Machine maintenance is possibly the most overlooked area of a woodworker's business. Yet establishing a routine is not difficult and, once established, most maintenance can be done in a minimal amount of time.
As a manager of a post-secondary woodworking education program that has more than 100 machines and tools from basic portable power tools to sophisticated CNC machinery, and a professional maintenance technician, we have cataloged the machinery and implemented a preventative maintenance program to ensure maintenance is carried out. In the process, we hopefully prevent expensive problems and machine downtime from occurring.
During the coming months, we will share our processes and some sound suggestions that you can use in your shop.
Preventative maintenance for us is summed up in three main principles:
Keep it clean
Keeping machinery clean in a dusty environment sounds like an oxymoron. However, wood dust is a concern because of its effect on our health, its potential as a fire and explosion hazard, and its wear and tear on machinery.
Controlling dust starts with efficient dust collection. Often overlooked, this is no area to skimp. Poor dust collection will cause machine downtime in the long run. However, even the best dust collection system won't pick up all the dust in a shop. Keeping machines clean will then require either brushing off dust, blowing it off with compressed air or sucking it up with a vacuum. The latter is preferred because oftentimes damage is done when fine dust is blown into machine bearings and sliding ways. Vacuuming also minimizes the amount of airborne dust, which is better for our lungs. Brushing may be an acceptable alternative, but brushes can't always get into the hard-to-reach places or under machinery.
While some of us can only dream of having a compressed air source at each machine, care must be taken to never blow dust into sensitive areas that can result in machine damage. This is especially true in electrical cabinets, which should always be vacuumed out. Extreme caution should be taken to avoid the potential of electrocution. Make sure circuits are de-energized by following proper lockout/tagout procedures and keep one hand behind your back when vacuuming to reduce the potential for stray voltage to travel through your body.
In addition to dust, machinery often has a buildup of old grease and lubricants that need to be removed before new lubricants can be added. Removing these will often require the use of solvents. Environmentally friendly products such as citrus-based solvents are effective for most applications. Combined with brushes, lubricants can be removed fairly easily. A good assortment of brush types - nylon, brass and steel - is suggested. Nylon and brass can be used on most surfaces without scratching or excessive damage. Steel should be used with care, but will remove difficult deposits.
Keep it lubricated
Once the machine is cleaned, it can be lubricated. Nowadays most bearings are sealed "for life." When a bearing goes bad, it is simply replaced. A mechanic's stethoscope can be used to diagnose bad bearings. You can use a screwdriver to transmit vibrations to your ear, though the stethoscope works much better. Listen for any clicking noises emanating from the bearing or housing when it is rotated while not under load.
While bearings no longer need to be packed with grease, there are still many moving parts on woodworking machinery that need lubrication. Selecting and using the proper lubricant is essential for maintaining machinery over the long term. Minimizing your inventory of lubricants will save money and create a safer worker environment. We reduced our inventory by cross-referencing lubricants and substituting alternative products. Most manufacturers have cross-reference charts listed online.
Limiting your inventory will also help reduce the detrimental effects of shelf life on products used less frequently and allow you to take advantage of better pricing by purchasing larger quantities of more frequently used products.
Synthetic lubricants have become a viable alternative for many applications, though care must be taken that the seals on older machinery can withstand these lubricants. Although synthetics are more expensive, they have to be changed less frequently, which saves time and money. Whatever the case, be sure to store your lubricants properly, keeping them free of dust and safe from fire. Taking the time to mark the date on the container when you receive them will allow you to monitor their shelf life. Most products are good for at least one year, but many lubricants do break down and lose their effectiveness over time.
One of the greatest challenges with using lubricants in a woodshop is that they are often sticky and tend to attract dust. Teflon-based "dry" lubricants leave a thin film that is less of a dust magnet. However, these lubricants often contain molybdenum disulfide, which, while being a fantastic lubricant, also tends to attract dust. Silicone-based lubricants can cause problems with finishes and should be avoided. Greases are usually super sticky, and care must be taken when pumping grease through Zerk fittings to not also push dust into the system. We always wipe Zerk fittings both before and after greasing a machine.
In our shop, we've invested in plastic caps that cover the fittings to keep them sheltered from dust. The colored caps, available from Grainger, are coded to colored grease guns, making it virtually impossible to inject the wrong grease. Cross-contamination as a result of using different grease types can cause lubricants to congeal and could result in major maintenance headaches. In addition to being colored-coded, our grease guns are also clear, allowing the user to see which grease is inside the gun.
Oftentimes, especially on older machines, adjusting screws are left uncovered. This is a haven for dust. Machines can be retrofitted with bellow covers that protect sensitive areas from dust. Maintenance technicians suggest that covered lubrication areas will often be missed. That's why it's important to have a maintenance task list, something we'll discuss in next month's article.
Keep it calibrated
Assuming your machines are cleaned and properly lubricated, the last task is to make sure they are properly calibrated. Every shop should have a master calibration standard to which all machines are set. In our shop, it's a 3" stainless-steel bar that we use to check our tape measures and calipers to ensure they are reading correctly. Other shops may use a scrap piece of solid surface material. Whatever you use, make sure it's prominently displayed and used by your employees so everyone is on the same page.
In addition to a good caliper, you should have a straight edge, reliable square, dial indicator and set of feeler gauges. This basic tool kit will allow you to inspect most machines to determine arbor runout, surface misalignment and other areas that can keep you from operating at peak performance.
People often ask how often they should check calibration. In a home shop, you may be able to go several months without calibrating. However, in a group setting with multiple users, it must be done frequently.
Next month we will discuss how to implement a preventative maintenance program, including discussing intervals, as well as ideas for creating and maintaining records.
Patrick Molzahn is the cabinetmaking and millwork program director at Madison Area Technical College in Madison, Wis. John Nichols is a senior maintenance manager at Techline USA in Waunakee, Wis.
This article originally appeared in the May 2010 issue.