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Square column vs. small knee mill

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AndySomogyi

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I’m looking at buying a milling machine for my small shop, and I’m down to two choices. A new PM-932 or a used Enco 100-5200.

Which one is a better choice? Which one is more rigid?

These are both about the right size for me.

I’m sure many here are familiar with the PM-932. My concerns with it are the lack of a precision dial in the Z, and the backlash in the quill adjustment. I’m used to a Bridgeport where you have very precise control of the knee to adjust the depth, and only use the quill depth for rough adjustment. But it’s a new mill from a reputable company. The geared head is nice. I suppose for depth, I could just use an dial indicator between the head and table for fine adjustments.

My concerns with the Enco is that it’s 30 years old, and who knows what kind of shape. It’s a belt drive which is very annoying for speed changes. Is it worth the headache? It’s an 8x30 small knee mill, basically the same as the Grizzly G0731. I’ve found this used one on eBay for 1700.

I just used to have small grizzly round column mill which was effectively worthless for steel because the lack rigidity, and don’t get me started with the round column.

So, take a chance on a used one, or buy an new PM?
And a pic of the Enco

474AB215-B1DE-4312-B868-D070B81F1B67.jpeg

The PM932
 

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markba633csi

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#2
I would choose the knee mill over the movable head type. On the Enco, you may find it may be something other than 0.10 inches per revolution on the leadscrews- can be a bit awkward if you don't have a DRO
mark
 

Ulma Doctor

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#3
i suppose it depends on how big of work you do.
for me i'd buy the Enco machine, only because i owned similar machines.
i like the charm of older (heavier) and more expensive to produce equipment.

the PM machine must be ok they keep making them
 

wrmiller

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#4
I have owned several square column mills (LMS, PM, Charter Oak) and managed to use the Z-axis OK. :)

However, I did have a DRO scale on the head to help with accuracy/repeatability and always made final translations in the upwards direction to keep the head/leadscrew interface in tension. Like you, I only used the quill for rough adjustments and drilling.

My personal preference has been to buy new instead of used, because you really never know what you're getting with a used machine. A used machine has wear, period. How much is the question. A little wear can be fine, but too much and you end up with a really large paper weight as a neighbor friend of mine up in CO found out.

Of course a lot of this comes down to what you want to do with the machine, and how accurate you want/need to be. Rigidity is less on smaller machines. That's a given. Doesn't mean you can't make anything with them. I built a competition pistol (1911) on my first machines which were Sherlines. After being told by a professional machinist that it couldn't be done. :)

Bottom line I guess is you have to decide between taking a chance on the little knee mill, or buying a new PM and adjusting to a different way of handling Z-axis translations. That and if you have issues with the PM you will get great customer service. Not sure what you'll get with that used machine.
 

Bob Korves

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#5
I would prefer the Enco, but I think the price is too high at $1700 and with no tooling included. Don't buy it without test driving it.
 

JimDawson

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#6
Rigidity is less on smaller machines. That's a given. Doesn't mean you can't make anything with them. I built a competition pistol (1911) on my first machines which were Sherlines. After being told by a professional machinist that it couldn't be done. :)
That pretty much supports my theory that the accuracy is built into the machinist not the machine ;)
 

Downwindtracker2

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I have a Taiwanese made Rong Fu 45, I think they were the first with the square column mill/drill. I like the 8x32 envelope. They are not as handy as a baby Bridgeport style but are probably more ridged. The design would suggest that. They use less floor space as well. Just as a gearhead drill press they are worth their price. Rong Fu now has a power down feed for boring BTW. However I have noticed the clones of the RF 45 to be slightly or more than slightly, smaller and lighter. Check the weights.

I paid $1750 CDN (75% USD) ,but I got a DF 1224g lathe with it. I valued the mill at $1500. New RF 45s are over $5000 US.
 

TomS

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#8
I have the PM-932 converted to CNC. It's a very solid mill. The only complaint I have is the lack of Y axis travel. At 8" it's a bit on the skimpy side. You may want to look at the PM-940 with 12" of Y travel.
 

