If ever you have used a lathe fitted with a brake and liked it, then using other lathes not fitted with this will leave you with the feeling that something is missing, which of course it is. My small Chinese bench lathe does not have a brake, turn off the power and it coasts to a stop as you would expect. In most cases this is not an issue but it can be an irritation if, like me, you have limited patience. At other times, such as threading up to a shoulder, a brake is a nice thing to have. I decided to see if I could fit one to my lathe. A quick Google search did not reveal much, lathe brakes seem to be one of those things that most operators can do without. I decided to use a pushbike disc brake setup as they are fairly cheap to buy. I do not have the mathematical ability to determine if the disc and pads would be capable of absorbing the energy of the rotating lathe mass so this was going to be very much a suck it and see exercise.
I removed the end of the lathe, this is like a small cabinet with a lockable door that allows access to the drive belts and screwcutting gears. I mounted the disc on the end of the motor pulley via an adaptor spigoted and bolted to it. The brake callipers were attached to the bench the lathe is mounted on and then adjusted to ensure the pads did not rub on the disc, this was a bit fiddley to achieve and in the initial running some slight scraping occurred until the pads bedded in. I think this is usual on a new bike setup but I have never owned a bike with disc brakes.
The brake pedal was a bit of messing around but in the end worked OK. I wanted to incorporate a micro switch into the design to cut the power to the motor contactor coil prior to the callipers engaging the disc, the pictures explain. The disc brake is actuated by a standard bike cable attached to the pedal. The theory is that when the pedal is depressed, firstly the power is disconnected from the drive motor via the micro switch then the brake pads engage the disc and stop the lathe.
The system worked much better than I had hoped. Depressing the pedal brings the lathe to an instant stop, regardless of the rotational speed selected. The highest speed of my lathe is 1600 rpm but I can honestly say that I have never machined anything at that speed, certainly not cutting a thread to a shoulder! After five or six quick stops at mainly 700 rpm I felt the disc and pads and they were barely warm. This indicated to me that the setup was capable of absorbing and dissipating the energy OK. My lathe chucks bolt to the backplate so I had no qualms about operating the brake in either direction of rotation. I suppose that there will be some that will say that I am imposing a big load on the bearings etc, but I think that they will handle it OK, mainly because I dont think the decelerational load is very much more than the accelerational, also, the brake will not be used all that much, only when the particular machining operation calls for it. I am quite prepared to stand corrected on this and invite comments. As a safety feature I personally would rather have it than not. I think I could stomp on the pedal quicker than I could reach the emergency stop button, plus it would have the added advantage of instant stop of the lathe. Just my opinion.
Costs was pretty minimal, around A$40 from BangGood in HK. I had to modify the end of the lathe as the original end would no longer fit but it came out all right at the finish. Obviously a bigger lathe would require a bigger disc setup, possibly twin discs and use hydraulic actuation rather than cable. The application of a bit of math would help as well. Here is a link to a brief video https://youtu.be/_2dwS6Xu9A4 Hope you enjoyed this post, all comments are welcome, Cheers, Peter.
I removed the end of the lathe, this is like a small cabinet with a lockable door that allows access to the drive belts and screwcutting gears. I mounted the disc on the end of the motor pulley via an adaptor spigoted and bolted to it. The brake callipers were attached to the bench the lathe is mounted on and then adjusted to ensure the pads did not rub on the disc, this was a bit fiddley to achieve and in the initial running some slight scraping occurred until the pads bedded in. I think this is usual on a new bike setup but I have never owned a bike with disc brakes.
The brake pedal was a bit of messing around but in the end worked OK. I wanted to incorporate a micro switch into the design to cut the power to the motor contactor coil prior to the callipers engaging the disc, the pictures explain. The disc brake is actuated by a standard bike cable attached to the pedal. The theory is that when the pedal is depressed, firstly the power is disconnected from the drive motor via the micro switch then the brake pads engage the disc and stop the lathe.
The system worked much better than I had hoped. Depressing the pedal brings the lathe to an instant stop, regardless of the rotational speed selected. The highest speed of my lathe is 1600 rpm but I can honestly say that I have never machined anything at that speed, certainly not cutting a thread to a shoulder! After five or six quick stops at mainly 700 rpm I felt the disc and pads and they were barely warm. This indicated to me that the setup was capable of absorbing and dissipating the energy OK. My lathe chucks bolt to the backplate so I had no qualms about operating the brake in either direction of rotation. I suppose that there will be some that will say that I am imposing a big load on the bearings etc, but I think that they will handle it OK, mainly because I dont think the decelerational load is very much more than the accelerational, also, the brake will not be used all that much, only when the particular machining operation calls for it. I am quite prepared to stand corrected on this and invite comments. As a safety feature I personally would rather have it than not. I think I could stomp on the pedal quicker than I could reach the emergency stop button, plus it would have the added advantage of instant stop of the lathe. Just my opinion.
Costs was pretty minimal, around A$40 from BangGood in HK. I had to modify the end of the lathe as the original end would no longer fit but it came out all right at the finish. Obviously a bigger lathe would require a bigger disc setup, possibly twin discs and use hydraulic actuation rather than cable. The application of a bit of math would help as well. Here is a link to a brief video https://youtu.be/_2dwS6Xu9A4 Hope you enjoyed this post, all comments are welcome, Cheers, Peter.
