Machinist's Minutes: Gibs and Ways

Understanding these is vital to understanding how to address slop in your machines.

[vasudatta]

I thank you for your video input.
I am a machinist and took on a job to kimda clean out the chips and my boss is clearly putting me under a microscope here as he thinks i can't do it.
I have one question though- how do you actually adjust the screws because when I'm doing it the manual feeds tends to get too hard to rotate.
I learned about the existence of tapperd gibs in this video. I had no idea that they're tapperd.i think your right that some gibs, you can't tell if they're trapped

[mr.picklesworth]

Thank you so much for filming horizontally! As a hobbyists I would love to see how you set up to mill a parallelogram. Especially on sowing long and thin like a gib.

[paulhunt]

One misspeak error where he interchanged "gib" and "way".
This video focuses on tapered gibs, but also includes non tapered gibs as illustrated on the Milwaukee mag drill.
Solid ways are still a very viable design option for machine tools and are found on the most expensive CNC machinery as well as manual machinery, but speeds and accuracy requirements for CNC demanded an upgrade. Linear guides became the standard for these applications. The force lubricated ball bearings in linear guide packs allow closer tolerances without friction resistance and wear. Solid ways and gibs must allow some free movement tolerance for oil and to allow the axis travel to move. My experience is that shooting for .0005" side to side movement is the best target when properly adjusting gibs. As he described, machine wear is uneven, and adjustment accuracy is compromised as the wear progresses. Tightening a gib properly in the worn area will lock up axis travel in the less worn area. Machine use will dictate your adjustment options. He said that the salvaged axis had 1/16" wear damage. I cannot imagine a machine running with this much wear for any machine operation, so this must refer something other than tapered gib/way fitment thickness that I thought he was describing.
He did describe the 3 most common adjustment methods. His lathe cross slide uses one adjustment screw with a flanged head fitted to a slot in one end of the tapered gib. The gib is adjusted by tightening or loosening this adjustment screw. The other very common method is the two adjustment screw method with adjustment screws on each end of the tapered gib. Tighten this adjustment by backing off the small end adjustment screw and compensating with equal adjustment tightening of the large tapered gib end adjustment screw. Seat these adjustment screws with only moderate torque. Over torquing will "bow" the tapered gib. I have a Craftsman Atlas lathe with square gibs like he described. This is the only machine tool in my experience that has used square gibs unless you include non precision machines like the Milwaukee mag drill
Machines sometimes don't employ dovetail ways but are true square box ways. This design mandates gibs in multiple directions. The dovetail way design allows the use of only one tapered gib for each axis. Axis and gib wear can be mitigated by proper lubrication and cleaning maintenance. This is why grinding and sanding lathe operations are frowned upon. Abrasive dust significantly accelerates the wear of way and gib surfaces. Way wipers help, but many inexpensive machines don't have wipers and wiper maintenance is commonly under performed. Way surface friction is sometimes addressed by facing the way with with turcite. This sacrificial surface is much softer than cast iron, but with proper maintenance and lubrication can survive in the production environment for many years without appreciable wear. Precision machine tools will be equipped with cast tapered gibs scraped similarly to the ways. This scraping obtains flatness accuracy and provides lubrication oil retention relief. Modern production machinery eliminates the time consuming hand scraping build step with precision way grinding, but automatic forced lubrication is included to ensure that these surfaces ride on an oil film.
He described applications that use short tapered gibs on each end of an axis. I have encountered this design too, but it is far less common in my experience than a tapered gib the length of the moving portion of the axis.

Similar gib technology is sometimes employed to compensate for axis screw/nut fitment and wear. In this application the axis nut is split and the "gib" wedge is forced to load the nut halves against the screw thread shoulder to reduce or eliminate this portion of axis drive backlash.

[robo]

My 1940s southbend lathe has the set screw gib on the crossfeed. Thank you for this video!

[GTSpeedDemon]

I have a bridgeport that has too much wear for the gibb to take all off the slack out with the stock screw adjustment. Is there a method that a DIY type could do to true it up, like filling in the low spot(s) with an epoxy?
Hand scraping appears to cost alot more than what the machine is worth.

[huddleberryfin]

Hey, great little video. Wished I watched it a long time ago when I bought my first machine.

Quick question, I have a cheap Chinese mill with a wonky set of ways. I may try and scrap them in, And the gib already seems like it’s out of travel. Do you see an issue with drilling out the ways to turn a tapered way, into a set screw type?

I just thought of this while watching your video. So I may be missing something obvious. Lol

[robertpearson]

I'm Canadian, metric threads don't bother me (though I prefer imperial)