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A few questions on new mill purchase

dado5

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#1
I am another newbie wanna be machinist. I have an old atlas/clausing lathe that works well. I now want to purchase a mill. I have never used one, but have watched a lot of videos! I don't really want to buy another old machine (i.e bridgeport) and am probably going to get either a PM or Grizzly. I obviously want the biggest I can get because I don't want to have to upgrade in a year or two. I have a few questions that I can't really answer since I have never run a mill.
1. Gear head or belt drive? I imagine gears would be quicker and easier to change speeds. My lathe is belt drive and I would rather gear unless there is a reason not to.
2. Do ineed variable speed? seems like it would be nice but not sure if necessary.
3. I would like dro and power feed so I don't have to upgrade eventually.
comparing a pm25 to a pm 932 to a pm 940 how much difference in capability? I am sure they will all be accurate enough for me but I don't really want to be taking only 10 thou. cuts at a time on steel. This will not be production stuff, just hobby messing around.
 

BGHansen

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#2
I have a Jet JVM-830 and a Bridgeport 2HP, used to own a Grizzly Mill/Drill round column like the Rong Fu.

I like the variable speed on my Bridgeport. My Jet mill has the typical center cone pulley and the speed steps from around 500 RPM down with the motor belt high, and 1000 RPM up with the motor belt low. Invariably, I need to run at the slower range to use an edge finder or 2" face mill, then have to pull the spindle and motor belts to flip them to get to the higher range for using a 1/4" end mill or drilling smaller holes. Not a deal breaker, but it's like have an opener on your garage door; beats the heck out of getting out of the car to pull the door open. The gear head would have just of rapid of changes.

I'd guess that the steps in the gear range should cover your work. My Jet has an added-on pulley on the jack shaft and motor, lets me get down to around 175 RPM. Stock machine is something like 300 RPM. My BP advertised range is something like 60 - 4200 RPM. I haven't done anything to date that took me out of a 200 RPM to 2000 RPM range.

If you're choosing between DRO or power feed, get the DRO. Your only regret will be that you didn't do it sooner.

I be giving you opinion with no experience on the PM choices, so look for some advice from others chiming in.

Welcome to the wonderful world of machining and the Hobby Machinist forum!

Bruce
 

T Bredehoft

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#3
I'm content with my PM25, in aluminum I've taken .050 by .25, with no problems other than a built-up pile of chips around the cutter. I ordered DRO and build an X drive. If I could have afforded a larger mill I'd have bought one. Only once in the two years I've had it was the table/movement too small.
I like the variable speed belt drive. It has High and Low range, (move the belt, its' not hard) but I keep in in low range, I can tap at 180 RPM, and cut aluminum at 1500.
 

mksj

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#4
A few answers or should I say recommendations.
1. Gear head vs. belt drive is often a function of the type and size of a machine, having had both, belt drive is much quieter and less long term maintenance. Almost all knee mills are belt drives of some form, with the exception of the back gear. Bench tops are often gear heads, although those with motor variable speed often have two belt speeds. My preference is for a belt, strictly from a noise an maintenance stand point of view, but really machine specific.

2. Variable speed is nice, but in a mill not a deal breaker. Mills have been around for years with a limited number of speeds. What it does limit you somewhat to is having higher speeds for say aluminum. Still you are looking at a speed range of something like 90-2000 which is more than adequate. If you were to go with 3 phase, than a VFD on a mill is a very easy and not terribly expensive proposition (I would say something like $300 for something simple using something like a Teco L510).

3. Power feed is a real plus for multiple reasons, as a minimum I would get an X power feed, possible a Z. DRO on a mill is really helpful, more for a newbie because it take a lot of the guess work out and dial/revolution counting. Also it gives you a true position. To keep the price down, probably go with glass scales, 2 or 3 axis, and use a battery operated quill DRO which can be had very reasonably. If you can afford a slightly better DRO like the Easson 12B 3 axis DRO with glass scales (install it yourself), they are nice for bolt circle and a number of other functions, if funds hold you back then there are less expensive 2 axis alternatives. I never used/needed a Z axis on my benchtop, mostly because I used the quill and the head was always locked when milling.

4. As far as mills, there is no substitution for weight ans size, but then it depends on what you want to do. I think a knee mill is the way to go if you can afford one and need the larger capacity, so something like a PM935. On the Benchtop side, I would go bigger and better, but on the smaller end the PM-927V or PM-930MV strike a good balance of size and function and the variable speed is really nice. If moving up and you want better quality in a benchtop I suggest considering the PM-833T at very close to the PM-940 price. The PM-833T comes with a 5 year warranty, says something about the machine to offer a warranty that long. The other PM benctops are 3 years, which is still is much better than other companies. My new knee mll came with a 1 year warranty. I use to have a benchtop mill similar to the PM-932, and often ran out of Y-axis travel especially if you add a DRO scale and a larger vise, thus the recommendation for the PM-833T or PM-940 if going big.
 
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wrmiller

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#5
I had a earlier version of the PM25, and a 9x40 bench mill very similar to the PM940. I now own a PM935S with a VFD for variable speed.

