Krenov Sawhorses – All Together Now!

Once all the parts were shaped to satisfaction, it was time to put the whole thing together.  I started by boring holes to drawbore the feet to the uprights.  I prefer a brace and bit for both aspects of this job.  For the mortises, it allows me to bore till the point of the auger exits, then reverse and bore from the other side for clean holes on both faces.  For the tenons, I can mark them through the hole in the foot, then easily offset slightly towards the shoulder.  An auger is better for this than any other bit I’ve tried.  It bores where you put it, and doesn’t wander like other bits.

Once the drawbores were prepared, a peg with a tapered point and a liberal dose of liquid hide glue put the joint permanently together.  One of the nice things about drawboring is that no clamps are required, and you can “go on with your rat killin’,” as we say in the South.

At this point, I cut the uprights to final length.  I was going to use a 1″ deep half-lap joint to attach the top stretcher to the uprights.  This meant that 2″ of board width would be taken up with the joint.  Since the top stretchers were 3″ wide, this would leave 1″ protruding above the top of the uprights.  Accordingly, I cut the uprights to a total height that was 1″ shorter than my bench height.

I had originally planned on planing my through-tenons flush with the surface, and had beveled them slightly before assembly to reduce spelching (blowout) when I planed them.  However, once I saw how they looked protruding 1/8″, I decided to leave them as they were.  The problem was that the leftover wedges sticking out made for a rather odd look.  Don’t worry – there’s an app for that.

The first step was to cut the wedges (and drawbore pegs on the feet) flush with the surface.

This, of course, leaves unsightly protrusions that must be removed.

My tool of choice for this is a shoulder plane.  Having the blade flush with the side of the plane allowed me to bring the bevels down flush with the surface of the upright.  In addition, the low blade angle and tight mouth allowed me to work crossgrain on the ends of the tenons with little trouble.

The end result is a nicely protruding tenon with beveled corners.

The last step was to add the top stretchers.  After cutting a 1″ deep notch in the uprights the same width as the stretcher, I put the stretcher in place and marked a corresponding 1″ deep notch in the stretcher.  This is a perfect example of relative measurement.  Rather than using a rule to measure the distance and then marking and cutting, just mark it in place.  This has the added benefit of allowing you to compensate for warped stock, as one of my uprights had done slightly.  When the two were assembled in a half-lap joint, the final height corresponded with the height of my workbench.

The original plan called for finish nails to hold the top stretcher in place, but I decided instead of the more prosaic choice of wood screws.  Hey, this is a working tool, and wood screws make for easier replacement of the top stretcher when it becomes worn.

And here they are, ready to go to work!  The top stretcher matches my workbench, and the bottom once corresponds with my sawbenches.  I’ll probably end up putting a coat of boiled linseed oil on them, but I’m going to leave them plain for now.  Call me lazy.

I hope this has inspired you to make a pair of your own sawbents.  Even if you already have sawhorses, these bring a different utility to the shop.  Keep your eyes peeled, and you’ll see them playing a supporting role in future projects.

Krenov Sawhorses – Through Tenons

With the mortises cut to shape, it was time to turn my attention to the tenons.  As I mentioned in the last article, I planned on 1/4″ shoulders on the ends of the tenons, but only 1/8″ shoulders on the sides.  With a softer wood, I might have needed a wider shoulder, but I wanted to see how a wider tenon would look, and hickory was perfect for this.  The question is, how to cut it?  1/8″ was barely a saw kerf, and handsaws track very badly when the wood on one side of the cut is thin to nonexistent.

This was the place to try my new Veritas skew rabbet plane.  Since only a small amount of material had to be removed, planing would be relatively efficient, and the tool’s 1 1/2″ width would handle my 1 inch-long tenon with ease.  This approach was not without its risks, however.  While the plane is almost 10″ long, the stretcher is only 3″ wide.   The resultant small registration area meant that the risk of mis-shaping the tenon was very real.  Being aware of this, I left the tenons slightly oversize for final fitting.

As you can see, the tenon shoulder is quite narrow.  I honestly don’t think you could do it with a saw.  If you look carefully, you’ll see the number “3” at the shoulder line.  This indicates that this is the bottom face of the stretcher for mortise number 3.  You’ve always been told to mark your pieces – this is especially true for hand joinery, where each joint can (and usually does) have its own unique character.  In this case, tenon 1 would probably not be a good match for mortise 3.

