It is currently 29 Mar 2024, 10:31
Gremmy wrote:Trevanion - yes I do use reducing bushes, and they are thinner than the body of the saw blade and they are turned not stamped from sheet metal. There isn’t enough room for the bush to work loose into the flange void, and I’ve superglued it in place. I’ve hoovered up your saw blades info and made sure that I’m up to speed with it. Have I preempted your thought process on the bushes?
I still don’t have a definitive answer, so will just ensure I’ve heeded all advice given, and be more careful changing my blades and tightening nuts!
Trevanion wrote:
I'm not really sure what's caused the problem aside from not being tightened properly initially, even if you caught an offcut on wind-down it would still want to tighten the blade because of the left-hand thread.
Doug71 wrote:Trevanion wrote:
I'm not really sure what's caused the problem aside from not being tightened properly initially, even if you caught an offcut on wind-down it would still want to tighten the blade because of the left-hand thread.
I would have thought if the blade hit an offcut on wind-down it would cause it to decelerate but the nut would want to keep spinning in the direction it was going (clockwise) so would want to unscrew?
I only suggest this because on our old Wadkin spindle moulder that had a hand operated brake sometimes if you braked it up quickly (and my father had tightened the top nut ) the shaft would stop spinning but the top nut would keep going and unscrew itself
I do think the nut not being properly tightened on the saw was probably the main factor in this incidence.
Trevanion wrote:Doug71 wrote:Trevanion wrote:
I'm not really sure what's caused the problem aside from not being tightened properly initially, even if you caught an offcut on wind-down it would still want to tighten the blade because of the left-hand thread.
I would have thought if the blade hit an offcut on wind-down it would cause it to decelerate but the nut would want to keep spinning in the direction it was going (clockwise) so would want to unscrew?
I only suggest this because on our old Wadkin spindle moulder that had a hand operated brake sometimes if you braked it up quickly (and my father had tightened the top nut ) the shaft would stop spinning but the top nut would keep going and unscrew itself
I do think the nut not being properly tightened on the saw was probably the main factor in this incidence.
That happened on the spindle because you were applying braking force to the shaft, not the the blocks on the shaft as would happen if an offcut came into contact with it.
The weight of the cutter blocks or blade causes inertia, when you apply a braking force to the spindle the intertia of the blocks wants to keep spinning on whereas the shaft is trying to come to a stop, since the nut is left-hand thread the spinning force of the cutter blocks is enough to undo it.
Doug71 wrote:Thanks Trevanion, that makes sense.
Quick thread drift but kind of related. On spindle moulders that can run backwards do they have a special nut/bolt to lock down the block? In the past I have thought about running mine backwards to make certain moulds easier, it's not meant to run backwards but it's three phase so I figured I could just swap a wire round. One of the things that stopped me was the fact that the block would be running the wrong way for the thread on the nut, it wouldn't be tightening when it was running, would you see this causing a problem? At least the nut shouldn't spin off when I brake hard
Trevanion wrote:
You also need to make sure that the shaft won’t end up unwinding out of it’s socket either!
Doug71 wrote:That could be quite an interesting experience think I'll stick to running it forwards. Thank you.
What he says.Trevanion wrote:...
The weight of the cutter blocks or blade causes inertia, when you apply a braking force to the spindle the intertia of the blocks wants to keep spinning on whereas the shaft is trying to come to a stop, since the nut is left-hand thread the spinning force of the cutter blocks is enough to undo it.
Vann wrote:What he says.Trevanion wrote:...
The weight of the cutter blocks or blade causes inertia, when you apply a braking force to the spindle the intertia of the blocks wants to keep spinning on whereas the shaft is trying to come to a stop, since the nut is left-hand thread the spinning force of the cutter blocks is enough to undo it.
The same forces that want to tighten the nut on startup, want to undo the nut during rapid deacceleration. And I'm assuming you have an electric brake on this saw. I'd guess catching the offcut must have caused some additional harmonic - just enough to overcome the friction holding the nut.
I know nothing about electric brakes. Is it possible to slightly reduce the braking (increase the rundown time) to reduce the "undo" forces?
Cheers, Vann.
RogerS wrote:I don't think electric brakes generate that amount of braking force to influence the nut tbh. It is certainly not instantaneous....nothing like.
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