BaronJ

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Hi Andy,

My preference would be the knee mill every time ! My mill is virtually the same as the PM932. I do some good work with it but it has a lot of limitations, but you learn to work around them.
 

AndySomogyi

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Thanks for your answers guys. There are some differing opinions here, but at least I haven’t heard a single report that either machine is total garbage, so looks like I’ve come up wth a pair of decent choices.

Got some thinking and considering to do.

On one hand, I’m half way tempted to shell out the $4300 for a PM 835S, which literally is a baby Bridgeport with a real J head clone. But that’s it for me money wise.
 

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Downwindtracker2

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I can understand that, I was waiting for the Grizzly tent sale, I live close by. But how do you tell She Who Must Be Obeyed .
 

BGHansen

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#13
I had a round column Grizzly mill drill and upgraded to a used Jet JVM-830 (same as the Enco pictured). I paid $1200 for mine in around 1989, mill was new in 1981. Really like the knee mill over the round column Rong Fu Grizzly clone. I haven't run a square column mill so not adding any actual experience here on that style, but I've had no issues with my Jet. I took the power feed off the Grizzly and put is on the Jet, made a 5" rise block and added a 4-axis DRO. The previous owner added another set of pulleys on the mid and motor pulleys for a lower speed range. Stock slowest speed was 280 RPM, mine will go down to 145.

I guess a plus on the square column is if you have a huge part overhanging the table, it'd stay stationery vertically on the square column but moves with the knee mill.

Good luck with the hunt. The 835S looks really tempting, but for $4300 you could buy a pretty nice "real" Bridgeport.

Bruce


1542936247265.png
 
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BGHansen

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#14
Here are some milling machine options off Craig's List in your general area (always fun to "shop" with someone else's money). I found these using the search engine www.searchtempest.com. Really like this search engine as you can input your search and lots of sort parameters like cost, miles away, etc. Searches CL and eBay.

Bruce


Index #645 mill for $1200, just North of Ann Arbor, MI. Comes with a 6" vise, many cutters, collets, hold downs.
https://detroit.craigslist.org/okl/tls/d/index-vertical-milling/6729496701.html

U.S. Burke model V, $1400, just North of Muskegon, MI. Has a #9 B&S spindle but comes with collets and a VFD.
https://muskegon.craigslist.org/tls/d/vertical-mill-us-machine-tool/6738749920.html

Lagun mill with a 10x50 table, $4000 in Grand Rapids, MI. Has an old 2-axis DRO, power feed on the X.
https://grandrapids.craigslist.org/tls/d/lagun-mill/6744019182.html

DoAll mill, $3500 in Olive Branch, MS. #30 spindle with some tooling, power feed on X.
https://nashville.craigslist.org/tls/d/very-nice-doall-mill/6749712082.html

Millport mill with a 10x50 table, $4800 in Louisville, KY. R8 spindle, 2-axis DRO, power feed on X.
https://louisville.craigslist.org/tls/d/millport-3kvh-knee-type/6754506936.html

Millport milling with 10x50 table, $3500 in Canton, OH. Runs on single phase, vise.
https://akroncanton.craigslist.org/hvo/d/millport-mill-milling-machine/6741980008.html

Bridgeport with a 9x42 table, $5500 outside Toledo, OH. Power feed on X, 2-axis DRO.
https://toledo.craigslist.org/tls/d/bridgeport-series-milling/6742273044.html

Pilgrim Bridgeport clone, $1500 or $1000 if the seller removes the modern 3-axis DRO. Just West of Cleveland, OH. Power feed on X, vise.
https://sandusky.craigslist.org/tls/d/vertical-milling-machine/6741047228.html

Millport with 10x50 table, $4000 outside of Columbus, OH. Power feed on X, 2-axis DRO.
https://columbus.craigslist.org/tls/d/used-millport-3hp-10x-50/6733090242.html
 

wrmiller

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#15
Thanks for your answers guys. There are some differing opinions here, but at least I haven’t heard a single report that either machine is total garbage, so looks like I’ve come up wth a pair of decent choices.

Got some thinking and considering to do.

