Do You Use the Foot Brake

[Bob La Londe]

Some times when I am making a bunch of repetitive parts I'll use the foot brake. Over the course of 20-30 of some common parts I make it can save an hour or more over waiting for the spindle to spin down on its own. (single phase 3HP lathe) I'm just concerned about additional wear and tear on the machine from that sudden stop.

Please try to be civilized in your responses. If we get the usual derogatory judgementalism I'll request the thread be removed.

If you have an opinion or solid feed back please feel free to share it.

One of the things I've considered is swapping out the spindle motor for a 3phase motor with VFD and large braking resistor. It won't be the instant stop of stepping on the brake bar, but I could reduce spin down to 1 or 2 seconds I think. It would have the advantage of being able to finish difficult heavy feed materials faster as I could increase RPM more easily with decreasing diameter. A programmed soft start could also help when spinning up in higher gears.

[Tim Clarke]

I have a brake on my Turnmaster I don't use it much, Just enough that I can react quickly if something goes south. (JERRY) Mine is pretty easy to apply gently, and there's also a cutout switch that drops power to the motor when I use it for the rare panic stop.

[Bob La Londe]

Yes. Stepping on the bar is the same as lifting the shield. It stops the spindle power and you have to move the switch back to the center position before you can restart.

[BCRider]

I envy you guys with the machines that can just disengage a clutch and brake the spindle for doing work that requires frequent stops.

Bob, I assume that the brake has the ability to feather out the stop so it's not a sudden slam? If so and you temper it so it slows over something like even a half second I can't see that being at all harsh on the machine parts. You just want to avoid a sudden SLAM! that makes the swarf jump up in the chip tray.

As for using the motor with some modification to do the braking? It takes extra power to accelerate the spindle during startup. And with a new setup you'd be directing that inertial energy back into the motor and some braking function in the VFD. And that is going to show up as extra heat being dissipated by the motor and VFD.

Now 98.7% of the time you'll still be well within the max power continuous rating of the system even with the reverse energy dumped back into the electrical side. But perhaps one day you'll find yourself doing some major hogging work on big parts done in rapid sequence. Something that involves using the full 3HP to run the spindle up to speed, 3hp to make the heavy cuts and makes the machine grunt hard and finally you shut off and dump 3hp worth of power into the electrical brake. Rinse and repeat in rapid succession. And on that day you might find that things get toasty enough to make you notice. On that day the probably 10% of the power that would have gone into the mechanical brake might make for a 10 or 15 degree lower temperature of the motor and power supply. For the other 98.7% of the time when we don't use the machines to anything like their full power rating? Not an issue at all.

[Captain K]

I can’t help with the foot brake question. However I did install a vfd with properly sized braking resistor on my 3hp Colchester Student and it works awesome. I think I set it for a second or less to stop. It works flawlessly up to max 1500rpm speed of the lathe with a 6 or 8 inch 3 jaw chuck. I don’t run the 4 jaw that fast. The vfd is a Fuji Frenic

[Tobias-B]

Seconded for the VFD braking-
if I had a foot brake, I'd use it, but as the brake on the Bridgeport's worn out,
and the lathe never had one,
setting the braking appropriately sure saves time on both machines.

So yes, if I HAD one, I'd use it!

t

[Bob La Londe]

You just want to avoid a sudden SLAM! that makes the swarf jump up in the chip tray.

Um, yeah. LOL. Lets not do that.

I'm not 100% convinced on going to 3 phase, but I would go with the typical 30-40% over size just like I would on any other 1 to 3 phase VFD application.

[Bob La Londe]

...but as the brake on the Bridgeport's worn out,

I haven't had the new South Bend Knee Mill a full year yet, but I've gotten spoiled with the spindle brake. I think that's something I would fix if it was worn out. I use a spanner on the keyless chuck all the time when I need to do heavy drilling with one hand on the brake lever, and the spindle brake makes for easy quick tightening by hand for light drilling and spotting.

