Saw sharpening/deep ripping technique

[profchris]

I am ripping a 3/4 inch mahogany board, 14 inches wide, into two thinner 14 inch boards. A brace of one-piece guitar backs, in case you wonder why. The board is ex a Victorian wardrobe, so probably Central American.

I'm using an old, no-name 26 inch handsaw which is 5tpi and I've sharpened rip. After sharpening the points of the teeth are sharp enough to nick skin, but after 10 mins sawing they are very noticeably less sharp. Still cutting though, but gently rather than aggressively.

Questions:

1. Is this dulling just normal? Or do I have a duff saw? If not,

2. Is it normal for the technique I'm using? I'm effectively sawing mainly end grain because I stand the board almost vertical, end grain up, and saw alternately from opposite corners at around 30 degrees to the horizontal. My sawdust is finer than when I cut at 45 degrees plus when normal ripping, but if I increase the angle I risk not cutting straight across.

3. I know I could do with fewer tpi, and one day will attempt that - what would be a good tpi number for deep ripping (4 inches up to 14). And what saw file size will I need?

For now I will persevere and get the cut made, but I'd like to be better set up, if possible, for next time.

 

[thick_mike]

Do the teeth feel blunt? It may well be that the teeth are still sharp.

If you are sawing at a 30 degree angle to the end grain, then as you start your cut you are cutting only a few mm length and progress will be quick. As your cut progresses, the length of your cut increases and the progress through the board will decrease. Also, as the thength of the cut increases you may get some teeth in the middle of the cut that never emerge from the kerf and so cannot release the sawdust from the gullets. This makes them cut inefficiently.

Both of these things will tend to slow progress.

Also, rip cutting is bloody hard work and your arm is probably slowing down!

 

[John15]

I believe certain Mahoganies can have inclusions (silica?) which are tough on saw blades.

John

 

[AndyT]

Most of my limited experience of this is here topic100654.html.
I found that a 3 1/2 tpi saw was good, on cuts much shallower than yours, in softer wood.

I admire your persistence!

 

[custard]

Your saw is way too fine, on a 14" deep cut the gullets between the teeth will be clogged up with compressed saw dust after less than half that distance of tooth travel, effectively preventing any more cutting and making the saw very liable to wander off-line.

The benefit of a coarser saw for deep ripping has nothing to do with the great big teeth, it's the great big gullets which serve as reservoirs for collecting the waste! That's why the large two man saws for ripping wet logs have those massive great perpendicular gullets far exceeding their tooth size.

On a bandsaw you can reproduce the benefit of big gullets by adopting a very slow feed rate, the teeth emerge at the bottom of the cut and drop their load of saw dust from the gullets, but with a hand saw things aren't so easy. You can laboriously withdraw the saw after each stroke, that'll work but it'll turn a big job into the labour of Hercules. What I'd do is break up the 14" cut into three sequential "flats" of about six or seven inches each, an angled entry cut, an angled exit cut, and flat cut across the apex. A 5 tpi is still too fine, but you'll just about pull it off, and more importantly with a 3/4" which board, you'll find you're cutting more accurately. A third option is to rip your 14" wide board into two 7" wide boards, deep rip them separately then edge joint them back together, mucho faff but it'll work.

Good luck!

 

[profchris]

Thank you all - I was concerned that the saw might just not hold an edge to its teeth, so its reassuring that what I'm getting is what was to be expected, i.e. hard work and slow progress! But I knew that before I started.

Particular thanks to Custard for this suggestion:

What I'd do is break up the 14" cut into three sequential "flats" of about six or seven inches each, an angled entry cut, an angled exit cut, and flat cut across the apex. A 5 tpi is still too fine, but you'll just about pull it off, and more importantly with a 3/4" which board, you'll find you're cutting more accurately. A third option is to rip your 14" wide board into two 7" wide boards, deep rip them separately then edge joint them back together, mucho faff but it'll work.

I'll give that a go and report back on how it works. Currently I'm cutting two angled cuts around 9 inches each, one from each side.

I had originally planned to halve the backs and join them, but the wardrobe door is big enough for one-piece backs, and one-piece backs are just ... well, rather cool! And I'm doing this for the fun of making, not for payment, so I can suck up some time just sawing.

I wonder - should I just (for future deep ripping) make myself a frame saw using a piece of bandsaw blade? I can't file deep gullets into the existing saw, even if I go to 3 tpi, but I might find a piece of bandsaw blade somewhere. Hmm, looking on the Tuffsaws site I see various blades for resawing/ripping, though none with extra deep gullets, maybe I should call up and see what can be done.

 

[thick_mike]

I made a framesaw for this very purpose, but found it hard to keep the blade straight. It twisted badly and wandered all over the place due to the blade not being sufficiently tensioned in the frame.

 

[profchris]

I made a framesaw for this very purpose, but found it hard to keep the blade straight. It twisted badly and wandered all over the place due to the blade not being sufficiently tensioned in the frame.

I had in mind something like a piece of M8 threaded rod, slotted and drilled to pin the blade, and using a socket wrench in the nut to tension it. Does that sound up to the job?

I guess the main drawback is the weight of a stout frame. Never any free lunches

 

[Jacob]

I've done this with a similar sized piece, but started by deep cutting all the way round over the top of a TS. Then 4TPI saw. The TS cuts act as a guide. Still hard work though.

 

[bugbear]

I made a framesaw for this very purpose, but found it hard to keep the blade straight. It twisted badly and wandered all over the place due to the blade not being sufficiently tensioned in the frame.

