Machine Gib Inspection video

Hey guys, just wanted to share this here and also let Richard see. I published a new video on my Youtube channel showing and talking about machine gib inspections and using an indicator to help determine how much play you have in them.
Some of this info I picked up from Richard at the Georgia scraping class, and since then I've had a few viewers ask me about the subject, so I figured lets make a video.

I'm no master at this either, just showing what I know and understand, and still have lots to learn. Hope the video helps some people out.



Checking Gibs For Wear & Needed Adjustments - YouTube

I'm just glad to see you hanging out here, what with how busy you are on you tube. Greg.

It looks good for the most part. On the 2nd test I hope when you set the indicator on the knee top you rested the indicator on the saddle and not on the table to check the play in the saddle gib. If you put it on the table and pushed it you would be checking both saddle and table gib. When scraping the gibs you test both ends of the gib to get the same gap on top and bottom using this method. But as Adam says, rest the indicator as close to the ways at the edge so you don't multiply the error. Also on worn machines , you may have to set it more then a .001" because they are worn low in the middle and when moved it will bind on unworn ends.

So on saddle gib test, set mag on knee and indicator ot saddle, then mag on saddle and indicator on table to check table gib.

I will put that on you tube later too,but I have to scoot now. Rich

Yeah, you need to be sure your set up allows you to test one axis at a time and not two as in the second test.

Also I was always taught to use the power feed instead of pulling on the table. It's ok on the small stuff but best of luck pulling on an 8 ton Hor bore table. Set a slowish feed running in one direction and then reverse the feed and see what happens to the DTI. Never adjust up beyond 0.001" of movement, bigger machines may need slightly more.

Regards Tyrone.

I have heard of people doing it like the 3 plate method, but I have never done that. A huge waste of time and effort. If you want to do it, go ahead. I test squareness with a mag. square, granite square, blade square or CMM.

Zertwiz said:

Richard is it possible to generate a 90 degree Guage buy scraping angel plates using only a surface plate as a reference. And no dial indicators.

Click to expand...

Why no indicators? Even the most casual hobbyist need one.

Yes, its possible to scrape three angle plates using Averaging of Errors technique but it's a lot of tedious work. If you wish to pursue this, you may wish to start small and cheap with import angle plates from ebay:

3 X 3 X 3 INCH GROUND ANGLE PLATE WEBBED END (342-153) | eBay

Get three angle plates for your scraping experiment but you might wish to select a design applicable for your later use.

There's a saying in racing circles: ' You cant beat cubic money." Unless you have access to cheap starting materials my suggestion would be to save time, labor, and cost by searching out a granite square suited to your use. Keeping a watchful eye on on-line auction and want-ad resources would be my first choice. Or buy new: Shars has a line of granite tooling that's almost affordable. For example:

1" x 6" x 1" Precision Granite Square.

If you are concerned with an unknown square's accuracy, remember squareness testing is one of the simplest procedures in open shop metrology (the reversal method) requiring only the test object, a surface plate, a surface gage some parallels and a means of clamping the parallels to the test object. You don't even need a reference square. First determine the beam and stock are straight and parallel. Then by using the reversal technique, you can refine your readings to the limits of your DTI's resolution. There's a group of images demonstrating this somewhere.

A square's reference angle does not have to be exactly 90 degrees to be usable. If you know the square's error you can compensate the reading to attain any accuracy desired.

I frequently used a 4 ft hard square when I was in heavy layout back when I was working in m career shop. It was a well made tool but it had been abused and was off by seven thou or so acute in 4 feet. Lay on a strip of masking tape on the side of the beam, mark off tics and numbers for the error and compensation is easy: Bump, check with a feeler, calculate the correction, note the reading. Jim Parr taught me that trick about 1972 Great machinist long gone to his reward. Hope there's plenty of home-brew beer wherever he is.