Thread: Making 150mm DC ports for workshop machines

Yep I get it now - thanks for posting the pics.

Here is a pic of my linisher as at yesterday. Note the piece of white timber fastened to the top.
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The next pic shows what that piece of timber is for. It has two T nuts embedded in it, to which the star knobs hold the new hood that is used when sanding round surfaces on the wheel. The upright for the new hood is a piece of 19 mm timber which has 25 mm wide 3 mm PVC sheet fastened to it's bottom edge. The PVC "shoes", along with the star knobs, holds everything securely in place it in the mitre slot.

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Here is the business end of the hood. The new hood is essentially a tunnel leading back to the primary hood and the ductwork.

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Finally, here is a video of it in use. I'm one very happy chappy.

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Pics of all hoods/ports have been put into an album here ... https://www.woodworkforums.com/member...6-john-samuel/

Nice - I'll be copying that

The attached video is enough to bring tears to the eyes of even the most battle-hardened OH&S specialist involved in dust control.

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Hi John, my first thought was What if you wanted those small bits? But then I thought, I think you said you have a VSD so you could tune the suck to leave the offcuts behind, or lift up the hood a bit, anyway good job.

On your belt sander it looks like they have done away with the belt oscillation, on mine the oscillation gadget is mounted under the front wheel and table is mounted on the motor end which is a bit useless.



Pete

Looks great john.

Originally Posted by pjt

. . . my first thought was What if you wanted those small bits? But then I thought, I think you said you have a VSD so you could tune the suck to leave the offcuts behind, or lift up the hood a bit, anyway good job.

This happens to me on my lathe, it might be easier to just add flip in/out piece of mesh

Thanks guys,

I can stop the small off cuts disappearing up the riser by moving the guard/hood to the left, so the blade is close to the right hand edge of the guard (as the operator looks at it). I move the guard to the left when ripping small pieces and to the right when using a mitre gauge When the gap between the blade and the guard is only (say) 7 mm, the small off cuts hit the edge of the guard as they are sucked up and unless they are tiny, stay there. As PJT mentioned, the guard can be lifted a little as well, so one way or another, that is not really an issue.

Most of my work is furniture, so I almost never want those small off cuts, and that sled is brilliant for one inch boards. For thicker timber, it is a simple thing to use a secondary fence (in front of the primary fence) about the same size as the workpiece. So long as the blade does not exit the secondary fence, dust collection works well.

My Taiwanese linisher is about 11 years old, and never had the oscillation feature. Same as my drum sander.

After making the new sled three things occurred to me. First, the sled worked like a charm for dust collection. Second, the cheap mitre gauge I was using sometimes got bumped and came out of square. Third, dust collection was not as good when using the mitre gauge. So ...
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Easy to use and dust collection is again excellent ... and I do get a kick out of watching the small off-cuts zip up the riser.

Hey John, you expressed some concern about the chips in front of your drop saw?

I was just wondering... there's a clearance gap underneath the table, right? How do you think it'd go if you either sealed off under the table or ran a duct through, to add a modicum of dust collection at the front?

Perhaps with a thin, bent strip of ply or similar along the front to redirect the flow vertically? (Maybe a glaziers putty or similar on the bottom, inside joint of the ply to smooth the flow?)

Given the confined space, it probably wouldn't be super-effective and may not be worth the effort... but it's something to think about.

Thanks, Skew,

Already thinking along that line. Tested the idea with cigarette ash to assess the amount of suction coming under the tool. If the ash falls very close to the edge of the tool, it is zipped off by the draught. Sadly, the airflow is severely constricted and if the ash is dropped only about 40 mm away from the edge of the tool, it just sits there.

So, the problem with that approach is inadequate airflow. No surprises.

I know that the small amount of dust I am getting is returning with the blade and being thrown forward. Because nearly all the air is drawn from the front of the tool (top is blanked off), I am getting pretty good dust extraction, especially of the very fine material (joy and happiness!). It is only the bigger stuff that can develop some momentum that is not being captured. That bigger stuff is not a threat to my health, and there is very little of it, so it is no big deal ... but it irritates me.

Currently I have an aggressive blade designed to cut wall studs and the like. A new, less aggressive blade was to be picked up today, but Carba Tech had no stock. When this is purchased and fitted, that should help. After that I'll look at the possibility of increasing airflow to the front of the tool.

Originally Posted by John Samuel

Thanks, Skew,

Already thinking along that line. Tested the idea with cigarette ash to assess the amount of suction coming under the tool. If the ash falls very close to the edge of the tool, it is zipped off by the draught. Sadly, the airflow is severely constricted and if the ash is dropped only about 40 mm away from the edge of the tool, it just sits there.

So, the problem with that approach is inadequate airflow.

Just a bit of techno talk to make things a bit more specific (or maybe not )

Normally air flow is considered as volume flow with units like CFM. This is critical for fine dust because fine dust spreads like and along with air movement.

Chips and medium size dust (as you have said can have significant momentum) don't so much need air flow (volume flow) as they need air speed ( linear flow, with units like FPM) to slow them down. Moving large chips can be done by using low volume flow and high linear flow, which is what vacuum cleaners do.

So if you want to grab the big bits the focus should be on somehow improving air speed. Of course if for a given cross section, air flow is improved - air speed will als increase, but some times it is not possible to do this so the only way left is to redirect existing flow or change the cross sectional area.

But as you already said this is not really a problem, just irritating.

Of course you have nailed it Bob.

The space under the drop saw where some air is drawn through is tiny. A smoke test shows that if the cigarette is held very close to the edge of the tool, the smoke is moving so fast it can barely be seen ... but I only need to move the source a couple of inches further away and speed drops off dramatically. So dramatically that dust and ash is not pulled under the tool.

In this case speed (beyond the edge of the tool) seems to be largely a function of volume. The further away from the edge of the tool we move, the bigger is the negative pressure bubble. As this bubble grows, speed drops off quickly, exactly as explained on Bill Pent's site.

It is an irritant, not a problem. After Skew's comments I tested it again today, with the same results. MDF and cedar leave nothing that can be seen, even after a bunch of cuts (OK, I did get one little speck of cedar). NG Rosewood left tiny traces, as did Vic Ash. The messiest thing I cut was plywood. Once again, nearly all largish chips were found on the table.

I am really happy with the improvement made so far, and am sure blanking off the top so all air is drawn through the front of the tool is a major success factor. I intend to wait for the new blade before even thinking about doing anything else.

Was never satisfied with the overhead arm on the table saw. The problem was securing it to the saw, which was difficult with a contractor saw like mine, and easy with a cabinet saw. So ...

Here is the original arm.
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And here is the saw as of today. First pic from the front.

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Second Pic shows how the arm is fixed to the cabinet.
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Third pic is from the rear.

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Final pic is a close up of the arm and shroud/guard.
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The additional storage space and using six wheels instead of four are additional bonuses ... and it is much prettier.

Very slick