On one hand, I’m half way tempted to shell out the $4300 for a PM 835S, which literally is a baby Bridgeport with a real J head clone. But that’s it for me money wise.
You'll always get differing opinions here, or anywhere for that matter, but that is not a bad thing. :)

Truth be told, there is nothing wrong with either style machine. Both will do the job, but some different techniques will be required for doing the same operation on a different style machine.

I was going to suggest you look at the PM835S, but was not sure of your budget. It looks like a pretty decent machine for the money.

Full Disclaimer: I now own a PM935S with a VFD for variable speed. And while this machine doesn't appear to be any more capable than my 9x40 Charter Oak was, it IS much easier to do many things on. A knee mill with a articulating head is a easy thing to get used to, and spoiled me quick.

If you do get the 835, a write up of your impressions, along with lots of pics might just help others who are in a similar position.
 

ConValSam

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#16
Having owned both styles, I really can't imagine going back to a column mill. In addition to what others have said, I would add that a knee / quill combination provides the best options for Z motion. Everytime I use my Clausing 8520, I marvel at how such a small machine can make such robust cuts. I would try to find an 8520, its more rigid cousin the 8530, or the Rockwell mills that offers a similar design. Although I have never used one, I would buy a MillRite in a second: more rigid, bigger axis travel, but still smaller than a Bridgeport class.
 

AndySomogyi

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Thanks!

However the problem with these monsters is I only have a tiny space to work with, I’ve got a 1 car garage that’s already housing my project car (the thing I’m building with my tools), lathe, welder, and other tools.

Sure, I’d love a full size Bridgeport, if I had another bay.

Here are some milling machine options off Craig's List in your general area (always fun to "shop" with someone else's money). I found these using the search engine www.searchtempest.com. Really like this search engine as you can input your search and lots of sort parameters like cost, miles away, etc. Searches CL and eBay.

Bruce


Index #645 mill for $1200, just North of Ann Arbor, MI. Comes with a 6" vise, many cutters, collets, hold downs.
https://detroit.craigslist.org/okl/tls/d/index-vertical-milling/6729496701.html

U.S. Burke model V, $1400, just North of Muskegon, MI. Has a #9 B&S spindle but comes with collets and a VFD.
https://muskegon.craigslist.org/tls/d/vertical-mill-us-machine-tool/6738749920.html

Lagun mill with a 10x50 table, $4000 in Grand Rapids, MI. Has an old 2-axis DRO, power feed on the X.
https://grandrapids.craigslist.org/tls/d/lagun-mill/6744019182.html

DoAll mill, $3500 in Olive Branch, MS. #30 spindle with some tooling, power feed on X.
https://nashville.craigslist.org/tls/d/very-nice-doall-mill/6749712082.html

Millport mill with a 10x50 table, $4800 in Louisville, KY. R8 spindle, 2-axis DRO, power feed on X.
https://louisville.craigslist.org/tls/d/millport-3kvh-knee-type/6754506936.html

Millport milling with 10x50 table, $3500 in Canton, OH. Runs on single phase, vise.
https://akroncanton.craigslist.org/hvo/d/millport-mill-milling-machine/6741980008.html

Bridgeport with a 9x42 table, $5500 outside Toledo, OH. Power feed on X, 2-axis DRO.
https://toledo.craigslist.org/tls/d/bridgeport-series-milling/6742273044.html

Pilgrim Bridgeport clone, $1500 or $1000 if the seller removes the modern 3-axis DRO. Just West of Cleveland, OH. Power feed on X, vise.
https://sandusky.craigslist.org/tls/d/vertical-milling-machine/6741047228.html

Millport with 10x50 table, $4000 outside of Columbus, OH. Power feed on X, 2-axis DRO.
https://columbus.craigslist.org/tls/d/used-millport-3hp-10x-50/6733090242.html



Sent from my iPhone using Tapatalk Pro
 

BGHansen

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#18
Hi Andy,

Yeah, the 2000 lbs. plus machines do take up some space. Here are some smaller bench top mill/drills that may work for you. Others with actual experience on square column mills will have better input than me; my impression of those machines is you can move the head up/down without loosing registration in the X/Y. Problem with round column mills (like my old Grizzly Rong Fu clone) is when you move the head up/down, registration to the table is lost. There are many articles out there on ways to minimize the effect, necessity is the mother of invention as thousands of the round column mills are out there.

