Thread: Improving machine cabinet dust ports

Originally Posted by jmk89

Bob
I use an external fitting on the flexy as supplied by Carbatec https://www.carbatec.com.au/dust-con...eaded-one-side
There is no loss of internal diameter with this connector.
My set up uses 'standard' machine ports at the thicknesser and jointer not bmh - the only bmh is for the BS. So I need a fitting on the bmh that mates with the Carbatec external fitting, hence my approach.

sounds good.

Here are some pics of the jig setup and results of my 150mm BMH build. The first pic shows the jig with my first attempt. My hot air blow gun really heats the pipe up quickly, and this was all done in a few minutes, with the pipe forming the hood almost like butter. It has suffered from being too hot and has split in a few places.

The second one I took much slower, maybe 5 or more minutes. I judged the softness of the pipe by the amount of effort required to turn the tail stock wheel. I'm really happy with the second one. This is going on my Harvey table saw. Pics to follow.IMG_0510.jpgIMG_0512.jpg

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Good work! I'm really pleased to see someone else have a crack at these. They really are simple to make.

Originally Posted by arniew

Here are some pics of the jig setup and results of my 150mm BMH build. The first pic shows the jig with my first attempt. My hot air blow gun really heats the pipe up quickly, and this was all done in a few minutes, with the pipe forming the hood almost like butter. It has suffered from being too hot and has split in a few places.

The second one I took much slower, maybe 5 or more minutes. I judged the softness of the pipe by the amount of effort required to turn the tail stock wheel. I'm really happy with the second one. This is going on my Harvey table saw.

The problem with splitting is partly due to the type of PVC foam filling use in DWV pipe. The 150mm stormwater foam PVC must use a different foam and appear to be bit more robust than the DWV pipe. I have never had a stormwater BMH split.

Slower heating does help - if you can get a hold of an IR thermometer that helps to optimise the temperature forming window.

Yesterday I upgraded my Harvey tablesaw with a 150mm BMH. It was quick and easy to do it as their was virtually no mods needed on the cabinet. The old 4" port was on a plate that was approximately 225mm x 275mm. The BMH was mounted onto an MDF plate and installed in its place.

Opposite the hood is a removable cover that has a small slot for air intake. This is way too small for adequate air flow, but even opening it up allows for testing. It will be simple to build a replacement cover with larger vents, although the existing one could be modified quite easily as well.

The port and intake are across the blade rather than inline with it, but I think I can live with that.

I wonder if anyone has some ideas about the pickup on the blade guard? The existing arrangement is 2.5" and I've just hacked a hole to tap into the 150mm duct. I'm not sure it is doing much good or how to balance flow between cabinet and guard.

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Originally Posted by arniew

Yesterday I upgraded my Harvey tablesaw with a 150mm BMH. It was quick and easy to do it as their was virtually no mods needed on the cabinet. The old 4" port was on a plate that was approximately 225mm x 275mm. The BMH was mounted onto an MDF plate and installed in its place.

It will be simple to build a replacement cover with larger vents, although the existing one could be modified quite easily as well.

Just a reminder that vents with slots like that are very restrictive - a better option is hole with a large mesh covering it.
Lovetoride has made an excellent suggestion of using baking goods cooling trays, see Bell mouth hood offer - expressions of interest
The testing of mesh is something I will do today while my test duct is in place.

The port and intake are across the blade rather than inline with it, but I think I can live with that.

Its really difficult to get them in line anyway, besides it should still work

I wonder if anyone has some ideas about the pickup on the blade guard? The existing arrangement is 2.5" and I've just hacked a hole to tap into the 150mm duct. I'm not sure it is doing much good or how to balance flow between cabinet and guard.

A 2.5" hole and hose connected to a DC like you have done and through the narrow guard will only pull 50-70 CFM which won't be enough for find dust control and not that good on chip control either .

You can improve your current arrangement by inserting a 150-100 mm reducing Y junction into your 6" line and then adding a DWV Level Invert Taper 100mm x 65mm to the arm of that and connecting your 2.5" hose to that.

Longer term there are a couple of approaches that can be followed.
1) Leave the guard as is and use a large shop vac (which has its own major fine dust problems so I assume its vented or located outside) - this will pull more air though the 2.5" hose, maybe 100 CFM.
2) Rebuild the guard to accept 100 mm flexy. Connected to the 6" with a Reducing Y and you will get ~300-350 CFM though that and this will grab more fine dust.
Just be aware the bigger guard gets in the way more than the narrower design style when the fence is close to the blade.

By using 6" to the cabinet and 4" to the guard this splits the flow ~1/4 to the guard and ~3/4 to the cabinet which is OK.

Thanks for the ideas Bob. I think I will build a bigger blade guard and go with option 2. I can use the shop vac and existing guard on odd occasions as needed.


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Originally Posted by arniew

Thanks for the ideas Bob. I think I will build a bigger blade guard and go with option 2. I can use the shop vac and existing guard on odd occasions as needed.


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This is what I did for my harvey overhead. Works very well, has 4" port and is adjustable up/down and left to right.
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Originally Posted by DomAU

This is what I did for my harvey overhead. Works very well, has 4" port and is adjustable up/down and left to right.
20161010_070716.jpg

Thanks DomAU. Looks like a great solution.


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Another angle if you want to do similar

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Another angle if you want to do similar

What did you do with your Jet jointer DomAU? I've got the combo Jet jointer/thicknesser.


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Suggest not clamping the hose to the guard - just use a push fit so you can easily pull the hose off and use it as a vacuum.

Originally Posted by BobL

Suggest not clamping the hose to the guard - just use a push fit so you can easily pull the hose off and use it as a vacuum.

But there's never anything to vacuum

Originally Posted by arniew

What did you do with your Jet jointer DomAU? I've got the combo Jet jointer/thicknesser.


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I just cut off the end of the metal hood and heat moulded some 6 inch pvc to fit. It works well but doesn't completely reduce flow restriction due to the actual rectangular inlet in the machine being smaller in area. However from a functional perspective the airflow I get is more than sufficient to capture all the fine dust produced so I am not looking for more improvement. BobL made a much better but more involved modification to the entire hood if your system requires less restriction.