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To lap or not to lap

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CODEMAN

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#1
I thought I would start a separate thread about this. I now have an HF lathe and mini Mill. Many say the very first thing to do is lap the gibs and dovetails. Others say that the grit can stay in the iron and over time grind it away. Others say that washing the water soluble Permatex valve grinding medium off the part then bathing in oil is the way to go.

I thought I would use 1000 grit wet and dry paper first on a aluminum flat plate, then finish with the Permatex.

What think you?

Steve
 

JimDawson

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#2
What problem are you trying to solve? Is the table hard to move? Sticky? I would be concerned about getting all of the lapping compound out of the system. Hot, soapy water might work. I would also suggest that the valve lapping compound is courser than 1000 grit.

If it were me I would use the machine for awhile and then take it apart and look for wear spots, or shiney spots on the gibs and ways. But if the machine will adjust OK, I wouldn't do anything except use it.
 

Cobra

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#3
As my Dad was want to say - "No good will come of this"
I wonder what problem you are trying to solve with the lapping compound?
You will be forever trying to get the stuff out of the parts.
 

tertiaryjim

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#4
I can't imagine any aluminum plate will be even close to flat.
If nothing else the small china surface plates are cheap and in the ballpark.
Wait for the 20% off and free shipping from Enco.
You'll then have something to use to check parts n such.
It's the perfect time to make a scraper or two and learn a bit about that and you can do a far better job of it, even as a beginner, than lapping will do.
For $30-$50 and some machine work you can have the tools to make your machines better and learn a useful skill.
First though, you've got to blue check the parts to see what needs to be done.
It's always fun to learn.
 

DMS

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#5
I scraped in my saddle and tailstock on the 7x14 lathe I started with. It made a huge difference. Initial contact on between the saddle and the ways was on 3 points no more than 1/4" diameter. That being said, it wasn't a quick process. I have heard of others lapping their ways. Some came out ahead, some came out behind. If you want to see how bad things are, it is fairly cheep to check the contact surfaces. Purchase some bearing blue (enco carries it). Pull off your carriage/mill table, and apply a (very) thin coat of glue to one side, then place the other side back in place with the gibs loose or removed. Apply mild, even, pressure and slide the part back and forth about 1/2" inch about 3 times. Then remove the table/carraige again and look at the two surfaces. On the part that was clean initially, there will be blue spots where it was contacting the mating side. On the part that was blued going in, the blue will be gone, or lighter than the surrounding area. The ideal case is for even spots of blue across the whole surface. If you only see blue in a couple places... well, lapping or scraping may help you. If you decide to lap, proceed with caution. If it were me, I would use the silicon carbide paper rather than the clover paste. Go slow, and measure often.

A lot of people (when starting out) think that ways should be mirror flat and shiny, but that is not the case. It's actually the opposite of what you want. If the mating surfaces are too flat they squeeze out all the lubricant, and then you have dry contact between the two, which leads to premature wear. This is why scraping is still the preferred method for machines. Some manufactures try to get away with a middle ground (hahah), so they grind the ways, and then "flake" them. This produces small, irregular surface imperfections that act a lot like a fully scraped surface.

That was a bit more long winded than I had intended... but there you go.
 

chuckorlando

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#6
Lapping is to make something real flat. Slip stick will be a problem if you make it to flat. As suggested I would try some scraping if anything. But I would use the machine a while before I tried anything at all.
 
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Andre

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#7
Well first off, how flat is that aluminum plate of yours? Run of the mill aluminum plate is not that flat. Get a cheap granite plate.

Valve grinding compound is around 400-600 grit. Way too coarse for lapping. There is a product called "Timesaver". It is a lapping compound that turns into an inert, non abrasive compound in a day or two. Used in gearboxes, throw some in the oil, let it lap away, and it will dissolve so no major cleaning is required.

http://www.mini-lathe.com/Lapping/mt_lap.htm

http://www.newmantools.com/lapping/time.htm
 

kd4gij

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#8
Andre beat me to it. All of the sites deadicated to the mini lathe and mill. Recomend lapping the ways. Tiag lathe eather comes in kit form with instruction on laping the ways or factory laped ready to run. But yes valve laping compound is to corse. and aluminum plate won't be flat enough. Plate glass works fine though.
 

John Hasler

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#9
Andre beat me to it. All of the sites deadicated to the mini lathe and mill. Recomend lapping the ways. Tiag lathe eather comes in kit form with instruction on laping the ways or factory laped ready to run. But yes valve laping compound is to corse. and aluminum plate won't be flat enough. Plate glass works fine though.
Plate glass is flexible (unless you have a chunk of the inch thick kind). It helps to stack up several sheets and put the stack on something at least fairly flat such as a tablesaw table.
 
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Andre

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#10
Andre beat me to it. All of the sites deadicated to the mini lathe and mill. Recomend lapping the ways. Tiag lathe eather comes in kit form with instruction on laping the ways or factory laped ready to run. But yes valve laping compound is to corse. and aluminum plate won't be flat enough. Plate glass works fine though.
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.

I wish you the best, but you can very easily RUIN your ways by doing this.
 

CODEMAN

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#11
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
 

tertiaryjim

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#12
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.
 

John Hasler

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#13
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.
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).
 

mhackney

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#14
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
 

chuckorlando

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#15
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.
 

CODEMAN

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#16
1/2" plate glass is plenty flat. Maybe not up to snuff for NASA but certainly good enough for me.

Steve
 

mhackney

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#17
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
 
A

Andre

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#18
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).
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.
 

The Liberal Arts Garage

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#19
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
 

pandreasen

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#20
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!
 

T Bredehoft

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#21
glass is a super-cooled liquid, and never stops flowing.
True to a point. for all practical purposes, glass is a solid below 900ºf. Window glass that is thicker at the bottom of the window was put that way on purpose, it didn't 'creep.' Anything else is old wives' tales.
 
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