Tuesday, 25 February 2014

No Snickering - Thank You Very Much...

Okay, I admit it. I chickened out.

I glued a couple of pieces of scrap together and planned one edge down to a 14° angle to use as a saw fence to cut the pin slots for this sliding dovetail.

I just didn't want to take a chance and possibly screw up a lovely chunk of oak using a new technique, so I went with what I know...

They turned out pretty good, though, so I'm happy...



Monday, 24 February 2014

Chiselling a Square Cut...

I had to trim the two ends of the centre stock for the portable vise and, frankly, I was a little worried about it. I'm just not very good at making square cuts with a saw. I'm sure it is an eyesight thing, and because I don't have any depth perception, it is damned near impossible to tell if the saw is at right-angles to the stock or not. I've tried different things to find a work-around, but I haven't been successful.

While checking out some woodworking videos on youTube the other day, I came across a post belonging to Paul Sellers, a woodworker in Wales, at least I think he is Wales. The post is "Part 3" of his, "How to build a workbench" and is titled, "Cross cutting the top", which seemed right up my alley at that moment. I watched the video and when it came time to bite the bullet and do the cuts, I decided to do it following Paul's instructions. It was a good decision

I marked out the cuts with a box cutter, fitted with an extra sharp blade. I then took a ¾" chisel and starting about ³⁄₈" on the waste side, I chopped out a bit so the wood angled into the knife-cut. I even went beyond his instructions and did the same to the ends that would face away from me while I worked the saw, but as it turned out, this second trough wasn't helpful to the saw, but it was for me. I could see it better than a line, so it helped me see where square was.

This is what the glue-up looked like when I was ready to take it outside and run a saw through it...

I have worked this trough-guide trick before, but only for short cuts. I do use a slight variation of it often for cutting dovetails, but I have never used in on a cut as long as this one or with stock as thick as this one. The theory behind it is that a saw is like electricity or water; it likes to take the path of least resistance. The saw will tend to follow the square cheek that the knife cut and if it decides to wander, it will be more likely to wander away from the perpendicular-cut wall. This is where the ramp that you cut with the chisel comes into play, as its angle will try to force the saw back against the square face, which just happens to be the line you want the saw to follow.

With this cut, though, Paul's instructions were a little different from what I was used to. What he suggests is that you follow the knife-line across the top of the cut, but angle the cut away from plumb across the bottom, leaving a little material on the waste side of the line. I used an old Diston full-sized crosscut and made the cut.

Once the waste was gone, I stood the block up on its end and using a Veritas Low Angled Jack, I  planned away the waste down to the line, doing so halfway across from one side, and then turning the stock around and finishing it off from the other.

I have to admit, Paul's instructions make cutting a very square end to a very big board very easy.

I was so impressed with the results, I decided to use the same process to cut a sliding dovetail in the side rails of the frame...

I'll let you know how I make out.



Saturday, 22 February 2014

Sometimes I'm Just Not In The Mood For A Little Tail...

I was just getting ready to layout the tails for the dovetail joints in each corner of the frame for the portable vise, but as I started to set up the dividers to mark-out some really cool, thin-tailed doves, a thought hit me that maybe what I had in mind was not the best way to go for something like this.

I am so enthralled with dovetail joints, I didn't even think about it. I just started to go at them with my only thought being how they would look, not how they would perform. I decided to hold off for a bit and take a serious look at what this type of joint is all about.

The first item on my new agenda was to create a couple of dovetail illustrations in different styles so I had some visuals to ponder.

The first illustration I created was the dovetail joint I was planning to use, one with thin pins...

I then created a dovetail joint with equal sized tails and pins so I could see the difference...

With my illustrations in front of me, I sat back and tried to remember the different points about them that I had read in the past.

The most common praise for dovetail joints that I remembered was about their ability to deal with wood movement. I came to my first conclusion that this, to me, isn't an issue in this application because the pieces being joined together are all sawn in the same manner and will share the same environment. For me, movement would only be relevant if the dovetail joint is used to joint two boards of different species together, or one board would spend its life in a damp environment while the other in a dry one (how that could happen, I have no idea).

So if wood movement isn't a factor in this application for using dovetail joints, what is?

Well for one thing - stresses!

