[Gilmax]

He must of jumped the gun or something, because I don't think he honestly even believes what he just said. Certainly not nonsense at all and cutting envelope vs mass is a very commonly used comparison when shopping for machines.

[inov8r]

There are lots of folks: watchmakers, jewelers etc. that will appreciate higher precision and dont need a large machine such as the 770, let alone the 1100.

I believe watchmakers, jewelers, etc shop a different class of machine such as the Minitech or better.

[keen]

Hi Folks,
New here, just starting out on a journey of CNC machining to build cool toys for my other hobby: astrophotography.

For the past couple of months, I have been researching various mini mills that I intended to eventually convert to CNC. Eventually it led me to consider the Tormach family of CNC mills. Unfortunately owing to space considerations, I have to rule out the PCNC 1100 and the PCNC 700.

The newly announced PCNC 440 seems like just the right machine for my purposes except for one consideration. The rolled lead screws are of a lower grade and consequently less precise than the ground ones used in the PCNC 770 and the PCNC 1100 mills. Per conversation with Tormach representative, they are accurate to around 1.8 thousands over the X travel.

I called Tormach to enquire why this decision was made to use a lower grade component in the 440, the answer they gave was that this was a purely cost driven decision.

Speaking for myself only, I would be willing to pay a bit extra for ground ball screws. Buying a mill of this level is already quite expensive with all the tooling. I would ideally have liked to get the 770 but it is too big for my workshop.

The good news is that it appears that Tormach takes this sort of customer input seriously.

If there is anyone else who is on the fence regarding the 440 and cannot justify getting the 770 for space considerations, it may be a good idea to call Tormach with your input.

Best Regards,

I am glad you have brought this up. I mentioned this in the thread when the 440 was first announced, but the subject was soon left behind.

The screws in the 440 are not just rolled, but are also to a lower accuracy spec and I personally believe this was a bad decision just to save a few dollars. It affects the long term reputation of the machine. The 440 is not just smaller, but it is also to a lower accuracy spec.

Not only is it less accurate, but less accurate in a ballscrew also means faster wear. I know I am a fussy toolmaker and not a marketing man - but I feel strongly about this. I had a Syil Cx3 with rolled ballscrews, and it showed.

Please Tormach increase the price a hundred dollars or so , and stay with the more accurate ball screws as per your other machines.

Keen

[adamvs]

I dunno, I think this much ado( todo? ) about nothing. For about a year and a half my 1100 had hellacous backlash on the X axis .002, it took quite a while to figure out the cause ( it was the ballscrew worn from lack of lubrication - thank you previous owner ). Real world, tho, it made lots of good parts in that time, basically never made much difference. I say if you love the form factor, get one and hack it. Install P4s .. but give'em lots of oil .

[astromachinist]

I am glad you have brought this up. I mentioned this in the thread when the 440 was first announced, but the subject was soon left behind.

The screws in the 440 are not just rolled, but are also to a lower accuracy spec and I personally believe this was a bad decision just to save a few dollars. It affects the long term reputation of the machine. The 440 is not just smaller, but it is also to a lower accuracy spec.

Not only is it less accurate, but less accurate in a ballscrew also means faster wear. I know I am a fussy toolmaker and not a marketing man - but I feel strongly about this. I had a Syil Cx3 with rolled ballscrews, and it showed.

Please Tormach increase the price a hundred dollars or so , and stay with the more accurate ball screws as per your other machines.

Keen

Keen, thanks for your response.

Tormach already told me that the rolled ball screws they used was PURELY a cost decision. They also told me that the p4 grade ball screws have a measurable improved impact on final accuracy than c7, all other things being equal.

It would be great if people reading this thread were to drop a note on their website. I was told by the person I spoke to that they take this sort of feedback seriously.

[inov8r]

Dude! It is what it is. If you don't like it, modify it or buy something else!!!! We were all hoping it was going to be a more accurate machine but guess what, Its not!

[MichaelHenry]

It would be interesting for someone like John Saunders at NYCNC compare accuracy and quality of the same parts made on both the 1100 and 440 mills. He has both so could do it pretty easily.

[adamvs]

It would be interesting for someone like John Saunders at NYCNC compare accuracy and quality of the same parts made on both the 1100 and 440 mills. He has both so could do it pretty easily.

That would be an interesting comparison. If he still has original 1100, I'm almost betting on the 440. I know it's been gone over but here it is: https://tech.thk.com/en/products/pdf/en_a15_011.pdf

So C7s have to hold 50 uM per 300 mm.. that's 50 microns or 0.050mm per 300mm. .050/25.4= .00196 per 11.81".
Per inch average would be .00196 / 11.81 = .00016.

I could live with that.

[kstrauss]

As previously mentioned, "0.050mm per 300mm" does nothing to specify "???mm per 25.4mm". The error could be 0.05mm per 25mm and still meet the specification. In fact, the error could be +0.05mm per cm alternating with -0.05mm per cm and still be accurate to 0.05mm over 300mm!

[keen]

Another factor is a ground ball screw is ground after heat treatment and rolled is heat treated after rolling. (I am assuming this so please link in other information if I am wrong).

