Thread: Sloped Gullets

I was intending to cut a bunch of dovetails today, for a set of 'utility' drawers for my other half to store her mosaic-making gear in, and with this thread on my mind, decided to try a little ripsaw 'test' myself, to see how well I could control the saw's cutting. The wood I used for the drawer sides is thicker (19mm) than I would chose for similar-sized drawers on furniture pieces, but a) they need to be heavy-duty and b) the material is pine, so I reckoned a bit of beefing-up wouldn't hurt. With the two sides for each of the 3 drawers, I thought I'd use each pair of sides to compare two saws that should be quite different, and give me a clear & (I hoped) consistent result.

So I first grabbed my 'second-best' dovetailer, which is a little larger & heavier than my 'favourite'. This saw has a 1/4" spine, 20 thou plate, and 13 tpi vs a 3/16" spine, 15 thou plate & 15tpi for the smaller saw (front): D-T saws.jpg

I sharpened the larger saw (with one of Bunya Pine's NOS Wiltshires), but didn't touch the smaller as it has only been used very briefly since its last sharpening. Two tpi difference may not sound like much, but it's quite a bit when you hold one up against the other: teeth cf.jpg

Finding #1: Don't use radiata as your test piece! Darned stuff is so varied, with it's large rows of early & late wood, plus variations in hardness for no reasons that I can discern. Exercising the utmost care, I got up to 50% variation in the number of strokes it took to cut to the line, and it didn't improve with practice!: D-T cuts 13tpi.jpg

About 2/3rds of the way through, I gave up recording the numbers because of the extreme variation, but I reckon I would've come out maybe 1 or 2 strokes less per cut on avreage, for the larger saw. I used both saws for crosscutting the shoulders and expected a bit more break-out on the exit side for the 13tpi (I wouldn't normally choose a 13tpi saw for crosscutting), but the difference was minimal. The real surprise here (for me) was that the differences between the saws were so small, I expected them to be greater since one saw is heavier, thicker & has larger teeth: 13tpi.jpg 15tpi.jpg

So Paul, whilst not a test of sloped vs non-sloped gullets, I think my little 'experiment' emphasises the difficulties in comparing saws, even when you expect to find quite appreciable differences. When you are trying to quantify subtle differences, the problems will be compounded, methinks. Some day, I might try to find if it was weight or tooth size or slightly longer stroke (the larger saw is about 25mm longer, but I tried to keep the strokes the same length for both saws) that contributed to the observed difference, but one thing's for sure, I will try to choose a much more homogenous wood as my test-piece!

All good fun..
Cheers,

Ian

Clearly we have quite a task ahead of us. Note the use of "we" which is a tactic I adopt when the outcome is unclear and I be covered in the proverbial instead of glory .

The trick, which is easier said than done, is to minimise the variables. It is a little like the old days when you could work on your car when it broke down. I would change half a dozen things, fix the problem, but not know which change had made the difference.

I don't think I will be using Radiata pine. I will probably select some hardwood without prominent growth rings. Also I can saw fairly closely which again will minimise the possibility of density variance.

I guess it is disappointing that you couldn't really point to any conclusion, but on the positive side pmcgee will be consoled because it was a rip test .

Regards
Paul

Originally Posted by Bushmiller

...The trick, which is easier said than done, is to minimise the variables.....

Actually, Paul, you can only test one variable at a time, so yes, try to minimise them to that!

I wasn't expecting any clear conclusions from my bit of fun, I just had an opportunity to see if I could show a distinct difference in a situation I thought should easily produce one. Typically, my expectations exceeded the outcome.

Originally Posted by Bushmiller

.... on the positive side pmcgee will be consoled because it was a rip test ....

pmcgee? Is he watching us??

Cheers,

Is pmcgee watching? If he isn't it's only because of the time difference. Hold on a tick. I have this feeling he might be further afield than WA, but not sure where I am getting this idea.

I'm still waiting for him to drag out one of those big docking saws. Now they are a saw!

Regards
Paul

Originally Posted by IanW

pmcgee? Is he watching us??

Not creepy at all ...

Originally Posted by IanW

The real surprise here (for me) was that the differences between the saws were so small, I expected them to be greater since one saw is heavier, thicker & has larger teeth: 13tpi.jpg 15tpi.jpg

... I think my little 'experiment' emphasises the difficulties in comparing saws, even when you expect to find quite appreciable differences.

