A GREAT Idea that fizzled.

[Philipintexas]

A couple month ago there was an article in "The Home Shop Machinist" on a system to maintain alignment of the head of a Mill-Drill while raising/lowering it. Then in this month's issue someone suggests attaching an inexpensive laser pointer to the head, and drawing a a vertical line on the wall. Sounds good but I doubt my mill column is perfectly vertical and that idea didn't seem quite right.
However, the idea of a Laser pointer piqued my interest as I have a small level with a Laser pointer. I took it apart so I had just the Laser, and made a mount to attach it to the head pointing straight down. I made a target on a magnet to place on the vise and It worked like a charm!! Before raising the head, Align the target with the laser, raise the head, re-align the head/Laser on the target, and re-tighten the head.
It worked perfectly!! Couldn't be easier!
As usual, after doing all the fabrication and mounting the Laser, testing it and patting myself on the back, I thought I'd try the cylindrical laser in the chuck to see if I also had a convenient alignment center-finder.
Well, when I rotated the chuck the laser perscribed a circle about 1/2" in diameter! :wall: Of course a smart person would have done that FIRST!
The moral of the story is, even though the laser is cylindrical, there's no guarantee the beam is parallel to the body...

I still like the idea though and will keep experimenting. Just can't bring myself to spend $125-$185 on a laser center-finder.

***********************************The Rest of the story*********************************************
Well, maybe it's not a fizzle after all!
Even a stopped clock is correct twice a day. I only need accurate alignment of the X axis after the Mill-head is raised/lowered. My laser, even though wonky relative to it's axis, can be aligned by rotating it in its mount. So, with the Mill-head fully raised, I fashioned a fine-thread plumb-bob in the center of the laser bracket, hanging next to a steel rule held in my vice. Once it is motionless, I can move the table and accurately align the thread to an inch mark on the rule, probably within a couple thousands of an inch. Without disturbing the table, I replaced the thread plumb-bob with the laser, and by rotating it I accurately targeted the indicated inch mark on the rule, and carefully tightened my bracket making sure it held the aiming mark. As long as the laser doesn't rotate I have an accurate zero.

 

[Philipintexas]

After much experimentation, even switching to a Laser gun sight, I've come to the conclusion that a laser beam, given its .005" - .010", diameter dot, is no better than traditional methods of re-aligning the head of a Mill-Drill after elevating the head to accommodate longer tools. It's close, but lacks the definition to provide the required accuracy.

 

[petertha]

If I understand your problem & assume its the mill/drill that slides up & down a round column vs. a rectangular dovetail? Have a look at this sketch & see if something like this could be used.
blue box = mill head
black circle = column
orange circle = quill
green rectangle = laser pointer fixed/attached
red arrow = laser beam out
purple arrow = reflecting beam back
grey slab = mirror in fixed position (maybe on shop wall?)

With the mill head in position A, you adjust the laser pointer just so it returns a dot to some arbitrary spot on the head, make a tick mark there. Now move the mill head to position B. If the head has swiveled on the column, the dot will reflect back at a different position. Rotate the head about the column until the beam aligns to the original dot position. Actually, the further away the mirror is located, the more accurate it should be. I 'think' this principle should work even if the column is not plumb because the mirror is fixed. Maybe some math guys here can vet this with squiggles & greek symbols

 

[Philipintexas]

I like your idea, I found the problem to be the size of the dot being too hard to align accurately. The more distance involved, the less that comes into play. Your idea creates the needed distance. However, wouldn't the mirror have to be exactly parallel (vertically) to the column? The problem in using a truly vertical reference introduces errors if the column is not also perfectly vertical.?
Your scenario looks good if the head merely rotates, but the reality is, the head also moves vertically, and if the mirror is plumb(pretty impossible), the spot will be off?
This sure looked easy in my head, but it's an interesting problem.
My thinking is, if the column is not perfectly plumb, no other artificially plumb reference (IE: the mirror, or a plumb-bob) will work.?
Add to the problem, my column is probably out of plumb in both coordinates.....

 

[petertha]

Hmm... where's the local Math Whiz when you need them?

I've made this sketch with an exaggerated non-plumb mill post. It appears (to the naked eye at least) that it should be very minimal. I think its related to the tiny triangle size & angle of your mill axis relative to the huge triangle distance of the reflection path. As long as the pillar runs in a straight line (which it better) and the mirror is flat (which it should be).

You will have to pre-align the laser pointer to some arbitrary position in order to get a return dot at a convenient recordable location on the mill head. But after that the device remains fixed in that position as you raise or lower the head & you are only looking for a relative shift away from that original dot location to determine mis-alignment. And from I can tell, the mirror doesn't have to be plumb either, its just a planar reflector.

The rotation misalignment (rectangular mill head about the pole) is the same principle, but the dot should traverse laterally & be very exaggerated with the tiniest of rotation.

 

[canadianhorsepower]

This is what you are looking for the plans for this tool


https://drive.google.com/drive/folders/0ByWaTeq__NX1eWtXQjIwWnU3V0E

this is the video you want to watch

[ame]https://www.youtube.com/watch?v=otSjut1iGGk[/ame]

enjoy

 

[Cogsy]

Ok, I'm not a math whiz but I just plugged a couple of quick figures into your sketch and this is what I found :

With the mirror 300mm (roughly 1 foot) from the laser and hitting the mirror with a 5 degree angle, increasing the distance from the mirror by 1mm (allowing for the out of plum column) mathematically shifts the laser by about 0.09mm (about 3-1/2 thou).

