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If you would like to be notified when I post a new article, send me an email. I'll only use the list for that purpose, and I'll mail blind cc so your address won't be any the worse for spam. This article was published in the April 2017 edition of More Woodturning
Bag Clip Introduction
A bag clip is a utilitarian object that from an economic
standpoint makes no sense at all to make yourself.
No matter how trivial a value you place on your time, for the value of
making one of these bag clips you could buy a bagful of plastic clips.
Or stop by an office supply store for a bunch of binder clips.
Or, for that matter, get by for free by saving the rubber bands that hold
bunches of broccoli together (yes, of course you should eat your broccoli). But just like you don’t have to listen when “they” tell you
to eat your broccoli, you don’t have to pay attention to those who tell you that
time is money and money is everything.
Personally, I would rather surround myself, even when it comes to trivial
objects, with handmade items, than with plastic vomited from an injection molder
assembled by underpaid wage slaves.
Besides, it’s kind of a cute design that’s fun to make. Briefly, the jaw blanks for the bag clips are glued to a
waste block with temporary joints. A
1” hole is drilled through the assembly, then the jaws are turned to shape on
the lathe. A piece of PVC pipe,
which will serve both as a spring and to keep the jaws together. is turned to
fit the 1” hole. The PVC pipe is
slit lengthwise, then attached to the jaws with turned wood pegs with the aid of
a couple of jigs. Then the sides of
the bag clip are sanded and the bag clip is finished.
Making the Turning Blank
In order to make the circular segments in the jaws that
match the PVC pipe “spring”, the jaw pieces are temporarily glued to a waste
block before drilling. Much as I
hate to admit it, blue tape and an appropriate to the purpose glue, is not very
good at resisting shear forces. When
tuning the blank after drilling the tailstock tended to push the short piece of
waste block between the hole for the PVC and the tailstock in, particularly if I
used a safety drive center. A
traditional paper joint is better at resisting shear forces, but after you’ve
discovered the joy of no-clean-up temporary joints, sanding off the paper and
glue after splitting the joint is really a drag.
So I used a combination of switching to a pronged drive center and a cup
tailstock center, trimming off the tape from the ends of a longer blank, and
cutting the nubs down to the waste block last.
The pronged drive center requires less pressure to drive once it’s set.
The cup center applies pressure to the jaw pieces as well as the waste
block. The tape is thin enough
(0.005”) to allow a wood to wood glue joint at the ends.
And not cutting the nubs down to the waste blank until the more stressful
turning is done also helps. Rather
redundant, I guess, but it works. I used Ash for the jaws and Radiata Pine for the waste
block. The Ash was 3/4” thick and I
wanted the jaws to be 1” wide. The
Ash pieces I had were over 2” wide so I glued up enough for two blanks at once.
Cut the primary and waste wood pieces 4-3/4” long.
Cover one face of the primary wood pieces with traditional blue masking
tape and sand the tape surface to remove the coating so the wood glue will
adhere better. Use a utility knife
and a square to score the tape 3/8” from each end and then remove the tape on
the ends as shown in Figure #1. Figure #1: The
primary and waste wood pieces prepared for gluing. Spread a thin coat of wood glue over the taped surfaces and
un-taped ends of the primary wood pieces.
Place the waste piece in between them and clamp together as in Figure #2.
Use a clamp at each end directly over the un-taped regions and one in the
middle. Allow the glue to cure
before proceding. Figure #2:
Clamp the temporary joint until the glue cures. Trim the ends of the blank true, and rip into pieces 1”
wide if you glued up enough for more than one bag clip at once as in Figure #3.
Mark the center of the waste block at both ends and create a small
centering dimple with an awl. Then
use a mallet to set a pronged drive center in one end of the blank as in Figure
#4. By using a mallet you won’t
stress the temporary joint pressing the drive center in with tailstock pressure. Figure #3: Trim
the blank ends and then mark and dimple the centers. Figure #4: Set
a pronged drive center in one end with a mallet. Using a pencil and square, draw lines across the blank near
the ends where the tape stops. If
you are using a dark wood, it may be easier to measure 3/8” from each end.
Then measure 1” away from the line at the end opposite where you set the
drive center and draw a line across the blank with pencil and square.
Carefully mark the center of this line, as in Figure #5, for drilling the
hole for the PVC pipe.
Figure #5: Draw
lines marking the extent of the tape and the PVC pipe hole location. Clamp the blank to your drill press table with a waste
piece underneath to minimize drill exit breakout.
