Shopsmith Forums

beeg wrote:Just remember that the build up helps the filtering process.




I get a buildup in about that area. The dust settles there and builds up.

Comments about removing that caking dust always confuses me. I read, frequently, that the caked dust improves the filtering capability. If that be the case, why remove it unless it is so thick that it obstructs the air flow all together?

Any time I change the dust collector bag it seems like a lot of the caking breaks off - usually right after I remove the bag.

I, too, have read that the collected dust helps with filtration but cannot imagine how that can be.

If a dust particle closes off a 'hole' in the filter that means the next dust particle has to find another 'hole' to plug. The previously filled 'hole' is not allowing airflow to bring the new particle to it. Repeat this millions (billions?) of time and you are just clogging the filter which reduces airflow and, I think, the efficiency.

If 'clogging' a filter is help in filtering, why do we replace the 'clogged' filters?

Help!

Forrest

dusty wrote:When does the 1 micron capability of the 42" filter really become a valuable characteristic for the DC3300.

Undoubtedly, if you work in a small enclosed shop or in a basement shop, filtering of that fine dust is good if not necessary.

I have often debated getting the larger filter but have not done so. I have the 24" filter (5 micron) and I work in a shop that is open to the great out of doors via a double garage door. I have rationalized that I don't really need the larger filter (1 micron) because of that.

Is my thinking flawed?

It depends on which DC experts you talk to. Most will go on and on about OSHA standards, air flow ratings and MERV filtration standards. There is nothing wrong with that per se' but do keep in find that OSHA standards are concerned with long term exposure in an "Occupational" setting meaning a typical work exposure to the hazard(s) is at least 35 hrs per week. I just don't have the time for 35 hrs of shop time per week. I too work in an open environment. I currently have no breathing issues such as asthma and no known allergies. My biggest issue with DC is not letting it get tracked into the house or settle on cars once parked back in the garage. I use a shop vac and some fans to blow the fines out and keep the air moving. To further avoid dust issues I make sure that severe dust operations like power sanding are performed as close to the large opening of the shop as possible. I'm also changing my work habits and reducing power tool usage. This is a hobby for me it is supposed to be an enjoyable time sink so I don't care if projects take longer using hand tools than they wood using power tools.

Just my 2 cents on the issue. Do what you are comfortable with.

As usual there be trade offs here.

The three DC 3300 filters are made from felt. IIRC the larger ones are less 'porous' and thus provide finer and finer particle capture as the size increases. That allows for more or less the same cfm.

As for the 'improved' filtering obtained by allowing caking, I can only surmise that the cake is still porous and provides greater surface area for capturing finer new particles. That has to be at a reduced cfm. That reduction will be less with the larger filters.(as will the amount of caking[thickness])

So the larger filters can be 'finer' and still maintain the cfm.



In other words, caking will provide smaller particle filtration, but at the expense of cfm. The larger the filter, the less this reduction will be and the time between 'time to decake' will be greater.


Lotta conjecture, but that is the way I see it.

beeg wrote:Just remember that the build up helps the filtering process.

I get a buildup in about that area. The dust settles there and builds up.

My guess is; Your hood is oriented so the zipper is located on the left side of the DC. This places the zipper above the fan discharge flange. This outlet is very close to the side of the DC, and a likely area for dust to catch and build up.

I rotated the hood so the zipper is at the back.

I absolutely agree with Forrest that cake is more of a restriction than a filter. A cake isn't needed or desirable in a larger hood.

[quote="charlese"]My guess is]

VERY GOOD Chuck. that's EXACTLY where it is right near the on/off switch. When I get home this weekend I'll be rotating the filter. THANKS AGAIN for the tip.

Not to mention the electrical charge of the dust particle and the "magnetic" attraction of it, since the majority of dust particles have a positive charge.

rbursek wrote:Not to mention the electrical charge of the dust particle and the "magnetic" attraction of it, since the majority of dust particles have a positive charge.

'Positive' relative to what?