Project of the Month built by TonyM

Help Support Home Model Engine Machinist by donating using the link above or becoming a Supporting Member.
Home Model Engine Machinist > The Tools and Tips > Machine Modifications > Mini-Mill Spindle-Column Alignment

Reply
 
Thread Tools
Old 09-06-2009, 06:37 AM   #1
rudydubya
 
rudydubya's Avatar
 
Join Date: Nov 2008
Posts: 337
Liked 25 Times on 24 Posts

Default Mini-Mill Spindle-Column Alignment

After reading an earlier thread about off-center drilled holes HERE, I checked my Harbor Freight mini-mill and found that the spindle was not in alignment with the column, apparently not uncommon with the Sieg X2 machines. From what I've read, the only practical way to align the spindle and column is to shim the spindle housing where it mates with its carriage for Y-axis corrections, and to wiggle it about on its mounting screws for X-axis corrections. Either adjustment requires getting to the housing mounting screws, located behind the carriage and hidden by the column. You have to remove the head from the column to get free access to the screws (shown later below). It sounded like a challenge, but turned out to be relatively simple. Here's how I did it. But before I start, the photo below shows what I'll be calling the spindle housing and the carriage that make up the mill head. Your nomenclature may vary. Also, all my measurements are in inches, taken on import tools.

Click image for larger version

Name:	01-SpindleHousingandCarriage.jpg
Views:	90
Size:	88.7 KB
ID:	90037

Aligning the mini-mill spindle with the column basically just involves putting a test bar in the spindle and adjusting the spindle housing until the test bar is parallel to the column in both axes. I used E. T. Hackett's alignment procedure except for the choice of a test bar and the measurement method (see the files section of the Yahoo GrizHFMinimill group or at http://www.machinistblog.com/?p=991 for his writeup). Mr. Hackett used an aluminum precision shaft from McMaster-Carr and measured along the length of the shaft after it was turned to midpoint of indicated runout. I used a 7" long, .500 diameter steel shaft salvaged from an old inkjet printer instead, and used Rollie's Dad's Method to do the measurements and alignment (see the link in steamer's post HERE for more information on 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.

Safety Note: If you try this and you've never removed the column and head assembly from your mill before, be forewarned that it's heavy, and top heavy, and can hurt you if you're not careful or can't handle the weight. Also, the head counterbalance arm is spring-loaded, don't let it spring back and whack your knuckles or your favorite dial indicator when you let it loose.

First, I removed the mill column, laid it on a workbench, and removed the motor, the control box, and the electrical box so the head would be easier to slide off the column. I also removed the Z-axis stop and the bolt that connects the spring-loaded counterbalance arm to the carriage. I let the arm swing back and rest against the benchtop.

Next, I did some baseline measurements to see how much out of alignment the spindle was and where adjustments would be needed. The photos below show my test and adjustment setup. The test bar is in a 1/2" collet, but a drill chuck could just as well been used. For the Y-axis checks and adjustments, the DTI point was set on top of the test bar with just enough pressure to get about a .015 reading on the dial. 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 and rotated the spindle 360 degrees, and wrote down the minimum and maximum readings from the dial indicator, and then found the average of the two measurements (added the maximum and minimum reading together and divided the result by two). 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.) I repeated the procedure for the X-axis, with the indicator point at the side of the test bar, as shown in the second photo.

Click image for larger version

Name:	02-Y-AxisCheck.jpg
Views:	117
Size:	92.8 KB
ID:	90038

Click image for larger version

Name:	03-X-AxisCheck.jpg
Views:	99
Size:	80.2 KB
ID:	90039

My initial Y-axis measurements indicated about .0055 misalignment, the spindle axis being tilted downward slightly toward the column. For the X-axis, I couldn't get an exact set of readings because the DTI was hitting its stops as it got close to the bar end, but I estimated that the misalignment was at least .020, more or less, the spindle axis being skewed slightly to the right.

Now, knowing the nature of the adjustments required, I proceeded with the alignment. I did the Y-axis first. I removed the head from the column and loosened the four spindle-housing cap screws (shown in the photo below) so I could put a piece of shim stock between the spindle housing and the carriage. For my mill, the shim needed to be at the bottom of the spindle housing so as to raise the far end of the test bar just a little. I didn't know exactly how thick the shim should be, but since the Y-axis was only off by .0055, I tried a strip of .003 brass shim stock first, figuring that would be a good place to start. I slipped the shim in under the spindle housing where it joins the carriage, tightened the spindle-housing screws, put the head back on the column, and repeated the Y-axis measurements. As it turned out, the .003 shim was a good choice, reducing the Y-axis misalignment to less than .001 over the length of the test bar. The second photo below shows the shim location, just barely visible at the joint. Note that any Y-axis adjustments need to be made first, otherwise any X-axis adjustments that were made would be corrupted when the screws were loosened to insert the shim.

