Cutting a Spruce Billet for Blocks, Bass bar, and a Top Plate

[Sean Couch]

For my third violin, I have a spruce billet that is sized for a viola. Can I get corner blocks, bass bars, and a 2 piece plate from this one wedge?

The billet is 460mm long, 144mm tall, 51mm thick at the bottom, and 22mm thick at the top. The grain lines on the 51mm side are a bit less than 1mm apart and on the 22mm side they are about 1.5 to 2mm apart. The specific gravity of the spruce was listed at 0.37, but I have not yet confirmed the density.

In my mind, I should be able to get a few bass bars, a set of blocks, and the two wedges that I need to make the belly plate out of this piece of spruce. What is the best way to process this billet to maximize the yield of usable bits? Should I cut the bass bar(s) from the 22mm side or the 51mm side? Is using the same billet for the plate, bass bar, and block a good idea or not?

My first inclination is to make a cut on the 460mm length and reduce it to 380 ish mm and use that 80mm bit for the blocks. The form for #3 should result in a body length of about 355mm. Then saw one or two 7mm wide chunks off the 51mm bottom (finer grain than the 22mm side) for a couple bass bars. The left over billet would then be cut in half and used for the 2 piece plate.

I don’t want to get too greedy and screw things up so I am looking for some advice on the best way to process the billet.

 

Edited to add a picture:

[Evan Smith]

It would probably help if you would throw up the picture with the measurements of the billet.
Trying to visualize all of that and the numbers in the billet, and on the billet, and the stars in the sky, as the moon flies by is giving me great mental anguish.

 Or just patiently wait, and wait

[HoGo]

I have a large stash of maple I cut into oversize billets years ago and try to get as much as possible out of that. My habit is look around the piece for any possible defects (tiniest pin knots or anything merely suspicious) and then trace parts from templates directly on the billet to see if I can get few plates and an extra neck or do few necks and one plate etc...

I would check the wood in and out for any defects - there may be hidden checks or even hint of pitch pocket that may show inside (been there). Body blocks can be made out of any spruce from lumber yard but if you trim your piece before you open the wedge, you may find a surprise right in the wrong place, without trimming you might just be able to move your template a bit... You can still cut a bar or two from the thicker edge of the wedge half.

Another thing to consider is how well does your bandsaw works, I had some problems with blade wandering (dull blade or low tension?) inside the cut (you don't see that during cutting) and making one of the wedges thinner than anticipated. If you have that extra wood around you still may be able to use it.

[Don Noon]

12 hours ago, Sean Couch said:

My first inclination is to make a cut on the 460mm length and reduce it to 380 ish mm and use that 80mm bit for the blocks.

My inclination would be to carefully draw up how the archings would fit into what you have left.

The biggest concern with cutting off the thick lower part for blocks would be that the upper part is too thin.  If you allow for the bandsaw cut and planing allowance, you'd only have 10 mm thickness at the top edge. You also don't mention how thick the billet is at the outer (lateral) edge, which matters since the critical thickness to accommodate the arching is NOT on the centerline.

Lay it all out before cutting.

 

[HoGo]

He mentioned 51 and 22 mm thicknesses so the thinner end is still plenty thick for resawing. if he cuts away lets say 25mm off the thicker side he'll still have ~45 mm at the thicker end.

I'd add that if the billet is resawn there may be some twist in the piece and the twist is always more severe towards center of tree (i.e. towards the thinner edge of wedge) and I'd like to have straightest grain near center of plate.

[Sean Couch]

I haven't had a chance to read through all the replies, but I added a drawing to the initial post that hopefully helps explain things.

 

[Davide Sora]

59 minutes ago, Sean Couch said:

I haven't had a chance to read through all the replies, but I added a drawing to the initial post that hopefully helps explain things.

 

You'll need to do your math and decide whether it's worth cutting blocks and bassbars from the billet, based on how many millimeters you'll shave off the cuts and how straight and precise you can cut them. There's always a certain amount of risk involved. The only thing I'd do differently, assuming the billet is free of defects, is to cut two strips for the blocks, one on each side. This is to avoid having the actual plate too close to the ends, due to potential cracks that could develop in those areas during seasoning. I would definitely clean the two endgrains well with the plane, to see if there are any cracks, and I would do the calculations on this "clean" length.

[Don Noon]

Before the diagrams were posted, I assumed 22m at the "top" was at the top of the violin, i.e. a non-uniform wedge.

