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Sheldon 12" Shaper - pg. 9
March 15, 2016
New Crank Handle

With the shaper attached to the floor, I started the last shaper project for a while. I wanted to make a new crank handle for the shaper. The original crank was damaged at some point and cobbled back together. The crank attaches to the shaper with 1/2" square hole cut through a 1.3" length of bar stock which serves as the drive for the crank. I will need to make a new square drive, arm, and a teardrop shaped handle.

teardrop_handle1
teardrop_handle2
The teardrop handle has been roughed out by turning the major diameters, then filed to shape.
The handle has been smoothed and polished and the lathe has been cleaned up a bit.

My current crank handle is pretty crude and it doesn't feel comfortable in my hand. I hoped to come up with a better shape for the new teardrop shaped handle. I took some pictures of the handle on the shaper's speed control. I also took some pictures of the handles on my grinder and lathe. I worked on these pictures in a photo editor until I had a rough idea of what shape I was after. I settled on a major diameter of 0.9" for the widest portion, 0.4375" for the waist, and the end that meets the crank arm would be turned to 0.625". The shaft to attach the handle to the crank arm would be 0.5". I considered making the teardrop handle able to spin, but decided against it. I turned a rough shape on the lathe to just over the diameters mentioned, then got out a selection of files and spent the rest of my limited evening shop time filing the handle's shape. This process was a lot like turning a shape on a wood lathe - all free-hand filing until the handle looked like what I had envisioned. Once I had the shape I was after, I used 120 grit sanding cloth to get rid of the file marks. I then used 400, then 600 silicon carbide paper wetted with WD40 to polish the crank. I am pleased with the outcome. 

crank_handle_parts1
crank_handle_parts2
Two crank handle parts. The kerf on the red arm will help make a tight bend. There's another kerf on the opposite side for the second bend.
Since the sine bar wouldn't fit under the part, I placed it on top and set the work to the proper angle. I then realized I hadn't drilled the hole.

For the crank arm I decided on using 1/4" thick 1018 steel. I wanted the width of the arm to taper from the 1" diameter square-holed cylinder (driver) to the 5/8" bottom portion of the teardrop handle. I also wanted the edges of the arm to be rounded. The last consideration was that to clear any obstructions when turning the crank, the arm needed to be angled around 10. To get nice tight bends on the angled portion of the arm, I cut kerfs about an inch from each end. I cut the kerfs with my horizontal band saw which leaves a slot of about 0.050". I opened the kerf up to a wedge shape of about 0.125" with a thin file, which will give me the proper angle on each of the two bends.

I laid out scribe marks and milled the 1" diameter half moon on the big end of the flat stock. To mill the angle from the 1" radiused end to the 5/8" end, I wanted to use a sine bar to position the flat stock in the mill vise for the angled cuts. Unfortunately, neither my 4" or 6" milling vises had enough jaw height to fit both the sine bar and flat stock. I ended up clamping the flat stock in the 4" vise and setting the sine bar on top of it. I used a 1/4" thick parallel to support the sine bar and used a 0.148" gauge block on top of the crank arm to define the angle. I set up a DTI in a collet and adjusted the flat stock until I could traverse the sine bar with no movement of the DTI needle. I was then ready to mill the angle and round the edges with a round over bit. Or so I thought. I had to laugh at myself as I had set up to mill the angles before I drilled the hole that the teardrop handle would fit into. I had to break down the setup and drill the 1/2" hole that the teardrop handle would fit in to before I went any further. If I had milled the angles before drilling the hole, I wouldn't have parallel sides on the flat stock to clamp into the vise. I'm glad I caught my error before I milled the angles.

crank_handle_parts3
crank_handle_parts4
I drilled the hole, then milled the part to the proper angle. I'm using a 1/8" radius round over bit on the edges. I'll do some filing to clean up the shape.
The crank handle driver has been turned to 1" diameter and is being drilled to 0.5" to ready it for broaching. The length will end up at 1.3"

The next step was to make the cylinder that would contain the broached hole. I turned a piece of tool steel to a 1' diameter, then incrementally drilled it for a 1/2" hole. I then put a good sized internal chamfer on the end that I would broach into. All that's left to do on the driver cylinder is to broach it.

Unfortunately, the rotary broaching didn't go so well. The shop made broach holder and broaches work pretty well for up to 1/4" holes, but the 1/2" square that I needed to broach through 1.3" of steel put too much stress on my little lathe. I will cut out the square hole using the milling machine.

I set the crank driver cylinder up in a square collet holder and used a 13/64" end mill to turn the round hole into a square with rounded corners. I sunk four holes 0.7" deep for what would be the corners of the square, then milled out the remaining material. I then switched to a 1/8" end mill to tighten up the corners. I again sunk four cuts in the corners, then connected them. Since I was taking off just a few thousandths of material, I could use a fairly heavy depth of cut. I used 0.2" DOC for the 1/8" mill. I use the carbide 1/8" end mills a lot, but have to be careful with them. They won't take a lot of side force without snapping. I'm happy to say that this one survived.

