Enlarging Bandsaw DC port (OT?)

[Greg Keddy]

I've recently picked up a cyclone and I am in the process of setting up the shop so that all of my machines have the equivalent of a 6" pipes worth of dust collection. I've run into a problem trying to enlarge the port on my bandsaw from 4" to 5". It's an awkward location, so a jigsaw won't fit, and the recip saw with a metal blade won't cut that radius of circle. I've seen such a diverse range of experience on this forum, I'm hoping that there are some metal working wood turners out there.

Any advice welcome.

 

[robo hippy]

I was lucky, mine had a plastic rectangular port on it which I was able to screw off, and then enlarge (Laguna 16HD). Bad thing was it didn't help. I am still thinking of cutting out on the bottom of the lower door, which is where all the stuff the DC doesn't pick up stacks up, and install a floor vent, maybe 4 by 12 opening with a 5 or 6 inch port on one end (to the back of the saw). The hose would be out of the way and shouldn't get in the way when opening the door. As is, the vent is in a back corner of the bandsaw, kind of behind the main vertical structure of the saw. Bad idea.

robo hippy.

 

[Harry Robinette]

Greg
I did the one on my old Jet 14" with my Air Body Saw small reciprocating saw run on air. Only need's 90# of air and you have to hold it back cause it loves to eat sheet metal. Got it at HF for $19.95 on sale. It gets into places nothing else will.
It works great on wood to I got mine after seeing Trent B.demo he uses one allot.

 

[Paul M. Kaplowitz]

Any AC supply place has transition fittings that go from 4 to 5 " On my system I had to go on some machines from 3 to 5", 4 to 5" and 5 to 6". PMK

 

[Rob Wallace]

Lines of small holes can work.......

Greg:

Back when I was a young teenager and needed to cut larger holes in metal chassis to build various electronic equipment (mostly ham radio related stuff) and was without more sophisticated metal cutting means, I would drill a series of closely-spaced small holes (1/8" - 3/16") along the line needing to be cut (locating them slightly to the 'waste side' of the line), and connected the holes with a drill bit held at an angle and rocked back and forth, or connected them using files. After removing the unwanted metal piece(s), I then used a drill-mounted grinding stone to smooth and refine the cut line. Very low-tech, but completely effective. I suspect I am not alone in using that method (?), but trying this might be able to overcome your limitations on access to the metal you have to cut.

Good luck retrofitting your bandsaw!

Rob Wallace

 

[Greg Keddy]

Paul: your idea of adapting to 5" would definitely be the easiest / least headache for me, but from a flow restriction point of view, it's not advisable. At the pressures a typical shop DC operates, air is essentially incompressible so your flow (and ability to collect fine dust) is limited by the smallest fitting diameter in the flow path.

Rob: I like your teenage idea and I think that's the one that I will use. I don't mind low tech and labor intensive, so long as I can be reasonable sure of a favorable result.

Thanks to all for your ideas

 

[Bill Boehme]

Greg:

Back when I was a young teenager and needed to cut larger holes in metal chassis to build various electronic equipment (mostly ham radio related stuff) and was without more sophisticated metal cutting means, I would drill a series of closely-spaced small holes (1/8" - 3/16") along the line needing to be cut (locating them slightly to the 'waste side' of the line), and connected the holes with a drill bit held at an angle and rocked back and forth, or connected them using files. After removing the unwanted metal piece(s), I then used a drill-mounted grinding stone to smooth and refine the cut line. Very low-tech, but completely effective. I suspect I am not alone in using that method (?), but trying this might be able to overcome your limitations on access to the metal you have to cut.

Good luck retrofitting your bandsaw!

Rob Wallace

Hey, that was also my method until I went upcale and bought a set of Greenlee chassis punches.

Being cheap was in my genetics and I once made my own custom steel chassis from a piece of discarded galvanized sheet metal roofing. It raised the bar on what it meant to look ugly. That's when I decided that I didn't want to become a tin knocker when I grew up.

 

[Patrick Miller]

Greg:

Back when I was a young teenager and needed to cut larger holes in metal chassis to build various electronic equipment (mostly ham radio related stuff) and was without more sophisticated metal cutting means, I would drill a series of closely-spaced small holes (1/8" - 3/16") along the line needing to be cut (locating them slightly to the 'waste side' of the line), and connected the holes with a drill bit held at an angle and rocked back and forth, or connected them using files. After removing the unwanted metal piece(s), I then used a drill-mounted grinding stone to smooth and refine the cut line. Very low-tech, but completely effective. I suspect I am not alone in using that method (?), but trying this might be able to overcome your limitations on access to the metal you have to cut.

