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  #21  
Old 07-10-2016, 03:01 AM
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1. To wrap things up, I welded in the angled brace to the tab on the backplate and to the new sleeve.

2. Installed one last time.

3. View from the top.
You might notice that I turned the bearing sleeve upside down from the first time I showed it because the bearing is now flush on top. It just worked out better that way for installing the brace.
For some reason I left about 3/8ths" of the other sleeve extending out downwards & exposed. I either forgot to trim it or or just decided I didn't care.
As my dad used to say, "It ain't hurtin' anything" so I probably decided just that. Mildred doesn't care either.

4. We had a visitor at some point; I believe it was in November of 2014.
I can tell from this picture that I was still tinkering with it because the lower socket is still clamped to the base in this picture.
This picture shows you a pretty good view of the overall thing from the front side.

5. I did eventually screw the last part down after I was through tweaking it as best I could. I actually wound up forcing the socket forward a little bit to sort of preload a little bit of pressure on the guide rod. Only then did I locate and drill & tap the final two hole in the base. It just worked better that way.
That few pounds of force on the guide rod was the key for getting the loss of registration down from .0010" or .0015" to the .0001" -.0004" that it is now.

Now a final word or several about that reading:
The test bar that I was using is hardly guaranteed straight anyway. It is a possibly 75 year old boring bar from my maternal grandfather's machinist chest.
Secondly, the spindle and the quill don't necessarily run absolutely true either, neither up & down or in rotation.
There can easily be a thousandth or two runout using any tool you stick in the collet. This was after all, a $400 Harbor Freight mill to begin with.
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  #22  
Old 07-11-2016, 06:28 PM
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Quote:
Originally Posted by MarkBall2 View Post
Rod,
The walking back & forth when you crank the handle is why I used my crank arm as the slider attach point for the bar. (if that makes sense)

For adjustment I have bronze flanged bushings that slide on the rod & slotted the flange they ride in. That slotted flange then slides in the bent 3/8" bars welded to the crank extension.

By having the crank handle far enough away, I get minor deflection when I raise or lower the head. To adjust the "anti-pivot" bar, I left everything loose, then made the head square with the table. Locked down all the adjustments & it stays square when up or down.
Mark, I have studied your pictures several times and thought about what you've said here again.
The only conclusion I can reach is that your mill must not, indeed cannot, have as much inherent tendency to twist built into it to as Mildred does.
I have no way of measuring the amount of force involved but it is surprising.
There really is no reason to expect that two Rong Fu mills from even the same production run would behave the same way anyhow.

If Miner did want to rotate as badly as Mildred then I believe it would shift something in your yokes or in the crank assembly, or I bet you that 3/4" bar would flex enough under travel to be very noticeable. She definitely flexed the 3/4" bar I used on my first attempt.

That's one reason I bolted and braced the lower mount to Mildred's base instead of using a second yoke. I also figured the 1 inch bar was too heavy to be supported by the yoke arrangement.

Clive, I found one more picture of the overall assembly from the backside.
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  #23  
Old 07-11-2016, 07:03 PM
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Very nice job!!!! with a lot of head scratchen I bet. Any idea about time it would take to do another verses the time that you have in this build
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Old 07-11-2016, 10:12 PM
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After looking at the back side of your bar/mounts, I can see where it should work similar to Miner's.

Maybe the torque of the motor is trying to twist the head?
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  #25  
Old 07-13-2016, 01:42 AM
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Quote:
Originally Posted by MarkBall2 View Post

Maybe the torque of the motor is trying to twist the head?
Nope.
In the first place I've watched it go up & down at least a hundred times, more actually, without the guide bar. It will wave back & forth past center some of the time & does not necessarily ever behave exactly the same way two times in a row. It does favor moving to the left more than to the right.

Secondly, the motor is mounted to the head casting so any "torque" would be like an isometric exercise, pulling against itself.
As far as drive motor rotational or centrifugal torque, it is horizontal, 90° to the column.

Third, the dc motor is variable speed, meaning that I can soft start it but no matter whether I ease into it or start it fast the head will move at some point during travel, not necessarily at the beginning. And it always liked to move more towards the top of the travel.
It always moved radically when I had to crank it.

Quote:
Originally Posted by digr View Post
Very nice job!!!! with a lot of head scratchen I bet. Any idea about time it would take to do another verses the time that you have in this build
I've thought about that overnight, Ted. While it's true that I wasted probably 85% of the time figuring out what I wanted to try I always have a difficult time duplicating anything. That's partly because I always think I can improve it and partly because I don't like to do the same thing twice.

Then there are parts. I only had the one 1 inch bar. The only parts I had to buy was a 1" bushing 6 inches long but I would have to find/buy another chrome rod.
Duplicating the yoke & the base plates would be easy and I would definitely want to simplify the bearing carrier sleeve situation. No way I want to bore out another chunk of that 2 inch bar, which was probably an axle but whatever it was, it was something extremely tedious for me to work.
So right away I'd get into changing the plan.
If I could find a 2 inch slug already drilled out to 1 inch it would certainly simply that.

There still has to be some way to align the bearings perfectly in line with the column. I believe that it has to turn out with less than one degree or error.
I wouldn't expect anyone else to approach it the way I did.
On the other hand, it did work.
But there should be an easier way.

The real nut is I wouldn't have high expectation of this working without getting rid of that crank. I think the dc motor drive makes it possible by turning the gear without a bunch of jerking back & forth.
That part of the project - building the power lift - took a lot of time too.
I don't have another 1/4 hp dc gearmotor like that either.

So the answer is, I really don't know but I am definitely glad I don't have to do it again.
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  #26  
Old 07-13-2016, 07:04 AM
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I really like the dc motor lift, I will let it simmer away for a while before I start but I will definately motorise the lift. Many thanks for all the photos.
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  #27  
Old 07-13-2016, 07:13 PM
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Quote:
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I really like the dc motor lift, I will let it simmer away for a while before I start but I will definately motorise the lift. Many thanks for all the photos.
Clive, I dug out the thread about the Mildred's Uplifting and read through it again. You are not among the commenters to it so I thought you might have missed that build project.

As usual, this was an experimental prototype, wordy & tedious build project with lots of sidetracking & me just having fun.
But I did learn a few things along the way so it might be helpful to you if you haven't read it.

Reading it again highlighted the importance of one thing: if you use new sprockets, which I did, use new chain!
It will probably save you a lot of screwing around.

I happened to have a bucket full of used #50 roller chain that Old Man sent me several years ago for some reason & I tried using it just because I had it.
Caused me a lot of lost time until Ironman pointed out the folly.

I can assure you this is worth doing for anyone who has one of these little mill/drills.
I was very negligent about moving the head to facilitate tool or collet/chuck changes so long as I had to crank the thing up & down. This meant I would likely try to run Mildred with the head too far away from the work, spindle extended, a lot of the time so I could switch between collets & drill chucks without moving the head.
Or I would shift the work between the mill & the drill press instead of using Mildred for both operations just to avoid that damned uncomfortable crank.
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