PM25-MV saddle squareness

B

Bluebutton

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I have had a PM25-MV mill for 3 years now and Just last month I finally had time to really use it. The 3 year lapse was due to work and family issues. The issue I am having is, if I indicate a 2/4/6 block to be trammed in in the X axis within .0005" across the 6" side of the block I find when I check the other edge of the block (4" side) I get a 0.010" run-out in the Y axis. I have done this with a 1/2/3 block, angle plate and get the same results. Also repeated the previous tests with the appropriate gibs locked and no improvement. The photos show that the Y axis non tapered dovetail is parallel to the reference surface on the surface plate, but when checking the X axis the same way its out 0.006". I know this does not check squareness. I did check squareness on the CMM at my work and it showed 0.004" out of square over 6 inches.

I have searched the forums and found little info about the similar issues. I have been in contact with Precision Mathews and they are helping me with the issue. in the meantime im looking for all the info I can. So far the only options I'm finding are to replace the saddle and gibs, or scrape the dovetails. My question is has anyone experienced this issue and how did they correct it?
 

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You appear to be reading on the dovetails. I'd prefer to read on a piece of stock, known square on the working surface of the machine, the table. That's where the work will be....unless I'm missing something...
 
T Bredehoft said:
You appear to be reading on the dovetails. I'd prefer to read on a piece of stock, known square on the working surface of the machine, the table. That's where the work will be....unless I'm missing something...
Click to expand...
The photos are for reference. I did use a 2/4/6 block clamped to the table. I first found the issue when trying to make a 3"x 3" x 0.50" thick block. I was machined 2 sides parallel but when squaring up the other surface it as 0.010" out. I checked the side with a granite square on a surface plate and machinist squares as a secondary check. No matter what I do I cannot get a square part between the x and y axes.
 
Strange...Write PM about it, they may have an Idea or two. They are easy to work with.
 
Reading this it sounds like you were off .010” on a part that was only .500” thick. Then off .010” on a 4” side of your block. That seems odd. If you were off .010” in ½” would expect more like .080” in 4”. I know you said you locked the gibs but are they fully adjusted and tight? If your X axis gib is not adjusted it would be easy to get the table to rock .010”? I am sure I am missing something here, just trying to help.
 
BladesIIB said:
Reading this it sounds like you were off .010” on a part that was only .500” thick. Then off .010” on a 4” side of your block. That seems odd. If you were off .010” in ½” would expect more like .080” in 4”. I know you said you locked the gibs but are they fully adjusted and tight? If your X axis gib is not adjusted it would be easy to get the table to rock .010”? I am sure I am missing something here, just trying to help.
Click to expand...
Sorry for the confusion. The part was out 0.010" between 2 sides of a 3 inch block. The 0.50" thickness was just the stock i was using.
 
Just watched your video. When you have your dial on the Y Axis see if you can grab the table and move it by hand. Grab each end by the hand wheels and try to turn it like a steering wheel laying flat. If you are getting movement there then you need to tighten the gib to get all the play out. That seems like a lot of out of square to have ever passed any level of quality control.
 
Also, maybe captain obvious here but tightening the gib is not tightening the lock screws on the side until it is snug. Tightening the gib is adjusting it from the end and wedging it against the dovetail. You mention the tapered dovetail earlier so sounds like you have it. But also mention you have not run it in 3 years so just figured it was worth a mention.
 
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