Breif Review of PM932M Mill/Drill

[schmeky]

Purchased a new PM932M from Precision Matthews to help with a small growing business. I have used a GO704 for the past 2 years with very good results, but I wanted a longer Y axis, Z power feed, X power feed, and a DRO. The PM932M I ordered had all the options less the spindle boring feature which I would never need.

Mill is typical Chinese, somewhat rough, somewhat crude in some areas, but no surprises. I would have ordered this from Grizzly but they did not offer everything I wanted and I don't have time to add on all the features I needed. Precision Matthews (PM) had all the options I wanted installed, basically read to go.

After cleaning, I removed the gibs I did a thorough clean and lube. The Z axis motor is shipped wired but not attached, a 5 minute job at best. DRO is wired in and glass scales are mounted, but readout has to be mounted, another 5 minute job. Greasy finger prints all over the aluminum angle the scales are mounted on and the cables to and from the readout were wadded up pretty badly. Once up and running, I checked the X tram. It was dead on. Y was out .0015" in 8 inches. I can live with that since most of my work envelopes are not large.

The spindle readout is poor at best and every time you turn it on, it defaults to metric. The spindle tension spring is not adjusted correctly and the spindle will not respond to the fine feed accurately. Entirely unacceptable. Instructions tell you how to increase the tension but so far I have not been able to accomplish this. I noticed there is no way to hold the spindle for a tool change so I called PM on a Monday and left a message. I waited 4 days and never got a call back. So Friday I called and the person I spoke with said to put the head in L/1, that this is all you need for an effective tool change. So on the first trial cut, the end mill slipped in the R8 collet over .250", due to a lack of proper tension. Entirely unacceptable. Anyone considering purchasing this mill will have to buy the Luminar 28MM spline wrench to be able to use this mill. How/why this mill can be sold w/o a spindle wrench defies reason.

I'll update if folks are interested as I get into more use.

[WJH]

Purchased a new PM932M from Precision Matthews to help with a small growing business. I have used a GO704 for the past 2 years with very good results, but I wanted a longer Y axis, Z power feed, X power feed, and a DRO. The PM932M I ordered had all the options less the spindle boring feature which I would never need.

Mill is typical Chinese, somewhat rough, somewhat crude in some areas, but no surprises. I would have ordered this from Grizzly but they did not offer everything I wanted and I don't have time to add on all the features I needed. Precision Matthews (PM) had all the options I wanted installed, basically read to go.

After cleaning, I removed the gibs I did a thorough clean and lube. The Z axis motor is shipped wired but not attached, a 5 minute job at best. DRO is wired in and glass scales are mounted, but readout has to be mounted, another 5 minute job. Greasy finger prints all over the aluminum angle the scales are mounted on and the cables to and from the readout were wadded up pretty badly. Once up and running, I checked the X tram. It was dead on. Y was out .0015" in 8 inches. I can live with that since most of my work envelopes are not large.

The spindle readout is poor at best and every time you turn it on, it defaults to metric. The spindle tension spring is not adjusted correctly and the spindle will not respond to the fine feed accurately. Entirely unacceptable. Instructions tell you how to increase the tension but so far I have not been able to accomplish this. I noticed there is no way to hold the spindle for a tool change so I called PM on a Monday and left a message. I waited 4 days and never got a call back. So Friday I called and the person I spoke with said to put the head in L/1, that this is all you need for an effective tool change. So on the first trial cut, the end mill slipped in the R8 collet over .250", due to a lack of proper tension. Entirely unacceptable. Anyone considering purchasing this mill will have to buy the Luminar 28MM spline wrench to be able to use this mill. How/why this mill can be sold w/o a spindle wrench defies reason.

I'll update if folks are interested as I get into more use.

Why are you using collets instead of endmill holders? You need the extra clearance?

[schmeky]

Most of my end mills do not have the flat for a secure purchase for use with the end mill holders. Have plenty of room.

[Harold_V]

Why are you using collets instead of endmill holders? You need the extra clearance?

End mill holders, especially on light duty machines, are not only NOT necessary, but I'd tend to support their not being used unless there is good reason. Keeping the end mill near the bearings in the quill is a far better idea.

There's absolutely nothing wrong with driving end mills with collets, even under what one might consider to be a heavy load when the machine in question isn't capable of taking huge cuts.

I used my BP mills for 16 years (commercially) and never once used an end mill holder. I don't own them to this day, and have no regrets, with one exception. That was when I was running a 1" end mill, buried .60" deep, full width, in aluminum. It gradually withdrew from the collet (about 1/8" total) and ruined the template I was machining. Beyond situations like that, or where the extension is to benefit, they simply aren't a requirement.

Harold

[BadDog]

I run collets pretty much exclusively. And I don't abuse it, but I'm far from delicate with my mill. No problems to report. I've lifted parts out of the vise, only very early on (before I knew how to tighten a collet) ever had an EM slip. In fact, the only time I use EM holders is when I need clearance around obstructions.

[stevec]

Most of my end mills do not have the flat for a secure purchase for use with the end mill holders. Have plenty of room.

If you prefer/require the use of end mill holders you could grind a flat on the shank of the end mills that don't have one.

[schmeky]

I had to revamp the drawbar on the PM932 to so I could apply sufficient torque to the collet. I did some cuts this week and it is working fine. But this mill needed an inordinate amount of work to make it useable. However, I seem to have turned the corner and now it's finally making good cuts.

On the collet/end mill holder topic, I have never had a problem with collets (excluding this new PM932). I prefer them since they are close to the spindle bearings and even though I have room for EM holders, I like the compactness of the collet.

In hindsight, I would not buy a PM932 again. Thanks for the replies.

