[Vicanic]

How would I go about determining if the column were damaged from over tightening or if there were an issue with the workmanship of a Taig Mill?

[Jeff-Birt]

Are you having problems with the mill? If so what problems?

[Vicanic]

Well, if you want the short version, I am nearly 100% certain that the mill cannot hold a tram.

Only continue if you would like the long version.

I received this mill semi-used from a friend of mine. He purchased it from VCS Hobbies in NY because he was interested in doing some projects with it, only to find out after getting it he did not have the time to mess around with it. Machining is a subject I am very interested in, so I offered to 'borrow' it and get it up and running on the agreement that I would do the projects he wanted with it. So, he set it up in his home, but never did anything with it. Never even hooked it up to the computer.

After I got it, I built a table and enclosure for it and began setting it up, but I had no idea what I was doing. I slowly figured it out though, and now after 11 months of practice tramming I feel confident that I have got this process down to a T, and that I am using the right equipment. I have been able to consistently tram it to within a half thou the last 3 times in a row. The problem is whenever I then mount my 'sacraficial' chunk of 6061 aluminum, and make incredibly light cuts, i then measure the tram and it is way off. The farthest so far was 9 thou. The cut is described as follows.

I am using the Taig Vise that came with the mill. In it I mount a 2x2x3 chunk of 6061 aluminum. I am running a HSS 1/2 center cutting endmill with a 3/8 shank at 4300 rpms, taking .002 off the top in a zigzag pattern at 10 ipm, with a 1/4 in stepover. I am using WD-40 as a lubricant. It is just a very simple cut.

I then take the vise off and put my 123 block back on to measure, and the z column has shifted. The last couple of times I did this I suspected I might not have tightened the column enough, so I tightened it a little more, but after 3 times I feel uncomfortable making that nut any tighter. I don't have a good feel to estimate a torque value, but it is beyond the suggestion I got from the nick carter site to choke up on the wrench, that is for sure.

What I suspect is that at some point in time, whether it was at VCS Hobbies, at my buddies house when he set it up, or during the time in which I did not have a solid grasp on what I was doing, that nut may have been tightened too much. I do think I have narrowed it down to that nut due to the fact that the Z-Column is the portion that has shifted every time. Whatever the problem is, I have currently broken the machine down and I intend to inspect the parts individually once I know what it is that I am looking for, or what it is supposed to be.

Any help that anyone can offer would be greatly appreciated.

Thank you,

Thaylen Langsmith

[awerby]

with a light cut like you're describing. I'd check for dirt, oil, rust or damage on the mating surfaces of your column and base. It sounds like you're not getting good friction between those two machined surfaces. A little bur or a tiny chip of metal can cause that. Rust takes up twice as much space as metallic iron, so any patches of it will interfere with a flat-to-flat fit. If there are any scratches on those surfaces, inspect them with magnification to make sure there's nothing protruding above the surface, and stone it down if there is. Clean them with brake-cleaner or some other de-greaser before reassembly. Check the alignment of the machined surfaces and the screw to make sure everything is going together flat and square.

If after all that, the mill still won't hold itself square under normal use, then get in touch with the Taig factory: www.taigtools.com. They're proud of the tools they make, and build them to last. They guarantee their parts and workmanship for two years, and even after that time is up they'll usually repair their equipment for a very reasonable price.

Andrew Werby
www.computersculpture.com

[Vicanic]

Upon careful inspection of the mating surfaces I found no evidence of rust, grit, or dirt. Nor did I find any physical defects that protruded from the surfaces. I did however find a gouge on the mating surface of the column. It is pretty big, but right on the edge. I don't know if it would effect the ability of the machine to stay rigid. Attached is a link to a picture of the said gouge. I most definitely never did anything to this machine to cause something like this.

DSCF0354 | Flickr - Photo Sharing!

[cameraguy]

I can't imagine that is going to affect anything. It doesn't affect the flatness of the mating surface nor reduce by more than a trival amount the surface area of the bearing surface.

If the mating surfaces are fine then I would look to the stud itself. If it has been dramatically overtightened in the past (as you suggested may have happened), it is likely just stretching now, just like with any over-torqued stud. Likely does not have near enough elasticity left to deliver proper clamping force. Best to just replace it.

[awerby]

Sometimes a gouge like that can have a raised edge, which would cause the mating surfaces not to mate. Check it carefully to make sure that's not the case. But yes, if the stud's deformed, that could also prevent the whole assembly from tightening up.

Andrew Werby
www.computersculpture.com

[Vicanic]

Just from touch alone it does not feel like it has any ridge or edge protruding. Is there some other way I could test this? On the subject of an over torqued stud, is there any way I could test if this is the case? Also, I took off the endcap nut that sits on the opposite end of the mating surface and found that the stud seems to be threaded into the metal body. How would I remove this stud?

[cameraguy]

I took off the endcap nut that sits on the opposite end of the mating surface and found that the stud seems to be threaded into the metal body. How would I remove this stud?

