Resusitating Some Chinese Iron

Baithog

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Quite a few years ago I finally managed to save up enough to buy a little HF mill. I had no illusions about the quality I was getting. Getting was way better than not getting at all. The ways were warped so that several inches of travel wouldn't travel. I lived with it for years, being creative about work piece sizes. A year or so ago I hung stepper motors on the little mill to do CNC. That made made the problem unworkable. Years of using nothing but the center of the table had aggravated the original problem with wear. CNC meant that I couldn't selectively lock one axis or the other, or do gib adjustments on the fly. So the machine saw little use. The sale of some of my other toys and a deal with my wife got me a larger mill/drill. I considered converting it to CNC, but I like the feel of manual control. It did occur to me that the mill/drill was just large enough to re-machine the X2's ways.

Two weeks ago I got up the nerve to mill the X-axis table and saddle. Not being very patient, I assembled the table and saddle with the old gib. It slide smoothly from end to end with no wobble. I was very pleased with myself, but all was not well. Wear marks from the first slides showed that I had very little bearing surface. If I don't do something to smooth the ways, I will quickly be back to where I started. I have spent hours reading rancorous discussions on the net about the merits of lapping versus scraping.

Enough of boring you with background. I think I want to scrape the ways, and I think that I have a plan. Assuming that I can teach myself to scrape, this is it.

  • Machine a cast iron dovetail master.
  • Scrape in the master.
  • Use the master to scrape in the bearing flats
  • Use the master to scrape in the table dovetail ( or should it be the saddle first?).
  • Scrape the saddle to the table.
I plan to scrape in a block plane and a angle iron for practice. Does the above plan sound way too ambitious for a novice scrapist?

Saddle
 
ambition is the key to success my friend.
practice will assure your outcome.

do this any way you wish, but i might suggest...

if you have, or can get a surface plate of desired accuracy,
you can scrape each flat surface from the surface plate's reference.
then use the dovetail master you scraped from the surface plate to master the dovetails.
it may save you some time.
 
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Gotta start somewhere...........Sounds like you have a good grasp on you plan and results..... a china man mill sounds like a worthy place to start.

Tim
 
Second a surface plate. You are dealing with small mill parts and it is easy to roll out some bluing on the surface plate and spot the parts. Still have a tube each of the yellow and blue that "he who shall not be named here" gave me at the scraping class. I should of taken some pictures of my last scraping job to illustrate here. But you should find some videos on You Tube.
 
Gawd scraping is tedius, I have about 18 hours in both hand and powered scraping on my lathe saddle and cross feed. I am only about 1/4 of the way done. I was getting frustrated so I started to do 2 different pieces just so I could feel like I was making progress between the two. I have someone locally who has given me some pointers on scraping but I am still learning. I now have to make a new gib for the cross feed and eventually the compound rest. Here is some of what I have so far....Tim

1227151505.jpg 1227151537.jpg 1229151347.jpg 1227151120.jpg 1230151332.jpg
 
Yes, scraping can be tedious.
However, it fun for me to watch and understand that observing a real machine tool rebuilder scrape is efficient and quick. Seems job that takes me several hours takes them 20minutes.
And their results are better!!
Practice....

Daryl
MN
 
I am working my way through "Machine Tool Reconditioning". The description of how to sharpen the scraper has me confused as to what I'm trying to achieve. I sacrificed a very worn Nicholson
file and was not able to get it to cut cast iron. It would help to have a properly sharpened scraper to examine and try out, So I guess I have to get off the pot and order a real scraper. I am tempted to get an 18" tubular handle with a HSS blade. I can hone HSS as I have hard arkansas stones and razor hones for my plane irons. That way I can start experimenting with the angle plate. On the other hand I will probably have to get a carbide blade eventually and build a lapper.

I found some descriptions of home built lapping setups. They are based on available motors. Most of the descriptions use a cast iron face wheel. There was at least one mention of using aluminum or brass for the wheel. I have 5" aluminum stock. Would embedding diamond past into aluminum really work?

Is 9micron the right paste, or should I go down to 7micron?
 
to make a scraper from a file, you'll want the edge to be at about 3*negative rake
or you can make a sharpener like i made...
 
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