Shaving Horse - The Business End

The swing arm and work platform are the heart and soul of this shaving horse.  The tight tolerances of these two parts prevent the head from racking and simple improvements to the height adjustment mechanism make for a more powerful and easy to use horse.  My previous post, Build a Better Shaving Horse, is a general overview and offers more insight into the design and features of this horse.  This post deals with building it.

My loud associate.

I used a power planer to thickness most of the parts for this shaving horse.  Ninety-nine percent of the time it slumbers silently in a dark corner in the closet of my workshop.  This is not a necessary tool to build this shaving horse, but it speeds up the process.

Work platform components.

I started by thicknessing the center portion of the work platform lamination.  It is important that this piece slip easily into the base, but not be loose enough to wiggle.  The length of this piece depends in part on the thickness of the rails of your base.  It should protrude 3" or so beyond the base rails and 11" (or more) above the top edge of the base.  I started with an 18" length, which left me with plenty of material to trim away in the end.  This piece is 4 1/4" wide.  I cut a relief at the top to give the swing arm clearance to pivot forward.  The relief cut out measures one inch at the top and tapers to nothing over six inches.

The two wider pieces in the photo form the cheeks and shoulders of this giant laminated tenon.  They are 7 1/2" wide and 11" long.  At this width, southern yellow pine boards usually have some cupping.  I completely flatten these pieces before gluing the work platform together.  These giant tenon cheeks also form the channel that the swing arm rides in, and flattening them keeps the tolerances tight in this critical area.  I also make sure the bottom edge of each cheek is square to the front edge.  This is easy to square up before laminating the pieces together, and more challenging to do later.

All glued up.

When you glue up the work platform there are a couple of things to keep in mind.  The pith side of the each tenon cheek should be oriented toward the center.  Flatsawn yellow pine boards this wide will cup a little over time, even after flattening them.  Orienting the boards this way prevents them from cupping toward the swing arm and pinching it in place.  Tenon shoulders that fit tightly to the base rails help to keep the platform assembly from wiggling and walking around in use. This shaving horse will be subjected to more torque, racking forces, and abuse than almost any piece of furniture.  

I carefully align all the pieces as I clamp the laminations together, with particular attention to keeping the shoulders parallel to each other and square to the center lamination.  No matter how careful you are during glue up, the tenon shoulders will probably need some work to get a good fit with the base rails.  A little time with chisels, a shoulder plane, or a table saw crosscut sled should do the trick.

Hole drilled for a wedge.

Once the glue has dried and the cheeks have been fitted to the base rails, I cut the mortise for the wedge that secures the platform to the base.  I start by scribing a line along the underside of the base rail with the platform in position on the base.  Then, I drill a 5/8" hole, centered on the tenon, and just touching the line.

Wedge mortise squared and tapered.

I square the hole with a chisel, making sure to remove extra material from the top of the mortise wall so that it doesn't prevent the wedge from bearing against the bottom of the base rails.  I like to use wedges with a six degree taper.  They lock tightly with a couple of taps of a drawknife handle.  The bottom wall of the mortise is cut at a corresponding six degree angle.  The dimensions of this mortise are not critical.  Get the angle close and size the wedge to fit the mortise.

Six degree wedge.  Use a hardwood.

See the marks from the mortise endgrain?

If you look closely at the picture above you will see the indentations that the leading edge of the mortise made on my wedge as I drove it in.  That means that my wedge taper is fatter than my mortise taper.  I use a handplane to micro adjust the wedge's taper until I see even indentations from the entire length of the mortise endgrain.

Tenon cheeks and wedge fitted.

The top of the work platform assembly will get more attention later.  For the moment I'll move on to the swing arm.

My screaming companion returns!

My rough swing arm was 32" long by 3 1/4" wide.  With the work platform wedged to the base, plane the swing arm to fit the channel in the lamination.  Proceed slowly.  The swing arm should slide easily without binding in the channel, wiggling should be minimal.

Layout for adjustment pin holes.

The height of the head is adjusted by a pin that fits into a series of holes in a groove on the swing arm.  The groove should be on the same side of the horse as your dominant hand when seated in the working position.  Lay out a line two inches down from the top of the swing arm and wrap it around the workpiece.  This line will become the tenon shoulders that the head will rest against.  With a combination square or marking gauge, lay out a line 7/8" from the front edge and 6" long that begins 3 3/8" below the shoulder line.  From the beginning of this line mark center points every 9/16".  Drill a 1/4" hole at each of these points.

