Round colume mill repositioning

B

Bruce Billett

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If anyone is interested I have a very accurate and very inexpensive and simple, solution to moving the head of a round colume mill (machine) and returning it to the same axis it started on.
I just don't know where to post it?
Can someone help me out.
 
Bruce Billett said:
If anyone is interested I have a very accurate and very inexpensive and simple, solution to moving the head of a round colume mill (machine) and returning it to the same axis it started on.
I just don't know where to post it?
Can someone help me out.
Click to expand...
Right here is fine.
 
I have an older round column mill. As anyone with one of these is aware your OK until you need to move the head. Getting it back on the same axis point can be a challenge, Best solution I can think of is an autocollimator down the middle of the spindle. Rudely accurate and expensive at best, also kind of defeating should you need to put the chuck/collet back in. Lasers really don't work that well. They are ok if you want to be within a fortnight as the beam size changes with distance and the beams seem to large to start with.
What I found that works very well is a cheap, (got mine from a gun dealer that had replaced a customers 4X10 gun scope because the hermitic seal failed and could no longer be used outside in bad weather.) A gun scope, one that is short, mine is about 5" long. If you shine a light thru the eye end it will project the crosshairs onto a distance surface. I tried this out across my garage, about 20 feet. Built a rather crude optical rail and as I moved the assembly across the garage the crosshair size remained very close to the original size. I then mounted an LED in place of the flashlight I was using so that angel would not change.
Next I built a mount and put it on the front of the mill head. I aligned it parallel to the spindle. to do this I took a piece of scrap material mounted it in my vice drilled and reamed a hole, Made a pin of the same size for a slip fit. Position the head so at mid stroke the pin was engaged with the hole about 1" deep. Marked a spot on my bed. Moved the head to a random position and lowered it, aligned the cross hairs with my mark, Locked it in place. Ran the spindle up and down to check fit. Adjusted the scope to be closer to parallel. Repeated this until I got a good fit. I was now close to parallel. Raised the head to max. repeated the procedure and adj. A few time up and down until I felt comfortable with the parallelism.
Lock the scope in place and it has been working like a charm, until you move the scope that is.
I suspect this COULD give you Micron resolution, if you played with it enough. But I am using a round column mill so expecting that is kind of silly.

b
 
Bruce Billett said:
I have an older round column mill. As anyone with one of these is aware your OK until you need to move the head. Getting it back on the same axis point can be a challenge, Best solution I can think of is an autocollimator down the middle of the spindle. Rudely accurate and expensive at best, also kind of defeating should you need to put the chuck/collet back in. Lasers really don't work that well. They are ok if you want to be within a fortnight as the beam size changes with distance and the beams seem to large to start with.
What I found that works very well is a cheap, (got mine from a gun dealer that had replaced a customers 4X10 gun scope because the hermitic seal failed and could no longer be used outside in bad weather.) A gun scope, one that is short, mine is about 5" long. If you shine a light thru the eye end it will project the crosshairs onto a distance surface. I tried this out across my garage, about 20 feet. Built a rather crude optical rail and as I moved the assembly across the garage the crosshair size remained very close to the original size. I then mounted an LED in place of the flashlight I was using so that angel would not change.
Next I built a mount and put it on the front of the mill head. I aligned it parallel to the spindle. to do this I took a piece of scrap material mounted it in my vice drilled and reamed a hole, Made a pin of the same size for a slip fit. Position the head so at mid stroke the pin was engaged with the hole about 1" deep. Marked a spot on my bed. Moved the head to a random position and lowered it, aligned the cross hairs with my mark, Locked it in place. Ran the spindle up and down to check fit. Adjusted the scope to be closer to parallel. Repeated this until I got a good fit. I was now close to parallel. Raised the head to max. repeated the procedure and adj. A few time up and down until I felt comfortable with the parallelism.
Lock the scope in place and it has been working like a charm, until you move the scope that is.
I suspect this COULD give you Micron resolution, if you played with it enough. But I am using a round column mill so expecting that is kind of silly.

b
Click to expand...
Gotta see the mill with a rifle scope mounted to it....

John
 
I have done this on a drill press with a laser and got the table aligned within a few thou. More than good enough for the job I was doing.
 
Yea, The laser is a good idea. However the beam divergence is a bother, Granted a few thou on a round column is about the best you can hope for. I build things more to see if I can do it than needing the accuracy, Accuracy is nice! But then you got to bite the bullet and buy a real mill.
So one step at a time.
Besides I spent 35 years working in the semiconductor industry making (relativity) ancient and obsoleted equipment do things the original designers never even dreamed of doing, So I love the challenge.
Got to keep the wheels turning. and you just never know when the brain droppings will yield something wonderful!
One of my heroes (Robert Noyce) is quoted as saying, Do not be encumbered by past history, go out and do something wonderful!
 
This is a picture of the early version. Note the LED is not mounted to the scope at this time. I have it dismounted right now as I am tinkering with some other aspects of the head and it was in the way.
Hope this helps
b
 

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I've had a round column mill for forty years. I have found the best approach has been to pre-plan my job so I don't have to move the head. Drills and reamers are the most problematic. To that end, I have a set of collets that I use for mounting drills and reamers. This brings them more in line with other tooling lengths. Manual tapping holes can be a problem as you have accommodate the tap wrench as well as the tap but in many cases, that part of the machining can be done as a last op and the head can be raised and positioned close enough for tapping purposes.

For those instances where the head height must be changed, I have used a dowel pin to rerefernce the table. I use a convenient hole on the wprk or mount an external piece with a hole on the table. The dowel pin is fit to the hole and the x position is recorded. The y position doesn't change significantly when the head is moved as the error is a cosine function. A .1" error in positioning the x will result in less than .0001" error in y. I have a DRO so I will set the position where the dowel pin fits the hole at .0000" in my absolute coordinates. For machining, I use one of the subdatum coordinates. When I move the head and re-reference the hole, I set the absolute coordinates to .0000" which repositions all the subdatum coordinates.

Without a DRO, I would just set up the head so the dowel pin once again slides smoothly into the hole and lock the head. It is more fiddly but its works.

As to the OP's method, along similar lines, I have made a spindle mounted microscope which will position to .0001". It can be viewed on a computer screen or a smart phone and is less of a strain on these old joints. https://www.hobby-machinist.com/thr...icroscope-aka-cheap-optical-comparator.38077/
 
My newbie method thus far: I use an R8toER32 adapter which drops tools down a bit over an inch, along with regular R8 collets, which are flush.

Allows me to move back and forth between longer and shorter tools somewhat. Along with planning out the job it mostly works.

In for hearing what you guys are doing.
 
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