For final fitting, I again turned to my router plane.  This technique, which I recommend highly, allows me to correct for any tilt that might have crept in from using a long plane on a short surface.  It also lets me fit each tenon precisely to its matching hand-cut mortise.  Remember what I said about marking your joints?

For the photographically-minded among you, the unique lighting in the above picture comes from a kerosene lantern.  You can see the edge of its base in the lower-left corner of the frame.  I often use a lantern for spot-lighting on gloomy days.  It also provides a wonderful soft raking light for checking a surface for flaws.

Once the tenons were fit to the mortises, I sawed the end-shoulders on the tenons and sawed the grooves for the wedges.  I’m of the school that bores relief holes at the end of the wedge kerf to minimize splitting.  I realize that this debate is right up there with pins-first, tails first dovetails, but in this camp I come down firmly on the side of the relief holes.  It’s true that the ends of the mortise support the wedged wood, but the very fact that you’ve put a wedge in the wood means that you’ve stressed the fibers beyond the the end of the kerf, giving the potential for the split to run.  Besides, as far as I know, there’s no downside to boring the holes.  If any readers want to weigh in on this, I’d love to hear your views.

Next time, we’ll put the whole thing together.  Stay tuned!

Krenov Sawhorses – A Firm Footing

With all the wood dimensioned, it was time to start the joinery.  I cut the four feet to length and laid out for the mortises at the center of each using a mortise gauge with a pair of spurs.  Having recently read Robert Wearing’s excellent book, The Essential Woodworker, I decided to use a variant of his mortising technique.

After scoring deeply with the mortise gauge, I began by making a series of shallow cuts across the width of the mortise with a chisel using hand pressure only.  In Wearing’s example, he uses the same mortise chisel used to chop the mortise.  However, in hickory, the mortise chisel didn’t work very well with hand pressure alone, so I opted instead for a bench chisel.  The idea is to simply raise the chip a bit, forming a corrugated area proud of the surrounding surface.

Once this is done, simply take the side of chisel and, going against the grain of the raised chips, rake them away.  This leaves a shallow rectangular recess in the surface of the wood.  This is the reason for the deep scores earlier.  You now have a pair of “fences” to ensure that your mortising chisel is properly registered, and doesn’t wander off-line.  The first cut with the mortise chisel is the most important, and defines the rest of the cut.  This technique greatly improves your odds of chopping a good mortise.

In softer woods, I will either begin chopping directly, or bore a single relief hole.  However, in hickory, I decided to bore three relief holes in each mortise.  This extra step was more than repaid when the time came to chop.  I’m not sure my handle would have stood the strain otherwise.  Those of you who have bored relief holes with a brace and auger know how easy it is to get slightly off-center.  Once again, the recess helps by letting you lay the bit on its side with the spurs between the walls, and then stand  it up with the point in place.  It’s not perfect, but it does help.  Then, bang away!

In fairly short order, I had all four legs properly mortised and ready for their tenons.

I left the legs overlong.  This gave me room to repeat a tenon if I made a mistake – the excess is removed once the danger is past.  This is something I try to do whenever possible, and it has saved my bacon more than once.  The tenons were a bit rough, as mine often are.  This time, however, I had a secret weapon:

I had seen Christopher Schwarz finish tenons with a router plane, and had wanted to try the technique.  With a new Veritas model in the shop, my chance had arrived.  The process is fairly straightforward.  Abut a piece of wood the same thickness as your piece against the end of the tenon.  This gives a support to the router, and lets you trim in the same way that you would clean up a dado.  Proceed lightly, alternating sides and checking the fit, and you’ll have perfectly centered, straight-sided tenons.  Of course, this assumes that your mortises are also perfectly centered.  If not, you’ll have to modify the technique somewhat, as I will on the blanket chest project.

I finished up the feet by cutting away a small amount on the underside to make two contact pads on each foot.  This makes for much flatter sitting, especially on irregular surfaces.  A simple 45 degree miter on the top corners finished everything off.  You could, of course, finish them any way you like – ogee, roundover, leave ’em square.  But for me, in the end, it’s just a sawhorse.  I just didn’t want to be stubbing my toe.

