Oh, Peter!
Oh, Peter!
Timothy F. Lewis
"If brains was lard, that boy couldn't grease a very big skillet" J.D. Clampett
Here it is. It's just made from scrap plywood. The main part of 5/8" sheeting grade plywood. 1/2" sheeting grade ply' is often 4 plies these days, and that is not balanced construction, so it warps. This is 5 plies, balanced construction so it stays flatter. The 1/4" scraps that surround the plate in the cradle are attached with screws only. If they were glued, that would cause an imbalance and the cradle would probably warp. Also, if I cut into it and ruin a piece, I can replace it by simply screwing on another piece.
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
Very good.
John Hamlett
www.hamlettinstruments.com
Thank you!
Very helpful, John. Thanks for your trouble.
I found some time to sharpen a couple of finger planes and do some top carving on a couple of other projects, so I figured I might as well do a little more work on the top of the 'cello while I was set up to carve.
I believer I left off here, rough carved to the bottoms of my depth gauge holes at about 7mm thickness.
I reduced the thickness to about 5.5mm, even thickness across the center of the plate, using a finger plane followed by a scraper. That's the thickness I expect to use for the center of the top (I might thin it more depending on how heavy and stiff it feels after it's graduated).
I used a finger plane to reduce the thickness near the edge to about 3mm.
I scraped away the tool marks...
Then "connected the dots", carving to an even graduation from the thinner edge area to the thicker center area, then scraped away the tool marks.
That's all I'll have time for for a while.
John Hamlett
www.hamlettinstruments.com
How kind of you to share so much of your acquired knowledge John! I don't build but, I do appreciate the myriad little tweaks and errors that make some of you that do are generous enough to share! It makes me look at every mandolin with more and more respect for the time builders have invested in understanding their craft. Strong work all!
Timothy F. Lewis
"If brains was lard, that boy couldn't grease a very big skillet" J.D. Clampett
In post 184 it looks like you're carving the inside of the plate after the outside's been carved. As you carve the inside, do you have anything supporting the outside of the plate (i.e. between your workbench and the plate), or is the plate strong enough by itself to hold up to the stresses of having the inside carved out?
Thanks for your generosity posting all this.
The carving cradle is shown in post #177 (and others), so you can see that the plate is supported all the way around the edge. The rest of the plate (the center part) is not directly supported during carving, but it is plenty strong for carving in this manner. Any stresses applied by carving are slight, and significantly less than the strings will apply later, if I ever get the chance to finish this thing!
John Hamlett
www.hamlettinstruments.com
Digging this up from the deep archives to say how great this thread was for sharing and information. One of my favorite reads so far on MC.
Did you ever finish it, or maybe starting posting somewhere in another thread?
Thx
Jon
Not finished yet. The future owner had some serious health problems, and the associated serious financial problems, so we sort of put the 'cello project on the back burner. I have done some more work on the 'cello and I have more pictures that I haven't processed for the internet yet. I'll try to post an update soon.
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
Moving ahead with the top, I sanded it also, especially inside where I sanded it all the way to 220 grit to make ready for fitting the bracing. The braces in the picture are simply lengths of spruce cut from a scrap.
First step is to mark for the initial cut for fitting the braces to the top. This pencil stub taped to a small wood scrap is the precision tool that I use to mark the cut line. Just drag the tool along the top and it marks the curve of the top onto the brace.
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
With most of the waste removed, the rest is chalk fitting the braces to the top.
I start with a finger plane...
then scrapers as the fit improves...
then finally some sanding. I use emery boards because they are sort of like little sanding blocks and they help me keep from rolling the edges and rounding the surface of the bottom of the braces.
Last edited by sunburst; Apr-05-2017 at 9:55pm.
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
I like to cap the joint of an X-brace to help with the strength at the joint. In Martin guitars you'll see a linen patch for this purpose, but I like to use a little piece of spruce. In order to glue the cap the brace surface must first be lowered to it's final center height and planed flat and straight for a good glue surface.
Here's the little spruce cap sitting in position and showing a good fit.
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
John Hamlett
www.hamlettinstruments.com
Looks like I neglected to get any shots of the process of gluing the top linings into the rim, but that is done, and here is the process of gluing the top to the rim. I used an assortment of padded clamping cauls, some that I made for an octave mandolin and others that I made for random purposes. I didn't have to make custom cauls for this instrument. Custom cauls would have looked better in the photos, but this assortment worked just fine for a good glue joint.
Hopefully I'll get some shots of gluing the back linings to the rim when that happens. It is the same process as the top linings.
I glued the top to the rim with the rim in the form in order to maintain the proper rim shape.
Here's what it looks like now.
John Hamlett
www.hamlettinstruments.com
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