Nige,a 3600 will normally have 0.34mm to 0.5 crush on the bearings.( 14 - 20 thou ) A handy rule of thumb for steel bearings in Nitrogen is that that they will shrink 2 thou per inch of diameter. So 3600 bearings will come down around 20 thou. They will start expanding the moment you get them out of the liquid. With Hitachi's I would normally heat the bore to 150 C minimum. Use a big soft flame and be careful to heat the hole evenly. No heating inside the bore! A infra red temp gun is the go and remember they will give a dud reading on a machined surface.
Another rule of thumb is a 12 inch bore will expand 1 thou per 10 deg C, A 6 inch bore half a thou etc. To start a 10 inch bearing in a bore and you have limited time you need a fair amount of clearance.
Now those other diggers,
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Liebherrs (which without line borers would be broke) only run a max of 4 thou crush.And if you bore them up on the top of their tolerance can be only 2 thou, you don't need any heat when using nitrogen. You can toss the bearing in from 20 feet.
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With bronze bearings rule of thumb for shrinking in nitrogen is 4 thou per inch of diameter. You will never need heat to put them in. The first time I did a RH200 stick I panicked. I had bored around a 300mm bore and shrunk the bronze bearing and it went in with so much clearance I was sure I had machined the hole a mm to big. Had to pull it out and check.It was correct so put the bearing back in and it was 5 or so minutes before it got tight.
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