Thread: A Funny Thing Happened Today

Hi,
The best glue for perspex is perspex dissolved in acetone or just softened with acetone and melted together. Unless the formula has changed since the last time I did some or you have some newfangled material.
Regards

I think that is what I was given today. He was telling me how he dissolved the "plastic" to form the glue. Apparently there are two types, one based on chloroform and one based on ether, or that is the way he described it to me. It was all good because if it had been glued properly I would have to re-make the whole thing due to the noise. I had to put ear defenders on, it was that loud.

Chris, my Sharkguard from Lee Styron arrived 6 weeks ago, its quite well made I think, But I still prefer no guard....

+1 For Lee's Sharkguard with the 4" dust port.
I've had mine about 2 years and use it constantly. come's off easily for dado's or other similar situations.
Cheers, Ian

Albert I have never been convinced of how well any of the conventional hoods work including the shark guard. A blade operating at thousands of RPM sprays debris everywhere and there is no way that a conventional guard which has clearance under it can prevent the escape of the really fine stuff or if it does I have never seen proof of it. They do mostly grab nearly all the larger debris and some of the fines that much is evident but there must be some escape. The problem has always been sealing against the cut material in such a way that air flow is at a maximum through the hood. Mine does both but I can't take any pics until I get it back into one piece. I haven't actually worked out how to mount it on my saw yet but that is only a minor matter that glue and bits of perspex should resolve.

Originally Posted by Chris Parks

Albert I have never been convinced of how well any of the conventional hoods work including the shark guard. A blade operating at thousands of RPM sprays debris everywhere and there is no way that a conventional guard which has clearance under it can prevent the escape of the really fine stuff or if it does I have never seen proof of it. They do mostly grab nearly all the larger debris and some of the fines that much is evident but there must be some escape. The problem has always been sealing against the cut material in such a way that air flow is at a maximum through the hood. Mine does both but I can't take any pics until I get it back into one piece. I haven't actually worked out how to mount it on my saw yet but that is only a minor matter that glue and bits of perspex should resolve.

The Sharkguard is not perfect but it stops the majority of the fine stuff spewing out at great speed, I think there are some video on youtube that will explain this but yes you are correct in saying some will escape, its better than no guard I must say ....

what about using 1-2 large commercial fan flowing in the direction of the saw dust, and then a large extraction hood at the downwind or opening to outdoor like garage door to help in "extracting" the dust, like a wind tunnel... the speed of the wind required to take away 99% of the dust probably meant the user has to wear goggles lol

Like Bill Pentz and others the best way is to stop the dust getting airborne in the first place. I suppose it has always been an issue that to me had never been addressed in a suitable user friendly way and I like solving problems like this. When I sort this out I have an idea regarding router tables, now they are a real problem waiting for an answer!

This one is made from perspex and timber and I used Polyurethane glue (Titebond) to glue P to P and P to T.

That looks nice Brett.

Originally Posted by Chris Parks

Albert I have never been convinced of how well any of the conventional hoods work including the shark guard. A blade operating at thousands of RPM sprays debris everywhere and there is no way that a conventional guard which has clearance under it can prevent the escape of the really fine stuff or if it does I have never seen proof of it. They do mostly grab nearly all the larger debris and some of the fines that much is evident but there must be some escape. The problem has always been sealing against the cut material in such a way that air flow is at a maximum through the hood. Mine does both but I can't take any pics until I get it back into one piece. I haven't actually worked out how to mount it on my saw yet but that is only a minor matter that glue and bits of perspex should resolve.

Yes I agree with you and Albert Chris and concede that even the best hood will never stop all the fine dust due to the speed of the blade. Most dust however can be captured with a well designed hood under normal use if there is a minimum 6" system under the saw and a 4" port on the hood over the blade.

It all goes to hell though when you make small trim cuts which allows tons of both visible and invisible dust to escape out of the side of the blade under the hood where it is not shielded by an off cut and I don't believe this will ever be able to be satisfactorily stopped. I'm sure most of us have seen the various "skirts" of different materials hanging outside several home made guards but these to me add more problems than they solve.
Look forward to seeing what you have come up with Chris.

Cheers, Ian

I have wondered about this myself. Has anyone tried brushes that extend from the hood down to the stock being cut ?

We use them in the IT industry in data centres to provide openings in floors and cabinets that allow cables to pass through while still minimising air leakage.

The brushes we use are similar to those you might see on the mudguards of trucks to reduce spray.

The open side when trimming is easily overcome with a sliding skirt that can be varied in height and locked at the required height. I suppose it would be possible to actually use a friction locking system instead of a threaded knob to lock it but a half turn of a knob would not be to onerous on the operator. I have not looked at that particular problem yet, concentrating instead on preventing dust escape on a full cut and I have got that to a point where nothing can escape at all even using a minimal flow air extractor, my experiments are being done using a Clearvue 1800.

I have for a long time pushed the idea of brushes but I have taken the view that the long brushes that I have linked to previously are not a really good idea at all, not because they don't trap the dust but they must impede the view of the operator. I am still using a brush skirt all round but it is very short in the order of 20mm being a brush from a door which is readily available and easily attached.

The commercially available hoods without fail all ride above the material and the air flow cannot control the velocity of the dust as it leaves the blade, the fines escape and on some the larger saw dust as well. To run the base of one of these hoods on or close to the top surface of the material being cut prevents air entering the hood at the required volume to feed the dust extractor so it stops working at peak efficiency. The answer to the whole thing is having sufficient air entry while the hood is sealing against the material being cut. It isn't rocket science but up until now no one has looked at the whole picture which as we know is a constant issue with DE and machines in general. Alan Shaffter in the US who designed and built the brushed hood I have linked to here came the closest so far but his brushes are way to long but being long a lot of air most probably went through them though I doubt it was ever enough. The brushes on mine being so short will never allow enough air entry but will prevent dust ejection which is all they should do.

Make up air in DE is still the unrecognised problem by anyone in the commercial end of the industry and by most at the hobby end but it is at the hobby end that it has at least had some recognition. To illustrate the point, I watched a video put out by Laguna and the MD of Laguna was proudly pointing out that they had put better sealing around the lower door of their bandsaw to enhance better DE where in fact it made the DE worse due to less air being able to enter. CNC dust shoes are also another area which can suffer from this as well along with just about all other machines we use that has a cabinet or hood.

Have you gents given any thought to adding high pressure air from the shop compressor to nudge the dust to the into the collector pipe?

A nozzle or two under the table, blasting the blade to clear the wood chips and dust from the teeth. A nozzle in the blade guard doing the same when the teeth come out the top of the cut to send the chips and dust where you want them to go.

The high velocity air will redirect the dust and add to the air volume in the blade cover to make up what is being removed. Added complexity for sure but may work.

Pete

Pete, as long as I can guarantee that the hood will trap and pick up the debris and fines I would rather they stay attached and be ejected at the top than try and extract through the cabinet port. Cabinets present other problems and never get completely clean though that is no problem in as the build up only goes so far.