[Randall]

Its strange that there is no comparison with the Tormach as its seems to be its closest rival.

Regards
Phil

Do you mean the IH site
Ahh what do you think he is comparing it to.
Randy

[philbur]

The specification on page 118 of the Tormach manual identifies the ballscrews as precision ground ballscrews ISO/DIN P4

Regards
Phil

[philbur]

The original statement of none comparison to the Tormach was Richards not mine. Read the quote in 18#. I didn't check to see if he had read it correctly I took it at face value. I've now had a look at the IH site and I can't find a comparison with any other machines at all.

Regards
Phil

Do you mean the IH site
Ahh what do you think he is comparing it to.
Randy

[philbur]

I think you are miss using the calculation as in both cases you are overloading the cutter. The two key controlling parameters for a cutter are surface feet per minute and tooth load. Go above either of these by to much and you will quickly destroy the cutter. You should start with these as fixed and determine the other parameters base on these. So in your example, for the cutter you identify, assuming it is HSS and a workpiece of 6061 aluminium then the approximate recommended (in a commercial environment) is 250 sfm and 0.002 inches/tooth. This gives 1,900 rpm and 8 ipm. and 0.5 hp. As the IH is only good for 1600 rpm the Tormach marginally wins this competion. If you are use smaller cutters or carbide then the Tormach would run away with it. What you should not do is turn up the tooth load until you are using all the available horse power.

Regards
Phil

Jeff,

I checked Robb Jack's Speed and Feed Application (see the www.gensa.com to use his excellent program on feeds/speeds/chip loads/hp, etc.) and it shows that a 2-flute, 1/2-inch cutter cutting 1/2-inch deep and spinning at 1,600 RPM can move at 16-ipm while consumming 1-hp and giving a chip load of 0.005. Using the same equation, but increasing the spindle speed to 4500 RPM, gives a chip load of 0.001778 - which is smoother, but more likely to fry the cutter in a short period of time, at least if having a 0.005 chip load is necessary to carry off the heat as well as give a reasonable finish. Interestingly, the hp requirements are the same.
.

[MAX711]

FWIW I have an IH mill that I converted to cnc with servo motors, Gecko drives and ground ballscrews. I didn't use Aaron's cnc kit so can't comment on how it performs. Long story short, at the end of the day I have a functioning cnc machine with good working envelope and reasonable accuracy but had the Tormach been available at the time that's what I would have spent my money on. I have sunk almost as much into my IH cnc as a Tormach would have cost and it's probably still not as good and took me far longer than I wanted. Unless you enjoy building a machine from scratch or need the extra working envelope, the Tormach would be a better solution. As I see it, it comes down to this, if you want to make parts right away and with little fuss, go for the Tormach. If you don't mind starting with some basic cast iron and investing the time and skill to coax it into a reasonable cnc machine then go with the IH + cnc kit option. One other comment, don't underestimate the electrical work involved. It took me as long to create and wire the control cabinet and connect all the motors, drives, limit switches, encoders and safety circuits, as it did to do all the mechanical alterations. It would be nice to see IH offer a turnkey solution like the Tormach, if it had the same features and ease of use, the larger envelope would be worth a premium. Just a few observations as an IH owner.

[Richards]

Fellows, I'm afraid that we're almost getting into a pissing contest. That was not my intention. I'm sure that both the IH and the Tormach are good machines, in fact, I believe that both mills are capable of producing better parts than the casual operator can honestly expect. With that said, I am still very uncomforable with some of the claims made either for or on behalf of the Tormach mill.

