Friday, January 26, 2018

Shaker Two Step Stool, Part 1: Design Considerations

A neighbor is having their kitchen renovated, so I asked if I could get the solid wood from the cabinets that were getting ripped out.
A whole bunch of red oak
I got the wood from all the face frames and the drawer fronts.  It takes a bit of work to make this wood usable, but hay, it's free wood.

I've been wanting to build a Shaker two- or three-step stool for a while.  I got some ideas on a design from an image search and came up with this.
The overall design
There are so many questions to answer when designing something.  I start from function.  I wanted a step stool about 18" tall to help get to some higher shelves in the garage.  So the first step is at 9" and the overall height is 18".  For the overall width, I chose 15".  This is the same width as some simple four-legged (staked?) stools I've been making and is plenty wide for me to place two feet side-by-side comfortably.

I've read that Shaker step stools were meant to be used directly against a wall.  Such stools were vertical at the back.
Typical Shaker step stool with straight back edges (3-step version)
Since I wanted to be able to use the stool away from walls without it tipping over backwards, I added a slant to the rear edge of the sides.  I matched that angle on the front edges.
Slanted back edge and matching slant on front edge
If the front edge of the side extended up to 18", the total span of the top step would be 12".  At the bottom, the distance front to back is 16".  So I have a 2" deviation in 18 vertical inches at both front and back (if that makes sense).  This slant turns out to be an angle of 6.3°.  The angle wasn't really important - it just needed to look like I wouldn't risk tipping it backwards when I'm on the top step.
Side dimensions
There's an interesting thing about this.  The front edge of the top portion of the side is dead center of the design.  You can see from the picture that the base is divided up evenly.  I intended to do this, but the undesired effect is that the first step is 7" deep whereas the top step is 6" deep.  I think I'd like them be the same.  I might feel a little safer with deeper steps, but I didn't want this thing to have too large a footprint.  I'll use a prototype to make sure it feels OK.

I wanted to dovetail the steps and sides together and needed to decide about dovetail layout.  But I also wanted a rail under the front of each step, so I couldn't have a half-pin at the front and back ends of the side boards.
Upper step dovetail and cross-rail layout
At the front and back of the step are "half-tails".  I needed to have a tail at front to rest on the cross-rail.  And I added one at the back for symmetry.  I played with the dimensions a bit before deciding on a four-tail design, with the two middle tails being a bit wider than the front and back tails.

I used a similar layout on the lower step, just each tail was 1/4" larger since the lower step was 1" deeper than the upper step.

The two front cross-rails will have their lower edges dovetailed into the sides.  The shoulder of the dovetail will add a bit more resistance to racking than if the rails were not dovetailed.  There's a bit of added complexity for the lower front cross-rail - it fits into an angled edge, so it's upper edge will need to be beveled to mate well with the underside of the step.
Upper cross-rail detail
There will be a cross-rail in the back for even greater stability.  It will be dovetailed into the sides as well.
Back cross-rail detail
I was not too particular about the vertical location of the back rail.  I ended up placing its top edge about even with the top of the first step.

One of the last things I considered was the arch cutout on the sides.  I didn't want the feet to be too wide or too small.  But the main thing I was concerned about was the amount of wood keeping the right half (lower step portion) attached to the left half (upper step portion) of the stool.  I think that's the weak point in this stool design.  If the wood is going to fail, it's going to fail just above the center of the arch.
Original arch detail
At first, I laid out the arch as a full semicircle.  That made the arch 5" high, leaving only 3 1/4" of wood above the arch keeping front and rear portions of the stool together.  So I dropped the arch down to 3 1/2" high to add 1 1/2" more wood above the arch to help keep the stool together.
Arch detail
As an added benefit, I think I like the lower arch shape better.

So much for the design.  Next time I'll go over the prototype build.

Friday, January 19, 2018

Making an Undercarriage for a Stool

I've been making a bunch of step stools lately and I wanted to try putting some connecting rails between pairs of legs and a stretcher connecting those rails.  I'm collectively calling the legs, rails and stretcher the "undercarriage".
The undercarriage of the step stool I'm making
This is something new for me.  I've never done this type of work before, but I hope someday to try chairs that have a similar undercarriage.

This is not too complicated, but there are a few things you've got to be careful about.  I'm mainly concerned about the angles used to drill into the legs for the rail tenons.  I'll get to that in a bit.

