Dust Collection: Vacuum Fittings

The Micro-Mark bandsaw’s vacuum port forced me to finish up a long-stalled project: adding a bit of plumbing to simplify connecting the small shop vacuum I use for dust collection.

It turns out that a 45° 3/4 inch Schedule 40 PVC elbow fits snugly into the bandsaw’s rubbery vacuum port and angles the hose in the right general direction:

Vacuum Adapters - 3-4 PVC to vac nozzle
Vacuum Adapters – 3-4 PVC to vac nozzle

The elbow OD fits into an adapter with a tapered socket for the vacuum cleaner’s snout:

Vacuum Hose Fittings - 3-4 PVC fitting to vac nozzle
Vacuum Hose Fittings – 3-4 PVC fitting to vac nozzle

That solid model doesn’t resemble the picture, because that gracefully thin tapered cylinder around the snout will definitely test PETG’s strength under normal shop usage; fat is where it’s at when it breaks. The interior has a tapered section between the elbow’s OD (at the bottom) and the nozzle taper (at the top) to eliminate the need for a tedious support structure.

The elbow’s OD pretty much matches the nozzle’s ID and leaves the air flow unrestricted. The aperture in the bandsaw frame might be half the pipe’s area, so I’m surely being too fussy.

With that in hand, I built more adapters to mate 1 inch PVC fittings with the two vacuum ports on the belt / disk sander to keep the canister out of my way and make the dust just vanish. A tee plugged into the belt sander side accepts the vacuum nozzle (bottom) and inhales dust from the disk sander (top):

Vacuum Adapters - belt sander - tee
Vacuum Adapters – belt sander – tee

A U made from two 90° elbows aims the disk sander dust into the hose going across the back side of the belt:

Vacuum Adapters - disk sander - double elbow
Vacuum Adapters – disk sander – double elbow

Those elbows have a 40 mm length of 1 inch PVC pipe between them; no need to print that!

The hose has a left-hand thread rib which, of course, required throwing the first adapter away into the Show-n-Tell box:

Vacuum Hose Fittings - hose to 1 inch PVC fitting
Vacuum Hose Fittings – hose to 1 inch PVC fitting

That’s a descendant of the broom handle thread, turned inside-out and backwards.

Building two hose adapters with the proper chirality worked fine:

Vacuum Hose Fittings - hose to 1 inch PVC fitting - Slic3r pair
Vacuum Hose Fittings – hose to 1 inch PVC fitting – Slic3r pair

Although you could lathe-turn adapters that plug PVC fittings into the sander’s vacuum ports starting with a chunk of 1 inch PVC pipe, it’s easier to just print the damn things and get the taper right without any hassle:

Vacuum Adapters - vac port to 1 PVC
Vacuum Adapters – vac port to 1 PVC

The straight bore matches the ID of 1 inch PVC pipe for EZ air flow:

Vacuum Hose Fittings - vac port to 1 inch PVC pipe
Vacuum Hose Fittings – vac port to 1 inch PVC pipe

The sleeve barely visible on the bottom leg of the tee looks like 1 inch PVC pipe on the outside and a vacuum port on the inside:

Vacuum Hose Fittings - 1 inch PVC to vac nozzle
Vacuum Hose Fittings – 1 inch PVC to vac nozzle

The source code includes a few other doodads that I built, tried out while deciding how to make all this work, and eventually didn’t need.

All the dimensions are completely ad-hoc and probably won’t work with PVC fittings from your local big-box retailer, as the fitting ODs aren’t controlled like the IDs that must fit the pipe. I cleaned things up a bit by putting the ID, OD, and length of the pipe / fittings / adapters into arrays, but each module gets its own copy because, for example, 1 inch 45° elbows have different ODs than 1 inch 90° elbows and you might want one special fitting for that. Ptui!

