Mills - What is good enough?

adamsgt

adamsgt

Jerry Adams
Now that I'm retired I bought a used 12 X 36 lathe to start refreshing my machining skills and am pondering a mill. The question is just how much of a mill do we need for gunsmithing? I've considered benchtop knee, square column, mill/drill, and full size. Just looked at a used Bridgeport series 1 that the guy wanted $1200 for but I would have to installl a phase converter and table drive. That would add $800 or more to the cost. Could buy something new from Grizzly for a little more. What table size is good enough? When I went to gunsmithing school I remember cutting flats on a half round/half octogon barrel with a good sized mill, but I have no intention of trying to do that now. Would just buy it already shaped from a barrel maker. I'd like to do some handgun work, cutting dovetails etc. Maybe the better question is, just what do you guys that have mills use it for? So far I can't think of anything that I'd like to do that would require a 2500 lb mill. I understand having extra capacity but you can overdo that too.

Thoughts anyone? :confused:
 
Jerry, If you have the room, buy the Bridgeport!!! Anything under $2500. is a good deal. You can never have too much travel on a mill table.

Don
 
Jerry - when you go to check out any used mill, take a magnetic base and dial indicator with you.
With the quill all the way down (machine not running), put the dial on the bottom of the quill and try to move the quill back and forth with your hand. Take the reading. This will show you how sloppy the quill is, or how much wear the quill housing has. If there is excessive play, you will not be able to do accurate work. Many of the other things on the mill can be fixed easily, but this one can be difficult & costly. Used mills can be gems, but can also be dogs.
 
I use mine for stock inleting, trigger brackets, drilling and taping for scope mounts, makeing mounts, extractor cuts. I would be lost without one, you don't need the power feed, but a DRO is verry nice. The one I have is a 9X42 step pully and I would not want anything smaller.
 
Thanks

for the replies so far. I had responded to an ad in the local paper for a CNC Hurco mill at $5500 and a Mazak CNC lathe. When I got to the place and saw the Hurco it was huge and the Mazak lathe was way bigger. They were far beyond anything I could use. The guy was having a newer larger CNC mill installed and needed to clear some space, thats when I saw the bridgeport and inquired about it. He had bought it used 4 years ago and said he only used it occasionaly in his business. Looks like it's been around several blocks or more. The table drive is toast and needs replacing.

Shiraz, thanks for the advice. I did that measurement on the spindle of the used lathe that I bought and was satisfied after using a 2X4 to check movement. What would you consider acceptable runout on the quill? 2-3 ten thousandths? Less? How about a four corner check of the table with an indicator attached to the quill? Run the table from side to side and fore and aft? Or do we not care if there is some vertical difference. One of the problems someone like me has is I know enough to be dangerous but don't know what an acceptable tolerance would be.

gunner223, I have leased a 20 X 50 unit with a rollup door and power. Room is not a problem. I just had two 220 20 amp lines installed. Unfortunately three phase is not available, hence the necessity for an expensive phase converter.

Kurt, you reminded me of how I did my first stock from a blank at school. Still have a blank that I bought then. Should be fairly stabilized after 25 years. Good suggestion on the table drive. The cheapest chinese run about $300 which could go to a good DRO instead.

Well, maybe I'd better call the guy monday and take my indicators to check it out. I'm pretty sure he can power it up also.
 
buy big

If you've got the room for the bridgeport then by all means buy it. Or a quality used copy of one. I sold a bridgeport a while back and replaced it with a used Victor. My Victor was made in Taiwan and is a better machine IMHO $ for $ than my older not so worn out bridgeport. I tried the chinese power feed and wish I'd saved my money. They do the job, but they just don't sound the same as a Servo brand. I blasted a chinese gear the first ten seconds I had it running. I put a Servo Dynamo (Taiwan quality) X axis power feed on my Victor and think it's better than the USA version. It works a little different than the standard Servo and it's clones. You can go from full rapid in one direction and flip the switch the other direction and not hurt a thing. It's got some magnetic clutch that keeps it from exploding gears. When I put a Prototrak 2 axis CNC kit on my Victor I took the Dynamo off the X axis and made a new shaft to use it on the knee. The little Dynamo can run my knee up and down all day without fail yet! Sure beats cranking by hand.
 
You could also use a static phase converter to fire up a 5 horse 3 phase pony motor for tapping your power. I use this setup to run a 2 horse lathe, 1 horse Bridgeport, and a 1 horse surface grinder. I only run 1 machine at a time so thats plenty of power for me. Would cost you maybe $200 or less if you buy a used 5 horse motor.


George
 
When you go and check the mill you dont have to check the four corners of the table with an indicator attached to the quill because even if it is out witch it probably will be you just have to adjust the head till it reads zero.

Hope this helps

Ryan
 
PhillyMachinist said:
When you go and check the mill you dont have to check the four corners of the table with an indicator attached to the quill because even if it is out witch it probably will be you just have to adjust the head till it reads zero.

Hope this helps

Ryan
Click to expand...

Sorry, but that isn't true. If you check the table with the quill locked and the head in back gear, any difference you see as you move the table IS in the ways.....you cannot correct it by "adjusting the head". If you leave the table centered and rotate the spindle (by hand) and indicate to the table and see some runout, you can zero it out by "adjusting the head".

If I were looking, I'd lock the quill, set the head to low range, and indicate from the spindle to the table. Run the table from center to the extreme left and right, and watch what happens........if the table suddenly comes up as you near the end of the travel, beware. I'd also take a good flashlight and maybe even a mirror to inspect the table ways. Look at the ways on the knee where the saddle rides. Pay attention to how hard the handwheels are to turn as the table and saddle approach the ends of their travel........if the ways are worn and someone has adjusted the gibs to tighten things up, it will cause extra drag as you move into the less worn areas. This much is still only a basic evaluation..........if the machine looks worn on the outside, it is probably pretty tired.

-Dave-:)
 
I should have been more clear I was just talking about spinning the quill and indicating the head. I never said anything about puting a indicator on the quill and moving the table, I know that that would show wear in the ways.

Ryan
 
I just received my new grizzly mill last week. I also didn't think I wanted or needed a large machine, as I am limited to 120 volt power right now. I purchased the #3102 at a cost of $1795.00, and it has a 1.5 hp motor. I am very impressed with the machine, and it seems to be more than I really need for my purposes (inletting stocks), but I am really glad that I didn't settle for a smaller unit or a round column mill-drill.

Check it out on Grizzly's website.
 
Yeah, me too

After starting this thread, I ended buying a large used mill that I'm in the process of cleaning up now.

DSCN0490.jpg
 
Butch

I bought a 5 hp rotary phase converter from American Rotary and it is wired up and just waiting on Hubbell twist lock connectors to complete the installation. Wanted a quick disconnect for the mill. The DRO display was missing and Accurate Measurement sent me a re-built Heidenhain 710 to try. This revealed that the X axis scale wasn't working. That's currently in a Fedex truck to them for cleaning and repair. Continuing to clean with Scrubbing Bubbles and Krud Kutter. Underneath the grime it looks pretty good. Was unable to find even a nick on the table. As soon a the post office delivers the Hubble connectors I'll be able to do the smoke test.
 
Mills-What is good enough?

The rotary phase converter can be built using a surplus three phase motor, capacitors and a few other electronic parts. The cost will be dependant on how good you are at scrounging parts, but you will save at least half of what you would pay for a commercial unit. The Home Machinists Digest had an article and a lot of feedback on this issue back in the 1990's and I helped several of my friends build highly successful rotary phase converters over the years.
 
You must log in or register to reply here.
Back
Top