Newbie- CNC Knee Mill Conversion (I searched.)

[KyleH2]

Ive spent the last hour or two looking for build information on CNC Knee Mill conversions. From a manual Bridgeport-like knee mill to a 3 axis CNC mill.

My budget: $10,000 for the mill ready to go, but not including all tooling.

What I want it for: Making auto racing parts to sell in my eBay store. (All my parts are currently made in China.) I am leaning towards this 2HP model as most parts I plan to make out of aluminum or mild steel and it has a little higher RPM rating than its 3HP counterpart. I will be using this to help make money to put me through college.

What I want it to be able to do: Make perfectly round circle interps, not chatter/shake and be able to take more than a .050 DOC. Optimally I'd like to put 2 or 3 parts on a fixture and run them over and over saving setup time.

My training: I am 19 but I have my OCP A-D (Full machinist certs), taught myself how to work on cars starting at 15 and am going to college for mechanical engineering. I posted here as MidFloridaTech briefly.

What I want to do exactly: I want to buy THIS harbor freight mill and convert it to CNC. I will make the brackets on it and a 13x40 lathe I plan to also purchase from HF. I will be running it off my laptop or will build a PC for it and use the Mach controller everyone else seems to use.

What I need to know:
1) I need thread that details with pictures a knee mill being converted. All the ones I saw had been taken down, pictures lost, etc. VERY FRUSTRATING!
2) I need to know if the off the shelf ball screw kits and retrofit guides you can get for a Bridgeport will be exactly the same for this mill. Is this mill an exact clone with interchangeable parts? Will the ball screws work?
3) What are my options for fighting backlash? Do I need to worry about it much with a brand new machine (this question also could be asked as, do I have to buy ball screws for it?)

Why don't you buy a BP Boss, older BP and convert it, older CNC mill or Tormach? while I have considered those, it would be difficult and expensive to hire a company to transport it here. I could buy an older bridgeport locally but the cost for a decent one usually is less than a $1000 difference between one from the 1970s and this brand new HF unit. Older CNCs might have things go wrong with them and I wouldn't know enough about them to fix them, then there is the issue of parts. Plus the issue of getting them here. The Tormach has less travel, less table, less power, etc. Its an option, but if this is possible obviously it would be much better for light production like I am talking about.

EDIT:

Just found this:

http://www.cncmasters.com/CNC%20Supra%20Knee%20Mill.htm

That seems to be in my price range. Any info on it?

[jeep534]

This is my opinion and mine alone. if you are going to do any type of production and.. are concidering a retrofit. you do not want a Bridgeprot Manual machine to convert to CNC. the issue is rigidity and repeatability. any Boss type machine can be converted with much less headache than trying to convert from a standard Knee Mill. and will be a ton more rigid. all the Ballscrews and limit switches ect are already there hooked up and working. you keep saying "get It Here" where Is here.

If the prospect of getting a boss machine and converting it is Intimidating to you then buy the converted machine you linked to. the boss style machine are out there. the other issue is time the longer it takes to get up and running the longer you are not making parts. the older boss machine had steppers and can be converted to run Mach3 quite easily.

I am doing a later servo machine which is a little more complicated....... but much less complicated than doing a full conversion from a knee mill.

also have you looked t the route 66 mills (they have a Knee mill conversion kit and conveted knee mills as well.

Just My 2 cents worth.
the bottom line is you want to do production of many like parts. weight and rigidity is your friend. now that being said the one thing you have overlooked about the tormach is it has a tool changer I believe.

a friend once told me that a cnc knee mill is 3 times faster than a Manual one and a machining center is 3 times faster than a cnc knee mill because of the tool changer. just something to think about.

Happy Hunting
archie =) =) =)

[KyleH2]

Another issue I have with buying an older machine is that I dont know that I have the knowledge to evaluate its condition. I am worried that I will purchase one and of some unknown reason it wont work or it will cost a lot to get it into fully functioning condition.

The HF mill I posted is 2600lbs, so it seem the weight is therem, but what makes you think it wouldn't be rigid? Along the same line what exactly one knee mill of comparable weight and design more rigid than the next?

I can buy the tormach's tooling system and use it in any R8 spindle if I want to improve productivity that was and have the cash. It bothers the heck out of me when companies dont list the prices of thier machines. I dont want to email you for a quote. I want to compare you directly with your competitiors quickly and easily.

That said the route 66 #4 looks like a pretty sweet (and I am sure out of my price range) machine. It says it has a #40 spindle motor. Do they mean it uses CAT-40 tools?

