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This jig helps you simply reverse your work for base turning.

Properly completed bowls by no means reveal how the turner mounted them. However, conventional strategies for reversing a bowl to show the bottom contain loads of fuss and hassle. Cole Jaws, for instance, require cranking no less than 48 hex screws for every use (to not point out the aggravation of getting to scrabble within the shavings for dropped screws).

Leslie Longworth should have been aggravated, too, as a result of he did one thing about it. Two many years in the past he conceived an ingenious self-centering scroll chuck that does the reversing job quick and elegantly. Unfortunately, it attracted little curiosity, maybe as a result of it seems difficult. His directions have been incomplete, as a result of he was in a position to write solely the primary of two meant articles on its building earlier than passing away.

However, with a bit of creativeness, the primary article incorporates sufficient info to not solely make his chuck however to develop it additional.

This 15″ model of the Longworth chuck has six lengthy jaws. Here, it’s getting used to carry a small spalted maple bowl.

The chuck is only a pair of counter-rotating disks. Their most radius is a smidgen lower than the gap between the lathe’s headstock and mattress. Outboard turners may dimension chucks to accommodate nonetheless bigger work, however they need to contemplate rising the thickness of the supplies. One additional outboard consideration is that the routed arcs ought to be reduce in the wrong way from these described beneath if the headstock is just not reversed such that the workpiece is rotating counterclockwise.

Some preliminary feedback earlier than beginning to construct:

1. Longworth’s design reveals solely 4 jaws that aren’t nicely suited to deal with facet strain. I found that it’s simply as straightforward to make a six-jaw chuck.

2. It’s essential to do the next steps so as. Trust me.

3. The spinning jaws and wing nuts can damage. Rather a lot.

Start by reducing matching disks of 34” MDF for the again and 14” Baltic birch for the entrance. Other supplies would possibly work, however I do know these keep flat.

The subsequent step is selecting find out how to mount the chuck on the lathe. You may flip a hardwood flange to suit your scroll chuck’s jaws, and glue and screw it to the MDF disk. However, a self-mounting chuck is a comfort, so including a small faceplate works nicely. It additionally ties up an costly part, as a result of eradicating and changing the faceplate would quickly put on the screw holes within the MDF. An different is a nut with the identical thread because the lathe’s headstock. (See “Make the Headstock” on web page 55.)

Use your band noticed to chop matching disks of three⁄4″ MDF for the again and 1⁄4″ Baltic birch for the entrance.

Whatever you determine, tack the entrance disk to the again disk with 4 small ending nails set about 12” in from the rim. Mount the meeting on the lathe, true up the rim, and spherical the perimeters.

The layouts for each a four-jaw and a six-jaw chuck. (You may use a trammel for each layouts.)

Now for essentially the most essential step: Use a chuck within the tailstock to drill a 116” gap by means of the precise middle of each disks. This gap will make sure the chuck runs true after closing meeting.

Remove the chuck from the lathe and clamp it in a vise. Draw three circles. The smallest is the diameter of your faceplate or nut, plus about an inch; the biggest is the diameter of the disk much less about an inch; the center circle is centered between the opposite two.

At this level, should you’re making a chuck bigger than about 14″, you must determine what number of jaws you need. I’ve made each, and whereas 4 are ample, I like to recommend six. The photograph on the backside of the web page reveals the layouts for a four-jaw and a six-jaw chuck. For 4 jaws, draw two perpendicular traces by means of the middle of the 116” gap you drilled earlier. For six jaws, draw three traces at 60° angles. I used drafting triangles.

Use a stable carbide upcut router bit to chop your arcs, as it will produce the cleanest reduce in each plywood and MDF.

Dimple the intersections of the diameter traces with the center ring, after which use the dimples to attract arcs from the outer ring to the tangent of the interior ring. (Drawing these arcs helps keep away from errors whereas routing.) Keep the compass set for the router jig.

I made a circle-cutting base  (photograph subsequent web page) for my router out of 14” Baltic birch. The gap is 3″ in diameter for good imaginative and prescient, as a result of all begin and cease factors are by eye. With a 14” bit in a router, set the compass pin towards the sting of the bit closest to the wing on the router base, and draw a brief arc on the wing. Drill a 116” gap by means of that arc and insert a  nail as a pivot pin. Push it by means of in order that about 12” protrudes and set it in a dimple on the disk. Push the jig flat and hammer the nail in no less than 18” to make sure the jig can’t slip out of place.

