Archive for the 'Jigs and Fixtures' Category

Finishing and using the pin chuck

Published on March 7, 2011 in Jigs and Fixtures, Machines and Woodturning. 1 Comment Tags: , .

Grinding the flat

Once the shaft slid smoothly into a 7mm pen barrel, it was time to cut a flat for the locking pin. I clamped the shaft in a vise and removed most of the metal with a grindstone in a Dremel rotary tool. Just as in hand sharpening, I locked my arms to my body, then used my legs to traverse the tool back and forth, about 75% of the way along the shaft. I got a fairly even cut.

The shaft, with its locking nail

Once I’d removed about a third of the diameter of the shaft with the grinder, I filed the cut flat. For this job I used a 10″ single-cut mill file. File teeth are graded relative to the length of the file, so a fine-tooth 10″ file has smaller teeth than a fine-tooth 12″ file, and leaves a nicer finish. A double-cut file cuts faster, but rougher. About 15 minutes of work got me a relatively flat surface along most of the shaft, as you see at left.

The nail I’d originally selected as a locking pin proved too large, so I used a #4 finishing nail instead, nipping off its head first. Here is the complete tool, almost ready for use.

Magnetizing

I say “almost” because, if your shop is like mine, having a little loose part such as the pin is a recipe for grief. It’ll get lost in no time, probably falling into the chips under the lathe the first time I pull a pen blank off it. So I ran the pin and shaft through a magnetizer. It doesn’t make them grip tightly—the pin can still roll so it locks, but it keeps the nail from sliding off the shaft.

In use

Here’s the new pin chuck in use. I held it in a Beale collet chuck (they have less runout than scroll chucks or Jacobs chucks), slid the desk pen blank on, and twisted it to lock it in place. I brought up the tailstock to stabilize things for most of the turning, parted off at the end of the bead, and pulled the tailstock out of the way to clean up and sand the part. It worked like a charm.

A pin chuck for desk pens

Published on March 3, 2011 in Jigs and Fixtures and Woodturning. Closed Tags: , .

The parts of a pin chuck

I was asked to turn a couple desk pens for people to use as they signed the guestbook at an upcoming wedding. Now I’ve turned a lot of pens, but never a desk pen, which sits in a “funnel”, rather than being clipped into a pocket.

Desk pens differ from other pens in that the top section is longer, and has a blind hole—it doesn’t go through the top. Instead, there’s a finial there. That means I couldn’t mount the blanks on a pen mandrel as I’d normally do. I needed a mandrel that could grip the upper pen blank from the inside, and support it as I turned it. What I needed was a tiny pin chuck. Today.

Filing the rod to size

Fortunately, they’re easy to make. Since I was building the pens with 7mm components, I started with a nail and some 1/4″ tool steel (O1 or W1 steels are readily available at hardware stores). 1/4″ rod is just a few thousandths of an inch too big to slide inside 7mm barrels. So I cut off a length, mounted it in a collet chuck on my lathe, and filed it to size. Note that when you file on the lathe, you do it left-handed, so the end of the file is off to the right, away from the chuck. You can really get hurt doing it right-handed, if the end of the file catches in the chuck.

Five minutes later, the barrel slid on easily.

I know filing steel rod to size sounds tedious, but it took no more than five minutes to reduce it to the point where the brass barrels slide on smoothly. There’s not much steel to remove. I polished the rod with sandpapers up to #600, and  then I was ready to cut the flat.

A pin chuck projects into a hole just slightly larger than it is. The chuck’s rod has a flat on it, and sitting on that flat is a smaller rod, such as a nail with the head cut off.

The diagram at left is a view from the tailstock of a hollow tube such as a pen tube mounted on a pin chuck. When the lathe spins counterclockwise, the little rod trapped in the flat rolls to the right, jamming the tube onto the pin chuck. It works amazingly well, jamming into blind tenons and tubes with dependability and repeatability.

Next post, I’ll talk about finishing and using the pin chuck.

The final product

Published on February 9, 2011 in Finishing and Jigs and Fixtures. 2 Comments Tags: , , , .

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The "flag", laid out on an offcut from the turning

The last step was to make the “flag” that signifies an 8th note in musical notation. I actually didn’t care about the musical timing, but needed the flag to hang the note on its stand.

