What are the size limitations of mini mills?

Hi all,
In researching mills, I'm stuck between the possible need for a larger mill and the convenience/size of a mini mill. I realize that I'll have to stay within the limitations of a mini mill, but despite my searching the NG, I can't find any post that quantifies the limitations. IOW, is it possible to say that for a certain mini mill that one will only be able to work on a piece so big or take cuts so deep? Or are the capabilities entirely dependant on what you're trying to do to the specific piece and type of metal?
Obviously, I'm new to this and have a bunch of books coming. I'm just trying to decide if I can get by with a mini mill or if I need to buy an RF-30 machine. I have a very small garage into which this stuff will have to fit, along with the car du jour.
I'd like to make pieces for automotive and motorcycle projects (brackets, pillow blocks, component mounts,etc..) mostly out of aluminum but some out of steel. Most of these pieces would FIT on a mini mill table but I'm getting the feeling that the mill might be out matched. Are there any general rules of thumb that suggest the maximum size (% of table, % of X,Y,X travel, HP x phase of the moon?) or capabilities of a mill?
Thanks,
Peter

I've been looking for a while too. One of the biggest boo-boos I've seen with mini mills is that they usually have a round column. That coupled with the short quill stroke makes it difficult to go from a spotting drill to a jobber length drill. Look for one with the table dove-tailed into the column or a square column so that the table can be raised or lowered without turning. gl, John
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Peter Grey wrote:
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I've got a mini-mill, the one that sells for $499 or so. I use it mostly for CNC demos. It has a 4" Y-axis travel. That is most likely the biggest limitation. Other than that, it has plastic gears in the head, and is awfully flexible for a machine tool. Mechanical flex, I mean, and that is not good!
Jon

I'm in the same boat, made worse by just having sold my Van Norman #12 before moving. I don't have room for a full sized mill.
I've had a mill-drill and wouldn't do it again. The round column (inability to change height without losing your position) and the lack of rigidity are real problems. I'm also suspicious that the screws don't wear well (mine was used and worn). I'm looking at a Clausing 8520 or a Millrite (used).
You might try digging around in the Yahoo groups and see what they talk about. Here's the one for Clausing: http://groups.yahoo.com/group/clausing_lathe_and_mill/messages/1601?viscount 0 There is probably one for Millrite, I don't know about Rong Fu. Another useful site: http://www.lathes.co.uk/ has decent descriptions of many machines.
Steve Smith
Peter Grey wrote:
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My personal opinion is to stay away from miniature machines for projects the likes of yours. I'd also avoid, like the plague, mill drills, unless you budget simply can't stand the cost of something better. It's RARE to find someone that is satisfied with a mill drill if they're using it as a milling machine, not a drill press.
There are small knee type mills available, which would be a far better choice, based on your suggested usage. Gorton, for one, made some that are small enough that you sit to run them, and Gorton is an outstanding builder of drop spindle type mills. I'd recommend one of their machines highly. There are others, too, of varying sizes, so I'd suggest you keep your eyes open for a "deal"and buy something that is much better suited to your needs. If space allows, though, I think a Bridgeport or Bridgeport clone might be a fine choice due to the flexibility of the machine. For the most part, no other type vertical mill offers all the features that they do in one machine. That's why Bridgeport was such a grand success, along with the cost, which used to be very reasonable.
A friend of mind has a mini-mill, CNC controlled. He's very happy with it, but he's machining wax to make patterns for investment casting. The rigidity of his machine would fall short, VERY short, of enough for satisfactory machining of most any metal. In machines tools, rigidity is everything. That's why they weigh so much.
Harold

On Sat, 8 Nov 2003 11:51:49 -0800, "Harold & Susan Vordos"
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(puts hand up -- me me ! :-)
I've had an RF30 for about four years now and it's served me well.
True, it's got limitations compared to a knee mill but I've done an awful lot of work on it and it has done everything I have asked of it (bearing in mind that I am aware of its limitations).
For me the choice was to buy an RF30 and have enough money left over to get some decent tooling, (rotary table, vice, clamping set, collets, flycutter, boring head, inserts, milling cutters, etc, etc) -- or to buy a knee mill and just spend my days looking at it and wishing I had all the accessories needed to use it.
One should always remember that unless you're planning to use your mill for production work or your income depends on it -- *any* mill is better than no mill :-)
You can always sell a mill-drill later and upgrade to a *real* mill if you want/need/can-afford to -- and then all that tooling and other bits you bought can still be used.
-- you can contact me via http://aardvark.co.nz/contact /