Drill a through hole with a 1” Forstner bit centered on the mark you made
in Figure #6.
Figure #6:
Drill a 1” hole for the PVC pipe spring. Turn the Jaws
Mount the blank between centers using a pronged drive
center and a cup tailstock center as in Figure #7.
Then gently plane the edges with a skew (or whatever tool you’re
comfortable with) until the edges are rounded as in Figure #8.
Figure #7:
Mount the blank between centers.
Figure #8:
Round over the edges of the blank. Now make V-cuts with the inside slope vertical following
the lines marked earlier as in Figure #9.
The skew is the most efficient tool for this but use the tool that
matches your own skills. Be sure to
leave some primary wood un-cut.
Figure #9: Make
vertical V-cuts at the marks 3/8” from the ends. Round over the nose of the jaws using a spindle gouge as in
Figure #10. Try to follow the
contour of the 1” drilled hole. You
only need to round over until the curve meets the intersection of the primary
and waste wood on the sides. If you
go past this point it can be adjusted with a V-cut later when removing the nubs. Figure #10:
Round over the front of the jaws. Round over the grip end of the jaws in the same fashion as
the nose end. Then cut a shallow
cove in between the drilled hole and the grip end of the jaws as in Figure #11.
Then blend the cove into the rounded grip end as in Figure #12.
Optionally reduce the diameter of the blended area slightly.
Figure #11:
Round over the grip end and turn a shallow cove.
Figure #12:
Blend the cove into the rounded over grip end. Reduce the nub at the grip end first until all the primary
wood is cut through. Then reduce the
nose end nub with a vertical cut as in Figure #13.
In order for the jaws to grip a bag across their full width the vertical
cut should cut back the nose to where the rounded edge intersects the line
between the primary and waste wood.
The bottom left image of Figure #13 shows a jaw nose rounded over too far.
The bottom right image of Figure #13 shows the nose after correcting this
with a vertical cut. Cut deep enough
that all the primary wood is cut. Figure #13:
Reduce the nubs to only waste wood and adjust the vertical nose cut if needed. You can sand the turned surfaces of the jaws while still on
the lathe. Drill Jaws for the Pegs
Remove the turned blank from the lathe.
You can remove the nubs with a bandsaw to get them out of the way.
Use a putty knife and mallet to split the temporary joints as in Figure
#14.
Figure #14:
Split the temporary joints. You can use a slip of paper to help mark the jaws for
drilling the peg holes. Cut a piece
of paper about 1/2” wide and 2” long.
Fit it into the circular segment, crease the paper at the ends of the
segment and run a pencil along the ends of the segment as in the top right image
of Figure #15. I used removeable
adhesive to keep it in place for the photos, but fingers will probably suffice.
Remove the paper slip and mark along one edge of the paper the midpoint
between the two end marks. Replace
the paper in the circular segment and mark the center of the circular segment as
in the bottom right image of Figure #15.
Use a ruler to mark the center point between the sides of the jaw.
Install a 1/4” (or whatever size you’ll turn the pins to) drill bit in
your drill press. Set the drill
press depth so it’s just above the drill press table or cross-vise as in Figure
#15. If you’re using a cross-vise
(which I heartily recommend) clamp the bag clip jaw between the vise jaws.
The arch of the bag jaw should be in contact with the vise bed, and the
flat inner surface of the bag clip jaw should be parallel to the vise bed.
Adjust the cross vise so that the drill bit is centered where you marked
for drilling and drill the hole for the peg as in Figure #16.
Repeat for the other bag clip jaw. Figure #15: Set
the drilling depth and mark the jaws for drilling.
Figure #16:
Drill the peg hole. If you don’t have a cross-vise you can use a hand screw
clamp to hold the bag clip jaws as shown in the top right image of Figure #16.
Again, be sure the arch of the bag clip jaw is in contact with the table
and that the flat of the bag clip jaw is parallel to the table.
A pencil line on the inside of the hand screw clamp might help with the
latter. If you have neither a cross-vise nor a hand screw clamp you
can use any pair of clamps plus a couple of straight wood scraps.
It would be easier to adjust the bag clip jaw between the wood scraps are
3/4” high. This is shown in the bottom right image of Figure #16. Make the PVC Spring
The spring is made from 3/4” PVC pipe, which is a little
over 1” in diameter. Most of us
don’t have a 1-1/16” Forstner bit, so it’s easier to turn the diameter of the
PVC down so that it matches the 1” diameter bit we do have.
Mount a short section of PVC pipe between #1 jaws on a 4-jawed chuck and
a large cone center as in Figure #17.