I bandsawed off a slice from that large bulge I originally turned on the bottom of the blank, drew the flag, then scribed a line on the right, where the tenon would begin. Scribing this way keeps the wood fibers from fraying at the cut line, giving a clean cut. I scribed both sides.

Cutting the tenon on the flag

I cut out the flag and tenon area on a scroll saw, then mounted the piece on a horizontal router table to cut the 1/8″ thick tenon. Here you see it elevated on a scrap, secured by clamps. A 1/2″ spiral straight router bit comes in from the right, held by the horizontal router. The router table allows me to set a depth of cut, then move the workpiece horizontally to cut one side of the tenon. The router is held on a plate attached to a 16TPI threaded rod. Once I’d cut one side of the tenon, I just turned the vertical control handle 10 turns, to raise the router by the diameter of the bit plus the 1/8″ thickness of the tenon.

With the tenon cut, I carved a slight flat around the mortise on the stem so the flag would sit flush, then glued it place. I sanded everything, applied three coats of shellac, then waxed and buffed the note.

The note on its stand

Finally, I brazed together some cold-rolled steel—1/8″ rod and 1/8″ x 1/2″ flat stock, into a musical “staff”. I attached the staff to a steel plate at the same angle the note hung at, sprayed everything with black lacquer, and the project was complete.

I’ll mention in passing how handy it is for woodworkers to have a bit of metalworking capability. Brazing is easy (like high-temperature soldering), strong, and can be done with a MAPP gas torch in your driveway. It let me make a light, strong stand in scale with the note—something harder to do with wood, which isn’t as strong in small sections.

From a pile of parts to a jig

Published on February 5, 2011 in Jigs and Fixtures and Routing. Closed Tags: , , , .

The parts, ready for assembly

Here’s the pile of parts, waiting to become a jig. That loop in the front is 1/4″ threaded rod that I bent into a semicircle and covered with vinyl tubing. It’ll help secure the router in place, along with the knob at the back of the picture (which threads into a hole on the side of the router casting).

I inserted the carriage bolts and drew them up to bite into the melamine, then secured them with nuts. Nuts and washers near the top of the bolts support the top plate which holds the router.

Setting the height

Here’s the jig with the router in place. I set that height gauge on the left to the distance between the table that will support the router jig and the centerline of the lathe spindle. Now, it’s a simple matter to adjust the nuts up and down on the bolts until a bit chucked in the router is at the spindle height, and the router is level. The digital protractor in the foreground helped with the leveling.

The jig at work, cutting a mortise

It’s time to try it out! Here you see it in place on a plywood table that’s mounted on the lathe ways. I’ve clamped stops to limit the width and depth of cut, and chucked a 1/8″ spiral bit into the router. The note, not yet fully carved, is held in place on the lathe.

Here’s a close-up of the action.

Here you can see details of what’s happening at the business end of the router. Once that mortise is cut, I can carve the rest of the note so the stem flows smoothly into the body, and make a “flag” that plugs into the mortise. See it in the next post.

Starting the jig

Published on January 30, 2011 in Jigs and Fixtures and Machines. 5 Comments Tags: , .

Drilling the melamine

I built this device using scraps of melamine-coated particle board, a flat, low-friction material that’s perfect for jigs.

My design called for two plates, separated by the 3/8″ bolts and nuts shown in the previous post. To drill bolt holes that line up in the two plates, I attached them together with a couple small pieces of double-stick tape, then set the drill press fence and stops so I could drill all four holes.

Above you see the bottom of the jig, which sports four large counter-bores (holes that don’t go through) to accommodate the heads of the carriage bolts, so they won’t drag on the table as I move the jig around. I drilled them first, using a 1″ Forstner bit which drills a flat-bottomed hole.

Forstner bit speed table

A lot of people run Forstner bits too fast, then wonder why they burn the wood and won’t hold an edge. The table at the left came with my set, and it shows that I should run the 1″ bit at around 800 RPM. When I did, it cut smoothly, with no burning.

Forstner bits leave a tiny pit in the center of the hole, and I used that to line up for drilling through both plates with a 3/8″ bit to accept the bolts.