[schmeky]

Just a quick update. After much fiddling and adjusting, I now have this mill working well and it's running as it should. I would probably not do this again, but at least it is now producing accurate work for my business.

[WJH]

Why are you using collets instead of endmill holders? You need the extra clearance?

End mill holders, especially on light duty machines, are not only NOT necessary, but I'd tend to support their not being used unless there is good reason. Keeping the end mill near the bearings in the quill is a far better idea.

There's absolutely nothing wrong with driving end mills with collets, even under what one might consider to be a heavy load when the machine in question isn't capable of taking huge cuts.

I used my BP mills for 16 years (commercially) and never once used an end mill holder. I don't own them to this day, and have no regrets, with one exception. That was when I was running a 1" end mill, buried .60" deep, full width, in aluminum. It gradually withdrew from the collet (about 1/8" total) and ruined the template I was machining. Beyond situations like that, or where the extension is to benefit, they simply aren't a requirement.

Harold

I see the point about keeping the endmill close to the bearings, but I do NOT like the idea of having to torque down the quill with collets so much. A light snug twist with the wrench is all that is needed for EM holders.

[Harold_V]

I see the point about keeping the endmill close to the bearings, but I do NOT like the idea of having to torque down the quill with collets so much. A light snug twist with the wrench is all that is needed for EM holders.

I'm not sure I understand your concern. The quill is designed for just such application. None of the torque of which you speak goes through the bearings---it's fully independent of them.

Mind you, I'm not trying to change your mind. Each of us is entitled to hold certain thoughts and beliefs as we see fit. I, personally, don't much care for reamers, as I've had more than a few negative experiences with their use. Doesn't mean others must share my views!

Harold

[pete]

With a poorly built offshore mill, or even a dirt cheap drawbar then maybe the drawbar's metallurgy,heat treatment or the lack of even having any, and just how sloppy and undersize the threads were cut or rolled may give reason to be concerned about putting some real torque on the drawbar with those internal spindle collet's. But it's not real hard to build your own replacement drawbar using simple mild steel and a cut off grade 8 bolt for the threads. You can cut a bolt head on the top end, then turn the drawbar to size, or thread the top end and just use two nuts to lock them to the drawbar so they can't rotate. Even better would be to thread the drawbar, then weld the nut to it at the top side of the nut. At the bottom end just weld, solder or locktite that cut off grade 8 bolt into the drawbar. I'd want to wrap the bottom of the threads in a wet rag if welding or soldering though. And if it's a standard imperial R-8 and the length is approximately correct, then buying a good one from Bridgeport or half a dozen other vertical mill manufacturer's that have mills at least as good or even better than today's Bridgeport is also easy enough and not that expensive. I always add a few drops of oil to the female threads on any R-8 tooling before I use it since that helps with the tightening torque, and I'd bet your tooling and drawbar threads will last at least 10 times longer. Continuous use in and out and with that required torque done with bone dry threads is really hard on them. Once they start to gall and wear and without cleaning the threads, then all those steel particles floating around in there will just vastly increase the wear issue. It doesn't hurt to clean and flush out the old oil and any wear particles from your collets once in awhile with some spray cleaner either. CRC electrical contact cleaner works well for that.

You could of course use a collet chuck and a set of ER collets. Even though I normally use those, I still have a set of end mill holders for the few times my collet chuck would prevent reaching in to where it's needed. A second smaller series of ER collets might have got the job done just as well other than for any larger tool shank sizes. But any vertical mill needs all the rigidity you can get so those spindle collets are much better than anything else. Even a few extra inches sticking out like my ER collet chuck does make a huge difference. The closer you can stay to those spindle bearings then the better for both your bearings and the work. One side benefit to those EM holders is they will give me a repeatable Z axis height setting, but you do need a good enough 3 axis and repeatable dro to utilise that feature.

Since I have zero experience or knowledge with your mill, I can only suggest what might allow you to tighten and loosen your spindle collets. They make what are called "Spline wrenches" if you can see enough of the spline sticking out of the top of your spindle, then using one of those would allow you to hold the spindle from rotating. That also will require your spindle to be up and inside the head as much as possible though. Or if there's enough of the spindle sticking up outside the top side of the head it's not impossible to build a two piece nut something like a lathes half nut but it gets clamped to the spindles O.D. as tight as possible with multiple bolts. With even mild steel you then cut an octagon on it as your building it, and then use a large wrench to again hold the spindle in place. Rarely is there no way around a design fault if you put your mind to it. It does take a bit of experience before you start seeing things like that I think.

Your spindles DRO faulting to metric sounds like a programming problem to me. Check your DRO's manual and my guess is there's a way to set it up so it stays in whatever form of measurement you want. I could very well be wrong about that too.

Pete

[WJH]

I see the point about keeping the endmill close to the bearings, but I do NOT like the idea of having to torque down the quill with collets so much. A light snug twist with the wrench is all that is needed for EM holders.

I'm not sure I understand your concern. The quill is designed for just such application. None of the torque of which you speak goes through the bearings---it's fully independent of them.

Mind you, I'm not trying to change your mind. Each of us is entitled to hold certain thoughts and beliefs as we see fit. I, personally, don't much care for reamers, as I've had more than a few negative experiences with their use. Doesn't mean others must share my views!

Harold

Well Harold, your point had me thinking about arms, levers, and torque applied... I ordered a 3/8th's R8 collet to play with. Just based on simple math alone, I would think it would be well worth it for a more rigid milling experience.
Perhaps it will have me singing a different tune about what my Mill can handle...
The endmill holder I have is very convenient to use, but I'd rather have the rigidity at this point.