NewB lookin for a B/T mill w/ ballscrews..

[Al_]

Here goes my first post...

As this thread entitles, I am in the market for a new benchtop mill with ballscrews for the x and y axis. I have already looked at the grizzly machines and relatives and the backlash sometime seems extreme. Because of this, I am placing a strong emphasis on ballscrews.

The machine I am looking for should be in the 24x7 range for table travel and be at least 1 hp but 110 volt only. My long term goal is to convert the machine to CNC.

The machine that caught my eye is the Jet JMD 18. I do not know if this machine has them or not. I gave their office in Illinois a call, but nobody could answer this simple question. After an hour of being on hold, I gave up and put the plan on a back burner.

Then again, I can live without ballscrews if I can build one of those nut assemblies with the tension on the nuts to reduce backlash. This might also be my only option because I do not have a large budget to deal with (low income college student).


I am quite certain that you will be able to assist me in this dillema (i'[ve been trolling here for a few months!).

Thanks
-Allan

[itsme]

Hi there,

As far as I know, you're not likely to find a standard non-CNC machine that comes with ballscrews (particularly the Chinese mills...). I would also imagine that if you did find one, it would be rather costly.

I have converted a small (Sieg X1) mill to CNC using the standard leadscrews and nuts. It has been very successful at this scale, but I have heard from many others that on the bigger machines (I would class 24 x 7 as 'bigger'), you really do need ballscrews to get the accuracy. You don't want a sloppy machine - especially a sloppy metalworking machine...

The other 'problem' with ballscrews and manual machining is that they can be a bit too efficient. There is not much resistance to stop the table moving when you are machining, whereas an acme screw won't allow much movement. With CNC this isn't a problem, as the motors provide holding torque which prevents the unwanted motion.

I have no experience with those nuts that reduce backlash, but I'd rather wait an extra few months (or years...) to save up for ballscrews, or maybe use those nuts temporarily while I sorted out ballscrews. I know they may work very well and all, but I always thought they just seemed like the 'cheap' way out (says the guy who used the standard leadscrews AND nuts... ). hahaha

Have you thought about just getting a 'standard' machine and then putting ballscrews on when you CNC it? That's what I would do.

Regards
Warren

[wizard]

Well Warren covered most of the bases with his post.

As far as the manual mills go you are not likely to find a machine with ball screws that has not been converted to CNC. As stated the reason is the acme screws will maintain position to some extent, though I have had experience were they don't hold good enough.

There are vendors besides Jet that carry the same machinery at lower prices consider going to a differrent vendor. Do shop around. If you expect to tear a machine up to do a conversion it might as well be the cheapest machine you can get. I'm not familiar with the model number of the jet machine but do not get a round column machine if CNC is in the future. Smaller, larger, knee mill or whatever just don't get anything with a round column.

If this is your first machine and the only one you are likely to have for some time I would avoid ball screws if you CNC it AND expect to also do a lot of manual milling. Stick with acme screws with some sort of backlash compensation. You do end up with somewhat of an accuracy issue but hopefully will maintain the ability to operate the mill manually without special concerns. A XY display (DRO) helps big time here.

At least initially that is what I'd suggest. You could go the ball screw route and get the additional accuracy at the time you do the CNC conversion if you feel that you can comfortablly adapt to using the CNC control to manually drive the mill around. In the long run it will pay big time to be able to use the CNC control in manual mode to control the mill.

The other thought is that you might be limiting yourself to much with the horse power and the 110V limitation. This is of course a budgetting issue just like everything else. Along with portability, if your are a college student that might be signifcant.

Dave

[Nono]

http://www.industrialhobbies.com/ These are 220v machines but they are pretty cool. Several of us have these, I like mine, Still workin on the conversion.