Now, the feet are ready to be joined to the legs.  But first, I’ve got to do the through-tenon joinery for the stretchers.  We’ll do that next time.  Stay tuned!

Fabric Push Stick – Brownie Points!

One of the high points of woodworking for me occurs when my wife comes up to me and asks, “When you get time, can you make me a …”.  That happened to me this week.  When I came into the house from the shop, my wife asked me if I could make a “fabric pusher” for her to use at the sewing machine.  We guys love it when this happens.  After a few minutes conceptualizing an item I had never seen, I sprang into action.  Dashing to the shop, I quickly ripped a few 7/8″ turning squares from hickory offcuts from the Krenov sawbents.  Then, I headed to the lathe, dragging her along with me.  This was a no-brainer project for a turner, but I needed her input on shaping.  After a few minutes of collaboration, the object was finished.

“That’s it?” you ask.  Yep.  It’s a simple teardrop-shaped piece of wood that she uses to guide fabric through the sewing machine, as shown below.  It’s especially handy for ruffles and other complicated folded fabric.  It has a simple rounded tip, but she says she may want more later with different tip shapes.  No problem!

I believe these are available through some of the specialty sewing supplies, but when your husband’s a woodturner, why bother?  Besides, a hickory offcut plus a few minutes at the lathe nets a pile of brownie points for me!

After using it for a bit, my wife thinks that the shaft may be a bit thick, and she may want something with more of a teardrop taper.  That’s OK, I left a stack of 7/8″ square hickory by the lathe, just in case.

You can never have too many brownie points.

Krenov Sawhorses – Roughing the Stock

Once the boards had acclimated, it was time to rough-dimension them.  I have learned from hard experience that it’s better to make the initial rip cuts somewhat oversize, especially in flat-sawn stock.  Boards with this grain orientation have a greater tendency to twist or bow when cut, and an oversize piece gives more room to correct this.  Also, I prefer to rough-dimension stock prior to planing to final thickness.  Wide boards often have some cup to them, and ripping them to near-final width means that less wood thickness has to be removed to flatten them.

I begin the process by doing a rough layout of the pieces required for the project, picking the best combination to give good grain, while avoiding any obvious trouble spots.  I’d rather throw some stock away than include bad wood.  Then, I crosscut to workable sizes.  In this case, all the parts are going to be 3″ wide, and I picked stock in excess of 6″.  Since all pieces were paired (I’m making two bents), I could crosscut and get two matching parts from each piece.  Don’t forget to allow some extra length on each piece for later finish planing (snipe) and unexpected problems (end checking).  Life isn’t always this simple but I’ll certainly take it when it is!

The next step is to get one reference edge on the board.  Since these edges are rough, I start with a scrub plane set light, and then finish with the jointer plane.  I’m not worried about a reference face yet – that will come after everything’s cut to rough width.

Now that I have a reference edge, I can lay out my rip cuts with a marking gauge, being extra-generous on this first pass.  This was a good precaution, as you’ll see later.

Now for the hard part, ripping to rough width.  A good, sharp rip saw is worth its weight in gold here.  Mine is a 6.5 ppi Henry Wilson & Sons that I sharpened not too long ago.  A coarser saw, 5 ppi or so, would make things go faster, but this one did well enough.  I used my paired saw benches to support the opposite ends of the board, giving a sawing space between them.  Fortunately, this was short stock.  Any longer, and support of the ends would have been a problem.  Oh yeah, that’s why I’m making these saw bents!

With the cuts completed, the boards go back on the bench for a look.  Yep, as I feared, there was some bowing in some of the pieces.  That will have to come out, but we’ll save that operation for next time.  Stay tuned!

Krenov Sawhorses – Getting Started

One shop helper I’ve been planning to make for a while is a pair of Krenov-style sawhorses, also known as sawbents.  These little work supports, based on a Fine Woodworking plan, are one of the best designs I’ve seen.  Bearing a more-than-passing resemblance to a coat valet stand, they are lightweight, have a small footprint, and are versatile additions to any shop.

