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TR
02-25-2013, 08:14 AM
What is the purpose of the spindle brake ? Is this a desirable feature to have ? I have noticed on some mills when one presses stop, the spindle may take up to 5 to 10 seconds to come to rest. I like to think, that if I press stop, it stops.

Love to hear what the experts think ?

http://i663.photobucket.com/albums/uu354/topari/spindle_brake_zps05d13f7a.jpg

Dr Stan
02-25-2013, 08:25 AM
Just like the brakes on a car the spindle brake can help in an emergency and also save time rather than just waiting for it to coast to a stop. Also just like when you change a tire/cutting tool, it will keep the axle/spindle from rotating and help make the job easier.

On some mills, like the Bridgeport & its clones, the off switch & the brake are separate. The Lagun however, has an off switch as part of the brake allowing one to stop it in one motion making it easier & faster. BTW, this is just one of many features of the Lagun that IMHO make it superior to a BP.

taydin
02-25-2013, 08:25 AM
When the spindle speed is set to slow using the gearbox, it takes reeeally long for the spindle to stop. In these cases, you definitely need the spindle brake.

Lew Hartswick
02-25-2013, 08:26 AM
Don't know about that mill but on a Bridgeport you need the manual brake to
be able to un-screw the draw bar. And to get the spindle stopped in a reasonable
time to change cutters if you are running at a reasonable speed.
???
...lew...

bborr01
02-25-2013, 08:39 AM
Dr Stan and Lew pretty much covered it.

Brian

Mcgyver
02-25-2013, 08:43 AM
i don't use it often running the mill, probably should, but didn't want to have to 'do a brake job' one day some use it sparingly.

where it is handy is to lock the spindle when using an indicator in the spindle, or a shaping operations - ie V tool for graduating dials etc

Black_Moons
02-25-2013, 08:44 AM
Depends.
a friction brake will slow it quickly, good for tool changes, better for CNC, of course a VFD with a good braking resistor will do nearly as well (and wear less), Makes more sense when tapping and on lathes.

a 'peg' that goes into a hole to 'lock' the spindle is only good for unscrewing drawbars and such. it is NOT good for tightening ER32/40 collet chucks as those need 100ft-lb+ of torque and the pegs are only designed for drawbar level torque.

Personaly, I just stick my mill in low gear range and 'wack' the wrench with my hand (it has a hammer on the other end, so nice large area to avoid hurting my hand) to tighten/loosen it.

Uncle O
02-25-2013, 12:22 PM
It is a brake. Use it.
It is not some god awful thing if you should need to go into the head and replace it...
Are you not machinists ? Are you not comfortable with "machines" ? How they work ? How they come apart, go together...?

I just can't understand the reluctance to use the thing ....It is downright silly.

lakeside53
02-25-2013, 12:27 PM
Mine just sits like a useless ornament most of the time. I have an air draw bar and aggressive vfd braking.

About the only time I use it is when my air drawbar gets stuck (need to fix that!...) ;)

Weston Bye
02-25-2013, 12:31 PM
Has anyone here actually worn out a spindle brake on a Bridgeport? How soon will I need to replace mine?

lakeside53
02-25-2013, 12:38 PM
You might not, but some guys do expecially if the BP was in a production environment. Just like a car... some wear out the brakes every 30,000.. some get 120,0000+ (my wife).

I've replaced the shoes on a few, and... on two the inside of the pulley was badly worn. I had to take a skim cut (not a great idea as it changes the brake fit radius) and build up the actuator cam to get reliable braking/holding.

J.Ramsey
02-25-2013, 12:58 PM
I use mine all the time when power tapping.

MaxHeadRoom
02-25-2013, 02:24 PM
On the Excello I retrofitted, it is only used for tool changes when stopped, Kwik-Change300.
The VFD stops the spindle in around 4 secs from high RPM.
The brake is only enabled by an At-Zero-speed output on the VFD to prevent activation any other time.
Max.

rohart
02-25-2013, 05:04 PM
I'm very glad I have an emergency stop and brake on my lathe. I just wonder if I'll remember it's there if I ever need it.

I've also used the brake when threading up to a shoulder. I don't use it this way often - the screech of the brake block in the pulley wakes the house up.

I know what's meant about a mill slowing down really slowly, especially in low gear. Which, incidently, is when I'd want it to stop quickly, as I mainly use slow for tapping. But I run it on a vfd, and I've never bothered to up the braking actiuon, so it seems that it doesn't bother me.

Where I'd really like a brake is on my bench grinder, as I often brush clothing or flesh past the freewheeling grinding wheel, and that hurts.

PixMan
02-25-2013, 06:03 PM
The brake on my overly-worn 1960 Bridgeport needed replacement shortly after I got it in 2004. It looked original. It was about a 2 hour job to change it, but if that happens every 44 years I'm OK.

