, (5 years later) I am feeling like I am just running out of space and power on the machine. I would love a larger machine (RF45 or larger) and will probably upgrade. That being said, I think it all about the kind of parts you want to make, how much you want to spend, and how capable you are to design your own CNC conversion (if you choose to do so).

I will say that the extra 1.5" of Y travel on the 727 would go a long way as that is where I am the most limited on the G0704. I rarely need the full 18" of travel in X. The 727 also weighs quite a bit more would would likely lead to better rigidity (the biggest issue with all <2000lb machines). In the end, you will have a great time with either machine, just understand everything will have its limitations.
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That really leans me towards 727 again. All good points as well. I would love CNC, but the expense! I wouldn’t even know what software to control it. It would have to be a premade kit as I don’t think I have the attention span to wing that over months. I have seen kits for $2500 and up, right now that sounds crazy, one day I know I’ll be chomping at that bit. Is the 727 just out of the question for CNC?
Thanks everyone for the help, my apologies if I hijacked this thread...
 
GunsOfNavarone said:
one day I know I’ll be chomping at that bit. Is the 727 just out of the question for CNC?
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So take anything I say with the understanding that I have done a few CNC conversions and feel pretty comfortable with the process. Basically all hobby CNC conversions are: design a few motor mounts/bearing blocks, machine ballscrews, hook up motors to control electronics, and plug into a PC. You can take it to any extreme that you want but you could probably do the whole thing for <$1000 on a budget. You will need some design abilities, machining capabilities (you can use your shiny new mill to make most of the parts, but if you need to modify the machine itself, then you need another tool), and comfort with basic wiring. The big question is, do you really need it? Many of the components I make actually could be done on a manual machine in less time than writing a program or jogging the machine. But there are certainly others which absolutely need CNC to be made.

My thoughts in short, think what kind of work you want to do on it (a manual machine is very capable by itself). If you want a CNC, and are comfortable designing and making your own conversion, either mill works fine. If you will enjoy the building of the CNC then it can be a ton of fun to do just that (and save money), but if you need to have a machine working as fast as possible, buying a kit accomplishes that.
 
You know, that brings up a really good question and I have been pondering for weeks.....haven't gotten up the nerve to ask yet. What if you need to mill something let's say 5/8" thick and let's say at one end it comes to a taper. That is, say the Y measurement is 3" but tapers down slowly, at a 4 5 degree angle to 1/2" along the Y. This requires the X and Y to be turned at a specific ratio to one another. How would you do this w/o CNC....this is why I KNOW I will need CNC....unless there is a common way to do this that I am unaware because.....well, I haven't learned that among many things right now.
 
GunsOfNavarone said:
How would you do this w/o CNC
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Use a swivel milling vise. Set the vise at 90* square, mill your one side, the loosen the vise, set to whatever degree your wedge requires, then cut the second side. Gets tricky, but there were probably a hundred years of people machining stuff w/o cnc.


The other way (if the part can’t be held in a vise) is to clamp it to your mill table with hold down clamps and use an indicator to set the angle. Basically you do some trig to say that over a distance of 4” you should have a change in Y of something. Use the handwheels and a test indicator to measure where you are at and tap it into alignment with a mallet. Tedious but perfectly doable.
 
Yeah, I thought that about life before CNC, the “old timers” probably did this without batting an eye. Your first technique sound doable, the 2nd sounds tricky as hell!
 
Nice conversion on the PM-25, your saga with the ball screws is similar to others posted experiences with the least expensive options. There are some reputable sources from China, usually a bit more cost but sometimes spending a bit more, one ends up with not having unusable products. What always is shocking to me is that you can buy these parts from China have them shipped to you for far less than just the cost of shipping it back to China if there is an issue. I am glad at least you got a refund. On some items, Chinese sellers just send you a new part because of the cost of returning the item. The positive side of buying through say eBay is at least you have some recourse if the product is defective or not as described. I pretty much have stopped buying anything direct from China because of the issues mentioned, along with long delivery times and very poor packing which often results damaged parts.

There needs to be some consideration if CNC conversion is a dream that it would be nice, vs. buying a mill with the intent to convert to CNC. Also the scope and type of work, along with the build budget. Almost every CNC conversion with smaller mills, individuals will mention that it would be nice to have more travel. When one looks at the machine footprint/floor space, once you build an enclosed cabinet, there might be 25% difference between what you would need for say a PM-25 vs. PM-932. Just mentioning this, because table travel becomes a significant factor. If your intent is to mill, then the PM-927MV would be a good choice with limited floor space, if your intent is to do a CNC conversion down the line, the PM-30MV would be my first choice due to the increased travel and 2Hp motor vs. the PM-25MV.
 
GunsOfNavarone said:
That really leans me towards 727 again. All good points as well. I would love CNC, but the expense! I wouldn’t even know what software to control it. It would have to be a premade kit as I don’t think I have the attention span to wing that over months. I have seen kits for $2500 and up, right now that sounds crazy, one day I know I’ll be chomping at that bit. Is the 727 just out of the question for CNC?
Thanks everyone for the help, my apologies if I hijacked this thread...
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Everything is a trade off, you just need to decide what you can live with trading away and what you really need. I have converted 2 machines to CNC and sort of built a CNC lathe from scratch (its mostly done, just back burnered for now) and you really can do it for as much or as little as you want. I don't think I would ever spend $2500 on a conversion kit, that just seems silly to me. Some motors, electronics, and ballscrews is really all you need to get it going. I typically upgrade along the way as is needed, but a lot of the cheap stuff I get at first has never needed to be upgraded. I prefer to make mounts just because they are so simple and easy to do.

The 727 is absolutely not out of the question for CNC. There were just a few specific things I wanted that the 727 would have been more difficult and expensive to accomplish. Mainly related to the spindle and spindle motor. I have no doubt that the 727 would make a fine CNC mill.

Also, you didn't hijack the thread. This is right on topic in my opinion.
 
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