I had in mind something like a piece of M8 threaded rod, slotted and drilled to pin the blade, and using a socket wrench in the nut to tension it. Does that sound up to the job?

I guess the main drawback is the weight of a stout frame. Never any free lunches

IIRC there was a lot of discussion and experiment of this, when Tod (someone)s kerfing plane was fashionable. It formed a pair with a frame saw.

I'll try to search for what people found out.

BugBear

 

[thick_mike]

I made a framesaw for this very purpose, but found it hard to keep the blade straight. It twisted badly and wandered all over the place due to the blade not being sufficiently tensioned in the frame.

I had in mind something like a piece of M8 threaded rod, slotted and drilled to pin the blade, and using a socket wrench in the nut to tension it. Does that sound up to the job?

I guess the main drawback is the weight of a stout frame. Never any free lunches

I used a very similar idea. My main problem was that I used an unsuitable blade. I had a bow saw blade which probably had the wrong tooth profile. You might do better with a section of bandsaw blade, but you would be much better off with a proper framesaw blade. For example...

https://www.fine-tools.com/gestell.html

 

[bugbear]

IIRC there was a lot of discussion and experiment of this, when Tod (someone)s kerfing plane was fashionable. It formed a pair with a frame saw.

I'll try to search for what people found out.

BugBear

Tom Fidgen.

Anyway, best page I found was this;

http://www.renaissancewoodworker.com/wh ... frame-saw/

BugBear

 

[custard]

Many years ago I knew an antique restorer who sawed his own veneers using a frame saw. I've only a dim memory of it, but I'm sure his wasn't the type of frame saw in Bugbear's avatar, instead of one cross bar it had two, one at each end so the frame formed a long rectangle. He held it flat, i.e. horizontal, and used two hands to saw, with the workpiece vertical so that the saw frame passed down over the workpiece as he progressed.

Incidentally, the problem with many commercial veneers isn't just their thickness (they normally come in at only 0.5-0.6mm), another issue is the way that they're cut. The log is boiled for many hours to make it soft and then the veneer is peeled or sliced off with a knife, on harder timbers the boiling process is rarely enough, so you often find fractures and damage to the surface. If the veneer is peeled off (like with a pencil sharpener) then the grain pattern just looks a bit odd to my eye. Consequently I generally saw my own veneers, although with a bandsaw rather than by hand. The other huge advantage of sawing your own veneers is that you then have a supply of solid wood from the same board with which to make lippings, legs, and other solid components; which all colour match perfectly.

 

[PAC1]

Many years ago I knew an antique restorer who sawed his own veneers using a frame saw. I've only a dim memory of it, but I'm sure his wasn't the type of frame saw in Bugbear's avatar, instead of one cross bar it had two, one at each end so the frame formed a long rectangle. He held it flat, i.e. horizontal, and used two hands to saw, with the workpiece vertical so that the saw frame passed down over the workpiece as he progressed. .

I think there is a picture of such a bow saw in Tag Frid's book

 

[Sheffield Tony]

Many years ago I knew an antique restorer who sawed his own veneers using a frame saw. I've only a dim memory of it, but I'm sure his wasn't the type of frame saw in Bugbear's avatar, instead of one cross bar it had two, one at each end so the frame formed a long rectangle. He held it flat, i.e. horizontal, and used two hands to saw, with the workpiece vertical so that the saw frame passed down over the

Like this ?
http://www.blackburntools.com/new-tools ... index.html

Looks quite an easy thing to make.

 

[profchris]

My mate Sven of Argapa Ukuleles in Sweden has made himself a kerning saw and frame saw, based on the Fidgen designs, so I'm up to speed on that (apart from the blade - I think he spent quite a lot on his blade, buying from he US, but then he's a tool addict!).

I'm trying Custard's three facet approach, but will probably go for a 4 facet technique (sawing from each side at 45 degrees and 20 degrees, approx). With a board this width it inevitably moves somewhat as the internal stresses are relieved by the sawing, so it pinches the saw a little for the horizontal cut - enough to make that hard work.

I'm getting there in 5 minute bursts - I have the biceps of a wimp and the stamina of a finely tuned couch potato

 

[thick_mike]

If the kerf tends to close and make the blade stuck, use small wedges to keep the cut open. And a little candle wax on the sides of the blade will help too.

 

[whiskywill]

I had originally planned to halve the backs and join them, but the wardrobe door is big enough for one-piece backs, and one-piece backs are just ... well, rather cool!

Your wood and your choice, but one piece backs always remind me of cheap laminated/plywood guitars.

 

[bugbear]

I had originally planned to halve the backs and join them, but the wardrobe door is big enough for one-piece backs, and one-piece backs are just ... well, rather cool!

Your wood and your choice, but one piece backs always remind me of cheap laminated/plywood guitars.

You must hate 1880's Martins!

BugBear

 

[undergroundhunter]

What I have found with deep ripping is this, if the saw has too many teeth the sawdust builds up in the kerf 1 making the saw inefficient and 2 causing the blade to bow in the cut, this means the saw stops cutting in a straight line making it a lot harder to push the saw and making cleaning up the pieces a lot more work and loosing quite a bit of thickness in the process. The most i have ripped by hand is about 10" width with a 6tpi saw, it was seriously hard work and took a while, I have since acquired a 3tpi 30" saw but havent had chance to use it in anger yet.

Matt