If you are looking at bench/bed mills in this range, I will have to give a second vote to mksj's suggestion that you give the PM833 serious consideration. Taiwan built, with a longer Y-axis travel than typically found in machines this size. FYI, I found myself running out of Y-axis travel on the PM25, which is why I ended up going with the larger 9x40. But, it was a Chinese machine that took me over a year of tweaking to get it right.

If this mill had been around when I was in the market for a larger mill than the PM25 I would have ended up buying this one. Between being Taiwan built, a great warranty, and Matt's great after-sale service, it would have been a no-brainer for me. :)

FYI, if you can afford a little more $$ and have the space, the new PM835 might be a good fit between the 833 and the 935.
 
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dado5

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#6
thanks for all the answers. I am driving myself nuts thinking about this. The bottom line is I would love to have a good old bridgport mill but don't have the time to go to auctions or chasing junk on craigslist. I would love to just order something, have it show up and set it up and go but don't want to regret not getting the machine I really want. I could probably do anything I want with a pm25. Maybe the 835 is what I need, or get a pm25, learn how to mill and if I need larger in the future upgrade.
 

wrmiller

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#7
The trick to using smaller machines is to stay within it's work envelope. People who go out and buy a PM25 and then expect it to hog steel with a 3/4" end mill will be in for a serious smack of reality. ;)

Smaller machines require patience. And more thinking 'outside the box'. Heck, I machined a three-port compensator out of titanium for one of my early competition pistols on a sherline lathe and mill. I wouldn't suggest most folks try that of course, but I got it done.

I am also a believer in learning on smaller machines gives you more insight into how the machines and cutters work and interact with a workpiece. But that's just my opinion of course. :)

It also helps to have machines that compliment each other. When I had my PM25, my lathe was a 8x18 South Bend. When I upgraded my lathe to a 1340GT, I wanted more milling capacity so I ended up with the 9x40 bench mill. But the quality of the bench mill was lacking, so I ended up with my PM935TS.

Now I have a mill and lathe that complement each other. :)
 

Silverbullet

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#8
If you buy one get the best you can afford. PM has the best after service of all. I'd get the vari speed and largest table and power feeds. Go once or not at all if you want new. PM will really help you. If you have 220 power or three phase .VFD Inverters are amazing for three phase changing . He has some made up with the vfd drive . YUPP give him a shot , Taiwan mills are much better then China by leaps and bounds.
 

dado5

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#9
The trick to using smaller machines is to stay within it's work envelope.
yeah, thats not my strong suit!! I would definitely be frustrated if I bought a new mill and 3 months into it couldn't do what I wanted. One option I am thinking is to just get a pm25, learn how to mill and if I eventually need bigger I can turn the 25 into CNC.
 

dado5

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#11
i went to an auction this weekend with 4 birdgeport sized knee mills. There was a Bridgeport, xlo, kondia and jet. I liked the excello the best but it seemed pretty beat up to me and I did not want to open that can of worms. When I came home I was thinking that I have never even run a mill! I really am thinking about getting a smaller bench type machine to learn on and keep my eye out for an older Bridgeport style machine. If I eventually get a larger machine maybe I can convert the bench mill to cnc. Is there a limit on size of bench mill to convert to cnc, or a tipping point of when it gets too expensive, etc..? Will a larger bench type mill such as a pm940 be close enough to a Bridgeport that I wont even want to look at them? I really don't have a clue since I have never run one before. Anyone in central Pa have one they want to show me?
 

tweinke

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#12
My advise would be to get the largest mill you can fit in your shop and budget. I think the PM 940 would be big enough to not outgrow very quick. Table size wise its about Bridgeport size.
 

mksj

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#13
The 940 should give you similar working scope to something like a 3/4 knee, so 835/935. The 833 gives up about 1" in the Y axis, and I still feel it is one of the best options in a bench top style mill. A bench top is a more manageable weight if that is an issue. So work envelope wise, I think they all will work well and you will not need to be too concerned about taking baby cuts of a smaller mill. Having had both a medium size bench top and a full size knee, there is no substitute for weight. But both will chew through metal with no issues. If you are just starting out, then used iron can often be a Pandora's box of mysteries, unless you have the experience to know what you are getting into and you have the time to rebuild it (which can be a bit of a nightmare once you get into it). When I was transitioning from a bench style mill to a full size knee, I looked at the used market, and something like a working Lagun mill in decent condition was 3-4K. Most had a few issues which would have added maybe another 1K to the pot. At the end of the day, for not much more I could buy a new knee mill. So I went with a new knew knee mill, I didn't want to spend the time rebuilding and sourcing parts (which add up quickly). It is just a matter of preference, budget and finding a decent used machine if you go that route.

So for someone new to the game without the experience and knowing what to look for and really what you want, then you can get bitten in the used market. I recommend buying new, and having a warranty. Just a matter of opinion, I have seen many hobbyist spend months rebuilding machines to pristine shape, and they enjoy the process. My hat is off to those that have the ability and patience to do so.

If you just want to learn and be able to mill out of the box, then I would look at the 833, 835, 935 or full size mill in that order of increasing price. There are also a lot of excellent full size knee mills in the 5-6K range, I went with a 9x42 knee because it fit my space needs. I did a lot of projects on my bench top mill, but the knee mill brings it up to the next level. I was fortunate to have a fellow hobbyist help me thought the decision/purchase process, otherwise I would have not been able to move the knee mill to my house.
 
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