The OpenSCAD source code for all those adapters as a GitHub Gist:

// Vacuum Hose Fittings
// Ed Nisley KE4ZNU July 2016
Layout = "FVacFitting"; // PVCtoHose ExpandRing PipeToPort FVacPipe FVacFitting
//- Extrusion parameters must match reality!
// Print with 2 shells and 3 solid layers
ThreadThick = 0.25;
ThreadWidth = 0.40;
HoleWindage = 0.2;
Protrusion = 0.1; // make holes end cleanly
//----------------------
// Dimensions
ID = 0;
OD = 1;
LENGTH = 2;
Pipe = [34.0,(41.0 + HoleWindage),16.0]; // 1 inch PVC pipe fitting
VacPortSander = [30.0,31.3,25]; // vacuum port on belt sander (taper ID to OD over length)
VacNozzle = [30.1,31.8,30.0]; // nozzle on vacuum hose (taper ID to OD over length)
MINOR = 0;
MAJOR = 1;
PITCH = 2;
FORM_OD = 3;
HoseThread = [32.0,(37.0 + HoleWindage),4.25,(1.8 + 0.20)]; // vacuum tube thread info
NumSegments = 64; // .. number of cylinder approximations per turn
$fn = NumSegments;
ThreadLength = 4 * HoseThread[PITCH];
ScrewOAL = ThreadLength + HoseThread[PITCH];
WallThick = 2.5;
echo(str("Pitch dia: ",HoseThread[MAJOR]));
echo(str("Root dia: ",HoseThread[MAJOR] - HoseThread[FORM_OD]));
echo(str("Crest dia: ",HoseThread[MAJOR] + HoseThread[FORM_OD]));
//----------------------
// Wrap cylindrical thread segments around larger plug cylinder
module CylinderThread(Pitch,Length,PitchDia,ThreadOD,PerTurn,Chirality = "Right") {
CylFudge = 1.02; // force overlap
ThreadSides = 6;
RotIncr = 1/PerTurn;
PitchRad = PitchDia/2;
Turns = Length/Pitch;
NumCyls = Turns*PerTurn;
ZStep = Pitch / PerTurn;
HelixAngle = ((Chirality == "Left") ? -1 : 1) * atan(Pitch/(PI*PitchDia));
CylLength = CylFudge * (PI*(PitchDia + ThreadOD) / PerTurn) / cos(HelixAngle);
for (i = [0:NumCyls-1]) {
Angle = ((Chirality == "Left") ? -1 : 1) * 360*i/PerTurn;
translate([PitchRad*cos(Angle),PitchRad*sin(Angle),i*ZStep])
rotate([90+HelixAngle,0,Angle]) rotate(180/ThreadSides)
cylinder(r1=ThreadOD/2,
r2=ThreadOD/(2*CylFudge),
h=CylLength,
center=true,$fn=ThreadSides);
}
}
//-- PVC fitting to vacuum hose
module PVCtoHose() {
Fitting = [34.0,41.0,16.0]; // 1 inch PVC elbow
Adapter = [HoseThread[MAJOR],(Fitting[OD] + 2*WallThick + HoleWindage),(ScrewOAL + Fitting[LENGTH])]; // dimensions for entire fitting
union() {
difference() {
cylinder(d=Adapter[OD],h=Adapter[LENGTH]); // overall fitting
translate([0,0,-Protrusion]) // remove thread pitch dia
cylinder(d=HoseThread[MAJOR],h=(ScrewOAL + 2*Protrusion));
translate([0,0,(ScrewOAL - Protrusion)]) // remove PVC fitting dia
cylinder(d=(Fitting[OD] + HoleWindage),h=(Fitting[LENGTH] + 2*Protrusion));
}
translate([0,0,HoseThread[PITCH]/2]) // add the thread form
CylinderThread(HoseThread[PITCH],ThreadLength,HoseThread[MAJOR],HoseThread[FORM_OD],NumSegments,"Left");
}
}
//-- Expander ring from small OD to large ID PVC fittings
// So a small elbow on the bandsaw fits into the hose adapter, which may not be long-term useful
