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Cross Cuts Differ From Rip Cuts...

This is a discussion on Cross Cuts Differ From Rip Cuts... within the Tools and Woodworking forums, part of the General Woodworking category; Several days ago I had very carfully re-calibrated the scale on my Incra LS TS ...


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Old 07-13-2013, 12:30 PM   #1 (permalink)
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Several days ago I had very carfully re-calibrated the scale on my Incra LS TS but had not used the saw since then. The calibration was done making cross cuts. This morning I wanted to see if my set up was still dead on but instead of making cross cuts I ripped a piece of wood and when I measured it with the dial calipers the board was 1/32" longer than the three inch setting on the scale. I made a second cut and got the same results. This just didn't seem to be right so I made two cross cuts with the fence locked down and clamped just like it had been when making the rip cuts. Those two cross curs were dead on. So I re-calibrated for the rip cuts and decided that I would, for the most part do all of my critical cross cuts on the Express sled as I should have been doing anyway.

Then I set up the sled and picked out two pieces of wood, walnut by the way, that had been ripped to be two inches wide and were about half an inch thick. I set the stops on the fence to about five inches and made five cuts, two were from one of the pieces and three from the other piece all five with the stops set in the same position. The three cut from the same piece of wood were within a couple of thousands but while the other two were also just as close in their variation in length, they were about .015" longer than the others. So I checked everything for slop and found none move the stop just a little closer to the blade and re-cut the five pieces and once again, got the same results, the pieces from the one piece os wood were consistant in their length as were the ones from the other piece of wood but again their lengths were off by about .015". I re-cut these five pieces of wood several times and got the same results with each set of cuts.

Fortunately this variation is a no-issue in the real world, but it does tend to suggest that all wood is not the same, we already knew that, but these slight differences do make a differences in how the blade cuts them. These are, to me, just interesting facts but as it has pointed out to me so often by the more experienced members of the is forum, "So What".

Jerry

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Old 07-13-2013, 08:32 PM   #2 (permalink)
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I think a lot of that has to do with the blade and whether it it is designed for going with the grain or cross grain. When you go to buy blades you'll notice lots of options like hook angle, type of grind, and of course number of teeth. All designed for an optimum cut in certain circumstances. Then there is the issue of free play in the arbor bearings of the saw. You can't set them with no free play. All of the bearings I've ever set had to have .002 to .006 thousandths of an inch of free play. Too tight and they would burn out prematurely. Different cutting operations could affect that free play differently. Too many difficult or impossible to control variables. That's why most of us don't worry about it. It's like trying to catch the wind and paint it green or fart upwind into a hurricane.
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Old 07-14-2013, 12:31 AM   #3 (permalink)
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Jerry-

Please paint me a picture. I'm trying to figure out what you are doing.

You have a left-tilt Craftsman (upper grade) TS with an Incra system on it right?

When you doing your crosscuts and rip cuts... you are going against the rip fence or using your Incra miter for crosscuts and your Incra fence for rips?

Or are you saying that with a somewhat square piece of wood, you can put it against the rip fence, go with the grain to make a rip cut, turn 90 degrees and crosscut against the grain, you get 2 different measurements? Wouldn't happen to be a thin kerf finish blade would it? Sometimes those, when used for ripping, will have a tendency to follow the grain...

Another thing to try is to take a piece of scrap about 12" long... put it against the rip fence & cut a thin piece off. Turn the piece clockwise 180 degrees so the fresh cut is against the fence.Adjust the fence in 1/8 in. Run it through again. (Those cuts will now be parallel.) Adjust the fence in 1/2". Turn the piece over (top to bottom, left to right). Run it through again. Take the off-cut and measure the width at each end. Tell us what it measures out as...***

Edit-- notes ***: Mark the first cut as "A". Mark a wavy line along the edge that is towards the front of the saw. So on the second and third cut, the wavy line should be the same orientation, if rear on second, still rear on third. What the off-cut should show you, if it is different measurements, that divided by 2 shows how far out your rip fence is from being parallel to your blade. If it's out. first check your blade to the left miter. I set the blade to the left miter and the fence to the left miter (with the back kicked out 0.001" to 0.002"). For setting fences to the left miter slot, I have a 36" long 3/4" square machined bar that I lay in the miter slot... I then move the rip fence to it. I put a 0.002" feeler gauge at the rear of the fence and adjust it. If the fence has a little flew to it (which yours should not, so ignore the next) then I set it dead on.
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Old 07-14-2013, 03:35 AM   #4 (permalink)
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Then I set up the sled
Clue no 1?
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Old 07-14-2013, 06:37 AM   #5 (permalink)
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Originally Posted by MAFoElffen View Post
Jerry-

Please paint me a picture. I'm trying to figure out what you are doing.

You have a left-tilt Craftsman (upper grade) TS with an Incra system on it right?

When you doing your crosscuts and rip cuts... you are going against the rip fence or using your Incra miter for crosscuts and your Incra fence for rips?

Or are you saying that with a somewhat square piece of wood, you can put it against the rip fence, go with the grain to make a rip cut, turn 90 degrees and crosscut against the grain, you get 2 different measurements? Wouldn't happen to be a thin kerf finish blade would it? Sometimes those, when used for ripping, will have a tendency to follow the grain...

Another thing to try is to take a piece of scrap about 12" long... put it against the rip fence & cut a thin piece off. Turn the piece 180 degrees so the fresh cut is against the fence. Adjust the fence in 1/8 in. Run it through again. Adjust the fence in 1/2". Turn the piece over (top to bottom). Run it through again with the same side counter clockwise 180 degrees. Take the off-cut and measure the width at each end. Tell us what it measures out as...
O.K. Mike, I'll do it and back to you on the results. By the way, right now I am running a full Kerf Forrester blade that is primarily a cross cut blade, I do have a Freud thin kerf fusion blade and should use it for ripping. There is lot for me to learn about blades obviously.

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Old 07-14-2013, 08:03 AM   #6 (permalink)
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Jerry working with wood is fun but there are times when it is annoying and not total fun, do this, rip into a piece of wood a small way and then pull it out of the saw, then do the same with a cross cut and then measure the saw cut and see if one is wider than the other or both the same, this will show if the saw blade is ripping and cross cutting a bit different or not. NGM
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Old 07-14-2013, 09:02 AM   #7 (permalink)
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Jerry working with wood is fun but there are times when it is annoying and not total fun, do this, rip into a piece of wood a small way and then pull it out of the saw, then do the same with a cross cut and then measure the saw cut and see if one is wider than the other or both the same, this will show if the saw blade is ripping and cross cutting a bit different or not. NGM
Neville,

I will do what you say and also what Mike is asking for me to do the next time I'm in the shop.

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Old 07-14-2013, 12:02 PM   #8 (permalink)
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I added notes to my last post to clarify...
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Old 07-15-2013, 05:07 AM   #9 (permalink)
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I added notes to my last post to clarify...
Mike I always wanted say how funny I think your "don"t worry cartoon" line is, very funny, NGM
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Old 07-15-2013, 11:27 AM   #10 (permalink)
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Mike I always wanted say how funny I think your "don"t worry cartoon" line is, very funny, NGM
Thanks. "I" think it's one of those ironically funny but true things. A two edged sword- Sometimes people blurting out a suggestion that is not physically possible in the real world... But on the other side of that, mostly a suggestion that is new and possible but people not understanding it because their experience or understanding is narrow and they can't see the all the other possibilities...

I saw that on a BBS years ago and it stuck in my head. I'm generally patience with people and have a twisted sense of humor. It has gotten me by.
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Last edited by MAFoElffen; 07-15-2013 at 11:36 AM.
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