Backer blocks eliminate chipping

Melamine is very brittle, but when I set the drill for the right speed (about 2100 RPM on my machine) and backed up the cut with scrap wood, I got the clean exit holes you see at the left, with no chipping. Note that there is some fraying or chipping around the edges of the plate. This surface faced down when I cut it on the table saw, and I didn’t take the time to set up a zero-clearance throat plate on the saw (it’s just a jig, after all). Therefore, as the blade teeth exited the cut, they pulled a little of the brittle melamine away from the core. The throat plate would have taken care of that. Covering the cut line with masking tape can also help.

Next, assembling and adjusting the jig.

How to hit the high notes

Published on January 27, 2011 in Jigs and Fixtures, Machines and Woodturning. 3 Comments Tags: , , .

I belong to a woodturning club, and each month we have a President’s Challenge project, to get us to stretch a bit and try something we wouldn’t normally do. This month’s challenge is “Stemmed”.

The note at an early stage, on the lathe.

I think one of the secrets to success is to figure out what everyone else is doing and don’t do it. In this case, I’m betting a lot of people will turn goblets or pieces of fruit. So I wanted to make a musical note.

I mounted a 3″ diameter chunk of osage orange between centers, and turned the stem down to 5/16″ using classic spindle turning techniques. I left a large round piece at the bottom. At this stage, it looked rather like a top.

The next step was to mount it sideways, gripping that large round section between centers. Then I could turn the section down to become the body of the note. I had to turn very carefully, because that long, thin stem whips around in an almost invisible arc. I turned left-handed so I could cut in close to the stem while keeping my hands clear. You can see the note body (that ball on top) is complete, and I next have to remove the rest of that big wooden round. I’ve remounted it along the original turning axis for the photo.

A Porter Cable trim router is the right size.

Now’s the interesting part. I want to attach a “flag” to the stem, like a musical note would have. That means I need to cut a 1/8″-wide mortise in the stem to accept the end of the flag.

I had a little trim router perfect for the job. But I needed to be able to move it in a controlled way along the centerline of the turning. Time to make a jig.

Here are the guts of the jig.

I started with some scrap melamine-coated particle board, 3/8″ carriage bolts, nuts, and washers. Carriage bolts are nice for jigs because once their square shoulders bite in to the wood, they won’t rotate as you tighten bolts on them. By building the jig as a base and elevated platform, fastened by bolts, I eliminated the need for precision cutting and tricky measurements of router bit height. This jig would be adjustable! (That also means I can adapt it to other routers when this one dies.)

Next—turning that pile of stuff into a jig.

Doorbell: finishing the motor housing

Published on September 9, 2010 in Bending, Jigs and Fixtures and Routing. 4 Comments Tags: , , .

I trimmed the top and bottom edges even on the bandsaw, using the bending form to establish a reference surface.

After the motor housing was laminated into its curved shape, it needed trimming on four sides. This took some cogitation, to develop a reference surface against which to square the cuts. Here was my thinking.

The most important thing was that the housing should appear to sit square on the motor, with its front (curved) surface vertical. That surface was hard to use as a reference, but the inside of the curve (which was parallel to the outside) was easy. All I had to do was put the housing back on the bending form and press it against the curved nose. Then, if I spaced the form away from the fence and pushed it through the bandsaw blade, I’d cut an edge that would be square to the curved nose, as in the photo.

Trimming the ends of the curved housing was easy, again using the bending form.

Once one edge was done, I just flipped the form over and ran the trimmed edge against the fence to trim the opposite edge. The form supported the “U” shape, which otherwise would have chattered up and down as it grabbed and released the blade.

The next step was to trim the open ends of the “U”, square to the edges and even with each other. Here again, the bending form made things easy. I used a square to mark a line across the width of the form at the right distance from the curved end, and set the bandsaw fence so the blade would cut at the line. Then I pressed the square end of the form against the fence and cut first one side, then the other. They came out square and even. (Note—this worked because my form was wide enough to stay square to the fence. If it was narrow, I’d have used a sled or miter gauge to keep it square during the cut.)

