J. Swenson's Bench

[Joe Swenson]

On 1/3/2017 at 4:08 AM, Jim Bress said:

Great bar clamp Joe!  Why do you think the bar didn't fit at glue up?  Did the clamp set up change the shape of the plate, or did the glue change the shape of the bar?

 

-Jim

Thanks Jim!  Sorry for the delayed reply.  

I'm not sure.  I think the thickness of the glue layer affected the ability to clamp it uniformly.  Both times the thick glue left gaps on the ends.  Once I thinned the glue it went so much more as expected. 

[Joe Swenson]

On 1/3/2017 at 6:41 AM, Mike Spencer said:

Joe,

Nice work on all the documentation you've done on your 'bench'! Of course the fiddle work looks good too!

Thanks!  I never know if I'm putting up too much information.  I figure you can skip if you want. 

Need to post work on the neck and gluing the top on the ribs,  

Trip to North Carolina got in the mix...  

Stay tuned! 

Joe

[Joe Swenson]

Stuff happens...  OK lets try and catch up.   A lot of photos under the bridge since I last posted.  Several things have occured.

1. Tuning the bass bar: Which involved monitoring the M3 and M5 tap tones and the quality of the "ringing" of the top plate as the height and shape fo the bass bar was reduced to the final configuration.
2. Good progress on the neck and scroll:  
3. Straightened my "warped" fingerboard to be used on this cello.
4. Preparing to glue on the top plate onto the ribs.  Which technique to use?

1. Bas Bar tuning.  
I spent some time measuring the tap tones as I trimmed down the bass bar, but my poor documentation skills I did not get photos to go along with the tap tone spectral plots.  
Suffice to say with the full bass bar height and thickness, the tap tones are too high compared to before the F-Holes were cut, and die out quickly.  The top doesn't ring properly.  As you get closer to the final bass bar height and profile dimensions, the ringing becomes clearer and more sustained. And closer to what you started out with prior to cutting the F-holes.

 

[Joe Swenson]

Skipping to #4.. Preparing to glue the top plate.

Next step was to check the rib alignment and glue in cross supports to hold the ribs at the proper dimensions for gluing on the top plate.

One side of the ribs aligns nicely while the other side is sprung out a little.  Easily lined up with a push of the finger.

Need to line up and clamp both sides then attach some cross pieces to stabilize the ribs dimensions for gluing. My local friend who is also a Luthier (for much longer than I have been)  leaves the ribs on the form when gluing on his first plate - in his case the back plate.  I will do the top plate first allowing me to clamp the neck much more securely before gluing on the back plate.

 

Cross diagonal strips provide additional stability and strength.  The whole center section can still move as a unit.  So by lining up and clamping one side, the other side can be unclamped and glued with the alignment being correct.

Alignment looks quite good now.  Ready to set up the clamps and get ready to glue.

 

[Joe Swenson]

OK as promised.  Dusting off the Bench thread.

Everything is ready to go. The body is ready to be glued.  What I've found is I prefer to  attach the top of the instrument to the ribs, then setting the neck, and then gluing on the back.  I feel its a much more reliable  process to fit the neck and clamp it with an open back than trying to set a neck on a closed box. The top glued to the ribs provides a rigid enough structure to reliably set the neck and fingerboard projections.

While the ribs are free we'll first drill the endpin hole.

 

Once the endpin hole is done we're ready to glue on the top. The surfaces are coated with hide glue. Then the plate is attached and a palette knife dipped in hot water is slid in the seam to remelt the glue and then clamped.  I started at the corner blocks and in the C bout first. Then worked into the upper and lower bouts.

Next we'll turn our attention to the neck and scroll... Following that is the neck setting procedure.

[Ken_N]

That is an interesting way to glue Joe.  The temporary supports in the center is a good idea, if you don't have the form inside.  I'm drawing up a Rogeri violin, and the Vieuxtemps Del Jesu.  They are both based on a Grand Amati form.  The central area encircled by the corners is exactly the same on them.  They are right on center.  The Rogeri radius through the corners is very slightly longer, but you can see that they wanted the corners where they wanted them. 

