Here we go again, clearing items from the backlog of jobs I have promised people I would do for them.
I remember seeing one of these that a long time machinist had made for himself, but it was about twice as long. The longer it can be made the easier to use and more accurate it will be. He did piece work, so anything that speeded up the tramming process meant more money in his pocket.
A friend has asked me to make him one of these, and he has already given me the relevent dimension required, I think for an X1 mill.
These are produced commercially, in a slightly different design. How they can have the audacity to patent it, I have no idea.
If you find one during your searches, please don't relate to it in this post. Issues have arisen over copyright on another post, and I don't want it rearing it's head here.
The one I will be making will be a short version, that will tram in both X and Y axis. But there is nothing stopping you making one much longer, just for use in the X axis. I should really have done that with mine, as I have no tramming adjustment in the Y axis on my mill, maybe I will just make another one but longer.
Now a few things that need to be said.
Please don't ask about tramming in this post, if you don't know what it is or how to do it, please raise a seperate topic and all questions will be answered there.
The other main issue is that this will end up as a precision instrument, and if your machinery or yourself are not up to working to tight tolerances, I would suggest you wait until you have the relevent experience or machinery. Get it wrong, and you will be doing a non tramming exercise on your mill.
You will require a faceplate on your lathe with the same or larger diameter as the main bar is long, or if you can come up with something that will do the job I will be showing later, then good, but the accuracy of this tool depends on the final cutting on the lathe. If you can work to tolerances of 0.002" (0.05mm) or lower, you should be OK.
This is easily only a one day job. Its takes me much longer because I can only work a couple of hours at a time, and I make the post up out of what I have done in that time.
So away we go, showing what I have been up to today in my little shop of horrors.
I will be turning this,
Into one of these.
It looks an easy exercise, but as I have said, all the work is keeping everything accurate, and being done in the correct sequence.
These are the rough materials I will be using for the job. I will be showing things in imperial for our US cousins, but actually I will be working in metric as that is the size of most of the bolts and bits used.
The length of the ali bar isn't shown yet, as that will be determined later, this one is about 8" long. You could just as easily make the bar out of steel, as long as you can get the surface finishes required. There is no handwork allowed except for deburring. By hand finishing surfaces, you will be introducing errors into the precision faces, unless you have a real nice lapping plate, and know how to use it correctly. The steel bar is 5/8" diameter.
You can work with larger or smaller dimensions, but it will be up to you to modify the design to your materials. These are the ideal sizes for the gauges I have.
This shows how deep the material should be for the gauges you are using, the sensing tips should be protruding out of the bottom of the finished tool by roughly the amount shown. You can use slightly shallower bar, but the gripping area for the top part of the gauge rod will not be supported as much. You don't want too much sticking out of the bottom as it makes the part vunerable to being knocked.
If you are going to be making the dual axis version, you will need the dimension as roughly shown between the two points of the gauges. The easy way is to measure from centre to centre of the outside rails of the table. If just making the X axis version, just make it as long as you feel is right, 12" would be a good figure (if you have a faceplate that can take it).
So now we get to the machining bit, cleaning up the bits of rough material I have selected.
There is a bit of a catch 22 situation here, because of the high accuracy of machining and drilling, the mill needs to be trammed up as close to perfection as you can get it. I had no trouble, as I already have a tramming tool, you will just have to do it the hard way until you have made yours. A sure sign of having the tramming spot on, is when flycutting, you will get very fine pattern marks showing that it is cutting on both the forwards and backwards cut as it goes over the material.
Here it is just cleaning up the surfaces, with a 5 thou cut. I went thru the procedure as though I was squaring up a bar, and ended up with all faces parallel to less that 0.0005" (0.01mm).
Then using a countersink tool, a very small chamfer was put down each edge. This is to try to eliminate errors after the tool has been used for a time, no sharp edges to get 'dinged' and stop the precision faces sitting down correctly.
This shows my setting tool from the bottom. It shows the layout of the slot and if you look very carefully, where the bolt sits. I will be showing how to do all this and dimensions a little later.
So now onto a bit of lathework.
The bar had a spigot machined on one end about 5/8" long (non critical but somewhere close), and 3/8" (10mm) diameter minus 0.001" (0.025mm). You could just about get away with being 0.002" (0.05mm) under size. This is to allow the use of high strength Loctite during assembly. The shoulder was also cleaned up as this will be a datum face.
The end of the spigot had a small chamfer filed on the end, and a hole drilled and threaded into the end of it. Mine was 6mm, for imperial, maybe 1/4"
So the bar was then turned around and the outside diameter reduced so that it was slightly smaller than the dimension between the chamfers on the ali bar. There will be slight length and diameter changes to this bar on the very final operation of making the tool.
The two main bits machined up and ready for the next stages.
Showing how they will be assembled, once the right holes are in place.
So there we have getting the bits prepared.
Next time it will be drilling holes and assembling it all.
John