Good luck retrofitting your bandsaw!

Rob Wallace

Man does that bring back memories- don't know how many holes I made like this, mostly stereo (hi-fi back then) for me. First time I saw a hole saw in action I though there was no greater invention in the 20th century!

 

[hockenbery]

Man does that bring back memories- don't know how many holes I made like this, mostly stereo (hi-fi back then) for me. First time I saw a hole saw in action I though there was no greater invention in the 20th century!

Ditto,
Works in concrete block to make a dryer vent hole. Just be sure to miss the center solid part of the block.
Al

 

[Steve Worcester]

Paul: your idea of adapting to 5" would definitely be the easiest / least headache for me, but from a flow restriction point of view, it's not advisable. At the pressures a typical shop DC operates, air is essentially incompressible so your flow (and ability to collect fine dust) is limited by the smallest fitting diameter in the flow path.

Rob: I like your teenage idea and I think that's the one that I will use. I don't mind low tech and labor intensive, so long as I can be reasonable sure of a favorable result.

Thanks to all for your ideas

However, a 5" pipe to 4" reducer will give you more suction (because of greater volume) than a straight 4" pipe.

Compression would be if you were pushing the air instead of pulling.

Depending on the saw and it's location of the port, if you are resawing dry wood, it will work fine. The only situation you will run into where it can't keep up is cutting thick green wood, and on end grain. Then the long fibers get caught on the front side of the bottom wheel. In that situation, with 2x4" ports (that are reduced to a single 5") and 1200 CFM, my cyclone can't keep up because of the poor port location on the Laguna (24x24).

The design of the piping can have more negative effect than the reduction of that port.
That said, if it is a real big saw, say >16" resaw, I would look at enlarging the port. I also know that if my thought process is incorrect here, I will be corrected 🙂

 

[Greg Keddy]

However, a 5" pipe to 4" reducer will give you more suction (because of greater volume) than a straight 4" pipe.

Compression would be if you were pushing the air instead of pulling.

Depending on the saw and it's location of the port, if you are resawing dry wood, it will work fine. The only situation you will run into where it can't keep up is cutting thick green wood, and on end grain. Then the long fibers get caught on the front side of the bottom wheel. In that situation, with 2x4" ports (that are reduced to a single 5") and 1200 CFM, my cyclone can't keep up because of the poor port location on the Laguna (24x24).

The design of the piping can have more negative effect than the reduction of that port.
That said, if it is a real big saw, say >16" resaw, I would look at enlarging the port. I also know that if my thought process is incorrect here, I will be corrected 🙂

Steve, I can tell by that last line that you've been on Internet forums for a little while 😉
Most of what you say is correct. A 5" pipe will result in less static friction (read: suction) loss than a 4" would. The only place I disagree with you is on your definition of compression. In gas flow, compression is any time volume is reduced for the same mass flow. Now, I didn't take that definition out of a text book, but basically anytime air needs to flow through a restriction, you either reduce its volume by compressing it or you reduce the flow rate if it isn't compressible. At the conditions that a DC operates, you can't really compress the air, so what happens is that you reduce the flow rate. If the DC was strong enough to pull harder, you could eventually overcome the effect of the restriction, but my DC isn't strong enough to do that. The issues with this get into ducting design which is more than I intended to discuss here.

 

[MichaelMouse]

Now, I didn't take that definition out of a text book, but basically anytime air needs to flow through a restriction, you either reduce its volume by compressing it or you reduce the flow rate if it isn't compressible. At the conditions that a DC operates, you can't really compress the air, so what happens is that you reduce the flow rate. If the DC was strong enough to pull harder, you could eventually overcome the effect of the restriction, but my DC isn't strong enough to do that. The issues with this get into ducting design which is more than I intended to discuss here.

If you did look in a book, you'd find it under Bernoulli. http://www.wisegeek.org/what-is-the-bernoulli-effect.htm#didyouknowout

If you're running a 4" at any point in your run, stick with 4". Holesaws are MUCH cheaper than chassis punches of similar size, so use one at the bottom, where Hippy suggests, and where many already have them. If the metal is formed, use your template maker and gouges to make a crude fit block you can screw in place while you're boring through wood and then metal.

That said, most effective I've ever seen and toyed with has been a high-pressure shop vac in the "standard" location elongated with pvc through the opening, slotted so it fits around the blade. Only problem left is the buildup on top of the cut.

 

[Fred Belknap]

My BS has two 4" ports for dust collection and they are connected to a 6" main. I found out by accident that it work just as good with one as it does with two. Now I use only the upper port and it gets all the sawdust. I cut mostly bowl blanks.