1. Ball screws - ground, rolled or? You'll have to decide for yourself. I called four ball-screw manufacturers today here in America giving the basic axis travels listed by Tormach and then asked for a ball-park price for GROUND ball-screws with P4 specs - including nuts, journals, bearings, etc. so that the whole assembly would conform to P4 specs. Make the calls yourself, but be ready to be shocked, both because of the price and because of the lead time involved. Given the fact that I'm comparing American made vs ball-screws made in China, perhaps I'm comparing apples to oranges; however, I think that any of us can look around our shops and compare many pieces of equipment that are made in the U.S. or Europe compared to the 'same' pieces made in China. In particular, I have four calipers, three of which were made in China and one that was made in the U.S. Although all four give almost identical readings (closer than my old eyes can tell), the look and feel of the U.S. made caliper is vastly superior to those made in China - and the cost is vastly higher too. I also have six drill chucks with five being made in China and one being made in the U.S. Three of the chucks are total junk. They were furnished with various pieces of equipment. Two of the remaining chucks are good within 0.004 - which is not too bad for drill press work. One, the one made in the U.S. is good within 0.0015, which means that I'll use it as often as possible to keep from boring and reaming low tolerance holes. If you're going to spend $7,000 - $10,000 for a CNC mill, do yourself a favor and spend $20 on telephone calls and talk with unbiased outsiders who sell component parts similar to the parts used in the machine of your choice.

2. Stepper drivers. Okay - I'm really biased on this one. I've saved copies of 'satire' against Mariss at Gecko. I'm also aware of 'differences of opinion' between Gecko and the manufacturers of the drives used in the Tormach. That being said, I've drawn my own conclusions about the merits of the claims made by both parties. I will not post the satire on this forum, because I'm certainly not sure that it was ever meant to be viewed by the general public. It's easy enough to find on the caches of various servers on the Internet. But this much I will say: when the defacto standard in stepper drives is Gecko, and someone uses something else on an 'above average' CNC mill, I have to wonder why.

3. Spindle speeds, feed speeds, & chip loads. I'll have to go with the manufacturers' recomendations on this one. Use the calculators furnished by several manufacturers or, better yet, call the tech rep representing your favorite cutter and give him the specs of your machine. Let him/her recommend the feed speed, chip load, hp requirement, and expected life of the cutters he/she sells. As far as having the cutters 'overloaded', as was claimed earlier, all I can say is that the manufacturer of the cutter recommended particular cutters given the spindle speeds, feed speeds, available hp and desired depth of cut. The manufacturer was willing to stand behind his recommendation. That's good enough for me. Several cutter manufacturers recommended 0.005" chip load as being optimum for roughing cuts in 6061 aluminum and then 0.001 - 0.002 for the finish pass. When contacted, they all said that defaulting to 0.002 for roughing passes was impractical if I wanted both speed and cutter longevity. They're in the business of selling cutters - to repeat buyers. I assume that they know what they're talking about.

4. VFD vs 1-phase 220vac motors. Given my choice, I would add a VFD and 2hp motor to my IH mill and consider the $500 well spent. However, I do not feel handicapped at all owning a mill with a top speed of 1,600 RPM. Using feed speeds, RPM, depth of cut and proper cutters, I can get excellent cuts with a non-VFD motor. I can also be assured that advertised hp is actual delivered hp. Sad experience with several Porter-cable 7518 routers opened my eyes to the embellishments that advertising departments add to the actual obtainable results of their equipment. Buying a VFD and 3hp Colombo spindle showed what a VFD/spindle can really produce - especially when the speeds are held within the constant torque range of the spindle. Not knowing what to expect from the Tormach VFD/motor combination just adds another question to my list.

Lastly, the old admonition still rings true to me - if something sounds too good to be true, it probably is.

[MAX711]

Not trying to fan the flames, but ground ballscrews are not that hard to find. Try www.misumiusa.com You can size them, specify end machining, get an instant price and delivery within 6 days. All from the comfort of your mouse

The great thing about ballscrew specs is that you either meet the spec or you don't, there's no ambiguity.

The Misumi units are from Japan (not China, before anyone starts into the China vs USA rant), although I think they are manufactured here in the US. They are ground, not rolled and a P4 spec with 30" of travel costs about $500. That may seem like a lot, but I think the ballscrews have the greatest impact on accuracy (unless you've got really bad cast iron and a lot of flex).

