Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Scott Black
 
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Default 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?

thanks

sb


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jim rozen
 
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In article , Scott Black says...

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?


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.

Jim


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Robin S.
 
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"Scott Black" sblackatprogression.net wrote in message
...
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?


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...

Regards,

Robin


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Robert Swinney
 
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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


"Scott Black" sblackatprogression.net wrote in message
...
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?

thanks

sb



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Bob May
 
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Lapping compound is nothing more than a thick oil containing some abrasive
grit. Go to www.gotgrit.com 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?




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Harold Vordos
 
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"Scott Black" sblackatprogression.net wrote in message
...
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?

thanks

sb

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.

Harold


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