The biscuit joiner was invented around 1955 in Europe with the intention it would help cabinet makers using particleboard, MDF, and plywoods in making stronger and more accurate joints using these materials. It was soon discovered that a biscuit joiner could also be used in natural woods too.

Watch it on Youtube: https://youtu.be/yEsCVi4Rsn4

One of the main purposes of a biscuit joiner for anyone using natural woods was to use it for making connections for aligning narrow boards together to make a wider board. Using biscuits to help keep natural boards aligned for glue-ups became something of a standard but not everyone experienced success with this practice, including me. If you are getting good results, congrats, many people are not and this article is to help assist those who are having problems with getting good results. 

I had so many problems with my biscuit joiner that after fighting with it for a few years I gave up using it, and sold it, along with a box of #20 biscuits, and never regretted my action.
More recently, a few others who have been having issues had contacted me to ask me why their biscuit joiners are not working properly ... and since I didn't even have one anymore AND the questions intrigued me, I wanted to see if now ... I could go back and see if I could solve the problems that many encounters with biscuit joiners. 

Porter Cable Biscuit Joiner

I went out and purchased a used Porter-Cable Biscuit Joiner that has been reputed to be "a very good tool". The one I bought came in a nice plastic box and, like many biscuit joiners, didn't look like it had seen much use, so I purchased it.

I also purchased some brand new #20 biscuits, the best I could find which happened to be Lamello (the European manufacturer and inventor of the tool). 

When I got to the shop the first thing I did was to measure the thickness of the cutter blade, then test the machine by making a couple of cuts, the machine was already set on #20 biscuit size so I made a couple of cuts. I found that the standard thickness for every biscuit joiner blade is 5/32" or 4mm

Porter-Cable Biscuit Joiner

The very first thing I noticed was that the biscuit I inserted was high centering, which means the slots I cut were not deep enough. I re-adjusted the stop, tried it again and it worked ... well ... kind of. 

Over the next several hours I tested, checked, and re-checked every aspect of the biscuit joiner and found a number of areas where things can go wrong such as tear-out from the blade were quite common.

Biscuit Joiner Tear Out

I also noticed inconsistencies in biscuits, many were loose-fitting.

Biscuit Joiner loose

I also discovered that the biscuit joiner itself was easily moved during the cut, and since the blade cuts on both the way into the slot, then also on the way out if it is left spinning, the resulting slots are often slightly wider making sloppy fittings.

Biscuit Jointer

Other Biscuit Connections
There are a number of "mechanical" connections that can be used in place of the wooden biscuits. These are often some form of metal or plastic-type substance and may or may not be suitable for use with natural wood. 

Here are links to some of these connections

This Lamello Connector available from Amazon

Lee Valley.com ( USA, Canadian and International site, see website) -  Metal Connectors 

Lamello.com have a variety of fasteners, check under Join Wood

There are many others as well if interested please Google your choices.

Finding Solutions That Work
Since I was not happy with the inconsistencies in biscuit thickness, I decided to make my own "tabs" from someone in wide material, quarter-sawn for strength, or any hardwood where you can see the grain running from end to end will work fine. I used my table saw with a circular saw blade installed to give a nice fine cut and made my first cut at what appeared to be something more than 5/32". When I tested this wood, I found that it was too thin, so re-adjusted the fence on the table saw and made a second cut. As would be expected the second was almost too thick, but with a little bit of hand sanding, I managed to get it down to a thickness that worked perfectly. Do not sand too much if you do this, it is easy to take off too much wood.

I cut my tabs at 3/4" and they fit perfectly, and when I slide the 2 sides of the wood together, it was a perfect fit. Finally, a biscuit joint that works for natural wood. 

Biscuit Joiner Tabs

The following checklist consists of every problem contingency that can occur when using a Biscuit Joiner to connect NATURAL WOODS -only- when using or attempting to use wooden or similar biscuits or to make your own connection tabs.
Note: for use with particleboard, MDF, Plywood, or other manmade materials other processes will be required, not covered here.

View and Download PDF Checklist by clicking the linkBiscuit Joint Check List

Colin Knecht's - WOODWORKWEB Check List for Biscuit Joiners Being Used with Natural Woods

1 - Set the machine for the type of biscuit you are using,  #20, #10, or #0

2 - Check how well biscuits seat by drawing a line through a seated biscuit then flip it upside-down to see if the line sinks below the baseline of the cut

3 - Double check the height of the carriage so the biscuits will go into the wood where you want them, usually near the middle

4 - Make clearly visible, straight alignment marks on BOTH pieces of wood that are going join

5 - When you make the cut, MAKE SURE the biscuit joiner is not jostled up or down during the cut, if it does you cannot get a nice clean cut. Do not rush your cuts

6 - Examine EVERY cut you make in every board and if needed cutaway with a sharp utility knife or chisel, EVERY piece of tear-out that the joiner blade makes

8 - If biscuits are sloppy in the cut, DO NOT USE THEM. There is no value in using biscuits that are not at least "snug" in the biscuit cut slot

9 - If needed make your own connection tabs. They will need to be slightly larger than 5/32" or 4mm. These can be cut on a planed or cut on the table saw then lightly sanded to the correct thickness. If using the #20 biscuit setting, the tabs should be 21/128" or 4.23mm the stock should be 1" or 26mm wide then cut tabs that are 3/4" or 19mm long.  Test to ensure snug to the tight fit. If not, re-do them

8 - Now you can apply glue to the surfaces only, of the boards you are want to glue-up. There is NO NEED to glue the biscuits, if you use them or the tabs into place, in fact, you are better NOT gluing them. Biscuits that are glued only make more mess with much more glue squeeze out from them and needlessly adding to the squeeze of glue from the mating wood surfaces.

And Finally
I know many of you will be wondering and asking, now that I have a biscuit joiner that is giving good results, will I start using it in production now?  .. NO.
Many years ago when I gave up my old biscuit joiner and started using my dowelmax jig, I was so happy with the joints and the strength of the dowels for joining wood, I will not be reverting back but I will hang on to my new biscuit joiner for now, who knows what will happen in the future ...
Dowelmax Joint

Copyright Colin Knecht
woodworkweb 

    

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