Somewhere I read that dovetail joints, due to their mechanical design, deal with stresses quite well. Thinking about it in layman's terms, I came to the conclusion that the stresses on the joint come in six directions; forwards and backwards, up and down and out and in. If you have a look at the illustration below, you can see how a dovetail joint deals with five of these six directions, and why it excels at each. The angles of the tails and how they fit to the angle of the pins handle forward stress while the cheeks between the tails deal with the backward stress. The cheeks of both the pins and tails resist the upward and the downward stresses while the cheeks between the pins alone deal with the inward stress. The thing is, I also realized that a dovetail joint can't deal with outward stress.

Thinking about it, I realized that the way a dovetail joint goes together is its achilles heel. The straight pins allow the tails to slide into them during assembly, but they also allow stress to reverse the process as well. If you cut both the tails and the pins on the angle to help the joint deal with the outward stresses, you wouldn't be able to assemble the joint. 

My second conclusion was that, when it comes to keeping the joint together, the dovetail joint excels in five out of the six stress directions.

Is there a way to overcome a dovetail joint's achilles heel?

Yes - glueing!

You wouldn't glue two boards together using a butt-joint because glueing end-grain surfaces, even to a long-grain surface, is a waste of time. A glue joint only works if the surfaces being glued together are both long-grain.

If you look at either of the two dovetail illustrations again, you will note that both the side-cheeks of the tails and the side-cheeks of the pins, where they come in contact with each other, have long-grain surfaces. It is these surfaces that hold the joint together, and while we all like to spread a little glue on the cheeks between the tails and pins, we are really wasting our time as they are end-grain, and have no glueing integrity.

My third conclusion was that these long-grain glueing surfaces are another beauty found in the dovetail's design. It creates long-grain glueing surfaces where none existed before and it is these glueing surfaces that not only add to the joints mechanical strength, but compensate for its achilles heel as well, the one stress direction the joint can't deal with.

So would more tails result in a stronger joint?

It depends!

In the case of the first two illustrations, from a glueing perspective, the narrow pins have the distinct advantage. The traditional dovetail layout has two tails and three pins, but by narrowing the pins considerably, an additional tail and pin can be added. This addition adds 50% more long-grain to long-grain glueing area, which is considerable under any definition.

This was the style of dovetails I had planned to use on the portable vise frame, but looking at the illustrations, I came to my forth conclusion that the joint, with thin pins, won't be strong enough. True, there is lots of that wonderful long-grain to long-grain glueing area, but I think what the thin-pinned joint gains in glueing strength, it looses in pin integrity.

If you compare the two illustrations of dovetail styles again, it is pretty obvious that the 50% addition in glueing area came at a cost of almost 40% in pin material. For the application at hand, I think the thin-pin style isn't up to the task.

In traditional drawer construction, the tails are always added to the side pieces. This is because the mechanical ability of the dovetail joint helps it withstand the stress of the drawer being pulled out thousands of times over the course of the piece's life (foreword stress). It can do this because the tails are wedged-shaped, so the drawer face can't be pulled away, unless, of course, the stress is so great the puller breaks either the tails, the pins or both.

In normal use, a drawer has to endure very little outward stress. The only time this stress direction would effect a drawer is if it is owned by someone like my wife, a lovely lady who loves to stuff 10 cubic feet of clothes in a drawer designed to hold 6, or thinks that they put two drawer pulls on wider drawer faces for looks as any drawer, no matter what its width, can be opened with one pull. Under normal use, however, the long-grain to long-grain glueing surfaces can easily withstand the outward stresses. If a dovetail joint holding a drawer together does give-way, it is either because my wife is using it, or it is a result of glue failure.

The portable vise, however, is a horse of a completely different colour. There will be constant stresses forward on the front joints and backwards on the rear joints, the results of clamping a piece of wood between the two. What also has to be considered, though, is that not all the stock placed in this vise will be square-ended, meaning there will be a considerable amount of stress in the outward direction as well. As the vise is tightened on oddly shaped stock, the stresses will try to rack the vise, putting far more outward stress on the dovetail joint, the one stress direction that the joint is incapable of coping with. These outward stresses can only be coped with by not only the integrity of the glued surfaces, but the integrity of the tails and pins as well.