Holes drilled.  Groove grooved.

With the holes drilled, it is time to cut the groove that keeps the pin aligned while you are changing the height of the head.  I used a Stanley No. 50, which is not designed for cutting stopped grooves.  I removed the remaining humps in the ends with a 1/4" chisel.  Use whatever does the trick.  In a pinch you could do it all with just a 1/4" chisel.

Back to the platform.

Work surface mocked up.

It's time to make some decisions about the height of the finished work surface.  My work platform is 10 1/2" from the top of the base rail to the top of the platform at the leading edge, and the platform is sloped at 7 degrees.  I'm pretty short, 5'5", so if you are much taller you may want a taller platform.  Before you cut the angle on the top of your laminated tenon assembly, don't forget to subtract the thickness of the platform piece that you will add later.  My platform piece was 1" thick, so the leading edge of my laminated assembly is 9 1/2" from the top of the rail, which gives me a platform height of 10 1/2" at the leading edge.

Cut the slope on the top of your laminated assembly.

Clearance for the swing arm.

Next, hold the swing arm in place so that there is at least a 3/4" gap between the back of the center lamination and the front edge of the swing arm.  This gap gives the swing arm clearance to pivot forward.  Mark a line that is centered on the groove.  Carry the line down the side of the cheek one inch and make a mark at that point.

Laying out the hole for the adjustment pin.

Drilling the hole for the adjustment pin.

Use a drill press, mirrors, or a couple of squares to drill a 1/4" hole through the tenon cheek at that point.  My drill bit wasn't long enough to drill across the channel and into the other side on my drill press.  I chucked the very end of the bit in my cordless drill and used the first hole as a guide to drill 3/4" into the opposite side.  The better the alignment of the holes as they are drilled, the less fussing to get the pin to fit later.

Holes aligned.

I like a low profile shaving horse head.  This makes it easier to reach over the head to work on the other side of the swing arm (especially useful for spoon carving).  Because I am working with dimensional lumber in this design I needed to laminate a piece for the head to get the 1 3/4" thickness that I wanted.  But before I laminated it I cut the mortise all the way through one piece.  This makes it easier to shape the mortise and get a good fit with the tenon.

Laying out the mortise on the head.

The head is 6 1/4" long and 4 1/8" wide.  The joint that attaches the head and the swing arm is a bit odd.  The mortise is oriented across the grain, with endgrain forming the two long sidewalls of the mortise.  This has some downsides from a joint strength perspective, but it has to be this way to keep the head as low profile as I want it.  I have been using my previous shaving horse for 3 years and the joint is intact.  Curtis Buchanan has been using a shaving horse that I built like this for him for the past year and his is intact.  And any shaving horse in Curtis' shop gets a workout.

Bulk of mortise waste removed.

The mortise is 5/8" wide with a 3/4" haunch on the back edge.  I remove the bulk of the material on the drill press and then square up the sides and ends with chisels.  This is a through mortise until I laminate another piece for greater thickness on the other side.  I take advantage of that and work from both sides to make a very clean, precise mortise.

Ends squared up and sides cleaned.

Tenon cut.

Cut a 5/8" tenon with a 3/4" haunch at the back edge on the top of the swing arm.  Because the grain orientation in this joint is a little funny, I feel it is important for this joint to have an exceptional fit.  Don't rush this part.  When the joint is fit up, cut off any of the tenon that protrudes through the head.  I scribe a line around the tenon and cut to the inside of the line to leave a little space for glue.

Joint fit up with steel pin above that will lock the tenon in place.

Laminating the head.

Even though I only needed to add a 1/2" to get the head to the thickness I wanted, I laminated a full 1 1/2" piece.  The extra thickness acts as a caul and distributes the pressure of the clamps more evenly along the glue surface.

1" yellow pine for the treadle and platform.

While the glue in that lamination is drying  it is a good time to take care of a couple of odds and ends that will finish out the build.  I use 1" thick pine for the platform top and the treadle.

