Posts Tagged ‘purfling marker’

Purfling and graduating the back plate

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Purfling and Graduating the Back Plate

Purfling came first, this time.

I decided that I would prefer to purfle first, then graduate, on this plate. Maple is much tougher than spruce, and I wanted maximum mobility as I cut the purfling slot, as well as avoiding any danger to the rest of the indtrument when forcing the purfling into the glue-filled slot. It can require a great deal of pressure.

 

I used the purfling marker to trace out the location of the purfling slot.

I used the purfling marker to trace out the location of the purfling slot.

 

Then I began incising the sides of the slot, and removing the waste wood.

Then I began incising the sides of the slot, and removing the waste wood, with a purfling pick.

I always forget, between instruments, just how tough the European maple is. I always find that I have to take breaks once in a while, and allow my hands to rest.

 

Back purfling slot.

I always find the back purfling to be physically difficult, but it is easier to do clean work.

 

Back purfling slot complete.

Back purfling slot complete.

 

After cutting the slot and removing the waste wood, I double-check the width ans depth of the slot by inserting a scrap of purfling into the slot, and dragging it around the entire slot, so that I know the purfling will fit cleanly.

Then I use a bending iron to bend the purfling, I cut the miters for the “Bee-stings”, and I insert the purfling, dry, to get a perfect fit.

 

Purfling installed dry.

Purfling installed dry.

 

Before I start gluing, I also take time to mark the edge of what will be the “crest” of the edgework, so that I don’t gouge too deeply or too wide, when cutting the channel. After gluing, it is difficult to get the pencil to mark on the wood, if it is either damp or glue-coated.

pencilled-in crest marks.

If you look closely, you can see the pencilled-in crest marks.

 

Finally, I lift out each purfling segment, one at a time, and slip hot hide glue under the purfling, then quickly press the purfling back down into the slot. I use a hard plastic roller to help force the purfling deeply into the slot.

 

The purfling is glued in place

The purfling is glued in place, and I can cut the channel now.

In this case, I chose to work on the graduation, next. I did not get it done, but I am within an hour of completion. Then I can conplete the plate, add the label, remove the mold, and close the corpus.

 

 

Graduation in progress.

Graduation in progress.

I will also complete the channel and the inner edgework, before removing the mold and installing the plate. But it is getting there…

Vacation is a hard time to get things done, because the people take higher priority, and everything eats up the time. (Ah, well…always good to spend time with family.)

 

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Button and Back Purfling

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Button and Back Purfling

Trimming the Button and Heel

When I installed the back plate, the heel had been trimmed flush with the back of the garland, but the upper surface of the heel was still quite irregular, and the upper end of the button was ridiculously oversized. The excess wood made it easy for me to install a clamp, and get the back plate glued on securely. So…when I removed all the clamps, this is what it looked like:

Back plate installed; button and heel not yet trimmed.

Back plate installed; button and heel not yet trimmed.

 

Tools for completion.

Next, I will trim the button and heel, then add purfling, then scrape. These are the tools I will use.

 

Button shape.

This is roughly the shape the button will be, but a little more refined, I hope.

 

Side view of heel and butto

Side view of the heel and the button. The closeness of the camera warps the picture a little.

 

Installing the Purfling

The next thing was to scribe in the purfling slot. I used the purfling marker to scribe the double line exactly 4mm from the outer perimeter of the plate, except the corners, where I used a sharp pencil to sketch the “bee-stings” in by hand. Then I incised the lines all the way around, just barely deepening the lines, so that they are more visible, and a little easier to follow with the blade of my small knife.

Purfling slot lines lightly incised.

Purfling slot lines lightly incised.

 

Then I slice in pass after pass, trying to get the lines deep enough for the purfling I will install. I usually find that, especially on the hard maple, I have to cut the slot in two layers: the first gets about half the depth I want, and the second finishes the slot. Here is the slot at half-depth:

Purfling slot, half-depth.

