Re: [CAD_CAM_EDM_DRO] Re: Improving accuracy on mini-mill? (lapping?)

Hi,

One thing that is often neglected with gib strips is that if they are not
pinned as opposed to the usual method of locating with a detent for the
adjusting screws. If you stop the end float and then scrap the gig to the
way there should be no movement and very little friction. Look at the way
really high quality lathes and milling machines are contructed.

The fastest way to right-off your machine would be to lap it because you
will be lapping against a bad surface already and not a purpose made lap.
Scrap off the high spots and leave somewhere for oil to sit and protect your
machine from yourself :-)

Regards,

Terry

>
> Hey,
> All you will do is smooth everything out, and probably make worse
> the convex/concave condition of the mating slides. A surface with a
> small texture to it is a good thing as each pit holds oil for
> lubrication.
>
> The problem is that your X axis topslide is probably convex, so
> that each end is up and only the middle is touching the base Y axis
> slide. What you want are two mating flat surfaces. Then with light
> gib pressure the table will be secure and won't rock. Of course this
> also assumes the dovetails are square and parallel to eachother,
> which they won't be.
>
> Through careful inspection on a surface plate or other very flat
> surface and your test indicator, you should be able to detect the
> high/low spots. Bring the high spots down until the ways are
> parallel with the face of the milling table. Do the same for the
> base slide ways.
>
> Better yet, you could buy some linear slides and build your own
> X/Y axis using your existing CNC mill. Then you could use your mill
> to rebuild your Z axis so that it is much beefier.
>
> Best yet, use your mini-mill as is, have fun with it and save your
> time/money/efforts for another, bigger/better machine.
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Abby Katt" <cnc@a...> wrote:
> > Roger,
> >
> > But I wasn't really thinking of using say.. 60 grit..
> >
> > I was thinking more of using something fine (ie 600 to 1200 grit),
> to smooth
> > out the bearing surface and gibs, so that I could reduce friction,
> allowing
> > me to tighten them more and gain better rigitity. If I used a small
> enough
> > grit size, wouldn't it just remove the current irregyularities from
> the
> > surface and even it out more, so that they still more or less
> defined the
> > same plane, but moved with less friction?
> >
> > I've heard of a few people using lapping.. Does anyone else have any
> > experience here?
> > A worthy-try, or a just plain bad idea?
> >
> > Thanks!
> > Abby
> >
> >
> >
> >
> > -----Original Message-----
> > From: Roger Hampson [mailto:r_.hampson@t...]
> > Sent: 22 March 2005 20:38
> > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > Subject: RE: [CAD_CAM_EDM_DRO] Improving accuracy on mini-mill?
> (lapping?)
> >
> >
> >
> > As far as I can see two things will happen.
> > 1 the application of abrasive compound will size the machine slide
> ways
> >
> > And
> >
> > 2 ruin what would otherwise be a usable machine
> >
> > problem is that you have no method of lapping just the point you
> need to, to
> > bring back accuracy
> >
> > Roger
> >
> > -----Original Message-----
> > From: Abby Katt [mailto:cnc@a...]
> > Sent: 22 March 2005 20:30
> > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > Subject: [CAD_CAM_EDM_DRO] Improving accuracy on mini-mill?
> (lapping?)
> >
> >
> >
> > Hmmm..
> >
> > I noticed that if I stick a DTI of my asian mini-mill so it's
> probing offset
> > to the middle of the table table/vs the column and then press on
> the table
> > at the extents, I can see the DTI needle move quite a lot! Aaah!
> Now, since
> > the cutting head is usually in the middle of the table, I guess
> that the
> > effect here is not so much, but still...
> >
> > So this makes me tighten up all the gibs, but the problem is that
> when I do
> > this, it makes it much harder to move the table (or impossible).
> This leads
> > me to ponder using some sort of lapping compound on the ways, and
> then
> > programming the mill to go back and forwards a few hundred times,
> to smooth
> > up the ways/gibmetal, so that I can then tighten the gibs more to
> get a more
> > rigid setup with less friction.
> >
> > Is it a good idea?
> > What sort of lapping jive should I be using? Brasso? Valve grind
> compound?
> > 1200grit? 600? Peanut butter and toast? :)
> >
> > Is the lazy CNC way of having the mill do the work a good idea, or
> > bad-science? Will it just make more sense to do it all by hand with
> the old
> > emery-cloth?
> >
> > Thanks guys!
> > Abby
> >
> >
> >
> >
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[Moderators]

> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:

aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.

> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a

sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.

>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.

DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........

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