Bruce

Jet gear head mill drill, $2050 outside Lexington, KY.
https://lexington.craigslist.org/tls/d/jet-milling-drilling-machine/6742394109.html

Rong Fu style mill/drill (MSC), $1600, outside Nashville, TN. Collets, drill chuck, clamping kit and nice vise.
https://knoxville.craigslist.org/tls/d/msc-milling-machine/6753940288.html

Jet mill/drill, $1300 outside Toledo, OH. Vise, power feed on X-axis.
https://toledo.craigslist.org/tls/d/mill/6739421669.html

Grizzly 1006 Rong Fy clone, $1850 in Chicago, IL. Vise, collets, drill chuck, some cutters
https://chicago.craigslist.org/sox/tls/d/grizzly-30-milling-and/6753346494.html

Precision Rong Fu clone, $1000 in just South of Kalamazoo, MI. Vise, collets
https://grandrapids.craigslist.org/tls/d/precision-milling-machine/6753238925.html
 

AndySomogyi

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#19
I just sold a Grizzly round column mill which was horrible, basically useless for anything other than aluminum, and don’t even get me started about that horrid round column.

Whatever I get will have dove tailed Z axis.

I am leaning towards the PM932, though I looked at a new genuine Rong Fu, and evidentially the higher end Chinese mills are actually better than the new Rong Fu ones.

With a DRO, you get perfect Z axis positioning on the square column RF45. Note, the RF45 head is moved with a lead screw, just like the knee on a knee mill. The smaller square column ones only have a z axis rack and pinion, so you can’t accuratky position the head in the Z.


Hi Andy,

Yeah, the 2000 lbs. plus machines do take up some space. Here are some smaller bench top mill/drills that may work for you. Others with actual experience on square column mills will have better input than me; my impression of those machines is you can move the head up/down without loosing registration in the X/Y. Problem with round column mills (like my old Grizzly Rong Fu clone) is when you move the head up/down, registration to the table is lost. There are many articles out there on ways to minimize the effect, necessity is the mother of invention as thousands of the round column mills are out there.

Bruce

Jet gear head mill drill, $2050 outside Lexington, KY.
https://lexington.craigslist.org/tls/d/jet-milling-drilling-machine/6742394109.html

Rong Fu style mill/drill (MSC), $1600, outside Nashville, TN. Collets, drill chuck, clamping kit and nice vise.
https://knoxville.craigslist.org/tls/d/msc-milling-machine/6753940288.html

Jet mill/drill, $1300 outside Toledo, OH. Vise, power feed on X-axis.
https://toledo.craigslist.org/tls/d/mill/6739421669.html

Grizzly 1006 Rong Fy clone, $1850 in Chicago, IL. Vise, collets, drill chuck, some cutters
https://chicago.craigslist.org/sox/tls/d/grizzly-30-milling-and/6753346494.html

Precision Rong Fu clone, $1000 in just South of Kalamazoo, MI. Vise, collets
https://grandrapids.craigslist.org/tls/d/precision-milling-machine/6753238925.html
 

mattthemuppet2

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#20
From what I've seen weight and travels wise the 2 mills in the OP are pretty similar. I haven't used a square column mill so can't really make a comparison, but I have a 6x26 knee mill (small cousin on the Enco) and I think that it's fabulous. Doesn't have enough Z travel, so a riser is on the list. I added a variable speed treadmill motor and that made a huge difference in utility. One plus about belt drive is that it's quiet.
 

Praeger

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Thanks!

However the problem with these monsters is I only have a tiny space to work with, I’ve got a 1 car garage that’s already housing my project car (the thing I’m building with my tools), lathe, welder, and other tools.

Sure, I’d love a full size Bridgeport, if I had another bay.
Even the smallest knee mills will require a work envelope of 74"x 50". That's a lot of room out of a single car garage. Have you looked at the PM-833T? Several H-M members have posted reviews.
 
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