[jeep534]

Originally Posted by KyleH2 Another issue I have with buying an older machine is that I dont know that I have the knowledge to evaluate its condition. I am worried that I will purchase one and of some unknown reason it wont work or it will cost a lot to get it into fully functioning condition. The HF mill I posted is 2600lbs, so it seem the weight is therem, but what makes you think it wouldn't be rigid? Along the same line what exactly one knee mill of comparable weight and design more rigid than the next? I can buy the tormach's tooling system and use it in any R8 spindle if I want to improve productivity that was and have the cash. It bothers the heck out of me when companies dont list the prices of thier machines. I dont want to email you for a quote. I want to compare you directly with your competitiors quickly and easily. That said the route 66 #4 looks like a pretty sweet (and I am sure out of my price range) machine. It says it has a #40 spindle motor. Do they mean it uses CAT-40 tools?

Kyle, first of all what part of the country do you live it really does make a difference what might be available.
Point one HF at the risk of being rude it is junk for any type of production cnc work.

There are many reasons to recommend a Boss style of machine.
1 If you buy the HF machine You will have problems cncing the z axis
2 a lot of people cnc the Knee instead
3 the leadscrews will have to be replaced with ball screws and fit home and limit switches.
4 does the mill you are buying have a one shot lube
5 all in all it will cost 3 to 4 thousand to retro the "new" hf mill.

and it still will not be a production machine.

You should be able to find a non functiioning bridgeport style machine 1000 to 1500 dollars or less. I gave 400 for the lagun. and the retrofit will cost less than trying to reinvent the wheel with the HF Mill

I have just finished updating my web site

http://jeep534.smugmug.com/Hobbies
look at the retrofit pictures real close.
I am working out of town and am at a standstill right now except working on my web site =-(

it is your time and money
it is said we spend what we have sometimes it is time and sometimes it is money. and sometimes both.

as for 40 taper that is not cat40 it is probably NMTB40 like my machines are I have NMTB 30 40 and now 50

I do not know what else to say, if you want a nice hobby manual mill the hf might be ok. but it was never meant to be cnc'ed. they are two different animals..... designed much different

Happy Hunting
archie =) =) =)

[DareBee]

#40 taper is a #40 taper is a #40 taper. The difference is the holding method. Am ISA 40 has a stem and is meant for use with a drawbar. A Cat 40 is American with inch threads and slightly different flange that fits the ATC. BT 40 is Japanese has metric threads and different flange for the ATC.
The machine you look at above will be ISA 40.
40 taper is way more rigid than R8 and facilitates having tools preset for length.
If you are wanting to do PRODUCTION and want to make the most money you can per part you need a REAL VMC with ATC and rigid tapping (if tapping any holes). A standard kneemills ways are not designed for CNC production work and will wear out quickly. I would never consider production work without an enclosure and high volume coolant system as well.

IMO you should be looking for some sort of mini VMC. They start new at under 40k or for cheap - get something like the Tormach or Syil Super X4 and build an enclosure.

[KyleH2]

Thanks for the replies!

Kyle, first of all what part of the country do you live it really does make a difference what might be available.

I am located in Orlando, FL.

and it still will not be a production machine.

The "production" I am doing is a joke compared to "real" production. What qualities and capabilities do you say make up a production machine? For me its basic repeatability (ability to swap out billets of material and keeping things bolted to a fixture) to run average speeds and feeds (I know it wont really get up to the RPM I want but oh well.)

You should be able to find a non functiioning bridgeport style machine 1000 to 1500 dollars or less. I gave 400 for the lagun. and the retrofit will cost less than trying to reinvent the wheel with the HF Mill

What was wrong with the Lagun? You would suggest looking for a machine with a bad controller? How much will it cost you to retrofit it? How do you know whats wrong with it and where did you get the information on retrofitting it?

#40 taper is a #40 taper is a #40 taper. The difference is the holding method. Am ISA 40 has a stem and is meant for use with a drawbar. A Cat 40 is American with inch threads and slightly different flange that fits the ATC. BT 40 is Japanese has metric threads and different flange for the ATC.

Wow that just cleared up so much for me. So I can buy any #40 tapered holder and just change the little piece that threads into the top of it?

If you are wanting to do PRODUCTION and want to make the most money you can per part you need a REAL VMC with ATC and rigid tapping (if tapping any holes).

I don't want to do real "production" per se. I will only be doing this for 3-4 years more through college. I want to make some parts to sell on eBay and I want to keep the mill after that to do things related to engineering and hobbies. I am currently a freshman going for a Mechanical Engineering degree.

