Thread: Sources of Split Nuts For Handsaws

This illustrates what I am talking about above. I didn't do this using a square shank bolt of course, it was the result of a moments inattention at the drill press. It was a pretty nice stock until then but mesquite can be very brittle.

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Originally Posted by DSEL74

Maybe this could be analysed to some degree in reverse. Looking at how many older saws are missing their bolts and damage to the holes what are the most likely causes and points of failure?
I do think machined bolts and the current quality of brass used would be superior for one thing to the soft cast bolt of eras gone by.

I agree, materials have advanced tremendously even in my lifetime, let alone since the 17th century. My perception is that tools like saws were simply tools. The makers and users were not necessarily trying to produce works of art such as the many fine pieces on this site.

As you can see below, I like pretty wood too so I am going to give this product a try. Anybody have experience with it?

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I am going to try vacuum imbibing this into a semi-finished mesquite handle. It will likely clog the surface fibers to the point that they resist finish but I have some ideas about overcoming that problem. I'll post the results when I have them.

Originally Posted by rob streeper

I agree, materials have advanced tremendously even in my lifetime, let alone since the 17th century. My perception is that tools like saws were simply tools. The makers and users were not necessarily trying to produce works of art such as the many fine pieces on this site.

As you can see below, I like pretty wood too so I am going to give this product a try. Anybody have experience with it?

DSCN0143.jpg

I am going to try vacuum imbibing this into a semi-finished mesquite handle. It will likely clog the surface fibers to the point that they resist finish but I have some ideas about overcoming that problem. I'll post the results when I have them.

Blue Spruce acrylic resin infuse their chisels & mallets, and the pen turners stabilise and infuse their pens. So I don't see why it couldn't be applied here.

Originally Posted by DSEL74

Blue Spruce acrylic resin infuse their chisels & mallets, and the pen turners stabilise and infuse their pens. So I don't see why it couldn't be applied here.

I will also try applying it just to the insides of the back mortise and the recesses for the screw heads.

Regarding snug fits between the blade and the bolts, that is something I try to avoid. It may help to keep things tight, but will stress the handle as it shrinks and expands in response to changes in its moisture content. It may or may not harm the wood, but I have stripped the threads on many an old saw bolt that was jammed tight against the edge of its hole in the blade when the handle shrank.

I owuld much rather rely on friction to hold everything in place. It doesn't take much torque on the nuts to provide enough of it, and it is a simple matter to tighten the nuts up when needed. In my experience, most saws will need to be tightened up less frequently as the wood settles in.

I could not agree more! Never, and I mean NEVER trap a piece of wood so that it cannot move, or it will crack in between the bolts.

Originally Posted by rob streeper

I will also try applying it just to the insides of the back mortise and the recesses for the screw heads.

Rob. If mesquite has a tendency to be that brittle I wouldn't bother trying to make it work for saw handles. There are much more suitable woods in the U.S. to choose from. IMO

Stewie;

Originally Posted by planemaker

Rob. If mesquite has a tendency to be that brittle I wouldn't bother trying to make it work for saw handles. There are much more suitable woods in the U.S. to choose from. IMO

Stewie;

Stewie,

Sure, plenty of usable woods here. I have some fantastic figured mesquite infected with mistletoe. It looks like a burl and physiologically it's probably more like a tubercular granuloma or cyst. I'd hate to turn it into a sugar bowl.

My feeling is: Why not climb that mountain?

Rob

Originally Posted by TobyC

I could not agree more! Never, and I mean NEVER trap a piece of wood so that it cannot move, or it will crack in between the bolts.

Now I'm confused. On the one hand square shank bolts are advocated because they can be tightened more snugly. Yet when I advocate fitting bolts better to the plate I'm somehow making things too tight?

Looking at this: http://www.extension.purdue.edu/extm...NR/FNR-163.pdf I see that the wood scientists suggest that the primary axes of moisture induced swelling in wood generally occur along the longitudinal (along the grain), radial and tangential axes of a flat sawn plank. A quartersawn blank will swell proportionally more in the radial plane than in the tangential because it is thinner in the tangential plane and the longitudinal swelling will be the same as in a flat sawn plank.

