Thursday, October 31, 2019

Grinder Improvement

It's been almost three years since I got my hand-crank grinder.  Its clamp doesn't open wide enough for me to attach it to my workbench, so I clamp it to a chunk of wood and clamp the wood in a vise.
My grinder, clamped to a 2x8, clamped in the end vise
The original tool rest is an "L" bracket bolted to the side of the gear box.
See the bolt?
The tool rest is fairly flimsy, so early on I made a new tool rest from a few pieces of oak and pine.
My first homemade tool rest
The adjustable rest is bolted to the gear box on one side and to a pine upright on the other
In use, I held the tool flat to the surface of the rest and brought it to the wheel
There were some problems with this.  First, it took a bit of practice before I got good at using it.  Second, if was never as accurate as I wanted it to be.  I wasn't getting an even grind across the width of the chisel or plane iron.
Here's an example: this chisel had been sharpened a few times after being ground,
but you can still see that the grind marks were not consistent
A while back I saw a grinder attachment that someone made and I'd been wanting to make something similar.  It's basically a platform with a movable stop that will hold the butt end of the chisel or iron a fixed distance from the wheel.  I can move the stop to get the grind angle I desire.

Half inch plywood extension screwed to the bottom of the 2x8, with a slot
down the middle for the movable stop
The stop keeps the chisel a consistent distance from the wheel
(the ruler is laid in front of the stop to keep the chisel from getting stuck in the slot)
Another view - see the sparks?  Ooohh!
And another view, in line with the wheel showing the alignment of tool to wheel
This is a far more even grind than I've ever gotten
The stop does double duty.  One side is straight so that I can slide chisels side to side, and the other side has a "V" groove for grinding gouges.  I've had much more difficulty grinding gouges in the past.  With this helper, the gouge's butt end stays seated in the groove while I twist the gouge to grind the entire bevel.
Bird's eye view of a gouge on the grinder
This allowed me to get an almost perfectly consistent grind all across the curved bevel.
Now that came out great!!
For plane blades, I can use it just as I did for chisels.  But it looks like the iron is held at a weird angle.  So I made a riser to hold a plane iron at a much more reasonable angle.
Plane iron in the jig
Plane iron on the riser
As it turns out, the riser isn't necessary and I quit using it.  That upright angle of the iron doesn't matter - what matters is the angle that the wheel grinds on the bevel.

This was an easy project to make.  It just took a little thought about how to do it.  And it works fantastically well.  I'll still need the other tool rest I made for other kinds of grinding work, but fortunately the two jigs are removable.

I'd seen another variation on this somewhere, possibly made for a powered grinder.  In that one, rather than have an adjustable stop, the whole platform was adjustable, sliding in and out through a slot under the grinder.

Thursday, October 24, 2019

Tenon Saw Problem - Solved?

Well, the problem is partially solved anyway ...

I've had this Veritas tenon saw for 4-5 years now, but I hardly ever use it.  Its tooth line is 11" long and it is filed rip at 12 tpi.  I reach for a $5 garage sale gents saw for dovetailing and other small work instead of the Veritas saw.
Veritas 12 tpi tenon saw
For whatever reason I've had problems with this saw.  I've sharpened it a few times and it's possible that I did something to make it worse rather than better.

Here's the problem I'm having.  When sawing, I get about 6" of the tooth line into the wood and ... CHUNK!  The saw stops dead.  I had thought that maybe I had overset the teeth in that area, so I stoned them and verified that the set was not out of whack.  The set was fine, but I still had the problem.

Well, I marked the area on the saw where the "CHUNK" was stopping the cut and took a closer look at the teeth and this is what I found.
Teeth marked in red are lower than the rest
Somehow I filed two teeth far too much and they ended up lower than the rest of the tooth line.  In the next picture, I had run a red marker over the entire tooth line and then jointed the teeth.  You can see a flat on all the teeth except on the two teeth that were over-filed.
Two teeth not jointed.
So I continued jointing until I got a small flat on these two teeth, then filed the saw carefully to ensure I only just barely removed the flats from every tooth.

A test cut went much better than before.  However, it still wasn't as smooth as it should be.  I'm not getting the big "CHUNK" anymore, but this saw hops all over the place as I push it forward.  I file my rip saws with 0° rake. 

It could be that my first test cut was in oak.  If I change my technique a little bit it gets better.  At first I had the board straight up in the vise and tried beginning the saw cut on the far edge.  The saw bounced all over, even with a very light grip.  But if I lean the board away from me and saw the front edge of the end grain first, I get a smoother cut.  I'll have to play with this some more.  Maybe I'll use a Sellers trick and file the first inch or two of teeth with a more relaxed rake, which would ease the teeth into the cut.  Time will tell.