I agree. I could spend a year looking for the "right" mill and not be able to do anything in the meantime. If I buy an RF30 or mini mill or whatever, I'll have the opportunity to make some stuff, experiment, and then buy something better if I determine it's what I need. In the meantime I will have learned a lot about machining and about what I prefer and want.
I understand that drill/mills aren't perfect, but there seem to be too many people on the web that are using the RF30 and its ilk successfully (while keeping in mind its limitations) to buy into the "mill/drills are useless" argument.
Thanks,
Peter
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I agree in principle with each of you, but practical experience is a great teacher. One of the hard lessons learned in life is buying something that is ill suited to a job, then trying to liquidate it in order to replace it with a tool that is better suited. The better investment would have been the proper tool to do the job at the outset. Often times the money is gone and the tool simply can't do the job at hand, and has poor resale value, if it can be sold at all.
My point is that if a person buys a mini-mill, it is woefully underpowered and, in general, not really equipped to make parts, regardless of the fact that they can be placed on the machine table. For example, how about drilling a ½" or larger hole in steel? Seems like that would be one of the things Peter would encounter in his quest to build his projects.
When it comes to a mill drill, I recognize that they are better than nothing, but they are, at best, a poor compromise for a reasonable milling machine. The problems with mill drills have been well addressed, and addressing them yet again in this thread serves little to no purpose. Resale value isn't great, but then buying new is not all that expensive, either. I accept that fact that for those that are limited economically, and perhaps have no prospects of anything better in the future, they are better than nothing.
Regards the argument about being satisfied with one, one of my friends, a retired tool and die maker, owns one, and built his 1½" scale model steam locomotive with it, along with countless other projects. He's a patient person, willing to make the necessary sacrifices in order to achieve the end result. I respect him for that, but my time is far too valuable to spend it spinning my wheels endlessly, and achieving a less than acceptable end result because the machine simply doesn't have the necessary quality built into it. I guess it all depends on the nature of the work you intend to do, and the quality level that you find acceptable.
I used my Bridgeport for gain, mostly building tooling for the aero-space industry. I consider it the absolute minimum machine one could own and get reasonable results. I do not look at the Bridgeport as a great machine, but, like in your case, it was the minimum I found acceptable in order to accomplish my mission. No way in hell could I have done my work with a mill drill. Maybe now that I'm no longer working for gain I might see it differently, but I still have the Bridgeport and wouldn't give the idea a second thought as long as I do. I still do not recommend mill drills, and for many reasons.
Harold

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A better financial investment perhaps, but I'm not concerned enough to have this be the only consideration. If I have to sell the mill/drill if I find something better, I will. I don't mind spending the time required in order to educate myself about which small used higher-quality machine will work, is in my price range, is truly small enough and is being sold by a source that I trust or is close enough so that I can look at the machine. While I'm doing that, I can be making things (or trying to) and learning on an RF30, which is a known entity.
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I've come to the same conclusion.
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It's not a matter of being limited economically with no prospects of anything better (Jeez, that sounds depressing). I'm trying to find a reasonable entry point into this "hobby". I've been heavily involved with - and taught - bicycle racing, music, car racing and other things that require equipment. I didn't buy the "best" equipment when I got into them because I didn't know if I needed it, and what my level of long term interest and competancy was going to be. I believe that there is a point of diminishing returns for most things. I'm not yet convinced that for my needs, the Bridgeport is the point of diminishing return.
I'm a jazz musician and there a ton of players that believe that one needs a $8,000 guitar in order to make good music. My 30 year old $1,500 guitar feels and sounds like a $8,000 guitar, but I wouldn't have recognized this guitar had I not owned and played a lot of other guitars. Those guitars weren't what I wanted ultimately, but I learned a ton by playing them. I'm sure that the equivilent of my guitar exists in the mill world. But I don't yet know enough to recognize the used mill I need when I see it. Maybe after hacking around on an RF30 for a year or so, I will. Or I may be satisfied with what I have. BTW, I've got a bunch of guitars, all with different purposes. You can never have too many - it's just like machine tools.
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I'm not going to be making my living at this and I don't think I can fit a Bridgeport in my garage. I live in San Francisco and my house was built 90 years ago. Garages just weren't a priority. There may very well be a small Bridgeport or other high quality mill in my future. Using an RF 30 will play an important role in learning enough to make an intelligent choice on the "point of diminishing return" machine - assuming that for me the RF30 isn't it.
Regards,
Peter

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What you want is a solid mill, inexpensive, that fits into a small shop - with a small footprint and low overhead. Bounus points for high quality and a 'name.'
I would suggest what I chose for a similar application:
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This machine looks like hell but it just won't quit cutting metal. Total cost from a used machinery dealer was $800 about ten years ago. It had been pretty well abused and I had to replace the handwheels, and make a new feed nut for the table. But after cleaning it up it's been a strong worker in my shop and does not require much attention at all.
The latest chip-fest involved making a specialized puller for removing a timing gear from a vintage motorcycle crank. The correct puller would cost about a bazillion dollars if one could find one for sale, and they're not for sale. So I had to take some chunks-O-steel and build two blocks that would get under the gear, in the limited space. Then I had to drill mating holes in a steel ring to hold them, and allow a puller to grab. The thing worked first time, and it was all hogged out, rough and ready, on the horizontal. The limiting factor was how tightly the small vise would hold the parts - early on in the project I realized that a part rip-out was entirely possible.
You can find machines like this, in much better condition than the one I bought (I have a soft spot for 'wing-down' stuff) for a bit more money. Watch on ebay and you do sometimes see them go by.
Jim
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Jim, do you happen to have a parts break down for that Hardinge Tm? I have most of what I think is a UM sitting in my trailer at the moment..it followed me home last night...
I have the mill, no power feed stuff, the table, one hand wheel, no lead screw and the brackets are missing along with the bearings on the side to side axis.
Once again..someone took something apart to clean and paint..and lost parts, then lost interest. Its damned nice looking now..with a sorta tourqoise paint job..but incomplete.
Id like to complete it, but need a blowup diagram to see whats missing. These mills are about the only Hardinge machines I dont have manuals or access to manuals for.
Gunner
"By calling attention to 'a well regulated militia', the 'security' of the nation, and the right of each citizen 'to keep and bear arms', our founding fathers recognized the essentially civilian nature of our economy. Although it is extremely unlikely that the fears of governmental tyranny which gave rise to the Second Amendment will ever be a major danger to our nation, the Amendment still remains an important declaration of our basic civilian-military relationships, in which every citizen must be ready to participate in the defense of his country. For that reason, I believe the Second Amendment will always be important." -- Senator John F. Kennedy, (D) 1960

