[Vogavt]

I've read through multiple posts on the net for how to perform the alignment of the Mill head to the column and Lathe Head to the lathe bed. I've seen shortened versions where a perfectly straight and cylindrical rod/tube is used. I've also read the versions to remove the error due to non-concentric rods.

So first off, let me say I don't want a "my method's better than your method" sort response as I've seen lately. I would like to gain some insight as to differenct scenarios that one might encounter during this process so this thread can be useful for the betterment of all. I'll post links I've found at the end.

I'll start with the first scenario (mine) to kick this off.

Mini-mill:
Head and column removed, laying face up on my workbench
My DTI measures in 0.0005"
Using the gadgetbuilder shortened method.

Measuring for Y-Axis tram, I've got the DTI located on top of the rod, near the spindle and have it zeroed at the center of the positive and negative swing (0.001" on both sides). When I move the head up the column to measure the rod for the "distant" reading I'm seeing the following. The DTI now shows a +0.0085" and a -0.01425" at a distance of 4.95" away from the near spindle measurement.

Summarized:
Near Spindle
High +0.001"
Low -0.001"

Away from Spindle (4.95")
High +0.0085"
Low -0.01425"


From what I understand, this indicates the spindle head is nodding forward, i.e., the rod tip is closer to the column than it is toward the machinist.

I'm confused from all the reading whether I'm supposed to add or subtract the numbers before dividing by two. One says one way will provide indication of "out of roundness" of the bar, another says it cancels out the radius, and another says it indicates deflection off the center of the axis. One says you don't need a test bar and another says do it this way if you have one.

Can someone tell me exactly how much I'm out of alignment and explain how you're arriving at your answer?

Thanks in advance,
Vogavt


Original Rollie's Dad's Method

Mathematical Analysis of Rollie's Dad's Method

[nomedia="http://www.youtube.com/watch?v=ZaIuHNFIFNw&feature=player_embedded"]YouTube - Rollie Dad Method - Spindle alignment on my 7x14 Lathe[/nomedia]


gadgetbuilder's Method

Jose Rodriguez's Method to Make a Test Bar

[Vogavt]

Well after reading again I noticed the point to tighten the gib lock down while taking readings, so I went back to the shop and had another go at it.

In the Y-axis I'm reading 0.0015" on either side next to the spindle. Away from the spindle I''m reading 0.0050" on either side. Seems odd but true.

If I subtract one from the other, and while accounting for the signs, I get 0.010"/2 which says I'm off 0.005". Problem now is, which way?

(0.005-(-0.005))/2 = (0.005+0.005)/2 = 0.005"

If I add the numbers, again accounting for the signs, obviously I'll get zero, so it appears that I have no issues with it being in alignment.

(0.005+(-0.005))/2 = (0.005-0.005)/2 = 0"


Moving on to the X-Axis, I'm also reading 0.0015" on either side next to the spindle. Away from the spindle I''m reading 0.01375" on one side but while rotating the spindle the number climbs past the 0.015" mark to the 0.0065" mark which is actually 0.0085 past the 0.015. By adding them together I arrive at 0.0235". So now my readings at the away spot appear to be 0.01375" and 0.0235".

Adding and dividing by two = 0.0186" out of alignment
Subtracting and dividign by two = 0.0487" out of alignment.

Two different numbers for the X-Axis.

Anyone care to take a stab at explaning which is correct and what the other means?

Vogavt

[SCzEngrgGroup]

At each position, ADD the two readings, then divide by two. Once you've done this, you have the average position near the spindle, and away from the spindle. Ideally, these will be the same, but if they're not, then subtract the far reading from the near reading. If the result is positive, then near end is higher than the far end. If the result is negative, then the far end is higher than the near end.

Regards,
Ray L.

[Vogavt]

Based on feedback, I've created a spreadsheet to assist in calculation.

Could someone look it over before I put it in the files folder?

Any additional feedback would be welcomed!

The file is in the newer *.xlsx file format.

It will take some work to move it backward to *.xls.

I'll wait on feedback to see whether it's worth the effort.

[Vogavt]

Finally purchased at 15" Drill rod, with near straightness and decided to test this. Holy Cow! Am I supposed to be able see the end move through a path that looks like a cone? I trued/zeroed the bar near the chuck (4 jaws), but when I rotate the spindle the flailing around of the bar is extremely visible at the end.

Without disturbing the indicator I moved it to the tailstock end (free, not using tailstock center) and it appears to be about the same amount +/- on either side of the zero. But again, this REALLY looks odd!

And yes, the rod looks straight when placed against other flat surfaces.

[pete from TN]

How thick is your rod?:stickpoke





I think you are way overthinking this... As much as I hate to say it...maybe this video series on tramming Hoss made will help you here...

[ame=http://www.youtube.com/watch?v=RlSa5bu2aK8]G0704 Tramming Part 1.wmv - YouTube[/ame]

It is the simplest and best description I have yet seen of how to properly do this. good luck man...peace

Pete

[philbur]

You will be very lucky if the jaws of your low cost chuck will hold a 15" rod parallel to the rotation axis of the spindle to any degree of precision. Hence RDM.

Phil

Finally purchased at 15" Drill rod, with near straightness and decided to test this. Holy Cow! Am I supposed to be able see the end move through a path that looks like a cone? I trued/zeroed the bar near the chuck (4 jaws), but when I rotate the spindle the flailing around of the bar is extremely visible at the end.

Without disturbing the indicator I moved it to the tailstock end (free, not using tailstock center) and it appears to be about the same amount +/- on either side of the zero. But again, this REALLY looks odd!

And yes, the rod looks straight when placed against other flat surfaces.

[Maglin]

Why are you using such a long rod on the lathe? Are you trying to get the headstock spindle on axis? Their is not much you can adjust on a lathe. For spindle center line use a 1" TGP steel round that is 6" mounted in a 5C collet and put a indicator on the cross slide to get your headstock dialed in. Hugh PITA but pays off with high precision straight turning. Then use a 1" round steel stock 12-14" between centers to make a test bar to align your tail stock. Past that I don't know what else you can adust on a lathe minus gib tightness.

And for material deflection the Machinery Handbook has a really nice section on how much a certain diameter of what material will droop over a certain length. Can't help with your mill as I don't know the method you are employing.

[Vogavt]

The Drill Rod is 1/2" thick and I chose that length so I'd be sure to have enough in the spindle to secure it and leave the maximum out to measure against.
Okay so the distance from the where I zeroed the rod just slightly away from the jaws of the chuck to the point I used to take the vertical measurements near the tailstock (free end, no tailstock used) is 7.727". I got (-)0.010 and (+)0.0015. So it appears according to RDM that I'm out 0.0043 over a distance of 7.727" or 0.00055"/inch. Correct?
And the horizontal was (+)0.005 and (+)0.0095 over 6.567". Again using RDM, it looks like I'm out 0.005" overall or 0.00076"/inch.

NOT bad, if my math is correct and I understand the calculations.

Being new to turning, I can now see that I must need to chuck up long pieces with a small portion sticking out of the jaws, do the center drill, then move the rod out closer to the tailstock. Obviously I can't drill the end with it flailing around like this. Am I right? Is that how you all do it?

[Maglin]

I do everything as close to the chuck as possible. When having to go out more than 6" I like to use the tailstock along with the chuck. For accurate work I'll go the distance and put the work between centers. With my current lathe it's a PITA to take the chuck off put the faceplate on and then mount it up. With a camlock spindle it's a hell of a lot faster to go from chucking to mounting between centers.