When we might expect to find differences and *don't* find them, we can consider why that might be.
There's a long engineering tradition in amplifying small changes ... usually employing some form of 'leverage' I guess.
So ... a factor here might be the short distance of the cut.
A 200mm cut eg should differentiate further.


I'm intrigued as to whether the most difference would be between styles of teeth in a low tooth pitch like 5ppi, or a finer pitch like 8ppi.

Also whether there would even be a linear (or at least monotonic) change in influence with increasing pitch.
It is conceivable eg that a 4/5ppi and 10/12ppi, the gullets are too large/small to see much effect from style of teeth ... but that there might be a sweet spot around 7/8ppi.
Alternatively it could increasingly or decreasingly influential with rising pitch.


And a third thought - seemingly changing the slope alters at least two characteristics of the teeth ... the shape of the gullet ... and the three-dimensional profile of the teeth. Different teeth might not cut at appreciably different rates, but might remain working effectively for longer.

Cheers,
Paul #300

I never considered sloped gullets to provide any advantage or disadvantage in medium hardwood type work when the bit of the tooth touching the wood has the same geometry as a flat filed saw. I've never had a saw that had a probably with filled gullets in regular dry wood, excepting dovetail saws where I went too far with file too big and left a shallower gullet.

I have filed saws both ways, but generally file flat now just out of laziness. I care more about fleam and rake, and of course, even tooth height. If a saw is rasping, too much fleam. If it's grabby, too much rake or not enough fleam. Diagnose, adjust, saw.

One of the other things that's difficult to test with saws is what they do to a user over 20 or 30 feet of ripping. The fastest saws that i have are saws almost zero rake that you can really fly with in the right wood, but they do wear a user down. I can use them for 5 or 10 feet no problem, but after that, the resistance from the aggressiveness becomes noticeable and it's hard to use them with a relaxed weight-of-the-saw cut because they have such a strong ability to grab.

Originally Posted by pmcgee

I'm intrigued as to whether the most difference would be between styles of teeth in a low tooth pitch like 5ppi, or a finer pitch like 8ppi.

Also whether there would even be a linear (or at least monotonic) change in influence with increasing pitch.
It is conceivable eg that a 4/5ppi and 10/12ppi, the gullets are too large/small to see much effect from style of teeth ... but that there might be a sweet spot around 7/8ppi.
Alternatively it could increasingly or decreasingly influential with rising pitch.


And a third thought - seemingly changing the slope alters at least two characteristics of the teeth ... the shape of the gullet ... and the three-dimensional profile of the teeth. Different teeth might not cut at appreciably different rates, but might remain working effectively for longer.

Cheers,
Paul #300

Paul #300

Aaaaaaagh! We already had infinite variables and now we have infinite plus three .

Of course you are right and we cannot reasonably cope with every scenario. This is why we have to take a punt at the most likely areas. The 8ppi crosscut should be one of three saws a dark sider will have in his arsenal. I know, even that will be open for debate, however we have to start somewhere and it fits very nicely with the five nearly identical saws I have so that seals it really.

The next question is what do we sharpen these saws at? I would suggest

1. Filed straight across: 20 degs Fleam, 20 degs Rake.
2. Filed straight across: 15 degs Fleam, 15 degs Rake.
3. Filed straight across To be advised
4. Filed sloped gullets: 15 degs Fleam, 15 degs Rake, 25 degs Slope
5. Filed sloped gullets: 15 degs Fleam, 15 degs Rake, 45 degs Slope

These are not set in concrete by any means. I am putting them up for consideration. The fact is I could easily come up with at least ten viable combinations of all this. The other variable is the timber. Even, and I do stress even, if we come up with a conclusion it may only be applicable to whatever timber we selected.

Depending on the results we can undertake further tests as in fact I have three D-95s (8ppi) and also another three D-23s (10ppi).

One comment on the size of the teeth and how it affects performance I would point to historical comments that indicate as teeth get smaller, as in fine point dovetail saws, it doesn't much seem to matter what the teeth are filed at providing they are regular and sharp. Does that mean that as the teeth increase in size the performance differences are more obvious? This immediately presupposes the first statement is correct.

So exciting!

Regards
Paul

Originally Posted by D.W.

