[Newbie] Today's Lesson: Making A Jig...

dave_r_1

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I'm making a grinder for sharpening lawnmower blades, and as part of it, making an axle for the grinding wheel.

And since it's being driven via a pulley, I'm putting in a keyway for the pulley, and since I don't have a mill, I decided to make a jig so I could use my lathe to do it. I worked off this video:


Pretty straightforward. Here's the jig:
IMG_0510.jpg

And after milling it:
IMG_0509.jpg

Did a reasonably good job, edges needed to be cleaned up with a file.

But, unfortunately, this is the result:
IMG_0511.jpg

Not quite centered.

So, today's lesson: When making a jig, give it a trial run to make sure it works right...

I can get a pulley on it with a key, but it wedges on really good...

Tomorrow, I'll try shimming the jig up a smidge [technical term], test it out on another shaft, and then put another keyway in the axle on the opposite site.

And no, that red stain on the far side of the carriage is not blood.
 
I forgot, that video has absolutely horrible music playing the whole time. It actually makes the video less informative, because you are really tempted to mute the audio, but the guy talks about how to do the various operations, so you can't. You just have to listen to that stupid music...
 
Live and learn, you already know what to do next time. keep up the work! Sometimes a mistake is the best learning experience. When people ask me what I make in my shop I have a tendency to tell them I take large pieces and make smaller ones, and some are actualy useful. :wink:
 
Put your indicator in the lathe chuck, find the top of the rod and set 'zero'. Move the cross slide far enough away so you can swing the chuck 180° and find bottom. Shim half TIR and you should be pretty much dead nuts.

Vice grips, the duct tape for machining:D
 
And, with a little shimming...
IMG_0512.jpg

Some notes if anyone else makes this jig:

Use a nut for clamping the jig to your compound slide. I reused the threaded handle from my 4-way, and it worked, but the handle was getting in the way of the vise-grips when you have to adjust the jig to get the bar perpendicular to the end mill.

I found that using the cross slide to move the axle along the end mill with the lathe off, I could visually get it perpendicular, as I couldn't get the carriage over far enough to get the axle flat against the 3 jaw chuck.

On the lathe, the result looks pretty nasty, but use a wire-brush to get the filings out of the slot, and file the two edges a bit, and the slot looks great. Only way it looks different from most other keyways is the end, which is rounded using this method, but most other ones gradually go up to the shaft surface. I'm not coordinated enough to do something like that...

Finally, I would like to slap the person who decided that there is no need to set the compound slide at any angle near perpendicular to the workpiece. Evidently, the closest they expect you to have to put it accurately is to 30 degrees from perpendicular [what you would use for threading]. Blah.
 
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Used jig to put a flat spot on a tube so I could weld a long nut to it [to be used as an height adjusting screw]. Took a little time and a couple of test passes to line up the jig so it was perpendicular to the end mill.

IMG_0513.jpg

It worked well, using .001 passes, as the work piece is not directly clamped down with the visegrips but only indirectly via a bolt through the middle, so I could make the flat the whole way along the work piece. You can't really see it, but the work did rotate a bit once, when I started a test pass with the end mill taking too big of a bite out of the work.

Lessons learned today:

Find a milling machine. It makes a bunch of jobs easier than cobbling together a bunch of stuff.
If you use a long threaded rod to help with aligning a nut with a tube, either cover or remove the rod before welding the two pieces together, as spatter from welding may get in the threads.
If you do get spatter from welding into threads, remove the spatter before trying to get the threads through a nut.
If you do get spatter from welding into threads, and you try forcing the threads through a nut, don't use a drill to try to speed and/or force the threads further through the nut. The jaws on my cheap drill will never be the same...

I wound up cutting the rod off at one end of the nut, reversing the rod back through the nut using visegrips, then running a tap through the nut to fix it's damaged threads. And then throwing away the parts of the rod that I couldn't get the spatter out of the threads.
 
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