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Buying a PM932

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ThunderDog

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#1
Hi all,

I think I'm going to pull the trigger for a PM932 tomorrow, after having just sold my Atlas mill and my Jefferson mill over the past two days. Money dictates alot of my choices at the moment. So, I'm going to go with the 932BASIC. Long-term projection is to buy a 2 axis DRO or dive deep into CNC conversion land as I've read a few of the long threads regarding the conversion.
Like anyone else in this hobby the "need" for more tooling, features, options, etc. is alive and well in my house. I've read somewhere that shipping won't go up if I add in the vise and other tooling. I hope that to still be the case. Regardless, I'm also going to add the 5" vise with swivel. But, I do have a few questions regarding other tooling.
PM offers an 11 piece collet set, however I'm currently seeing 13 piece collet sets with free shipping from US sellers for $10 cheaper on the 'ole eBay. The same can be said for the drill chuck, but in this case almost half the cost. Have many followed this same approach of tooling up from eBay opposed to PM's accessories? Is there a significant quality difference between the PM chucks and collets? Or, do you think it's simply that piece of mind knowing that PM has "screened" all of their inventory before selling? Please do NOT misunderstand this to mean that I am against PM's prices. I've only ever heard great things about the customer service and dedication to their customers.
 
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Ray C

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#2
The quality of the stock add-on components is about the same as the generic equipment from Shars. Aside from that, a couple things come to mind... As time goes, you'll probably desire to own multiple sets of collets and drill chucks. I have 3 drill chucks for the mill and 4 for the lathe. On the mill, one is setup with just a center bit. Another is a keyless used for drill bits in the standard-shank index size range. The last is a basic keyed chuck used for Silver/Demming shanks that have the three flats. If you spin-out a large drill bit, it's often the end of that chuck. As for collets, I have a basic set of R8 and an ER32 set. Economics... I understand that economics is always an important consideration but, a $10 price difference in something compared to the overall cost $2000+ for the machine... Is it really worth the hassle of ordering from multiple sources?

Anyhow... I hope you're considering the basic set of hold-down clamps because life without them is not a fun thing -and its even worse when you order the wrong size from a place on eBay.

Ray
 

ThunderDog

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The quality of the stock add-on components is about the same as the generic equipment from Shars. Aside from that, a couple things come to mind... As time goes, you'll probably desire to own multiple sets of collets and drill chucks. I have 3 drill chucks for the mill and 4 for the lathe. On the mill, one is setup with just a center bit. Another is a keyless used for drill bits in the standard-shank index size range. The last is a basic keyed chuck used for Silver/Demming shanks that have the three flats. If you spin-out a large drill bit, it's often the end of that chuck. As for collets, I have a basic set of R8 and an ER32 set. Economics... I understand that economics is always an important consideration but, a $10 price difference in something compared to the overall cost $2000+ for the machine... Is it really worth the hassle of ordering from multiple sources?

Anyhow... I hope you're considering the basic set of hold-down clamps because life without them is not a fun thing -and its even worse when you order the wrong size from a place on eBay.

Ray
Appreciate the feedback.

I thought the same thing regarding $10 until I saw the drill chuck for $40 vs $120. I have a set of hold-down clamps but the T-nuts were modded to fit my old Atlas mill. That is unfortunate, but something I'll have to buy.
I have a problem, sometimes I need a crowbar to open my wallet.:grin:
 

navav2002

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#4
For SAFETY reasons I don't recommend skimping on "work holding" devices ie: vise, clamping kit or anything related to holding your work piece.

Congrats on your new mill!!
 
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Muskt

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#5
I have a 932PDF. I've had it for about 3 years. Overall pretty satisfied with it. I have a real Albrecht chuck for it and cannot say anything bad about it. I got it on EBay for about $100. I use ER32 colletts from MariTool. I have found them to be pretty good and not terribly expensive. I have the supplied 4 inch vise. The swivel base has never been installed--not once. I would like a bigger and better vise; however, other things always seem to have a higher priority. I attached 4 leds from Walmart to a ring near the spindle--big improvement in visibility. The clamp kit is adequate; but the T-Nuts are a bit looser than I like--not dangerously loose, just not a nice fit. I have recently noticed a small amount of oil seepage--haven't investigated the source, yet. Does not appear to be from the spindle--need to check that out.