[Randall]

The original statement of none comparison to the Tormach was Richards not mine. Read the quote in 18#. I didn't check to see if he had read it correctly I took it at face value. I've now had a look at the IH site and I can't find a comparison with any other machines at all.

Regards
Phil

Phil
You have now asked about it twice. Home page, CNC comparison.
Randy

[philbur]

Thanks for that. I just couldn't see it for looking.


Regards
Phil(chair)

Phil
You have now asked about it twice. Home page, CNC comparison.
Randy

[Richards]

Phil,
I'm sorry if my post was not clear (my white hair is a clear indication that I have a worn out brain). The comparison I refered to on the IH site points out the features of the IH/CNC mill and compares those features to features most likely found on other mills - without naming ANY other manufacturer. Aaron is not a mud-slinger, nor is anyone on the Tormach site. Both sites point out the features that each manufacturer thinks is most important to a shopper ready to make a decision to purchase a CNC mill. That's good for all of us who really want the facts before laying down our money.

Max711,
Thanks for the reference to misumiusa. I've bookmarked the site. At this point, I haven't contacted them for pricing information, but I'm assuming that the approximate $500 that you quoted is for the screw only, without machining, without bearings, without nut, without journals, etc. Is my assumption correct? (If not, the price would be a very pleasant surprise.)

To everyone who might who might think I'm distrustful of certifications relating to anything made in China. You're right, I absolutely would not accept any certificate of compliance for anything manufactured in China unless a trustworthy independant body that certified parts claiming to meet DIN and ISO standards was willing to certify that the part met the 'certified' standard. (Does anyone remember the Grade-8 bolt scandal that caused the crash of airplanes where counterfeit 'Grade-8' bolts from China were used instead of 'real' Grade-8 bolts?) I'm old enough to remember when the words Japanese and Junk could be used interchangably. Now, I just wish I could buy some of the excellent products produced by companies in Japan. They found their place in the world market and cleaned up their act. I'm sure that China will do the same - someday. How does this relate to the IH mill and the Tormach mill? Simply this: Aaron has specified modifications to the mills that he imports from China. Tomach (as far as I understand) has their mills built to their specifications. The ground ways on my IH mill are vastly superior to the ways on machines I've purchased from Harbor Freight - meaning that Aaron's specifications are being followed by the factory. If Tormach is getting the standards claimed (P4 ground ball screws), then their ball screws will be of excellent quality.

[MAX711]

Richards,

It's been a while since I bought mine so I went back to the site and priced up my Y axis ballscrew assembly. The screw and nut (cannot be bought seperatly because of preloading) is $433 which includes all end machining. The double angular contact bearing for the fixed end is $63 and the bearing for the support end is $20 So you get a complete ballscrew assembly for just over $500 and ships in 6 days from order. You can price and order all their parts directly online.

[MichaelHenry]

Tormach has their own independent QC person checking machines at the factory in China. They also publish the certification sheet specs that are supposed to be used to check each machine out.

My Tormach arrived today and I'll start tearing apart the crates tonight or tomorrow morning. Hopefully I'll be able to verify most or all of the certifications this weekend before disassembling the mill to move it to the basement.

Hopefully, no one is reading my replies with the idea that I'm anti-IH. It's just that I've checked out the Tormach a lot more than the IH mill and CNC kit. Apart from a general sense that the mill was well designed and made, my decision to buy the Tormach was largely based on a desire to obtain one major tool that would be plug and go. My other major machine tools are all used and involved one project or another to get running. One big benefit for me was the availability of the deluxe stand with flood coolant and chip shields that Tormach sells. I've no welding experience and really didn't want to get into fabricating a stand myself.

