Sunday, November 27, 2011

Lattice Jig


Granddaughter and kids went home yesterday.  We went to Lowe's where Lora bought a white Christmas tree (something she has always wanted) and I bought a quarter sheet of birch ply (something I can always use).  I adjusted the platen on my thickness sander, and put a coat of poly on the drum.  I will put another coat on today, then during the week, I'll install the sandpaper, and all is for the good.

The lattice jig is really a rather simple affair, though it is somewhat ingenious, and I don't know who to credit for that ingenuity.   I took my design from LMI, and simplified it.   It is used for joining the plates for the back and soundboard.  I'll picture its work when I get to joining the plates for my next guitar,

It consists of two lattices, each of which consists of two rails (thinking of the rail road analogy again) and three ties (with a bad pun on ties).  It is assembled using standard wood-working techniques.  I cut 2 inch strips to length, then set up my dado blade to cut over-lapping notches.  I cut them slightly deep, at about an inch and an eighth, so I could keep it all perfectly flat during glue up.

The bottom lattice required the most work.  Between the notches for the two rails, I removed enough material to accommodate 1/4 inch MDF and some sheet plastic.  It provides the base against which the top rails bear, keeping the plates flat at the seam.

On one side, the rope is knotted into a single hole, and on the other, once it is crossed back and forth over the plates, it is snaked through the three holes pictured.  Drill the holes before assembly.  I glued and pinned it on my table saw, so it would be perfectly flat, threaded the rope and tested it on some scrap 1/8th ply.  It worked as advertised, so I can actually begin work on the guitar.  I will need to dig through my wood, but I believe I salvaged the mahogany for the back and sides, along with a book-matched piece of redwood for the soundboard.

If not, I will need to wait for the pieces needed to repair my band saw come from the manufacturer, and there is another project that I can tackle -- a circle cutter to define the rosette channel.  For that, I need a 1/4 inch brass rod (about 12 inches).  I have the necessary screws and inserts -- those I did salvage from the flood -- and the body I can make from oak off-cuts left over from the bench.  I could also continue making my shop cabinets.  I have in mind a router cabinet and another to hold my hand held power tools.  Never a lack of things to do.         

Friday, November 25, 2011

Thickness Sander and Lattice Jig

I have given this some thought on and off over the holiday, between games with my granddaughter, and remembered something that was implicit in my design for the thickness sander all along, though I wasn't completely cognizant of it. The cross member that holds the hinge is not structural and was unintentionally, or perhaps intentionally behind the white noise that usually fills my head, set up to allow for adjustment. Consequently, I have resolved on the plan to withdraw the screws that hold the hinge support in place on the out-feed side. With the adjustment screw fully extended, I will then bring the hinge end of the platen up until it touches all the way across the drum, and screw the hinge support back into place. I've taken a straight edge to the drum, and it reasonably flat along its length all the way around its diameter, so to continue down my current path would simply distort the drum, making the radius smaller on one side than on the other. I will do this Saturday, when the kids and granddaughter return to Boise.

Also, in the meantime, I have been giving some thought to the first step in actually building the guitar, the plate joining for the soundboard and back. I have used the method that Sloane describes. After getting a good light-tight joint, on a work-board, one places a dowel or metal rod under the plates, taps nails along the two edges of the plates (not into the plates, but abutting them), removes the nails and presses the plates flat against the work-board, places a caul over the joint, and then weights that down. For weight, I used edger bricks wrapped in duct tape, but about anything suitably heavy would do. This works reasonably well -- that is to say, it works -- but I wouldn't necessarily recommend it. A couple of reasons, the most important being that you can't really see the joint as it is coming together and its difficult to get even pressure along the length of the joint with the caul, so there have been occasions where plates, perfectly thicknessed, have not come together sufficiently flat at the seam. I have had to cut them apart, re-joint the plates, and go through the steps again.