Now for a slightly different story. Yesterday, while at the local metal/scrap yard, I noticed a "pile" of milling cutters & lathe tool bits lying on the ground in the mud. I investigated. No Carbide--all HSS. Most of the end mills were a bit rusty, but not the lathe tools--HMMMMM.
Looked to be only surface rust--if that. I asked the owner what he wanted for the "stuff". He said $5 per pound. Well, $34 later, I'm on the way home. Soaked the end mills in EvapoRust for about 6 hours & wiped 99% of the rust off. No pitting, & no dings. Many of them had that waxy protective stuff on them. All are regrinds. One or two are questionable, but most look good as new. I think I ended up with 5-6 1/2 inch, 3 3/4, 2-3 5/8, 1 1inch, & a couple of 9/16. There are a couple that must have been extremely special. The lathe tool bits are 1/2, 5/8, & 3/4. Mostly 4-5 inches long. A couple are MoMax Cobalt. I may have to go back soon.

Best to you with the new mill. I enjoy the heck out of mine.

Jerry in Delaware
 

Bob Korves

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38Bill

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The one thing I wished I had purchased right away with my PM932 was the 2 axis DRO. I ended up adding one within 6 months and I love it.
 

navav2002

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#8
One thing I remembered when I bought my mill is that it didn't come with a spline wrench...Maybe they have changed that by now but if not here is a link to the one I got:
Luminar Spline Wrench

I couldn't live without my x-axis power feed!! I hope to be adding a DRO soon, I think I'm going with the PM 3 axis..

Good thing you can add a piece at a time or I couldn't afford any of it!!
 
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38Bill

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I couldn't live without my x-axis power feed!! I hope to be adding a DRO soon, I think I'm going with the PM 3 axis..

Good thing you can add a piece at a time or I couldn't afford any of it!!
I purchased my mill with the power feed and I use it all the time. Makes working much easier and it seems to give me a better finish too.
 

ThunderDog

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#10
The one thing I wished I had purchased right away with my PM932 was the 2 axis DRO. I ended up adding one within 6 months and I love it.
I have a feeling I'm going to end up like this.
 
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umahunter

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#11
I just got mine a lil while back and mine came with this 1/2 inch drill chuck it's not the best but it'll work till I can buy a more precision chuck 20180331_001335.jpg
 
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umahunter

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#12
Their online manual says it comes with a facemill but it only comes with an arbor pm said they stopped getting them because they were junk
 

ThunderDog

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#13
Hi again,

Didn't get a chance to order mine last week, general life/dad/spouse responsibilities took center stage.

While I'm here I have to ask, what is the expected depth of cut on say mild steel? Let's assume .5 end mill. I know other factors can contribute to an exact answer, but one of the big reasons for moving on from the little Atlas mill and Jefferson mill was due to the very light cuts that I was forced into making with those two machines. And honestly those light cuts drove me bananas, not counting the super small work tables.

I've searched around and seem to only find results related to this machine for cutting aluminum. For whatever reason, all of my projects seem to revolve around steel.
 

stioc

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#14
OK, I'm going to offer just a quick opinion from my point of view- after recently converting my RF30 mill to CNC.

CNC is fun and addicting, and for most of us the affordability is always a big factor. Nowadays it can be done pretty inexpensively (I detailed my $500 cnc conversion here somewhere). I love it, it was well within my comfort zone of if I screw it up I'm not out a lot of money, if I don't like it or find it difficult again I'm not out a lot of money etc. However, having done it, it's very addicting because you have a lot to learn and you can now build things that are almost impossible to do by hand. So I'm pretty happy with converting my old RF30.

However, now I'm starting to realize all the short comings of a DIY solution too. It's not just about turning motors through CNC but also all the other things- ballscrews, a better VFD spindle motor that can turn at high speeds, a coolant system, an enclosure and then future upgrade-ability to automatic tool changers and such.