Since the planks we are discussing here have the grain generally running from the screws to the top horn the axial and tangential swelling axes will be to the top and or sides at various angles roughly orthogonal to the saw plate. The screws are typically placed centrally in the section of the tote that surrounds the back of the blade plate where the tangential and radial axes of swelling are directed outward from the plate toward the screw/bolt inner faces at some angle relative to the inner flats of the screws and bolts. Longitudinal swelling will be along the direction of the grain, where the forces will be applied to the sides of the screw/bolt circumferences and the sides of the screw shanks and to the bottom of the blade back.

Depending on the type of wood we are talking about, most planks swell more in the radial and tangential axes. That's why we want quarter sawn planks where the tangential plane thickness is minimal thus reducing or eliminating cupping. But lets face it, straight grained quarter sawn planks have relatively uninspiring figure i.e. they are visually boring. I remember Mr. Murray, my first wood shop teacher, admonishing us all to stick with straight-grained quarter sawn wood. That swirly stuff was for the fireplace.

I have never heard of any advice to loosen the saw screws when you are done using the saw so we can assume that the screws are always left tight.

In the world of artistic saw totes, the beautiful swirly birdseyes and so forth are anisotropically swelling and contracting with every change in ambient humidity. I was reading on the safety forum where there is a note about a fellow having been cracked across the nose with a chunk of jurra burl he was turning which exploded suggesting the presence of lots of anisotropic internal forces. These swelling forces bear heavily on the inside flats of the screws and bolts, i.e. those surfaces facing the radial and tangential planes of the wood, more heavily than they do elsewhere due to two factors. First the flats are the largest pressure bearing surfaces of the screw and second the swelling in the radial and tangential planes is greater generally (depends on the wood) than it is in the longitudinal axis.

It is further clear that these swelling problems should drive the selection good finishing to control moisture content and thus produce a greater degree of dimensional stability.

In other-words, how is a shank that fits tight in the plate causing a problem when it appears that most of the deleterious forces caused by moisture induced swelling and contraction play on the heads of the screws and the faces of the bolts?

I'm not trying to be irritating here but I do want to hear alternatives to my thoughts.

Thanks,
Rob

Hi Rob,
I'd encourage you stick with the mesquite, (that mistletoe infection sounds interesting) and experiment with the vacuum infusion idea, it will be interesting to see how the idea progresses.

I've mostly used walnut and she-oak for saw handles, both are very stable timbers, She-oak is unusual in that the radial and tangential shrinkage are almost the same, and it has a lot of crosslinked grain. Walnut would still be my favourite since I have a ready supply from a friend who is a gunstock maker, walnut also holds detail very well.


Toby,
What you say is mostly true. However, saw screws should always be tight. In this instance wood movement is generally not a problem, other than the timber slowly gets compressed over many years of cyclic moisture changes, I've never seen a saw handle split because of screws being done up too tight. Seen plenty come loose after the timber dries out.

Ray

Originally Posted by RayG

Hi Rob,
I'd encourage you stick with the mesquite, (that mistletoe infection sounds interesting) and experiment with the vacuum infusion idea, it will be interesting to see how the idea progresses.

I've mostly used walnut and she-oak for saw handles, both are very stable timbers, She-oak is unusual in that the radial and tangential shrinkage are almost the same, and it has a lot of crosslinked grain. Walnut would still be my favourite since I have a ready supply from a friend who is a gunstock maker, walnut also holds detail very well.


Toby,
What you say is mostly true. However, saw screws should always be tight. In this instance wood movement is generally not a problem, other than the timber slowly gets compressed over many years of cyclic moisture changes, I've never seen a saw handle split because of screws being done up too tight. Seen plenty come loose after the timber dries out.

