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#1 2010-09-26 10:27:15

Registered: 2005-10-11
Posts: 1297

Hitachi 20 sb shoe adjustment modification tutorial

Before anyone reads any further, I must say that the Clark Planer is a great deal, especially after having done the changes myself. The reason I decided to do it myself is that I had a brand new Hitachi before I realized you could buy the modified one for a great price. And at any rate I absolutely love screwing around with tools, so what the heck I went for it. The only problem, I could not find any info on how to make a fast acting depth adjustment, so I decided to tackle the beast on my own.

After a few attempts at solutions I searched Mcmaster Carr for an Acme thread, but it looked a little pricy for something that might not work. Then in the middle of the night the answer came—a Starter has a throw pinion and gear and it moves quickly and smoothly.  For sizing I thought an outboard motor might be a good candidate.
So I went to my local boat engine mechanic, and gave him the description of what I was looking for. “Ah, you mean a BENDIX!!�  Yeah sure, a Bendix!! ….now I know…. So I bought a used one for $10, went to Ace hardware for bronze bushings (washers)—3 of them, got a spring, a 1/4x20 2�  stainless bolt and a split shaft collar, and a little round knob for the lever. Total cost around $20.

Before you go any further, the tread in this particular bendix, causes the shoe to move UP (deeper cut) when you turn the lever to the left, opposite to the Clark planer. For me this is no big deal to relearn as I have not used a planer so extensively. However, I would think there would be Bendix units with the opposite thread direction, but I did not bother going that far in the quest. For me the most important was to keep my hand level and with minimal rotation create a significant change in depth cut, while having a smooth up down action of the shoe. This sure beat all other planers I have ever used.

Basically the original threaded rod is removed and in place of it a fast tread nut is epoxied to the top of the aluminum cylinder, the rod is then cut close to the thread so the shaft can freely travel up and down the nut. The split collar holds the shaft in place so it forces the shoe to travel up and down the shaft. It requires ¼ turn to move the shoe more than 1/8� .
Tools needed are 1/4x20 tap (male and female), hack saw, grinder with metal cutting wheel, masking tape, epoxi and cabosil.
Take a good drill bit and drill a pilot hole on the base of the existing bolt on the planer shoe. Drill out the existing bolt. You need to go in about ¼� . Then pop it out.
Take the newly acquired bendix which you chose as close to the original shaft diameter as possible, and cut off the gear portion of it. Use the metal cutting wheel to do the job quickly.  This is a hollow unit with swaged end that holds the fast thread nut that you want to use.

Remove the nut and grind some grooves in the hex head, so the epoxy bonds well to it.
Take a grinder and grind the flange of the nut until it becomes slightly smaller than the outside diameter of the aluminum cylinder. There should be enough flange left so the nut sits on top of the cylinder

Cut off the bottom portion of the shaft, leaving 1/16 (1-2 mm) of shaft protruding past the thread. Enlarge the hole in the planer where the rod will go through, using the appropriate drill bit size.
Thread the rod into the fast nut, and tighten the split collar ring against it to minimize movement. Use masking tape to protect the upper part from any epoxy.
Wax thoroughly the shaft and threads, same with the top of the nut. Make sure the area to glue is clean and free of wax. Use a grinder to rough up the area to glue. Use wax or mold release agents to protect the inside of the planer and the aluminum cylinder. Cover everything else with masking tape.
Use modeling clay to close the hole on the bottom of the shoe, and to cover the fast thread flush with the nut. Take a close look at the picture below showing this. Make sure the clay also covers the bottom of the bolt. Both the nut and the clay area will be totally encapsulated in epoxy/cabosil mix, so it is important that no epoxy contacts the thread.

Now make a mix of resin research Quick Kick, pre wet the nut and the aluminum on the inside, then add cabosil, so as to form a peanut butter consistency paste. Apply carefully to the nut, and over the clay, and the inside of the aluminum cylinder. Put enough so the excess will squeeze out when you push the unit into the cylinder. Remove excess as it squeezes out. After the nut is seated wipe off any traces of epoxy off the cylinder walls using acetone
Now VERY carefully slide the planer over the whole shoe/ rod unit, keeping firm pressure on the rod so it does not move around.
The planer should be in a level place, so the rod is well aligned with the hole.

While the epoxy is setting, get busy with the lever unit: drill a hole into the split shaft collar using the pilot drill appropriate for the tap to be used. Tap a 1/4x 20 threads. Cut the head off the stainless bolt and tap a 1/4x20 thread onto the cut end, so he little threaded ball screws into it. When every thing is assembled, use a hack saw and cut a reference mark, use a Posca Pen and make a permanent reference mark on the split collar ring. This will help set your shoe depth at zero and max cut. Later you will mark the planer body with the marks set to zero, on to max as you prefer.

When all epoxy is set, remove the clay from the inside of the cylinder with a bent piece of metal, and remove as much as you can. I don’t know if there is anything that can dissolve the clay, but leaving some is not that critical. Make a little plug for the hole on the bottom of the shoe, and close that hole, allowing enough room for epoxy and cabosil mix too “grab�  onto the hole. Mix a batch of epoxy/cabosil and fill in that hole, and the entire groove on the shoe. When all epoxy is hard, trim off excess, sand, clean and polish the shoe.

Install a bronze bushing, a spring and another bushing, and then put the shoe back in the planer. Put another bushing against the planer body, and then the split shaft collar with the new lever installed.
Place the planer on a level, and unscrew the rod so it sits as high as possible, still leaving some thread engaged. Push down hard on the collar, and make a small reference mark on the shaft so you will know easily when the shaft is in the upmost position, while you adjust the lever to the position you want. Tighten the screws of the split shaft collar.
Verify correct operation.

Now mark the zero depth position on the base of the planer, close to the split ring. Mark the max cut depth.
Make a handle knob out of whatever you find. I had one made out of stand up paddle, but ended up with a block of maple wood. Drilled a hole in the middle, put the block on a drill press, and turned a round handle out of it. If you have access to a machine shop, I am sure you can make something really trick. You can make them out of UHMW plastic (Starboard) or polypropylene plastic, or aluminum.

Last edited by tinho (2010-09-26 10:35:57)



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