lapping compound

I had the cross slide and compound on my logan lathe ground but there is some resistance. I was thinking of lapping the slides to reduce the friction. What sort of lapping compound should I use? I have heard of oil stone powder but don't know where to get it. Any ideas?



Reply to
Scott Black
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Machine tool ways are not lapped using compound like that. Don't do it.

You need to find out where the hangup is, and address it in a more careful fashion.

Remove the crossfeed screw and nut, and blue the mating surfaces including the gib, with a large blue sharpie pen. Adjust the gib so it just starts to bind, and see where the interference is. The blue will rub off where there is unwanted point or line contact.

The goal is to have uniform contact on a large area.

Likely sources of trouble:

1) after grinding the axis of the crossfeed screw no longer lines up with the axis of the slide nut. This is expected, and will show up if the entire unit slides freely once the screw is removed. 2) there is line contact at the very tips of the dovetails. If this is the case then the male dovetail can have the sharp edge knocked off or the female dovetail can be relieved at the root by using a small woodruff key cutter to create a square slot at the root. 3) Angles were ground incorrectly, not really likely.


Reply to
jim rozen

At work we use a lapping compound made by Loctite, but I just tried to look it up on their website and it's a bumbling giant. Perhaps an asertive e-mail would get some information....

Anyway, the compound uses silicon carbide abrasive in some type of grease. We use it to lap out holes in hardened tool steel. It works well on soft steels as well.

But are you sure you're correctly addressing your issue? What kind of resistance are you feeling? I've heard of surfaces being too *good* after grinding which causes too much surface contact, and too much resistance. I would assume this would just make for a very *tight* motion. Is this what you're experiencing? If so, lapping may make the situation worse...



Reply to
Robin S.

A lot of people use Clover brand lapping compound (valve grinding compound) which comes in a number of "grits". It is available from MSC, J&L, and most of the catalog supply houses. It is probably not a good idea to try it until you determine where the friction is and if the friction is excessive. Suggest you check with Scott Logan at Logan Actuator Company.

Bob Swinney

Reply to
Robert Swinney

Lapping compound is nothing more than a thick oil containing some abrasive grit. Go to

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and they will have various grades of Silicon Carbide (SiC) and Aluminum Oxide (AlO2) that will be quite useful for making your own lapping compound. You should be able to use something like the 9 micron grit to get a nice smooth finish on the ways and you will definitely find the high spots that way and be able to scrape them down You will probably like to use some lightweight (10 weight or so) oil for grit that fine. When you are done with the grit, make sure that you clean it ALL from the surfaces otherwise the grit will continue to do it's work.

-- Why isn't there an Ozone Hole at the NORTH Pole?

Reply to
Bob May

Pay strict attention to what Jim said! Don't use lapping compound on your lathe regardless of what you discover is the problem. Remember, cast iron, because it's soft and is relatively porous, becomes highly charged with abrasive and will be difficult to clean when you think you've lapped enough. That's why the scrape cast iron instead of lap it. You'd end up with as much damage as you had before grinding if you couldn't eliminate the abrasive, and that could prove quite challenging.


Reply to
Harold Vordos

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