It looks good, but it is not deep enough.

 

Purfling slot ready for purfling.

Purfling slot ready for purfling.

 

Back purfling installed...glue still wet.

Back purfling installed…glue still wet. 🙂

 

Front view

And the Front!

 

Back to Work!

As most of you know, I had undergone hernia surgery, just after Christmas, and had a 6″ x 8″ polypropylene mesh patch installed in my abdomen. I have been convalescing, and just this week, have finally been feeling better. So…I just received word that I will return to my work at Gunderson, Inc., tomorrow at 6AM. I think I had better call it a day, and try to get some sleep. 3:30AM comes at the same time, every morning, whether I am ready or not. I will get home sometime after 4PM, I expect. Maybe I can jump back in where I left off. 🙂

Tomorrow evening, then, I hope to complete the purfling channel and the outer edgework of both the front and back plates, and begin the final scraping in preparation for varnishing. Any little glitch, regardless of how tiny, will be very visible under the varnish. So this part has to be done with great care.

 

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Home Stretch for the 14-inch Viola

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On the Home Stretch Now!

The 14-inch Viola is getting closer to completion!

When I last posted, the viola was still in the spool clamps. The back plate was installed, but that was as far as I got that night.

Viola in spool clamps

Lots of promise, but not much “grace” in this picture.

 

Spool Clamps Off: Lots of Work to Do, Preparing for Purfling

So…the next step was to remove those clamps, adjust the overhangs as needed, and get on with the purfling. That sounds pretty straightforward, but there is always more to anything than meets the eye.

front view, back plate installed, button needing shaping.

Looks nice, at first glance, but take a look at the neck button (where the back plate overlaps the heel of the neck.)

 

side view viola with unfinished back plate.

Side view of the same state of the viola.

 

Back view viola with unfinished back plate.

Back view: button hidden by my hand. No purfling, and no shaping done.

 

Purfling Groove

I marked the purfling groove, using what is frequently called a “Purfling cutter“, but which is actually a marker. It has two blades that simply lay out the sides of the groove, by scribing them a set distance in from the outer edge…which is why I want the outer edge perfect, before beginning purfling. I have modified my cutter a bit, to make it work more reliably, but the link above shows the type of tool I use. I don’t think I have that brand. I can only use the marker to get within an inch or so of the corners. I lay out the corners by hand, sometimes using a frnch curve to achieve some repeatability.

Afterlaying out the groove in pencil and scribe marks, I incise the lines with a small sharp knife, then pick the waste wood from between the cuts.

Here is the completed groove:

Purfling groove and button complete

Purfling groove complete. Notice that the button is taking shape as well. The neck, too is getting slimmer, and smoother. Lotsa work…

Here is a detail shot of the groove:

Detail of purfling groove.

Detail of the purfling groove.

 

The Purfling, the Channel, and the Finish Work.

Finally I can start cutting and installing the purfling itself. I use a wood purfling, which is very brittle when dry, but bends nicely with a little moisture and a lot of heat. Once the purfling fits correctly, I lift each stip out partway, and insert hot hide glue under it, then force the strip back into the groove. Afterward, I mark the crest of the channel, and cut the channel using a sharp gouge. Finally, I use a tiny plane as well as gouges and scrapers to bring the convex curve of the plate into a fair, smooth agreement with the concave curve of the channel.

The purfling is complete, the channel is cut, and the back curve faired into the channel.

The purfling is complete, the channel is cut, and the back curve faired into the channel.

 

Purfling detail

Purfling detail: look closely, and you can see the edge-crest line in pencil.

 

side vies of viola.

It is a fairly high-ribbed viola: 35mm. I think it will sound good.

And, it is looking more and more like a viola!

Viola nearly complete

On the Home Stretch!

 

What is next? Edgework, and final scraping; coffee stain, mineral ground, sealer, and varnish…and then fittings and set-up. (The outer edgework is not even begun on the back plate.)