Thursday, October 17, 2019

Update on Tapered Reamer and Tenon Cutter

My last two posts were about making the tapered reamer and the tapered tenon cutter.  The result was satisfactory, but the tapered tenons still wiggled a little bit in the tapered mortises.  I made another reamer and another tenon cutter and this time the tenon is perfectly snug in the mortise.

I turned a new reamer on the bungee lathe, this time using red alder.  The first one was from a 1 3/4" square blank, which seemed too bulky to me.  This one started out a tad over 1 3/8" square.
Turned very carefully to get a straight taper
I went very carefully to get the conical section as straight as I could, but then I got to thinking about the necessity of having it perfectly conical.  My thought now is that this piece merely holds and supports the blade.  It is the blade that needs to have perfectly straight edges.  The wood doesn't do the cutting and if it doesn't match the blade perfectly, it doesn't really matter to the cut (as long as it's not horribly off).

The next thing I did to make this reamer better than the first was to be more careful about the relief cut where shavings can go in front of the blade.
On the first one I made, I chiseled willy-nilly.
On this one, I drew a layout line and chiseled carefully to it.
I got a much more consistent trench cut on this one, thanks to better layout.

For this new tapered reamer, I also made a new blade, this time without saw teeth and it results in a far smoother cut.  Check out these two pics:
The original reamer blade with saw teeth left deep gouges around the hole
This is the same hole as above.  The new reamer removed the gauges left by the
first reamer and left a very nice surface (the lines you see are annular rings)
For this blade, I honed the edges at 90°.  I think I read (either from Elia Bizzarri or Curtis Buchanan) that others sharpen the edge at 70°.

I also wanted to make another tapered tenon cutter, this time being a bit more careful about layout and cutting.  My blank was about 2" thick, 3" wide and 8" long and I carefully squared one face with one side, then made the other face and side parallel to the first ones.  I laid out a center line along the length and along the width and followed those lines to the opposite face.
Added concentric circles to help me judge whether or not I ream straight
I made the layout lines full length and width for reasons that I hope will become clear at the end of this post.

After boring a 3/4" hole from both sides, I used the reamer to taper the hole.  I checked with a square often to see if I was tapering straight and made any adjustments to fix any straying.  If I was leaning a little left, I leaned the reamer a little more to the right to fix it.
Here's the top (larger diameter side), fairly well centered
For whatever reason, the small end came out a little off center
The small end of the tapered hole was only reamed slightly, as I wanted it to stay close to 3/4" diameter.  But what little I did ream it removed more material to the upper right in the pic above and less by the pencil point.  Well, close enough for amateur work!

I then laid out the 15° angle on top and bottom, the line emanating from the point where the circle meets the vertical center line.
Top surface: note the 3/16" relief for shavings ejection
Bottom surface
After sawing out the waste and carefully paring to the lines, I got a nice flat bed for the iron to rest on (and be clamped to).
The waste removed and a parallel surface marked
To aid in clamping the iron to the bed, I drew lines parallel to the bed, then sawed away the waste and planed to the lines to create a surface nicely opposed to the bed.

Again, I'm using a spokeshave iron for the cutter, clamped in place with an "F" clamp.
The setup ready for use
A test cut came out great - the tenon fit a reamed mortise tightly at both top and bottom.
Tight fit at top ...
... and perfect at the bottom (excess was planed smooth to show the fit)
The last thing I did was to add a curved point to the top of the reamer.  I his videos, Curtis Buchanan uses the pointed top of his reamer to line up the cut with sight lines on a chair seat.  That way, he knows the reamed hole is in perfect alignment.
Made a nice tapering point at the top of the reamer
Here's the thing about these tools.  It's not easy to taper a hole without leaning left, right, front or back.  And it's also not easy to taper a tenon without leaning.  It takes constant checking with squares to make sure your tapers have the center line you desire.

To help with the tenons, I've thought about making some kind of block that would clamp to the tenon cutter.  There would be a hole in the block just big enough for the piece being tapered to fit through.  The hole in the block would be centered using vertical and horizontal layout lines.  I could clamp this block to the tenon cutter, matching up the block's layout lines with the layout lines on the tenon cutter.  That way, I would know that the center of the block's hole is in perfect alignment with the center of the tenon cutter's hole.  And if the block's hole is just a tad larger than the stock being tapered, the stock couldn't wiggle much as the taper is being cut, resulting in a straight taper.  It's just an idea - but one I'll be checking out soon.  Maybe after some practice with the tenon cutter I won't need these training wheels, but they could help.

Thursday, October 10, 2019

Making the Tapered Tenon Cutter

Last time I wrote about making a tapered reamer that will enlarge and taper a cylindrical hole.  To go along with that, you need a way to taper a tenon that will fit into the hole.  This post will describe how to make the tapered tenon cutter.