Mike

[philbur]

I checked my Tormach against the certificate (after using it for a while) and in all cases but one it was better than the minimum requirements. The one failure was the squareness of the Z-axis to the table in both the X and Y. It appeared that the head had moved during shipping from - China to USA - USA to Norway. Realignment of the Z-axis was easy. After some investigation the Y-axis miss-alignment turned out to be due to a slightly loose gib on the Z-axis, the head was leaning forward slightly. Now it’s all within spec.

Backlash on the X and Y-axis is less than 0.01mm and on the Z 0.02mm. Last night I did a quick test by milling a 25 mm round spigot on the end of a bar of 6061 aluminium. The diameter measured 24.98mm + or minus 0.01mm around the complete circumference. This was with a 0.5" end mill in a ER20 collet holder, with no checking of concentricity or actual cutter diameter calibration.

Pretty good for cheap and nasty, Chinese, "precision ground" ballscrews I would say.

Regards
Phil

Tormach has their own independent QC person checking machines at the factory in China. They also publish the certification sheet specs that are supposed to be used to check each machine out.

My Tormach arrived today and I'll start tearing apart the crates tonight or tomorrow morning. Hopefully I'll be able to verify most or all of the certifications this weekend before disassembling the mill to move it to the basement.

Hopefully, no one is reading my replies with the idea that I'm anti-IH. It's just that I've checked out the Tormach a lot more than the IH mill and CNC kit. Apart from a general sense that the mill was well designed and made, my decision to buy the Tormach was largely based on a desire to obtain one major tool that would be plug and go. My other major machine tools are all used and involved one project or another to get running. One big benefit for me was the availability of the deluxe stand with flood coolant and chip shields that Tormach sells. I've no welding experience and really didn't want to get into fabricating a stand myself.

Mike

[Richards]

It's great to know that P4 GROUND ball screws are used in the Tormach - and my profound appologies for doubting. It's also great to know that P4 GROUND ball screws, nuts, shaft machining and bearings can be purchased at an affordable price for any tool needing ball screws.

Sometimes, when I see a battle for tolerances going on, I just smile. Here in Utah, right now as the sun is just rising, the temperature in my shop is 38-degrees F. Yesterday afternoon at 3:00 p.m., after the Autumn sun had beat on my South facing metal door, the temperature in the shop was 97-degrees F. giving a 59-degree F. difference throughout the day. The formula that I use to calculate the expansion of steel due to temperature changes is 6.5 millionths of an inch expansion per degree F per inch of steel. Using that formula, I can expect 0.0000065 X 59 X 12 = 0.0046" error per foot of ball screw length. Sometimes the temperature difference is less. In the middle of the summer, the range is 80 to 110 degrees (there is a significant increase of temperature inside the shop compared to outside air temperature - often 15 to 20 degrees, sometimes more). Interestingly, the coldest part of the winter has less variation because I never let the shop temperature drop below freezing and only warm it to very moderate temperatures 55 or 60 degrees F., which gives a Winter time error about 1/2 that of Spring or Autumn.

All things considered, overspending or overspecifying to get the tightest possible tolerance and then disregarding the shop temperature doesn't make a lot of sense.

Just yesterday, I finally broke down and bought a 6" Mitutoyo digital caliper to go along with the various dial indicator calipers that I've used for years. That $106 tool will probably increase quality in my shop dollar-for-dollar more than any other tool or accessory or part - that and the knowledge that comes through lots of practice to know when exacting tolerance is necessary and when getting that last 0.0005" is just a waste of shop time. After all, regardless of the quality of the mill, the biggest factor affecting quality is the nut turning the handles or pushing the buttons .

[philbur]

Hi Richards,

Interestingly the rest of the machine and the part will expand by the same or a similar amount. What is really of interest is the rate of temperature change and the speed of reaction of each item in the system.

So as long as all parts of the machine are at the same temperature it would not matter what that temperature was. Although of course differing coefficients of thermal expansion between the part and the machine would place a part, but then you could allow for this in your part progam.