As shown, there should be plenty of margin for getting blocks from the cutoffs, and bass bars from the other section, and still have plenty for a violin.  If, as David says, the billet is defect-free.

[Sean Couch]

Right on, thanks everyone for all the tips. I will give the billet a good inspection to look for any defects and clean the ends with a plane to make sure there aren’t any checks. 

My initial thought, since it is a viola sized block, is that it would be a shame to waste a bunch of the billet and to try and maximize what I can get out of it. However, I do understand the concerns mentioned above.

I may give up on the idea of trying to get the corner and top blocks out of this piece and take the conservative route and just go for the plate wedges and a couple of bass bars. That should be fairly easy to do with minimal risk and buying some spruce or willow block wood is pretty cheap. A heck of a lot cheaper than a new billet.

I do have some bass wood carving blocks laying around, but the little bit of research I did seems to show that bass wood is not optimal. I don’t know where the bass wood came from, but I would assume China. I got it off of Amazon quite a while ago for a non violin related project.

[nathan slobodkin]

Hogo has given some great advice here. I would definitely make sure you get the best top plate possible out of the billet first then you should easily get a bass bar or two and then cut blocks if you have enough left over which you will if everything else goes well. With as much length as you have you might be OK to cut one slice off one end just long enough for blocks before resawing if you need to.

A couple of  suggestions regarding resawing on the band saw:

Cupping or wandering cuts are due to either a dull blade or more likely a blade which is not clearing saw dust properly. If you are using a small saw such as a 14” Rockwell I would not use a “resaw” blade. The extra width creates too much drag for the small motor causing the blade to be pushed through the cut rather than pulled which makes the blade bend in the cut leading to cupping. A Regular 1/4” or 5/16” hook or skip tooth blade will not drag and will clear the dust much better. 
 

Also check the beginning of the cut carefully to make sure the resawing cut is perfectly centered and marked on both the top and bottom of the billet before proceeding with the cut and then feed the billet slowly watching the line and correcting even the slightest deviation before advancing the feed. The slow cut allows the blade to clear the dust properly.

Remember that there will usually be a bias to the blade which will make it cut at a slight angle (lead) which you should not try to fight but let the saw cut as it wants to.

[Don Noon]

10 hours ago, nathan slobodkin said:

If you are using a small saw such as a 14” Rockwell I would not use a “resaw” blade. The extra width creates too much drag for the small motor causing the blade to be pushed through the cut rather than pulled which makes the blade bend in the cut leading to cupping. A Regular 1/4” or 5/16” hook or skip tooth blade will not drag and will clear the dust much better. 

I use "Wood Slicer" blades from Highland Woodworking on my 14" Delta, and they work great (although for most resawing I use my 24" Agazzani).

[Sean Couch]

I never thought much about my bandsaw blades until Hogo and Nathan brought it up. I have two wood cutting blades. One is a 10 tooth/inch with raker teeth and the other is a 6 tooth/inch with positive claw teeth. Neither of them would work well to cut the billet in the 144mm dimension. Both are Timberwolf blades and my max depth of cut is about 40mm with the 6 TPI blade.

The 10 TPI blade works great at roughing out the plate profiles and getting into the throat of the scroll, but I will have to get a new blade to make the cut on the billet. I have a 14” Wilton and remember the 6 TPI blade working well on ripping 2x4’s in half. That was cutting the 1.5” dimension. The cuts were nice, but I don’t think it could handle anything much thicker. The boards were still a bit wet, so that didn’t help either.

I was looking at Timberwolf’s variable positive claw blades last night. The blade from Highland that Don mentioned is almost identical to the one I was looking at from Timberwolf. It’s great to have options. It looks like the wood slicer blade has a thinner kerf than the Timberwolf blade, so I might go with that one.

[Don Noon]

1 hour ago, Sean Couch said:

It looks like the wood slicer blade has a thinner kerf than the Timberwolf blade, so I might go with that one.

I have the 1/2" wide 3-4 tpi variable pitch Wood Slicer on my 14" machine, and here's a test resaw at maximum capacity.  The wood is 5 1/4" tall (turned 90 degrees for the photo) and it's some kind of softwood cut from the pallet that my new milling machine came on (more about that eventually).