Ray

Ray,

I'll post a photo of a mesquite/mistletoe burl in situ. The Tejano's here refer to it as 'tree killer'. Mistletoe infects both mesquite and live-oak in this area.
Your mention of she-oak inspired be to look around and I found a domestic supplier of both she-oak and Australian blackwood, Hearne Hardwoods in Pennsylvania. I'll probably order some after I work out the kinks with mesquite infusion.
The various sources discussing infusion list heating, pressure treatment and vacuum imbibing as methods for saturating woods with acrylics. The Minwax product is in acetone so it should penetrate very well. The acetone will limit me on the vacuum I can draw and heat that can be applied but I think with several cycles I can get the product in. The critical point of acetone is 235 C at 48 bar which is beyond the capability of any chamber I have at this point so supercritical fluid treatment is out.
After infusing I'll try to lightly back-extract the blank with solvent to reduce the polymer content of the outer layer of wood to facilitate finish penetration. Mesquite polishes up like glass using several coats of BLO and the figure of the burls can be really nice.

Rob

Originally Posted by rob streeper

Now I'm confused. On the one hand square shank bolts are advocated because they can be tightened more snugly. Yet when I advocate fitting bolts better to the plate I'm somehow making things too tight?

Well Rob, the main reason I advocate square shanks for saw bolts is so they can be un-done (years down the track....)

Originally Posted by rob streeper

Looking at this: http://www.extension.purdue.edu/extm...NR/FNR-163.pdf I see that the wood scientists suggest that the primary axes of moisture induced swelling in wood generally occur along the longitudinal (along the grain), radial and tangential axes of a flat sawn plank. A quartersawn blank will swell proportionally more in the radial plane than in the tangential because it is thinner in the tangential plane and the longitudinal swelling will be the same as in a flat sawn plank.

Changes in dimension due to moisture uptake/release are virtually all in the radial & tangential axes. The change in longitudinal dimension is neglible for most woods. Most woods shrink & expand more tangentially than radially, and tangential movement generally increases toward the outside of a log, because this is where the younger fibres are. You can think of it this way, the younger cell walls have had less time to undergo chemical changes & contain less water-excluding gunk, so more room for moisture to be taken up. But where a quartersawn board gets most of its 'stability' from is that the shrinkage & expansion are more symmetrical, and the movement across the widest dimension of a plank should be the lowest possible for that species - but they still move....

Originally Posted by rob streeper

....Since the planks we are discussing here have the grain generally running from the screws to the top horn the axial and tangential swelling axes will be to the top and or sides at various angles roughly orthogonal to the saw plate. The screws are typically placed centrally in the section of the tote that surrounds the back of the blade plate where the tangential and radial axes of swelling are directed outward from the plate toward the screw/bolt inner faces at some angle relative to the inner flats of the screws and bolts. Longitudinal swelling will be along the direction of the grain, where the forces will be applied to the sides of the screw/bolt circumferences and the sides of the screw shanks and to the bottom of the blade back.

Depending on the type of wood we are talking about, most planks swell more in the radial and tangential axes. That's why we want quarter sawn planks where the tangential plane thickness is minimal thus reducing or eliminating cupping. But lets face it, straight grained quarter sawn planks have relatively uninspiring figure i.e. they are visually boring. I remember Mr. Murray, my first wood shop teacher, admonishing us all to stick with straight-grained quarter sawn wood. That swirly stuff was for the fireplace.

If you are talking small saws with two bolts, I cannot see any problems arising from tight screws, since the bolts are generally placed pretty much in line with the grain, & there will be virtually no wood movement in that direction. The miniscule amount that does occur is likely to be well within the elastic tolerance of the material (unless your Mesquite is unlike any other wood I've ever met!). Where you might run into trouble is if you used a 'lively' wood for a full-sized saw, with a wide handle, and bolts spread right across it. The fact that you rarely see handles split because of wood movement (or at least I have never come across it) is probably due to the fact that saw makers chose their handle woods wisely. Curly woods, which I happen to like too, can be fine, as long as they have sufficient structural strength, but because of that wild grain, it can be a lot more difficult to ensure that it will be ok, in man cases. Go for woods with a reasonably low coefficient of moisture movement, & good structural properties, & I'm sure you'll have few problems....