The platform top is 6 1/4" wide and 8 1/2" long with a cut out for the swing arm.  I like the platform top to overhang the laminated portion a little in the front and the back, just for looks.  Two 3" long screws hold the platform in place.  I have a stash of leather that I bought a few years ago in Tennessee at a flea market that I like to glue to the top of the platform to prevent workpiece denting.  This is good stuff.  Pete Galbert has found that vegetable tanned leather is a little too slick.  Jameel Abraham, of Benchcrafted, recommends using suede on vice chops.  Since he is the reigning king of workholding, I would wager that suede is a good choice.

Treadle tenon.

The treadle has a 5/8" mortise that slides onto the bottom of the swing arm and is secured with a wedge.  The distance from the bottom of the head to shoulder for the treadle is 27 3/4" on the front edge of the swing arm.  The treadle shoulders are cut at 10 degrees.  The process for cutting and fitting the wedge is the same as for the wedge that secures the work platform to the base. 

Treadle top.

Treadle bottom.

The treadle is 8" wide at the front edge and 3 3/4" wide at the back.  Total length is 13" and the distance from the back edge of the treadle to the back edge of the mortise is 1 3/4".

Joint complete.

Back to the head!  Once the glue has dried saw or plane the head down to 1 3/4" thick.  Test fit the tenon again and make sure that it is not too long.  Trim if necessary.  If you leave the front corner of the head square a couple of things will happen:  the corner will crush immediately and it will dent the carefully shaped workpieces that you put in the jaws.  I like to cut a rabbet on the front edge and add some kind of padding to eliminate the denting.  In the past I have used thick leather, which works great.  But I wanted to try something different for this shaving horse.

Rubber insert.

I bought some nonmarking neoprene rubber from McMaster-Carr to try.  It was 1/4"  thick and I left it 1/16" proud of the wood.  It is superglued in place.  The rubber holds like crazy!  No spindles slipping out of these jaws and knocking the wind out of you.  But unfortunately it is too soft (50A) and I would prefer something less squishy.  I'll order some harder neoprene rubber in the future and give that a try.

Another option to reduce denting is to radius the leading edge of the head and glue some suede in place.  If you try this, I would love to hear your impressions.

Gluing the head to the swing arm.

Next up, joining the head and the swing arm.  I used the cut off from the bottom of the swing arm as a caul to give my clamps a good bearing surface.

Layout for the steel pin.

Once the glue has set up, I pinned the tenon in place with a piece of 1/4" steel rod.  The rod passes all the way through the tenon and into the front portion of the head.  I like to make the pin as long as I can without it popping through the front of the head.  The pin is centered on the swing arm to assure that it passes through the center of the tenon.  I drilled the hole a 1/2" up from the shoulder of the joint.  Precision is important in this operation, so that you don't drift and drill through the side of the tenon.  Use mirrors or whatever you need to keep your bit as straight as possible.  I used my drill press.

Drilling for the pin.

Make sure the hole passes all the way through the tenon and into the front of the head.  The pin is crucial to the longterm strength of this joint.

Steel pin driven home.

I am fairly confident that a good hardwood pin would be functional in this application.  But then you wouldn't have that shiny little chamfered pin on the back of the head to look at.  Whew!  I love the way that looks.  The pin is glued in place.  Epoxy is the best choice.  I had superglue on hand.

Filing the adjustment pin to fit.

If you have ever tried to fit cold rolled steel rod through a hole that is nominally the size of the rod, you will know that it doesn't always work out.  Sometimes the surface of the rod is uneven and the stated dimension can be over or under sized.  Precise, it is not.  Inexpensive and widely available, it is.  I file the 1/4" rod to get the fit that I want.  The process for changing the diameter of the rod is the same that I use to whittle a windsor chair spindle.  Long light passes with the rod rotated a small amount after each pass.  Test fit with the swing arm in place until you have a nice smooth action that does not bind.

Marked for bending.

I like to bend the end of my adjustment pin around which helps to keep it from sliding out as I work.  Locate the bend by inserting the pin into the work platform as far as it will go.  Make a mark 1/2" out from the surface of the wood.  Make a mark that won't disappear when the rod is heated.  A propane or MAPP torch provides plenty of heat for bending stock this small.

 

Bending the adjustment pin.

