I have dial and digital indicators, test indicators, 80lb 72" camelback scraped straight edges and a 6000lb 4' x 8' x14" surface plate , And I have never used any of them to setup or check my jointer. I use them for metalwork, they are recent acquisitions, I built a lot of furniture before I ever got them
All that you need to check a jointer is a verified straightedge, and that could be a piece of wood.
Check and verify that the individual tables are flat first. ( you need five reference points, the four corners and the center)
Then check that the tables are co-planer.
Then check that the tables and cutterhead are aligned ( cutterhead axis is parallel to the table)
check you knife protrusion.
set your infeed and outfeed table heights.
dress a stick and make any fine adjustments on the outfeed table to TDC of the cutting circle.
Joint a few pieces of wood, check for fit, adjust either the outfeed height or you technic to make fine adjustments to the results.
I have done precision woodworking for 50 years
Woodworking is not difficult, people make it difficult, they overcomplicate, or the overlook the basic concepts. If you miss the basics everything will be complicated and no amount of tools will make it easier.
My suggestions is to learn to do things without measuring tools. Learn to check flat, straight and square etc without tools, set up your jointer by dressing wood and reading what are the problems, if its the jointer or you. Check that your joiner fence is square, by dressing a couple of pieces of 1x6 placing the dressed edges on the jointer table, back to back, then flip one around, what does it tell you? Check the knife protrusion from the cutterhead with a stick, a pencil mark, check the outfeed table to top dead center with the same stick. Check you tablesaw the same way, the mitre slot to the saw, with a stick, the blade perpendicularity to the table, with a stick, the miter fence perpendicularity the the saw... with a stick. All of this is more accurate then measuring. Don't measure anything that you don't have to. I don't use a tape measure or a ruler, I use a story stick and transfer knife-lines. I sincerely doubt that anyone using expensive metrology equipment can get anything more accurate than me using a couple of sticks. My point, is learn the principles, understand the relationships, and how to check and reference things.
If you understand the relationships, for most things you wont need to measure anything. I you don't understand, then you have to trust your tools, and without being able to check and verify them, you will be working on blind faith, and that's not how I like to work. I prefer to know.
The basics are the foundation.
You need to understand wood, cell structure and moisture exchange, movement and strength, so that you can design properly and avoid all of the big mistakes that come from not knowing.
You need to understand referencing and relationships to be able to accurately set up you tools and machines, to set up your process and to be able to avoid cumulative errors.
You need a little bit of knowledge and the rest is project management.
Just my opinion, everyone has their own way of doing things.
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