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2nd generation saw cuts

rtaylor

PRO Member
I just finished up a vase with a 2nd generation feature ring. I had real difficulty making those centerline cuts. I found that the laser method is really not accurate enough unless the laser set up is plumb with the saw top. If it is not perpendicular to the saw table, but at a slight angle, then the position you set for the blade at the saw top is off by the time you line up 3/4 inch higher. I found that the laser dot is fuzzy and easy to get off by 1/32 to 1/16. The relative method was better but still off somewhat. All of this tends to get cumulative which can make things go south in a hurry. Has any one just tried to set the fence and rip center line to centerline? This was a great source of frustration and the results were less than perfect.:(

Thanks
rtaylor
 
The relative positioning system is not cumulative but setting a fence is. If you set a fence and you're off by 1/32nd, your next cut will be of 1/16th and so on.

Here's some tips that may make things easier. The laser is simply to get you close. After marking the point where the cut is to be made, use a laser or simply eyeball the cut. Start the cut but stop just short of the target. At that point, you should be able to see if the center of your saw kerf is going to pass through the center of the dot. If it isn't, you should be able to see how much it is off. Move the board that much and make the cut again, stopping even closer to the dot. It should be centered now and if it is, set the relative stop and both this cut and the following cuts should be right on the money.

It just takes a little practice. I can consistently make second generation boards with perfect joints using this method. However, if your first generation board isn't glued and clamped correctly, all bets are off. Before cutting strips for the second generation, you should be able to stand the board up on both edges on the table of your table saw and the tip of every 'ear' should touch the table. If this is not the case, you will not have success regardless of how you cut the strips.

Lloyd
 
"Before cutting strips for the second generation, you should be able to stand the board up on both edges on the table of your table saw and the tip of every 'ear' should touch the table. If this is not the case, you will not have success regardless of how you cut the strips."

Well, that explains in a nutshell my difficulties. Not only do they normally rise up in the middle, the lamination tends to bow front to back. I have tried different gluing techniques, but haven't hit on one that works for me yet. I imagine I am using too much clamping pressure causing the bowing effect. I tried cutting the ears off to make the board straight, but that must be too late. It all boils down to accuracy I guess.
 
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Jeff,
Yes, too much clamping pressure can cause bowing and the glue is so strong that it will permanently make a bow part of the new board. You probably saw the PowerPoint presentation I posted called 'Tips and Tricks' in the Multi-Generation Laminations tutorial at this link:
http://woodturnerpro.com/software-t...o-tutorials-multi-generation-laminations.html

Art Bodwell made an upgrade to this Clamping Channel which has some significant improvements. Since the channel is clamped to a base, you can use hold-down devices in the channel to clamp along the board to keep elements flat and that has always been my biggest challenge. Here is a link to his tutorial:
http://woodturnerpro.com/blogs/art-bodwell/5-gluing-jig.html

I have found the key to always clamp the laminated board and all generations in a parallel channel that will force alignment to be correct. Once you have a first generation board that was clamped and glued in this manner, making a second generation board from it is no more difficult than making the first generation board. In theory, this process should be able to be repeated with the same accuracy, but since the sky is not pink in my world, that is not always the case.

Lloyd
 
Jeff,

In addition to the blog post Lloyd mentioned above, here are pictures of the clamping channel in actual use. Since I started using this, I have not had a problem keeping the glue up flat and square in both planes. It is worth the small investment if you are going to be doing a lot of multi-generation work.DSCN1537.jpgDSCN1538.jpgSince the picture was taken, I've added two more of the Rockler clamps for a total of four. In the blog pictures, notice the two thin strips of wood. This elevates the work enough to let glue drip out. In a recent improvement, I've added clear packing tape to the plywood base between the clampinig channels, this greatly facilitates glue clean up after removing the work piece.
 
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Thanks Art and Lloyd, I think I need to do some shopping. This looks like an excellent idea and should solve many issues I am having.
 
I have made a gluing clamp using the Rockler parts. I recently purchased a Festool table (I think that is what Lloyd uses.) I had some trouble trying to find a good way to clamp it to the table. I see in Lloyd's pictures that you use the stops but don't seem to clamp the fixture to the table. It looks like you use the movable part of the clamp to clamp the stock to the fixture by pushing it against the stops. This looks like it might work better than what I did by clamping the fixture to the table and then using other clamps to hold the stock. Also, I made my fixture by cutting the 3rd rail in half so my fixture is 36 x 18. Do you have pictures showing how you clamp the fixture if I am not correctly understanding how you do this. If not totally clamped, I had trouble keeping the fixture square.Wayne
 
The relative positioning system is not cumulative but setting a fence is. If you set a fence and you're off by 1/32nd, your next cut will be of 1/16th and so on.

Here's some tips that may make things easier. The laser is simply to get you close. After marking the point where the cut is to be made, use a laser or simply eyeball the cut. Start the cut but stop just short of the target. At that point, you should be able to see if the center of your saw kerf is going to pass through the center of the dot. If it isn't, you should be able to see how much it is off. Move the board that much and make the cut again, stopping even closer to the dot. It should be centered now and if it is, set the relative stop and both this cut and the following cuts should be right on the money.

It just takes a little practice. I can consistently make second generation boards with perfect joints using this method. However, if your first generation board isn't glued and clamped correctly, all bets are off. Before cutting strips for the second generation, you should be able to stand the board up on both edges on the table of your table saw and the tip of every 'ear' should touch the table. If this is not the case, you will not have success regardless of how you cut the strips.

Lloyd
Thanks for the advice Lloyd. I have no problems getting flat and straight glue ups its only on those 2nd generation cuts. I will keep at it using relative methods.
 
I have made a gluing clamp using the Rockler parts. I recently purchased a Festool table (I think that is what Lloyd uses.) I had some trouble trying to find a good way to clamp it to the table. I see in Lloyd's pictures that you use the stops but don't seem to clamp the fixture to the table. It looks like you use the movable part of the clamp to clamp the stock to the fixture by pushing it against the stops. This looks like it might work better than what I did by clamping the fixture to the table and then using other clamps to hold the stock. Also, I made my fixture by cutting the 3rd rail in half so my fixture is 36 x 18. Do you have pictures showing how you clamp the fixture if I am not correctly understanding how you do this. If not totally clamped, I had trouble keeping the fixture square.Wayne

My clamping channel has been based on having a rigid right angle and then making parallel clamps to the two edges making up the right angle. So my clamping channel is not necessarily clamped to my Festool table, although it could be. Instead, I just make sure my strips are simultaneously clamped to the right angle elements. Where this approach has limitations is that since the channel is not clamped to the table, it cannot be used to put downward pressure on individual strips. This limitation will be corrected when I switch to Art's approach of having the elements attached to a platform.

I haven't taken the time to do this yet because I don't have a big problem in gluing the next generation board and keeping the strips flat. As long as I don't over-clamp, it's easy to put downward pressure where needed.

Lloyd
 
Thanks Lloyd, I could not open Art's pictures yesterday before I wrote. Now I have opened them and see what he did. I had thought of that as well but I had the table and didn't want to take the time to build something. Wayne
 
Wayne,
As you see in the pictures, one end is a wood block that is screwed to the plywood base. While both channels can move in the tee channels, I have secured the lower one at right angles to the wood block, and only the top one is movable. This way when I place the glue up, moving the one channel tight makes everything perfectly square. I use this for the first lamination glue up and anything else I glue that wants to be square. I can add clamps perpendicular to the glue up for added pressure it necessary Art
 
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