[Halfnutz]

I dont think the backlash will affect you much if your going to use it manually. Just replace the screws when you get ready to convert it. Since you are manually adjusting position, backlash is not an issue. Nono's right in my oppinion, if you can afford it, the Industrial Hobbie, or Ronco 45 , sieg X3 style square collum is the only way to go if you got the bucks. If not, get the Harbor Freight 33686 on sale for 799.00. If your gonna convert it, you have to do ballscrews, so dont worrry about it's backlash, the ballscrews will fix it. Also, I too have never seen a stock mill with ballscrews that was'nt a conversion. I dont think there is one. And the post about the Sieg X1 is correct too, you can get away with a Sieg X2 or X1 with the stock screws, also the Taig and Sherline, because of thier size. Of course it would be better to change them, but many have done it that way. Good luck & go get something, you wont regret it.

[Al_]

Thanks for the info.

I was talking with an owner of a tool and die shop yesterday and he mentioned that I can get used bridgeports for a very low price from a local scrapyard as long as I get to them before they get melted. The only issue here is that they are very heavy. Also, he said that I can put a smaller motor in one if I do not plan on any heavy cutting.

I do not normally plan in using a cutter larger than 1 inch and hence the 110 volts. But I wonder if the cutter ratings are for aluminum and not ferrous metals?


In reguards to the square turret mills, I'm trying to figure out which ones are and are not square turrets. I like that on that nono linked. How much do they cost?

About the lower priced machines from china, I have been looking at those grizzley machines. under 1k$, they are the cheapest machines. Unfortunately, I was playing around with the handles to the table and I had to turn one more than one time over till the table actually moved! If it was not for that, I would have already bought the machine by now.

If I could get my hands on some plans, I would build a backlash compensating assembly for the existing screws. To me, it would be the cheapest path to an accurate machine. It there is a fair ammount of resistance to turning the handles, I can live with that.

For a CNC machine, I sometimes think about building a machine from scratch. The general idea is more of a CNC router because I do not plan on cutting metal. It would need to be large enough to cut light materials (plastic, wood...) to shape what would later be used for one-off molds such as car hoods and fenders.

[itsme]

Hi Al,

If you looked at that Grizzley in a shop, I wouldn't always believe that it is as bad as it seems. Generally (at least in the UK) when they put a machine like that on display in a shop, it has basically just been 'thrown' together (often by someone with no experience on these machines). You can normally adjust a lot of that play out just by tweaking the machine and spending a bit of time on it (which you should do anyway).

Overall, I would say that the Chinese machines are quite good, PROVIDED you do set them up properly. I've been extremely happy with mine.

Just a quick thought on a Bridgeport. If you pick one up from a scrapyard, is it not there for a reason? Surely you could sell a used Bridgeport for more as a milling machine than scrap metal if it was still working? I'd be weary of a 'scrap' machine, as it could end up costing a lot more than expected if the major components are worn out.

Regards
Warren

[wizard]

Thanks for the info.

I was talking with an owner of a tool and die shop yesterday and he mentioned that I can get used bridgeports for a very low price from a local scrapyard as long as I get to them before they get melted. The only issue here is that they are very heavy. Also, he said that I can put a smaller motor in one if I do not plan on any heavy cutting.

That issue of being heavy is just one of many, but I would have to say is probably a major one for home shops. It means going to extrodinary measures to move one. One of the other issues is that the machine is likely to be worn out. This might not be a problem if you are up to a rebuild. I would have to think that auctions woud be far better as hopfully the machine has some life in it.

I do not normally plan in using a cutter larger than 1 inch and hence the 110 volts. But I wonder if the cutter ratings are for aluminum and not ferrous metals?

You can't really deduce operting voltage from cutter size! It is a question fo determining horse power requirements for the feeds and speeds you expect to get. One inch is a big cutter, something to think about.

In reguards to the square turret mills, I'm trying to figure out which ones are and are not square turrets. I like that on that nono linked. How much do they cost?

Shop around at previously mentioned venues. Note that Grizzly only has one machine in my estimation that comes close to handleing CNC conversions well and it is three phase.

About the lower priced machines from china, I have been looking at those grizzley machines. under 1k$, they are the cheapest machines. Unfortunately, I was playing around with the handles to the table and I had to turn one more than one time over till the table actually moved! If it was not for that, I would have already bought the machine by now.

New or old machine?