This is definitely as far as I am going tonight, though…. Getting too tired.

 

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5 String Fiddle Progress Report #6: Front Plate Installation and Purfling

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Five String Fiddle Front Plate Installation

Back to Work!

It was fun working on the Sawmill, and just as we got that done our daughter came home (from Switzerland) for a visit, so, between that and all the overtime at work (teaching print-reading classes), it has been hard to get going again, but the fiddle has been patiently waiting on the dinig room table for me to get back to work.

Installing the Front Plate

I levelled the garland by scrubbing it back and forth on a sanding board, then aligned the plate on the garland and clamped it with spool clamps. After heating up the glue, I removed a few clamps at a time and inserted the glue with a thin pallete-knife, and re-applied the clamps. In this way, I can work my way around the perimeter, accurately and easily gluing the plate in place without fear that the glue will gel before I can get the plate clamped in place.

front plate with garland

Front plate glued in place

Ready to begin Purfling

The purfling is an inlay that is partially decorative, and to some degree a protection against cracks and splits– an edge reinforcement. There are some (usually very cheap) instruments that have the purfling simply painted on, so that it only looks good, but has no other function. They are usually seen as sub-standard, though, and I will not consider making an instrument that way…so, here is the beginning point: the purfling marker. Two blades set apart by the exact thickness of the purfling to be inlaid, and the distance from the edge set, as well.

Purfling marker

Purfling marker

Some people call this a purfling cutter, but it really does not workwell if you try to use it to cut the slot. I mark the slot with this tool and then cut the slot with a sharp, thin knife. In use, the purfling marker should be held exactly perpendicular to the plate, and tightly against the plate edge.

Purfling marker in use.

Purfling marker in use: see the double lines.

The purfling marker will not complete the corners, and they are fairly critical to the overall look, so I carefully sketch them in with a very sharp pencil.

Sketching the corners

Sketching the corners

Cutting the Purfling Slot

I usually use an X-acto knife to cut the slot, and pick the center out with one of several tools made for that purpose.

Purfling tools.

Purfling tools.

The first trip around the plate it is important to go lightly but very accurately, so that I am barely deepening the marks left by the purfling marker: after that I can cut more deeply.

Incising the Purfling Slot

Incising the Purfling Slot

Cleaning the Purfling Slot

After I am satisfied that the cuts are the correct depth all the way around, I carefully pick out the center of the slot and clean the slot, using a purfling pick. I have some that I made myself, but this one was given to me by Jake Jelley, and it works very well.

Purfling Pick in Use

Purfling Pick in Use

Ready to Install Purfling

Ready to Install Purfling

Installing the Purfling

Some people make their own purfling…maybe I will try it someday, but for now, I buy mine in three-ply strips. The strips are too brittle to bend, so I use a bending iron to make them flexible and to bend them to the correct curvature for the tight corners.

Purfling strips with prepared frot plate

Purfling strips with prepared front plate

 

I try to install the C-bout purfling first, then force the mitered ends of the upper and lower bout purfling against the mitered ends of the c-bout purfling. It takes practice to get good at this: I do not claim to have “arrived”. But it does seem to be getting easier. (I read the other day that someone asked Pablo Casals why, at 93 years of age, he was still practicing the cello for three hours a day. He said, “I think I am seeing some improvement!”) (Good one, Maestro!)

C-bout Purfling installed

C-bout Purfling installed dry

Then I install the rest of the purfling strips: I want the slots to fit snugly, but not so tight that I will struggle to install them once I apply the hide glue.

Purfling installed dry.

All Purfling installed dry. Spliced in some places, but after gluing the splices will be invisible.

Gluing and Trimming the Purfling

I lift each section up out of the slot, one at a time (tilting them, so as to try to leave the mitered ends in their places), and use the palette knife to slip thin hide glue into the slot, then press the purfling back into the slot, all the way down. I use a roller made for installing the rubber trim around window screens to force the purfling all the way home. The glue squeezes its way into the mitered corners, and secured them. The plastic roller is easy to clean afterward with hot water.

