Scraping straight down and datum points

[ThunderDog]

Hi all,

It's been a little while since I've touched some scraping projects. I've been on a roll of machinery upgrades, namely the new to me Wells-Index Super 55. But, that has only lead me back to scraping and checking of machinery. As I've been reading Machine Tool Reconditioning(RTC), I've noted the sequence clearly outlined on where to start checking and where a scraper would begin. If I'm understanding this correctly, the book lays out that a datum point for a vertical mill would be the spindle. Using that as the datum point, one would progress to a sequence of checks starting on the column, then to the knee, etc., etc. There is a part of me seriously contemplating such a project, but I may hold off for now. However, I still want to work through the exercise of checking the state for all ways and sliding members. As you will see the machine is going through a complete tear down. The spindle has been sent to Wells-Index for a regrind to R8. I'm asking the following:

Could the mounting plate for the vertical head be the datum point? This machine does NOT have the ability to nod the head. RTC recommends laying the column down to scrape the flat ways and then rotate the column to scrape the dovetails. My cast iron plate is large enough to cover the entire surface of the column way and it has two rods that can be used to easily maneuver the plate. Should I go for it or is there another method to check the vertical head mount relationship to the column way? I was considering a straight edge held flat against the head mount and extending down. This would allow me slide an indicator across the straight edge.

Second question:

Does one HAVE to start at the datum point and then proceed to the knee, saddle, then table? I ask because a quick check shows that the table retains original scrape marks at the ends and has .002" of wear in the middle. According to the text, if original factory scrape marks are present I should be able to use the original scrape marks as my starting point and scrape to the lowest point. Thus scraping straight down.

Alright, I'm tired. Hope all of this makes sense.

 

[Bob Korves]

Usually one tries to find areas that are factory ground in the same setup the ways were ground in. My take on Machine Tool Reconditioning's sequence for correcting the geometry of vertical milling machines is to do the column ways first, using an unworn reference surface on that face. Your Wells-Index does not seem to have an unworn face in that plane...

Looks like plenty of wear on some areas of that mill.

Let's hear Richard's take on it...

 

[Richard King 2]

The MTR Book (Connelly book) has been referred to as the MTR book for years. I have never seen it referred to as what you used.

One must understand the Connelly book was organized by Edward Connelly and he did not write all of it. He wrote parts of it and if you look at the beginning of the book he acknowledges several companies for their contribution to the book.

Much of the book was written by machine builders and many of the drawing in the book were drawn by Connelly who was a technical trades school teacher who had never scraped anything. He guessed. Many professional machine rebuilders laugh at the book. I sell the book and reference it all the time, calling it the Bible of Rebuilding. But as in the real Bible everything inside has to be looked at as a story and look for the meaning.
Or that's the way I look at it.

The better reference book for tests is The George Schlesenger book Testing Machine Tools. Many of the tests that Connelly used came from the TMT book. All specs written over the years were based on the MTT book and not the MTR book.

https://pearl-hifi.com/06_Lit_Archi...s/Schlesinger_Georg/Testing_Machine_Tools.pdf

The rule of thumb professionals use on rebuilding a mill is:
1) If the spindle is fixed or runs through a casting like a Horizontal Mill and cant be adjusted then you start at the spindle datum and work from that. Up and out as your following the spindle bearings axis.
2) If the spindle can be removed and can be aligned by either adjustment like a Bridgeport by worm and worm wheel or like your machine the head alignment can be tweeked to align you start at the column and work up. Scraping the head to align with the rest of the machine. A whole lot easier scraping that little flange last then scraping the machine from it.

Many make the mistake of scraping a machine when the spindle is out of the casting, scrape the machine from the worn ways, then slide in the fixed spindle that can't be adjusted. Make the tests and see the mis-alignment and then have to start all over.

As a rebuilder and you being a detective you measure the machine from unworn areas and figure out why and where the machine is worn and how much. One needs to know that Mill tables bend and by micing (measuring with a micrometer) it only you assume the table is only worn in the middle your making a mistake. . But if you flip it over on a granite table setting it on 3 points or 4 points and shimming it and measuring all 4 corners so they are shimed to the same height. You will run a height gage over the entire length of the table top you will see the table (top) is bent convex because when the Tee-Nuts were over tightened the table stretched (Peened).

