Sunday, August 11, 2013

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.