If all you can comfortably afford is a DIY conversion go for it but if you can afford a real cnc machine like a Tormach I'd say you'll buy quality once, cry once. Also, consider the cost of the mill and the conversion against the cost of a Tormach say a 770 that you can start with now and then add the gee-whiz parts to it later on. I'd think you might not be too far off?

As I said before, all I could afford comfortably for this hobby (I have several others :() was the conversion and I have no regrets for the bang for the buck (since I already owned the mill). I just wish I had all the features I mentioned or at least the ability to add them as I progress - which may not seem important now but they will be as you really get into it.
 

wrmiller

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#15
Hi again,

Didn't get a chance to order mine last week, general life/dad/spouse responsibilities took center stage.

While I'm here I have to ask, what is the expected depth of cut on say mild steel? Let's assume .5 end mill. I know other factors can contribute to an exact answer, but one of the big reasons for moving on from the little Atlas mill and Jefferson mill was due to the very light cuts that I was forced into making with those two machines. And honestly those light cuts drove me bananas, not counting the super small work tables.

I've searched around and seem to only find results related to this machine for cutting aluminum. For whatever reason, all of my projects seem to revolve around steel.
I've never used a 932, as I went straight from a PM25 to a 9x40 (similar to the one Matt is selling). That machine needed some love up front, but once I got it tuned up, I could bury a 5/8" hogger end mill (corn cob type) an inch deep in mild steel without a problem.

As you say, there are a bunch of factors that go into answering your question. If it were me, for hogging steel on a 932, I would use rougher-type endmills to do the bulk of the material removal and use regular endmills for your finish passes to dimension. This does two things. One, it is less stressful on the machine, making it last longer, and two, it saves your good end mills for finish work. :)

I think that if you do this, your 932 should do fine.
 

navav2002

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#16
What do you consider a "light cut"?? Where would you like to be with your dept of cut?
 
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ThunderDog

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#17
5/8" hogger end mill (corn cob type) an inch deep in mild steel without a problem.
This would be more than satisfactory and has me looking to save just a little bit longer for the pm940. I'll buy once, cry once!!

FWIW, .050 to .075 was my limit on the Jefferson. It was painfully slow.
 

wrmiller

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#18
This would be more than satisfactory and has me looking to save just a little bit longer for the pm940. I'll buy once, cry once!!

FWIW, .050 to .075 was my limit on the Jefferson. It was painfully slow.
Not a bad idea. ;)

I'd still have that big 'ol bench mill if Matt hadn't made me a great deal on my 935. The young man I sold the 9x40 to still loves that machine.

I will admit though that I normally didn't push my mill that hard on a regular basis, but it was nice to know that I could do it if needed.
 

Ray C

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#20
I will admit though that I normally didn't push my mill that hard on a regular basis, but it was nice to know that I could do it if needed.
It always makes sense to not push a machine too hard. Why ruin your investment? I had so many customers who would take a light-weight lathe or mill and drive the daylights out of it. In some cases, it was because of inexperience, in other cases, it was intentional. Anyhow, when doing stock removal, I always use carbide hoggers (the kind with sharp points, not the flat carbide insert type) to get the bulk of the work done. Save your good smooth endmills for that that last 10 thou finish pass.

Ray
 

navav2002

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#21
I don't push my machine (pm932m) at all!! I'll admit that I'm a panzy but I hope to preserve this mill for a long time..I have my personal limits set to .100 doc for 6061, 7050 or 7076 alumnium...I know the machine will easily take more but I'm in no hurry..I don't have any roughing end mills but have been meaning to get one..Maybe I would be willing to take more depth of cut with a rmr endmill, I don't know..

That being said: I have very limited experience with steel on my 932 to this point..I have milled a little 4150A and went very easy with it (.020 max doc with high quality 4fl m42 end mills)..I think that was some pretty tough stuff..I had to learn how to handle it because it was different from alumnium..

From that very limited experience I can not imagine hogging 1" doc with steel on my mill...Like I say, I'm consertive and have no experience with a rmr end mill yet...But still, there ain't no way....

Mild steel may handle totally different than the 4150 alloy I don't know?? I have some 1018 laying around that I need to play with it and see how it is...

