03-11-2012, 10:01 AM
Timber pinching on the blade is very common, especially with softwood timbers, the main cause is a high lignin content and it's disproportionate growth rate, as a once full time sawyer I have experienced it many times, it can be dangerous.
I once operated a 5ft plate saw, a saw that size needs a lot of gee gee's to power it, it can pickup a 12ft x 6" log and spit it out no problem.
Larch was the worst, the high lignin content is normally a result of the tree growing on a slope and leaning, the lignin is put on to support the underside of the tree.
A good way to decide wether or not the timber is going to react is to check the end grain of the timber before shoving it through the saw, the lignin is generally a lot darker in colour and shows up in the growth rings predominately on one side, you can also check the hardness of the ring (don't confuse the early wood with the late wood) those with a high lignin content are very hard compared to the rest.
The saw guard can help mitigate the effects of the flywheel/cranking action by being set to the correct hight ie: set it as low as is practical.
Some times as you feed such timber into the blade, you can hear the blade slowing down a bit as it starts to grab, at that point you can withdraw the timber and feed it in again, doing this repeatedly and advancing slowly can relieve the tension as you proceed.
The danger generally arises once the feed end of the timber has passed the axis of the blade heading towards the rear outside edge of the blade.
Radial arm crosscuts can be equally as bad if crosscutting timber that is under tension or is bent, the shorter the piece of timber the worse it can be, often resulting in a large bang as the bits fly everywhere.
If there is a gap between the timber and the backstop then the blade is going to bite, avoid.
In such crosscutting situations I find it best to cut with a handsaw cutting slightly overlength then trim on the crosscut saw to the exact length required.
Pinching can also jam up a wide bandsaw blade, I remember one occassion when we were breaking down some larch sawlogs, we were running a Stenner rig with a 5" band powered by a large six cylinder diesel engine, shortly after the back edge of the band had dissapeard into the sawlog the log pinched up and stopped the whole rig, such are the forces involved.
Most of the above will be familiar to most but if not familiar then beware, play safe.
Lawrence.
I once operated a 5ft plate saw, a saw that size needs a lot of gee gee's to power it, it can pickup a 12ft x 6" log and spit it out no problem.
Larch was the worst, the high lignin content is normally a result of the tree growing on a slope and leaning, the lignin is put on to support the underside of the tree.
A good way to decide wether or not the timber is going to react is to check the end grain of the timber before shoving it through the saw, the lignin is generally a lot darker in colour and shows up in the growth rings predominately on one side, you can also check the hardness of the ring (don't confuse the early wood with the late wood) those with a high lignin content are very hard compared to the rest.
The saw guard can help mitigate the effects of the flywheel/cranking action by being set to the correct hight ie: set it as low as is practical.
Some times as you feed such timber into the blade, you can hear the blade slowing down a bit as it starts to grab, at that point you can withdraw the timber and feed it in again, doing this repeatedly and advancing slowly can relieve the tension as you proceed.
The danger generally arises once the feed end of the timber has passed the axis of the blade heading towards the rear outside edge of the blade.
Radial arm crosscuts can be equally as bad if crosscutting timber that is under tension or is bent, the shorter the piece of timber the worse it can be, often resulting in a large bang as the bits fly everywhere.
If there is a gap between the timber and the backstop then the blade is going to bite, avoid.
In such crosscutting situations I find it best to cut with a handsaw cutting slightly overlength then trim on the crosscut saw to the exact length required.
Pinching can also jam up a wide bandsaw blade, I remember one occassion when we were breaking down some larch sawlogs, we were running a Stenner rig with a 5" band powered by a large six cylinder diesel engine, shortly after the back edge of the band had dissapeard into the sawlog the log pinched up and stopped the whole rig, such are the forces involved.
Most of the above will be familiar to most but if not familiar then beware, play safe.
Lawrence.