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Gunner, check the Hardinge-Mill Yahoo group. There's one in the files section.
Pete Keillor

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I hate when that happens. Well, OK. Not me. *She* hates it....
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I thought you needed one and got it, a while ago. It will take me a day or so to copy the one I have (which is actually a copy that one of the hardinge folks sent me) and I could pass it along to you.
I think I have your address at work.
Jim
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Gunner,
I have parts breakdown/schematics for what I believe is a Hardinge auto chucker. Has sections for console, hydraulic, programmer, drive headstock, carriage, vertical slide, etc. Seems to be everything but the cover and first couple pages. I have no use for it, maybe you do. Send your snail addy if you want.
michael

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I sent a note or two to your lightspeed account. If you did not get those today, drop me a line.
That mill really does work fine without the power feed. Not all of them came with it. The handwheels can be replaced inexpensively by rough castings from mcmaster carr or MSC. The leadscrew however would be a toughie, along with the endplates for the long axis.
My machine had a power feed 'event' which apparently had ripped the end off the non-handwheel end cap, and knocked a chunk out of the table casting slot where the stops for the feed setup slide.
And somebody took the time to mill out the boo-boo, and sister in a chunk of steel to repair the table, and carefully piece the end cap back together.
I had to buy the thing when I saw that.
Jim
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Hmm. Could you please send me your mail address then, to the jrr(zero) email in my sig line? That way I can compare with the one I have on file, and see if the parts breakdown is headed in the right direction....
Jim
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This is a horizontal mill, yes? My understanding was that they're not as versatile as a vertical mill...?
Maybe I should try to find a used machine tools dealer in my area.
Peter
Peter Grey
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Horizontal mills are as versatile as vertical mills, but are more difficult to do some things with. On the other hand, they do some things better than vertical mills.
Depending on your application, they both have strengths and weaknesses. I have two verts and one horizontal, and find myself using the horizontal more often than the two verts combined, some months, and visa versa in others.
I also use the heck out of a shaper.
Gunner
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"By calling attention to 'a well regulated militia', the 'security' of the nation, and the right of each citizen 'to keep and bear arms', our founding fathers recognized the essentially civilian nature of our economy. Although it is extremely unlikely that the fears of governmental tyranny which gave rise to the Second Amendment will ever be a major danger to our nation, the Amendment still remains an important declaration of our basic civilian-military relationships, in which every citizen must be ready to participate in the defense of his country. For that reason, I believe the Second Amendment will always be important." -- Senator John F. Kennedy, (D) 1960

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Right. The spindle axis is horizontal. The spindle has no 'quill' which is defined as a movable section that slides in and out of the casting. Most horizontal machines (here we are leaving out the aceiras and deckels because they are basically lear jets) don't have a quill the way vertical ones do.
Folks use the quill in a bridgeport type machine to drill, mostly. So it becomes a super-solid drill press, with really slow back gear speeds - so you can run honking huge drills in it, with the drill held in a collet so it won't slip.
In a horizontal, any drilling gets done with the X (in and out) axis handwheel, so it's a bit cumbersome. My solution to this is to either a) spot the holes in the horizontal with a center drill and transfer the part to my dril press and finish them off there, or b) simply lay the holes out by hand, centerpunch, and do the whole job on the drill press, for low accuracy stuff. The puller I just made had *all* the holes done right in place on the horizontal, and I was glad to have the slower speeds available there because it was a stainless ring I was drilling.
Just about the only time I put the vertical head on this machine (which in this case is a bridgeport M head, adapted to it) is when I need to mount a rotary table on the machine, and machine downwards in towards it. I have the vertical head, it almost never gets used, in spite of its having a quill.
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This could be a good idea. Where are you located? You should be going to places like this just to see what they have, what's available. Don't express any strong interests in any given machine, just see what's out there. It's kind of like used car shopping. Sometimes something just jumps right out at you.
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I'm in San Francisco. There are some listed in the fone book, but if you had suggestions or recommendations... I suppose they don't need to be local - just trusted.
Peter
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