As this frame is made from 1½" by 3½" stock, two beefy tails will give me enough long-grain to long-grain surface to create a more than adequate glue joint to handle the stresses. If I used the thin pin design, however, I very much doubt that they would be strong enough to handle the outward stresses, resulting in failed joints over time. They wouldn't fail because of problems with the glue, they would fail because the pins would break off. A problem, after all the work I am putting into this vise, that I would rather avoid.

After all this deep thought while contemplating dovetail joints, it is time I headed off to layout some; all with equal sized tails and pins.



Wednesday, 19 February 2014

Boat Anchors Don't Come Cheap...

While searching around the web the other day looking for vintage tools I came across  vintagemachinery.org again, a site that offers up a treasure trove of owners' manuals and other information on, as the name suggests, vintage machinery. While I don't have the interest in power tools that I once had, I did read the owner's manual for my old man's 1949 Beaver 8" Tilting Auger Table Saw, Model CS3200, again, as well as the company's Products Catalogue and some other publications.

The following image is a compilation I made up from the different catalogues...

The "Beaver" brand was the trade name for machinery manufactured by the The Callander Foundry & Manufacturing Co. Ltd. located in Guelph, Ontario, Canada. They started operations in 1917 producing grey iron, brass and aluminum hardware and building items. In 1933, Callander took over a small company that manufactured woodworking tools and added these to their growing list of products. After the war years, a period in which they pretty much produced nothing but military components, Callander expanded their Beaver brand of tools and added some new twists to many of them.

One of their more innovative design additions was a new tilting arbored table saw mechanism that could be produced cheaper than all the similar products produced by their competitors at the time. What they developed was a lighter motor mount that was an integral part of a lighter arbor mechanism, without giving up strength but still allowing it to tilt with the motor. They claimed the new design was as good or better than the existing design, but much, much cheaper to produce.

It was this particular innovation that first caught the attention of the newly formed Rockwell Manufacturing Company. Rockwell was so impressed with this new design, in 1953 they bought the rights to the Beaver brand of tools. In 1954, Rockwell Manufacturing Company came back and bought out all of Callander's remaining assets, rolling them over and into a new company, specifically named "Rockwell International".  It is pretty cool to discover that the largest woodworking tool manufacturing company in the world started out using a Canadian manufacturer as their base.

Reading through the information about this 8" table saw also produced some other surprises for me.

My old man's example of this saw is still my favourite tool, bar-none. Its only drawback was its weight, which I always calculated as being about 80-pounds. Reading now that it actually weighed 147-pounds not only surprises me, but ticks me off a bit as well. I remember being 11 or 12-years old and having to haul that thing from the trunk of the old man's car to wherever we were working and constantly getting shit when I got there because I always seemed to end up hefting it using the fence guides. Discovering the weight of that saw now makes me wonder how I grew up with the ability to talk with a low voice - if you get my drift.

Another surprise was the cost. The list price for this saw, back in 1949, without the stand, was $119.50, which would be equal to $1250.00 in today's dollars. That is a heck of a lot of money for a portable table saw, if you could call it that, especially when the average carpenter plying his trade in Toronto in 1949 would have been making, at best, $1.25 an hour. I have a feeling the old man probably had to forgo his beer for a few weeks to get it. That must have killed him.

Oh, ya. The first woodworking project I ever assisted my dad with was when I was 7-years old. It was a "hot rod" (push cart) for me and every stick of wood that went into it was cut on that Beaver table saw - curves and all. I knew the old man missed it when it came to the proportions, but I didn't care. To me, it was one sweet ride...



Sunday, 16 February 2014

It Just Might Work...Maybe...

This is where my portable vise stands as of this afternoon...

The 16-pieces that make up the meat of the vise are now all drilled, glued up and rough-blocked (that is the term for truing up a car's body panels but is that the correct term for truing up a piece of wood?).

Even though drilling those 32 - ¾" dog-holes was monotonous, it was an easy and relatively enjoyable task doing them on the drill press. I didn't through-drill them, but that might change by the time it is done. While I was blocking it, I found that it was quick and easy to fill the holes with shavings, but getting them out was a real bitch. My original thought was that it would be easier to keep my work area clean with blind holes, which would reduce the spread of crap from getting under the vise. After spending 10-minutes earlier, cleaning out all the holes with a awl before turning it over to work the bottom side, I'm rethinking that one.

