Just bought a Brown & Sharpe 618 Micromaster. Small issue

Okay a couple small issues. #1 When the head feeds back away from me it doesn't always change direction when I flip the lever. It has also stopped half way across my part. I flip the lever up and then back down and it goes again. It doesn't seem like the lever is popping out of feed. Its still down all the way when the feed stops. What could be causing this?

#2 It has a permanent magnet chuck. I'm not sure when the last time this thing was used. The lever was fairly stiff when I went to use it. It seems no matter what way I flip the lever. The magnet doesn't disengage. I have a heck of a time getting my parts off of it. I don't know how they work inside. Is it possible that there is rust inside and when I flip the lever the magnet doesn't release?

#3 I bought this grinder to mainly do one job. I make these tools from M2 64Rc that are about 2" wide and 5" long. I finish grind them after heat treat. I thought I could take .001" per pass. One forward and one back. It seems to be really bogging the wheel down. I ended up going .0005" per pass but now it takes twice as long. I put 4 tools on the chuck at once with space between them. Also the tools aren't solid. They have holes in them and a cut out. The wheel is a 7"x 1/2" Radiac 8BP46-G800-VOS ceramic wheel. I run coolant to keep it cool. I figured either my wheel is wrong or the grinder just doesn't have to power to do what I'm asking it to do. My breaker is 20 amp and it tripped after about 15 mins of grinding. Guess I'll need to upgrade that too. Any thoughts here? Should I try a different wheel? Or am I pushing it too hard?

#2 It has a permanent magnet chuck. I'm not sure when the last time this thing was used. The lever was fairly stiff when I went to use it. It seems no matter what way I flip the lever. The magnet doesn't disengage. I have a heck of a time getting my parts off of it. I don't know how they work inside. Is it possible that there is rust inside and when I flip the lever the magnet doesn't release?

********************************************************************************

Do a search on on this forum for " Magnetic chuck rebuild".

The short answer is that your chuck is filled with 90 wt gear oil and the cam linkage that pries apart and then slides the magnet assembly inside the chuck is worn out. If this is a Walker chuck you can buy a linkage repair kit. You can also make the parts yourself if it is from another manufacturer.

The Brown and Sharpe 618 operation and maintenance manual suggests purging the cross feed cylinder of air to cure erratic motion. If that does not work it suggests checking the ways for adequate lubrication, checking the piston rod for damage, inspecting the piston seal for leakage, and verifying that there are no leaks in the hydraulic lines.

You did not mention in your post the procedure you used to dress the grinding wheel or the amount of cross feed. You also did not specify which grinding spindle is installed. The o-ring drive spindle is rated at 1 hp. The direct drive spindle could be either 1 1/2 or 2 hp.


Your 20 amp 3 phase circuit breaker is supplying roughly 6 kw to the machine. The grinder has a 1 hp hydraulic pump and at most a 2 hp spindle. The motors at peak load will use 3 kw of power. Why is your circuit breaker tripping?
Robert

Thank you for helping me. I will check those things and the thread about rebuilding the chuck. The grinder didn't come with a manual. I will look online and see if I can find a copy to purchase.

My spindle is the O ring drive spindle. I have a 1/4" shank diamond dresser in a little holder that I place on the magnet. I take .001" at a time and slowly crank the dresser across the wheel. I offset the dresser to the wheel so the diamond is making contact with the wheel. I take .001" forward and .001" back until the wheel cleans up all the way across. I am feeding about 1/8" for the cross feed.

As far as the circuit breaker goes. Im running 3 phase 220v. The breaker doesn't appear to be tripped like you would normally see with the lever kicked out of position. I reset it anyway and the grinder comes back on so I assumed that was it. Maybe the breaker is bad. The grinder seems to run fine. It has a coolant pump hard wired in also that kicks on with the spindle.

With whatever else is going on, try dressing the wheel far coarser/faster. It will cut more freely with less power, and with little sacrifice in surface finish.