module ExpandRing() {
Fitting_L = [34.0,41.0,16.0]; // 1 inch PVC pipe elbow
Fitting_S = [26.8,32.8,17]; // 3/4 inch PVC elbow
difference() {
cylinder(d1=Fitting_L[OD],d2=(Fitting_L[OD] - HoleWindage),h=Fitting_L[LENGTH]); // overall fitting
translate([0,0,-Protrusion])
cylinder(d=(Fitting_S[OD] + HoleWindage),h=(Fitting_L[LENGTH] + 2*Protrusion));
}
}
//-- 1 inch PVC pipe into vacuum port
// Stick this in the port, then plug a fitting onto the pipe section
module PipeToPort() {
Pipe = [26.5,33.5,20.0]; // 1 inch Schedule 40 PVC pipe
difference() {
union() {
cylinder(d=Pipe[OD],h=(Pipe[LENGTH] + Protrusion));
translate([0,0,(Pipe[LENGTH] - Protrusion)])
cylinder(d1=VacNozzle[OD],d2=VacNozzle[ID],h=VacNozzle[LENGTH]);
}
translate([0,0,-Protrusion])
cylinder(d=Pipe[ID],h=(Pipe[LENGTH] + VacNozzle[LENGTH] + 2*Protrusion));
}
}
//-- Female Vac outlet inside PVC pipe
// Plug this into PVC fitting, then plug hose + nozzle into outlet
module FVacPipe() {
Pipe = [26.5,33.5,20.0]; // 1 inch Schedule 40 PVC pipe
difference() {
cylinder(d=Pipe[OD],h=VacPortSander[LENGTH]);
translate([0,0,-Protrusion])
cylinder(d1=VacPortSander[ID],d2=VacPortSander[OD],h=(VacPortSander[LENGTH] + 2*Protrusion));
}
}
//-- Female Vac outlet on 3/4 inch fitting OD
// Jam this onto OD of fitting, plug hose + nozzle into outlet
module FVacFitting() {
Adapter = [26.5,(33.5 + 2*WallThick),17.0]; // overall adapter
VacPortSander = [30.0,31.3,25]; // vacuum port on belt sander (taper ID to OD over length)
Fitting = [26.8,32.8,17]; // 3/4 inch PVC elbow
TaperLength = 5.0; // inner taper to avoid overhang
difference() {
cylinder(d=Adapter[OD],h=Adapter[LENGTH]); // overall fitting
translate([0,0,-Protrusion])
cylinder(d=(Fitting[OD] + HoleWindage),h=(Adapter[LENGTH] + 2*Protrusion));
}
translate([0,0,Adapter[LENGTH]])
difference() {
cylinder(d=Adapter[OD],h=TaperLength);
translate([0,0,-Protrusion])
cylinder(d1=(Fitting[OD] + HoleWindage),d2=VacPortSander[ID],h=(TaperLength + 2*Protrusion));
}
translate([0,0,(TaperLength + Adapter[LENGTH])]) // vac fitting
difference() {
cylinder(d=Adapter[OD],h=VacPortSander[LENGTH]);
translate([0,0,-Protrusion])
cylinder(d1=VacPortSander[ID],d2=VacPortSander[OD],h=(VacPortSander[LENGTH] + 2*Protrusion));
}
}
//----------
// Build things
if (Layout == "PVCtoHose")
PVCtoHose();
if (Layout == "ExpandRing") {
ExpandRing();
}
if (Layout == "PipeToPort") {
PipeToPort();
}
if (Layout == "FVacPipe") {
FVacPipe();
}
if (Layout == "FVacFitting") {
FVacFitting();
}

Sketches of dimensions and ideas, not all of which worked out:

Vacuum Fitting Doodles - hose thread - 3-4 pipe - nozzle
Vacuum Fitting Doodles – hose thread – 3-4 pipe – nozzle
Vacuum Fitting Doodles - hose thread forms - 3-4 elbow
Vacuum Fitting Doodles – hose thread forms – 3-4 elbow
Vacuum Fitting Doodles - port - male port - 45 deg 3-4 elbow
Vacuum Fitting Doodles – port – male port – 45 deg 3-4 elbow