Cutting the runways for the two maple stabilizers and the walnut screw was a fun task. I cut slots in the pieces that they run in and used a round plane to cup the surfaces of the pieces that face them to get the width needed. They all slide in and out smoothly and evenly, so I figure I made a good choice regarding how to cut them.

I still have to cut the ends square, but I am going to have to wait for some decent weather so I can do that on the outdoor bench. Cutting stock is a dusty job, too dusty to do indoors. The weatherman is actually calling for warmer, sunnier days starting Tuesday, so the minute the temperature gets close to (or hopefully above) freezing, I'll be out there with saw in hand. I'm going to try that H. E. Mitchell Tenon Saw I purchased recently to cut them, not just because it is a good, heavy backsaw, but because I want to see how it works.

I have shown a piece of 2x4 oak stock to the right of the vise's body which will become its right frame-rail. I bit the bullet and bought new stock for the frame for no other reason that aesthetics. I figured the 1½" by 3½" boards would look a lot better than 2 - ¾" boards glued together, given that the body was glued up with material of that thickness. I am going to keep this material at its 3½" height, but rip some cut-outs along their bottom edges leaving extra material in each corner to act as feet. I think the vise needs feet as I can't count on the work surfaces I will use it on being level. Feet will make it easier to stabilize the vise by sliding narrow strips of cedar shingles under them as required.

I still haven't given up on setting this vise up to use as a shooting board, but I have decided all the shooting board parts will be detachable. The reason for this is I want to add a storage box to hold the bits and pieces the vise will need, such as dogs and clamps, and if everything is connected in one piece, I'll have to rent a crane every time I want to move it. The drawing below shows how the vise will look when the frame is done, showing the where and how of the storage bin...

That's it for now. Catch ya' again when I get the frame done.



Friday, 7 February 2014

Will a Round Peg in a Square Hole Work...

How many of you guys miss new additions to Kari's blog, http://villagecarpenter.blogspot.ca? Damn I miss that girl. I hope she is doing well and still makin' sawdust.

So I got the body pieces of recycled oak stripped on their glue-up faces. It didn't take as long as I expected, but it still took a fair bit of time. I'm not really big on killing myself for my hobby, so when I get involved in boring, physical jobs like this, I'm not one for sticking to it. I do this, after all, for the pure enjoyment and somehow, slugging my guts out for hours on end doesn't quite have that ring to it.

I have done some gluing up with these pieces, making four glue-ups with three pieces each and one with 2 pieces, leaving two other pieces on their own. I decided that putting the entire thing together and then drilling all the holes was more work than necessary, given these pieces are only 24½" long by 3¼" high. I can see dealing with the holes after the assembly is done if your making a 12' bench like Richard is over on The English Woodworker blog (read about it here), but not one that is only going to be 31" long soaking wet.

I spent a lot of time thinking about whether or not square or round holes would make any difference to the function of the screw and two stabilizers and couldn't think of one reason why they wouldn't. I came to the conclusion that as long as they all ran in close-quarters to their holes, whether those holes had square corners or no corners at all didn't make much difference. As a result, the hole for the 1" stabilizers in the two single pieces will be cut with a saw, rather than a drill, and the two-piece glue-up for the 1½" screw will be done in the same way. I will have to plane their facing pieces a bit with a round plane to expand the holes to fit, but again, doing them this way is far more exact than trying to drill 14" deep holes on the true after the assembly is completed.

The four glue-ups of three pieces each are for the dog-holes, a slight change from my original design. Whether these holes are drilled before assembly or after doesn't make a lick of difference to the way the dogs will work, so why not speed up the process and ensure they are square to the top by drilling them all out on my drill press before assemble? Sounds like a plan to me.

I've labelled the pieces here so you can see what they are for.
To ensure that I have a flat, square surface to work from, I planed down the bottom surface on all of them by first wasting material using a No.5 with a convex blade, then smoothing them out with a No.6. This way I'm sure the dog holes will be square and the screw and stabilizers will run true.
This shot shows a bottom surface after making it true
and square, as well as the tools used to do it. All
seven glue-ups have been treated the same way.
I'll get back to you again after I have drilled the 32 dog-holes and cut the three passageways.