[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]

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.

[KyleH2]

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.

If I could get the machined items produced here cheaper than there I would do it in a heartbeat. I would probably still buy the welded items from there because they do a great job for a great price no American welder could beat it. ( For example an intercooler core retails for more than the cost of a finished intercooler at my cot including getting ti here and tariffs) And thats at the cheapest core prices I have seen.

I would still get a machine though. I love machining. (My own stuff. I would hate changing oil or machining some company's parts on that company's machines.) I am not a point dexter calculus student type of mechanical engineer. I am the type that likes designing things, building things, and also maintains a high GPA. Why not get a machine that can make some money in the process?

I might just put out an RFQ though as I am about ready to buy some more of a particular simple-to-machine item. Well see if some of you guys can't compete with the Chinese.


EDIT: By the way on a funny side note, it has shocked me in college how little any of the students understand about manufacturing. Out of 20 or so people I have talked to, all majoring in engineering in mechanical or aeronautical, most are second year students, not one has known what a lathe was. When I described how it worked (I guess I did a poor job of it) they asked if it was like a particle accelerator. I know its not really required to be an engineer but it seems pretty related to me.

[blackdoggy]

Another reason you might try to have it machined by someone here is the Made In USA sticker will usually allow a slightly higher cost of any said product. It's pretty sad when a student in the engineering field can't identify or understand what a lathe is, I mean how can they spec a part with out knowing what it is to be made with or on(chair).

[KyleH2]

haha and its not like they were comp engineers or sanitation engineers. Its freaking MECHANICAL engineers. I put up an RFQ for one of the parts I want made. Lets see if we cant strike up a mutually beneficial relationship.

[Caprirs]

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.

If you are concerned about your ability to troubleshoot, then performing an entire retrofit might be a little too much to bite off yet. I don't mean that in an insulting way. Since you're familiar with cars, the analogy would be you are willing to fab, install, and tune a turbo kit on a car yet you're not sure you can diagnose driveabilty issues. On the other hand, that's how you learn.

You mention wanting something rigid, yet are considering anything from Harbor Freight. Although there are a zillion brands using the same casting, it's the other bits like ball screws, bearings, turcite coated gibs, etc. that make a huge difference in quality.

I have a BSME and have resorted to being a machinist on my own after eight years of "engineering". I spent a lot of time sitting in staff meetings, generating paperwork, writing procedures, supervising, and other dull activities.

I would not consider a knee mill personally (and didn't when I bought my two mills). A VMC with tool changer, flood coolant, and enclosure is not much difference in price, but the capabilities are in a different world. The only penalty is travels compared to the knee mill.

[KyleH2]

If you are concerned about your ability to troubleshoot, then performing an entire retrofit might be a little too much to bite off yet. I don't mean that in an insulting way. Since you're familiar with cars, the analogy would be you are willing to fab, install, and tune a turbo kit on a car yet you're not sure you can diagnose driveabilty issues. On the other hand, that's how you learn.

haha funny you mention that because I did EXACTLY that at 17 but with a supercharger on a Lincoln Mark VIII. Thats how I learn :P (I joke that it would go faster than the 150+mph I pushed it too, but my balls, would not.)

I see what you mean but I have used, for example, a Sharp mill. At $7000 it was way better than ANY of the Bridgeport mills in the shop. It just overall felt better and was smoother and was easier to make good parts on. It was about 1 year old where as the newest Bridgeport was maybe 10 years old or so. Still it was probably half the price. The reason for saying this is it seems to me that a new machine that I can take apart clean and know that it has been properly maintained would be better than a 10 year old (or older) vmc that someone does'nt want or cant make money with anymore.

To keep the car analogy, while a 2008 Kia might still have less features, it will probably be more reliable than a 10 year old BMW.

I hope no one thinks I am being stubborn, arguing is just my way of encouraging more advice, new ideas, etc.

[Caprirs]

We sold my wife's Mark VIII a couple years ago. Great car except for the air bags. Never modded it. When we want to go fast, we jump in the Mustang or Capri.