Click image for larger version

Name:	04-CarriageBackShowingSpindleBoxScr.jpg
Views:	94
Size:	93.5 KB
ID:	90040

Click image for larger version

Name:	05-Y-AxisShimLocation.jpg
Views:	88
Size:	88.3 KB
ID:	90041

For the X-axis adjustment, I removed the head again and loosened the screws so that the housing could be moved by hand slightly side to side (without significantly moving the shim), and put the head back on the column. I set up my DTI for X-axis measurements again and then moved the spindle housing side to side on its mounting screws to adjust the alignment while monitoring the readings on the DTI. When the alignment was right, I moved the head to the top of the column until I could get to the upper two housing screws from underneath and carefully tightened them. Then I removed the head completely, tightened the two lower screws, replaced the head, and re-checked the X-axis alignment. It took me a couple of tries before I got the bar alignment within .001 of the column axis, because the housing tried to shift a little when I tightened the upper screws. After I was satisfied with the alignment I re-checked both the Y-axis and X-axis alignment to make sure nothing had changed, replaced the motor and boxes, and put the column back on the mill. A final alignment check after the mill was back together indicated less than .001 error in either axis over about 5" of head travel.

Click image for larger version

Name:	00-CheckingSpindle-ColumnAlignment.jpg
Views:	64
Size:	94.8 KB
ID:	90042

I hope the above is of value to anyone considering adjusting their mini-mill. I did a search of the forum but didn't find anything about how to do such an alignment, but if it's there and I missed it, my apologies for the repetition. I'm still a novice on these little machines, and my methods may not be correct and are certainly not the only ways of doing these things. This is just the way I did it. I didn't go into detail on how I removed the column from the mill, the electrical boxes, the motor, etc. either, but if anyone has questions, I'll try to answer. Thanks for reading.

Regards,
Rudy



Last edited by rudydubya; 07-20-2017 at 09:44 PM. Reason: Replaced PB images
rudydubya is offline  
2
People Like This 
Reply With Quote
Old 09-06-2009, 01:28 PM   #2
zeeprogrammer
 
Join Date: Mar 2009
Location: West Chester, PA
Posts: 3,362
Liked 172 Times on 172 Posts

Default Re: Mini-Mill Spindle-Column Alignment

Thanks Rudy!
I have one of those machines and your post is very very helpful.
I know I'll be using this thread as a reference.

Thanks again for the well detailed process.


__________________
Carl (aka Zee. will sometimes respond to 'hey' but never 'hey you'.)

To work. To work.
zeeprogrammer is offline  
 
Reply With Quote
Old 09-06-2009, 02:53 PM   #3
tmuir
 
Join Date: Oct 2007
Posts: 888
Liked 32 Times on 32 Posts

Default Re: Mini-Mill Spindle-Column Alignment

Thanks a lot for that.
I read a bit about this on other peoples websites but none of them actually showed where the shims needed to go and I've been afraid to touch mine in case I make it worse.

I'll print this out tomorrow and when I go to fit my airspring I think that will be a good time to do this and I will even use a 1/2 inch SS rod I just got from a printer I pulled apart to.

Most helpful post I've seen on aligning the head of an X2.
Thanks
tmuir is offline  
 
Reply With Quote
Old 09-06-2009, 03:36 PM   #4
Diy89
 
Join Date: Sep 2009
Posts: 109
Liked 10 Times on 10 Posts

Default Re: Mini-Mill Spindle-Column Alignment

Great Job, Thanks for sharing. Now i have the incentive to work on the mill.
Great photos to.
Diy89 is offline  
 
Reply With Quote
Old 09-07-2009, 07:38 AM   #5
jmshep
 
Join Date: Aug 2008
Posts: 83
Liked 3 Times on 3 Posts

Default Re: Mini-Mill Spindle-Column Alignment

Thanks for that - I will now have another go at aligning my mill using some of your ideas.

How did you check that the column was aligned in both axis to the table when reassembled ?

Has anyone come up with a method of locating the spindle housing and carriage so that they stay in alignment rather than relying on just the four screws.
Similarly any good methods to add fine adjustment to the column to make tramming easier and locating it once set. (mine always moves as I tighten it).

Regards
John



jmshep is offline  
 
Reply With Quote
Old 09-07-2009, 10:28 PM   #6
rudydubya
 
rudydubya's Avatar
 
Join Date: Nov 2008
Posts: 337
Liked 25 Times on 24 Posts

Default Re: Mini-Mill Spindle-Column Alignment

Guys, thanks, I appreciate the feedback.

John, I just trammed it normally. No problems with the X-axis tram, but my column wasn't exactly perpendicular to the table in the Y-axis, something not so easy to correct. Others have loosened the three cap screws holding the pivot plate to the base shown below and shimmed underneath the plate, either at the front or back of the plate, to get the column straight, but I couldn't get the shims to work for me. I finally corrected the Y-axis tram when I was stiffening up the column to reduce flexing. I plan to post an explanation and some pictures on how I did all that in a day or two, but essentially I just put a little stress on the bottom of the column to force it into alignment. It didn't take much, the misalignment was only off about .004 before I fixed it.

