Here is some more poor man’s stuff for you to try. This week I went into Aldi with Liz and saw some granite worktop (countertop) savers reduced for closeout. The packages were torn. Now I do have a bonafide granite block certified to engineering tolerances so I didn’t need any more but for most people this is an overkill. I picked up two of the 30counter savers and placed them face to face and they looked gap free on all four edges. This is is a good start, but they could both be hollow. The offer was two for £5, so a reduction of £3. At £2.50 a piece this makes a granite test surface doable for anyone, but only if near flatness is a reality. I bought the four granite worktop savers and tested them out. Using feeler gauges and the straightedge in my square, and winding sticks too, three of them were flat across whichever way I tested them with no gaps that I could feed any feeler gauge through. The fourth one was out by 0.06mm (about 2.36 thou) in one small area. Nothing to worry about here, most woods compress as much or more than that and if it doesn’t then the fibres can certainly be pulled up into the plane mouth that much. Now I know some might say that’s too much and it’s not really very scientific, but it’s really not at all.
In my transitioning betwixt workshops and living and working zones my own block is still in storage so this was the last testing I wanted. Buying worktop savers gave me instant testing capabilities I could apply to the three planes and guess what? They did test out very well. The best one was the Silverline followed by the B&Q and then the MACALLISTER. None of them were far enough out to not be used straight off in the case of my selection but you will have to try as best you can to test out your own. These three planes could be dead flat in a few strokes on the granite worktop savers.Remember an out of flat plane is a good enough reason to change it out. Also remember that there are no guarantees with any of the planes you buy. Just because it says in the catalogue tested to this or that flatness doesn’t mean it will be. High end models can be out too.
There are a couple of pockets you get in granite 3-5mm across, but these don’t affect the functionality of the granite as a proving surface as a surface suitable for flattening with abrasive paper. A little light misting with spray adhesive and you are on your way.