Making guns in the garage

I just put two (x,y) of the Igaging DRO's on my LMS mill.
Yeah, ridiculously inexpensive. Accuracy? Well, I'm a total noob to this as I said. But, ten full turns of the leadscrew each axis (@.0625) read exactly .625 on the LCD. They advertise .002, per six inches of travel for this model:

http://www.igaging.com/page18.html

They have a new line, the Absolute DRO, with an absolute function, better display, and .0015 accuracy per foot. Still, under $100 per axis depending on length. 6" is about $60 on Ebay.

The mill had a torsion spring to support the head, I've just replaced it with an air spring so I now have space to add the z axis.

I suppose, it depends on the level of precision of the part(s) being machined. Basically, these are the same technology used in calipers, adapted onto longer slides with remote readouts.

But, accurate "enough", for me for the time being, at least- and NO MORE backlash compensation! That alone makes it a dream to learn with. Seems to me that even minor errors are bound to occur due to backlash that would end up being no more accurate in the end than using the DRO's. I hesitate to offer an opinion though because I'm so new at this.

Hesitating to put a lot of dough into the manual aspects (including a power feed) because I'm giving it some time to figure out whether I'm going to do the CNC conversion which would make these "improvements" moot. There are comprehensive kits designed specifically around these X2 mills that make a turnkey conversion for little more than a grand.

I haven't put any DRO's on the lathe yet because it's a bit more challenging to figure out a way to mount them on the cross-slide, and since all cuts are in the same direction I don't see it as a "must-have" just yet.

A lot to learn...
 
tobnpr,

You don't really need any on the longitudinal axis of a lathe. When I worked at a machine shop, turning large pump and propeller shafts, most with multiple stepped diameters and 10+ feet long, they only used a tape measure for the lengths layout, since bearing fits are drawn or shimmed up, and nothing was that accurate over the length. The diameters and finish, though, had to be held, along with any threads. So, anything you'll do on a gun, a dial indicator will work. Before several of us were lain off, they had bought a new 10 foot lathe with a two axis DRO, and it was nice.

Mills are different, though, and you have to have accuracy in all three axis, so I always just use a mighty-mag with a dial indicator, and if I am running several of the same piece, I set up stops. Long ago, they had some mills with a dial indicator built in, set up like a long dial caliper on the x and y axis, similar to the digital ones you mention, but they were mechanical. Repeatability is the main thing, and the overall accuracy on the full travel. Of course, you should measure the piece after each cut, when getting close to finish size, or I do, as I never really trust indicators nor readouts.
 
This week I did some mill work for the Dumoulin Mauser scope base with a 2" dial indicator and mag base. I also was using the dials on my 1963 Rockwell 21-100 mill. I had a 0.504" on centers hole turn into a 0.521" distance.
When they agree, I am usually within 0.001". So I screwed up. My fault, not the two machines. But my lathe has DRO [the cheapest installed by Machine tools on line before they shipped the lathe.] That has been so convenient...

As soon as I finish this carpentry work on the shop, I will buy a new mill with DRO and give a hunting buddy my old mill.
 
When I started out I put one of the cheap "caliper scale" readouts on my mill. It worked but no matter how rigid the scales were mounted there was .002-.003" of backlash in them. When the x axis went toes up I bought a cheap chinese setup with glass scales (X & Y, the Z is magnetic). It is right on time and only cost about $500.

I find them less useful on a lathe. All I have on my lathe is a Trav-a-dial
 
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