Importance of foot brake on lathe

W

WVBrady

Guest
I am not even a neophyte yet (a nonophyte?), but I have a question based on the previous thread on lathes. Mickey stated that he didn't want a lathe without a footbrake. Is this a matter of convenience (time), or is a matter of safety?

TIA, Brady
 
Both.
I use mine for threading. When the tool gets into the undercut I stop the spindle with the brake. Back the tool out and go into spindle reverse without releasing the half-nut lever. Let the tool feed past the end of the part and reset tool position for the next cut. This eliminates using the half-nut lever and the possibility of cutting half threads. When you get on to this method it's slicker 'n seal s**t.
 
Primarily for safety. There was a picture posted on another forum where a guy got his heavy sweater caught in the work on a lathe. Evidently it was an older lathe and he worked in a big shop where heat was scarce. The sweater got caught in the work and he couldn't reach the switch. The chuck had to have been about 15 inch chuck and when they caught it the chuck had gone through his head and was stopped between his shoulder blades. You could see his brains and what was left of his face with an eye showing in the goo in the picture of the back side of the lathe.

You can't believe how quickly your day can turn into guano when you least expect it.
 
Thanks for the responses. Mickey: I think I saw the pictures of that accident. It was gruesome enough that I just looked at the first two pictures.

I have read many threads on the proper way to do such things as chambering and threading. Maybe someone would comment on such things as being in the proper position to apply the foot brake and other safety procedures. I have also read of instant reversing to stop the spindle. Is this a safety feature that is commonly used?

Yoo Hoo Shiraz Balolia! Would it be possible to add the foot brake to the G4003G ?
 
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On my lathe I use the foot break for SAFETY. I wired the switch of the foot break to the emergency stop contact points of the VFD. Stomp the break the spindle stops NOW and will not restart until you clear the fault on the VFD. I did this because I work in a one man shop and the shop is about 900 feet from the house. It is not uncommon for me to work past midnight and when I get to the house everyone is asleep, even if they were awake they would never hear me and they seldom come to the shop. I do have a telephone at each machine and a cell phone on me at all times just in case.

Nic.
 
Niccolo said:
On my lathe I use the foot break for SAFETY. I wired the switch of the foot break to the emergency stop contact points of the VFD. Stomp the break the spindle stops NOW and will not restart until you clear the fault on the VFD. I did this because I work in a one man shop and the shop is about 900 feet from the house. It is not uncommon for me to work past midnight and when I get to the house everyone is asleep, even if they were awake they would never hear me and they seldom come to the shop. I do have a telephone at each machine and a cell phone on me at all times just in case.

Nic.
Click to expand...
Sounds like a great idea. I had wondered if anyone had wired such a shutoff to the foot brake. I had also wondered if anyone had wired up some sort of switch similar to what motorcycle hillclimbers used to do. It commonly was as simple as a piece of hacksaw blade, tied to the rider's wrist by a cord, that completed the ignition circuit. Thus when the rider departed the saddle (which usually happened) it would kill the engine. It seems that it might be possible for you not to be able to get your foot on the brake in time. Even if the lathe is only running at 60 rpm, it still only takes one second to make a revolution, and many people do threading and chambering at much higher speeds. Do you keep your foot poised over the brake when operating the lathe? Please don't think I'm being critical; it seems like you are more safety conscious than most. I'm just trying to find the safest way to operate a lathe.

Thanks, Brady
 
On my lathe I use the foot brake for threading against a shoulder. It shuts off the power and also applies a brake to the spindle. It stops instantly.

As for saftey a few years ago I had a small moment of stupidity where I smashed my finger in the lathe. I never did think of hitting the brake. I was to concerned with getting my finger out of the pinch.

Gary
 
The foot brake is there for speed ( dont have to wait for spindle to stop), and to stop the spindle abruptly at an exact point in an operation. It also allows the motor to run constantly, so that we don't toast it by switching it on & off all the time.

