Last month we started discussing Cleaning Solutions for the Machine Shop with a quick overview of detergents. This month we’re finishing up our look at cleaning solutions with an overview of glass beads, tumbler media and shot.
The Whys and Why Nots of Cleaning with Glass Beads
One of the most widely used cleaning media is the glass bead. Glass beads are primarily used to blast engine components free of carbon base soils and oxidation. Blasting is done in a cabinet to contain and recycle the media being used.
The cleaning process is done with beads being siphoned from a storage area, through a hand held gun that accelerates the media with air pressure. The removed material and broken beads are passed through an exhaust system into a filter that can be cleaned manually.
Tips for faster glass beading
Keep your air pressure at 60PSI or below.
If you set operating air pressure in excess of 60 to 65 PSI, glass beads will shatter upon contact with the part being blasted. A shattered bead will be removed to the filter, just like the materials that have been removed from your blasted component. This is the largest WASTE of beads, and beads equal money.
Blasting a part that is wet with oil or water will take more time than blasting a dry part. Always remove as much wet soil and grime as possible BEFORE starting the glass beader. Bead blasting parts is labor intensive enough, why prolong the time involved?
Remove all glass beading residue before proceeding.
Remember to clean parts after glass beading, using warm soapy water, followed by a clear water rinse. Parts solvent does not cut it. If bolt holes, water jackets, and oil galleys are involved, they too must be cleaned carefully. Be sure any orifices are clear of glass beads; you wouldn’t want a tiny glass bead compromising your engine build, now would you?
Parts cleaning with an Airless Blaster is less labor intensive than glass beading and is generally used following thermal cleaning. In other words, once you’ve “cooked” the parts in a thermal oven, you use blast media to remove the carbonized materials left over.
Select the correct media for the job
Goodson stocks three cleaning media or shot for different applications. The first is Steel Shot, used primarily for removing materials from cast iron or steel. Used in a conservative manner, is effective in removing baked carbon and rust. But remember, leaving parts in a blaster too long will compromise machined surfaces, including deck and bearing mounting bores. One big drawback to steel shot is that it will rust and leave a dark red finish on parts.
Stainless steel shot is also available, in conditioned and cut wire. This material is used primarily for aluminum parts. The stainless shot won’t rust like steel shot so it doesn’t leave the reddish finish on cleaned parts. It removes soil and oxidation and produces a like-new aluminum appearance.
Conditioned Stainless is simply shot that has been blasted into a hardened steel plate, leaving a spherical or ball shaped abrasive. Again short blast times are recommended to minimize distortion and surface damage to machined areas. Dry parts are an absolute necessity to maximize cleaning while minimizing labor time.
Cut Wire Stainless is used to clean the worst oxidized aluminum materials. This media is very aggressive and used exclusively before a complete reman or repair including TIG welding (tungsten inert gas). All machined surfaces will require re-machining.
Just as with glass bead cleaning, these media require a complete soap and water scrub down before continuing the build. The cleaning abrasives can be trapped in oil galleys, water jackets, and bolt holes. Be very careful!
The parts tumbler does a good job of cleaning smaller components. Some advantages of parts tumbling are:
- Low maintenance
- Time to clean is short
- Can be used on a wide variety of shapes and material with the correct media.
As with glass beading and the airless blaster, care must be used to avoid damaging machined surfaces.
Parts Tumbling in the Auto Machine Shop
The most common usage of the tumbler in the auto shop is in cleaning valve train parts and smaller engine fasteners. When cleaning these parts, such as valves, you need media that has weight to it. Since you’re looking to abrade larger quantities of baked on carbon you would use Steel Diagonals. (Order No. PTM-20D). As the valves are tumbled, they are bombarded by the heavier media, removing the deposits. In this instance valve stem protection (VSP-16) must be used to prevent damage to polished stems.
Irregularly shaped parts such as valve springs, retainers, etc. clean well with Steel Ballcones (PTM-20BC) These are a lighter weight and clean without damaging valve springs and retainers.
Ceramic Diagonals (PTM-20CR) are our lightest media and used on soft materials such as brass and aluminum. Ceramic Diagonals work well with alternator and distributor housings.
We recommend you use Parts Tumbler Solution (PT-SOL) with all of these media. This solution softens deposits for easier removal and combines with removed deposits to carrying them to the sump area of the tumbler, releasing them there.
As always, if you have any other questions about parts cleaning, give the Goodson Techxperts™ a call at 1-800-533-8010 or visit the Goodson Tech Library online.