In any event you can not make a determination about where the looseness is based solely on shaft rotation. There could be issues with thrust bearings. The gibbs could have been tight too.

If I could get my hands on some plans, I would build a backlash compensating assembly for the existing screws. To me, it would be the cheapest path to an accurate machine. It there is a fair ammount of resistance to turning the handles, I can live with that.

You don't want to much resistance. Further it probably isn't a good way to accuracy even on a manual mill. Better to go out and get a DRO.

For a CNC machine, I sometimes think about building a machine from scratch. The general idea is more of a CNC router because I do not plan on cutting metal. It would need to be large enough to cut light materials (plastic, wood...) to shape what would later be used for one-off molds such as car hoods and fenders.

That is a very good idea! Sounds like the machine would need large Z-Axis movements, If so engineering will be a bit more involved than many of the routers describbed here for sheet goods. You will need a relatively we equiped shop to build the machine though, so you may still find yourself looking for a mill.

Thanks
Dave

[Nono]

I Must ask.. How permanant is your residence? The machines that we are talking about are upwards of a 1000lbs and that is not the little engine jack that will move it.. I had to completly dismantle mine to relocate it from the floor. After the conversion mine will have gained 150lbs. Is there anything specific that you are trying to make? A Cnc Router may be the way to go.

[Al_]

I am still living off the "ma and pa system" while I attend college. The house is large enough for a large machine shop to fit in the basement and still have room to spare.

I also understand that some of these machines are very difficult to move due to their weight and shape. Because of this, my dad and I have been planning on building a stairway to our basement from the outside. I'm guessing it would be 8 feet long, 42 inches wide, and as deep as the basement itself. My dad wanted to have concrete steps cast into the stairs, but a contractor said that they would rather dig straight down because concrete steps will crack after the first freeze and they also cost more to form. I have been insisting that we dig straight down because of the cost issue as well as the advantage of putting removeable metal steps in. These steps would allow us to lower large objects (like a full-size bridgeport) straight down with a crane or hoist.

Just a side note: I like to do metal and woodwork while my dad only does wood work. He only insists on buying large, name-brand tools which would never fit down our stairs. The stair idea is just an addition to an existing plan of digging up the back yard because our basement floods every time it rains.

I plan on living here till I am done with undergrad and then I will (hopefully) attend a school farther south (like texas or florida (wisconsin gets too cold)). I have found it to be cheaper to buy a house near some of these schools and get a mortgage rather than pay rent.

I have also been recieving a fair ammount of flak from some of my friends and family for considering such expenditures. But I was adding and comparing expenses and found that they spend more money at bars than I spend on tools.


I took another look at one of those grizzley machines this past weekend. Specifically, I was looking at their G3358


I might buy a bandsaw first.

[Runner4404spd]

don't knock the round column mills. i have done quite a bit on my bench top round column. granted the square column would be better and a bridgeport better than that. but for my buck and what i build and the limited space i have i just couldn't pass it up. btw i got a 9x20 lathe and a 4x6 band saw as well.

i'm getting ready to cnc my mill, i was considering getting a slighly bigger one but i just can justify the expense. although

http://www.wttool.com has one for $699 or 799 and its pretty comparable to the RF-31 or grizzley g1006

[Halfnutz]

Thats the mill I have and, although in retrospect I wish I had bought the square collum Ronco 45 type, for 799.00 from Harbor Freight I have been very happy with it. It does everything I need to do, it just takes alittle more ingenuity and time for fixturing and tool changing than some of the other , nicer benchtops. The worst thing about them is the chinese engine and its vibration. For around 1100.00 Jet has one with an American motor. If you want something to get started with its a great way to go, but not if your going to spend Grizzley or Ronco prices on it. The only one I'd get is the Harbor Freight on sale for 799.00. Otherwise get a square collum for around 1500.00. Just my 2 cents. A bandsaw is another awesome tool to have, for both wood and metal. I think you should go out this evening and get one of each.

One thing to keep in mind, make sure you get an R8 spindle if you get the Grizzley. That way all of your tooling will migrate up to the Bridgeport. They have a MT3 version that would be a mistake I think.