The unfortunate guy in the picture Mickey mentioned probably didn't have a chance to get his weight shifted off of one foot, let alone hit the foot bar. (That machine was large enough that it probably had one, unless it was too ancient)

I don't see a reason to wire a switch into the brake to stop the motor...........Everything stops on lathes with the foot bar, except the motor and parts before the clutch, which are all enclosed. Making the motor stop every time the machine stops just beats the pulp out of it. Also, it slows you down a whole bunch.

-Dave-:)
 
Most of the newer/smaller lathes typical of the size used for gunsmithing don't have clutches, so the motor stops each time the brake is applied. The footbrake on my JET was wired to stop the motor and require the apron switch to be cycled through another off/on cycle to restart. Then we converted to a 3-phase motor and wired in a VFD to control it - now the brake still stops the spindle & motor, but when you release the brake, they both restart.
 
VFD's and lathe stoppage

Does the chuck stop immediately when using a VFD (variable frequency drive) or is there still mechanical momentum? Many of the overhead cranes in our power plant have VFD's for bridge and trolley motion with two controlling 15 ton aux. hoists. I've operated these cranes and when running the aux. hoist at full speed, then going to a dead stop, there is a small degree of mechanical inertia which keeps the hoist from stopping immediately. This small amount of additional motion could still injure a person running a lathe.
Chino69
 
flatlander said:
....Then we converted to a 3-phase motor and wired in a VFD to control it - now the brake still stops the spindle & motor, but when you release the brake, they both restart.
Click to expand...

Check your VFD and see if there are points for remote control inputs. If so wire your foot brake switch to the emergency stop control points. Having the lathe re-start when you release the foot brake is bad news.

Again depending on the make and model of your VFD there are many programming options. I have mine set for soft start and soft stop (takes awhile to spool up or down). Emergency stop (programmable) plugs the motor then removes power to the motor (plugging the motor is very hard on it). My foot brake is a disk brake; the pedal clamps a caliper down on a disk and opens the circuit via a switch. When voltage is removed from the emergency stop control point the VFD programming kicks in.

Be warned that stopping the spindle while taking a heavy cut or crashing into a shoulder on having the cross feed engaged instead of the longitudinal feed and going “O S%&*T and stomping the foot brake will leave a ton of pressure on the tool and it will shatter.

Please play safe,
Nic.
 
VFD's ROCK!

Chino
You can vary the parameters on most VFD's. How fast it starts and stops and many more variables. If you want an almost instant stop using the DC injection braking you would need an extra resistor. These braking resistors are very large and get pretty warm especially with many spindle reversals during CNC tapping an array of holes. VFD's are an excellent way to control ONE three phase motor. They only power three phase motors. But will convert single phase to three for motor applications ONLY. If you have many questions about these try calling Anton at http://www.precisionzone.com/
He repairs them & sells them new and used.
 
VFD's

gunmaker said:
Chino
You can vary the parameters on most VFD's. How fast it starts and stops and many more variables. If you want an almost instant stop using the DC injection braking you would need an extra resistor. These braking resistors are very large and get pretty warm especially with many spindle reversals during CNC tapping an array of holes. VFD's are an excellent way to control ONE three phase motor. They only power three phase motors. But will convert single phase to three for motor applications ONLY. If you have many questions about these try calling Anton at http://www.precisionzone.com/
He repairs them & sells them new and used.
Click to expand...

Gunmaker,
Thanks for the response. I'm familiar with the VFD circuitry and using dynamic braking resistors. Dynamic braking resistors take the back feed from the VFD and serve as a dynamic brake by freezing the rotor in place; creating alot of heat in the process. What I'm trying to get at is the built up inertia in any mechanical system which will tend to want to stay in motion. Even with dynamic braking, a large enough machine will still have built up momentum. Now bear in mind, my experience has been with large overhead cranes. I've programmed the VFD's for soft starts and time delays before the mechanical brake engages. For the cranes where a VFD drives the hoist, a sudden stop from full speed still has a little movement due to the inertia of the hoist drum. Granted, the motion is minimal but it's still there. I'm thinking that in the case of a normal sized lathe, the stop function would be instantaneous due to the rotating mass being much less than that of a hoist drum.
Chino69
 
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