I said they’re “based on” a plan.  That’s because these babies are a perfect candidate for customization.  In fact, they require it for maximum utility.  Most of us already have sawhorses of the usual type – I’ve got 10 or 12.  However, their height doesn’t really match up with anything else in the shop.  Heck, the different sets don’t even match each other.  These sawhorses are a chance to change that.  Basically an “H” shape, they have two stretchers – middle and top.  The ultimate utility comes from making the top coincide with the top of your workbench, and placing the middle stretcher at the same height as the top of your sawbench (you have made a sawbench, haven’t you?).  This way, you can support long items at either of your two most common working heights.  Everything else is just a matter of joinery.

Joinery is indeed the centerpiece here.  With properly done joints, it is theoretically possible for each and every piece of wood in this project to be of different cross-sectional dimensions and still arrive at a workable sawbent.  If you’re really adventurous, you might want to give that a try just for the fun of it.

If you’re interested in more detailed information on making this type of sawhorse with hand tools, along with other great projects, Shannon Rogers, the Renaissance Woodworker, covers the construction of the one pictured above in the first semester of his Hand Tool School.  This online subscription video course in hand tool techniques is the only one of its type that I’m aware of, and is a great way to get started with hand tools, or improve your existing techniques.

I decided to use hickory for my version.  It has a high strength to weight ratio, and is relatively inexpensive here in the South.  It is also fairly hard, which complicated my other decision – to do most of the work with hand tools.  I’m fairly proficient in this discipline, but cured hickory will make anyone think hard about this approach.  Feel free to use the tablesaw if you choose.

A trip to the lumberyard procured a pair of hickory boards.  They were flatsawn stock, and not absolutely ideal for this purpose.  However, ask for quartersawn hickory and you’ll get laughed at.  They were twelve-footers so, after a quick mental calculation, I had them pre-cut to five and seven-foot lengths so they wouldn’t hang too far out of my truck.  Yes, I could have taken my handsaw, but they’ve got this HUGE radial-arm saw, and the cuts were free.

After skip-planing the 4/4 boards to expose fresh surface, I set them aside for a few days to acclimate.  Did I use my electric planer for this operation?  Absolutely!  As I mentioned earlier, this stuff is hard, and I’m a woodworker, not a masochist.  I’ll plane to final thickness after rough-dimensioning the stock, which is where we’ll pick up next time.  Stay tuned!

Folding Trivet, Roubo Style

I was thumbing through a catalog the other day, and stumbled upon a folding trivet.  You know, the things you put under a hot pot on the table.  It was made of two pieces of plastic joined together with a pivot in the middle, and was X-shaped when open, but folded flat for storage or carrying.  I thought to myself, “Why not make one from wood?”

Don’t worry, I’m not talking about two pieces of wood with a nail through the middle.  Rather, I’m talking about a single piece of wood, using the knuckle joint loved by whittlers and Andre Roubo alike.  The basic construction is similar to the Roubo bookstand that I made some time back, but on a much smaller scale.  Once you get the knack, these are simple to make and, using nice offcuts, would make great small gifts for teachers, party favors, or what have you.

The process begins with cutting a piece of wood to about 3/4″ x 3/4″ and about 9″ long.  This seems to yield a finished “X” to fit most pots.  Following this, mark the center of the piece all the way around, and then make 45 degree marks to form a diamond on the two opposing sides.  Then, mark lines around the stock at the points of the diamonds.

Next, divide the clear faces into thirds between the outer boundary lines, and shade alternating sections as shown above.  It is crucial that the opposing faces be marked the opposite of each other, or the joint is doomed to failure.

After all the faces are marked correctly (you’re sure, aren’t you?), drill small holes completely through the wood at the intersection of one of the boundary lines with each of the two dividing lines.  This provides a starting point for a saw blade.  Oh, and don’t to like I did and let the nose of your chuck run into the wood – see the circles?  I’m using a deep-throat fretsaw, so the hole is 1/16″.  Saw downwards from the hole to the other boundary line along the dividing line as shown.  This defines the parts of the joint.

Now comes the tricky part.  Using a chisel, remove all the shaded areas.  While this requires some care, it’s much easier that the multiple-knuckled Roubo bookstand.  One way to make things easier is to use a block of wood cut at a 45 degree angle as a guide for the last few strokes.  This is especially helpful on the inside cuts as shown above.  Yes, I know I need to make one more cut on the bottom side – I got it after I shot the photo.

