Tramming PM 833tv

RJSakowski said:
Considering your experience level and that you have a brand new machine, if I were you, I wouldn't be thinking about shimming the column at this point. I definitely wouldn't think about using epoxy as Sefan Gotteswinter did as there is no going back if it isn't done correctly. Get to know the machine first. When you have correctly identified a problem, then you can think about the best solution.

There are a lot of interactions that can affect the tram of a machine. A properly set up mill/drill has a flat table, an x axis travel that is parallel to the table surface, a y axis travel that is parallel to the table surface, a column travel that is perpendicular to the table surface in both x and y directions, and a quill travel that is parallel to the column travel. In addition, all gibs should be properly adjusted. This is of particular importance for the column gib as a loose gib there can cause the the head to sag. Loose x and y gibs can cause table lift as when the table is moved to extreme positions.

A simple tramming procedure can be done to correct an out of tram condition. Adjust tram in the x direction by rotating the head. Adjust in the y direction by shimming between the head and the mount to the column. Be sure to lock the head prior to tramming to prevent any sag caused by a loose column gib.

A non-perpendicular column to table will have the effect of moving your reference datum in the x and/or y direction as the head is raised or lowered. If the head position is not changed, you will not notice any effect. For that reason, I would not rush to correct any issues.
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Y and X are not flat and I don't see PM doing anything to fix this as it all needs to be replaced and you just get a newer version of the same thing..
 
Tammy63 said:
Ok so over 6in I can be out .0015 the head down spindle upbut when I move the X 6in out I have up to .006 out and if I go 6in past center I got. 004 out. If I do the Same thing but move y to the next rib I'm .002 out and .004 out if I go to the last rib.

Now if I bring the head up and the spindle down my numbers are all off but not the option so I can't find a happy middle.

But hey I can shim my work and still get what I need done it just takes 5x longer to setup and a lot of math. So why am I so upset with this mill. If I plunge a hole using a new mill that can cut you just looking at it the head moves around as much as. 010 out same as it does when I bore a hole out with the boring head.
I can still get what I need to do but the setup time and how slow it takes to remove. 020 off the OD of a motorcycle hub makes me cry..

The spindle runout on this mill is only .0003 and it looks and feels rock solid until you put it to use..
The sad part is I was just going to get the PM940V but I believed that the VT was made better as PM listed it as.
I have a PM1030 lathe and I get way better accuracy from that and that came with a. 003 of runout from the 3 chuck..

If I had to do it all over again I would have looked around for a used lathe and mill
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Are you locking the head before making these measurements or cuts?
 
dabear3428 said:
Are you locking the head before making these measurements or cuts?
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Yes and no. Locking the head will move the spindle or mill bit out .001 but you can't lock it if you bore with the feed. If I lock the spindle it can more as much as .003. With this mill you never know how back you cuts will be because their is too much wrong with it...

And yes and have adjusted all the gibs to get the best accuracy out of it. I guess I got a Monday/Friday mill
That this point it's just a toy I play with in the winter or when I need to make or fix something on one of my bikes.
 
Tammy63 said:
Y and X are not flat and I don't see PM doing anything to fix this as it all needs to be replaced and you just get a newer version of the same thing..
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How are you determining the table flatness?

Years ago, I swept my Tormach 770 with a digital dial indicator mounted in the spindle and the table looking as if it wasn't flat. It turned out to be due to the table tilting on the ways as the center of gravity shifting to an unsupported region. I had adjusted the gibs following Tormach's recommended procedure which was based on increased drag which then resulted in an increase in backlash. A CNC mill by its nature can't lock the axes as it must be able to move in all three directions in a pseudo random fashion. The problem with the Tormach is IMO caused by two factors. The stepper drive for the x axis is located outboard of the table on the left side which causes a cantilevered effect when the table is moved to the left and the ways are poorly designed and don't provide sufficient support for the table. The separation between the two y axis ways could have been significantly larger and the separation between the two x axis ways could have been larger and their length could have been increased. BY comparison, the Tormach ways are separated by 7" and are 9" long for the y axis and the separation for the x is only about 5" and the length is 11-1/2", My RF30 clone has a separation of 8" and a length of 10" in the y ways and a separation of 8" and a length of 15 inches in the x ways. This design change on the Tormach would have increased cost minimally and only improved performance.

