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This article was published in the April 2017 edition of More Woodturning

Bag Clip as 6 page pdf

 

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.

Main

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.

 

 Fig01

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.

 Fig02

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.

 Fig03

Figure #3:  Trim the blank ends and then mark and dimple the centers.

 Fig04

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.

Fig05 

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.

Fig06 

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.

Fig07 

Figure #7:  Mount the blank between centers.

Fig08 

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.

Fig09 

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.

 Fig10

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.

Fig11 

Figure #11:  Round over the grip end and turn a shallow cove.

Fig12 

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.

 Fig13

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.

Fig14 

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.

 Fig15

Figure #15:  Set the drilling depth and mark the jaws for drilling.

Fig16 

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.

Fig17 

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.

Fig18 

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.

Fig19 

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.

Fig20 

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.

 

Fig21 

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.

Fig22 

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.

Fig23 

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.

Fig24 

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.

Fig25 

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.

Fig26 

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.

Fig27 

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.

Fig28 

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.

Fig29 

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.

Fig30 

Figure #30:  Tweak the jaw fit with folded over abrasive.

Fig31 

Figure #31:  Sand the PVC spring flush with the sides.

Fig32 

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.