What to do with an edge finder that gives goofy reading?

[gary350]

My 32 year old Starrett edge finder has always worked perfect but to day it is giving me all kinds of goofy readings. I cranked the mill table over to find zero then set the dial setting to zero, the table locks are snug. Then I cranked back then forward to check zero again and the edge finder gives me a reading of minus +.003" on the dial. I reset the dial tried again this time I get a reading of +.005". Whats up with this? Try again I get -.002". Try again I get -.005". Try again I get +.001". Try again I get -.002".

Removed the edge finder from the mill and inspected it. It looks fine but trying to slide the tip with my finger it does not slide easy.

I put oil in it that did not work. I tried different types of lube none of them keep it from sticking. I tested it in the mill and I still get all sorts of goofy reading from +.003" to -.005" either side of zero.

I never had this problem before whats up with this???

[RWO]

Is the mill's drawbar tight?

RWO

[uncle pete]

I don't know about the exact materials used inside those edge finders but I'd say your problem is old and improper oils gumming up the works. If the internals are all metal then maybe a good long soak in some acetone or other more user friendly chemicals would remove the old lube then re oil with a non drying type oil. I'd guess Starretts instrument oil is designed for exactly this type of lubrication. Then again you could swap it for one of those digital edge finders that are made in Germany, About $800 and no oil required. A 5 buck container of the proper Starrett oil seems more cost effective tho.

Pete

[beanbag]

I think the smoother the two parts slide against each other, the better the edge finder works. You may have to take it apart and clean and possibly polish it.

[smalltime]

Demag the edge finder and the workpiece.

If this fails, buy a new edge finder. (And don't spend anywhere near $800.00 for it )

JMO

[gary350]

I got to thinking how old oil gets gummy and the edge finder has never been cleaned so I got it running in the mill off center against a metal part then I sprayed it with carburetor cleaner. It only took a few seconds I could tell a difference. I blew it off with the air hose then put a drop of good oil on the edge finder. Now it works excellent.

[MichaelP]

Now tell us what you're going to spend the unused $800 on.

[Arthur.Marks]

Maybe a stupid question---what exactly is an "edge finder" in this instance? I was expecting your title to refer to a standard twenty buck "jump" edgefinder, but you're talking indicator dial readings. Is this a dial test indicator? Some sort of 3D edgefinder? Something else?

[uncle pete]

Art,
If your talking about what I posted about those $800 edge finders. There's a probe that is calibrated for size so that the digital edge finder reads to zero once the exact spindle C/L is reached. Plus you need to zero the edge finder in the tool holder it's permanently fixed in. That's a one time thing unless you change tool holders.Those edge finders are used with the spindle stopped. How the internals work makes me scratch my head. Try Googling 3-D taster. They make both analog and digital versions. I was curious enough to email the factory to see if they had a exploded view of the internal workings. They never emailed me back. I'd still like to know exactly how they work.

Pete

[gary350]

Maybe a stupid question---what exactly is an "edge finder" in this instance? I was expecting your title to refer to a standard twenty buck "jump" edgefinder, but you're talking indicator dial readings. Is this a dial test indicator? Some sort of 3D edgefinder? Something else?

Here is a pic of an edge finder on ebay.
http://cgi.ebay.com/Fisher-Micro-Edg...item2eb1c8292e

The dial I am talking about is the milling machine table. The hand crank dial goes 0 to .200" full turn on the table.

[Forrest Addy]

Here's a video from TubalCain on edge finding:

http://www.youtube.com/watch?v=CXMl7KyH8yc

I strongly encourage the noobs and neophytes to look for TubalCain's excellent videos of the basic machine shop tutorials. His explanations are simple and to the point, easly undertood and being on YouTube is readily available. About all you need is "TubalCain" for a search object if you have time to browse, otherwise include the topic.