Re: probably done to death... but going to ask anyway. blade popping off.
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Popping the blade off the bottom wheel (esp. when cutting in the vice or pushing hard on the blade in vertical mode) is very likely due to the bottom guide bracket (the casting with the two side guide rollers and the rear support roller) being too far forward on its guide bar.? If this is the case the bottom rear support roller will be turning all the time and it will be difficult to stop with your fingernail (correctly set it is easy to stop).?? What happens to pop the blade off is the weight of the sawframe in the cut pushes the blade backwards, between the top and bottom rear support rollers, and then the lower rear support roller (which is too far forward), acts as a fulcrum to lever the blade off the bottom wheel. There is a 5/16" bolt that controls the backwards and forwards movement as well as the twist of the guide bracket (more on this below).?? It should be set so that the rear support roller only just touches the blade in hit&miss fashion as the blade rotates, even a slight (~0.040") gap is O.K. (it's not like a wood bandsaw where the rear support roller setting is critical to good cuts - these horizontal vertical saws are very tolerant to rear support roller position - as long as it's not forward of the right position). One of the hardest things to set is the position of the guide brackets on their guide arms via that 5/16" bolt. since both backward/forwards and left/right twist is done at the same time.?? There is a very simple mod to separate the two adjustments.? Drilling/tapping for a small bolt (3/16"?x 1" (UNF is better than UNC, but there's?no weight on it so either will do) or M5 x25mm) though the picture shows an M6x25 bolt) in the back of the guide bracket as in the photo. This allows the rear support roller to be set independently of the twist of the blade. Just centre pop and drill with a handheld drill in the centre of the back of the bracket casting, then tap. Picture shows the upper bracket not the lower one because it is easier to see. Do both of them. While you're at it replace the metric headed UNC bolts with cap head screws and decently thick washers as in the photo. Use a nut to lock the bolt in position?once you've set the rear support roller-to-blade back clearance - jv On Wed, Feb 7, 2024 at 5:34?PM Wolf Gang via <wolfgang_90=[email protected]> wrote: I've got an older harbor freight 4x6 bandsaw that is probably 20 years old. It's green if that helps, and if I saw lightly, in ether horizontal or vertical mode, it seems to work. If I push on the work like my old saw, it pops the blade off the bottom wheel. I have not gone and replaced anything yet. I did change the oil (first time I think) and took the top wheel apart and put it back together with tighter tolerances. I've replaced the blade twice.? |
John Vreede