[Captain K]

There is no need to oversize the vfd. If it’s single phase input it will put out rated hp. The derating thing is out of date. This is with quality, genuine drives. All bets are off on others.

[Tundra Twin Track]

[QUOTE=BCRider;n1981896]I envy you guys with the machines that can just disengage a clutch and brake the spindle for doing work that requires frequent stops.

BC a lot of Lathes with Foot Brake don’t have a clutch,the foot brake kills power to the Motor before any braking takes place.

[BCRider]

[QUOTE=Tundra Twin Track;n1981950]

I envy you guys with the machines that can just disengage a clutch and brake the spindle for doing work that requires frequent stops.

BC a lot of Lathes with Foot Brake don’t have a clutch, The foot brake kills power to the Motor before any braking takes place.

Gotcha. Sort of a middle ground before stepping up to the big stuff where the motor runs for the whole session? I see that on lots of the bigger lathes in various machining videos.

I do a lot of stopping and starting on my 12x36 to get measurements or for small parts. From medium fast to stopped I timed mine just now out of curiousity and it seems to be roughly 1.8 seconds with the 6" chuck. From medium slow it's just under 1 second. And when I'm in a rush to get on with things that 1.8 seconds seems nigh on FOREVER ! ! ! !

These times go up by probably double when the 8" four jaw "lump" is on the machine. I didn't swap chucks to time it but it always made me notice how much longer the spin down required. And come to think of it this alone makes me happy that I've never felt the need to step up to an 8 inch three jaw. It's so rare when I need the extra size that I just swap to the 8" four jaw. And being a 4 jaw it has a generous center bore to boot.

Bob, I'm glad you got a chuckle out of my "making the chips jump" comment ....

[Tundra Twin Track]

[QUOTE=BCRider;n1981953]

Gotcha. Sort of a middle ground before stepping up to the big stuff where the motor runs for the whole session? I see that on lots of the bigger lathes in various machining videos.

I do a lot of stopping and starting on my 12x36 to get measurements or for small parts. From medium fast to stopped I timed mine just now out of curiousity and it seems to be roughly 1.8 seconds with the 6" chuck. From medium slow it's just under 1 second. And when I'm in a rush to get on with things that 1.8 seconds seems nigh on FOREVER ! ! ! !

These times go up by probably double when the 8" four jaw "lump" is on the machine. I didn't swap chucks to time it but it always made me notice how much longer the spin down required. And come to think of it this alone makes me happy that I've never felt the need to step up to an 8 inch three jaw. It's so rare when I need the extra size that I just swap to the 8" four jaw. And being a 4 jaw it has a generous center bore to boot.

Bob, I'm glad you got a chuckle out of my "making the chips jump" comment ....

The Brake Drum on mine is mounted on Motor Shaft and will stop the 12” Chuck in a split second if needed,I rarely ever STAND ON IT that hard.

[Tundra Twin Track]

I haven't had the new South Bend Knee Mill a full year yet, but I've gotten spoiled with the spindle brake. I think that's something I would fix if it was worn out. I use a spanner on the keyless chuck all the time when I need to do heavy drilling with one hand on the brake lever, and the spindle brake makes for easy quick tightening by hand for light drilling and spotting.

Bob what style of Brake does your Bridgeport have,I’ve also gotten spoiled by having a Brake on my Varnamo great for tooling changes in Park Mode.

[Noitoen]

When I installed a new motor on my lathe for the VFD, I also installed a bicycle brake disk. It helps with threading a lot. I I press the pedal lightly it will coast to stop by just stopping the VFD and pressing harder will actuate the caliper and I can stop almost instantaneously if I want but then i'ts just a small lathe

[Tobias-B]

yeah, I have been meaning to fix the brake on the mill for ages.

And I hadn't given the lathe much thought- but fitting a disc
and a caliper in the cabinet below wouldn't be hard at all.

Of course, the threaded spindle nose might have something to say about that...

t