The steel gauge Scheppach supply is hopeless - chuck it in the sundry ironmongery box.
What worked for me:
- find some time when you are not rushed
- sit on a stool next to the planer, cup of tea nearby
- take out the old blades, clean the wedges and slots and replace the new/sharpened blades; just gently tighten the bolts evenly, but don't torque them
- lay a flat piece of bar on the outfeed table, projecting over the planer blade and hold the bar in place with a small magnet at the far end (I use a spare planer blade that happens to be magnetised - make sure it is flat as some of my blades were a bit bowed
- set up a dial indicator on the outfeed table with the point adjusted to the top of the steel bar above the centre of the cutter block
- as you rotate the block, you can see the amount of vertical deflection on the dial indicator - you are really aiming for something pretty small - 0.05mm is 5 marks on my dial indicators and that is about 2 thou (of an inch)
- it takes some getting used to the very fine adjustment of the allen bolts that seat the planer knives - the knives wont tend to drop down when you want to lower them, so you need to press them down with a bit of wood (if the wedge bolts are too loose, you won't be able to position the knife properly. A bit like a hand plane, I find it works best when advancing the blade to the desired position.
- you need to do this process with the dial indicator set up on either end of the knife as one adjustment will affect the other end - the best thing is to bite the bullet and buy two dial indicators so that you can see where you are on both sides at the same time.
- you will find that when you get to finally torque up the wedge bolts, this will probably bring the knives out further, so you go back and redo, allowing next time for this
- usually takes a few goes, but once you get the hang of it and apply some patience, it works well.
I have now got the luxury of Centrofix knives on my big Ixes planer, so knife changing is a doddle (although more expensive!). I have used the same technique for levelling the tables/cutter block, hopefully a one-off. Here are a couple of photos of the setup.
Hope that is of use
Cheers