The cut is pretty flat, but you can see from the diagonal pattern that there were times that the blade started singing, even with the variable pitch tooth spacing.  The 3/4" wide Wood Slicer wasn't an option when I bought this blade; I probably would have gone for that one.

[Sean Couch]

That cut looks good enough for me. I just checked at Highland and Timberwolf and it looks like I can’t get the 3/4” 3-4 TPI wide blade for my 92.5” blade length. Highland has the 3/4” starting at a 93.5” blade length and Timberwolf drops down to a 2-3 TPI and a much wider kerf on their 3/4” blades. I might be able to get the 3/4” Wood Slicer to tension up correctly on my saw. It isn’t a huge difference but I have never tried to rig up that situation before. lol. 

[Don Noon]

1 hour ago, Sean Couch said:

... my 92.5” blade length. 

93.5" is pretty much the universal standard for 14" bandsaws.  I'd check your machine with a tape measure at the maximum and adjustments to see what range you really have.  My Delta looks like it has 1.5" adjustment in the top wheel, or 3" variation in blade length.  I haven't actually measured it, though.

I also have a 3/4" resaw blade for my Delta, .024" blade thickness and very wide kerf (carbide tips).  The machine doesn't seem too happy about tensioning up such a beefy blade, but it manages.  I had the blade re-sharpened, so it doesn't get bothered by the quantity of wood it has to remove.

[Shunyata]

I have a 104” Rikon that gets unhappy with a 3/4” resaw blade… so I know what you mean.

[HoGo]

I've managed to get good results with ordinary steel blades (I believe the blades I use are 9 and 13 teeth 1/2"wide) on 14" Delta clone. You just have to keep eye on sharpness of bladeand feed the wood only as fast as the saw wants without undue pressure. Spruce is one of the easiest woods to cut. Few weeks ago I sliced brick sized piece of pear into headstock veneers, slow and steady feed and good saw preparation and setup before work resulted in pretty nice straight cuts.

[Sean Couch]

I will have to do some practice runs on some lumber yard SPF scraps with the blades I have. The 10 TPI blade I bought this past March and has only been used on violin #2. The 6 TPI blade is a year and half old. I bought that one for my first violin, but it is has also my go to blade for general wood cutting when the chop saw or table saw won’t do. I know the finer toothed blade is still quite sharp, I am not so sure about the 6 TPI blade. I ripped a bunch of 2x4’s with it while screening in the back porch earlier this year.

I dug out my owners manual for my 14” Wilton and it does say 92.5” for the blade length. I also have my original sales receipt and the blade that I bought when I bought the saw, back in February of 2003, was a 93” blade. I know that blade had no issues on the saw and it was used/abused with cutting metal when I was forging pattern welded knives. I don’t think the 93.5” would be a problem, but I will double check before I order a new blade.

I don’t mind buying another blade, but if what I have now will do a good job, then I will pinch my pennies. I was rummaging through my violin scraps and found a chunk of spruce block wood that I forgot I had. There is probably enough to make blocks for 2 or 3 more violins. It is probably Adirondack Red Spruce as it came from Old Standard Wood in Missouri.

I looked over the billet and planed the ends and did not see any checks or other defects. I like Davide’s idea about cutting the block wood off of each end. My current plan is to cut 40mm (or so) off each end of the billet, then resaw the billet to make the two wedges. If there are any visible defects, hopefully I can work around them. If it is defect free, I will cut some bass bars from the thicker side of each wedge. Even if I can’t manage to get any usable block wood from the billet, I will fall back to the red spruce I currently have.

[nathan slobodkin]

17 hours ago, Don Noon said:

I use "Wood Slicer" blades from Highland Woodworking on my 14" Delta, and they work great (although for most resawing I use my 24" Agazzani).

My own experience with those blades was not good. I processed maple logs with the narrow blades and had much better results than with wider, thin kerf  blades. I also use the 1/4” hook blades to slice 3 mm cello ribs with no problems.

[Sean Couch]

I ran tests on some 1x4 lumber scraps that were sent through the saw so that the cut was 5 to 6 inches tall. The 3/16” 10 TPI blade produced too much cupping/bowing. The 1/2” 6 TPI blade did quite well. No cupping and a pretty clean, straight cut. I was surprised that it did so well. I may still order the 1/2” variable toothed blade as my current 1/2” blade is definitely not as sharp as the newer 3/16” blade.

One picture showing the straightness of the cut, and the other trying to show the cut quality.