The buttons on the entrance of a 10″ four-jaw chuck and the wing nuts on the rear of a 15″ six-jaw chuck.

Routing the arcs is very easy that one can develop into a tad complacent and make a ruinous mistake. Take your time. Begin a reduce by plunging the bit partially into the work about 1″ away from an out of doors begin level, again it as much as that time –cautiously; it is a climb reduce – after which pull ahead to the tip level. A stable carbide bit required solely two light passes to undergo each disks. Repeat till all arcs are reduce. The consequence will appear like the photograph at above proper.

Now drill finger holes (about 34” diameter) across the perimeter of the disk sandwich; drill 4 for a small chuck, and 6 for a big one. These present the means to counter-rotate the disks to set the jaws.

A #10 x 1″ roundhead wooden screw with an unthreaded shoulder serves as an axle, so enlarge the middle gap within the entrance disk simply sufficient for a cosy match on the screw shoulder. Enlarge the middle gap within the again disk to the within diameter of the screw’s thread.

Sand each faces of each disks clean, taking specific care to do away with any fuzz on the perimeters of the routed arcs. Apply a few well-buffed coats of paste wax to the face of the MDF disk, and to the face of the Baltic-birch disk that has the drawing on it. This will ease rotation. Now reverse the entrance disk and place it towards the again disk in order that the routed arcs cross. Drive within the axle screw, and again it off simply sufficient to allow the entrance disk to rotate. This completes the chuck physique.

Now for the jaws. The photographs above present the buttons on the entrance of a 10″ four-jaw chuck and the wing nuts on the rear of a 15″ six-jaw chuck.

The jaws are comprised of rubber leg suggestions obtainable from {hardware} and housewares shops. (Do not purchase the vinyl variations. They don’t grip.) The 58” sleeve kind is greatest for giant chucks, and in addition supplies extra attain. However, I’ve discovered the screw-on button kind is your best option for smaller fashions.

The sleeve suggestions require wood inserts for attachment, so flip a dowel to 58” diameter, and reduce lengths to suit inside every sleeve. Drill 14” holes lengthwise by means of the highest of the rubber tip and the dowel. With 14” x 212” machine screws inserted by means of the dowels and the arcs, wing nuts and washers on the rear of the again disk make for fast and straightforward adjustment.

The buttons that again the sleeve suggestions require washers (smaller in diameter than the buttons) beneath the screw heads to compress the buttons towards the workpiece.

Rotate the disks till the outer ends of the arcs overlap. Insert the jaws and place the washers and wing nuts loosely on the again facet. Rotate the entrance disk once more, and watch the way it completely synchronizes all 4 or six jaws as they transfer out and in. Place a reversed bowl towards the disk face, rotate the jaws till they press towards the outer – or interior – fringe of the bowl, tighten the wing nuts, and the entire unit is safe.

Now, retire your Cole Jaws and jam chucks.

Make the Headstock

Headstocks on smaller lathes typically use commonplace pipe thread, and nuts are available. Unfortunately, for these with 1 14” headstocks, the usual 1 14” pipe thread is seven enamel per inch (TPI), so that you’ll need to go to a specialty supplier for 1 14” x 8 TPI nuts. I purchased a number of and have been utilizing them to make quite a lot of faceplates. To mount them, I drill and countersink three holes by means of the face of the nut – the steel is comfortable – and use wooden screws to lock it. (Size the holes so the screws match snugly.) A small nut has an additional benefit in that the diameter of the nut/faceplate establishes the restrict of inward journey for the buttons.

However, producers don’t have any want to make sure the faces are completely coplanar. All of mine have been off just a bit, inducing wobble within the chuck. The repair is just not troublesome. You can put the nut on the headstock, and use a sanding disk within the tailstock to face it. Alternatively, mount the nut on the MDF disk centered in addition to doable. Although this positioning is just not vital, I turned a plug that may simply squeeze by means of the nut, and drove a small ending nail into its middle. By dimpling the middle of the disk, the nail will make sure the nut is centered. Tapping the three screws with a hammer marks the pilot holes.

If your nut does induce wobble, you may cut back it to nearly nothing by shimming one facet of the nut with a single enterprise card. Eliminate the remainder by going through the rear disk.

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