Am I wrong if I guess that the grinder has been rewired from 440V?
I suspect that the motors have been rewired to be used at 220V, but the heaters haven't been changed and they trip at half the current they're supposed to trip at 220V.
But I could be completely wrong.

Paolo

Conrad Hoffman said:

With whatever else is going on, try dressing the wheel far coarser/faster. It will cut more freely with less power, and with little sacrifice in surface finish.

Click to expand...

I will give that a try. Thank you.

Paolo_MD said:

Am I wrong if I guess that the grinder has been rewired from 440V?
I suspect that the motors have been rewired to be used at 220V, but the heaters haven't been changed and they trip at half the current they're supposed to trip at 220V.
But I could be completely wrong.

Paolo

Click to expand...

Would resetting the main breaker in the breaker box allow the machine to restart again if that was the problem? I had an electrician wire the machine up. He may have just checked the motor was capable of 220v and that was it. I don’t know. I’m not familiar with the heaters you are talking about.

A.Delaney said:

Would resetting the main breaker in the breaker box allow the machine to restart again if that was the problem? I had an electrician wire the machine up. He may have just checked the motor was capable of 220v and that was it. I don’t know. I’m not familiar with the heaters you are talking about.

Click to expand...

**********************************************************88
The grinder electrical cabinet has two or maybe three sets of motor starters. Each starter consists of a 3 phase relay and a 3 phase current overload device. The overload device is there to protect the motor from burning out if it is stalled. The overload device is a spring loaded mechanism with a heater block for each phase.

The heater's temperature is proportional to the current flowing through the wire. When the heater reaches its rated current the heat generated causes the spring loaded mechanism to release and break the electrical connection. The overload device must be reset manually by pushing in a button which forces the latch back to the closed position.

The fact that the grinder starters are not tripping suggests that the problem is that your circuit breaker feeding the grinder is bad. The circuit breakers in your wall panel have a design life of about 100 trip cycles. The latch mechanism wears out and can no longer hold the spring back. The latch is released by a electrical solenoid pulling the pawl back from the latch. As the latch wears out it takes less force and a corresponding reduction in current to pull the pawl back.

Robert

Here find the manual for free download
http://vintagemachinery.org/pubs/2185/6029.pdf
Sounds like you are saying the cross feed stops mid part, Check to see of hydraulic motor is stopping, oil is full and as Robert said some times you have to travel full cross travel back and forth to bleed lines.

How does the cross travel feel doing so manually..That machine travels the whole casting so you need to be sure the bed ways are getting proper oil..

Wheel selection along with being sure you have a full count of belts..I have run that machine (a larger micromaster) on material it would hardy cut for slipping belts. Think it was cpm t-14 or the like. With having an Ok surface finish you may wish to go to a courser wheel. What wheel are you using? ....And be sure you have turned the diamond to fresh facet. Going softer wheel for harder stock is the norm but sometimes softer just will not hold up to super-hard material and acts like you are trying to grind carbide with an aluminum oxide wheel..Sometimes the harder wheel may need more sfpm , a smaller wheel area contact or a different grit material.....

You stock should not be a problem but sometimes with a stalling spindle you may go to a softer wheel, a courser grit, more often dress, slower long travel, one side only feed(often on the grind side) and like someone said be sure the motor is getting the correct voltage.

I once stuck a chuck in a bucket of oil the free up the magnets..it worked,.

You- tube on chucks https://www.youtube.com/watch?v=cG-01vY36W0

The manual on page E6 states that the hydraulic system is purged of air by running the grinder for an hour with the table throttle in the off position. The hydraulic pressure should be 25 psi. The normal operating pressure is 120 psi.

On page D2 it recommends running the table at the highest speed with the trip dogs set far apart. I suspect the same procedure applies to the cross feed.
It may be time to replace the return line hydraulic filter. A clogged filter may be part of the problem.


According to the manual the grinder is designed for a step cross feed only. The cross feed should be done while the grinding wheel is off the work. The table left and right hand stops need to be set far enough away from the work to allow the complete cross feed to take place. If the feed is inconsistent or delayed the feed will occur during the grind. The inconsistent cross feed motion may be part of the reason why the wheel is slowing down.