If its threaded into the body, back it out the way you back out any stud; double nut it and put a big wrench to it.
This is why you replace studs after each use on things like cylinder heads and other critical mating components; once they have been torqued down past a certain point they can't be reused. A Taig should not ever need to be torqued down tight enough to have stretched the stud, but if your friend went all Tool Time on it and did indeed stretch it, replacement is the only option. Luckily, they are cheap and locally available.

[Vicanic]

I do own a torque wrench. Does anyone have a particular value to put it down to? I read on Nick Carter's website that 40 ft lbs is way too much, but that still doesn't give me an actual number.

[Taflin]

The front of the mill can start bending in if you over tighten the stud. I added a large heavy duty washer to distribute the load closer to the box section.

[desktoplathes]

...I have been able to consistently tram it to within a half thou the last 3 times in a row...

...I then take the vise off and put my 123 block back on to measure, and the z column has shifted...

Thaylen - A couple questions and comments... When you say you have consistently trammed to within a half thou, what measurement are you referring to exactly? One major misunderstanding I've noticed with customers is that they assume tramming starts with adjusting the Z column such that the table sweeps from one side to the other with minimal indicator travel. This only ensures that the spindle (and not the Z column) is perpendicular to the X axis. The only measurement that should be considered when adjusting the Z column is taken by fixing a test indicator to the traveling spindle assembly (I use the T slots on the spindle housing) and running it up and down the a long face of a bolted down 1-2-3 block (or similar squared reference). Is this the measurement you are referring to above?

Another question.. when you say you put your 1-2-3 block back on.. do you ensure it is completely clean where mating to the table? Do you bolt it down or just set it there? Is it in the same orientation as before and with the same mounting surface? And when you say it has "shifted" by how much has it shifted? If it's gone from a half thou to a thou, you're looking at thermal differences causing such changes. One other thing... when you get it down to the last half thou... do you happen to give it one last tighten before moving on to cutting? I ask because tightening the nut typically moves the column enough to create a couple thou difference in 3" of travel. I always have to plan for this and adjust it out before final tightening, and then remeasure to see if it wound up right.

Something else to check for is the dovetail plate mounted to the Z carriage. It is mounted with 4 to 6 cap screws that can be loosened and the plate rotated slightly to adjust the spindle alignment (only after ensuring the Z column is perpendicular). I wrote up a procedure for the process I use for tramming here. I doubt that you've got an overtightened column. It seems to me that over tightening would result in an obvious warped frame rather than a slipping Z column. But then I've never seen one over tightened before - only warnings to not do so. Keep at it - you will figure it out eventually! -Keith

[Vicanic]

---what measurement are you referring to exactly?

Yes, I am talking about mounting the indicator to the headstock and running the tip up and down the long face of the 1-2-3 block. I do clean the mating surfaces, and I bolt it down to the table. I am measuring the same face.

---And when you say it has "shifted" by how much has it shifted?

The largest amount it has shifted so far has been 9 thou, and that was this most recent time, but the first time I checked this it had moved 3 thou. I do give it one last tighten, but I adjust for it and on top of that after I give it that tighten I double check it.

[bwprice100]

Hi

Not familiar with your machine but would it be possible to put a BRI on the column to see if it is moving?

Sent from my X10i using Tapatalk 2

[bwprice100]

Hi

Not familiar with your machine but would it be possible to put a DTI on the column to see if it is moving?

Brian

Sent from my X10i using Tapatalk 2

[B-RAD]

You could pin it like I did in a thread near this one.

[desktoplathes]

Interesting... I know you said you think you've overtightened it but I'm still wondering if it's not tight enough. Can you use your torque wrench to measure how tight you've got it now? Torque it as you normally do and then use the torque wrench to remove the nut and measure when it breaks free. I will try and measure the torque on my mill and see what I've got with my normal method of tightening it down. -Keith

---what measurement are you referring to exactly?

Yes, I am talking about mounting the indicator to the headstock and running the tip up and down the long face of the 1-2-3 block. I do clean the mating surfaces, and I bolt it down to the table. I am measuring the same face.

---And when you say it has "shifted" by how much has it shifted?

The largest amount it has shifted so far has been 9 thou, and that was this most recent time, but the first time I checked this it had moved 3 thou. I do give it one last tighten, but I adjust for it and on top of that after I give it that tighten I double check it.

[B-RAD]

You can't measure torque by breaking the nut free, it takes more torque to take off a bolt than to install it. This is why they make breaker bars and impact guns....

[Vicanic]

What I could do is tighten it down to right around the area I did last time, then loosen it a bit, and try and find right about where it is with the torque wrench via trial and error.

What I am doing right now is stripping it down and cleaning everything again. This is the third time I have done this, but I never cleaned the mating surfaces with brake cleaner before, so maybe it will help.

[Taflin]

Add a large heavy duty washer to where the stud comes through the front of the box.