I never thought of putting the plate that I was gluing on the bottom.  But it seems like it is easier to see everything that way.  You could see a line that you drew on to mark the linings on the inside, and see the overhang too. Great idea. I made my spool clamp heads long enough so the instrument would sit on the clamp heads, and not the plate, so they would work.  I'd have to make twice as many, and get longer bolts for a cello though.

[Joe Swenson]

1 hour ago, Ken_N said:

That is an interesting way to glue Joe.  The temporary supports in the center is a good idea, if you don't have the form inside.  I'm drawing up a Rogeri violin, and the Vieuxtemps Del Jesu.  They are both based on a Grand Amati form.  The central area encircled by the corners is exactly the same on them.  They are right on center.  The Rogeri radius through the corners is very slightly longer, but you can see that they wanted the corners where they wanted them. 

I never thought of putting the plate that I was gluing on the bottom.  But it seems like it is easier to see everything that way.  You could see a line that you drew on to mark the linings on the inside, and see the overhang too. Great idea. I made my spool clamp heads long enough so the instrument would sit on the clamp heads, and not the plate, so they would work.  I'd have to make twice as many, and get longer bolts for a cello though.

Thanks for pointing that out Ken. This internal frame was the only option since I had no choice but to take the ribs off the form due the way I built the form. 

Might as well post it here.  I redid my cello form for Cello #2 . I may need to consider further modifying my form so that I can glue the top plate on the ribs while still on the form and easily remove the form plates. I didn't have much choice on Cello #1 due to the clumsy design of the current form employed. 

I have modified the form to be lighter and "collapsible" but I'm still a little concerned about removing the form if I "do the right thing" and glue the top on the ribs while the ribs are still on the form. 

Old form (3 solid layers with solid spacer  - H.E.A.V.Y.!!)

New Form. for Cello #2

Removed center layer. Alignment with 3/8" dowels and spools. Held together with six1/4" x 3.5" bolts. Form has lost a lot of weight > 12 lbs..!! 

Plan for new form is to remove dowels and then pull spaces out through center opening and collapse the two layers. Then angle the two layers along the long axis to remove from the ribs after the top has been glued.  That means the neck and bottom block openings have to have enough clearance allow this tilt.

Sound good?

 

 

 

[Joe Swenson]

So onto the neck...

First step is to prepare the neck block with template. Squaring up the fingerboard surface and neck root angle with the fine blade of the table saw.  This saw blade leaves a perfectly smooth clean surface. Gotta love good tools! 

A shim / spacer was glued onto the side of the neck block and planed flat to support the neck block in order to define the fingerboard surface.

Fingerboard surface can be cut now and root angle defined.

Final fine cut is made to define fingerboard surface.

Neck block is prepared and ready to be cut out on the band saw.

[Ken_N]

Sounds like a plan.  I started a cello, but I sawed the back wedge in half, but off center, and I can't get the arch as high as I'd like. I need to find a new back set.  Maybe willow or poplar?  I thought about Sycamore too.  It is a big tree.  My form is similar to yours, but no holes for clamps.  I figured that I would clamp right on the blocks.  I just looked at it, and I put dowel holes in for the corners. Ok.  

I designed it with a belly that is way bigger than the back. 740 over the block on the front, and 720 on the back. The width is tapered too, but not much in the middle.  Guadagnini on steroids?    So since the back is so much smaller; it SHOULD just pop out the top with the back glued on.  That's the plan anyway.  The blocks are glued to REAL wood in between the junk composite shelving I got for something like $2 a shelf at Menard's.  

I wonder about the spruce on the belly.  I could bend the cutoffs very easily crossgrain with my fingers.  Keep it thick?  God for new spruce too?

That is one nice bandsaw extension.

 

[Joe Swenson]

Cutting out the scroll and neck on the bandsaw. A new blade is required every time I've had to cut a significant piece of maple. You can see the burns n the maple as the blade becomes dull.

 

Cleaned up the  edges with a rasp. Ready to apply the template to drill the pilot peg holes

Paper template is printed out to lay out the peg holes and volutes.

