# Pm25mv Or Rf-45 Clone?



## thinaire (Apr 23, 2015)

PM25MV or RF-45 Clone?

As I'm sure most are aware at $1600 the PM25MV comes very close to the price of several RF-45 clones on the market. Although I would like PM932, I am looking for a CNC base machine and don't want to pay $500 extra for power assist parts I'm going to put on the shelf.

For me this will be a hobby machine. I am planing work on small parts like multi-tool/pocket knife mods, RC parts and bicycle parts.  I am not planning automotive engine parts but maybe a bracket here and there. I do want to mill small aluminum, stainless and titanium pieces. Speed is not a primary concern unless it will take a factor of 10x longer  to complete something on the PM25. I am thinking that my one off projects will take a lot more time planning and setting up that actually milling. 

I see the PM25MV as the plush option.  Quiet belt drive ( I will use it in a basement under bedrooms ) High torque brushless motor,  Dial in Variable speed.  Also the light weight could be helpful during the CNC conversion and with other tweaks and maintenance. A three year warranty would be great and I am alway reading good things about Quality Machine Tools.

The 45 sized mills have power, mass and rigidity on their side.

So given all that, when working on small projects with harder metals to mill like above, does a larger mill still offer added benefit? If so how?


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## darkzero (Apr 23, 2015)

Mass is a factor of rigidity. Harder materials require rigidity unless you don't mind taking numerous shallow cuts. Chatter is a big concern here. The PM25MV seems to be the easier & cheaper machine to do a CNC conversion but I would rather take the time to convert a RF-45 style mill.

I'm not a CNC guy (yet) but when I was in the market for a mill for conventional use, I did not want a mill smaller than a RF-45. I knew I would not be happy with anything smaller. It was well worth the extra time I needed to gather funds & already I want a full size knee mill now.

Not sure how Matt handles his warranty but if you do a CNC conversion, I would think that would void the warranty so it doesn't matter how long the warranty period is.


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## brav65 (Apr 23, 2015)

I have the PM-25MV and am extremely happy with it. I think you have defined the benefits and shortcomings of the two mills very well. Ultimately I think it comes down to money. If you can afford the lager mill go for it. I don't think there are many people who look back and say that they wish they had purchased a smaller mill. On the other hand  Matt has done a great job fixing some of the shortcomings of thePM-25's. With the latest batch he includes the three bolt modification which is one less thing to have to take care of.   In addition there is tons of information out there about converting to CNC.


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## compsurge (Apr 23, 2015)

I'd go for the RF-45. As Brooks has said, the PM-25 is a fine machine and will definitely suit you as a hobbyist. If you want to use CNC, you can run the machine faster than with the hand cranks. The lack of rigidity in the smaller machines will become apparent and be a limiting factor of the machine feed rate. I would also consider the G0704 and a high speed belt drive upgrade (6000 vs 2500 rpm) if going CNC. The cost of CNC conversion components between the PM-25 and an RF-45/IH machine is negligible. Ball screws are cheap and the electronics will be the same for either.

I have a Weiss 30 (PM-30MV-L) and I find it could use more rigidity, but most of my concern comes from the flimsy sheet metal stand (steel box tube stand project slated for next month). There may be an epoxy granite cavity-filling in my future as well.


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## thinaire (Apr 23, 2015)

Thanks Gents for your advise.

The warranty point was the one that surprised me the most. I can't remember any CNC conversions bringing up voiding of the warranty. Almost anything one buys is this way. Just the same, I am a tinkerer and I mod a lot of products with forum type instruction. I have found that  most non milling groups bring this up in the first or second post unless it is a product that encourages mods.

Brooks is also right about money. I can't say for sure if money was not a question that I would still DIY CNC the mill or just buy Tormach or HAAS. In this case the dollar cost between the two mills is within a two or three hundred dollars That's not chump change but doable for me. But I don't feel like I am comparing apples to apples either.   The real cost for me is going back to noisy slow geared drive that tends to break if you crash.


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## brav65 (Apr 24, 2015)

I would also check with Matt regarding the warranty. He is a a stand up guy and would probably stand behind his product of there was an issue unrelated to the CNC conversion.  Fortunately most of the parts are relatively inexpensive as compared to buying a whole new machine.  So even if you were forced to buy the parts your exposure is not too great.  

On the noise front, the PM-25 is very quiet. I'm can have a phone conversation with the mill on and the person on the other end can't hear the mill running.  You also have the ability to change/upgrade the motor with little effort. Mill a new motor bracket and maybe change a pulley and you are up and running.


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## compsurge (Apr 24, 2015)

When I bought my PM-30, I asked Matt if the mill would be covered if I had converted it to CNC. He said any of the parts originally on the mill are covered by the warranty, so the motor, gearbox, etc. would all be covered. Matt has sourced good parts for his machines and they are made a little better as well. This is why there is a premium on his machines versus others.

I do not think you will break the gearbox in a crash. On a G0704, you may break the plastic gear, but that is a GOOD thing as it is the weak link in the system and prevents cascading damage. It's also a cheap replacement part if I remember correctly.

My PM-30 is gear drive and it is relatively quiet as well (I also have partial hearing loss, so maybe not!). Most noise is from the machining.

Anyway, buy what is in your budget and make things with it. This is key - as long as you're able to make the things you want with your machine, you will be satisfied. For what you have described, I would venture to say the PM-25 will be just fine with a CNC conversion (even using the factory leadscrews at a low feed rate).