Here is a before and after graph of my table surface, as measured with a spindle mounted indicator. The dashed lines are the before and the solid lines are the after. The zero reference is with the table to the far right and out. Note that with the table at the far in and right and for about 6" of travel the elevation is flat and at its lowest. As the table is moved out, the elevation increases and the flat range decreases. Before adjusting the gibs, my overall variation was around 3.5 thousandths. After gib adjustment, it drops to about half at the extremes and in the regions wher I work most often, it is within a thousandth.
1713272811273.png
 
Tammy63 said:
Yes and no. Locking the head will move the spindle or mill bit out .001 but you can't lock it if you bore with the feed. If I lock the spindle it can more as much as .003. With this mill you never know how back you cuts will be because their is too much wrong with it...

And yes and have adjusted all the gibs to get the best accuracy out of it. I guess I got a Monday/Friday mill
That this point it's just a toy I play with in the winter or when I need to make or fix something on one of my bikes.
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Tammy63 said:
Yes and no. Locking the head will move the spindle or mill bit out .001 but you can't lock it if you bore with the feed. If I lock the spindle it can more as much as .003. With this mill you never know how back you cuts will be because their is too much wrong with it...

And yes and have adjusted all the gibs to get the best accuracy out of it. I guess I got a Monday/Friday mill
That this point it's just a toy I play with in the winter or when I need to make or fix something on one of my bikes.
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you can lock the head and still use the quil
 
Every machine tool is a compromise. Of course if it doesn’t meet the advertised specs you have a problem, but if you can make the parts needed then it’s doing the job for you.

If not then either rectify the problem, hopefully with the help of the manufacturer, or replace it with one that meets your requirements.

I learned a lot about this by trying to build my own CNC mill/drill. Since then I’ve replaced it with a couple of better machines. And, I have the Gorton at work if I really need something more stout.

John
 
7milesup said:
As a point of reference, I owned an 833T for a few years. I, too, was not utterly impressed with it. I should point out that the gib on my Z-axis was atrocious. PM claims that these "fit" each machine, and when I inquired about getting a new gib, I was told it would take weeks to get one. Mine was not of the correct size (too thin) and thus could not be adequately snugged unless I used a shim behind it. As I said, I was not impressed. I had planned on making a new gib myself but ended up selling the 833 to an unsuspecting dude who oozed machismo. Perfect.
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ok so note to self, never buy a used mill from Wisconsin, jk
 
On more than one occasion, I have seen comments in mill descriptions of 'almost the accuracy of a jig boring machine'. This on mills costing $30k plus. No way a sub-$10k bench mill is going to compete. But that doesn't excuse poor quality like in @7milesups case (or anyone else's).

When I was looking at upgrading my milling capability, I seriously looked at used 2-3 ton bed mills. Problem is finding one that isn't worn out, and paying to have that sucker put in my garage. :oops:
 
matthewsx said:
Every machine tool is a compromise. Of course if it doesn’t meet the advertised specs you have a problem, but if you can make the parts needed then it’s doing the job for you.

If not then either rectify the problem, hopefully with the help of the manufacturer, or replace it with one that meets your requirements.

I learned a lot about this by trying to build my own CNC mill/drill. Since then I’ve replaced it with a couple of better machines. And, I have the Gorton at work if I really need something more stout.

John
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I'm living with mine just not happy with it and I know it's not going to get better then what it is now..
Just like my 1st Hubby I knew what jobs I could get him to do and what job/things I was on my own with..
 
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