Author Topic: On the vices and joys of machine tool reconditioning...  (Read 43209 times)

Offline steamer

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Re: On the vices and joys of machine tool reconditioning...
« Reply #30 on: July 14, 2013, 01:51:17 PM »
And hey Tom....what are you using for a camera?....head on shots of spotting is hard to do... :ThumbsUp:

Dave
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Offline MuellerNick

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Re: On the vices and joys of machine tool reconditioning...
« Reply #31 on: July 14, 2013, 02:46:46 PM »
@Tom:
Except for the burrs, I do not see severe obvious errors. So, you should not be too disappointed by the critics. You are on the right track, and you are very close to a good result.
Also, the pattern of you scraping passes looks good to me. The more random it gets, be better it is. If you look at in which direction you scraped on a spot and the direction is random (half one direction, other half the other direction) you know that you are good or almost good. If all high spots have the same scraping direction, there is work left to be done.


I know how annoying scraping can be.  :cussing:


Nick

Offline steamer

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Re: On the vices and joys of machine tool reconditioning...
« Reply #32 on: July 14, 2013, 03:57:08 PM »
No critics here.  Keep gong Tom!

Dave
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Damned ijjit!

Offline ttrikalin

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Re: On the vices and joys of machine tool reconditioning...
« Reply #33 on: July 14, 2013, 06:03:20 PM »
No critics here.  Keep gong Tom!
Dave
@Tom:
Except for the burrs, I do not see severe obvious errors. So, you should not be too disappointed by the critics. You are on the right track, and you are very close to a good result.
Also, the pattern of you scraping passes looks good to me. The more random it gets, be better it is. If you look at in which direction you scraped on a spot and the direction is random (half one direction, other half the other direction) you know that you are good or almost good. If all high spots have the same scraping direction, there is work left to be done.
I know how annoying scraping can be.  :cussing:
Nick

Gents, 
I am very much in debt for the pointers, and I assure you, I have not taken the feedback the wrong way.

Your comments are already helping me break out of chasing my tail with the reading of the marking...

I did not reply this am, as I printed the comments and went down to the garage to have a go at it, and take photos... and now these are coming in installments in the next posts...

So what follows is:

1. a standardization of the amount of blue I put on the tombstone
2. the evolution of the markings after 2, 7 and 9 cycles
3. high magnification of the markings at 9 cycles
4. the planning to resurrect a dead-on-arrival VFD -- the suboptimal way ;) 

here we go... 

take care,

tom in MA

Offline ttrikalin

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Re: On the vices and joys of machine tool reconditioning...
« Reply #34 on: July 14, 2013, 06:21:06 PM »
Point 1. On the standardization of marking and reading.


What Nick described in the quotation below I have seen in practice. In fact, after a while, weaker characters like me might be tempted to thicken the dye on the tombstone, and pat ourselves on the back on work well done...

[...]  But I have to say, that the spots per square inch method is crap. Not the fact that you want to have a certain number of spots, but the fact that there is no repeatable way to measure them. Just make a thicker layer of blue, and the coverage shoots up. If the layer is thick enough, you have 100% :)

A better way is to observe how the spots develop. As long as they do get more, there is work left to be done. If they stay the same and you have to split them to increase their count, you can call it good. [...]

So I cleaned the tombstone well, with plenty of 90% alcohol...  I use the hi-spot blue (and nitrile gloves -- anastasia does not let me in the apartment otherwise.  :( )



I usually put the blue by eye, by smearing a decidedly smaller quantity than Mike Moore did in his video (to be expected -- he was demonstrating rough scraping  :facepalm: ).



But for today, I wiped that off, and decided to try something more repeatable... sort of... I do not have a precision scale, so a by-eye volumetric approach should do...



A dolop, a bit more than 3 mm in diameter:



This ended up being a tad thick, so I removed some by swiping most of it off from 1/4 of the 9" by 12" tombstone, and re-distributed it... 

I renewed the blue in cycle 6 -- and this may account for apparent differences in the photos that will follow...
« Last Edit: July 14, 2013, 06:24:08 PM by ttrikalin »
take care,

tom in MA

Offline steamer

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Re: On the vices and joys of machine tool reconditioning...
« Reply #35 on: July 14, 2013, 06:24:32 PM »
The "calibrated eyeball dolop" is how I do it too Tom...works for me
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Offline ttrikalin

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Re: On the vices and joys of machine tool reconditioning...
« Reply #36 on: July 14, 2013, 06:44:05 PM »
Point 2. On the evolution of marks and the need to deburr (always deburr)...

[...] I have a question about the stone you guys use for clearing the burrs, I have seen this stone mentioned in some videos I have been watching, its a tin flat black stone...
[...]

So this is the stone I use... I was supposedly a slip stone, of the soft arkansas variety, which I got online for a few bucks (too expensive still -- but I have this as a hobby so I do not really ponder the pennies...)



Dave was right --  :embarassed: I was not paying attention to stoning. I was also using the stone pretty loaded. So I cleaned the stone, and listened to its sounds after each scraping pass. There is a distinct cutting sound that I think corresponds to the raised burrs being knocked down (cut?) by the stone. After a couple of easy passes the sound and the resistance vanish, and the stone slips smoothly over the surface.

Next post is my understanding of how the burr is raised while scraping... also based on connelly's descriptions and stuff I may have read here or elsewhere.... so please correct me... 


take care,

tom in MA

Offline ttrikalin

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Re: On the vices and joys of machine tool reconditioning...
« Reply #37 on: July 14, 2013, 07:12:16 PM »
Point 2, continued.. .On the nature of burrs...

