Adjusting the Depth:
First, slightly loosen the adjustable handle. Then, adjust each depth adjusting screw in turn to move the blade to the desired position. These adjustments are done while holding the plane upside down and sighting down the sole from the front of the plane. It is important to have your eye in a direct line from the bottom of the plane. Then, relock the adjustable handle.
Springs above the frog keep constant tension on the adjustment threads, so depth adjustments can be done either way and then the handle locked. So, no worry of any backlash!
Adjusting the Mouth Opening:
I will start by saying that I never adjust the mouth opening. Therefore, the frog is always seated back against the wood bed. This is my recommendation for users also. The main reason for moving the mouth opening is to help fight tearout. This, however, is only minimally effective. Adjusting the chipbreak distance is much more effective, and doing this on a ‘Blum’ plane is very easy and quick.
However, adjusting the mouth opening is easy. Just loosen the adjustable handle, and insert a small shim behind the frog, from the bottom of the plane. This can be as simple as a matchbook cover or similar. Snug up the adjustable handle and then adjust the depth screws. Then tighten the adjustable handle.
On a traditional double iron, the chipbreaker is the piece that sits on top of the iron. On a Blum plane, the chipbreaker also sits on top of the iron and is secured at the bottom of the frog. This assembly comes off easily and is easily adjusted. It doesn’t require any of the fiddling and precise fitting of a traditional chipbreaker. On a ‘regular’ double iron, the iron must first be ground perfectly square. If not, the chipbreaker can not be set really close ( where it is most effective ), because it won’t match up with the iron. The second issue is that the back of the blade must be flat and the chipbreaker must fit against the back perfectly. This is especially critical when setting the chipbreaker very close to the edge ( small chipbreak distance ).
Otherwise, chips will jam underneaath the chipbreaker and all planing comes to an immediate halt. The third issue is that the chipbreaker must be ‘sprung’ just right to give the proper pressure at the leading edge so no chip can ever get underneath it. The screw holding the chipbreaker to the iron might be 2-3″ from the front of the iron. The fourth issue is that the leading edge of the chipbreaker must be ground at the proper angle to be the most effective at holding the chip down to be sheared by the iron. On some planes, this is not ground right, so the chipbreaker is much less effective than it could be. This is probably because some makers still believe the chipbreaker is only there to just stiffen the iron!
On a Blum plane, none of those issues come into play. The blade is easily lined up with the chipbreak edge. The bottom of the frog is ground so the blade contacts it evenly. The back-up iron gives direct pressure so no chips can get underneath, and the leading edge is ground at the proper angle to give maximum effectiveness. Also, the depth doesn’t need changed to reset the chipbreak distance.
Adjusting the Chipbreak Distance:
You can leave the depth right where you were cutting, or, to make it easier to see and maneuver, you can lower the frog below the sole about 1/8″. Re-lock the adjustable handle.
Using a Torx driver, loosen the 3 screws on the bottom of the frog slightly, and using the tip of the driver, lever up the back up iron and remove. Then, use the driver in the mouth to push out the chipbreaker/blade assembly into your hand. The blade and chipbreaker are held together by rare-earth magnets so the chip break distance is set by just sliding the two and setting the distance with your fingers.
What is the ‘Right’ Distance?
The best answer I can give is that experience will give you your answer. Most old texts said to move it ‘as close as possible’ for fine cuts in difficult woods, and move it ‘farther back’ for heavier cuts. One old book said to move it to 1/100 th of an inch for swirled grain. That’s .010 ( ten thousands of an inch ). I move it closer than that for difficult cuts. The problem is that measurement of the chipbreak gap is difficult at best. You can use a feeler gauge or calipers. Since this is done ‘by eye’, the best thing to do is look at the distance and compare it ‘by eye’ to a standard such as a feeler gauge or caliper gap. You won’t have to know any measurements to set it, but it does help when learning to have something to go by and compare to.
The closer the chipbreaker is set, the harder the plane will be to push, so its use needs to be somewhat discretionary. If you are jack planing with a heavy cut, and there will be more cleanup with a smooth or fore plane, you don’t want the chipbreaker set so close as to make it more difficult to push. Experimentation is the key. Happily, your ‘Blum’ plane has the easiest to set, most reliable chipbreaker on the market, so moving it should become part of your planing regimen. It will greatly expand your planing abilities.