Heat the rod and bend it at the desired point.  A metal machinist vise, which I don't have,  is the tool for this job.  I found that I could clamp the rod in the underside of my saw vise.  I don't think I damaged it.  Heat the rod in the open air and only clamp it when the section that you want to bend is glowing.  Pull up the bar fast for a nice, tight curve.  Plenty of extra length makes this easier.

First bend.

I didn't get any pictures making the second bend that wraps the pin back around.  Probably because my bending setup was so lousy and I was fighting it the whole time.  The second bend is easy if you have a good metal vise or more ingenuity than me to make do with what you do have.  The second bend is another 90 degree bend, 1" down from the first bend.  Cut off the rod 3/4" from the second bend.  Here is the pin in place on the horse.

Hole layed out for end of pin.

Looks better than a straight old pin, right?  Drill a 1/4" hole to house the end of the pin.

Adjustment pin in place.

Only the seat remains.  I carved a prototype stool seat.  I can't advocate for a comfortable shaving horse seat strongly enough.  I find sitting on a plank or sitting on a bicycle style seat for hours unbearable.  My butt hurts just thinking about it.  I recommend using whatever tools you have to play around for a little while and carve a seat.  Try a shape or an idea that you saw somewhere or that has been bouncing around in your head.  Curtis Buchanan uses sack back seats and Pete Galbert uses stool seats.  Both are comfortable.  Treat yourself.  Hopefully you will be spending many, many hours on that seat.  If at any point you start to develop calluses on your butt (seriously, I have had butt calluses from terrible shaving horse seats), stop whatever you are doing and carve a comfy seat.  You will never regret it.  This little seat took me half an hour to carve, and I had a blast doing it.

Prototype stool seat.

Fin and risers for forward tilt.

I screwed a fin to the bottom to slide between the base rails.  I also added a couple of riser blocks to tilt the seat forward a little.  I find a level or slight forward tilt to be a comfortable working position.  The seat completes the horse.

Now, on to more pressing tasks!  Like shaving a small mountain of adze handles.

Frankenstanley

I've been turning a large batch of handles for the reamers that I make over the course of the past few days.  To accurately size the portion of the handle that locks into the body, I use a rounder plane like the one pictured above.  My rounder is made from a block of wood and a Stanley frog and blade assembly (á la Pete Galbert) from an old handplane.  It works great, precisely creating the joint that I need time and time again.  While this seems like an intuitive assembly to put together, it can be tricky to get it to work properly. 
The first one that I made required so much force to turn the spindle through the cutter that it tore up my hands and aggravated my forearms every time that I used it.

When cutting with gouges and skew chisels on the lathe it is important to present the edge of the cutting tool with minimal clearance of the bevel.  This ensures that you are cutting and not scraping the wood away, which tends to leave a better finished surface and reduce resistance to the forces of cutting.  The same principles apply to rounder planes.  The cutting edge should be presented to the workpiece at an angle just high enough to prevent the back of the bevel from rubbing.  In the picture below the blade has a 30 degree microbevel, which means the iron must be bedded at an angle slightly greater than 30 degrees to prevent the back of the bevel from interfering with the cutting action.  In this example the iron is bedded at 35 degrees.

Note the low clearance angle of the bevel.

The low clearance angle reduces the effort needed to cut the spindle.  If you have ever used a low angle block plane (especially on endgrain) you have probably noticed how it seems to slice through the fibers with less effort than planes with blades mounted at higher angles (typically 45 or 55 degrees).  Keeping the angle of attack as low as possible in a rounder plane translates to faster work, less effort, and forearms that won't be screaming at you when you pick up that third chair leg to cut the tapered tenon on top.

5/8" hole.

With this knowledge, the process for making a successful rounder plane is straight forward.  Start with a block of wood roughly six inches long and as wide as the blade you will be using as the cutter.  Drill a hole the size of your finished spindle or the top of your leg through your block and ream the hole to the desired profile.  My example is a 5/8" hole with a six degree taper in the first 3/4" of the hole.

Reaming taper in the first 3/4".

I do the reaming for holes like this by holding the reamer in one hand and the workpiece in the other.  The only reference you have to be sure you are going straight is that the end of the reamer coming through the hole remains centered.  I actually watch that end as I turn the reamer to make sure that I stay centered.

Reamer centered as it exits the hole.