Click image for larger version

Name:	ThreeCapScrews.jpg
Views:	48
Size:	83.9 KB
ID:	90046

And John, I haven't had a problem, at least that I'm aware of, with the spindle housing moving on the carriage. Have you seen movement with the screws tightened?

Rudy
rudydubya is offline  
 
Reply With Quote
Old 09-09-2009, 11:16 PM   #7
ksouers
 
Join Date: May 2008
Posts: 1,358
Liked 55 Times on 55 Posts

Default Re: Mini-Mill Spindle-Column Alignment

Rudy,
Very nice write-up on aligning the spindle. This seems to be a common problem with the X2 and I'm sure many owners will appreciate the effort you went through to document the process.


Kevin
__________________
Kevin

I make things.
ksouers is offline  
 
Reply With Quote
Old 10-04-2009, 09:22 AM   #8
4wheels
 
Join Date: Aug 2009
Posts: 80
Liked 4 Times on 4 Posts

Default Re: Mini-Mill Spindle-Column Alignment

Hi to all the other X2's,

I have been enjoying my X2 for a few years now only doing small minor jobs but very enjoyable never the less.

Then a few months ago I read a magazine article about the lack of rigidity in the X2 so the next use I finished facing a surface then with the mill still running I placed a finger on top of the spindle housing and without leaning on it I made a noticeable cut. I reckon I could operate the Z axis by mind control only!

The problem was deemed to be the rotating joint at the base of the main upright member and the offered solution was to add bracing from the four mounting points and the large bolt which the upright rotates on. They still allowed the ability to tilt the upright 45 either side. Once I get the upright upright the last thing I will want to do is rotate it. So my plan is to extend the bracing to some distance up the upright. Instead of fixed attachments at this high point I would use adjustable screws which will allow for fine tuning to the squareness of the upright.

Having just feeling good about that problem I had the same problem described on this thread i.e. started a hole with a centre drill then replaced it with a longer drill and then started the hole a mile away. I went through all the thoughts as described here and noticed that the paint at the joint between the spindle housing and the carriage housing was disturbed and was obvious that the spindle housing had rotated.

My thoughts were that to set the two units back to their start position was there would be no guarantee that they would stay there. They would be held by fiction alone resulting from the tension of the four securing bolts. I went along the lines a some sort of pining or keying but I worried about the testing for alignment procedure as I would hate to key it in the wrong place. The testing procedure was solved by the previous reply and thanks for that. The other great idea was the shim trick.

To hold the spindle housing after the alignment test I intend to securely bolt three bars to the carriage housing two top and bottom on one side a one in the middle of the other side these would overlap the spindle housing by 10mm or so with a bolt through each to contact the spindle housing to adjust and hold the alignment until the four holding bolts are tightened. They would also hold the housing from twisting when one is trying an over zealous cut.

Two problems two solutions. Your good, bad or indifferent comments most welcome.
__________________
Brian
* * * * "to grow old is compulsory - to grow up is voluntary!"
4wheels is offline  
 
Reply With Quote
Old 10-04-2009, 04:09 PM   #9
jmshep
 
Join Date: Aug 2008
Posts: 83
Liked 3 Times on 3 Posts

Default Re: Mini-Mill Spindle-Column Alignment

4 wheels
I have been thinking on similar lines to you re making sure the head stays in x axis alignment and also to improve the alignment process. Prompted by your post I had another look at my mill and came up with this idea :

Drill and tap a hole in each of the back corners of the motor mounting plate. With the four screws that hold the two sections together loosened slightly, screws in the new holes in contact with the carriage top surface will then be adjusted to "rock" the spindle housing into alignment. The screws can be then held in place with lock nuts and the four fastening screws tightened.
This method might not stop the spindle housing moving but it should help, provide a reference if it does and make the alignment procedure easier.

Before I start drilling can anyone see any flaws in the idea?

John S

jmshep is offline  
 
Reply With Quote
Old 10-05-2009, 05:42 PM   #10
jmshep
 
Join Date: Aug 2008
Posts: 83
Liked 3 Times on 3 Posts

Default Re: Mini-Mill Spindle-Column Alignment

Since my last post I have had a look at the underside of the motor mounting plate and its shape does not lend itself to being drilled as I had hoped.
Plan B is to mount a bar onto the end of the plate as an extension and do it that way.

John S


jmshep is offline  
 
Reply With Quote
Reply


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Reducing Mini-Mill Column Flex (and Column Y-Axis Alignment) rudydubya Machine Modifications 88 09-29-2015 10:11 AM
mini lathe spindle bearing lube John Rudd Machine Modifications 2 12-28-2011 07:39 PM
Help me buy a Mini Mill - Spindle Taper: MT #3 or R8? RMS General Engine Discussion 56 01-06-2011 08:17 PM
X2 mini-mill spindle thread Andrew_D General Engine Discussion 0 02-04-2010 03:38 PM
Mill Vice Alignment Brian Rupnow Machine Modifications 11 11-08-2009 03:16 AM



Newest Threads






- Top - Member List