This would mean that for any given preload, the screw/ball/nut surfaces are likely to wear more rapidly on the more irregular surfaces of the rolled C7.

Funnily enough I was just this morning replacing worn balls on a machine.

Keen

[LeeWay]

I have replaced worn out balls a few times. That is not a chore I like very much. Don't drink too much coffee before you start that job.

[SCzEngrgGroup]

Seems to me people are making some mighty broad generalizations about rolled screws, and other things. I've used a lot of rolled screws, and quality varies greatly from one source to another. Most have been very good, and as smooth as the ground screws I've had. Specs are all over the map, and when you're talking Chinese manufacturers, ALL specs must be taken with a grain of salt. Most are very good, but every once in a while you get one that is a real turkey. But, most of the ones I've seen from China the last few years have been quite good.

And, just because a screw is spec'd at +/-0.002"/foot max lead error, doesn't mean that any particular example of that screw won't actually be MUCH better. In fact, I would pretty much be disappointed if I got a "limit sample". MOST should be much better than spec.

So, if you think rolled screws will ALWAYS be worse, they won't. If you think they will ALWAYS be less accurate, they wont. If you think they will ALWAYS be less smooth, they won't. I've seen rolled screws that were dead smooth and tight, and I've seen ground screws that were rough and sloppy.

Regards,
Ray L.

[keen]

Seems to me people are making some mighty broad generalizations about rolled screws, and other things. I've used a lot of rolled screws, and quality varies greatly from one source to another. Most have been very good, and as smooth as the ground screws I've had. Specs are all over the map, and when you're talking Chinese manufacturers, ALL specs must be taken with a grain of salt. Most are very good, but every once in a while you get one that is a real turkey. But, most of the ones I've seen from China the last few years have been quite good.

And, just because a screw is spec'd at +/-0.002"/foot max lead error, doesn't mean that any particular example of that screw won't actually be MUCH better. In fact, I would pretty much be disappointed if I got a "limit sample". MOST should be much better than spec.

So, if you think rolled screws will ALWAYS be worse, they won't. If you think they will ALWAYS be less accurate, they wont. If you think they will ALWAYS be less smooth, they won't. I've seen rolled screws that were dead smooth and tight, and I've seen ground screws that were rough and sloppy.

Regards,
Ray L.

Yes but Ray that logic has to be applied to the higher spec screws too - they can equally be much better than the finer tolerances they have. Higher spec does means less luck involved.

Keen

[adamvs]

I have replaced worn out balls a few times. That is not a chore I like very much. Don't drink too much coffee before you start that job.

But plenty of beer afterwards

[philbur]

You pays your money and makes your choice. If a product doesn't match your requirement then it's simple, look elsewhere and move on.

Phil

[Spinnetti]

You pays your money and makes your choice. If a product doesn't match your requirement then it's simple, look elsewhere and move on.

Phil

lol.. but how can you have endless pointless debates for us all to share our superior knowledge? That's what the internet is all about

[keen]

Ego is not the only reason people post... sharing and receiving information is a big benefit for many.

The zone has got me out of a hole many times - and I hope I have returned the favour to others.

keen

[Steve Seebold]

Hi Folks,
New here, just starting out on a journey of CNC machining to build cool toys for my other hobby: astrophotography.

For the past couple of months, I have been researching various mini mills that I intended to eventually convert to CNC. Eventually it led me to consider the Tormach family of CNC mills. Unfortunately owing to space considerations, I have to rule out the PCNC 1100 and the PCNC 700.

The newly announced PCNC 440 seems like just the right machine for my purposes except for one consideration. The rolled lead screws are of a lower grade and consequently less precise than the ground ones used in the PCNC 770 and the PCNC 1100 mills. Per conversation with Tormach representative, they are accurate to around 1.8 thousands over the X travel.

I called Tormach to enquire why this decision was made to use a lower grade component in the 440, the answer they gave was that this was a purely cost driven decision.

Speaking for myself only, I would be willing to pay a bit extra for ground ball screws. Buying a mill of this level is already quite expensive with all the tooling. I would ideally have liked to get the 770 but it is too big for my workshop.

The good news is that it appears that Tormach takes this sort of customer input seriously.

If there is anyone else who is on the fence regarding the 440 and cannot justify getting the 770 for space considerations, it may be a good idea to call Tormach with your input.

Best Regards,

I would say if you need a machine with better than .0018 accuracy over the X axis travel, perhaps you need to rearrange what's on your workshop ang buy the 770 or just move to a bigger workspace.

[ruawake]

Did anyone find out if the 440 is less accurate than the 770.
Thanks

[adamvs]

Did anyone find out if the 440 is less accurate than the 770.
Thanks

The only way to find out is to take the trouble to:
1) get two machines with in spec backlash.
2) get them in a room around 68F
3) make sure they are leveled.
4) make sure the mill table is trued.
5) probably some other things.

Kind of a tall order, I'd just contact Tormach and see what they guarantee on new machines and go with that.
Even with the old X ball screw ( that was pretty screwed - backlash at 0.002 ) it still was making good parts.