Definitely look into a better stand though. The machine really should not move when performing rapids.

You can always put some epoxy granite/aggregage in the base to add some mass and help dampening.


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## GA Gyro (Apr 25, 2015)

darkzero said:


> Mass is a factor of rigidity. Harder materials require rigidity unless you don't mind taking numerous shallow cuts. Chatter is a big concern here. The PM25MV seems to be the easier & cheaper machine to do a CNC conversion but I would rather take the time to convert a RF-45 style mill.
> 
> I'm not a CNC guy (yet) but when I was in the market for a mill for conventional use, I did not want a mill smaller than a RF-45. I knew I would not be happy with anything smaller. It was well worth the extra time I needed to gather funds & already I want a full size knee mill now.
> 
> Not sure how Matt handles his warranty but if you do a CNC conversion, I would think that would void the warranty so it doesn't matter how long the warranty period is.



I opted for a 935, a knee mill... so I do not have any experience with either of the bed mills.

If it were me, I would think on the issue of rigidity, especially in a CNC application.  All that cast iron mass, is what keeps the machine accurate, and in CNC applications, one tends to push the machine more than in hand applications.  If it were me... I would get a 932 or Matt's new 940 (basically a 932 with more Y travel and a beefier frame).
Most of the folks I have read... after a few years, want a larger machine... and the beef is the major issue.


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## wrmiller (Apr 25, 2015)

Iron isn't a very hard material (it is classified as a metal because of it's conductivity?), and one of the main reasons it dampens vibrations is that it ISN'T very rigid (ever hear of semi-solid iron?). Very strong/rigid metals transmit frequencies (vibrations) with much less loss of amplitude/signal strength than less rigid materials. That's one of the main reasons epoxy/quartz mixes are so great at dampening vibrations. Semi-viscous.

Iron has been around for thousands of years and is (relatively) easy to work with. It can be cast into all kinds of shapes. In order to get some semblance of rigidity out of iron you need a crap-load of it (which is why some people think there is a direct corollary between mass and rigidity. But it isn't a direct corollary. Not even close.

In an ideal scenario you would want the most rigid/hardest materials right at the cutter/material interface to draw the vibrations/frequencies away from said interface only to be dampened or removed further away in a different type of material. Uber high-strength steel or what-not for hyper accuracy surrounded by an epoxy-granite substrate for frequency dampening? This might work, but I don't know where I could buy something like this. Or if I could afford it. 

Sorry for the rant. I just get tired of hearing how great iron is when it's just a cheap, readily available, half-arsed solution that's been around since before the Romans...   (bill is now slinking off back into his corner...)


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## JayBob (Apr 25, 2015)

Technically, it's been around for much longer than that.....man just didn't know about it.


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## T Bredehoft (Apr 25, 2015)

_man just didn't know about it_

along with time travel, among other things. 

Tom


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## wrmiller (Apr 25, 2015)

Ok, million of thousands of years. I stand corrected.


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## GA Gyro (Apr 25, 2015)

wrmiller19 said:


> Iron isn't a very hard material (it is classified as a metal because of it's conductivity?), and one of the main reasons it dampens vibrations is that it ISN'T very rigid (ever hear of semi-solid iron?). Very strong/rigid metals transmit frequencies (vibrations) with much less loss of amplitude/signal strength than less rigid materials. That's one of the main reasons epoxy/quartz mixes are so great at dampening vibrations. Semi-viscous.
> 
> Iron has been around for thousands of years and is (relatively) easy to work with. It can be cast into all kinds of shapes. In order to get some semblance of rigidity out of iron you need a crap-load of it (which is why some people think there is a direct corollary between mass and rigidity. But it isn't a direct corollary. Not even close.
> 
> ...


 
I totally agree Bill... Iron is a 'traditional' method of building things... including machine tools.
Seems to me (correct me if I am wrong)... at the level of things us hobby shop owners can afford... a beefy iron frame is the easier way to increase the amount of rough cut, and the potential accuracy, of a machine tool.  Observation would suggest this has been going on for longer than many of our grandparents were alive.  

Back on subject:  If it were me... I would look more seriously at the 932 or 940.


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## GA Gyro (Apr 25, 2015)

Raises the question of whether we were talking about iron in a usable form, or a natural form. 

I could have dozens of kilo's of gold in the dirt under my home... however if it is in the form of 5-6 gr/ton of raw dirt... it is basically worthless to me.  (derned)


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## compsurge (Apr 25, 2015)

One of the things with the new PM-940 is the hardened ways option. That sounds pretty enticing. Also a cost-adder.


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## thinaire (Apr 25, 2015)

Has anyone seen the video on Youtube where a gentleman mounts the Column of his BF30 to a solid wall to dampen the vibration.  This is something I could do in my basement.   What are your thoughts on this?


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## compsurge (Apr 25, 2015)

I was always curious how much of his movement was due to the flimsy sheet metal cabinet.


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## T Bredehoft (Apr 25, 2015)

My PM25 is going to be installed on work bench, a used kitchen counter, with 2x4 frame underneath, double thick top, two layers of Formica and Particle Board. Counter top secured to the wall behind it._ As soon as it gets here!
_
Tom


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## compsurge (Apr 25, 2015)

Come on now, you need to put it on the stand it comes with first so that you have a data point to compare


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## T Bredehoft (Apr 25, 2015)

There's no room in my 'shop' for a stand.  I gotta walk sideways to use my band saws now.


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