The resaw blade was still on the bandsaw, and I resawed a 1/4″ thick slice of the same Honduran Mahogany used for the sides of the motor housing and glued it onto the top edge of the “U”. I glued it with the grain running along the sides of the “U” because it will expand and contract with changes in humidity, slightly flexing the walls of the “U”. If I’d glued it across the “U”, sooner or later its seasonal movement would have broken the glue bond.

Once the glue dried, I trimmed it within 1/8″ of the housing sides with the bandsaw, then used a flush-trim router bit in my router table to bring its edges flush. In this operation the bit runs against the grain for half the cut, potentially yielding a torn out surface. What I did was to use a normal cut (moving the piece against the rotation of the bit) for the right side of the cut, then use a climb cut (moving the piece with the bit’s rotation) for the left side. This way, the cut was always supported by fibers beneath it. It took several light passes, but the final cut was just about perfect, only requiring light scraping with a card scraper to produce clean, flush edges.

I sanded all surfaces to #180, then finished them with the same gel polyurethane varnish I used on the rest of the cabinet.

Next, the installation and lessons of the project.

Doorbell: Making the motor housing, pt. 2

Published on September 1, 2010 in Bending and Jigs and Fixtures. 5 Comments Tags: .

One of the secrets to serene glue-up is time.

I don’t like drama at glue-up time.

Once I had pre-bent the mahogany leaves that would make up the housing, they were considerably easier to stack and bend around the form. Now it was time to get ready.

Getting ready for me means doing a trial clamp-up without glue. I gather all the clamps I think I’ll want, then put them in place around the form. That way I can tell in advance if clamps will interfere with each other, or if I need extras. With no glue drying, I can think, change my mind—whatever I need to do. That’s when I saw that the leaves tended to move a bit on the form, and were difficult to keep in registration with each other.

Since I knew I’d have to fiddle with the slippery, moving leaves during clamp-up, I wanted a glue with long open time. I also wanted glue that dries rigid, unlike yellow glue, so I wouldn’t get any joint creep or spring-back. I chose 30-minute epoxy.

Three handscrews, a couple strap clamps, and a Bessey clamp were the right mix for this job.

I wrapped the form with waxed paper and put more waxed paper underneath. I mixed the epoxy in a plastic container, then painted it onto all four leaves with an acid brush. Next, I stacked the four leaves on the form, put a couple strap clamps in place, and pinched the whole assembly to the form with a Bessey clamp. This kept things stable.

I drew the leaves tight against the curved end of the form with the strap clamps, then added three handscrew clamps, which served to keep the leaves up against the straight sides of the form. All that, plus 12 hours of drying time, left me with a light, rigid, curved shell.

Next, the trim.

Doorbell: Precision cutting moulding parts

Published on August 18, 2010 in Jigs and Fixtures and Joinery. 1 Comment Tags: , .

The router bit made the top bead of the moulding. Beside it you can see the smallest of the three parts comprising the assembly.

The trim mouldings have to fit just right, and have to wrap around and return to the wall. I needed three partassemblies to wrap from the inside of the cabinet, across the face, and return to the wall with a tiny mitered piece. That means precise cutting. It’s no time for hand clamping to a miter gauge. Here’s my approach.

I build a small bandsaw sled for cutting the 45º miters. You see it  in the picture below.

I used the sled to cut a stop block with one mitered end, which you see held in the “F” clamp near the front of the sled. I backed that up with a second stop block, held in a spring clamp.

I used this sled on the bandsaw (with a new blade) to cut the mitered moulding sections to precise lengths.

To cut the longest moulding pieces, which have one 90º end, I squared the end of a strip of moulding and set the second stop block to cut it a little too long. Then I measured how much too long it was (compared to the cabinet sides), and inserted feeler gauge spacers between the stop block and the cut-off piece to get it to the right length before cutting it to final size.

The clamping board—a useful fixture

Published on July 1, 2010 in Jigs and Fixtures. Closed Tags: .

In the Jigs & Fixtures class, students make (among other things) a clamping board like the one shown in the previous post.

When I introduce the project, some students wonder what they would ever use it for. Especially if they’ve gone through many years of woodworking without ever building one before. But it just takes one time struggling with such hard-to-clamp situations as the arch moulding in the previous post to make believers of them.

I’ve put a description of the board, along with pictures and a Google SketchUp model of it, here in the Q&A/INFO section.