On the vices and joys of machine tool reconditioning...

[steamer]

and that I have not spotted clumsily (i.e., i let the weight of the part be the only downward force (well, if I pushed down it would be very lightly), and I moved less than an inch in 2 directions...

Oh-oh! Who told you this!?
To properly develop the spotting pattern, the part hast to be moved. The finer the scraping, the more it has to be moved. You need to give the blue a chance to be wiped away from the peaks and to build the bull's eye.
So place the part (that's how I do it) on the plate where no blue is, move it into the blue area and move it there in circles (so say figure 8, I don't do it so).
Diameter of the circle maybe 10 cm (not really that important). Maybe something around 5 turns.
No jerky moves, but smooth and gently. Grap the part so, that you don't tilt it. That means a bit below the center of gravity. That part is quite flat, so don't worry about that. Push it down a bit.


Steamer already mentioned the rocking test.
Sometimes, it is hard to hear wether it rocks, so here is a better way:
Lay the part down, put a DI on top of one corner and try to rock it diagonally (over two opposing corners). Repeat at a second corner, but not one diagonal to the first one


Nick

Wot Nick Said!.......

[ttrikalin]

and that I have not spotted clumsily (i.e., i let the weight of the part be the only downward force (well, if I pushed down it would be very lightly), and I moved less than an inch in 2 directions...

Oh-oh! Who told you this!?

Wot Nick Said!.......

I wanna say I read it but its a lie. I somehow formed this idea, and never gave me the opportunity to stand corrected -- until now. Duh.

You see why I do this thread? I am already learning that I've been chasing me tail...
OK I'll write more... and please pay attention and correct me!

thanks, sirs!

[MuellerNick]

Now, it would be interesting (at least for you) how different the spotting is with both methods. Without scraping in between.


Nick

[NickG]

Is it wrong that I am finding this quite fascinating?! 

I still don't understand though so am going to go back through the whole thing!

Nick

[steamer]

Now, it would be interesting (at least for you) how different the spotting is with both methods. Without scraping in between.


Nick

YES!......you find all kinds of sins when you do this...and it teaches to ask "The part"  lots of questions!.....The part will lie to you if your not careful!......

The problem is assumptions.    Don't have any assumptions and the part will not lie to you!

Dave

[steamer]

Try this one.....mark up the part....and note the marking.

NOW

Rotate the part 180 degrees and note the marking.....does it look the same?...

It might....it might not.... and it depends.

Dave

[steamer]

I'm at the final check in alignment phase....and I'm checking the cross slide squareness to the axis of the spindle.....I'll be doing the straight edge in the 4 jaw test...and hopefully, I won't need to adjust the saddle....I'll post here Tom...very briefly....how I'm doing it on my SB....as a reference...but it's in Connelly.

Dave

[Tennessee Whiskey]

Just a little scraping question. Can y'all scrape two pieces to the point that they will "wring" together like Gage blocks?

Eric

[MuellerNick]

Just a little scraping question. Can y'all scrape two pieces to the point that they will "wring" together like Gage blocks?

Somewhere in the net, I have seen a picture of a scraped surface mirroring a newspaper. It looked like a mirror, but it was scraped. 
I wouldn't try that. I think Forrest Addy made something like this. Or at least coming close to a mirror finish.


If that wrings together? Don't know!




Nick

[Maryak]

I believe it's possible but IMHO you need 3 pieces. Just using 2 will feed off each others error and so on and on and on..................

Best Regards
Bob

[steamer]

Nick,

Moore tool scrapes the ways of the jig grinders to .0000020"/24"....Then.....they lap them!....This becomes the ways for Roller bearing slides.

They are not mirror ....but they are pretty damn close!

NO I can't do that...but Eddie could!

Dave

[Dave Otto]

If you ever have a chance to get your hands on the book "Foundations of Mechanical Accuracy" or something like that; it is a big hardbound book published by Moore and has lots of pictures and theory about how and why they do what they do. When the guys are scraping, the machines are insulated with blankets so the body heat of the scraper doesn't warm the casting as he is working,

We used to have a copy in the Metrology lab at work but I'm not sure is is still there.

Dave

[steamer]

Thanks Dave!....I used to work there......

"Eddie"...who has been there over 30 years as a scraper....knew Dick Moore.

Dave

[Dave Otto]

Wow I did not know;

We used to have a Moore CMM (I'm not sure if that is what it was called) with all the tooling years ago in the lab and there was also a Jig grinder in the tool shop; beautiful machines .

Sadly do the evolution of the company they're gone now.

Dave

[steamer]

Nope....still there...though not making NEW jig grinders....they are rebuilding machines in Bridgeport.    I worked at their division in New Hampshire on Diamond Turning Lathes, but we had lots of stuff made in Bridgeport.......They still do contract manufacturing....but for special, tight tolerance stuff....

Dave