My opinion is that the square collum mill is not rigid enough to go super crazy... I noticed a lot more vibration than I'm use too while milling the steel compared to alumnium.. Once I got my spindle speeds and feed rates dialed in things seemed to smooth out a lot but I still took it easy.. In the end I was able to get nice surface finishes and hold good tolerances..

It may be that I don't have enough experience and I shouldn't be posting this.. But if I were buying a mill for hogging steel it would be a pm935 or similar knee type mill.. The square collum is not rigid enough in my opinion...

Just my .02...
 
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ThunderDog

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#22
I don't push my machine (pm932m) at all!! I'll admit that I'm a panzy but I hope to preserve this mill for a long time..I have my personal limits set to .100 doc for 6061, 7050 or 7076 alumnium...I know the machine will easily take more but I'm in no hurry..I don't have any roughing end mills but have been meaning to get one..Maybe I would be willing to take more depth of cut with a rmr endmill, I don't know..

That being said: I have very limited experience with steel on my 932 to this point..I have milled a little 4150A and went very easy with it (.020 max doc with high quality 4fl m42 end mills)..I think that was some pretty tough stuff..I had to learn how to handle it because it was different from alumnium..

From that very limited experience I can not imagine hogging 1" doc with steel on my mill...Like I say, I'm consertive and have no experience with a rmr end mill yet...But still, there ain't no way....

Mild steel may may handle totally different than the 4150 alloy I don't know?? I have some 1018 laying around that I need to play with it and see how it is...

My opinion is that the square collum mill is not rigid enough to go super crazy... I noticed a lot more vibration than I'm use too milling the steel.. Once I got my spindle speeds and feed rates dialed in things seemed to smooth out a lot but I still took it easy.. In the end I was able to get nice surface finishes and hold good tolerances..

It may be that I don't have enough experience and I shouldn't be posting this.. But if I were buying a mill for hogging steel it would be a pm935 or similar knee type mill.. The square collum is not rigid enough...

Just my .02...
Your experience is more than those who have never been around these machines. So, thank you for that input. Yeah, I have no intention of abusing a machine. However, I'm just curious what a reasonable depth of cut would be with these two models(pm932 or pm940). For anyone reading this post I will say again that the answer to the question of DoC has many variables to consider and no single definitive answer can be expected. But, a general answer could perhaps be extracted.:cool:(That last sentence of mine sounded like such a nerd.):cool:
 
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navav2002

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#23
Another problem I had milling the 4150 was keeping the head trammed.. I upgraded the nuts and used some nice tooling washers on the adjustment bolts which helped, I still had to take it easy...
 

wrmiller

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#24
My Charter Oak 9x40, and the PM940 push the boundary of the definition of a 'bench mill'. These things are massive. And quite rigid for their size.

My 9x40 could do anything my 935 can. The major difference is the knee and articulating head on the 935 makes some operations easier is all.

I will admit that I miss that extra 5" of table length I had on the 9x40 though. :(
 

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Having converted my PM-932 to CNC 4 years ago I will add my 2 cents.

I will start with I have no regrets converting a bench top mill to CNC as it has been a rewarding and educational experience. If you enjoy the process of learning and building then go for it. If you just want to run parts on a CNC then finding a purpose built machine (new or used) in working condition would be a better option. Had the PM-940 been available at the time I purchased my mill I would have spent the extra money for the increased Y travel and rigidity.

I got the cast iron base and have been able to make it work for my coolant enclosure but a purpose built stand would provide better use of the space below and allow for better customization.

CNC conversion of the PM-932

Decide early if you want to have manual capability along with CNC or just CNC. If you want to retain manual use then flood coolant is not really an option with the need for a more comprehensive enclosure. Mine is CNC only with flood, mist and air cooling. I believe the benefit of flood coolant outweighs the drawbacks but it is more work to setup and maintain. I can do most manual operation with the game pad pendant but I did miss the ease of use of a manual mill for certain things and have added a heavy duty drill press with an X,Y table to my machinery for manual use.

The Chinese ball screws, nuts and bearing blocks are perfectly adequate. The bearing blocks will need some TLC to get them at their optimum. Use the double ball nuts. I used two single ball nuts on each screw and while it provides better adjustability, it is a pain to work on and requires periodic adjustment. I recommend 20mm on the X & Y and 25mm on the Z.