Once the purfling is glued in place, I mark a line around the margin of the plate, using a compass, with the pencil set to about 1.6mm (1/16″ or so), so that I have a guide to follow as I cut the “channel” (trimming the purfling below the surface into which it has been glued.) I want the wood surface and the purfling to make a smooth curve that begins near the edge of the plate, cycles down through the purfling, and sweeps back up to join the curve of the violin plate. I carve the channel with a gouge, then scrape to complete the curves. The faint pencil guide line can be barely seen in this photo.

Trimming the purfling and cutting the channel

Trimming the purfling and cutting the channel.

And there is the finished work, ready for the next step.

Completed Purfling.

All the purfling is trimmed, the channel is cut, and the scraping is complete.

The outer edgework will be completed after I install the neck. I used to wait and install the neck last, but I eventually decided that I prefer to install the neck and fingerboard while the front plate and rib garland are still on the mold, then trim the heel of the neck to be in plane with the back of the rib garland so that the back plate can be installed last. But that is a subject for another post….

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Cello Back freshly purfled

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One-piece Cello back purfling complete.

Narrow (violin-style) purfling, like the original

Today I completed the back plate purfling. Though this is a cello, I purfled it with violin-style purfling, as it was pointed out to me by Jacobus van Soelen that the original instrument (1712 Davidov Stradivarius) had narrow purfling, like a violin, not the wide purfling I used on my first cello (and which I actually like to use on violins and violas, as well.) I just like the eye-catching appeal of the larger purfling as a rule. In this particular case, I must concede that the wood is so beautiful that it really does not need additional “eye-candy”.

The job starts with layout and measuring

Last night I laid out the corners, and marked the whole purfling channel using a purfling marker (sometimes called a purfling cutter— but I only use it for marking– I use a knife to actually cut out the slot for the purfling).

Then cutting and fitting

This morning I incised the whole purfling slot, using a small, home-made knife, and then cleaned the waste wood out of it with a purfling pick.

While I fitted purfling into the slot, and carefully fitted the corner miters, the glue-pot was heating up.

Gluing the purfling

When all the purfling seemed to fit correctly, I tipped each center-bout purfling strip up out of its respective slot, so that it pivoted up and out on the two corner miters, but left the ends in the slots, unmoved. I slipped hot hide-glue (quite thin) into the slot, using a palette knife, brushed hot water to flow the glue, and pressed the purfling strip back into the slot, forcing it deep into the groove with a special tool. (Sometimes I use my purfling pick for that job. Today I remembered that I have a plastic wheel on a sturdy handle,  actually designed for forcing the rubber trim into screen window frames. It worked perfectly. :-)) Then I repeated the above process for the upper and lower bouts.

If I start toward the middle of a section of purfling, and work toward the ends, the glue is forced along under the purfling, and squirts out along the edges and, finally, out the ends, and the miters. The result is that all of the piece has adequate glue, even if some spots had been a little skimpy. Then I brushed more hot water to re-flow the glue, and wiped off the excess with a rag.

So– here is the completed back, ready for final arching, and for having the edge channel cut, etc. It will look pretty rough until the gouge slices along the channel, and trims that excess glue and damaged fibers off the top of the purfling strip. Then it will look very nice. (Purfling isn’t only for looks, by the way, on violins– it also helps stop a split from the edge from moving up into the plate…supposedly.) Anyway, this is how it looks for now:

Completed purfling on one-piece cello back, before carving the channel.

The channel still needs to be cut, but the purfling is complete.

Lower treble cello-back corner, freshly purfled

Lower treble corner, freshly purfled

The next step will be to mark an edge margin all the way around, locating the crest of the finished edges, after which I can use a gouge to carve the channel, and begin the final arching.

But, for today, I have a bow to re-hair, so this is as far as I am going with the cello.

 

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