The way you are setting your blade depth is wrong. You aren't setting it deep enough!! As I said, you need to have the blade go about 1/3rd the way into the slip sheet, not just scratching the surface of it. Do that first before trying to solve anything else.
When I talked about having the cutting head in the same place every time, I didn't mean on the rail. I meant in relation to you.
You can start the cut anywhere on the rail you want, but you should try to "address" the cutter head the same way each time. The angle I talk about is between you and the head. Consistency in HOW you do it is important in getting consistently good cuts. (Zen and The Art of Mat Cutting) It is important that you become one with your machine, little grasshopper.
I've never used a Logan cutter. I consider them to be at the bottom of the mat cutters out there. My opinion is they are for occasional work and not meant for full time framing businesses. I have used a C&H cutter and now have a Fletcher cutter and when I draw the guide lines, I use the hold down bar which is set to the size I want. Then when I cut a mat, theoretically, the blade SHOULD cut right on the line.... but it doesn't actually do that. Thus my asking you about where the blade goes into the mat in relation to the line. Once you know how the machine works you can make the tiny adjustments in how you work which will allow you to get the good cuts you want. Single edge blades versus double edge ones and which way you put the single edge blade into the holder will also make a slight bit of difference in where the blade enters the mat in relation to the line. Even something like how you hold the pencil when you draw the line (or how thick you make the line) will affect the relationship between the line and the blade.
That's why practicing on scraps over and over and over is so important to becoming consistent in how you do it.
This is SOOO much easier to show in person!! I'm used to just doing it and am now having to put into words that you will understand something i don't even think about anymore. That, plus I have a computerized mat cutter now and rarely ever use the table cutter.
Thoroughly diffused and clear as mud!!
Thanks again for the reply. I agree with you on the blade depth, I will take a closer look at that. When you say a 1/3 deep into the slip sheet, there are two ways to look at that. Are you referring to along the 45 degree angle of the cut? or perpendicular to the mat?
A mat that's 0.053 thick, will be 0.075 thick at 45 degrees. How do you judge your blade depth?
I think my mat cutter, which is 40" long, may be cutting deeper in the middle, so blade depth would be a issue.
The fact that the Logan 650 uses a partial board base, flatness of that base could be a problem. I keep mine on flat solid table, but there's slight warp in one corner.
In regards to the lines, I think what you are referring to is called parallax error. In my day job I'm a machinist, and I match lines with lines all the time, so that's not a problem.
If you take a look at the manual, the number one cause of problems is setting the blade to deep.
I thought I was buying a quality mat cutter, but I'm beginning to regret my choice, it just isn't consistent cut to cut, but it still could be operator error, I hope so anyway.
I don't use a wood pencil, I use 0.5mm 5H mechanical pencil which draws a very fine line, the 5H lead doesn't smear. I hold it at a slight angle when drawing lines.
I practiced cutting mats and mats and mats until the cows came home, just when I thought I had it right, something would change.
When looking at the drop, the distance (gap) from the drawn line to the cut is smaller in the long direction than in the short, in fact the gap in the short direction is twice as wide as it is the long way, shouldn't they be the same? This gap is equal on both sides, just twice as large on the short ends. I hope I didn't confuse anyone here with that last comment.