[Joe Swenson]

Laying out the volutes and peg holes

A Forstner bit is used to align the drill with the pilot hole location.  Standard drill used to drill the pilot hole.

Done. Ready to lay out volute templates

[Joe Swenson]

Laying out the volute templates.

Ready to start cutting... (more later...)

[Joe Swenson]

Be prepared! Lots of pics of carving the neck and scroll. Mostly just shows the technique. The first curve of the volutes is from a paper template. The second and third curves are drawn by hand.  It's important not to undercut the walls of the volutes. Initially the faces of the volutes are cut basically flat. The shaping and scooping is done last after the spiral shape of the volute cylinders are finalized and the bevel to the edges is applied. Aside from the pull saw here are the basic tools used.

It's definitely easier carving a cello scroll. The larger size make small mistakes less noticeable.  Roughing out the scroll and volutes. Starting on the bandsaw... 

 

/

[Joe Swenson]

Finalizing the cylinders of the volutes and scroll shape

.

Ready to cut the pegbox opening....

 

 

[Joe Swenson]

On 1/29/2020 at 10:48 AM, Ken_N said:

Sounds like a plan.  I started a cello, but I sawed the back wedge in half, but off center, and I can't get the arch as high as I'd like. I need to find a new back set.  Maybe willow or poplar?  I thought about Sycamore too.  It is a big tree.  My form is similar to yours, but no holes for clamps.  I figured that I would clamp right on the blocks.  I just looked at it, and I put dowel holes in for the corners. Ok.  

Poplar is popular with cello makers I believe.

On 1/29/2020 at 10:48 AM, Ken_N said:

I wonder about the spruce on the belly.  I could bend the cutoffs very easily crossgrain with my fingers.  Keep it thick?  God for new spruce too?

I'm not following...?? 

On 1/29/2020 at 10:48 AM, Ken_N said:

That is one nice bandsaw extesion....

Thanks!

[Ken_N]

15 hours ago, Joe Swenson said:

I'm not following...?? 

 

 

I could bend some of the extra pieces crossgrain into a half circle.  Bend it like a piece of cardboard.  It would go back, and the belly doesn't seem to be like that because of its shape.  But that REALLY surprised me.  It didn't snap, but it didn't fill me with confidence either.  I don't notice it when I cut it out, and worked the wood; only on the leftovers later.  

I just pulled the belly out, and it does bend fairly easily cross grain.  I guess violin bellies do too, but not as easily.  Laying it on the bench it doesn't push down in the middle at all.  No f holes cut yet.  Maybe I just don't know what it should feel like.  Learning on your own you don't have any reference.

It seems to be in the ballpark.  6-8 mm thick now it is 690 grams.  The ring tone is about 233.  I guess they end up strong, but flexible?  I do like working on the bigger size.  The wood has so much reflectance; one way it is dark, the other it is bright.  When smoothed up it should look very cool. And cellos sound way cooler than violins.  Especially down low.  But like guitars they like to play them too high a lot.   

I started cutting the pegbox mortice out right after cutting the profile, and drilling the cross holes.  Melvin Goldsmith suggested it.  Easy to clamp it tight.  Get most of it out of the way.  When finishing, you only have light paring cuts.  I always hold them in my hand, except for the mortice.  I've never carved one clamped down.   Maybe a cello might need it for roughing?

Your scroll looks nice.  I haven't tackled that yet.  Again, the bigger size seems like it would be easier.

[Joe Swenson]

2 hours ago, Ken_N said:

I could bend some of the extra pieces crossgrain into a half circle.  Bend it like a piece of cardboard.  It would go back, and the belly doesn't seem to be like that because of its shape.  But that REALLY surprised me.  It didn't snap, but it didn't fill me with confidence either.  I don't notice it when I cut it out, and worked the wood; only on the leftovers later.  

I just pulled the belly out, and it does bend fairly easily cross grain.  I guess violin bellies do too, but not as easily.  Laying it on the bench it doesn't push down in the middle at all.  No f holes cut yet.  Maybe I just don't know what it should feel like.  Learning on your own you don't have any reference.