The first step was to find the vertical location for the connecting rails.  So with the legs dry-fit into the top, I turned the stool over and measured to mark each leg a consistent distance from the underside of the top.
Using a combo square to find the vertical location of the rails
About 5 1/2" got me to the fattest part of the legs
I used a rubber band strung between pairs of legs to help me find the dead center for drilling.
Marked a location midway between rubber band strings to get "dead center"
Then I had to figure out at what angle to drill the holes.  To do this, I used two bevel gauges.
First bevel gauge gets the rake (or is that "splay") angle
Second bevel gauge records the splay (or is that "rake") angle
I marked a line on my benchtop at the angle of the first bevel gauge and lined up the leg along that line.
Leg in a "cradle", leg is at the angle of the first bevel gauge
Then I set the second bevel gauge up next to the leg to guide drilling.
Drilling at the angle of second gauge
But the trick here is that I have to lean the drill not only at the angle of the second bevel gauge, but also perpendicularly towards the front of the benchtop to account for the first angle.

The stretcher that connects the two rails didn't need any special angles.  Just straight 90° drilling into the rails.  I'm sure there are other ways to work out the angles for drilling the legs, but this worked for me.
Undercarriage dry-fit
Here's what it looks like right-side-up
BTW, the legs, rails and stretcher were made without a lathe.  They're not perfectly round in cross-section, but It's amazing what you can do without a lathe (though I hope to build one this year).

The strength that the undercarriage adds, compared to a stool with only legs, is remarkable.  After gluing, this stool is so much more rigid than any others I've made.
And here she is all gussied up
Just a couple of notes here.  First, my tenons were 1/2" and seemed quite small and possibly weak.  The legs are about 1 1/4" diameter where the rails are mortised in, so I could (should?) have used 5/8", or possibly 3/4" tenons.  The rails are 1" diameter where the stretcher is mortised in and I think 5/8" tenons would have been better.

Second, the glue up was interesting.  Even though I had my legs and all parts numbered and did a couple dry-runs, I still put a leg in the wrong hole when gluing up!  Fortunately I was able to knock it apart and get it right.  The order of gluing was as follows: stretcher to rails (a tad loose), rails to legs (a little looser), then legs to top.  You need to have the undercarriage joints a little loose so there is some flex - otherwise you can't bend the legs enough to get them all in their angled mortises.

Comments and suggestions welcome!

Friday, January 12, 2018

Sharpen an Incannel Gouge - The Cheating Way

Bob Rosaieski often talks about the use of incannel gouges.  In November at a tool show I found two of them for sale and picked them up fairly cheap.
The two new (to me) incannel gouges ($30 for both)
Smaller one is approx. 7/8" wide, larger is 1 1/4" wide.  Don't know the "sweep"
but the smaller has diameter approx. 15/16", larger approx 1 3/4"
Smaller one is a Buck Brothers
Larger is Marples
I thought for a long time about how to sharpen them with the equipment I have, which mostly sharpens flat blades.  The following pics are from sharpening the Buck Bros. gouge.

I started by using the hand-crank grinder to create a flat one the end, removing any chips or unevenness.
End-on view, showing the flat created at the edge
Got it reasonably straight across - I don't think you want a curve on these gouges
Clamped the gouge in the vise at a 25° angle
A year or two ago I bought a cheap Dremel tool at a garage sale and hadn't used it for anything yet.  Here was my chance.
Grinding wheel, smaller fine grinding and polishing accessories
Holding the Dremel parallel to the bench gives me a 25° grind,
I followed up with the fine grinding and polishing
To polish the back, I used my diamond "stones", rocking the gouge as I traversed the stone.
Started at front of stone with far side of gouge contacting stone ...
... and as I pushed the gouge across the stone, I rocked it back so the near side was contacting the stone
After some work on the strop, I got a beautiful smooth back
Then I got back to the bevel, stropping on a piece of leather charged with honing compound, draped over a dowel rod.
Stropping the bevel
There was one issue with this method.  I sharpened the larger gouge first and when grinding the bevel, I just went side to side without changing the angle of presentation of the Dremel to the bevel.  Because of the curve of the gouge, this results in a smaller angle of sharpening at the sides and steeper at the center.  Notice in the picture below the uneven bevel on the larger gouge.
Note the curve at the base of the bevel on the large gouge
I don't have a picture of the smaller gouge's completed bevel.  When I ground it, I angled the Dremel towards the center of the gouge when working the outsides of the bevel.

I'd rather be doing this stuff freehand, but for now I have two sharp incannel gouges.  I wasn't sure about how and when I'd use these gouges, but I already found them handy when cleaning up an inside curve on a recent project.