I squared up a 2" thick piece of poplar, marked a location on top and bottom and bored a 1/2" hole.
I had drawn (poorly) several concentric circles before boring the hole.
Note the vertical reference line - there's one on back, too.
The next step was to taper the hole using the tapered reamer.  The concentric circles that I drew were to guide me in keeping the tapered hole as straight as possible through the workpiece.  This is not really necessary for the tenon cutter to work properly, but it's good practice and it might help me to make the tapers straight rather than on an angle to the axis of the spindle.
I had run the reamer a little more than needed - the far end was reamed to 11/16"
and the large end just under 15/16" diameter
From the point where the vertical reference line meets the bottom of the 15/16" circle, I drew a line to the lower left at about 15°.  After repeating that on the other side for the 11/16" circle, I sawed out the angled waste and smoothed the sawn surface with a chisel.
Didn't get any photos, thought I'd try describing with a Sketchup model.
The lower left triangle gets sawn out.  I sawed an extra 1/4" to the right of the
vertical reference line to add an "escapement".
I also sawed a flat area parallel to the newly sawn surface - a guideline can be seen under the ruler two pics above.  This was to give a parallel surface for clamping a blade to the tenon cutter.
Here's how the blade gets clamped to the tenon cutter
I'm using the iron from a spokeshave to cut tapered tenons.  I know some people will put a radius on the leading edge of the iron so that it doesn't gouge the tenon stock.  I still need this iron in my spokeshave, so I couldn't do this.
A closer pic from a different angle showing where to set the iron
I roughed out a piece of poplar to an approximately 7/8" diameter, small enough to fit into the big end of the tenon cutter, and made a test cut.
Ready to test the cutter with a 7/8" poplar dowel
Making tapered tenon shavings
It's hard to know whether or not I had the dowel 90° to the tenon cutter.  I've gotta think about how to ensure that.  If you hold the dowel off-center, then the axis of the tapered portion will be angled from the axis of the straight portion of the dowel.

I tried the tapered tenon in a hole that I had bored and reamed.
Nice and tight in the large end ...
... but a little loose in the small end
So I modified very slightly the bed of the cutter to remove a little more from the large end of the tenon
It took a couple of iterations, but I got a nice tight fit of the tenon in the tapered hole.  I still need to do a bit of refining, but I'm almost there.

Just a note: this is probably very obvious to most of you, but I hadn't thought it through until I made these things.  You'll need different tapered tenon cutters for various diameters of spindle stock being tenoned.  For example, the thicker legs of a chair might be 1" diameter at the start of the taper, whereas the spindles for the back of a chair might be 5/8" at the start of the tenon.  They'll need separate tenon cutters, even though the same reamer can be used for both sizes.  So far I've made two tenon cutters - one for 7/8" dowel stock and another for 1 1/8" stock.

Another note: The YouTube channel "Pask Makes" has a couple excellent videos on making a tapered reamer and tapered tenoner.  Much of my method came from those videos.

Thursday, October 3, 2019

Making a Tapered Reamer

This has been on my to-do list for quite a while.  I've made some small, four-legged stools in the past and they've had round tenons glued and wedged in round holes.  But I know it would be better to have tapered tenons in tapered holes.  That way, every time the stool gets sat on or stood on, the joints only get tighter.

I wanted approximately a 6° angle on the taper (3° either side of an imaginary center line) and calculated that over 8 1/2" length of taper I'd need 3/8" diameter at the small end and 1 1/4" diameter at the large end.  So I glued up some oak, octagonized a 1 3/4" square blank and put it on the bungee lathe.
Checking the taper for straightness
So far, I'm a fairly horrible turner and I had some trouble getting the taper to be straight along its entire length.  But it's close enough.  For anyone interested, there's about 1/4" allowed for the transition from taper to octagonal section and the octagonal section is about another 3 3/4" long.  I later bored a hole through the octagonal section for a handle.

To guide my sawing a kerf lengthwise through the tapered section, I marked some lines carefully along the length of the taper.  Having marked crosshairs on both ends before turning helped to get the lines 180° opposed to one another.

For the blade of this tapered reamer, I'm using a really crappy and cheap garage sale saw that I've been cannibalizing for scratch stock blanks.
Blade marked out
But before I cut out the reamer's blade from the saw plate, I used the saw to make the kerf that the blade will fit into.
I had hammered most of the set out of the teeth to get a kerf that will match the blade's thickness
I also did a quick sharpening of the teeth before cutting out the blade and fitting it to the taper.
The blade cut out and the edge filed to match the taper of the reamer
Bladed installed in the reamer: the saw's teeth are just barely showing
On the other side, the edge is proud of the taper by about 1/32"
I bored a through hole in some pine and made the first test taper.

The first cut
The tapered hole showing the reamer's teeth marks
This is good enough for a prototype and proof of concept.  Next I'll write about making the other part of the equation: the tapered tenon-cutter.