Re: how to square vertical cutting table?
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Hi Mark You ask what brand blade to use.?? In my experience it doesn't matter much what brand you use so long as it is the right teeth count for the material?and saw. I've made a bit of a thing about blade performance and have tried?all the blades I can get my hands on, which is by no means all of them, but enough to get a picture: Starrett (US), Lenox (US), Bruel (Germany), Rontgen (Germany) BiChamp (China), iMachinist (China)??Hakkonsen?(Sweden) and Bahco (originally?Swedish but now a Snapon brand made in Belarus). I've trialled cutting performance (how fast it cuts through a 4"x 5/8" bar and how that changes over 100 repeat cuts), of all the Bimetal blades and there was no statistical difference between them ($7US iMachinist blades off AliExpress to?$35US Bruel imported coil welded in NZ).? I've never 'worn-out' any of them!
When people?say "Buy a good blade" they are mostly talking about?buying a 'Bimetal' blade, which has high speed steel (HSS) tips on a high tensile steel band. There is an intermediate type of blade called Hard-Edge-Hard-Back (which has teeth ground into the same band material as Bimetal blades) and then the 'lowest quality' Hard--Edge-Flex-Back which is generally called a 'Carbon steel' blade. The bimetal blade will cut a greater range of harder metal, but treated properly (proper feed rate with right teeth-in-cut on appropriate hardness material) the others last just as well, better in fact when they're half the price! The machinery and process to electron beam weld HSS tips on the teeth is not cheap and not many people have it.? At a guess I'd say only a few of the very biggest mnfrs (probably Lenox, Morse, Rontgen Bahco etc) have the gear to do it, and all the others will buy coiled stock from them and grind, weld and trademark it themselves, or get theirs made by the big ones as a 'house brand'. That said, there is a big difference between the welding?of the different manufacturers and their local?distributors, who make from?coil. This takes into account loop length, alignment of both sides across the joint, annealing of the weld and grinding of the weld-flash at the joint.? The best aligned, loop length and grinding control has been Rontgen - it must be CNC controlled to get them so uniform, however there was something wrong with the annealing?setup that day, and all 3 blades I bought broke at the weld, yet the Rontgen blades I've bought that were welded here in NZ were always OK. The iMachinist blades were very well aligned (better than the Lenox or Starrett) but had far too much ground off the joint - the tips of the teeth were gone on both sides for 3/4" on each side of the weld which made it squeal every time the joint went through the work esp when cutting wood. You can tell how well the grinding has been done by running the joint?in the blade between your thumb and forefinger.? You'll feel the prickle of the sharp points except where they've been ground off.? Done really well, like the CNC controlled Rontgen, there's?less than 1/4" on either side of the weld (1/2" total). The blade should NEVER break at the joint - take it back for a refund or another?blade if it does, no matter?how old. A bimetal 10-14 TPI vari-pitch, nominal 1/2" wide x 0.025" thick blade is 'the standard'? blade for 4x6's.? It's the blade to have if all you cut is 1/8" thick or thicker steel, set to run at about 7-8lb bow weight. However it is completely the wrong blade to cut aluminium; it will clog the teeth and cut crooked. A 4 to 8TPI straight pitch carbon blade (only bimetal blades are vari-pitch) will cut aluminum?all day dead straight at 5lb bow weight, much?faster than a 10-14.? Heat is the enemy of tooth sharpness.? HSS has MUCH greater hot hardness than carbon steel so resists the heat generated by cutting hard steel like high tensile or tool steel, and the heat from cutting stainless steel, which workhardens when cut by a bandsaw (so many teeth at such thin?cut-per- tooth) and is a very poor conductor of heat, so almost all the heat of cutting goes into the teeth which rapidly softens a carbon steel tooth. By comparison aluminium is?an excellent heat conductor and no matter?how fast you feed it, the tooth will never get hot enough to de-temper. At similar TPI, bimetal blades do not cut aluminium any better than carbon steel blades.?? I think the lesson is:?
On Sun, Nov 6, 2022 at 2:16 AM mark lacombe <Lacombe1958@...> wrote:
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John Vreede