An alternative mount would be to turn wooden stub tenons and mount
between centers. Turn the PVC pipe
down to a 1” diameter. I’ve found a
slightly rounded negative rake scraper works well, although not much of the
exterior surface of the pipe is visible when the clip is assembled so you could
also just use gentle cuts with a spindle roughing gouge.
Use a narrow parting tool to cut off a section a little longer than 1”
(the width of the jaws) to allow for trimming after assembly.
Figure #17:
Mount the PVC pipe and turn to 1” diameter, Now cut a slot lengthwise in the PVC pipe section.
You can cut it on the bandsaw as in Figure #18, or clamp it in a vise and
cut with a bandsaw.
Figure #18: Cut
a slot lengthwise in the PVC pipe. Now make a wedge to pry open the PVC pipe spring a little
while you align it for mounting the jaws.
This is necessary so the jaws will exert pressure when closed.
The wedge should be about 3/16” thick for 1”, then tapering to a point.
This will feel safer to cut out of a larger piece.
Start with a piece of wood about 3/8” thick that has a straight edge.
Draw a 2” line 3/16” from and parallel to a straight edge.
Measure 1” from the end of the line and draw a sloping line from the
straight edge end. Cut the slope
first, then cut the rest of the wedge out.
The wedge makes it easier to insert in the slot of the PVC spring as in
Figure #19.
Figure #19: Make a wedge to hold the PVC spring in a
slightly open position. Turn the Wooden Pegs
The most common calipers used in spindle turning are often
called spring calipers because the tips can spring apart.
This is a useful feature when the diameter you’re cutting to will be a
final surface because they don’t burnish or compress the wood as much.
However, when you’re cutting a tenon to be glued into a mortise,
compressing the wood can be an asset.
If you put the glue into the mortise and then insert a moderately
compressed tenon, the moisture in the glue will expand the tenon locking it
quickly in place. Back in 1984 I
learned this tip from Russ Zimmerman. You can make a tenon gauge from steel or brass that’s
thinner than the parting gauge you’ll be using.
For use with a standard diamond shaped parting tool 1/8” thick steel
works well. For small tenons cut
with a 1/16” narrow parting tool 0.05” thick brass works well.
Cut the slot just a little undersize of 1/4” with a hacksaw and file to
size. Round over the corners a bit
so they don’t cut. If you
accidentally make the gauge too wide you can narrow it with a series of blows
just inside an edge with a center punch and hammer. Rather than making a gauge, you may be able to just use an
open end wrench if that size is narrower than your parting tool.
You won’t be able to easily modify the size of an open end wrench, so
turn a few test tenons with it and see what size drill they best fit.
Figure #20 shows a completed peg, a homemade 1/4” steel tenon gauge, and
a 1/4” open end wrench. Tenons made
with my open end wrench fit best in in a mortise drilled with a F drill
bit. To use either tenon gauge, bring the gauge up against the slot your cutting
with a parting tool. When the gauge
slips on (leaving a groove of compressed wood) turn the rest of the tenon the
size of the uncompressed wood cut by the parting tool, then bring up the tenon
gauge and move it from side to side over the entire tenon.
Figure #20: A
completed wooden peg, a homemade steel tenon gauge and an open end wrench used
as a tenon gauge. To determine the length of tenon for the pegs, measure the
depth at the outer wall of the drilled mortices of both jaws.
Add the shorter depth to the thickness of your PVC spring wall. Chuck up wood for the pegs in a chuck as in the top image
of Figure #21. I think a collet
chuck is the most finger friendly option.
For the photos I used 3/8” maple dowel, but a collet chuck will hold
accurately cut square stock as well.
Make a gentle planing cut the length of the dowel.
Then slightly dome over the end of the dowel. Make a pencil line 1/8”
from the end and cut to the tenon diameter with the tenon gauge.
Chamfer the shoulder of the head of the peg slightly as in the middle
image of Figure #21. The chamfer
makes it less likely that you’ll crack the head inserting it tightly into the
rounded inner surface of the PVC spring.
Mark the length of the tenon and cut using the parting tool and tenon
gauge. Turn any remaining tenon area
to diameter and run the tenon gauge back and forth over the entire tenon.
Then cut a chamfer on the end of the tenon as in the bottom image of
Figure #21 to make it easier to insert.
Then part off the peg using a narrow parting tool.
