Thread: Sloped Gullets

Ooooh! Independent evaluation? That's a tricky one. I'll see if SWMBO can take time off from her knitting. I might have to offer to make tonight's meal (just to maintain true impartiality ). Statistical evaluation. You know the old saying, "There's lies, Damned lies and Statistics!" So the statistics should be a piece of cake.

I will check the vernier gauge to see how many places of decimals it will spit out . Actually that is one of my pet hates at work where I find people writing in two places of decimals when actually a whole number is more than adequate.

Yes, I probably should have done multiple saw cuts to validate and provide consistency and when we test the D-23s we will do just that, but with this I just wanted to prepare these No.5 saws to get ready for a big clearout. The work is building up and even for me there is a limit to the number of times I want to sharpen individual saws.

How is your saw arm? I will be looking for saw testers? I will need somebody from the denial camp .

Regards
Paul

PS. I will be onto the gardener about the grass. It really is beyond a joke.

I feel like a fiddler crab from filing saw backs so, after recovery, my saw arm should be in good shape.

Originally Posted by rob streeper

Hi Paul,

Have you run the numbers on your fleam angles? I'm tending away from higher fleam, have been for a while. I file my xcut hardwood saws in the range of 10^o-15^o or so. I found a US Army field guide recently that suggested 45^o fleam for xcut.

Regards,
Rob

Rob

Sorry, I missed this request. The short answer is that I have gone to 15degs for sloped gullets and 20 degs for teeth filed hoizontally. I have seen suggestions of 35 degs for mitre saws, but the only reference I have come across for 45 degs is for the 120ACME saws and that is Disston's recommendation. I would suggest that higher fleam angles would only work well in the softer timber species.

Regards
Paul

Fleam angles are something I've given some thought to, but little action, in terms of any serious search for the Goldilocks points. At first blush, it seemed obvious to me that the more you angle the file (i.e. more fleam), the 'sharper' the knives you are forming on the leading side of each tooth, so the saw ought to cut easier. But maybe there's more to it than that. A typical crosscut consists of nothing but all those 'knives', which may be good at slicing fibres on each side of the kerf, but what about the material in the middle? Big two-man crosscuts have raker teeth expressly for the purpose of removing the middle, but the ordinary crosscut saws we use for carpentry/cabinetmaking don't. After pondering this a little more, I decided that the bevels on the teeth simply bludgeon the chips off - not all that difficult because they are just teeny bits of short-grain in the middle of the kerf, & easily knocked off once each end is sliced.

In terms of chisels or plane blades, the 'knife' of a crosscut tooth is hardly a sharp one! With a "standard" 15-20 deg fleam angle, we're talking about a cutting angle of something like 70-75 degrees, even the 'extreme' of 45 still leaves a cutting angle of 45. So we can't take the 'knife' analogy too far, which got me thinking that a blunt bevel is part of the grand scheme, to knock out the chips more effectively. It also serves to keep the teeth points reasonably robust, a consideration when hoeing into very hard woods such as we have around Aus. In some woods, you might gain something by going to the maximum bevel angle, but for routine work, I suggest our forefathers have done the experimentation for us and found that the angles most often advocated (15-20 or so) are the best compromise for general sawing. Dunno - some day when I find time hanging heavily on my hands I'll set up some trials & test my hypotheses as best I can.......

Cheers,

Originally Posted by rob streeper

I feel like a fiddler crab from filing saw backs so, after recovery, my saw arm should be in good shape.

Rob

I'll let you know the schedule. You will be welcome. Can probably meet you from Brisbane. Unfortunately Millmerran International Airport does not run to direct flights from San Antonio.Something to do with the 1200m long 10m wide strip! There are only a few jumbo drivers capable of the manoeuver and they all died in the attempt.


Regards
Paul

Originally Posted by Bushmiller

The short answer is that I have gone to 15degs for sloped gullets and 20 degs for teeth filed horizontally. The only reference I have come across for 45 degs is for the 120ACME saws and that is Disston's recommendation

I was recently researching saw sets and the instructions for a Stanley 42/43/442 gives you saw filing instructions too; it states for crosscut saws you should hold the file at approximately 45 degrees to the saw plate. As pretty much all I know about saw filing is what I glean from discussions such as these I sort of tend to take anything written down on sepia tinted paper as gospel!

So... for Aussie hardwoods like Red Gum I should be looking more towards 15-20 degrees rather than 45? Or should I just give it a crack at 45 and see how it goes?

Chief

There is always a balance between cutting ability and longevity. If pure sharpness was our criteria we would use something that resembled a razor blade However, while a razor blade works well enough on body hair it would be pulled up very quickly on hard timber.

So as has already been alluded to, a high fleam angle (45 degs would be considered the upper limit by most people I think) may work well enough in soft timbers, but to last a reasonable period of time before sharpening, this angle needs to be reduced in our hard timbers.

There is also a real risk of breaking a tooth or many teeth if the tooth does not have sufficient metal behind it. Think of it the same way you would a chisel. You are not going to hammer a fine paring chisel. The edge would quickly damage as it just does not have the strength.

If you have several backsaws, you can indulge in the luxury of several different fleam angles designed to suit everything from soft Radiata pine to hard as nails Gidgee. If you have one saw, 15 degs to 20 degs will serve you well and perhaps you can chose based on the types of wood you use or think you will be using.

Regards
Paul

Paul,

I get the sense that we're in yet another area of woodworking tool characteristics that rests primarily on received wisdom and is thus ripe for systematic investigation. I'm not implying that the commonly used practices and figures are incorrect or even that they can be improved but it does seem that there's a lot of 'should be' and 'must be' type reasoning being applied.

