To lap or not to lap

CODEMAN

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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
 
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.
 
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.
 
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.
 
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.
 
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.
 
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
 
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.
 
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.
 
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.
 
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