Re: RE: [CAD_CAM_EDM_DRO] Re:Lapping

Hey Guys. I'm completely ignorant about this lapping and scrapping stuff. Although I believe I understand the methods and pitfalls of lapping (did a few telescope mirrors many years ago) could someone explain what hand scraping is.

I have heard the term many times and it's obviously a good thing to have hand scrapped ways on your machine. How is it done?

Thanks

Ted

----- Original Message -----
From: Roger Hampson
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Thursday, March 24, 2005 3:34 PM
Subject: [Norton AntiSpam] RE: [CAD_CAM_EDM_DRO] Re:Lapping





Bruce

Excellent answer !!!

Roger

-----Original Message-----
From: Bruce Pigeon [mailto:bwpigeon@...]
Sent: 24 March 2005 20:29
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re:Lapping



IMHO lapping in this case is trying to make a silk purse out of a pigs ear.

All of your aruguements have their merits and their places. I have seen
many gunsmiths use many different processes to rework or so called
repair a gun. Not all of these methods would be deemed acceptable.
So does that make lapping the correct way to repair this machine? I don't
think so. I have hand scraped more cast iron in my life than I want to
think
about, never have I tried to lap a pair if ways to correct them, it won't
work.
I also have lapped many things that should not be scraped. Learning and
knowing when and where to use each method is important. If you don't have
a mentor to to ask and help you, you are left to other means like these
forums.
If your hear all of the arguements and pick the wrong solution, you will
learn
the hard way. Your best tool is good judgement and common sense in
selecting
the right process. Don't look for a short cut. Choose wisely Grasshopper.

Just my opinion.

Bruce

-------Original Message-------

From: CAD_CAM_EDM_DRO@yahoogroups.com
Date: 03/24/05 13:12:16
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re:Lapping



Andy Wander <awander@...> wrote:

If lapping can only be done with a lap, and using lapping compound on 2
mating surfaces to smooth them up NEVER makes things better, why do custom
gunsmiths working on tightening up the slide-to-frame fit on auto pistols
use this technique?

Ron, I think you're being a little TOO adamant on this point.

/// Or TOO realistic. Comparing the alloys and toolsteels gunmakers use to
chinese cast iron, there isn't much comparison. Marcus is exactly right, to
do this without a means of verifying the concerns to begin with and means of
monitoring the progress and end result is a gamble at best. Would be
virtually impossible to maintain the precision of the machine. The problem
exists with the cast iron itself and the method in which it was finished.
Cast iron and steel as you know have hard and soft spots. The soft areas are
going to be abraded away by the compound at a much faster rate. Now the
machined finish: To lap these two surfaces with one another and any degree
of accuracy and not have a method of verifying. one must ascertain that the
machine finish is constant throughout the entire surface meaning the same
number of peaks and valleys of machine tool marks. An area of less surface
density will wear away faster as well. When surface grinding a surface after
machining will demonstrate
this especially in the case of a fly cutter that tends to crown the
surface.

And all of this when re-assembled must maintain 90 degress from the X and Y
plane to the centerline of the spindle (many of these machines have no means
of adjusting the tram). Then the bottom of the saddle must be parallel to
the top. The X and Y centerlines must be 90 degrees to one another. dovetail
to dovetail parallel etc. etc. Alot of things to keep track of and check
along the way.

Just my opinion, If it was TOO adamant, I apologize,

Ron

/////





Andy Wander
Verrex Corporation

-----Original Message-----
From: Tom Hubin [mailto:thubin@...]
Sent: Thursday, March 24, 2005 9:07 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re:Lapping


> In fact,
> telescope makers make their mirrors by grinding two surfaces together to
> make them curved.

And alternating two of three surfaces to grind all three flat.

Tom Hubin
thubin@...



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