The most time consuming part of the job was having to flip the cylinder over and align it so I could sink the square hole on the back side and have it match the square hole in the front. The depth of cut on the 13/64" and 1/8" end mills is only 3/4" and I had 1.3" to cut through. To get the square hole lined up for the reverse side cuts, I used a long stylus on my DTI and did the measuring and setup on the surface plate. The square holder for the 1" 5C collet made the job easier than trying to get the cylinder lined up and cut using a V block.


crank_handle_parts7
crank_handle_parts8
Sinking the 13/64" holes at what will be the first step in milling the corners of the square.
Joining the 1/8" holes along the X axis with passes that are 0.2" depth of cut.

To bend the arm to the proper angles, I clamped the flat stock arm in a bench vise and used a hammer and brass drift to bend the arm and close up the kerf. Once the angles were bent, I needed to silver braze the kerfs to fill them in and then file off the excess silver-nickle braze.

I had to wait a day to do the silver soldering to assemble the crank handle. My oxy-acetylene brazing rig was almost out of oxygen and the acetylene was also getting pretty low. Prices for acetylene have risen quite a bit from the last time I filled my tanks. This didn't surprise me too much as it's been at least five years since the last time I had the tanks filled. They're only 80 cubic foot tanks, but they don't get a lot of use.

To braze the parts, I am using AN-50 cadmium-free silver braze (McMaster # 76965A64). This is 50% silver and 2% nickel. I bought it for silver soldering carbide to steel, but I find that it also works well for joining cast iron or steel to steel. For this project, the teardrop handle was turned from cast iron and the arm is 1018 steel. I am glad I bought a few ounces of the silver solder back in 2008, even though I thought it was expensive at the time. The $31 I paid per Troy ounce is now almost $80. Does anyone else seem to get the feeling that the purchasing power of the dollar is decreasing at an alarming rate?

For silver soldering flux, I use either white FB3A or black FB3C paste flux. The black flux has boron included and is able to withstand higher heat for some carbide to steel applications. I used the white flux for this job. I find that cutting a small piece of the silver solder and laying it on the joint, then heating the metals (not the solder) until the solder starts to flow helps to ensure that I have enough heat to braze the joint. I then add more silver solder as necessary to fill the joint. You don't need much solder as the parts should be placed in very close contact to each other. I use a lot of flux but try to be careful to keep the flux only where I need the silver to flow. The solder seems to follow the flux to where ever it is, so you need to be careful when applying your flux. Too much solder will make for more filing and obviously wastes the expensive silver solder. As you can see in the picture below left, I got a little too much solder on the left side of the arm to driver joint. I didn't do a good enough job of wiping up the extra flux before I started brazing.

crank_handle_parts9
crank_handle_parts10
The cylinder is brazed on the bottom side after being already brazed on the top. The teardrop is brazed on the bottom, but wicks to the other side.
I got a little too much solder on the drive cylinder joint. This will make for a little more filing and sanding.

Cleaning up the excess braze is a job that some people hate, but I tend to enjoy. Filing is one of those jobs where once you get into a rhythm, you can zone out for a while. Repetition and some good music makes the time spent seem short.

I spent an hour or two blending the brazed parts into the arm and cleaning up the teardrop handle. Once I was happy with the way the crank looked, I lightly sanded the surfaces with 400 grit silicon carbide paper. I cleaned the crank with lacquer thinner and taped off the teardrop handle. I was ready for paint. I sprayed a couple coats of primer and called it quits for the evening.

crank_handle1
crank_handle2
The filing and sanding have been completed. I'm pretty pleased with how it looks.
A couple coats of primer have been sprayed. I'll add the color coat in the next day or two.

I sanded the primer with 400 paper, then cleaned the surfaces and shot on the color coat with my artist's air brush. I like the air brush for small jobs because it is much easier to clean than my larger spray guns. Over the next few days, I sprayed three coats. The color is Tractor Supply machine gray enamel with about an ounce and a half of black added to the quart of gray. I added some hardener and thinned the small cup of the mixed paint with about 10% mineral spirits to get it to shoot properly though the air brush. The picture below right shows pretty close to the true color since it was taken without the camera's flash.

crank_handle3
crank_handle4
The crank handle clears the second shaft with a bit to spare. The handle is a little longer than the stock handle by design.
One more view of the handle. Unlike how they show in the picture, all of the newly painted surfaces are the same color.

The project turned out pretty well. If I hadn't spent so much time building the rotary broach, it would have been done a lot sooner. However, the rotary broach is a neat tool and there will be other uses for it.

While I would prefer to have an original unmolested handle, the new handle is a lot nicer to use than the old one and it looks a bit better.

crank_handle5
The new crank handle and the one that came with the shaper. I think that the new handle works and looks a bit nicer.



Shaper 1
Shaper 2
Shaper 3
Shaper 4
Shaper 5
Shaper 6
Shaper 7
Shaper 8
Shaper 9


Fager March 15, 2016