Bench Suction

[David_D_Arens2]

Hi Gang,

I looked at some of the new shop vacs that were displayed in
Home Depot & Payless Cashways. The vacuum inlet on most of these
goes in the side (90 deg to the top) of the top cover. The
instructions I listed recently for converting one of these for
use as a water bath vac won’t work. The following instructions
will.

Many of the newer, larger shop vacs (10 gallon & up capacity)
have the vacuum inlet on the side of the top cover. The cover has
a molded deflector on the inside of the inlet. This deflector
must be removed in order to modify the vac for use as a water
bath vac. This modification will reduced the effectiveness of the
vac for ordinary vacuuming if it is used for both applications.
I saw one vac that had the side inlet, but no deflector. It was
mfgd. by Ridgid, model WD1200, priced at $69.95 at Home Depot. It
is a 4.25hp, with a 12 gallon capacity & comes with a full set of
tools.

All the vacs I saw had a 2 1/4 inch inside diameter inlet hole.
It will be necessary to obtain some plastic plumbing fittings &
pipe to complete the installation. A 1 1/2 in PVC 90 deg elbow
has an outside diameter of 2 1/4 inches. This can be cemented in
the inlet with standard plastic plumbing cement. A 24 in long
piece of 1 1/2 in PVC pipe is also required.

Here’s the instructions for those vacs that have the inlet port
on the side of the top cover and a deflector as part of the
inside portion of the inlet port.

Dave

Section I

1. Remove the top cover.

2. Empty the contents of the tub into the trash & clean out
   the tub as required.

3. Cut the inlet deflector from the inside of the top. A
   sharp knife may be repeatedly drawn along the intersection
   of the deflector with the top cover until the deflector can
   be removed. A hack saw blade, with one end taped for a
   handle, could also be used to saw the deflector off. Follow
   the contour of the cover when removing the deflector.

4. Remove any burrs & rough edges with a suitable file or
   sandpaper.

5. Insert the 1 1/2 in elbow into the inlet hole from the
   inside to check for fit. It may be a little loose. If the gap
   is less than an 18 ga wire, the plastic cement will fill the
   gap. Mark this end.

6. If the gap is more than an 18 ga wire, a few wraps of
   black electrical tape can be placed on the elbow. Wrap the
   tape as far back as possible & only 1 tape width wide.

7. Remove any burrs or rough edges from one end of the 1 1/2
   in PVC pipe. Mark this end.

8. Insert the marked end in the untaped side of the elbow.

9. Insert the elbow in the inlet hole. Be sure the pipe is
   pointing straight down (perpendicular to the vacuum top). If
   the bottom of the tub slopes in too far to allow the pipe to
   remain perpendicular to the top cover proceed with the
   instructions in Section II.

10. Carefully set the top on the vacuum. It won’t be able
    reach it’s normal resting place because the pipe is too long.

11. Measure the distance from the top of the tub to the
    bottom of the top right at the inlet hole.

12. Remove the top cover.

13. Remove the pipe & elbow from the inlet hole.

14. Remove the pipe from the elbow.

15. Add 1 1/2 inches to the measurement from step 11.
    Transfer this measurement to the unmarked end of the pipe.

16. Cut the pipe at the mark & remove all burrs & sharp
    edges.

17. Clean the end of the pipe that fits into the elbow of
    all dirt, oil & grease. Note: A cloth with acetone or alcohol
    works well for this activity.

18. Clean the outside of the taped end & inside of other
    elbow end of all dirt, oil & grease.

19. Clean the inside of the vacuum inlet hole of all dirt,
    oil & grease.

20. Apply a liberal coating of PVC cement to the inside of
    the untape end of the elbow. The cement should cover the
    entire inside, from the ridge to the end.

21. Apply a liberal coating of PVC cement to the marked end
    of the pipe. The coating should cover the entire surface of
    the pipe for about 1 in back from the end.

22. Insert the glued end of the pipe into the glued end of
    the elbow with a twisting motion. Hold the two together 10-15
    seconds after the pipe is seated.

23. Apply a liberal coating of PVC cement to the inside of
    the vacuum inlet. Try not to get any on the potion of the
    inlet the vacuum hose connects to. Any excess can be wiped
    off with a paper towel.

24. Apply a liberal coating of PVC cement to the outside of
    the taped end of the elbow.

25. Insert the elbow into the vacuum inlet. Be sure to
    position the pipe so it’s hanging down, perpendicular to the
    top. Hold the elbow & top in position for 10-15 seconds after
    the pipe is in the correct position. Place the top on the tub
    to allow the cement to dry. Be careful not to move the pipe
    while replacing the top.

26. Follow the directions on the cement container to
    determine drying time.

27. If any gaps appear after the cement dries, they can be
    filled with silicone bathtub caulk. Let the caulk cure before
    apply any vacuum.

Section II

If the sides of the tub slope in at the bottom too far to
allow the pipe to extend straight down from the elbow, an
extension may have to be added to the part of the elbow that
goes into the vacuum inlet.

This can be accomplished as follows:

1. Obtain a 1 1/2 in PVC coupling, mark 1 end.

2. Cut a piece of 1 1/2 PVC pipe 2 inches long. Remove any
   burrs & sharp edges.

3. Measure & record the length of the vacuum inlet (inside
   to outside).

4. Clean any dirt, oil or grease from the inside of the
   marked end of the coupling & long pipe, the elbow & the 2 in
   long piece of pipe. Note: A cloth with acetone or alcohol
   works well for this activity.

