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You can buy top-of-the range kit brand new or get what you need second hand. I tend to use the latter.
Here’s what I use:
Marking;
I use engineers’ squares, Plenty going on fleabay. A little 4”, 6” and a bigger 10” is what I use all the time. The biggest one is a bit of a luxury for wider boards.
Marking Knife. A few folk make their own but Axminster do a double edged V point Japanese one for about £14.
A cutting gauge is very useful for delineating the cut line.
Planes:
Moving fillister planes are quite cheap. Record 778 is a useful buy, you can fit your own wooden fence.
Likewise a side rebate plane. There are lots about. I have a few and use the Stanley double ended one mostly.
Rutlands used to do a long (about 13”) Chinese wooden rebate plane which was excellent for finishing both the base and side of long rabates. I can’t see it in their catalogue any more but if you do see it –get one - they are very good!
Dado planes are an option, but these are invariably wooden and good ones tend to be expensive.
Chisels
The only chisels I use for cross-grain trenching are a couple of long paring chisels. I also use a paring chisel to cut away the sides of dados against the scribe line so that the saw sits and starts in a clean groove. Unfortunately these tend to be expensive, but it's best to get the best.
OWT routers are also plentiful for opening a dado after you have cut the two sides, but personally I can’t get on with these; they are difficult to control and a pain to keep re-setting. Best to use these for finishing the dado floor.
Saws.
A good cross-cut is useful, (16 – 18 tpi) but unless you are certain of the quality, old ones are usually knackered and need a lot of work. Best to buy new - the Veritas range is good value.
As well as fleabay, there are some dealers around. Search for Alf’s website where she has a list of UK dealers. The guy in Beer, Devon is very reasonable and helpful.
That should get you going.
After that you need to look at sharpening kit..................
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