One of the other things that's difficult to test with saws is what they do to a user over 20 or 30 feet of ripping. The fastest saws that i have are saws almost zero rake that you can really fly with in the right wood, but they do wear a user down. I can use them for 5 or 10 feet no problem, but after that, the resistance from the aggressiveness becomes noticeable and it's hard to use them with a relaxed weight-of-the-saw cut because they have such a strong ability to grab.

David

I agree that human fatigue is a factor and indeed I briefly addressed this in post#12 (para.3). In this instance we are crosscutting and while I have not yet selected the timber, I expect that it will something around 125mm x 50mm or even 100mm x 50mm, which will be a lot less exhausting than ripping a huge length.

Regards
Paul

Originally Posted by pmcgee

When we might expect to find differences and *don't* find them, we can consider why that might be.
There's a long engineering tradition in amplifying small changes ... usually employing some form of 'leverage' I guess.
So ... a factor here might be the short distance of the cut.
A 200mm cut eg should differentiate further.....

Paul, I think in all disciplines we try to set up tests that will be most likely to demonstrate any differences between 'treatments'. What I was looking for in my quasi test was some clear indicator of difference between two saws I thought were different enough to show it up. I definitely chose the wrong task in this instance. I was also well aware that I had more than one variable, so if there had been a decent difference I would have had to do much more work to dissect out how each variable contributed. Given there was so little difference in speed & quality of cut, and really no difference in the degree of spelching when I compared a half dozen crosscuts, and the extreme variability of the pine I was sawing, my enthusiasm waned rather quickly. Actually, the one big surprise to me was that the amount of spelching was similar with both saws. I have a personal rule of thumb that saws of 15tpi & up are ok for crosscutting, the difference between crosscut & rip teeth at the level, in the woods I mostly saw, is too small to worry about. That 'rule' has been developed over a long time & many woods, so I think it was just a fluke that this bit of pine didn't break out much.

I take your point that pushing the cuts deeper might have helped, but I think increasing the width would have been a better bet. As DW says, & I think I said on the other thread, clogging of gullets is rarely a problem with larger saws (8tpi & coarser) unless you regularly munch into very wide cuts in strange, oily woods (& we do have a few of those). However, it does start to show up pretty quickly with finer teeth in wide cuts, so I reckon I could slow the 15tpi saw down quite quickly by asking it to rip a cloggy wood somewhere around 35mm wide, where the 13tpi would still be clearing itself ok.

What I was trying to emphasise, & anyone who has been involved in research knows all too well, is that you spend most of your effort in working out your means of assessment & verifying them - the actual 'experiments' are often an anticlimax....

Cheers,

Something I feel I should briefly touch on is the saws themselves. Probably not for the cognocenti, but I appreciate there are people out there, who while they enjoy handtools and specifically saws, do not spend every spare moment on the Disstonian Institute website. I have to confess that I went to the D-23s straight away for two reasons. The first is that I was fairly sure I had a number of similar tooth configurations in this model and secondly it is in fact a very good saw.

However, it is something of an unsung hero. I often (actually when I am attempting to sell them) point to the fact that I have seen King Roy (Roy Underhill. Look him up on UTube) use a D-23 in his videos.

The fact is that the D-23 was a level up from the ubiquitous D-8 to put it's standing into perspective. It first came into being in the early 1920s in conjunction with it's stable mates the D20, D21 and D22. The D23, which morphed into the D-23 in 1928 with Disston's revamp was the straightback, lightweight version. The stablemates gradually disappeared from the line up leaving the D-23 on it's lonesome.

Somehow it does not have the charisma of some other models in the Disston range, and in a way this is a pity because it is an excellent saw. Interestingly, I have nine examples of this saw and none of them have a damaged handle. I wish I could say the same about all my saws! The Disstonian Institute particularly makes a mention of this phenomena, which is worthy of mention in the handsaw market.

The D-95s, which are in the group reserved for follow up if that should be warranted, was and still is the most expensive saw made by Disston. Intoduced in 1935, it was at times described in their literature as their "Masterpiece" saw. It features a two piece, high quality plastic handle, which should be unbrakeable, but isn't. The quality of the saw is excellent. It was last produced in this form in 1955 when Disston sold the company.

Ok. Enough history. Just establishing the credentials:The saws, not me!