The reliability factor is quite the variable. When the Kia (the car, not the machine tool) starts to become unreliable, it goes to the crusher. When the BMW acts up, you fix it. A broken VMC is worth more than a broken knee mill.

That Sharp will wear faster than the higher quality machine. Thus, a 5 year old Sharp might be as "old" as the 10 year old Bridgeport. The cheaper machine is cheaper usually because the ballscrews are cheaper, the bearings are cheaper, the ways are not as well ground. Some machines are more prone to rust than others as well. In Florida, it seems everything must be awash in WD40 to avert the corrosion.

A lot broken machines that are for sale are on the market because most machininsts cannot or will not fix them. Often, the trouble is electrical and machininsts are notoriously unsavvy about chasing electrical issues. However, most all manufacturers support their machines even after 10 years. Some parts may be expensive, but the payoff is how productive the machine can be.

[jeep534]

haha funny you mention that because I did EXACTLY that at 17 but with a supercharger on a Lincoln Mark VIII. Thats how I learn :P (I joke that it would go faster than the 150+mph I pushed it too, but my balls, would not.)

I see what you mean but I have used, for example, a Sharp mill. At $7000 it was way better than ANY of the Bridgeport mills in the shop. It just overall felt better and was smoother and was easier to make good parts on. It was about 1 year old where as the newest Bridgeport was maybe 10 years old or so. Still it was probably half the price. The reason for saying this is it seems to me that a new machine that I can take apart clean and know that it has been properly maintained would be better than a 10 year old (or older) vmc that someone does'nt want or cant make money with anymore.

To keep the car analogy, while a 2008 Kia might still have less features, it will probably be more reliable than a 10 year old BMW.

I hope no one thinks I am being stubborn, arguing is just my way of encouraging more advice, new ideas, etc.

Kyle,
the 15 year old boss style machines..... are a much different animal than a Bridgeport knee mil. you asked for our advice an it has been given.

Ballscrews to retrofit the HF mill will cost what you would pay for for a whole machine.
most of the older cnc machine are not running because the electronics quit working because of fatigue vibration ect.

My Mill has preshureized lubricant on the ways and the ways are Chrome. the mill would not run without lubricant.

so It is in real good shape.

Most of all cnc machines whicch don't run have electronic trouble (which would be fixed by the retrofit) or maybe thrust washers on the ends of the ballscrews.

all the rest of it will most likley be ok.

sometimes You have to just pay your money and take your chances.

as for 30 40 and 50 taper the styles are not interchangeable as someone previously pested. you need the corrct one for your mill and there are a few flovors.

al the man made a good point you are talking about retrofitting a machine but are worried about retrofitting a machine that has most of the work done for you......

I think you need to buy something and ask specific questions about that machine.

In a year or two you will look back and say now why did I do that =-)

archie =) =) =)

[skullworks]

Something to think twice about.

Ask around, ask anyone.

If you need a replacement part for a Harbor Freight branded machine can you get that part and how long will it take?

Manufacture support is a major concern when a business looks to aquire machine tools for production. The true cost of downtime is rarely completely counted but its more than you might think.

If you think the Tormach is too small look at a IH.

Buying all the components and doing your own retrofit will likely take over a year before it is fully up and running and the kinks worked out. This kinda makes sense for a hobby class tabletop machine as until the last few years turnkey units just were not easily available.

Edit: That other CNC Knee mill for about $10K with steppers... 50 IPM rapids - The speed of a glacier in mid summer. Please get real. ( Even the Tormach stomps that number.)

Personally I would look for a not too abused "Tupperware" Haas VF0. Also figure 10% of your profits need to go into a interest account to be ready for those costly (never at the right time) repairs that will happen, and happen more often than you expect. Edit: the Basic VF0 has 20" X axis travel, just a bit more than a Tormach, but only 66% of the IH which has 30" - But ATC, 7500rpm spindle and true Flood coolant are REAL big reasons.

Also hiring an expert to test out a prospective used machine at say $300/hr can be worth every penny.