It seems to be in the ballpark.  6-8 mm thick now it is 690 grams.  The ring tone is about 233.  I guess they end up strong, but flexible?  I do like working on the bigger size.  ...

The cross grain stiffness compare to along the grain is always different with spruce.  Much stiffer along the grain direction.  The belly has to support a lot of pressure from the strings so yeah, its not going to push down significantly. 

The model for a spruce top is a uniformly thick plate (~7 mm) with an arching shape of your choosing.  I user the Sergei Muratov arching.  There's a little increase in this thickness near the F-Holes which I actually forgot to do in my cello. So I didn't flute the F-hole wings. 

There are a couple ring tones you can listen for depending where you hold the plate (m3, m5 for example). It's harder to hold in some node locations on a cello since the plates a re so big and heavy.  You're not necessarily looking for a particular tone frequency - which depends upon the spruce (or maple fr the back) stiffness and the mass and thickness of the plates.  You just want a nice sustained ringing that doesn't die away quickly.

I started on my own as well using the Johnson and Courtnall "The Art of Violin Making" book.  Made 2 violins and a viola before attempting the cello. I just discovered  Davide Sora's many violin making videos so I have been spending a lot of time watching them. 

You might say you like working in the larger size until you start carving a maple back! OMG!!!  Head to the gym and start working out now. You'll need the strength!

[Joe Swenson]

A little carving on the neck / scroll area.. (searching for the right term... LOL )

 

[Joe Swenson]

Cutting the pegbox mortise. 

I know now after watching Davide Sora's video to use the flat chisel sooner than later. LOL

Mortise wall thickness changes slightly with depth.

Pegbox mortise finished!

Rough profile cut on remainder of neck.

 

[Jim Bress]

Great pics Joe.  Kind of nice not having to wait for to finish the next step.

[Joe Swenson]

7 minutes ago, Jim Bress said:

Great pics Joe.  Kind of nice not having to wait for to finish the next step.

Thanks Jim!

[Joe Swenson]

More neck carving was done and the chamfer has been applied. A boundary line was drawn and a 45 deg chamfer was cut up to that line.  The face of the volutes should have been better defined before this step as a few spots the chamfer was a little uneven.  That was worked out as the fluting was cut.

...

 

[Joe Swenson]

Last steps carving the scroll... Embarrassed to say the total time from starting cutting out the neck from the maple block (12/16/2016) to finishing the scroll carving (1/5/2018) was nearly 13 months!! When the entire cello took 4 years I guess that is consistent. LOL 

This will be cleaned up with an oval scraper. On to the front of the scroll...

Scraped smooth. Finished! Pretty happy with the results.

More fine detailed cleaning up of tool marks was done in the coming months as I worked on other things. Your eye catches things anew after leaving things for a period of time.

 

 

 

[Joe Swenson]

Continuing on...

Something which isn't part of the usual cello build...I bought this gorgeous round cello fingerboard (slightly damaged - small inconsequential chip which I glued back in place) at the VSA convention in 2015(?). Some of the blackest ebony I've seen... After having it in the workshop for a couple of years and went to use it I found it had warped - twisted slightly. Since this fingerboard was already close to the proper thickness I couldn't just plane it flat again or there would not be enough thickness for a properly proportioned neck.  So using a heat  gun and some proper twisting torque on the fingerboard I got it straightened out.  It actually took three heating sessions, the second one closer to the end of the fingerboard, and a third at the wide end to remove all of the twist...  Once straightened again, the underside of the fingerboard was sanded and scraped flat.  Good to go again, flat on the maple neck gluing surface.

You can see the twist angle in the 1x2... Applying heat with foil to distribute the heat and torque on the 1x2 the twist is corrected.

Still some twit at the end so the process is repeated.

Little more complicated on the wide end. Uneven clamping with a spacer on one side puts the needed torque.

Pretty near flat and with a little sanding and scraping its flat again.

[Joe Swenson]

Before shaping the remainder of the neck. I want to get the peg holes reamed out. I found that using the drill press as a guide for doing the bulk of reaming makes the final result quite reliable.  I've been using this ever since the first attempt not realizing how much a reamer can wander as the peg hole enlarges.