View Full Version : Lathe safety brake
Does anyone have experience with a lathe equipped with a foot brake?
I am considering making a brake for a lathe I recently bought and want to make sure I'm going about it correctly.
It goes without saying that there must be a switch to cut power to the contacter coil.
Am I correct in assuming that they use a band brake to stop the spindle? If so, is the brake applied on the input side of the gearbox or on the spindle itself? If not what sort of mechanism is used?
Any information pertaining to this or any other saftey devices for a lathe is greatly appreciated.
Thanks in advance. http://bbs.homeshopmachinist.net//smile.gif
10-13-2002, 01:01 PM
I would worry that braking the lathe spindle would allow a chuck to spin off. Just turning one off while at high speed revolutions can cause the same. Maybe there is a brake that slows the spindle by contacting the chuck in some way?? (just thinking out loud here)
Thanks for mentioning it.
I had planned on preventing that by either keying or setscrewing or pinning the chuck backplate to the spindle.
Also its a gear head so the speeds are relativly slow (low speed 15 RPM)and the chuck back plate is a very tight fit on the spindle and large (3"-5 TPI) so I don't think it will be a problem.
Incidently for those who have had morse tapers come out in use, I have a setscrew on my DP spindle to hold tapers in. This will solve the problem 99% of the time when its impossible to use a drawbar. http://bbs.homeshopmachinist.net//cool.gif
10-13-2002, 08:01 PM
Enterprise put a foot brake on their 15" lathe. BUT it is a D1-4 Spindle. My DoAll 13" also has a brake and a D1-4 spindle. There is no way in He_ _ I would put a brake on a lathe with a threaded spindle--I just can't picture myself catching a rolling chuck with my valuable part in the jaws. Or as far as that goes my valuable parts in its jaws.
10-13-2002, 08:06 PM
The lathes we had in the school where I got started in this hobby had a couple of handles under the front of the carriage that you had to move to start the spindle to turning. When you let go, or pushed it to the other extreme, the spindle would brake and very rapidly. I never say any of those machines lose a chuck and they all had threaded spindles.
10-13-2002, 08:08 PM
Oh, I forgot to mention that they all had variable speed hydraulic drives in them.
10-20-2002, 12:52 PM
You shouldn't have a problem with the chuck spinning off, as long as the taper has a key in it. If there is no key, I wouldn't advise it. Just keep an eye on the threaded collar, but as long as you tighten it good, it should be fine. (I have never had one come off, my old L&S 16" lathe had a brake, along with reverse). I have a brand new lathe sitting here that has a foot brake on it. It has a cut off switch, just like you had mentioned, and a band for a brake. Send me your email address, and I can take a picture of the brake system and email it to you. My email is firstname.lastname@example.org.
If I do build a spindle brake for the lathe
and can not key or pin the chuck on the spindle would a drawbar be enough to keep it from spinning off when braking? (breaking http://bbs.homeshopmachinist.net//biggrin.gif)
(Similar to the left hand screw that holds on drill chucks on reversible drills)
12-02-2002, 07:44 PM
Most of the comercial ones I've seen are set up like drum brakes acting on the inside of the pulley on the input shaft. One of the guys in the shop just fixed one a couple of weeks ago. The moron out in the repair area wasn't satisfied unless he stomped on the foot pedal. Twisted the engagement pin in the likage so bad the pedal had to be depressed just to disengage the brake. If you can figure out how to put one in go with an electromagnetic brake instead.
12-04-2002, 01:19 PM
I have thought about this same redo on my lathe and here are a couple of ideas I have tossed around. First off the Clausing lathe had it right by not stopping the motor when braking the spindle. Two ideas that came to mind are, the motor drive on my upholstery machine and my lawn tractor power take off. This is going to be basic but here is how they work. The motor on my upholstery sewing machine has an extended shaft with a flange at the one end closest to the motor and which are spinning with the motor. Another stationary flange at the opposite end of this shaft which is supported by a ball bearing on the shaft. Between these flanges is mounted a cylinder with a pulley to drive the sewing head and with two friction dics on both ends which will come in contact with these flanges. An angular ball bearing is also mounted in the center of the cylinder, this has to be seen since it gets too hard to explain, but is basically the throw out bearing. With the motor on and you engage the pedal, the cylinder moves into the flange of the motor causing the cylinder to spin with motor, to stop you need only to release the pedal and a spring pulls the cylinder back into the stationary flange stopping it instantly. The only thing that you would have to do is reverse the spring direction making it hold the motor and cylinder together to drive the lathe and then stepping on the pedal would shift the cylinder over to stationary flange to stop the spindle from turning. At this point the redesign might be better with a handle or pedal with a positive off position rather than momentary one since lifting your foot would re-engage the spindle.
The second one is like the A/C clutch drive unit on you car which is an electromagnetic device. The only difference is that when I switch off the PTO on the tractor the backside of the clutch is made to spring back against a flange stopping it from spinning. Sorry for poor explanations of these devices but I think they have some possibilities if you are mounting the device on the motor. It also would allow you to stop the spindle without shutting off the motor each time which is another reason I wanted to have this set up.