[Al_The_Man]

Most points have been covered, I would just like to add a bit to what is already said.
If you are concerned about retro-fitting, you need virtually the same knowledge and ability to convert a manual machine.
As has been said, the mechanics, ballscrews etc are already on.
The thing to bone up on is how to tell if the mechanics are still in good shape, look at way wear, and take a dial gauge if possible and do a simple backlash test, in most cases this can often be done without power.
The machine will have disconnects, contactors and power supplies and enclosure that generally can be reused
There used to be an excellent site on a quick course on assessing a used machine, but it seems to have disappeared, If I find it I will post it here.
Another thing is what power do you have and what do you need, most larger mills like bed mills will run under a RPC (rotary phase convertor off 240 1 phase) to obtain the 3 phase.
I would not consider retrofitting a knee mill and CNC'ing the knee, not if you want fairly good production rates or are considering peck drilling.
If looking at knee mills, the XLO Exello Ram Mill is considered by most, more rigid than the BP. There are a few out there that were converted to production, they have a Z quill and often power knee for rapid initial knee positioning.
Al.

[KyleH2]

Any suggestion to helping me find one in my area? I currently have an RSS feed from ebay and Orlando Craigslist that alerts me anytime any type of machinery for metalworking gets posted within 50 or 75 miles.

There used to be an excellent site on a quick course on assessing a used machine, but it seems to have disappeared, If I find it I will post it here. Another thing is what power do you have and what do you need, most larger mills like bed mills will run under a RPC (rotary phase convertor off 240 1 phase) to obtain the 3 phase.

Please post it if you can find it. I have 220V single phase. This is going in a regular household garage. Whatever I get will either have to run on a 3-1 converter or would have a single phase motor.

[blackdoggy]

Hunt online and at your local industrial auctions for Bridgeport's 98% of anything with the HF name on it is trash. One of the machine companies I have been looking at for retrofitting my 49 Bridgeport would cost me around 6 or 7K shipped to me then maybe another 1 or 2 to clean it up and put some new bearing in.

[MrWild]

I bought a Boss Bridgeport for peanuts. It had been retrofited with a "new" control sometime around 94 with servos and all sorts of goodies. Because I didn't know what I was looking at, the bunger got inserted hard and deep. The ways were "ok" but the head was trash and the ballscrews were junk. I lost money getting rid of it and buying something newer, and with much less wear. I'm fairly happy now mechanically. It'd be nice to have a new control, but not needed, and I've amassed the parts to upgrade the control to EMC2 with MESA Electronics control boards.

You are right to be wary, but you really need to make sure to get box ways, and a machine that is already CNC. There are still some very low hour pristeen examples Tech colleges are parting with. The right one would be worth the shipping expense across country. You wion't be happy at all with the HF example down the road. New junk is still junk. Sometimes just because you can and know how to do something, doesn't mean you should.

[KyleH2]

Everyone talks about what crap tools that HF has. I can honestly say that 90% of their stuff that I have bought have worked great. The stuff that didn't I returned with no problems and was stuff I suspected of being crap. Like their cordless electric stuff. That is neither here nor there. Their mills aren't made by them, they are likely made by a major Chinese manufacturer and probably the same as the larger grizzlies.

It is probably worth mentioning that I probably will not ever need to hold more than +/- .001 on any dimension. Probably wont even need to hold that. I am talking about building cosmetic parts, and stuff thats going to get welded on or bolted together.

If I want a small machine to hold +/- .0001 on I would take up Gosinger's 4.9% offer on a Hurco VM1 Mill or TM6 Lathe. But they cost $30-40K + interest, and although they're great machines and I enjoyed using them both at tech school, I can't afford one as part of a business plan.

This machine cant be one that takes a year of 12 hours a day of operation to pay itself off. If it is I don't need it, I will get my parts manufactured overseas rather than make them myself.

I have read a little bit about what box ways are, but what machines do not have box ways?

I would love to have either of the mills my local tech school does. But the only way that is happening is if the school shuts down.

[blackdoggy]

Instead of doing it your self and buying machinery or shipping it over to China why not get one of us to do it for you? Most every one here has modern machinery and most can run circles around the Chinese. I give you credit for having the skills and desire for your own equipment but if some one else has everything and can do it better, cheaper, and faster than China why do it yourself or ship it? You still need to understand any machine you get even something as old as I have still needs to generate enough product to keep you fed. If you take chances with Chinese machines chances are you might end up eating dinty moore instead of eating steak., You run less risk using older brand name American machines than China discount brand I mean can you call up HF and get a part in less than a week where as if you need most any part for a Bridgeport you can have it in your hand the next day.