Planning on glueing 1/4 or 3/8 inch strips to bottom of sides on existing drawers for'm to slide on when opened. Will be sliding on 3/4 ply, drawers aint opened maybe one er twice a month. Aint nothing to fasten metal side slides to. They won't be slide out to far. Strips glued to 3/4 to guide'm back to their home position. TALK TO ME!!!
Some drawers are fabricated with very thin sides and a shoe or slip is added to the bottom edge to spread the load and decrease the wear. Don't know where they originated or what country they were popular in, but maybe somebody will chime in.
If you have 1/2" sides you have plenty of thickness for ball bearing runners. Worked my way through school building kitchen cabinets and installed hundreds of drawers. The drawer boxes were glued and stapled and in all the years since have only heard of one or two failures.
If you want to use slips my understanding is you should use very hard wood in the cabinet and softer wood on the drawer. There is something about the difference in species reducing friction and it moves the wear to the drawer where it will be easier to repair if it's ever necessary. I bet thee is a chart somewhere that list the friction if we could find it.
I have used slips on furniture drawer sides, because I used 3/8” sides for easy dovetails. The hardwood slip was glued to the drawer sides, providing a good runner. The slip has the groove for the drawer bottom. The slip could be the same wood as the cabinet. I like the looks of the slip.
I just went a looked at Amazon and there are many many brands and types. I used side mounted one from both Blum and Knape & Vogt. Have not used the under mounted ones.
Some of them are about 3/4 extension and some a re full extension. Some are soft close.
They have various weight ratings. My advice is to get ones that are over rated. If you think you are going to put fifty pounds of stuff in the drawer get ones rated for a hundred pounds.
As far as the ball bearings go, many of them have ball bearings in the wheels and others have linear races filled with bearings.
Follow the instructions carefully. Some of them say Set the spacing allowing +1/32" minus 0.
In a work shop you may have to blow the dust and crud out occasionally.