When you finish, the joint should look like the photo above.  Notice that lines have been drawn from the points of the diamonds to the ends of the piece.  These will be the cut lines for your saw.

I used a handsaw for this, but a bandsaw is a better choice if you have one.  I just used my handsaw to stick with the all-handtool theme.  I chose a 12pt crosscut saw instead of a ripsaw due to the fragility of the wood.  Go slowly and carefully, especially as you approach the boundary lines which mark the end of your cut.  This is the point where the magic happens, and the one piece of wood magically separates into two.

Or three, if you aren’t careful.  Actually, the pine for the first prototype wasn’t strong enough to take the stress.  The fact that I could have been gentler with my manipulations certainly contributed to the problem.  However, even if I had treated it like spun glass, the pine was still a bad choice.  I made the second prototype from hickory with much better results.

And now, for the moment of truth.  As you reach the boundary lines, the ends should separate and start to hinge.  If things are sticky, take a close look at all your cuts, and gently tweak things.  Finally, the (now) two pieces will pivot away from each other.  As you can see from the photo above, there are little bits here and there that need to be cleaned up but who cares?  You did it!

And here it is in all its unfolded glory.  Did I hear you say that it looks a little plain?  Bear in mind, this was a prototype to prove the concept.  Though tough, hickory is not the most decorative of woods, and would not be my choice for a production model.  However, there are limitless ways to dress the basic model up.  Exotic woods, curved or sculpted profiles, and decorative carvings are all ways to turn this basic form into something worthy to give as a gift.

Hey, even if they don’t use it for hot pots, they may, like my sister-in-law,  just spend hours playing with the cool joint.

Turning Saw – Putting It All Together

After shaping the frame parts, all that was left was construction of the two handles and the winding toggle shown in the picture above.  Unfortunately, I’m not fond of trying to photograph while using power tools, even the lathe, so I’m afraid you’ll have to settle for my descriptive prose.

The toggle starts life as a ½” diameter cylinder easily made from offcuts from the saw (at least in my case).  The ends are rounded and a cove us turned near one end.  The cove retains the tensioning strings and allows the toggle to pivot when under tension.  After parting off, the opposite end is flattened into a paddle shape.  There were several ways this could be done, but I chose the stationary belt sander as the most expedient – 60 seconds start to finish.  Just hold by the grooved end and press the opposite end to the belt.  Flip and repeat.

Yes, the handles are cocobolo.  I didn’t have any thick hickory, and didn’t care for putting a glue line right in the middle of a knob.  I know the wood is still strong, but it bothers me for some reason.  Besides, I had some leftover turning squares laying around by the lathe.  I started to use mesquite, but found a cocobolo blank that was just the right size.  I grabbed one end in the chuck, bored a ¼” hole for the blade pin, and shaped a handle.  The form is simple, and makes a good turning exercise.  Again, precision is NOT required.  The second one quickly followed.

After completing the handles, the blade pins are glued into place.  The butt end of the pins has a series of concentric grooves connected by a lateral channel – perfect for gluing.  I followed the recommendations and used a slow-set epoxy.  I dribbled some into the holes and then pressed the pins into place.  You might want to have some sort of clamping device standing by if the fit is a bit tight.  That little bit of extra pressure can make all the difference.  This is when you find out what that channel is for.  As the pin presses in, some of the epoxy is squeezed back around the flange in the middle of the pin.  Just be ready with a paper towel and wipe as it appears.  This works better than trying to get all the squeeze-out at once.

My choice for a finish was my usual shop-grade one – diluted boiled linseed oil flooded on and wiped off in two coats.  Simple and effective.

All that remained was to assemble the final product.  The stretcher fits into the mortises, and the blade is hooked into the pins just like a coping saw.  I followed the recommendations for stringing and used 50lb braided fishing line.  It had been a long time since I bought braided line, and I was unprepared for the change.  This stuff looked more like monofilament, than the braided nylon I was used to, and I was more than a little skeptical about it.  After all frame was assembled and the blade was in place, I made four slightly loose loops around the two horns and tied the ends together.  The toggle was placed on the inside of the loops and twisted to tension the blade.

