Brake Lathe Care and Feeding: Breaking the Cycle of Neglect When it Comes to Machining Rotors – UnderhoodService

Brake Lathe Care and Feeding: Breaking the Cycle of Neglect When it Comes to Machining Rotors

How often do you use your brake lathe? Once a month? Once a week? Once a day? If you’re like most undercar shops, your brake lathe is humming along for at least several hours per day, every day. Even a one-man shop will find a brake lathe to be an indispensable piece of undercar equipment.

How often does your lathe let you down? Chances are, rarely. The point is, quality brake lathes routinely give years, even decades of accurate, trouble-free service. Of course, proper maintenance of your brake lathe, just like scheduled vehicle maintenance, will extend the life of your equipment. Furthermore, a well-maintained lathe will ensure an accurate cut and the correct surface finish on each rotor that you machine.

No one wants a comeback, particularly when a brake noise or vibration could have been prevented in the first place with a correctly finished rotor.

What is brake lathe maintenance? Just as we diplomatically point out to our customers that the maintenance requirements are in the back of the vehicle owner’s manual, you might try looking in your lathe operator’s manual for recommended service procedures. You know, that booklet that came with the lathe when you bought it? Yeah, the one that you probably haven’t seen since you opened the crate that the lathe came in. The same one that you most likely couldn’t find today even if you had a winning lottery ticket hidden inside of it!

OK, I confess. I couldn’t find mine either when I recently needed to order a new lamp assembly for our lathe. Fortunately, the lathe manufacturer is well aware of people like me, and I was able to download a copy of the operator’s manual (and an exploded parts diagram) from their website.

Brake lathes are subjected to metal chips, rust, brake dust and dirt. The most important maintenance is frequent inspection and cleaning. Metal chips and dust should be cleaned from the lathe daily. If they are allowed to accumulate, they can pack down and harden, particularly in a humid environment. This will make them more difficult to remove.

Cleaning should be done with a brush. Avoid compressed air as it may embed metal particles where you least want them, like into lathe bearings, or worse yet, your eyes! Furthermore, compressed air cleaning increases the potential for airborne brake dust.

The protective boots or bellows that cover the various spindles and crossfeed mechanisms should also be inspected daily. If they’re cracked or torn, highly abrasive particles will quickly find their way into the lathe with disastrous results. These boots, especially the one near the arbor, should be kept in the shop as spare parts. What will you do if a silencer band flies off a rotor and wraps itself around the arbor, taking a hunk of boot with it? Will you immediately stop the lathe, remove the rotor and send it and the others out to a machine shop while you wait for a replacement boot? That will cost you time, money and a severe loss of productivity for that bay. Of course, you could continue to resurface drums and rotors until the new boot arrives. That could cost you even more!

Daily care should also be given to the various adapters, cones and hardware used to mount the drums and rotors to the arbor. They, too, live in a harsh environment. Dirty adapters increase the likelihood that a rotor or drum will be improperly mounted. If mounted crooked, the drum or rotor will be cut crooked. Not only will that cost you time and money, it may cost you a drum or rotor. It’s much easier to keep the parts clean and mount the drum or rotor correctly the first time than it is to try to “compensate” for the crud on the adapters. If they are simply wiped clean after every use, lathe housekeeping will be easy and second nature.

If you notice a tendency for the adapters to rust slightly, spray them with light penetrating oil and wipe them down thoroughly. You don’t want them to be oily; that could do more harm than good by attracting dirt and metal chips. The penetrating oil will find its way into the microscopic valleys of the metal, preventing rust and corrosion.

Arbors and adapters should be inspected for nicks and other damage. When mounting a heavy rotor or drum, it’s easy to inadvertently bang it into the arbor. A nick could cause misalignment. Nicks can be removed by carefully using a very fine stone (such as one for hand sharpening a knife). If the damaged cannot be removed, replace the part. If you suspect a bent arbor, you can check runout with a dial indicator. Some arbors have “witness marks” that should be aligned with the corresponding marks on the spindle. These marks are made to assure the least runout on the arbor during manufacturing process and testing at the factory.

Nothing has a greater impact on the surface finish of a rotor or drum than the condition of the tool bit. Dull bits will tear the metal leaving a rough finish which can cause brake noise, rapid pad wear and poor brake performance.

A quality tool bit will produce an excellent finish and last longer than the cheap stuff. This is especially important for one-cut capable lathes. Some lathes can produce a finished rotor with just one cut, but it’s not going to happen with a dull bit. Some manufacturers claim that their lathes are capable of removing .040” of material per cut. Try that with a worn out bit!

Too shallow a cut can actually shorten tool bit life by reducing the heat transfer from the bit to the rotor (or drum). The depth of cut and feed rate will have an effect on tool bit longevity.

Replace bits as needed as soon as you notice a degradation of surface finish.

Some on- and off-car lathes have oil that needs to be changed periodically. They may also have grease fittings that need to be given a shot of grease. There is generally a drain plug to allow easy draining of the lathe. Check the operator’s manual for the recommended type and capacity of oil.

There you will also find the recommended intervals for oil changes and lubrication. If your lathe is belt driven, check it occasionally for condition and proper tension. Since lathe belts are generally small, you may not be able to obtain one quickly if it happens to break in the middle of a job. Some lathe manufacturers offer “tune-up kits” for their lathes. These kits contain common wear items such as boots, belts, silencer bands, etc.

Don’t forget to check silencing devices. Rubber silencing bands should be inspected for rips and tears. A silencing band that comes off during drum or rotor machining can damage the lathe, or worse yet, cause personal injury to the operator. Friction silencing devices, those that lightly clamp the rotor between two friction pads, are particularly effective on thin, non-vented rotors. These rotors are often too thin to use a rubber silencing band. The friction pads should be inspected and replaced as needed.

If you want to keep the lathe area or your shop cleaner (due to desire or necessity), an enclosure may be the answer. An enclosure is a molded plastic “box” that fits around the complete lathe. It helps keep the vast majority of dust and chips confined to the inside of the box. If your lathe is near a workbench, office or some other area that you must keep clean, an enclosure might be just what you’re looking for. Additionally, the enclosure can help improve the air quality of the shop.

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