The scores you are pointing at is a super example of lack of lubrication and the ways rung together and pulled out the metal. If it was dirt or chips the scores would extend all the way out to the end of the ways.

You need to clean up, lay the column on it's back and be the detective and measure from all the original machined areas of the machine that were not wear areas and use those areas to guide you to bring it back to the original datum's.

Another ways rookie rebuilders do is square everything a perfect 90 deg. like the knee. They fail to think about how cast iron bends and sags. I also would recommend you Prepare or as I sometimes say "pre-qualify" the ways before using them as a reference to match fit ways to each other.

More later as I am also getting writers cramp. Rich

 

[ThunderDog]

Richard, thanks for the reference pdf.

This was my thought process:



Or is that flawed due to this(see below)?


Probably best to wait for the spindle to be returned after the regrind from Wells-Index.

 

[Richard King 2]

The top edge of the knee and bottom edge seldom saw any wear and you use that for reference. You know I have been rebuilding machines for 50+ years and don't come on here and guess at this. You can do it your way and stumble learning how. I am trying to tell you the way I was taught and have taught new machine builders and machine rebuilders. measuring off that small surface to scrape the column knee and table is a BIG waste of time. Do it your way . I was paid to do it and I gave a 1 year guarantee on my rebuilding to be as good or better then new machine accuracy. I never had to go back and rescrape anything in all those years. The spindle head is fit on the machine the last thing you do.

 

[ThunderDog]

So, I'll summarize my idea for future readers, "It's the wrong idea and causes more work and inaccurate work".

You know better than me and I'm not contesting your knowledge or skill.
But, you do know I'm the rookie who will ask rookie questions, right?
Just trying to learn.

I'll continue getting things cleaned up and work on laying the column down. Stay tuned.

 

[Richard King 2]

You seem to always go off in a rookie direction. You read various pages in the Connelly book and interpret it your way. Scraping that machine is easy....so easy, nothing complicated to it at all. I am a Journeyman Machine Tool Rebuilder. I have been rebuilding Jig Bores and Vertical Machining centers....consulted in Taiwan at new machine builders for over 30 years. It is obvious your self taught and you are trying to teach with guesses as you have never done one before. You can do it your way, but when I see you are doing it wrong I will tell the readership the mistakes your making. I hope I don't come off as I'm bullying you. Just telling you the way it is. I would love to teach you the right way and save you a lot of time. Be a detective and dismantle the machine completely and measure things. I am not going to argue with you as I said scraping that machine I easy for me.
Here is another book you need to read. I read it 40 years ago. Connelly book acknowledgement page, Award I was given buy TAMI Taiwan Association of Machinery Industry

 

[Richard King 2]

Check out my web page Handscraping.com

read under testimonials. Here is an example.

"Ever since you instructed our first group of rebuilders, we have had numerous requests to have you back to instruct the remaining rebuilders. Your ability to adjust your class to fit our needs left a lasting impression.
Even though our rebuilders are experienced at scraping, they learned new techniques to improve accuracy and efficiency. The rebuilders had a lot of praise regarding the class and recognized your expertise as you worked along side them.
I strongly recommend King Way ... seminar for instruction in Basic 40/40 Hand and Advanced Machine scraping. It is excellent for anyone who is doing machine rebuilding or slide retrofitting."
Norm J.
Supervisor Machine Rebuild • TIMKEN • Canton, OH 44706

Thunder no offense but I have a few years under my belt helping people rebuild machinery.

 

[ThunderDog]

I will agree that trying to figure out the tone of an email, letter, or post can be challenging. I DO NOT BELIEVE that you are attacking nor do I think you're bullying in ANY WAY. I completely hear what you're saying. I do not post with any mind set of knowing much of anything related to machine tools, machinists knowledge, etc. I take your experience and knowledge as a valuable resource.

trying to teach with guesses as you have never done one before.

I'll be the first to say that I'm not here to teach a single thing. That's why I ask questions. I completely agree that I have NEVER scraped a machine. Shoot, I've never even scraped a dovetail. I'm a straight up 100% rookie. But, I want to learn and I want to learn how to do it right.

Trust me, if I had more cash I would sign up for your upcoming Ohio class. But, my wife might be a little upset after having just picked up this machine.

I'll read up on more of what you shared with me. Thanks.

 

[Richard King 2]

where you from? I sometimes give away a class to someone with a hardship. If you live close, maybe we can work something out.