Thursday, August 28, 2014

Life is a grind

Well, the bandsaw vise is working. I still need some blade adjustments to bet the thing to cut perfectly square. But this is for another day.  Today's post is about a grinder. Specifically I have a 4mm carbide end mill to deal with, for my Proxxon mill. The largest size collet I have for that mill is 3.2 mm which is 1/8" in RGU. So I propose to cut the shank down to 3mm to fit my next collet. I tried very hard to cut it down to 3.2 mm and failed. I cut a taper into it. Slipped in the collet.

Now you might say "you have a lathe, dummy! Just turn the shank down! Piece of cake!" Alas, the end mill is carbide. If I tried to cut it with even a carbide tool, I would ruin the shank, certainly the tool, and maybe even the lathe. Not an option!

The only way to do this with my equipment is with a toolpost grinder. But nobody makes one for the Taig. So I improvised one. I started with some 1/4" - 6.3 mm steel square bar from Lowe's. Nice nickel finish on it, too. The Taig toolpost takes this size. Ten second's worth of time with Handy Bandy cut it off. Then I milled the ends square.

 The basis for this gadget is the Dremel chainsaw sharpener. This gadget is lousy for chainsaw sharpening. But the Dremel screws into it. It is amazingly a metric thread, M19x2, which I cannot cut. It's very large and I have no such tap. So I bolted the sharpener bracket on my piece of bar. I put a dial indicator on the Dremel and on the chuck. Chuck ran out (was off center) .06 mm and the Dremel only .03. I was impressed by the Dremel. It took a lot of fiddling to get the holes in the bracket right in line.
In the end, it took a long time. The grinder does not like big cuts. Furthermore if the grinder axis is off-center you will grind a taper on the shaft. So you have to measure the shaft at root, middle, and end and adjust the toolpost accordingly. There is no way I can get a dial indictor into this setup, I sure tried enough, but no room. I practiced on a broken drill bit until I got the angles right. I wore out 3 grinding wheels in the process. Carbide is very hard. Also things tend to move. So it's grind, measure, reset, go again. Took, essentially, a full day.

But it worked. The new shaft fits, just, the 3mm collet, so I have a 4mm endmill at my disposal on Cecil B. de Mille.

Friday, August 8, 2014

Handy Bandy's vise, a long trip.

The saga of Handy Bandy's conversion into a cutoff saw continues. In this episode we relate that we were unable to find a suitable commercial vise for him; we were obliged to make out own. One of the hardest metalworking projects I have ever undertaken. At first I tried just clamping down the work and hoping for the best.

 Alas, this does not work. The bandsaw blade pulls left to right as you view the picture. It exerts enormous torque on the clamps. The work is pulled crosswise and the blade jams. This needs a proper vise. I looked all over the place and could not find a proper one. So I decided to make my own.

Long ago I found a couple of bedsteads thrown out by the wayside. With my trusty angle grinder I deconstructed the bedsteads and provided myself with a lifetime supply of angle iron, I am here to tell you, bedstead steel is super-excellent. I could make tools out of it, and will in the future. So the idea is this: we have a fixed jaw on a vise (angle iron). We have a movable jaw. Angle iron too. Finally we have an end block. For this I used 13 mm (1/2") square bar. I bought 10 foot of ths stuff for $7 from Fastnall in Wasilla. Now the whole megilla has to be lined up, clamped, and drilled in the proper place. It was quite difficult to keep the whole aligned as I drilled it:

 Now over to the lathe. We need some steel rod. I used hardware store stuff 12+ mm, not the best. I turned down the ends in the lathe to accept hardware store 10-32 screws and threaded then with a die:

 Now we put the whole thing together. We will have to tap the end block for a 1/4-20 (about M6x1) holdit-down screw, which I did, a real pain because I really don't have the proper size drills. I had the holdit screw nade up from a previous abandoned project.

And there is my vise. Now we have to countersink screw holes to take wood screws so I can hold down to the wooden block. Then use wood screws to hold it down. Then realize you need a shim under the movable jaw. Adapt a pice of aluminum. Then you have a vise.
And here is the end result. We have a little piece cut off on the bandsaw. Stiiting on the Al shim. It works. We need a bit of tuning but I have a working cutoff saw.

More to come.

Sunday, August 3, 2014

Camera Repair

As I mentioned before my Nikon Coolpix had a latch failure. The tiny little latch that holds the battery lid in place was broken off when I dropped it on the floor. I have improvised with scotch tape -- not duct tape; it stretches too much. Time for a more secure fix. Obviously I cannot photograph any of this because the camera was kaput. But I can show you the result.
What I did is spend half the morning measuring the camera. I then put a screw through both lid and the plastic beneath. Little black thing lower right on Camera. It obviously has to be placed so that there is some "meat" underneath the hole, i.e. some plastic. We are running the risk of drilling into some very significant wire; but the camera did not work anyway, so what the hey! Now -- how to drill the hole? It must be drilled, or at least started,  on the Proxxon mill. I have .001 = .025 mm control on where I place the bit. I also have some tiny aircraft drill bits, Morse number 80 or so  (bigger the Morse number the smaller the bit; most confusing, about 0.6 mm) . The next problem is to drill the hole. My mill will not go high enough to go through lid and bottom. The lid, by the way, goes out and only then will it hinge.  So I put the hole on the bottom where I wanted it. After that I zeroed my dials so I could get back to the right spot. Then I closed the lid. Oh dear the bit broke when I cranked back. On a chance I said "maybe it will cut anyway." It did! Once you have a pilot hole it is not so hard.

What size screw? Well, I had #4-40 caphead screws, these are about 3mm and they worked. So after that I moved over to the drill press; drill and tap for #4-40, put in a screw.  A Coolpix costs about a hundred bucks. My repair is much cheaper. Even if I need an Allen wrench to change batteries. Thanks to John for photographing the repair.