Milling Machine

[Nick1911]

So I'm looking into buying a milling machine.  I have a lathe, which has worked out really good, and I LOVE working with metal. So I *think* a mill would really expand on what kinds of things I can do metalworking.  I don't have a lot of money right now, so I'm just window shopping, but wanted the opinions of APS.

The one machine that I really like is here:
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=42827

I think it would be rigid enough, and has plenty of travel.  The price really isn't that bad, and I could get it locally. (no shipping charges)  But I dont really have $1000 to spend on equipment, and it wouldnt come with any tooling.

I would consider something more like:
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=44991

But I'm concerned it wouldn't be rigid enough, which would make it pretty worthless.  Less cross-slide travel isn't a huge issue, but rigidity definitely is.

My other option is the used market, although I haven't found ANYTHING used for sale around here.  I would have thought that I could buy an old one from a factory tool room or something pretty cheap ($500ish), but no avail.  Maybe I'm just looking in the wrong places?  If anyone here is looking to sell a mill, let me know! :-p  Used tooling might also come with some tooling, which could add up to big savings.  I dont mind using big iron from the 40s.  All I ask is that it use single phase power.

What is your opinion?  Do we have any professional machinists here, or other hobbyists?

Thanks

[cfabe]

Forget the harbor freight junk. Shop around for a used mill, you're right if you're lucky it will come with tooling too. I'm not at all an expert so I can't reccomend machines to look for or where to look, but they are almost all going to be 3-phase machines. You will need to invest in a phase converter or build one yourself with a spare 3-phase motor.

[Leatherneck]

Grizzly Industrial has pretty good tools over a wide range of sizes and cost. I've got a contractor's saw and a 12" planer of theirs that have lasted for years. They even feature "28 milling machines right on their home page.

http://www.grizzly.com/

TC

[Marnoot]

While I can't speak on machine tools specifically, I second avoiding Harbor Freight if you're looking for a long-term quality item. I consider them a peddler of "disposable" tools, and only buy from there with that in mind. Even their simple tools, like screwdrivers, sockets, etc., are poor quality, often made from soft steel that just can't hold up to normal use. I've bought the occasional thing there that has held up surprisingly well, but it's a bit of a crap shoot. If you need some tool for one or two uses they're a good option, but not if you're buying for long-term use.

[m1911owner]

Regarding using 3-phase equipment, there are reasonably-priced Variable Frequency Drives (VFD) that take single-phase in, and produce three-phase out.  You just set them at 60 Hz and don't use the variable frequency feature.  (Unless you want to--it might come in handy).

These are availabe up to about 3 hp in single-phase-in versions.  Above that, they need three-phase power, too.

Google "Variable Frequency Drive" to find various makers and sellers.

[Shalako]

I was lucky enough to get trained on a Bridgeport mill at a one man factory when I was 17.  That was one awesome peice of equipment. It must have weighted a ton though, so that might not be what you are looking for. In college I later learned the importance of matching the cutter speed, drive speed, and cutter rake angle to the softness/hardness of the material you were cutting. I'm sure a good textbook or reference book would have that info as well. Also learned that drill bits don't make round holes, that's what a reamer is for.

Metalwork is extremely gratifying and I hope you wind up with a great mill.

ps. you will also need to buy an s-load of dial indicators and micrometers to insure that your work is true and the cutter head is square to the work. thats a biggee for tolerance machining.

[brimic]

Try Ebay, there usually is a large number of lathes and mills for sale cheap there, the only obstacle is arranging the shipping or having to pick the machine up yourself.

[dogmush]

Nick, did you ever get a mill?

There's apparently a whole cottage industry in upgrading the Chinese copies of an X2 into a useful machine.

I can get that HF X2 clone for about $425, and upgrade it over the winter.  I'm considering taking the plunge and seeing how much precision i can get put of it.

[French G.]

State property auctions are where you buy full sized mills in great shape for around scrap value. My dad liberated several very nice machines from community college property auctions.

[Nick1911]

Nick, did you ever get a mill?

There's apparently a whole cottage industry in upgrading the Chinese copies of an X2 into a useful machine.

I can get that HF X2 clone for about $425, and upgrade it over the winter.  I'm considering taking the plunge and seeing how much precision i can get put of it.

I did.  I bought a Rong Fu 31.  At the time, it cost around 1100 bucks from Enco.

I was in college, and had it shipped to my parents place.  My dad was not thrilled when a semi arrived with a delivery for him.    Hard to move around palatalized freight without at least a tractor or something.

I've had it for a while now, 7-8 years.  There have been a few issues that I've had to correct with it, and it definitely has limitations particularly with z-axis travel - transitioning between jobber drills to end-mills almost always entails moving the mill head up or down the column, which requires rezeroing [round column mill].  And that's actually a big PITA if I'm really tackling a proper machining project.