Any new news on your slope angle work?

Thanks for the offer but other work keeps me on the ground for now. I'm planning a look at blade hardness vs. durability after I finish looking at setting methods so I may have time in a few months to make up some blades reproducing your test pieces.

Regards,
Rob

Just a small update to maintain momentum:

The five D-23s have been restored from the cosmetic perspective and the first two have been sharpened. I will try to post some pix in the next day or two.

Regards
Paul

Whilst the saws are ready in principle as I mentioned in the previous post only two have been sharpened.

Here are the five saws:

Disston D-23s 007.jpgDisston D-23s 005.jpgDisston D-23s 006.jpg

The sharpening angles will be as follows:

20 deg fleam, 20 deg rake, 0 deg slope (Done, second saw in pic above)
15 deg fleam, 15 deg rake, 0 deg slope
20 deg fleam, 15 deg rake, 0 deg slope
15 deg fleam, 20 deg rake, 45 deg slope (Done, first saw in pic above)
15 deg fleam, 25 deg rake, 45 deg slope

Clearly there are many more combinations that are possible. The combinations multiply even more when sloped gullets are factored in. Clearly I cannot cover all possibilities.

My plan is to sharpen the saws and briefly test each to make sure they are cutting as would be expected. Then I will set them all again and lightly sharpen again in readiness for testing.

Then my proposal is to set a date and invite interested people to come along. Some will be the official testers and others will be observers, but once the testing is complete there will be the opportunity for anybody present to try out the saws probably with the facility to give their opinion.

All being well the results will be published in this thread in due course.

Please feel free to offer any comment ahead of the testing. Naturally I have the right of supreme veto (just see the slogan at the foot of my posts), but all suggestions will be evaluated.

I had hope to have all five saws finished while I had my recent two day saw exhibition, but I only sharpened one saw on each day. I spent too much time chatting.
Regards
Paul

I am most embarrassed that is is more than three and a half years since the last post and I have not proceeded further. I still have the saws and I really must pursue it, but in truth it has slid down the priority list.

However that is not the purpose of this particular post. It is on the subject of sloped gullets and whether they were indeed the preferred method of sharpening. My contention has always been that if saw teeth were not intended to be sharpened with sloped gullets the manufacturers would not have produced the metal saw vices that can be canted back at an angle. I actually would prefer to call the teeth angled as my belief nowadays is that it is the angle of the top of the tooth that is important and the sloped aspect of the gullet is just a consequence of the geometry.

I guess there is an argument that the sloping of the gullet may eject sawdust better but I can't be certain that is the case. Nor am I convinced that the tooth is made taller and the gullet deeper thus creating an ability to "hold" more sawdust. Lots of discussion material there. The tooth may appear taller on one side but it is shorter on the other. Certainly the tops of the teeth must be the same height.

These are typical saw vices adjustable for angle and enable the filer to saw at the horizontal as the saw itself is canted over.

saw vices 1894.jpg

The other day I came across this extract from a Disston catalogue dating from 1876 and it is the first reference I have seen advocating what today we call sloped gullets:

Disston Saw vice from 1876.jpg

The comments above are not mine but do echo some sentiments I have made in the past. Why did this practice fall from favour? My own theory is that it is a similar problem that accompanied progressive tooth rip saws: Namely, that the automated filing machines could not replicate these patterns and hand filing was too expensive in the modern competitive world.

Regards
Paul

I have been searching for a patent for the "Improved" clamp mentioned in post #42 without success. I did find where the reference above appeared in recent times from Brent Beech:

Sloping Gullets

I find it strange that a device such as this was not patented. It could have been an omission. Apparently the 3M company neglected to patent Wet and Dry paper. A little bit of a balls up for a company that specialises in surface coatings so maybe a lil' ole saw clamp pales into insignificance.

Regards
Paul

Originally Posted by Bushmiller

I have been searching for a patent for the "Improved" clamp mentioned in post #42 without success. I did find where the reference above appeared in recent times from Brent Beech:

Sloping Gullets

I find it strange that a device such as this was not patented. It could have been an omission. Apparently the 3M company neglected to patent Wet and Dry paper. A little bit of a balls up for a company that specialises in surface coatings so maybe a lil' ole saw clamp pales into insignificance.

Regards
Paul

Excellent thread as always Paul,
Will you be applying for the Patents right on the “improved” saw clamp.
Or just let 3M pick it up?

Cheers Matt

Originally Posted by Simplicity

Will you be applying for the Patents right on the “improved” saw clamp.
Or just let 3M pick it up?

Cheers Matt

Matt

As soon as I find out how it is made, I will be looking to make up a version. However, I have to say I currently use a clamp that is the full length of the saw (a handsaw not just a backsaw) and I would be looking to adapt the "Disston" principle to achieve that. That clamp may not have been made by Disston, but whether it was made by Disston or one of the Disston employees or an external inventor, I have been unable to track a patent and I have searched quite hard for that. If any of the patent experts can find something i would be most appreciative. A search under "saw clamp" seems the first place to try and can be narrowed down to say 1870 to 1876. I have gone beyond those dates still without a result.

The original would have been a casting but I would probably endeavour to fabricate something. I can imagine the mechanics of the device mostly, but the aspect that puzzles me is what looks like a dial indicator on the top. Was it a guide for the fleam angle?

3M are still smarting from their stuff up and licking their wounds: Not anticipating too much grief from that direction.



Regards
Paul