Adapting a Numatic NVD750 to take 100mm

[jimmer]

I've just picked up an NVD750, for 120 euros, pretty happy with that!
but it's an older model and doesn't have the inlet for the 100mm tube, just regulat screw-on 38mm tube. this is achly fine for everything i have at the moment, but when i get a new P/T it'll presumably have a bigger outlet. so ideally i'd buy just the part that does the 100mm, cut a hole in the drum and rivet it on. guess i could try emailing axmisnter to ask it they can get it.

otherwise i could probably make something out of soil pipe and plywood.

anyone been in this situation or done something similar?

 

[Sideways]

Just an opinion but even with two motors I don't think these make the airflow to justify a 100mm inlet. Make it 2 inch or 63 mm to match the common smaller pipe sizes.
I set one of these up with a 2 inch hose to the upper port on an axy bandsaw and it works well . The saw has the top corner of the lower box closed off with an almost zero clearance insert and this concentrates the suction where the dust enters. The dust ports on the saw are 100mm but simple reducers let it all work well with 50mm ID hose.

The lower port I just ignored and with good extraction at the top of that box, only a mugfull of dust accumulated in the bottom of the machine in the time it took to fill the NVD750 to the gunwales ...

 

[jimmer]

good advice thanks.
seems plenty powerful to go a bit bigger like you say, but yep perhhpas better results with 50mm waste pipe for example

 

[WellsWood]

I've got the wall mounted version of that extractor which has a 100mm inlet. I have about 5-6m of ducting between it and my 12" P/T and it copes admirably. Your bugbear used for P/T will be capacity - I have a dustbin dropbox with a lashed up cyclone lid next to the P/T which catches almost everything more or less at source. It's quite satisfactory except when planing wide boards (particularly softwood) when it can occasionally clog up - to be fair this is usually the result of not cleaning the filters or emptying the dropbox often enough, which reduces efficiency rapidly.
I would contact Numatic directly and see if you can get the moulded plastic 100mm port as a spare, then as you say just make the cutout and bolt it on.

 

[jimmer]

good stuff, thanks mark

 

[John15]

Don't you need a Low Pressure High Volume extractor for a planer thicknesser?

John

 

[Keith 66]

At the school where i work we have NVD 750-2's as extractors for everything, even the twin motor ones struggle to cope with any sizeable machine.
We have had ongoing arguments with our "service provider" who insists everything is fine when in reality the extractors are woefully underspecified & there are serious dust issues.
A Planer or wood lathe for instance needs a low vacumn high volume type of extractor not a high vac low vol one like the nvd750's. Duct size is critical, we have standard vacumn cleaner hoses on most of ours & the lev engineers quote the size on the outside dia of the corrugated pipe not the bore! A 35mm hose does not work on a circular saw!
At home i have a nvd 750-2 with 100mm duct & used to use it for extraction when grinding grp, it was pretty good.

 

[Sideways]

I'm in the process of replacing a run of central heating pipes blocked with iron oxide deposits. The root cause was inadequate dosing with Fernox, but the transferrable lesson is that the deposits accumulated in a couple of branches of piping where the radiators were only run at tickover with a low flow rate.
.... too low an air velocity in too big a pipe and the air speed won't be able to keep the pipe swept. You'll get dust and chips depositing just like i got oxide depositing in the CH pipes that didn't have enough flow through them

• 
  The internet tells me you need 4000 feet / minute to move heavy sawdust (74 kilometeres an hour).
  Multiply it by the cross sectional area of your hose (in metres) so for a 125mm (5 inch) hose I need an extractor that can move 908 cubic metres / hour or 15 cu metres / min.
  A 100mm hose needs 64% of that so 580 cmh / 10 cmm
  The NVD750 has a max air volume of 5,000 litres / min = 5 cmm so about half what that internet source thinks is advisable for a 100mm hose.

 

[meathead]

I have nvd750, it collects more dust on the outside of it , than whats inside DOH
I just hide my beers from my mrs in it, she works for social services, under child protection
and she's what i would call a booze nazi, but I love woodworking especially when my extractor is full
couldn't make it up
and what's up with them rubber adaptors!