Originally Posted by rob streeper

.....In the world of artistic saw totes, the beautiful swirly birdseyes and so forth are anisotropically swelling and contracting with every change in ambient humidity. I was reading on the safety forum where there is a note about a fellow having been cracked across the nose with a chunk of jurra burl he was turning which exploded suggesting the presence of lots of anisotropic internal forces. These swelling forces bear heavily on the inside flats of the screws and bolts, i.e. those surfaces facing the radial and tangential planes of the wood, more heavily than they do elsewhere due to two factors. First the flats are the largest pressure bearing surfaces of the screw and second the swelling in the radial and tangential planes is greater generally (depends on the wood) than it is in the longitudinal axis.

It is further clear that these swelling problems should drive the selection good finishing to control moisture content and thus produce a greater degree of dimensional stability.

In other-words, how is a shank that fits tight in the plate causing a problem when it appears that most of the deleterious forces caused by moisture induced swelling and contraction play on the heads of the screws and the faces of the bolts?

I'm not trying to be irritating here but I do want to hear alternatives to my thoughts.

I can't see birds-eye figure per se being much of a problem - I've made several handles from B.E. Maple, with no problems over the medium-term, at least (& I live in a climate with moderately extreme moisture cycles). For really highly figured wood, it is nigh on impossible to predict maximal & minimal dimension changes - you just have to go on experience, trial & error, imo.

I agree with you emphatically, that the major problems come from simple expansion & contraction affecting the wood under the bolt heads & nuts. There is no doubt handles loosen & need tightening when the fibres are crushed beyond their elastic limits, but this generally settles after a cycle or two, as you say.

And unless you encase the handle in some goop that hermetically seals it, this is going to happen. NO 'standard' finish will prevent ingress/egress of water - they will slow it down a bit, but that's all. Some expansion/contraction is going to happen, so lets just get over it & tighten our nuts occasionally. I think this is a 'problem' that is getting over-intellectualised .....

Cheers,

Ian,

In the inimitable words of Kant, I think therefore I am.

This very useful discussion has inspired me to go in a new direction - use bushings. The model RC hobbyists here apparently use flanged brass bushings for their purposes. Associated Bushing 3 16 x 5 16 Flanged ASC6863 | eBay

Drilling a little deeper and wider into the screw mounting position would allow me to secure 4 of these in place with epoxy. Since they are porous they are never coming out. Thus increasing the wood to metal bearing surface, stabilizing the local wood with a combination of epoxy and hardener and providing a very tight screw shank to bushing to wood fit that will be much less subject to wear and swelling since the screw head and nut face will bear on the flanges. I'll give it a try and post the results.

Best,
Rob

Originally Posted by rob streeper

Ian,
...Since they are porous they are never coming out...

I am not familiar with those, but a quick glance at them leads me to believe they are used as bearings. Before you use epoxy on them, you may want to make certain that they are not oil impregnated bronze. If they are, you may have trouble getting with adhesion. That being said, I don't see much need for a glue joint unless you are concerned about the flange rotating or moving in the wood.

I can be a little slow at times, but I'm still not sure I see an advantage to having a super tight fit between the handle and the bolt shank. Unless the wood is 100% stabilized, isn't it better to have a little cushion for expansion and contraction? In theory, you can minimize the movement of the wood between fasteners by choosing the wood orientation carefully and aligning the fasteners with the grain. But what happens if that is not possible? Or when you use three or four fasteners on a larger saw?

Hi Isaac,

I thought about the oil impregnation issue too. I'm going to reflux the bearings in methylene chloride or hexane to remove any oil. They're pretty small and it should not take long.

I think that by vacuum infusing the wood with resin, leaching the surface layer back out and setting the bushings in epoxy I will realize the following benefits:

1) A nice tight fit-up of the blade and tote without relying primarily on friction of the tote cheeks against the blade and back.
2) Elimination or near elimination of the moisture driven swelling problem.
3) Elimination of the wood fiber compression problem.
4) Drastic reduction in wear of the screw holes in the tote.
5) Tight mechanical fit of the tote to the blade through the tight fit of the screw shanks to the holes in the plate.
Plus of course I can say that I'm the only one who does it.

Hopefully all of this will eliminate or greatly reduce the need to periodically tighten the screws on with wooden stocked hand saws that at this point we all just live with.

Rob