One of the projects on my to do list.. A foot brake for the SB 9 lathe.

[Alcap]

If I’m understanding , you’ll have a foot brake and power switch combined ?

 

[rwm]

Curious how you prevent over travel of the cable from damaging the caliper or stretching the cable?

 

[Lucas E]

A foot brake may help in an emergency situation, but if the chuck unscrews while your using it you've just created another emergency. I've been looking into ways to clamp my 3 and 4 jaw chuck onto the spindle of my heavy 10 so I can run a VFD with brake and proximity switch.

So far I think this clamp design will work best. Clamp it onto the backplate OD, and then onto the OD of the spindle flange. I've modeled one up with holes to match my 3 jaw chuck and the spindle flange and calculated the hole locations to balance it, but haven't started building one. I'm a little cautious as I haven't seen anyone successfully using one on a southbend lathe.

 

[graham-xrf]

My machine takes way too long to stop for my satisfaction. At a minimum this might prevent a crash. If I ever get clothing (or worse) caught in the lathe I will really regret not doing this. I also looked at snowmobile brakes, but this seems easy and robust enough to do the job. Thanks for posting.

What kind of motor drive combination do you have? We know that VFD's and servos often have the braking dump resistor, and a current control parameter to brake to a safe stop without busting things. In principle, if you just switch off, the motor is spinning from combined inertias, and generating a voltage (if there is any field left). Connecting to resistive loads makes the motor see a braking force, even though it's still running forwards. With VFDs, you can program the stopping time. With other motor drives, it's about choosing the right resistances to switch in. When it comes to squirrel-cage induction motors, I am not so sure.

I am having to dig deep in the memory here, but I do recall being told that all machines, even induction motor types, can be arranged to connect to a braking resistor load that connects when the motor switch/contactor goes to the OFF position. I have done the trick myself, but with permanent magnet multi-pole motors. The dump resistance does not have to be rated for continuous motor power. About 10% is enough, because it is only used intermittently. The resistor value is chosen to have an initial braking current some reasonable fraction of the motor power, As the motor slows, this current declines to zero, as does the braking effect. I chose to have the run-down time about 1 second, which seemed swift enough without getting violent.

 

[DavidR8]

A foot brake may help in an emergency situation, but if the chuck unscrews while your using it you've just created another emergency. I've been looking into ways to clamp my 3 and 4 jaw chuck onto the spindle of my heavy 10 so I can run a VFD with brake and proximity switch.

So far I think this clamp design will work best. Clamp it onto the backplate OD, and then onto the OD of the spindle flange. I've modeled one up with holes to match my 3 jaw chuck and the spindle flange and calculated the hole locations to balance it, but haven't started building one. I'm a little cautious as I haven't seen anyone successfully using one on a southbend lathe.

Not a Southbend but

Locking on a threaded chuck ?

Howdy Guys....and Gals if your out there ! ... I have been contemplating the threaded chuck coming off when using reverse on the motor problem..... ..... I would imagine a simple screw into the side of the chuck adaptor would cure this problem.... but I've never read where anyone has tried...

www.hobby-machinist.com

Locking Threaded Chucks

Thought I'd revive this topic based on some chatter on @YYCHM's threading tool thread (see what I did there?) The perennial question of how to reverse thread on a lathe with a screw-on chuck. There's this example...

canadianhobbymetalworkers.com

 

[rwm]

What kind of motor drive combination do you have? We know that VFD's and servos often have the braking dump resistor, and a current control parameter to brake to a safe stop without busting things. In principle, if you just switch off, the motor is spinning from combined inertias, and generating a voltage (if there is any field left). Connecting to resistive loads makes the motor see a braking force, even though it's still running forwards. With VFDs, you can program the stopping time. With other motor drives, it's about choosing the right resistances to switch in. When it comes to squirrel-cage induction motors, I am not so sure.

I am having to dig deep in the memory here, but I do recall being told that all machines, even induction motor types, can be arranged to connect to a braking resistor load that connects when the motor switch/contactor goes to the OFF position. I have done the trick myself, but with permanent magnet multi-pole motors. The dump resistance does not have to be rated for continuous motor power. About 10% is enough, because it is only used intermittently. The resistor value is chosen to have an initial braking current some reasonable fraction of the motor power, As the motor slows, this current declines to zero, as does the braking effect. I chose to have the run-down time about 1 second, which seemed swift enough without getting violent.

