Thread: 100mm Hole in Bandsaw Door

Originally Posted by markharrison

Have you thought about a box shroud around the trunions and the lower blade guide assembly and bypassing the existing upper duct? Collecting the dust before it enters the lower cabinet works better for me.

I think this is the way I will go but it is pretty obvious the other duct could benefit from some extra venting in the door way. I can understand manufacturers not wishing to put a box shroud around the trunions and the lower blade guide assembly because that would interfere with the table tilt. However, I cannot remember the last time if ever I have used the tilt on this BS.

My thoughts are if you are trying to help your customers improve dust collection, the method that is easiest to reproduce would be the most desirable.

This example in the attached photo is not mine. Mine is far more primitive!

It comes from the Sauer and Steiner blog here. No surgery involved.

As I said, this is reversible if it doesn't work to your satisfaction.

Think about it a bit more Mark. If you added a vent to the cabinet and the air drawn through it also drew air from a box like that or a simpler dust pick up you get two for one. You vent the cabinet, pick up the under table dust using the same vent and it all goes through the cabinet into the DE. Sounds good to me, I like simple.

Unfortunately putting a vent in the door is not going to help remove dust from the vicinity of the conventional under table port because very little air seems to travel through that port, even with the door open. Maybe it's better on other saws but the pathways to that port are just too constrictive on my setup.

If a vent is placed in the door air will also preferentially travel through pathway 2 and less will travel through pathway 1 which is what is really required.



As Mark (and others have said) a better place seems to be just to locate a naked hose at position 4

Originally Posted by BobL

Unfortunately putting a vent in the door is not going to help remove dust from the vicinity of the conventional under table port because very little air travels through that port even with the door open.

If a vent is placed in the door air will also preferentially travel through pathway 2 and less will travel through pathway 1 which is what is really required.



As Mark (and others have said) a better place seems to be just to locate a naked hose at position 4

That is not what I meant at all. Put the vent in the door and lead an adapter, dust pick up call it what you will from the door vent up to under the table to where the dust is shown in your photo. The air is drawn from under the table as it is now a dust pick extraction point, through the cabinet into the DE exhaust.

Originally Posted by Mini

That is not what I meant at all. Put the vent in the door and lead an adapter, dust pick up call it what you will from the door vent up to under the table to where the dust is shown in your photo. The air is drawn from under the table as it is now a dust pick extraction point, through the cabinet into the DE exhaust.

Maybe your port is differently designed but I just established that cabinet port A is a dog that only conducts about 300 cfm even if the door is completely left open.


For BSs with both ports A and B, port A is best completely closed since A and B will just fight each other for similar air.

For BSs without a port B, installing one into the cabinet is probably the first thing to do. Putting a grill in the door so this port can breathe more easily seems like it will help.

For all BSs, the most useful ducting is probably placed directly to the underside of the table without any box around it so it can draw enough air. Routing this ducting through the lower cabinet is only going to reduce the total air flow from that area.

I will perform some testing of my grill material to see how much it slows the air flow down.

If you only get 300 CFM with the door open, that's the maximum you could get with an additional air inlet.

The other box shroud I am intending to build for my saw will be open at the opposite end to the DC collection point. I'm not sure if Conrad Sauer's is. It's hard to be sure from that photo but I expect it probably is. He reports that while it isn't ideal that you have to do this in the first place, it does work.

Anyway, it's your saw and you should feel free to do as you please.

Originally Posted by markharrison

If you only get 300 CFM with the door open, that's the maximum you could get with an additional air inlet.

Yep I agree with that (see my previous posts), but the flow through the port in the bottom part of the cabinet increases from 300 to 600 cfm by opening the door open so a grill in the door still makes sense for that port.

The other box shroud I am intending to build for my saw will be open at the opposite end to the DC collection point. I'm not sure if Conrad Sauer's is. It's hard to be sure from that photo but I expect it probably is. He reports that while it isn't ideal that you have to do this in the first place, it does work.

Thats a good idea - I'll see if I can do a similar thing and measure the air flow.

Originally Posted by BobL

Maybe your port is differently designed but I just established that cabinet port A is a dog that only conducts about 300 cfm even if the door is completely left open.

Yes, my port is a different design so your contention has no relevance. Actually what counts in the real world is whether it works or not.

Originally Posted by BobL

Yep I agree with that (see my previous posts), but the flow through the port in the bottom part of the cabinet increases from 300 to 600 cfm by opening the door open so a grill in the door still makes sense for that port.

The airflow figures sound a little strange. One thing that might happen by adding a hole in the door to get the 600cfm into B is that the flow into A will drop even further. What about adding a plate/box to the door so more air can get into port A? Something not completely unlike this.

Stuart

p.s. sorrry for the rubbish drawing but I dont even know what the door looks like

Originally Posted by Stustoys

The airflow figures sound a little strange. One thing that might happen by adding a hole in the door to get the 600cfm into B is that the flow into A will drop even further.

You must be looking at the figures the wrong way. Opening the door increases A from 244 to 280 cfm so adding holes in the door should still increase the flow at A.

What about adding a plate/box to the door so more air can get into port A? Something not completely unlike this.

Port A can is so poorly designed to begin with that it only pull 280 cfm with the cabinet door wide open so adding plates or holes is a waste of time . I'm going to try disconnecting port A and used that flexy directly underneath the table.

Originally Posted by BobL

Opening the door increases A from 244 to 280 cfm so adding holes in the door should still increase the flow at A.

Yes but by adding a hole mostly over port A only you may increase the flow in port A to more than 280. Adding it were its going to go into port B may decrease flow in port A to less than 244.

Originally Posted by BobL

Port A can is so poorly designed to begin with that it only pull 280 cfm with the cabinet door wide open so adding plates or holes is a waste of time . I'm going to try disconnecting port A and used that flexy directly underneath the table.

Whats the flow in port A with port B blocked?(granted, depending on how your system is set up it may not make much difference)

Stuart

Originally Posted by Stustoys

Yes but by adding a hole mostly over port A only you may increase the flow in port A to more than 280. Adding it were its going to go into port B may decrease flow in port A to less than 244.

Short of drilling large holes or cutting metal away in the cabinet (not the door) to open up access for air to the area around port A there is no greater access of air to port A than leaving the door open. There is no way deflectors or cutting holes in just the door etc will increase the flow above 280 cfm

Whats the flow in port A with port B blocked?(granted, depending on how your system is set up it may not make much difference)

Its the same, the limit is port A (and to a lesser extent the fact that flexy is being used)

Anyway this doesn't solve Mini's problem because he has a differently designed port A.

However the following info is likely to be useful all concerned.
It's around 40º in the shed right now but I managed to get into the shed and do some quick measurements.

In these pics you can see the grill material I'm planning to use in the door way to improve the flow for port B.

The grill is held in turn in front of a 150 and 100 mm intakes connected to 100 mm flexy and the air flow measured with and without the grill. The grill itself is 200 x 175 mm and is 58% transparent.


Placing the grill in front of the 100 mm intake like above reduces the airflow by 27%


Placing the grill in front of the 150 mm intake like above reduces the airflow by only 7%.

My plan is to use the full 200 x 175 grill in the bottom door of the cabinet to improve the flow in port B. The question now is where in the door is the best place to put the grill ?

Bob, no way would I use a grill like that. I would build a stand off guard that covered the opening and had at least the intake area of the hole but more would not hurt. A stand off guard drawing through four sides would not have a huge gap between it and the cabinet and given a large overlap on the hole would be effective as a finger guard. I will dig the aenometer out and do some tests when I get it all going but I don't think I have a flow problem as the port draws entirely differently from Bob's BS.