Video - Saw Blade Protection

[Radio Fixer]

http://www.youtube.com/watch?v=wFp62jDcoFM&feature=related

Now this is really clever and I would want it if I used such saws.

Gary

[pwdrive]

Well I guess I had to comment on this, no saw guard!! no push stick!! not to mention that his invention could soon be rendered useless by an excessive build up of sawdust in the works...

Lawrence.

[Joe]

I wonder how may saws would get wrecked through damp wood?

Like all such things there's a danger that it could give a false sense of security and be used instead of normal precautions.

Certainly interesting though.

- Joe

[pwdrive]

I agree.
All circular saws should have the correct riving knife fitted and correctly adjusted, a blade guard fitted and correctly adjusted, cut out/isolating switch. Fingers/body parts should be nowhere near the blade, safety device or not.
A properly designed push stick should always be used when feeding the end of the wood through.
Small saws breed contempt.....

Blah, blah, blah.

Lawrence.

[Radio Fixer]

But with refinement he could be on to something... Put the guards on and the push sticks as well

False triggers could be a nuisance to say the least!!

What was it 10 accidents a day? So a lot of folks aint doing it right

Gary

[Geaney]

I fully agree with having all the safety gear in place and adopting safe practice, etc. I remember years go in school our woodwork teacher was demonstrating something on the table saw - the blade kicked back and shot the long 2x1 offcut like a spear clear down to the end of the workshop where it ploughed through the door of one of the tool cabinets up on the wall. I can't remember what the exercise was about but I will always remember that spear sticking through the door!

Teacher went a bit pale as I recall!

Cheers, John

[Joe]

One of ours took his index finger off.

- Joe

[pwdrive]

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.

[Radio Fixer]

Scary stuff Lawrence ...

Gary

[pwdrive]

Hi Gary, It can be scary but to be honest most accidents I have seen etc have been caused by small saws/cutting equipment, I always felt safer operating the large breakdown saws than using a small plate or crosscut saws.
I wrote that bit on wood tensions in haste.... the general term used is "reaction" wood ie: wood under compression (mainly softwood) and wood under tension (mainly hardwood) Compression wood grows on the downside of softwood trees and tension wood grows on the upside of hardwood trees (when leaning)
The side of the wood with a high lignin content in that context also shrinks noticably along it's length as it dries out which adds to the problem, unlike lengthways shrinkage in normal wood which is usually minimal.

The enclosed picture is of a saw I operated many years ago with a friend of mine, it was eventually taken out and left out in the open in bits for 15 years! The picture shows our recent re installation of the said saw to date.
The headrig shown is a Stenner VB42 the bandwheels being 42" diam. which are designed to take a 5" band blade, the bottom band wheel is down in a concrete sawdust pit (which I built) where the intake for the sawdust blower also resides, the feed tables are 30ft long being designed to take a 30ft log, the rollers run for just over 60ft to accomodate the tables, the saw runs off a 40 hp electric motor, the rack drive under the tables is driven by hydraulics via a small electric motor, the fence is driven by an electric motor also. The Stenner saws were and still are world renowned. They can be often seen at traction engine rallies in full swing, usually the earlier Stenner & Gunn rack bench plate saws.

Lawrence.