- Joined
- Dec 29, 2012
- Messages
- 394
I thought I had posted this a year ago but I cannot find it anywhere on the site!
So I re-post it for anyone interested in a shim-free method to tram solid column mini mill.
After some months from the initial tramming of my mini mill (see it here: http://www.hobby-machinist.com/showthread.php/10788-Tramming-my-Sieg-SX2P-mini-mill-(identical-to-LMS-3960)?p=89448#post89448) I discovered that the drill chuck I was using initially, has an unacceptable play, driving the whole procedure on the wrong side.
When I used collets and rechecked verticality of the column I noticed that it was far from vertical.
So same procedure followed again, and again, and again, to manage some 0.10 mm @ X and 0.08 mm @ Y direction. Far from happy!
Last Christmas having some free time, I searched thoroughly the Internet and plan a more systematic approach on the matter.
My approach started from testing that:
a) the head of the mill stands parallel to the column and
b) the column stands vertical to the table.
Part A. Head to column tests.
The drawing below shows my test setup.
I have mounted in a collet a steel shaft 20 mm thick (salvaged from an old shock absorber), and used Rollie's Dad's Method (explanation follows) to do the measurements. For the X-axis checks, the DTI point was set on the side of the shaft. Then, two sets of measurements were taken, one set at the collet end of the bar, and the other set at the far end of the bar. I started my measurements at the collet end. I locked the carriage there, rotated the spindle 360 degrees, wrote down the minimum and maximum readings from the dial indicator, and then found the average of the two measurements [(max + min)/2]. Then, without changing anything about the indicator, I unlocked the carriage and wheeled the head back up the column, so that the indicator was at the other end of the bar. I locked the carriage, got the maximum and minimum readings there, and averaged those two measurements. Then I compared the averages. The difference between one end's average and the other end's average was the total misalignment for the distance along the bar. (That's Rollie's Dad's method.) The beauty of Rollie's Dad's method is that the test bar doesn't have to be perfectly straight, and runout of the chuck or collet won't affect the results either. I repeated the procedure for the Y-axis, with the indicator point behind the test bar, as shown in the right side of the drawing. Results were X = 0,05 mm misalignment and Y = 0,01 mm over a distance of 200 mm. That means if I drill a 20 cm deep hole, moving the head down from top to bottom end, the holes will be out of alignment by 0,05 mm. I can live happily with it!
Part B. Adjusting the column verticality (tramming)
I don’t know about you, but I am the kind of guy who feels very frustrated if, lets say, after a dozen of trials fails to achieve the results he aimed for. That was exactly the case when I tried to tram my mill. As I was putting a shim on one corner I had to put another one at another corner otherwise the readings were far from correct. With the new shim I had to calculate again and put a new one and so on. I have repeated this procedure a dozen times and I decided that there is something wrong with the method as there are 4 corners and in order to achieve ultimate results you have to put different thickness shims in at least 3 of them.
Scratching my head for days I could not find a better method. Internet had nothing to suggest either. Suddenly last night I found the solution. I will use long bolts screwed to the base and I will support column with nuts below & above each corner.
So sleeves up and off we go. I prepared 4 long bolts with their nuts and washers (see next photo the short black bolt is the original).
I removed all shims and cleaned thoroughly base and column. I put the bolts, nuts and washers to column (see next photos).
Then, leaving nuts loose, secured bolts firmly to base (That’s why I did not trim the heads of the bolts initially).
Next step was to screw lower nuts fully down and to secure column by screwing the top nuts tight.
I was ready then to mount my DTI, a piece of glass from an old scanner (measured to be flat) and start tramming.
The procedure was easy. If you wish to lift a particular corner(s) unscrew the lower nut (after making provision that the top had been loosen as well so the column could change inclination).
To make corrections and fine-tune any corner follow next photo!
Then using a scanner glass (as the flattest thing in possesion) I tested and fine-tuned X and Y axes.
Piece of cake! In 5 minutes job finished.
Results: X= 0.00 Y= 0.00
PERFECT!!
That is X+ and X- readings
And thats Y+ and Y-
Finally, holding the magnetic base I rotated the spindle 90 degrees (in case there is a misalignment in the spindle) and tested again. Results same as before.
That’s how the base looks now. I never choped the bolts to achieve a more professional look (as I should have done).
