HF Dust Collector - 4" or 5" Flex Pipe

[Martin Hutton]

I have the HF dust collector motor setup with the 5" Super Dust Deputy pre-separator and a Wynn MERV15 on the back-end. Standard impeller for now.

I am looking at buying a number of Magport attachments as I roll around my homemade cart from tool to tool. Is there any appreciable benefit for going up to a single 10' length of 5" flex pipe over 4" just running the HF motor (tapering back down to 4" at each tool)?

[Bobby Robbinett]

I believe you would get better performance from a 5” pipe rather than a 4”. Especially if you might change the stock impeller later on. Make sure if you use flex hose to get the kind that is smooth in the inside and not ribbed.

[David L Morse]

The performance difference will depend on your setup. It sounds like you've made some major mods to the stock unit so that will increase the difference between the two sizes. In any case it's not a huge change.

The only real downside to the 5" is the extra $9 per fitting. So it comes down to your definition of "appreciable benefit". It's not going to be more than about 15% flow improvement, more than likely less than that. Again, how much less depends on your setup. Can you post a pic?

[Martin Hutton]

The performance difference will depend on your setup. It sounds like you've made some major mods to the stock unit so that will increase the difference between the two sizes. In any case it's not a huge change.

The only real downside to the 5" is the extra $9 per fitting. So it comes down to your definition of "appreciable benefit". It's not going to be more than about 15% flow improvement, more than likely less than that. Again, how much less depends on your setup. Can you post a pic?

I may just pipe in the outflow from the motor right into the filter from above with a small bag or catch pan hanging off the bottom of the filter. However, I just went with the standard HF setup for now since it was easier.


PXL_20210805_015530809.jpg

[Jim Becker]

The 5" SDD will support a 5" hose, so I'd use the 5" hose if you can. But if it makes adapting to machines easier, you can use a 5"-4" metal reducer at the machine end and do your magnetic connections at 4" to match the machine. If you have any Euro type machines with 120mm ports, the 5" hose will be the better choice, too.

[David L Morse]

I may just pipe in the outflow from the motor right into the filter from above with a small bag or catch pan hanging off the bottom of the filter.

That will make a big difference. Fabricating a 6" outlet adapter and using a 6" hose to the filter will also make a big difference. Increasing the fan inlet to 6" will make some difference by eliminating a contraction, but not as much as opening up the outlet.

Here are some fan curves I measured a couple of years ago that show the performance of various stripped down versions of the HFDC:

Many Configs.jpgPanorama3A.jpg

This was done with the 12" impeller mod as well as a 6" inlet but the relative performance will be similar.

[Martin Hutton]

The 5" SDD will support a 5" hose, so I'd use the 5" hose if you can. But if it makes adapting to machines easier, you can use a 5"-4" metal reducer at the machine end and do your magnetic connections at 4" to match the machine. If you have any Euro type machines with 120mm ports, the 5" hose will be the better choice, too.

I can't believe I didn't think of this haha. Good call on just using 4" ports and putting the reducer on the 5" flex hose. Saved me some money and will allow for more flexibility if I ever want to go straight 4" for any reason.

[Jim Becker]

There are some battles that are worth more to fight than others. Changing the ports on some tools is not an easy task, so you do what you need to do. I will say, however, it amazes me that tool manufacturers still embrace 4" posts on major dust/chip producers that would be better served by a 120mm or 5" port and this is despite a whole lot of attention paid in recent decades to making dust collection more efficient. They seem stuck on the status quo.

[Bobby Robbinett]

That will make a big difference. Fabricating a 6" outlet adapter and using a 6" hose to the filter will also make a big difference. Increasing the fan inlet to 6" will make some difference by eliminating a contraction, but not as much as opening up the outlet.

Here are some fan curves I measured a couple of years ago that show the performance of various stripped down versions of the HFDC:

Many Configs.jpgPanorama3A.jpg

This was done with the 12" impeller mod as well as a 6" inlet but the relative performance will be similar.

Will the stock Harbor Freight dust collector support a 6” intake? I know that just talking a 10ft x 6” hose it might support. But what about a 6” trunk line?

[David L Morse]

Will the stock Harbor Freight dust collector support a 6” intake? I know that just talking a 10ft x 6” hose it might support. But what about a 6” trunk line?

Depends on what you mean by "support", that's kind of a vague term in this context. A six inch trunk will allow more CFM than a five inch trunk regardless of the DC it's connected to. It will also have lower velocity inside it but the need for high velocity in a hobbyist system is often way exaggerated, especially for horizontal runs. Note that higher CFM means higher velocity at the tool inlet where it really counts. That is, the larger pipe results in higher velocity to pull in dust from where it's made even though velocity drops in the trunk.

Note that five inch snaplock isn't available in Australia so six inch PVC is the preferred duct in their home shops. The 50 Hz power there makes all of their "2HP" DCs perform like the HF. So, yes, on that side of the equator a HF equivalent will support a six inch trunk. Check out the "Dust Extraction" forum at woodworkforums(dot)com. It's in the "Hand Tools & Machinery" section.