With the hole reamed to the finished profile, remove all but the last sliver of wood above the hole.  I use a bandsaw and fence to remove the bulk of the waste.

Bulk of wood removed.

And finish by planing off the last sliver of wood until the hole just begins to show through the surface, as pictured below.

I trim the last fragments of wood from the opening with a knife or saw.  If you have ever made a wooden handplane this begins to look a bit familiar.

Place the frog on the surface of the wood.  Note that if you tilt it up so that the front portion of the frog sits level on the wooden block, the blade protrudes into the hole instead of resting at a point on the circumference of the hole.  The frog must be tilted back, which simultaneously pulls the blade up out of the hole and lowers the clearance angle, as addressed above.

Blade extending into the hole.  Frog must be tilted back.

The standard angle frog positions a plane blade at 45 degrees to the sole of the plane.  For my purposes I want the blade to be bedded at 35 degrees.  That means that I want to subtract 10 degrees from the existing 45 degree frog, to achieve my 35 degree bed angle.  To permanently adjust the bed angle add an angled riser block that tilts the frog 10 degrees back.  Cut a 10 degree wedge the same width as your frog, with a maximum thickness of about 5/8".  Smooth the top and bottom surfaces of the wedge with a handplane and position the wedge on the block underneath the frog with the blade assembly roughly centered on the opening.  To properly fit the riser block, saw off the front of the riser in 1/8" increments (or less) until the elevated machined portion of the frog sits flat on the wedge shaped riser block as pictured below.

Frog properly seated on riser block.

One clamp provides enough pressure to glue the riser block in place.

Riser block glued in place.

After the glue has set up reposition the frog on the block.  If the frog rocks back and forth, fine tune the bedding surfaces with a plane to remove the offending high spots.  With the frog solidly bedded remove the blade assembly and mark the holes to attach the frog to the block.

Holes marked for drilling.

Drill a few test holes to find the appropriate pilot hole size for the screws that originally attached the frog to the plane's sole (3/16" worked for mine).  The holes should be drilled square to the sloping surface of the riser block.  I drilled the pilot holes on the drill press by shimming underneath the block until the sloping riser block was square to the drill bit.

Pilot holes drilled.

Attach the frog to the block.

Frog in place.

My default method of problem solving is heavy on the math.  I love calculating angles and using trig functions to describe the details of what is happening on my workbench.  The first time I made I tried to walk down the geometry road to figure out the ideal shape of my blade in relation to the bedding angle.  My thoughts went something like this, "If I grind a 6 degree taper on the last 3/4" of the blade and the blade is bedded at a 35 degree angle, the assembly will actually be cutting a taper of...."  After about five minutes down that road my brain exploded and I switched to a trial and error approach to blade shape and position.  You will know if the assembly is not working right.  Try to figure out where the spindle is binding or why the blade is cutting to much.  Play around with the depth of cut adjustment, amount of skew, and blade shape.  Also, move the frog forward and back until you find a sweet spot where the assembly cuts the desired shape and the amount of force necessary to turn the wood through the cutter does not tear apart your hands and forearms.

Test piece.

For joints that have a taper and a straight section you will need to grind the blade to the appropriate profile.  For joints that are a straight taper you will have to attach the riser block at an angle (it should be half the angle of your total taper) to appropriately position the blade.

Blade with tapered and straight sections

Once the frog and blade are properly set, the rounder produces repeatable, perfect joints.  I turn my reamer handles very close to their finished size and remove just the last, little bit of material with the cutter.  This produces the cleanest results and it minimizes the wear and tear on my forearms.

Perfect joints every time.

Shaving Horse Base

The base of a shaving horse has to be solid.  I prefer a base made of a laminated beam with three legs glued and bolted in place.  It is stout and the three legs sit firmly on uneven workshop and porch floors, even outside.  The base can also be built using the same construction as a Windsor chair; a solid plank with turned legs and tapered mortise and tenons to join them.  If you have already made chairs this base is faster to build.  Jameel Abraham's shaving horse built to Peter Galbert's design is a good example of this construction.  If you choose to go this route I recommend making the leg tenons substantially beefier than chair leg tenons and starting with a plank that won't flex along its length in use.  If the plank can flex it will creak, moan, and trot across the room as you work.  Not a desirable trait for this type of horse.

