We recently received a customer request about shim safety. An employee at the customer site had experienced a “near miss” safety issue due to walking too closely to a machine, and getting their clothes caught against a shim. Since I have a scar on my right thumb caused by a 3 mil shim, I thought a discussion on shim safety might be in order!
Shims do three things:
- Change the elevation of the moveable machine.
- Compensate for soft foot.
- Provide a smooth, flat surface for the machine feet.
As such, they must be used in the alignment process. But proper safety considerations for shims should be used as well.
TYPES OF SHIMS
There are basically three types of shims:
-Pre-cut, stainless steel shims. These types of shims are the most commonly used. They come in many different sizes, or can be custom-ordered. These shims have a safety tab, to help in installation and removal. They are typically free from burrs, but can have a sharp edge. And very thin ones – less than 5 mils, can cut, especially if they extend out from the machine (as in the image above).
-Rolled Shim Stock. Once common, rolled shim stock is not commonly used in most facilities. Each shim had to be laid out, cut with snips, and de-burred. For the sake of time, these shims were often cut in haste. It is strongly recommended to use cut shim stock only as a last resort. It is time-consuming, inaccurate (if not measured, and de-burred), and if time is considered, it is more expensive than pre-cut shims.
-Plastic, or soft shims. These shims are most often used to compensate for irregularities in the machine base of feet, and to minimize the negative effects of soft foot. Since they are somewhat elastic, they are best used in conjunction with stainless pre-cut shims.
SAFE HANDLING PRACTICES
As with any thin-cut steel, shims should be handled with gloves whenever possible. The tabs on pre-cut shims serve as a “handle” to install or remove shims from under a motor. Removing shims is best done with needle nose pliers, or a shim removal tool (or hook), if your shim provider has these. If shims or shim stock must be cut, it should be cut with the correct type of snips, de-burred, and made safe for use. If it doubt, please contact your safety department for specific applications in your facility.
SHIM PLACEMENT ALTERNATIVES
If shims will be placed so that the tabs are exposed, and a chance for bumping against the shims exists, other placement configurations should be considered.
One is to install the shims with the tabs in-line with the shafts, so the tab does not protrude outward into traffic or exposure areas.
Another method to minimize cut exposure is, once the alignment is completed, the shim tabs could be covered with a liquid plastic costing, such as those products developed for coating tool handles.
Shims are essential for proper alignment, but shims should always be considered sharp, and proper placement and handling techniques will help to minimize accident risks.