5. Apply a liberal coat of PVC cement to the inside of the
   marked end of the coupling.

6. Apply a liberal coat of PVC cement to the inside of the
   elbow.

7. Apply a liberal coat of PVC cement to both ends of the 2
   in long pipe.

8. Insert the 2 in long pipe into the glued end of the
   coupling with a twisting motion.

9. Insert the pipe with coupling attached, into the elbow
   with a twisting motion. Hold the assembly in position for
   10-15 seconds.

10. Apply a liberal coat of PVC cement to the inside of the
    elbow.

11. Apply a liberal coat of PVC cement to the marked end of
    the long pipe. The cement should cover the entire outside of
    the pipe aprox. 1 in back from the end. 1. Wait at least a
    1/2 hour for the cement to cure before continuing with the
    next steps.

12. Insert the coupling into the vacuum inlet from the
    inside. Check to see that the elbow end does not interfere
    with any part of the vacuum. Check the fit as in steps 5 & 6
    in Section I. Also measure the distance between the outside
    end of the coupling & vacuum inlet. The assembly should be
    inserted in the inlet far enough to allow the long pipe to
    reach the bottom of the tub without contacting the side of
    the tub.

13. Check to see the measurement from step 12 is less than
    1/2 of step 3.

14. If the the result of step 13 is more than 1/2, cut the
    excess from the coupling. Remove any burrs or rough edges.

15. Insert the coupling in the inlet hole. Be sure the pipe
    is pointing straight down (perpendicular to the vacuum top).

16. Carefully set the top on the vacuum. It won’t be able
    reach it’s normal resting place because the pipe is too long.

17. Measure the distance from the top of the tub to the
    bottom of the top, right at the inlet hole.

18. Remove the top cover.

19. Remove the pipe assembly from the inlet hole.

20. Add 1 1/2 inches to the measurement from step 17.
    Transfer this measurement to the end of the pipe…

21. Cut the pipe at the mark & remove all burrs & sharp
    edges.

22. Clean the outside of the coupling of all dirt, oil &
    grease.

23. Clean the inside of the vacuum inlet hole of all dirt,
    oil & grease.

24. Apply a liberal coating of PVC cement to the inside of
    the vacuum inlet. Try not to get any on the potion of the
    inlet the vacuum hose connects to. Any excess can be wiped
    off with a paper towel.

25. Apply a liberal coating of PVC cement to the outside of
    the coupling.

26. Insert the elbow into the vacuum inlet. Be sure to
    position the pipe so it’s hanging down, perpendicular to the
    top. Hold the elbow & top in position for 10-15 seconds after
    the pipe is in the correct position. Place the top on the tub
    to allow the cement to dry. Be careful not to move the pipe
    while replacing the top.

27. Follow the directions on the cement container to
    determine drying time.

28 Any gaps that appear after the cement has hardened can
be filled with silicone bathtub caulk. Be sure to let the
caulk cure before subjecting it to a vacuum.

[Marrin_and_Mary_Dell]

A friend and I have been discussing another solution. Although
it does not address all the problems and variations discussed in
this thread, it does address the ones that currently concern me
the most: dust from grinding and polishing, and corrosive fumes
from pickling.

I am going to place a squirrel-cage blower below the polishing
bench, and direct the flow upward through a generously-sized
duct. “Taps” coming off this main feed will be of the radiused
variety, with the inlets placed so there is a venturi effect,
drawing air into the stream of air passing through the main
duct. The exhaust will outlet through the roof, and several
feet into the air. All the piping will be plastic. With this
arrangement, no “contaminated” air will pass through the blower,
stopping it up or corroding it.

At least, that’s the theory. Should it work, or not, I’ll pass
this “adventure” on to the group. It will likely take me months
to finish, but finish I will, and hope it works as planned.

[David_D_Arens2]

Hi Gang,

Marrin said,

  I am going to place a squirrel-cage blower below the
polishing bench, and direct the flow upward through a
generously-sized duct.  "Taps" coming off this main feed will
be of the radiused variety, with the inlets placed so there is
a venturi effect, drawing air into the stream of air passing
through the main duct.  The exhaust will outlet through the
roof, and several feet into the air.  All the piping will be
plastic. With this arrangement, no "contaminated" air will
pass through the blower, stopping it up or corroding it.

If you’d like, you could place the the fan assembly on the roof
(or some other out off the way location) and inject the fan
exhaust into venturi located inside the exhaust stack from the
shop. The size of the blower can be kept smaller by adding
dampers to all the inlets and only opening them when they are
needed. The tubing and fittings for this type of a system are
available from companies that sell woodworkers shop tools. You’d
probably have to find a different source for the squirrel cage
blower though. A good sheet metal shop should be able to provide
a venturi & blower for a system like this.

For efficient operation, this system requires a fresh air supply
to the shop (unless it’s already a drafty place). All the air
that’s exhausted through the roof has to be replaced. The fresh
air supply opening should be a little larger than the exhaust
duct.

One disadvantage of this type of system is that the precious
metal recovery at the polishing station will be less. It could
also affect the amount of fine particles left in the bench
sweeps, The smaller ones may go down (up) the tube.

Dave