All-Time High for Steel

In a February post I explained the origins of the steel scrap surcharge. Basically, the base price of steel shot and steel grit is fixed but a surcharge is added (and changed each month) to bring the price of steel to current market value.

Well, the demand for steel in both Asia and Eastern Europe continues to grow and much of the scrap is being sent overseas to satisfy this demand. Obviously, increasing demand leads to increased pricing and even product shortages.

The current scrap surcharge is up about 500% in the past 5 years and has nearly doubled in the past six months. In addition, the lead times are continuing to extend for certain sizes and grades. Unfortunately, it does not look like this is going to be a short term problem unless steel manufacturers can figure out a way to make a lot more steel.

We're at an all-time high for steel prices but I fear we will continue to say the same thing many times in the near future.

Matching Nozzle Size and Grit Size

Question: I would like to know if there is a standard for matching Nozzle opening size to media size. I am just starting out and I am not sure what size media I can use with my sand blaster. The literature on the blaster doesn't say. Can you help?

Response: Generally, the nozzle size you use should be at least 3-4 times the diameter of the grit size.

{If the grit is still getting stuck in the nozzle, try reducing the blasting pressure (psi) and making sure there is no moisture in the system.}

Mass Finishing Basics (Part 4)

The art of mass finishing really shows itself when trying to select a tumbling media. Media is the material ('stones') that parts are tumbled with in either a vibe or barrel tumbler. The types of media available are as varied as the parts that can be tumbled in a mass finishing process.

Ceramic Media is available in bonds or formulations that range from super aggressive, cutting to non-abrasive polishing. The most popular preformed shapes are triangles, cylinders and variations of these shapes. Ceramic media is typically used with hard metals such as steel. Softer metals such as aluminum can be tumbled with ceramic media but care should be taken so the process is not too aggressive. Precision Media is a high density version for specialty applications.

Plastic Media and Synthetic Media have a lower density and are thus less aggressive than ceramic media. These media are typically used with aluminum, copper, brass and other soft metals. Popular preformed shapes include cones, pyramids and wedges.

Steel Media is used primarily for polishing and burnishing operations in barrel tumblers. Some vibes can be set-up to handle the weight of the steel media which is 3-5 times as heavy as the other preformed shapes.

Other types of tumbling media include Hardwood Media (dry tumbling of wood and some plastic parts), Aluminum Oxide (surface finishing and etching), Walnut Shell (burnishing) and Corn Cob (burnishing) as well as many other specialty media.

Choosing the proper type, size, shape and bond is critical to making sure that the required finishing is achieved. Common problems include excessive media wear, poor and/or inconsistent surface finish, too much (or too little) edge rounding and media 'jamming'.

Wood Stripping

Question: I’m renovating a house built in 1917 and I would like to remove the years of built up paint off the 6 panel doors and trim that was used in the house. There are 15 doors and probably a 1000 lineal feet of various finish boards. Which Machine and Media should I purchase? Approximately how much media will I need?

Response: Either the KF110DM or the KF65DM will work with the Corn Cob Grit or Walnut Shell Grit. The Walnut Shell Grit will offer a more aggressive stripping action but the surface may require some sanding depending on the surface finish you require. Corn Cob Grit will be more ‘sensitive’ to the wood surface but will not strip as quickly.

The quantity of media required will depend on how aggressive the blasting that is required. Multiple layers of durable paint will demand more media; however, both Corn Cob and Walnut Shell are re-usable. If you are blasting in a clean area you can pick up the media and re-blast it a few times – just be careful to not pick up anything that could be blasted and damage the wood surface.

Motorcyle Parts

Question: I want to clean /polish an aluminum motorcycle engine. Would walnut shell be the best media for the job? I want a clean, lightly polished look typical of stock bikes.

Response: Walnut Shell Grit will clean the surfaces relatively well but will not have an impact on the surface finish. A Medium-Fine or Fine Glass Bead will clean the metal and leave a satin-like finish on the surface.