Hold on to the peg with one hand so it doesn’t go flying. If you’re not
comfortable with that, then cut part way through and finish cutting the peg off
with a small hand saw. If your shop
is messy like mine, then store the pegs somewhere safe so that they don’t get
lost. You could blue tape them to
your workbench.
Figure #21:
Turn the wooden pegs. Assemble the Bag Clip
A jig will make it easier to insert the pegs into the PVC
spring. Start with a
piece about 3/8” thick, 3/4” wide, and 6” long.
Drill a 1/8” deep hole close to one end with a 3/8” Forstner bit.
Narrow the end at the hole in both width and thickness with a bandsaw or
utility knife. Figure #22 shows the
jig with and without a peg. To use
the jig, place a peg in the drilled hole.
Hold the PVC spring with the hole you want to insert the peg in facing
up. Use the jig to place the peg
under the hole and press upwards.
You may need to insert the wedge in the slot of the spring to place the second
peg.
Figure #22: A
jig will make peg insertion easier. Put both bag clip jaws on your workbench oriented as they
will be when assembled. Mark the
center lines of the peg holes on the sides of the jaws facing up.
Put an extra line on the upper jaw as in Figure #23.
The marks on the jaw sides will let you mark the PVC spring for drilling
and assemble them correctly if they aren’t quite identical.
Figure #23:
Mark the jaws for assembly. Insert the wedge in the PVC spring and place it between the
jaws. Bring the points of the jaws
together and orient the wedge so that it’s aligned with the jaw points.
Transfer the marks on the sides of the jaws to the side of the PVC spring
as in Figure #24.
Figure #24:
Transfer the marks on the sides of the jaws to the PVC spring. Use a square to extend the hole locator marks
perpendicularly down the side of the PVC spring.
Find the midpoint of each line and make a mark as in Figure #25 to mark
the PVC spring for drilling.
Figure #25:
Mark the PVC spring for drilling. Clamp the PVC pipe end to end in a vise with one drilling
mark facing up. Create a starting
dimple with a center punch or awl.
Then drill a hole that matches your peg size as in Figure #26.
Repeat for the other hole.
Figure #26:
Drill holes for the pegs in the PVC spring. Clamp something flat and sturdy in your vise.
In the photo I’m using 1/2” square key stock.
If you use something round, such as drill rod, and don’t center the peg
head on the rod, you may crack a side of the peg head.
Insert a peg in the side of the PVC spring marked as upper and place it
on the flat close to the vise as in Figure #27.
Figure #27:
Insert a peg in the PVC spring and place it on the flat clamped in your vise. Select the jaw marked as upper.
Insert some glue in the peg hole with something like bamboo skewer and
spread it evenly around the sides of the hole.
Then use a mallet, as in Figure #28, to set the peg into the hole.
The joint should set quickly, but give it a few minutes anyway before
further handling. Yes, my mallet has
been abused. I confess to sometimes
striking metal objects with it. It’s
also getting on in years.
Figure #28: Set
the peg into the upper jaw. Insert the wedge in the spring. Use the jig to insert a peg
in the other hole, and place the PVC spring on the flat in your vise.
Insert glue in the hole in the other jaw and then use a mallet to set the
peg in the hole in the other jaw as in Figure #29.
Set the assembly aside until the glue sets.
Figure #29:
Glue the peg in the other jaw. Tweak the fit between the jaws so the entire width of the
jaw will grab a bag by doubling over a strip of 80 grit or so abrasive and
drawing between the jaws a few times, as in Figure #30.
Sand the sides of the PVC spring flush with the sides and sand out any
tear out on the sides of the jaws as well as in Figure #31.
You can then apply finish if you like.
The completed bag clip shown in Figure #32 was finished with linseed oil.
Figure #30:
Tweak the jaw fit with folded over abrasive.
Figure #31:
Sand the PVC spring flush with the sides.
Figure #32: The
completed bag clip. The bag clips should be sturdy in use.
I’ve dropped them as well as kept them for a time in both the
refrigerator and freezer without apparent damage.
It is possible to over-extend the PVC spring so that the spring loses
tension when closed. This should
only happen if you use the bag clip as a hand exerciser or pass it around a room
full of guys at show and tell. If you don’t like using the pegs, it’s possible to use
machine screws. To do this you would
drill and countersink the jaws for the screws (such as 1/4x20x1/4 or 12-24x1/4
pan head screws) before turning. Put
the jaws around the wedged spring as in Figure #24 and mark the spring for
drilling through the holes in the jaws.
Then drill and tap the holes in the spring.
You could either leave the screw heads exposed or cover them with a
wooden plug.
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