Don't run the boring bar into the chuck jaws on the end of the hole

My lathe has a foot brake, and it is pretty useless like the other controls when something unexpected happens. By the time you get it stopped it has probably already bashed something pretty good. However, the foot brake is perfect when you are anticipating needing to use it. I have used it for metric internal threading tight up to a shoulder, leaving the half nuts engaged. No problem. My foot brake stops the spindle instantly if I have my foot resting on it and am mentally geared up to use it, even at higher speeds. I occasionally find it really useful.

I would love to have a foot brake, but unfortunately I would have had to go up a size to get one and that machine would not fit in the space I have, however as I said I'm thinking about making a carriage stop that will trip the feed, not a total solution, but a move in the right direction. I'm even thinking of how to fit a clutch/brake to the lathe, any ideas would be welcome. I'm thinking in terms of an automotive electric A/C clutch fitted to the motor. They can usually handle quite a few HP. and a second one fitted to the pulley at the lathe end of the belt, set up as a brake. Could be set up with a button connected to a foot bar to simultaneously disengage the motor and apply the brake, a separate lever could be used just as a clutch. I like the idea of a clutch very useful when doing a lot of stop/start work.
 
Glad to say I have yet to smash the chuck on the carriage.
But, I have, however, dropped the 6" 4 jaw on my hand unscrewing it from the spindle... I suppose better bruise my hand than damage the ways.....

It's always a good idea to place a wooden board on the bed under the chuck when removing, also useful when putting large heavy items in or out of the chuck.
 
One thought on emergency braking that comes to mind is the braking power of a VFD. I have mine set for gentle braking, but could ramp it up. I suppose it depends on the VFD, but they might be able to stop that motor very quickly. Rig up your emergency switches/stops to go through the VFD and it may work well.

Chris
 
This is my carriage stop, but I do not recommend it.
That's the metric clone. Each of the inscribed rings is mm of interference, so just divide by 25.4 to get inches of crash :)
 
Wonder if a solenoid would have enough throw. Fooled around with bikes alot and the caliper brakes don't require much movement to draw tight. Whether they would have enough clamping force to do anything is another matter. Asco Red Hat solenoids are pretty reliable.

-frank
In my experience it is easier/better to use a solenoid (or hydraulic or air cylinder) to hold a brake OFF. Use spring pressure to apply the brake. You can adjust the clamping force by the spring size (belville washer stack) and adjust the application rate by using a flow control valve when using a hydraulic or air cylinder.
 
Bah!

At least you didn't bore your MT3 headstock spindle straight for half an inch...

[oh, a squirrel!]
Oh, I have better than that! I know you guys get tired of my stories, but we got to keep this trade going.

Dad told me of a man, wasn't him, working on night shift, was running a old lathe. He was spade drilling a hole in a piece of iron, I'm guessing somewhere around 3" in diameter. He doze off, next thing he wakes up and the chuck and piece of iron is just sitting there not turning on drill bar. The lathe was still running. He had bored thru the piece of iron, thru the chuck into the spindle until the part holding the chuck on parted off! What a mess he created!

Well, being a oilfield machine shop, they were always fixing someone's mess up. The man bored a box tool joint connection in the spindle. Then on another lathe, made a pin connection to fit the freshly made one in the spindle. Made it up in the spindle, finished the outside to fit the chuck. (I assume the original spindle was threaded as most older machines were made that way) And threaded the chuck on and went about his business like nothing happen. Don't know if the boss ever found out either!

Much for my story telling for the day.

Ken
 
In an extreme case, I remember the story about a guy at Mare Island Navy Yard who had a job boring a long hole, when suddenly the chuck fell off; he had continued his cuts until he bored all of the spindle away; I think the story went that when this happened, he put his tools away, picked up the tool box and left the premises (permanently).
 
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