By fortune, I ended up with a bucket of old end-mills, and a chest of Starrett indicators.  The indicators are absolutely essential for machining.  I would have been floundering without them.

Even with limitations, I'm glad I bought it, and I've used it to make and modify countless things.  It was worth it for that alone.  More importantly, I've learned a great deal about real world machining by using that machine to make chips.  That mill - with it's limitations and challenges - helped me a great deal and I'm glad I bought it.

That said, when I move to a more suitable place, I will buy a bigger mill, and outfit it with at least DRO.

Everyone says "buy a Bridgeport", and there's certain wisdom in that.  But the mill you can afford now will help build your skills now, so someday when you can buy a Bridgeport, you have the background to fully use and enjoy it.

The X2 looks interesting.  What kind of mods would you do?  What kind of precision can be expected?

[dogmush]

From what I gather, you need to stiffen the column/base joint to add some rigidity. That's mostly done by bolting a big plate or channel to the back of it.

Then a belt drive to remove the failure prone plastic drive gear.

An air spring conversion instead of torsion spring to support the head. At the same time you can mod the Z-axis track to give you another couple inches travel.

Then a DRO setup so you don't have to worry about backlash on the table. Although while I'm there there's a mod to take out most of the backlash anyway.

With some carefully traming and adjustment of the gibs folks have reported getting the X2 clones under .001" accurate for it's whole range. Then it's just a matter of going slowly so as not to over tax the mill.

I have a Bridgeport at work that I use pretty frequently,  but do both to changing politics at work, and the nature of my personal projects, using it got personal projects is getting sketchy.  I'd love a 9x42 or so knee mill, but I don't really have room for it, nor realistically am I going to pay that much.  I'd be less then $900 all in when I finished the mods and have a pretty nice, but small, mill. Big enough for firearm receivers and slides however.

[dogmush]

This guy has gone full in with his X2.  I2's a CNC, with auto change tooling and flood coolant.  not to mention an articulating head, engraver, 4th Axis, and some other stuff.  It seems like overkill.

I've supposedly been saving for a bigger Grizzly mill for a while, but the money keeps ending up going to house repair, or another project.  I had ignored the mini mills on the theory that they are cheap chinese crap (which they are as shipped), but as I read what folks are doing to them, and getting out of them with some sweat equity in the machine I am thinking it'll do 85-90% of the projects I need done.  Plus it'll fit in the space I have for it.

~$450 for the machine
$200 for the DRO display
$150 for the DRO scales
$100 for drivetrain and Z-axis mod kits

Some machining, some time, and you get a pretty nice machine.  Some guy on arfcom used one to go from a chunk of billet to an AR lower.

Also, everyone says estate sales, auctions and used for good deals, but I've been going to them for a bit.  Around here people know what machine tools are worth.  Yeah they are cheaper, but you aren't going to touch an American made knee mill for less than about $2000 unless it's beat to hell.

ETA: That RF 31 looks like a nice machine, but it's $1500 now, and I'd still want a DRO.  Since you mentioned DRO's, check out www.DROkits.com  They have a nice display and scales.  although if yo are planning an upgrade, some cheaper igauging scales and save the nice one's for the new mill.  Also This Guy has an open source Android based DRO project going that is probably the cheapest if you have the skill to build the controller and an old tablet lying around.

[HankB]

Necro Thread!!!

. . . I bought a Rong Fu 31 . . .

You know, I thought you were kidding, but then I checked . . . . . Rong Fu really is the name, not a Chinese language joke.

At least, not an official joke. 

I own a Chinese-made 7x14 mini-lathe I've worked over and tweaked, so I think I have some idea of the challenges you faced getting your mill up to par.

[birdman]

Actually, I have a mill question, I need a little mill and lathe, and was looking at the sherline CNC ones.  It seems like they are superior to the Chinese little ones, obviously, not as good as a big one, but for small (less than 6" square stuff on a mill, less than 1-2" dia on a lathe, and almost entirely aluminum work, they seem okay), and have gotten some good reviews.

Any thoughts?

[dogmush]

Rigidity is going to be the issue.

CNC is operating at faster speeds, and even the US mini mills were originally designed as a manual, then converted to CNC. So once sped up, vibration and flex can be a problem. Not necessarily will be, but can be. I would plan on having to brace up and add rigidity to any "benchtop" size mill just for normal use, much less to run CNC at any useful speed.

Side question: Are you running large runs of the same part? Because CNC (as opposed to a DRO equipped manual mill, or a manual power feed) really only shines at lots of repeat parts. The machining is faster, but you still have to write the program. Our big mill at my shop doesn't even have a DRO,  just power feeds, and for one or two of the same part I can generally beat a CNC mill I  production time. After two it starts to depend. More then 5 and the CNC almost always catches up. (I have actually raced with the navy guys that share my center. They have a 9x42 CNC mill. And a better budget.)

[DustinD]

www.cnczone.com is a great resource for small or home CNC projects. Also www.practicalmachinist.com