Consequently, I have been thinking about jigs to join the plates, and the one that holds the most promise is the lattice jig. I call it that for lack of a better term, but it is the jig sold by LMI. Though it has nice features, the price is a bit steep, and I think LMI, in particular, sets prices on such things as if to say, "look, if you're too lazy or impatient to build your own jigs, then you shouldn't be building guitars." Regardless, my next project will be the lattice jig. I will build it from birch ply, cutting strips about 2.5 inches in width and about 22 inches long. It will consist of basically two lattices (think a section rail road tracks with three ties) put together with interlocking notches. On the bottom lattice, on the ties, between the notches for the rails, I plan to remove about 3/8ths. This will accommodate 1/4 MDF and sheet plastic, that will provide a solid flat surface. On each end of the rails, I plan to drill three holes, large enough to thread rope. The three holes should provide enough friction to lock the rope in place, but if not, the exposed loop can be clamped to hold it. To use it, the plates are sandwiched between the two lattices, rope is crossed over the rails, locked into place, and then to provide clamping pressure, a wedge is tapped under the crossed ropes. The lattice holds the plates flat while the ropes provide pressure not only against the edges of the plates, but also to lattice. The trick to this will be keeping the lattice perfectly flat during construction.

A quarter sheet of birch ply should provide enough to build the lattice jig, with enough left over to build the jig that will build the radius dishes for sanding and gluing the braces on the sound board and backs.

Sunday, November 20, 2011

Thickness Sander Continued



I was able to accomplish more than I had anticipated, in part because my wife and granddaughter took longer than expected to travel from Boise. The almost finished sander is pictured from the in-feed side, and you can see the simple adjustment that raises and lowers the platen. The eye-screw is threaded through an insert and pushes against a mending plate, which helps prevent the screw from digging into the MDF.

I say, "almost finished," for a couple of reasons. The drum still needs to be rounded over completely and adjusted to the platen. Viewed from the in-feed side, it is between 1/32 and 1/64th of an inch higher on the right side. I am rounding and making the adjustment by running a sheet of sandpaper attached to a piece of scrap ply through the sander as it turns. It may be quicker to back the screw out and tap up the right side of the platen, but we will see where my patience takes me.

Also, of course, once adjusted, I will need to attach the sandpaper to the drum. I have ordered adhesive back sandpaper from Amazon, and I think it will do the trick, but here again, we shall see. It hasn't arrived yet, perhaps to my benefit, because I would have been tempted to put it on before rounding and adjusting the drum. If not, I have a back-up plan for a pair of hold downs on either side of the drum, but I am hoping they will not be necessary.



A couple of problems did emerge. Pictured is the power-train for the drum. The belt runs between two pullies, the one attached to the arbor of my table saw is a one inch diameter, the one attached to the drum is a two inch. The rotational speed of the drum seems about right -- not sure what it is exactly -- but the bottom pully had to be modified to fit on my saw arbor. I had to cut away the set screw. Since it was aluminum, it cut away easily.

Also, on the right side, during the trail run, the bearing on the right side grew very hot -- literally smoking hot. The problem was a small set screw that holds the interior sleeve of the bearing firm against the arbor. It is visible in the photo. There were two on each bearing, and on the right, one of the set screws wouldn't remain set. It had backed out and was turning against the housing generating the heat. I removed it, and now things seem to be fine.

Finally, when the bearing over-heated, the drum came loose on the arbor. The two events were most likely not connected. It is held firm to the arbor by two bolts on either end which are cranked in against either end of the drum. It seems to be holding fine now, but if necessary, I will pin the drum through the arbor. Here again, I am reluctant to do so, because that too will require dis-assembly, but will do so if necessary.

Saturday, November 19, 2011

Thickness Sander Continued



The pieces of the platen are pictured. I'll begin this morning by gluing the edge pieces up to the platen, and while that dries, I'll begin work on the base. I have a 2/6 piece of construction lumber that will serve as the base. It's been in my shop for a while, so it should be about as stable as possible for the humidity of the area. Today, I'll prep the lumber -- cut off the factory rounded edges, and run it through my thickness planer until I get clean surfaces -- and cut everything to length.

The assembly will be rather straight forward. There will be two sides, which hold the bearings, and two cross members. I will use half lap joints for the cross members, gluing and screwing them into place. At the front of the sander, where the platen is hinged to tilt up to the drum, I want to have a cross member, butt jointed into place with screws. I want to set it so the hinged platen is about 1.5 inches from the drum when it is fully flat. That should leave enough clearance for other sorts of projects, beyond the guitar (my wife has her eye set on "tea-boxes" that could be sold at the open market this coming summer). In the back, set at the same height, will be another cross member, through which the height adjustment screw will be threaded. The width of my table saw will determine the length of the base -- approximately 30 inches -- which will leave sufficient over-hang for the operation of the adjustment screw. The width of the platen will determine the width of the base. I'll make adjustments as necessary.