Regards
Paul

I managed to refurbish two of the D-23s today so that's two down, but still more than a big red roo (for the intercontinental participants, that is the largest marsupial in the world) could jump over still to go .

On the positive side they are cleaning up really nicely . The roos are still the same as they always were. Plentiful .

Regards
Paul

I thought it was time for two things. Firsty an update on progress with the saws and secondly a small taster that has come up coincidentally.

I have cleaned up the saw plates on the D-23s and started on the handles, which of course has no real bearing on this test, However as these saws will be out up for sale after the test I am expecting that prospective customers would really like the saws to be presentable.

The saw plates have all come up very nicely without being in mint condition and will be a good test bed.

Now I have mentioned elsewhere that I am also restoring four Simonds No.5 saws. One saw is going to be my fine tooth keeper with the other three being offered for sale eventually. My keeper and one of the group of three are 11ppi (the other two are 8ppi and 5 1/2 ppi rip).

So the point of this is that the other night I sharpened my saw, which is a an early No.5 from the "Crescent Moon and Star" period making it pre-1907, using a straight across style and after sharpening tried it on a piece of unknown hardwood. It is probably Ironbark, but I can't be certain. Definitely heavy and very hard. Reddish.

The timber is 125mm wide and 47.61mm thick (I have measured to two dcimal places to give the impression this is a scientific study ). Using little more than the weight of the saw, in other words guiding the saw, it took exactly 60 stokes to saw though this timber and was delightfully smooth.

However, I do have a preference for sloped gullets so I then filed the saw with a sloped gullet profile, which is purely the next step.

I tried it again on the timber, which incidentally is not parallel along it's length. It is gradually increasing towards 175mm wide. However it was what I found in the dark the other night and it was a spontaneous decision to test. No premeditation or planning of any description here.

This time I felt the saw was a little rougher in the cut and it was tending just to bind a little. It probably needs to be reset, which I will do. I was therefore surprised when it cut the timber in 45 stokes!

This is the saw with the old handle, which is what I used (just a couple of saw bolts holding it on), and also with the new handle.

Filing comparison. Sloped. Straight across on Simonds No.5 006.jpgFiling comparison. Sloped. Straight across on Simonds No.5 008.jpg

Today I sharpened the other No.5 (same ppi), but from a later era 1907 - 1922 I made a slight adjustment to the rake by increasing it to 20 degs, but otherwise it was the sharpened with the same sloped gullets.This is the saw:

Filing comparison. Sloped. Straight across on Simonds No.5 005.jpgFiling comparison. Sloped. Straight across on Simonds No.5 007.jpg

This time the saw was extremely smooth, almost effortless and it took 40 strokes ( I wish it had taken 39 or 41 strokes as that would have complied with the law of exactness far more credibly) to saw through the same timber. Well, I rushed for the camera. I was tempted to take a selfie to capture the smile on my face for posterity, but I have shielded you from the trauma that might create .

More than this, the cut was super smooth. This is the cut end of the timber, although I don't think I have captured the texture well:

Filing comparison. Sloped. Straight across on Simonds No.5 009.jpgFiling comparison. Sloped. Straight across on Simonds No.5 010.jpgFiling comparison. Sloped. Straight across on Simonds No.5 011.jpg

It is the grain that makes the last pic appear ridgy. There is no discernible saw mark to the touch.

Ok, that is the appertiser, which I now realise increases my susceptibility to prejudice. I think I am going to have to call for volunteers to to undertake the sawing test when the D-23s are ready.

Any takers?

Regards
Paul

PS. Sorry about the state of the grass. SWMBO has been away for six weeks and although back for nearly three weeks she still hasn't got around to the mowing.

Originally Posted by Bushmiller

......PS. Sorry about the state of the grass. SWMBO has been away for six weeks and although back for nearly three weeks she still hasn't got around to the mowing....

I dunno - why are good women so hard to find, these days....

But on a more serious note, Paul, I'm impressed by the quality of the cut, but even more by your apparent consistency with a saw!

However, I'd be even more impressed if you repeated each cut at least 5 times & got such a tight result. I find that even trying hard to be consistent, I get up to 10% variation in the number of strokes it takes me to cut through a decent-sized board with the same saw. So I'll need multiple replicates, a statistical evaluation and independent verification, before I'll accept your scientific paper for publication......

Cheers,