#12
  
Using the Porter Cable biscuit joiner.  Not my favorite tool, but has its uses.  

In the process of gluing together some boards, planning to make a flat surface.  They are about 28 inches long and 3/4' thick.  Have run all of the individual boards through a conventional joiner and confirmed that the surface is in fact completely flat.  And yes, I cut the biscuit slots without touching the depth of cut setting any.

Question:  When glued together, how come the boards do not line  up exactly?  For some parts of the glued assembly, at least a part of one of the boards is slightly proud.

I know I can sand it down, but I feel like I should not have to...
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#13
  Dumb biscuit joiner question Steve Soldo Using the Porter Cab...
Tool has to sit perfectly flat on the board as you cut the slot.  Sawdust from a neighboring slot sitting on the face would be enough to mess up the next cut.
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#14
  Dumb biscuit joiner question Steve Soldo Using the Porter Cab...
You also must put the fence on the good face side, just in case there is a slight variation in thickness.
We do segmented turning, not because it is easy, but because it is hard.
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#15
  Dumb biscuit joiner question Steve Soldo Using the Porter Cab...
There can also be a slight variation in the thickness of each biscuit or the amount of glue on each side of the biscuit in the slots. Does not take much difference to make a noticeable misalignment like you are experiencing.

One way to prevent that problem is to use cauls or similar means of aligning the surfaces of all the pieces.




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#16
  Dumb biscuit joiner question Steve Soldo Using the Porter Cab...
There should be enough play in the biscuit slots to line up the boards. Cauls are a good idea to keep the boards flat.
Don
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#17
  Dumb biscuit joiner question Steve Soldo Using the Porter Cab...
I think there is also a subtle timing aspect to getting biscuits to best align boards. Biscuits are compressed so they will easily fit into the slots, swelling on moistening with glue. If you initially put clamps on just tight enough to hold everything in place, then wait just a bit for swelling before tightening down the clamps, tapping into place any out of alignment, this should better align the boards.
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#18
  Dumb biscuit joiner question Steve Soldo Using the Porter Cab...
For pieces only 28" long I wouldn't bother with biscuits.  I tighten the clamps just enough to snug the boards together and then coax them into alignment with a rubber mallet, using my fingers to feel if the joints are flush, then tighten the clamps and check again to make sure they are still aligned.  Yeah, cauls sometimes, but for me are usually more bother than benefit. 


John
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#19
  RE: Dumb biscuit joiner question jteneyck For pieces only 28" ...
(07-02-2019, 01:10 PM)jteneyck Wrote: For pieces only 28" long I wouldn't bother with biscuits.  I tighten the clamps just enough to snug the boards together and then coax them into alignment with a rubber mallet, using my fingers to feel if the joints are flush, then tighten the clamps and check again to make sure they are still aligned.  Yeah, cauls sometimes, but for me are usually more bother than benefit. 


John

^^^^^^^^^ Agree wholeheartedly! As others have mentioned, you almost always get better results with a biscuit joiner (I have the PC 557) when you register both the base of the joiner and the material on the same flat surface. Using the fence as registration can cause misalignment (DAMHIKT!).

Doug
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#20
  Dumb biscuit joiner question Steve Soldo Using the Porter Cab...
(07-02-2019, 01:52 AM)Steve Soldo Wrote: Using the Porter Cable biscuit joiner.  Not my favorite tool, but has its uses.  

In the process of gluing together some boards, planning to make a flat surface.  They are about 28 inches long and 3/4' thick.  Have run all of the individual boards through a conventional joiner and confirmed that the surface is in fact completely flat.  And yes, I cut the biscuit slots without touching the depth of cut setting any.

Question:  When glued together, how come the boards do not line  up exactly?  For some parts of the glued assembly, at least a part of one of the boards is slightly proud.

I know I can sand it down, but I feel like I should not have to...

If the machine held parallel to the flat side of the stock the slot can be slightly angled. An angled slot will cause alignment problems. This is in part why some people don't use the fence but instead rest both the base of the biscuit joiner and workpiece on a flat bench. I learned about this when cutting biscuit slots in the face of a piece of plywood. Resting the fence on the edge of a 3/4" piece of ply it's real easy to have the machine not exactly perpendicular in this case when plunging. The result is an angled slot. I started clamping a jointed square piece of 3" X 3" stock exactly even with the edge of the ply giving the fence more to rest on. It worked much better.
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#21
  Dumb biscuit joiner question Steve Soldo Using the Porter Cab...
(07-02-2019, 01:52 AM)Steve Soldo Wrote: ...Question:  When glued together, how come the boards do not line  up exactly? ...

You still need to use cauls or clamps to perfect the fit. And you will still need to surface the assembly.
Wood is good. 
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