An oil system for the ways and ball screws is a must. I have separate one-shot oil pumps for the X,Y axis and the Z axis. I originally had a single pump but found that the lines to the Z axis would drain back. The extra pumping was wasting oil of the X,Y axis. Adding check valves could have solved this but that would have required a complete redesign of my distribution manifold. At my next tear down for service I plan of replacing the two pumps with an automatic pump system and new manifold.

Steppers or servos. I personally don't think servos are worth the additional cost for this level of mill. Myself and others who have converted similar machines are running larger steppers with no issues of lost steps. Larger steppers are slower but on this size mill 100 inches per minute is plenty fast. I rarely exceed 50 IPM on most work.

Don't skimp on the electronics. Stay away from cheap no-name breakout boards that have little or no support and lower cost motion controllers like the UC100 are not worth the headaches. For steppers I blew several power supplies and drives before settling on dives with built-in power supplies. Theses have been trouble free. Start out with a controller package than can do spindle & coolant control. Your electronics may be driven by what motion control software you use. I run Mach3 for simplicity. While it has its quirks I find it straight forward to use. If your a computer guy who can deal with Linux then LinuxCNC is a good option. We use it at the high school on the router and it works great. I don't use it since I prefer to stay away from anything that requires command line input for tasks that should be done with a mouse click. Personal problem.

At some point the gear head of the PM932 will become too slow for anything but steel and the noise will drive you nuts. A high speed spindle conversion will probably be seriously considered so it is a good idea to plan ahead for it.

Some kind of power draw-bar system will become a must. Having an idea of how you intend to use the machine will help determine what system will work for your needs. I do a lot of complex parts with multiple tool changes. I went with the Tormach TTS system and a pneumatic draw bar. I love this system other than I undersized the air cylinder based on some bad information and I can have issues with tool pullout when hogging with cutters 1/2" and larger. That is also on my list to upgrade.

My largest grip about the mill is the dovetail column. Because I am driving the head and not the quill to get the maximum amount of Z axis travel the Z axis gibs need to have some drag but still be able to move. This introduces some nod and flex to the head. The nod is compensated by shimming the base of the column. The flex is usually not noticeable expect for heavy drill ops and quick Z moves on 3D parts.

To your question regarding cutting steel. I use serrated roughers for heavy material removal but I prefer fast light passes over slower heaver passes as it it easier on the machine.
 

ThunderDog

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#26
WOW, thanks for all that hindsight jbolt!!

I built a 3d printer from LOTS of reading back in 2010. That was right before the big commercialization of them. Crazy to think I spent about $900 for that thing and the work envelope is nowhere near what can be had for about half that price for printers today. It was a ton of fun, challenging, and a great learning experience. I envision a CNC conversion will be similar in the ways of reading, researching, collecting parts, learning more electronics, more reading, more purchasing, etc.

I will get to that stage one day and your feedback is most appreciated.
 

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#28
What jbolt said. He covered it well in his explanation of converting to CNC.
 

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#29
I'm curious how much you spent ($ not the time) on building your enclosures, VFD setup, coolant rigging, ballscrew conversion?
 

jbolt

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I'm curious how much you spent ($ not the time) on building your enclosures, VFD setup, coolant rigging, ballscrew conversion?
Costs as my mill sits today.

PM-932 w/cast iron base/ delivered $2400

Basic CNC conversion including balls crews, couplers, pulleys, belts, steppers, drivers, power supplies, breakout board, motion controller, computer w/screen & keyboard, control box and switches, limit switches, aluminum stock, wire & cable / connectors, misc hardware. $2800

One-shot oil system. $200

High speed spindle conversion (motor, vfd, electrical cable & wiring, spindle bearings etc.) $700

Pneumatic draw bar system (air cylinder, switch, hose & fittings, regulator, filter, hardware etc.) $700 (not including air compressor)

Flood coolant system (pump, nozzles, plumbing, solenoid switch, tank, hardware, etc.) $350

1/2 height enclosure (custom aluminum sheet metal pan, aluminum panels for the walls, 8020 for the frame, Plexiglas door panels, hardware, etc.) $600

Total $7750
 
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