For this tutorial I am building the laminated beam style base, but the clamping mechanism can just as easily be used with a plank base, or as a retrofit to an existing shaving horse.

My shaving horse.

Construction begins with a 16 foot southern yellow pine 2x10.  With thoughtful layout this is enough material for the entire shaving horse if the wood is nearly perfect.  I used to live in North Carolina and eastern Tennessee, where yellow pine lumber is cheap and abundant.  I live in Maine now and yellow pine is much harder to come by.  OSHA walkboards can be a good source of yellow pine if you live outside of the southeast and are willing to pay more than construction lumber prices for it.  The upside is that all of the walkboards that I looked at were nearly perfect.  That means no digging through the pile for that one perfect board.  The cost would be prohibitive for building something like a workbench, but when only one board is needed the walkboards fit the bill for me.  You'll have to go to a lumber supplier or quality building supply as the big box stores don't carry them.

The laminated base consists of two rails at least 3" wide and 54" long, and two spacer blocks the same width as the rails.  The rear spacer block is 6" long and the front one is 3" long.

Parts for the base.

The rear legs are 2 1/2" wide and 24" long.  They each have a 20 degree angle cut at their tops, which gives the rear legs their splay.  Lay out the angle so that the top of each leg tapers to a 1" width.  

Rear legs.

The shape of the front leg is slightly more complex.  The leg rakes forward at 25 degrees.  The front edge of the leg is 20" long.  Lay out the 25 degree angle that forms the top of the leg and the same angle that forms the bottom of the leg.  Make a mark along the angled line that forms the top of the leg 4 3/4" from the edge, and a mark on the angled line that forms the bottom that is 2" from the edge.  Connect these two marks to complete the shape of the front leg.

Front leg.

The front leg is wider at the top to allow greater offset for the two bolts that will hold it in place.  If the bolts are directly in line with each other they will provide little resistance to the racking forces on the front leg.  Like this:

The reason to glue the front leg in place and offset the bolts.

That third bolt stopped the movement, but it isn't exactly an elegant solution.

Base glue up.

Glue up the rails and the two spacer blocks.  I squared and jointed the top edges of the rails prior to glue up, but you can even things out later if you are so inclined.  The leading edge of the front spacer block should be 14" from the back edge of the front leg to provide clearance for the swing arm.  I glued the front leg in place after the spacer blocks so that I could take the time to get it aligned to my liking.

Counterbore for the bolts.

With the leg glued in place I layed out the bolt locations on both faces of the base and drilled the counterbores to house the heads and nuts of the bolts.  The hole locations are located 1" down from the top edge and 1 3/4" from the back edge of the top of the leg, and 1" up from the bottom edge and 1 1/2" from the front edge of the horse.  I drilled the counterbores to a 1/2" depth and used 4" by 3/8" bolts.  

Completing the hole by drilling through from the second side.

I drilled the through holes with a long 7/16" twist bit, from both sides.  Look close and notice the pencil lines across the top of the shaving horse.  Those are the lines that I used to carry the layout for my holes from one side of the horse to the other.  I also used them as a reference to sight the long drill bit with.  For each hole I drilled halfway through from one side, then flipped the horse around and drilled from the other side to complete the hole.  The drill bit is 1/16" larger than the bolts used and the play of the bolt in the hole usually compensates for inconsistencies in drilling.  Usually.  

There are a few of other techniques one could use to drill these through holes, either with increased visual aids for lining up the bit or using the drill press.  This technique requires no set up and it makes the whole process feel like a game to me.  I get to see how well I can line up each of the holes.  When I am building things for my shop I can take greater risks than when I am building things for a client.  I like to use these opportunities to develop my eye and my skills.  Plus, my drill press table is too flimsy to hold this much weight.

The washers for 3/8" bolts fit perfectly in 1" holes.  If there is misalignment in the bolt holes sometimes it is necessary to grind the washer or remove some wood with a gouge to get the bolt to come through the center of the washer.  Another option is to drill the counterbores at 1 1/8" to provide more play in the location of the washers.

Rear leg dado.