A word here about tension: The notes on the TFWW website are vague about the amount of tension required, and after a bit of fiddling I understand why.  Tension is a very subjective thing.  I’ve been very conservative so far, after reading the dire warnings about the perils of overtensioning.  How much is enough?  I’m not yet sure.  For now, I’m playing with the following numbers:

“Slack” is considered to be the point where, when released from the stretcher, the toggle won’t unwind on its own (about three turns).  “In tension” is five or six additional turns beyond that.  “Overtensioned” is the point where something cracks – something I don’t really want to find.

I’ll spend a little time with the saw, learning its quirks and finer points, and then report back with what I’ve learned.  Till then, I highly recommend that you try one for yourself.  It’s a fun and simple project that yields an inexpensive fix for your saw problem.

What I Screwed Up This Week – December 12, 2010

Welcome back for another edition of What I Screwed Up This Week!  Once again, we’ll be looking at a problem with building the turning saw.

The Problem:

After affixing my templates to the hickory, I went ahead and cut the pieces out without taking into account that I needed to bore pin holes (bottom circles) and chop mortises (upper circles).  This left me in a situation where the pieces would not be properly supported during these operations.

The Solution:

I used cabinetmaker’s handscrews to hold the pieces in alignment during the drilling and mortising.  Handscrews can, when properly adjusted, provide excellent holding power for irregularly-shaped objects, and can act as a flat reference surface when performing operations like drilling.

Lesson Learned:

Whenever possible, plan to do operations like mortising or drilling BEFORE cutting the curves on parts.  It’s often possible to establish flat reference surfaces parallel or at right angles to the area that needs to be worked.  Then, proceed with shaping the piece after the machining or joinery is finished.

Turning Saw – Shaping the Parts

My next step was to bore the holes for the blade pins.  If I had been smart, I would have done this, as well as chopping the mortises, before I cut the blanks to shape.  Since I’m not, I had to use a handscrew clamp to hold the pieces in proper alignment.  That done, I then chopped the mortises for the stretcher, again using a clamp to hold things steady.  The size of the mortises isn’t critical, since they simply align the stretcher.  In fact, they should be a bit oversize to allow it to shift as tension is applied.

The tenon stretchers are a bit more work.  They were cut to length during the rough-out in the previous episode, but now are cut to width, and the shoulders curved to match those of the mortises in the saw cheeks.  I transferred the width with the marking gauge used to define the mortises, but had to adjust the length slightly due to the fact that the cheeks are a bit thicker than the stretcher.  I then sawed down to the tangent of the shoulder with a dovetail saw, and removed the waste by paring straight down with a gouge.  In this case, a #3 sweep carving gouge was perfect.

Now, it was time to shape the parts.  For me, this meant saddling up the shavehorse and breaking out the spokeshaves.  If you don’t work that way, don’t worry – there are plenty of other ways to perform this operation.  The stretcher has a tapered octagonal shape that is easily done with the spokeshave.  Another option would be to make an oval instead of an octagon.  Don’t make a big deal of slavishly copying the pattern here.  The whole point is to lighten the structure somewhat and make it easier to work the toggle.  Go for smooth flowing lines.

The cheeks are a collection of various shapes.  I decided to begin by rounding over the bottom of the cheek where the pin passes through.  To do this, I clamped the piece in the vise and cut facets on the corners with a rasp.  These were then rounded into a semicircle with rasp and file.
The finger rests were then shaped using the round side of a rasp, which makes a perfect indentation, then cleaned up with a half-round file.

A close look at the pattern reveals that the horn end of the cheek tapers to about half its original thickness.  For this, I went back to the shavehorse and gently worked the taper with a sharp spokeshave.  I then shaved as much of the bullnosed edges of the cheeks as possible, then switched to rasps & files for the rest.  This was followed up with a general clean-up and smoothing with sandpaper.  I paid particular attention to the horns, removing any distinct corners and creating a near-oval shape.  This area would hold the string in tension, and I didn’t want any sharp corners causing fraying.

With that, the basic frame pieces were made.  Next time, I’ll touch on making the handles and toggle shown here, add blade pins, and finish.  We’re in the home stretch.  Stay tuned!