Thread: Help with components

Originally Posted by John Samuel

In the next few weeks a new dust extraction system will be installed in my shop, and I have some questions about components.

TABLE SAW. My saw is an old contractor's saw. The cabinet hopper works a treat and will get better when it is upgraded to a 150mm port, but I need to hook up an overhead guard/shroud to collect dust with a 100mm port. I was going to make several things, including this shroud and a method of attachment (overhead), but am running out of time and right now I have nil dust extraction from the top of the table. So, will try to buy several items to speed matters up. This is one of them. Can anyone help with sourcing a suitable guard/shroud, preferably with a 100mm port?

I have only see home made versions of these.

DUCT BENDS. I was planning to use two 45 degree bends with a straight section between them instead of a 90 degree bend in my ductwork. However, at Bill Pentz's site he says two forty-fives equals one ninety in terms of resistance. Should I just use nineties?

2 x 45º is equivalent to a 90º bend with a radius of 2.0 X (Pipe Diam Radius), actually it's a bit more than 2 but close enough. If you can find 2 x PDR 90º bends then use them, the 90º bends I could find were all <1.5 x PDR

When I was an apprentice, you could buy bends or elbows. Elbows were pretty sharp with a radius about the same as the diameter ... not good ... but some manufacturers made bends that had a big radius. Sadly, I have been unable to find them anywhere. Are these big radius bends still around? If so, can anyone help with where (I am in Brisbane)?

I haven't been able to find these

John as far as finding an overhead guard with a 4 inch outlet...good luck.

I baught an overhead guard system when I baught my saw bench, it came with a single 2 1/2 inch outlet.....which seems to be typical......this was not good.

With no hope of getting a 4 inch pipe into this guard....( simply not wide enough)....I grafted a pair 3 inch outlets onto it.

They connect via a couple of short lengths of flexible into the rigid 4 inch pipe that comes down the arm.

This connection was achieved by "Soundman's Trouser Adaptor".

what I have done there is take a 3 inch dust hose coupler.
Cut it straight down the middle, giving two identical parts to connect the 3 inch hose to.
Then you have to cut a slice of the side of each to make up a Y, glue this up with conduit cement and hold in place with strong tape.
the Y is completed by heating up the end of a length of 100mm PVC pipe and forcing it over the y just made.......this will need some pushing and shoving, and heating and pressing various parts.
BUT the PVC can be formed to a good fit with the "Y: that has been made.
once cooled and satisfied that it is a fit, glue it all together with sicaflex and fill up any holes left by inadequacy in the fit.

I call it a trouser adaptor, because when finished that is what it looks like.
It is neater and better flowing than a conventional Y...if you could get one that goes 3 inch DC pipe to 100mm PVC.

As for the 4 x 45s making up an 90......yes and no......if the 2 x 45s have a wider radius than the 90 they will flow better.

There is the need for a 90 deg bend on my overhead guard, I did this with two 45s and it is obvious that the bend radius is way wider.....plumbimg 45s can be had in male to female and female to female.

a male to female pluged into a female to female makes a very much wider bend than a single 90.

OH one thing....stay way from flexibles as much as possible

cheers

Thanks, Soundman.

I think I am about to abandon the fantasy of buying a decent guard and make my own guard out of 10 mm polycarbonate. If I do, I'll likely use the Shark Guard as a guide. It's the only one I've seen that traps/slows down the dust coming towards the operator of the top of the blade and which is open enough (at the back) to allow good airflow.

Looked at the latest Grizzly overarm noted here T10113 Universal Overarm Blade Guard For Table Saws At first I liked the clean, simple lines ... but that did not last long. How do they pull air through the guard/shroud? It is so snug to the table. I reckon what it would do best is pull the throat plate out of the saw table.

If I do make up a guard, I'll probably use 90 mm pipe as a port for the guard and a 500 mm long piece of 125 mm dia pipe for the cabinet (which I'll make myself). I'll grow a socket on the end of these short pieces to take 100 and 150 mm ducting.

I will use PVC wherever possible, but some flex hose is unavoidable in a shop where the machines are all on wheels, are stored against a wall and pulled into position for use.

In a previous life I was an apprentice plumber. I would kill for some of those wide radius bends we used to have available at the time. As you indicated a MF and FF 45 degree bend/elbow seems to be the way to go.

I have a wild idea for the overhead arm on my TS. It should be possible to slide a 90mm pipe into a 100mm pipe with, say, three small timber spacers to keep the two pipes separate Then we could drill holes in the bigger pipe and pump in the polystyrene gap filler that is now available. I reckon this would make a much stiffer pipe. Still a wild idea at this stage. All will be revealed in the fullness of time.

Hi John,

Bob has a picture of his O/H guard on here somewhere - its very good and a generic design. I put a 4" port on mine too but is specific for my saw so not much use for copying. I hate to recommend them, but Gregorys Machinery has wide radius bends in metal I am sure.

If you are so inclined, I think building yourself is the only way to go.

If you are looking for PVC that slides ine inside the other you need to have a foot in two camps.

Electrical conduit is measured on outside diameter and plumbing pipe is sized on inside diameter......combine the two and they sometimes slide or at least nest.

50mm conduit definitely glues into 50mm plumbing pipe.

As for the guard sealing to the bench top....yeh the better the seal....more like the smaller the gap the better the resut will be........there will always be enough gaps to let the air flow...for practicality the front needs to be a little open likewise the back.

I see if I have time to clean up my saw bench enough to take a photo.

cheers

Originally Posted by John Samuel

When I was an apprentice, you could buy bends or elbows. Elbows were pretty sharp with a radius about the same as the diameter ... not good ... but some manufacturers made bends that had a big radius. Sadly, I have been unable to find them anywhere. Are these big radius bends still around? If so, can anyone help with where (I am in Brisbane)?

For a possibly longer radius bend maybe have a look and compare an inspection bend with an ordinary bend, I was having a look at one a while back and they did seem to be a longer radius.



Pete

Thats given me an idea......electrical conduit bends are definitely avaialble is large radius and in large sizes.....not cheap, but available.
The only problem is that there would be a diameter reduction....small though it may be.

A 100mm conduit bend with the flares cut off would fit inside a 100mm plumbing pipe....if the ends where faired up it may end up being less lossy than anything that could be done in plumbing fittings.

The problem with the inspection bend is the turbulance that would be casued by the hatch.

cheers

Originally Posted by soundman

Thats given me an idea......electrical conduit bends are definitely avaialble is large radius and in large sizes.....not cheap, but available.
The only problem is that there would be a diameter reduction....small though it may be.

This has been discussed before
See ELECTRICAL CONDUIT, FITTINGS - ELECTRICAL FITTINGS PVC - Perth Irrigation - Retic Fittings , Plumbing Fittings, Reticulation Supplies, Western Australia
100 mm diam large radius bends cost ~$50
The last time I enquired a 6" diam large radius bend was more than $150.

Communication PVC pipe is a about half that
see ELECTRICAL CONDUIT, FITTINGS - COMMUNICATION FITTINGS PVC - Perth Irrigation - Retic Fittings , Plumbing Fittings, Reticulation Supplies, Western Australia
I could not get any 150 mm when I enquired

6 x 15º bends in 100 mm diam will cost ~$12, but unfortunately ~ $80 for the 150 mm.