Moving the mirror to 3 feet away produces about the same error (using the same 1mm out of plum figure).

So my conclusion is that the mirror and mill head have to be fairly close to parallel or the error will be significant.

 

[canadianhorsepower]

Ok, I'm not a math whiz but I just plugged a couple of quick figures into your sketch and this is what I found :

With the mirror 300mm (roughly 1 foot) from the laser and hitting the mirror with a 5 degree angle, increasing the distance from the mirror by 1mm (allowing for the out of plum column) mathematically shifts the laser by about 0.09mm (about 3-1/2 thou).

Moving the mirror to 3 feet away produces about the same error (using the same 1mm out of plum figure).

So my conclusion is that the mirror and mill head have to be fairly close to parallel or the error will be significant.

check the video it worth it

 

[Philipintexas]

Canadianhorsepower: Darn, you took all the fun out of this..

I liked that idea, it's really ultimately all about the chuck re-positioning, not the head. I'll explore that further. Thanks.

 

[petertha]

I liked that idea, it's really ultimately all about the chuck re-positioning, not the head. I'll explore that further. Thanks.

Sorry you have lost me now. The video CHP shows is a 'center finder'. The laser is contained in bracket clamped to the quill so for convenience the chuck or collet can stay engaged. It rotates with the quill, thus it draws a circle on the work piece about the axis of the quill. The circle diameter (or dot convergence) is dictated by mill head vertical height (assuming the laser pointer is fixed, not adjustable).

So now onto your mill. You have an inscribed cross or a drilled a hole. You raise the head. As I understand, the head is somewhat free to radius around the column because it has no dovetail so there is no guarantee your quill is concentric to original center. The laser center finder will illustrate this discrepancy. It will show a red circle which is offset from the center of your hole & so gives you all the information you require to re-position it back so it lines up concentrically (+/- the beam width of the laser which seems to be somewhat variable from what people say).

So it doesn't matter if your column is tilted back 5-deg & left 3-deg out of plumb because the whole assembly (quill, head, X-Y table) is coming along for the ride. The quill axis is parallel to the column axis (or should be otherwise you have other headaches outside the scope of this alignment issue). But it is somewhat unconstrained to rotate about the column axis.

If your chuck is not gripping concentrically or consistently, that is a separate problem over & above quill axis alignment.

Hope you have enough info to solve your problem. Good luck

 

[Philipintexas]

Correct. I should have said "Quill" alignment not chuck. The ultimate goal is to have a tool in the chuck pointing at the same spot, AFTER raising the head, and its having rotated somewhat around the column.

 

[canadianhorsepower]

Correct. I should have said "Quill" alignment not chuck. The ultimate goal is to have a tool in the chuck pointing at the same spot, AFTER raising the head, and its having rotated somewhat around the column.

You might consider this alternative also

http://email.villagepress.com/pub/MW/20101210/MW20101210.html

 

[Philipintexas]

You might consider this alternative also

http://email.villagepress.com/pub/MW/20101210/MW20101210.html

I have one of those. The problem I have is using the head low, near the work for say a center-drill or wiggler, then having to raise it for several different length drills working up to the hole size, then switching to a long shank chucking reamer or boring head. Every time the head is raised the zero is lost.

I'm going to explore the laser on a holder with the beam off center as shown in the video.

 

[canadianhorsepower]

I have one of those. The problem I have is using the head low, near the work for say a center-drill or wiggler, then having to raise it for several different length drills working up to the hole size, then switching to a long shank chucking reamer or boring head. Every time the head is raised the zero is lost.

I'm going to explore the laser on a holder with the beam off center as shown in the video.

As you notice the plans are there also.
and that guy Is simply awesome to talk to.
On your spare time check all his video (19 I think)
even after 35 years doing this I learn different stuff from them
enjoy

 

[clazman]

After much experimentation, even switching to a Laser gun sight, I've come to the conclusion that a laser beam, given its .005" - .010", diameter dot, is no better than traditional methods of re-aligning the head of a Mill-Drill after elevating the head to accommodate longer tools. It's close, but lacks the definition to provide the required accuracy.

Yes, this fascination with the laser is way over done.

 

[Wizard69]

Yes, this fascination with the laser is way over done.

I have to agree with respect to edge finders and the like. The only way you would get better accuracy with a laser is if you have a long baseline. For example across a room. Even then it would depend upon minimal beam divergence and the setup persons ability to see the spot.

 

[goldstar31]

My opinion- for what it is worth? I recall that the professionals aligned straightened motor vehicle shells with lasers. They used Plexiglas /Perspex cards with graticules and prisms. OK, prisms are in every cheap set of Chinese binoculars. Again, a Peter Rawlinson writing in Model Engineer did use cheap children's blackboard pointers whilst Michael Trethewey produced a his version for converted webcams. I wrote a bit to him about it. He was to update but the technology is there.

Again, back in the real world, my old Myford lathe bed on the slideways grinder was laser aligned.

The technology is already there.

Good luck

Norman