I am using an SCR drive with a DC motor. The spin up/down is programmable to some extent. For routine start and stop I did not want to tax the controller and motor so I have about a 3 second stop depending on RPM. It has an E-stop which is quicker, about 1.5 sec. The E-stop button is not as easy to find as the foot actuated bar shown here. Also, that brake seems to stop the spindle almost instantaneously! I like that. My Southbend has a D1-3 spindle so no worries about the chuck spinning off.

 

[graham-xrf]

I am using an SCR drive with a DC motor. The spin up/down is programmable to some extent. For routine start and stop I did not want to tax the controller and motor so I have about a 3 second stop depending on RPM. It has an E-stop which is quicker, about 1.5 sec. The E-stop button is not as easy to find as the foot actuated bar shown here. Also, that brake seems to stop the spindle almost instantaneously! I like that. My Southbend has a D1-3 spindle so no worries about the chuck spinning off.

OK - a DC motor with it's own permanent magnets, and DC motors that have access to field coils can be used to have electrical reverse torque braking control into a dump resistor, but it seems you don't need that, because you already have a controller, and you have augmented it with a separate mechanical brake. I think that's a really cool mod. Braking right at the motor shaft does mean the force to bring the inertia of the lathe moving parts has to go via the belt drive train. Provided you are happy that a real swift stop is not going to hurt anything, it's great! That is the kind of thing you can sense when you try it. On a South Bend, maybe a belt might slip a bit.

I had looked at the Joe Pieczynski favourite method of threading with lathe in reverse, and threading away from the headstock, with the tool mounted upside down. It is a completely safe way that avoids ever running into a stop, nor needing lightning fast reactions to disengage the half-nut. For those who keep in sync without using a thread clock dial, by keeping the half-nut engaged all the time, taking a cut, then running backwards to the beginning to take another cut, it requires a fast reaction, and a damn fast braking to a stop in the thread gutter without traveling too far.

The whole deal about running in reverse, Joe Pie style, would unwind my chuck. There are some solutions suggested, including one which amounts to using a kind of draw-bar to hold the chuck on. I don't know about a D1-3 spindle. I guess your Southbend is a more modern one.

Joe Pie's method. Maybe if he had a brake like yours, he wouldn't bother.
Threading on a manual lathe BEST TECHNIQUE EVER !!!!

 

[f350ca]

Had a Taiwanese 14 - 40 with a foot brake. It used a D something or other chuck so no worries of it coming loose. Loved it. Would stop on a dime when threading up to a shoulder.
The Summit uses wet clutches and a brake on the spindle. Stops pretty quick at low speeds but nothing like that foot brake.
The Hardinge has a pad brake on the motor pulley, slows it down a lot faster than not having it, but you have to disable it to rotate the spindle by hand.

Greg

 

[woodchucker]

OK - a DC motor with it's own permanent magnets, and DC motors that have access to field coils can be used to have electrical reverse torque braking control into a dump resistor, but it seems you don't need that, because you already have a controller, and you have augmented it with a separate mechanical brake. I think that's a really cool mod. Braking right at the motor shaft does mean the force to bring the inertia of the lathe moving parts has to go via the belt drive train. Provided you are happy that a real swift stop is not going to hurt anything, it's great! That is the kind of thing you can sense when you try it. On a South Bend, maybe a belt might slip a bit.

I had looked at the Joe Pieczynski favourite method of threading with lathe in reverse, and threading away from the headstock, with the tool mounted upside down. It is a completely safe way that avoids ever running into a stop, nor needing lightning fast reactions to disengage the half-nut. For those who keep in sync without using a thread clock dial, by keeping the half-nut engaged all the time, taking a cut, then running backwards to the beginning to take another cut, it requires a fast reaction, and a damn fast braking to a stop in the thread gutter without traveling too far.

The whole deal about running in reverse, Joe Pie style, would unwind my chuck. There are some solutions suggested, including one which amounts to using a kind of draw-bar to hold the chuck on. I don't know about a D1-3 spindle. I guess your Southbend is a more modern one.

Joe Pie's method. Maybe if he had a brake like yours, he wouldn't bother.
Threading on a manual lathe BEST TECHNIQUE EVER !!!!

Joe Pie did not come up with the reverse threading. But he did teach many about it. I met a machinist when I started that told me to thread in reverse when needing to come close to a shoulder. I have used it a long time. And Joe reinforced it. Joe has taught me many things.