Thank you for reading
Petros
So I re-post it for anyone interested in a shim-free method to tram solid column mini mill.
After some months from the initial tramming of my mini mill (see it here: http://www.hobby-machinist.com/showthread.php/10788-Tramming-my-Sieg-SX2P-mini-mill-(identical-to-LMS-3960)?p=89448#post89448) I discovered that the drill chuck I was using initially, has an unacceptable play, driving the whole procedure on the wrong side.
When I used collets and rechecked verticality of the column I noticed that it was far from vertical.
So same procedure followed again, and again, and again, to manage some 0.10 mm @ X and 0.08 mm @ Y direction. Far from happy!
Last Christmas having some free time, I searched thoroughly the Internet and plan a more systematic approach on the matter.
My approach started from testing that:
a) the head of the mill stands parallel to the column and
b) the column stands vertical to the table.
Part A. Head to column tests.
The drawing below shows my test setup.
I have mounted in a collet a steel shaft 20 mm thick (salvaged from an old shock absorber), and used Rollie's Dad's Method (explanation follows) to do the measurements. For the X-axis checks, the DTI point was set on the side of the shaft. Then, two sets of measurements were taken, one set at the collet end of the bar, and the other set at the far end of the bar. I started my measurements at the collet end. I locked the carriage there, rotated the spindle 360 degrees, wrote down the minimum and maximum readings from the dial indicator, and then found the average of the two measurements [(max + min)/2]. Then, without changing anything about the indicator, I unlocked the carriage and wheeled the head back up the column, so that the indicator was at the other end of the bar. I locked the carriage, got the maximum and minimum readings there, and averaged those two measurements. Then I compared the averages. The difference between one end's average and the other end's average was the total misalignment for the distance along the bar. (That's Rollie's Dad's method.) The beauty of Rollie's Dad's method is that the test bar doesn't have to be perfectly straight, and runout of the chuck or collet won't affect the results either. I repeated the procedure for the Y-axis, with the indicator point behind the test bar, as shown in the right side of the drawing. Results were X = 0,05 mm misalignment and Y = 0,01 mm over a distance of 200 mm. That means if I drill a 20 cm deep hole, moving the head down from top to bottom end, the holes will be out of alignment by 0,05 mm. I can live happily with it!
Part B. Adjusting the column verticality (tramming)
I don’t know about you, but I am the kind of guy who feels very frustrated if, lets say, after a dozen of trials fails to achieve the results he aimed for. That was exactly the case when I tried to tram my mill. As I was putting a shim on one corner I had to put another one at another corner otherwise the readings were far from correct. With the new shim I had to calculate again and put a new one and so on. I have repeated this procedure a dozen times and I decided that there is something wrong with the method as there are 4 corners and in order to achieve ultimate results you have to put different thickness shims in at least 3 of them.
Scratching my head for days I could not find a better method. Internet had nothing to suggest either. Suddenly last night I found the solution. I will use long bolts screwed to the base and I will support column with nuts below & above each corner.
So sleeves up and off we go. I prepared 4 long bolts with their nuts and washers (see next photo the short black bolt is the original).
I removed all shims and cleaned thoroughly base and column. I put the bolts, nuts and washers to column (see next photos).
Then, leaving nuts loose, secured bolts firmly to base (That’s why I did not trim the heads of the bolts initially).
Next step was to screw lower nuts fully down and to secure column by screwing the top nuts tight.
I was ready then to mount my DTI, a piece of glass from an old scanner (measured to be flat) and start tramming.
The procedure was easy. If you wish to lift a particular corner(s) unscrew the lower nut (after making provision that the top had been loosen as well so the column could change inclination).
To make corrections and fine-tune any corner follow next photo!
Then using a scanner glass (as the flattest thing in possesion) I tested and fine-tuned X and Y axes.
Piece of cake! In 5 minutes job finished.
Results: X= 0.00 Y= 0.00
PERFECT!!
That is X+ and X- readings
And thats Y+ and Y-
Finally, holding the magnetic base I rotated the spindle 90 degrees (in case there is a misalignment in the spindle) and tested again. Results same as before.
That’s how the base looks now. I never choped the bolts to achieve a more professional look (as I should have done).
Thank you for reading
Petros