So this is my understanding about the nature of burrs, based on observation, and on what I've read in Connelly's book, and what I've read on this forum...  Please correct me if this is off....

When we cut with the scraper, there is a lip of metal that is left behind, at the end of the stroke. The schematic tries to show this... it is not accurate of course in that it is not to scale, and that the deepest point of the cut is drawn near the lip (burr). The deepest point of the cut should be closer to the midway of the stroke, and the blade should start coming up before the end of the stroke. Well, I probably scrape the wrong way (i.e., as I drew...) So in some twisted sense, my drawing is accurate!



So when we stone the work, we knock down the lip raised by the blade... I think... 



tom
take care,

tom in MA

Offline steamer

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Re: On the vices and joys of machine tool reconditioning...
« Reply #38 on: July 14, 2013, 07:25:51 PM »
Point 2, continued.. .On the nature of burrs...

So this is my understanding about the nature of burrs, based on observation, and on what I've read in Connelly's book, and what I've read on this forum...  Please correct me if this is off....

When we cut with the scraper, there is a lip of metal that is left behind, at the end of the stroke. The schematic tries to show this... it is not accurate of course in that it is not to scale, and that the deepest point of the cut is drawn near the lip (burr). The deepest point of the cut should be closer to the midway of the stroke, and the blade should start coming up before the end of the stroke. Well, I probably scrape the wrong way (i.e., as I drew...) So in some twisted sense, my drawing is accurate!



So when we stone the work, we knock down the lip raised by the blade... I think... 



tom

Yes...that is pretty accurate...at least from my perspective...your should lighten the stroke just before you finish so it doesn't leave as much of a burr....but for the life of me I don't know how to teach anyone that.....I leave some burrs...but not too bad...but I do stone my work.    Your stone looks much nicer than mine...but is similar...I dress it on 150 grit sandpaper every once in a LONG while...but otherwise I just use it.

When you mark up the part, if there is a burr on it , or dirt, or chips...the moment you move it on the "tombstone"...you will feel it, and you will hear it...it sounds very different...and you will see swirls in the marking medium.....

Dave

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Damned ijjit!

Offline ttrikalin

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Re: On the vices and joys of machine tool reconditioning...
« Reply #39 on: July 14, 2013, 07:27:25 PM »
I should get a photo of the work after a pass, before and after the stoning... and with tangential light...  till then... Take a sneak peak through the microscope... I know the picture is crappy, but I am holding the camera to the eye piece... Magnification is (I think x20) -- I do not recall the setting.

The red ellipse shows a stoned burr (from a previous cycle) on a spotted surface. The stroke is light, and the radius is small, so the width of the cut is small (~2mm), and the cut is shallow. THe red arrows show the direction of some cuts that have been overlapped by other cuts... The upper one, pointing to the ellipse is the cut that generated the aforementioned burr. The other arrow shows another cut, in a different direction... 



more later, baby woke up... 

t
take care,

tom in MA

Offline MuellerNick

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Re: On the vices and joys of machine tool reconditioning...
« Reply #40 on: July 14, 2013, 08:50:12 PM »
Tom, your method of finding out the thickness of the blue won't work that well.
Make a very thin layer and pick up all the blue with your work. Means: Spot, wipe off from work, spot, ... until the work no longer picks up blue. Part of the blue still will be sitting in the many pores of the surface plate. These pores are a desirable property.
You will find out, that it takes much more blue on a fresh plate than it takes on one that you have been using after cleaning.


Nick

Offline ttrikalin

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Re: On the vices and joys of machine tool reconditioning...
« Reply #41 on: July 14, 2013, 09:50:37 PM »
Tom, your method of finding out the thickness of the blue won't work that well.
Make a very thin layer and pick up all the blue with your work. Means: Spot, wipe off from work, spot, ... until the work no longer picks up blue. Part of the blue still will be sitting in the many pores of the surface plate. These pores are a desirable property.
You will find out, that it takes much more blue on a fresh plate than it takes on one that you have been using after cleaning.

I hear ya... The standardization is simply for meself... I scrape for 2 hours every two weeks, and by the time I start getting the hang of it I stop... So this thread is a reminder for me too...

btw -- I tried spotting with a banana, as shown in the video you posted, but it didn't work too well for me... When I ate the banana I also ate some Dykem blue, and now my tongue is blue  :P
take care,

tom in MA

Offline MuellerNick

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Re: On the vices and joys of machine tool reconditioning...
« Reply #42 on: July 14, 2013, 09:55:03 PM »
Quote
and now my tongue is blue


I want a video of it! :LittleDevil:


Nick

Offline ttrikalin

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Re: On the vices and joys of machine tool reconditioning...
« Reply #43 on: July 14, 2013, 10:05:24 PM »
2.  Evolution of the markings...

It seems to me that I am chasing my tail... but I am not sure...  I am sure I am not consistent in my scraping force -- I have only a few hours' experience, and scattered...

This is where we left off yesterday...



I wiped it off, stoned it, marked again, and after two passes:



and after three passes ...



After 7 passes...  (blue was added in this spotting).



and after 9 passes...



In the next post, I will mark which areas I see as "good" and which need more work...

t
« Last Edit: July 14, 2013, 10:13:01 PM by ttrikalin »
take care,

tom in MA

Offline MuellerNick

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Re: On the vices and joys of machine tool reconditioning...
« Reply #44 on: July 14, 2013, 10:25:01 PM »
The only conclusion I can draw from the pictures is, that you are scraping too hard.
That makes you an exception!


Do only scrape the spots with an eye (better just the eyes, not the whole blue spot) and only something around 3 strokes. Light strokes.
Take a picture of two consecutive passes.


Nick