I have 3-phase power and don't use it for power tapping and have quick reversal, but do use it almost every other time. It makes changing tools easier (no power draw bar), and it saves waiting for a tool to stop spinning before I change a part in the vise or make a measurement.

oldtiffie
02-25-2013, 06:37 PM
I use mine all the time when power tapping.

One of the problems there is that if the chuck or collet doesn't slip the tap is subjected to low speed high torque which may break the tap even before it has "bottomed" or if it has "bottomed".

I have a Seig SX3 mill which has a tapping facility but has the same risks.

http://www.machineryhouse.com.au/M155

I prefer to use a tapping head in my mills (MT3) or my pedestal drill (MT2) as if correctly set the torque set will "render" (slip) betwwen what is required to drive the tap and snapping it. I don't have to stop or reverse my machine spindle (it can be left turning or switch off) as my tapping head will reverse when it is at its pre-set depth.

http://www.machineryhouse.com.au/T002

http://www.machineryhouse.com.au/T004

PixMan
02-25-2013, 08:09 PM
When I power tap on the Bridgeport (a 1HP step pulley one), the tap is in a drill chuck and may slip a bit. Usually, it just flows through as I use a higher speed than many and a tapping compound. I do not drill holes oversized to make tapping easier, and the only time I use the spindle brake is at the end of the sequence. Here's a quick video of tapping a 1/2"-13 through hole in 1" thick 1117 CRS:

http://www.youtube.com/watch?v=anR-E2AVUzU&feature=share&list=UUDlpWhxakPMd4fAqCJOzU_g

I have tapping heads but don't use them because it takes to long to crank the table down and back up. Those things take up a lot of spindle-to-table space!

oldtiffie
02-26-2013, 12:52 AM
When I power tap on the Bridgeport (a 1HP step pulley one), the tap is in a drill chuck and may slip a bit. Usually, it just flows through as I use a higher speed than many and a tapping compound. I do not drill holes oversized to make tapping easier, and the only time I use the spindle brake is at the end of the sequence. Here's a quick video of tapping a 1/2"-13 through hole in 1" thick 1117 CRS:

http://www.youtube.com/watch?v=anR-E2AVUzU&feature=share&list=UUDlpWhxakPMd4fAqCJOzU_g

I have tapping heads but don't use them because it takes to long to crank the table down and back up. Those things take up a lot of spindle-to-table space!

Pre-drill your tapping holes anywhere and any way you like then switch to the pedestal drill - with long table vertical adjustment and a good spindle (adjustable) travel and a tapping head.

In most cases alignment "by eye" will get you close enough so that when thetap starts the job will move and pretty well self align.

Take your pick of good pedestal drills (up to MT3) etc. - just "click" to checvk the specs:

http://www.machineryhouse.com.au/Bench-Pedestal-Drilling-Machines

TR
02-26-2013, 03:13 AM
When I power tap on the Bridgeport (a 1HP step pulley one), the tap is in a drill chuck and may slip a bit. Usually, it just flows through as I use a higher speed than many and a tapping compound. I do not drill holes oversized to make tapping easier, and the only time I use the spindle brake is at the end of the sequence. Here's a quick video of tapping a 1/2"-13 through hole in 1" thick 1117 CRS:

http://www.youtube.com/watch?v=anR-E2AVUzU&feature=share&list=UUDlpWhxakPMd4fAqCJOzU_g

I have tapping heads but don't use them because it takes to long to crank the table down and back up. Those things take up a lot of spindle-to-table space!

Excellent. I have seen a few operations whereby the setup is critical and the machinist prefers to perform the tapping operation from the one position. I figured in my search for a mill, I'd like to be able to powertap. Your video was excellent. Looks like not all mills are created equal. BTW, how did you reverse the tapping operations ? Just reverse the motor ?

Thanks Tom

darryl
02-26-2013, 03:24 AM
One of the benefits of using a permanent magnet motor. They don't coast for very long.

PixMan
02-26-2013, 07:28 AM
Excellent. I have seen a few operations whereby the setup is critical and the machinist prefers to perform the tapping operation from the one position. I figured in my search for a mill, I'd like to be able to powertap. Your video was excellent. Looks like not all mills are created equal. BTW, how did you reverse the tapping operations ? Just reverse the motor ?

Thanks Tom

Tom,

Thank you. The 3-phase 1HP motor reverses almost instantly, as you see in the video. Yes, that's done simply by switching from forward to reverse without stopping in the center "off" position of the switch. There are many VFD units that also seem to give near-instant reversal. I'm sure others can share and there has been much discussion of that subject here in the past.

I just wanted to illustrate that power tapping is usually done like that. I've never used the brake.

rohart
02-26-2013, 05:29 PM
All right - I'm convinced.

I'm setting my mill's vfd up for quick stop (and reverse) first thing tomorrow.

I do flick from forward to reverse on the vfd that powers my x-feed. I guess the inertia of the powertrain and the gearbox disinclined me from doing it before.

Lathe runs from a converter so I can't do it with that. I'll stick with the brake.