To lap or not to lap

I have to say that all of this is a bit disheartening. I think I'll just put things back together and just use the machines for a few months and then revisit this issue. I've cleaned the Permatex off the cross slide and oiled so no harm done. Thanks for all of your comments.

Steve
 
Codeman
It's all part of the learning process.
Holding off on that for now is a good plan and lapping isn't the way to go.
If your machines dont adjust or preform as you expect then it will be easy for you to do a bit of research and set up
to scrape them in at you're convenience.
First big lesson done! Welcome to the machinist world.
 
Andre said:
Plate glass, float glass, etc is NOT flat! If you want to get glass flat you have to get three plates and lap them together.

http://www.myheap.com/the-notebook/homemade-surface-plate.html

I've measured how un-flat various glass is, with a cast iron surface plate under it to keep it from warping, and is was not flat.
Click to expand...

How un-flat was it? The sheets I use are flatter than anything I've got to measure them with (which isn't saying much) and are also flat enough to have considerably improved the ways on my Chinese xy table (which is also not saying much).
 
CODEMAN, there is a saying in the auto racing world "Speed is expensive, how much do you want to spend?". Translated to machining "Precision is expensive, how much do you want to spend?"

First question to ask is "how precise do I need this machine to be?" I manufacture fly fishing reels which require a certain amount of precision. But, through thoughtful design and understanding the characteristics of my machines, I can easily machine the parts I need. I would be willing to bet that the backlash on the stock screws/nuts on your machines would have a much more pronounced effect than finely scraped gibs and ways. I started my business with an X2 mini mill run manually. The parts I made then are just as good as the parts I make now. Except now with a larger CNC G0704 I can make a lot more a lot faster! Of course, that also means I can make a lot more bad parts faster too!

Although I agree that plate glass is not "terribly flat" you can put a nicer surface on the gibs with sandpaper on glass than stock and be done with it until you address the other areas (if they even need to be addressed). The one thing that lapped gibs will do is significantly improve the "feel" of the machine, the hand wheels will crank more easily and smoothly.

cheers,
Michael
 
I cant tell how flat plate glass is, but I know a whole lotta atv, buggy, and sled owners with heads lapped on plate glass. Including my own buggy which has more then 2x the stock HP.
 
1/2" plate glass is plenty flat. Maybe not up to snuff for NASA but certainly good enough for me.

Steve
 
I had to flatten the sole of a 32" long antique Stanley hand plane. The shops wanted something like $100 to do it (this was back in the 90s) so I bought a sheet of 1/2" plate 8" wide by 48" long for $10 (it was a cutoff from another job) and did it myself in less than an hour. Best darned jointer plane I have! I've got a lot of "miles" on that plate. Once side I simply glue sandpaper to with spray adhesive, the other I reserve for lapping compound. Like I said "Precision is expensive, how much do you want to spend?" :)

cheers,
Michael
 
John Hasler said:
How un-flat was it? The sheets I use are flatter than anything I've got to measure them with (which isn't saying much) and are also flat enough to have considerably improved the ways on my Chinese xy table (which is also not saying much).
Click to expand...

I don't remember exactly, but I can check thickness variations with a tenths indicator. I can probably read up to a half to a third of a tenth using the analog DI. No way to measure warping though, as thin glass (all I have to test) warps. I guess I could see how much it warps over a distance using Airy's points, that would be interesting.
 
I'm not sure I should mention this, but glass is a super-cooled liquid, and never stops flowing.
Lately ground, OK, but beware! .......BLJHB
 
I usually just lurk here, but wanna add 3cents. I have had my LMS3960 mill for a couple of years and ran it ot of the box. So-so. Have the time now, so I thought I would check it out good while cleaning everything. The ways (X,Y,and Z) were horrible! I used blue dye and checked the Y track and for its full length I had "maybe" a total of 1" of surface contact! Counting BOTH sides! Yet it was doing fairly good. Did some research. Valve compound is nowhere near as smooth as mentioned here already. From NAPA to racing forums, it is usually 120 or 280 grit and most now is both mixed! I did use et just to get "some" surfaces to touch. Then 400, 600, 800, 1000 grit to follow. You CAN get things too smooth as said, but unless they are as smooth and flat as gauge blocks, trust me, you will stay lubed unless you are using axle grease! I ran tests with gibs and ways down that 1000 grit and everything from motor oil to way oil still keeps on it. SMOOTH as silk movement! The gibs made the most improvement. White Lithium grease "appeared" to have scraped off, but it was still leaving a nice film. BTW, I have a granite plate (A grade) but for stuff where I might damage it, I got several 12" x 12" marble tiles ($2-5 ea) at Home depot. All of them was withing 5-8 tenths. The ONLY problem is now my 72 yo arms look like Popeyes!
 
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