The object is to keep the construction as simple as possible. I had in mind another "sliding" method of adjusting the platen, but gave up on it for the sake of simplicity.

Thursday, November 17, 2011

Thickness Sander Continued

As I've said in an earlier post, there is an order of precedence in the building of a guitar. It isn't minutely exact, but from my perspective at least, it is exact enough. It begins with the sound board then moves to the back plate. For the sound board, there are essentially five steps (1) re-sawing the plate to an approximate thickness, (2) edge gluing, (3) refining the thickness, (4) installing the rosette, and (5) gluing on and shaping the ribs.

Re-sawing is a common woodworking operation, so I won't comment at length here. Besides, I think, most buy their plates from LMI or others at the approximate thickness. I do have some redwood, however, that I rescued from the lumber yard that I want to use for plates. Someone must have recognized it as special and pulled it from a decking pile. The grain is close, tight, and the board rings when tapped with a knuckle. I have cut several plates from it, and I plan to use a set soon.

The drum sander is used at step two, refining the thickness. I have used planes and sanding planes in the past. They work well, of course, but planes have their limitations on highly figured wood, and sanding planes are, well, tedious. I prefer to relegate them to the job of finish sanding, working up through the intermediate grits, then finishing with a sanding block on the fine grits. I have made the drum wide enough to accept the full width of the guitar, so I can edge glue the book-marked plates before refining the thickness.

The next step in the construction of the drum sander itself will be the adjustable platen. It should be relatively simple. I see it as a 20x30 laminated piece of 3/4 MDF and 1/4 hardboard, the latter replaceable if damaged. The design consideration was this: the drum itself is 20 inches wide, and my table saw is 30 inches wide. Since I envision the drum being turned by my table saw motor, that seemed appropriate. I will run a rib along the 30 inch side of the platen at about 2.5 inches thick, this to insure the MDF remains flat along its length, with a notch cut where the bolts secure the drum to the arbor. Since my wife will be in Boise this evening, fetching our grand daughter for the holidays, I hope to stop at the Depot or Lowes on the way home and get what I need to make the platen.

Wednesday, November 16, 2011

Thickness Sander




I have begun work on the thickness sander. Actually, I had begun work a couple of weeks ago on the drum. It began as scraps of birch ply (left over from the apothecary cabinet and the shop cabinets you see hanging in the background) cut to 4x4. I drilled the 5/8th inch hole for the arbor in the center of each and glued them up on the arbor in three sections, then glued up the three sections. MDF would, perhaps, have been better, and if I were buying the materials specifically for the sander, I would have gone with MDF, but the ply, I think, will do and eliminated a number of scraps that would have otherwise cluttered my shop. Once glued up, I then nipped the corners off the squares, as close to the finished diameter as possible, then set up my router lathe.

It too was made from scraps around my shop and consisted of two end pieces, slightly wider than the widest spot on the now octagonal drum. I drilled a 5/8 inch hole about an inch down centered on the end pieces to support the arbor. For the sides of the lathe, I ran a quarter inch groove along the length, then screwed the sides to the end pieces so the groove was about a quarter inch above the drum. I then made a base for my router out of quarter inch hardboard, sized to slide in the two grooves, then rounded over the drum by sliding the router back and forth in the groove as I turned the drum beneath it. The process is a bit tedious, in part because you don't want to crank the router down and take too big a bite, and would perhaps have gone more quickly had I cut circles instead of squares, but my bandsaw is still out of commission from the flood in Chicago. I received the motor, but it did not come, as I had anticipated, with the mounting plate, so now I am awaiting that. Altogether an exercise in patience.

Monday, November 14, 2011

Apothecary Cabinet & Bench


I have finished two new projects for my wife, the apothecary cabinet and a bench to match the dining room table. Both were accomplished with more or less standard woodworking techniques.

On the apothecary cabinet, I built the carcass, then fit the drawers and doors to the cabinet. The cabinet was slightly out of square, so that required some fiddling, but it came together adequate for my wife's purpose -- having many drawers to store the sorts of things that one can't find when one needs them, everything from batteries to dog brushes. Since it was a utility cabinet, I made it from the cheapest materials possible, standard construction grade white pine. The multi-colored finish was my wife's contribution.



On the bench, it is basic mission style, with perhaps the exception of the through tenon on the stretcher. It is a compromise between mission style chairs and a dining room table with a trestle base, which has a similar through tenon (intended to imitate a Japanese joinery technique.