The rear legs fit into a 1/2" deep groove.  The front edge of the groove should be 1/4" back from the front edge of the spacer block.  The groove is raked back at an angle between 10 and 25 degrees.  The rake is just for looks, as it would be challenging to tip over backwards on this thing.  You can have more rake if you like the way it looks or less if you have Victorian moral sensibilities.  Actually, the legs on the horse that I am building are only raked back at 10 degrees.  It doesn't look quite right to my eye.  My previous horse has the legs raked back at 25 degrees, which looks like a bit too much to me.  Something in the ballpark of 15-20 degrees probably looks best.  Pictures.

10 degrees.

20 degrees.

I cut the rear leg groove with a handsaw and a router plane.  It could just as easily be cut with a saw and chisels or an electric router.  The rear legs should fit tightly in their grooves which prevent them from racking.  The grooves also help to temporarily hold the rear legs in place for drilling.

Rear leg fit up.

When you fit the rear legs in their grooves make sure that they seat all the way down and do not rock

The layout and drilling of the rear leg bolt holes is the trickiest part of getting the base together.  My advice is to do careful layout and then don't think about it too much and drill the holes.  My friend Zac Ispa-Landa recently came to build a shaving horse with me and I spent a few hours trying to dream up a new way to do this drilling that was simpler and more controlled.  All that thinking just made my head spin.

I use the square cut on the end of the legs as a reference surface for laying out the hole locations.  With the legs clamped in the angled grooves only the front inside corner of each leg will be flush with the top of the rails.  The holes are centered on the leg and 1 1/8" and 2 1/2" from the top edge on center.  These distances will change a little if you are angling the legs more than 10 degrees.  You want to end up with close to 1/2" of wood above the top edge of your hole after you  trim the tops flush with the rails.

Zac drilling the rear legs.

Before clamping the legs in place draw a square line from the center of one groove to the other to use as a sighting aid.  Clamp the legs in position leaving enough room above the clamps to drill the top holes.  For the angled counterbores I use a 1" spade bit in a cordless drill.  It is helpful to have a friend or a mirror to help align the elevation of the bit.  Use the line across the top as a sighting aid and drill in until the flat surface created by the drill bit is approximately even with the vertical plane of the outside of the rails.  Stop and check a few times until you have it.  After both counterbores are drilled use the long 7/16" bit to drill through from both sides.  If your bolt won't go through wallow out the hole with your drill bit, or anything else you can get in there until it does.  If you have a 1/2" twist bit you can also chase through the original hole with one of those to give the bolt more clearance.  If the bolt slides right through, pat yourself on the back and count your blessings.

Tighten the bolt and remove the clamps to drill the lower hole.  Follow the same process except the depth of the counterbore is 7/8" on the bottom edge of the hole.  The upper bolt is 4 1/2" long and the lower bolt is 5 1/2" long.

Legs trimmed.

Trim the tops of the legs flush with a saw and a block plane and trim the end of the beam to even it up.

With the legs assembled the base slopes forward considerably because the rear legs are overly long.  To get the base to sit properly it is necessary to level the legs.  The goal in leveling the legs is to have the tops of the rails 18" from the floor after trimming the bottoms of the legs.  My workbench isn't long enough to level the legs on, so I had to level them from the floor.   Using a tape measure or framing square and a few blocks and wedges, I leveled the base from front to back and side to side.  The measurement from the floor to the top of the rails should be the same or very close wherever you check it along its length.

After inserting blocks and wedges to level the tops of the rails, the distance from the floor to the top of the rails should be greater than 18".  For example, lets say the rails are 22" from the floor (this number is arbitrary, just for the purpose of example).  To bring the rails down to 18" from the floor I would need to lower the tops of the rails by 4" (22" minus 4" equals 18").  To do this you have to scribe a line around each of the legs 4" above the floor.  Enter simple scribing tool.

Simple scribing tool.

The scribing tool is just a block of wood with a clamp holding a pencil in place.  The pencil needs to be clamped firmly enough that it will not move.  The point of the pencil is set to the desired height, in the case of the example, 4 inches.  Then pressing the block of wood against the floor, trace around all of the legs.  When the bottoms of the legs are sawn to this line the top of the rails will sit 18" from the floor.

Base complete.

Seeing this nice clean base next to my shaving horse made me realize just how much abuse my horse has taken in the three years since I built it.  It shows wear and tear, but it still has a long life ahead of it in the workshop.  The new shaving horse is for spooncarving in my apartment in the evenings.