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What are Brake Lathes?

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  • Written By: Eric Tallberg
  • Edited By: Bronwyn Harris
  • Last Modified Date: 08 November 2016
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Essentially, brake lathes are metal lathes designed to turn automobile brake drums and rotors, as well as a number of other items. While traditional metal lathes suspend the piece to be worked horizontally between the rotating spindle and the tailstock, brake lathes are somewhat different. Brake lathes have only the spindle and the item to be machined is suspended vertically.

As with traditional metal lathes, brake lathes use cutting bits mounted on toolposts to cut into a rotating piece of metal stock. Bench-type lathes do not, however, have a traditional lathe bed simply because they are machining vertically rather than horizontally. Typically, bench-type lathes consist of the motor, which powers a rotating spindle, and the movable toolpost and bit. Various tapered arbors, designed to fit into the several sizes of brake rotors, are used in place of the chuck common to many traditional metal lathes.

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In the operation of brake lathes, the arbor is inserted into the center hole of the brake rotor and the arbor-mounted rotor is fitted onto the shaft of the spindle and secured with a locking ring. The motor is turned on and the spindle rotates the rotor assembly at a pre-determined speed. The toolpost and bit are maneuvered into place, either by a hand crank or mechanically, to begin scoring the rotor, thereby removing rust, dirt, and debris. As well, the bits will cut minute grooves into the rotor. These grooves are essential to providing the friction between rotor and brake pads necessary to good stopping power.

In addition to bench-type brake lathes, many repair facilities will have on-car lathes which do exactly what a bench lathe does. On-car brake lathes are much more compact than bench lathes and are designed, as the name implies, to be mounted directly to the vehicle, ordinarily on the wheel hub or brake calipers.

Though somewhat cumbersome and time-consuming to mount and set up, on-car brake lathes have two advantages over bench lathes. First, on-car lathes reduce rotor runout where the cut may not be deep or shallow enough by providing a more even application of cutting bit to rotor. Runout is simply an uneven rotor surface caused by imperfect machining or rotor wear and will result in a pulsation in the brake pedal when braking. Secondly, on-car lathes eliminate the expense and time needed to take off stuck or “captured” rotors, a common problem with abused or inferior brake systems.

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titans62
Post 3

What kind of material are brake lathe bits made from? Also, what exactly do they look like?

I have seen wood lathes before, so I am imagining something similar that is a curved piece of metal. I'm not certain, but I assume rotors are made from steel, so the cutting material would have to be harder than that, wouldn't it?

When you do get your rotors turned, how much of the metal does it actually take off of the rotor? I have never had it done, but does the extra distance the brake pad has to move cause you to stop slower for any reason?

JimmyT
Post 2

@TreeMan - First and foremost, I would recommend not driving your car unless it is absolutely necessary. The longer you drive with the bad brakes, the more damage you are doing to the rotors.

At this point, I'm guessing you may be able to get by with just replacing the pads. I find that a lot of times, mechanics try to overcharge on brake repairs by saying you need new rotors with they could easily use a brake lathe and repair them. I think it is probably the extra time for them that causes them to want to replace the rotors altogether.

If you live in a larger area like I do, you may be able to find individuals

who own brake lathes and will repair them for you. They will cost much less than a regular mechanic, but be sure you trust the person first. If you can, ask around and you may be able to find something like this.
TreeMan
Post 1

I have been having problems with my brakes grinding. I just noticed it a couple of days ago, and I know I need to get them fixed before any major damage is done.

I have been reading about different brake repairs and was wondering if anyone here might be able to give me some advice. From what I understand, I will have to get new brake pads, and there might be some damage to the rotor.

From what I have seen, as long as there isn't a lot of damage to the rotor, the mechanic should be able to fix it like the article here describes, right? How much will this usually cost? What would it cost if I have to get them replaced altogether?

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