As rightly said by somebody previously in this thread, the key is "adequate for the purpose". However more than adequate is seldom, if ever, detrimental to the overall goal.

Regards
Phil

......
Sometimes, when I see a battle for tolerances going on, I just smile. Here in Utah, right now as the sun is just rising, the temperature in my shop is 38-degrees F. Yesterday afternoon at 3:00 p.m., after the Autumn sun had beat on my South facing metal door, the temperature in the shop was 97-degrees F. giving a 59-degree F. difference throughout the day. The formula that I use to calculate the expansion of steel due to temperature changes is 6.5 millionths of an inch expansion per degree F per inch of steel. Using that formula, I can expect 0.0000065 X 59 X 12 = 0.0046" error per foot of ball screw length.

[Runner4404spd]

just becuase the shop temperature can vary, 59 degrees, how much do you think friction will add to the heat and therefore change your measurements even more?

[Richards]

Phil and Runner,
You've both made valid points. Since the mill is steel and the parts that I cut are aluminum, there is a significant difference in expansion due to temperature. Heat generated by cutting and by the movement of the axes would have to play a part in that expansion. Fortunately, the parts that I cut have few areas that need to be held to sub 1/1000 tolerances. For those areas, I have turned Go/NoGo gauges in aluminum on my mini-lathe to be sure that the size of bearing holes and other critical holes are proper size. The Go/NoGo guage may not be the most scientific, but, to date, it has worked perfectly.

Although I, as a Chip Sweeper, would like to find a way to cut everything to exact size, I'm enough of a realist to know that some dimensions just don't matter very much and that the dimensions that do matter can usually be handled with a little creativity. This is not meant to reflect on the inherent accuracy of any mill, IH, Tormach, or any other make, it is just to point out that even though the mill may have been built to high standards, there may be other factors that could significantly reduce the quality of parts cut on that mill. The old saying, "A poor carpenter always blames his tools" might be modified to say, "A good carpenter knows the limitations of his tools and his environment, and knows how to work around those limitations."

[Tormach]

On the issue of ballscrews, just looking to ground versus rolled is really missing the point. As a side note, the screws in the Tormach PCNC 1100 are, in fact, ground. The real point for the specification of a ballscrew is precision. This is generally specified in a two part designation, a number and a letter. While there is actually quite a bit more to it, in brief:

grade 4 has an allowance of 0.0006" error per foot of length
grade 5 has an allowance of 0.0009" error per foot of length
grade 7 has an allowance of 0.0020" error per foot of length

A prefix of T or C indicates cumulative error is allowed. This means that a T7 can have 0.002" in a foot, 0.004" in two feet, 0.006" in three feet, et cetera

A prefix of P is a precision grade, where there are strict limitations on the accumulation of error over the length of the screw.

Milltronics and Haas use C5 grade screws. Tormach PCNC 1100 uses P4. You will have to get detailed specifications from your supplier, but in most cases retrofit kits use rolled screws which generally in a T10 to T7 class. Rockford screws state 0.0070" to 0.0030" per foot and cumulative, which makes them no better than T8 (ref http://www.rockfordballscrew.com/pdf...s-catalog.pdf).

For a more detailed understanding, look to published standards ANSI B5.48, DIN 69051 or JIS B1192. Remember, rolled or ground just tells you a process, it does not specify the actual precision or quality. The machines for rolling screws keep getting better, some can occasionally roll a T5 grade. In addition, lots of rolled screws have a finish cut on a grinder. I don't know if those would be called rolled or ground. For some photos of a Chinese ballscrew factory, check out the page at http://www.tormach.com/quality_overview.htm

Greg Jackson
Tormach

[MichaelHenry]

Greg,

Thanks for the info on ballscrews. For those that want to check out the Rockford site, note that there is a trailing ")" that must be deleted from the link to get to the PDF file.

Mike