Robert

The grinder should have 3 cross feed options, incremental feed, rapid, and wheel dress. In incremental, the head moves forward or back at each table reversal. In rapid or dress mode, the table does not cycle. The table speed lever is used to control the speed of the cross feed, which is continuous.

The cross feed is done with a simple hydraulic cylinder. Pressure is applied to the circuit and it lifts the cross feed nut off the screw. Then it supplies oil to the cylinder. Running it front to back a few times in rapid should be sufficient to bleed out any air.

These grinders tend to have issues with the cross feed nut sticking. It's spring loaded and raised by hydraulics. If the machines sit too long, the nut get sticky. Usually you can get them working by cycling from auto to manual cross feed a few times.

Check the linkages from the levers to the actual control valve. It's vert common for the set screws and pins to come out or work loose. The actual valves are very hardy and are rarely the cause of the problem.

Robert R said:

**********************************************************88
The grinder electrical cabinet has two or maybe three sets of motor starters. Each starter consists of a 3 phase relay and a 3 phase current overload device. The overload device is there to protect the motor from burning out if it is stalled. The overload device is a spring loaded mechanism with a heater block for each phase.

The heater's temperature is proportional to the current flowing through the wire. When the heater reaches its rated current the heat generated causes the spring loaded mechanism to release and break the electrical connection. The overload device must be reset manually by pushing in a button which forces the latch back to the closed position.

The fact that the grinder starters are not tripping suggests that the problem is that your circuit breaker feeding the grinder is bad. The circuit breakers in your wall panel have a design life of about 100 trip cycles. The latch mechanism wears out and can no longer hold the spring back. The latch is released by a electrical solenoid pulling the pawl back from the latch. As the latch wears out it takes less force and a corresponding reduction in current to pull the pawl back.

Robert

Click to expand...

I understand now. Thanks for the detailed explanation. I’ll start with replacing the main breaker and go from there.

michiganbuck said:

Here find the manual for free download
http://vintagemachinery.org/pubs/2185/6029.pdf
Sounds like you are saying the cross feed stops mid part, Check to see of hydraulic motor is stopping, oil is full and as Robert said some times you have to travel full cross travel back and forth to bleed lines.

How does the cross travel feel doing so manually..That machine travels the whole casting so you need to be sure the bed ways are getting proper oil..

Wheel selection along with being sure you have a full count of belts..I have run that machine (a larger micromaster) on material it would hardy cut for slipping belts. Think it was cpm t-14 or the like. With having an Ok surface finish you may wish to go to a courser wheel. What wheel are you using? ....And be sure you have turned the diamond to fresh facet. Going softer wheel for harder stock is the norm but sometimes softer just will not hold up to super-hard material and acts like you are trying to grind carbide with an aluminum oxide wheel..Sometimes the harder wheel may need more sfpm , a smaller wheel area contact or a different grit material.....

You stock should not be a problem but sometimes with a stalling spindle you may go to a softer wheel, a courser grit, more often dress, slower long travel, one side only feed(often on the grind side) and like someone said be sure the motor is getting the correct voltage.

I once stuck a chuck in a bucket of oil the free up the magnets..it worked,.

You- tube on chucks https://www.youtube.com/watch?v=cG-01vY36W0

Click to expand...

The cross feed has stopped mid part a couple times, but it’s mainly when I’m at the far back of the travel and switching directions. Once the wheel is past the chuck in the back. I flip the lever but the cross feed doesn’t just stops. I have no feed and the hand wheel is not engaged. I have nothing. I flip the lever up and back down a couple times and then it goes. Everything feels smooth cranking the hand wheels. Also with limits. I am traveling off the chuck in all 4 directions. I will check the ways for oil.

The wheel I’m using is a radiac ceramic 46 grit G hardness vos bond. I was reading the manual in the link you posted and it leads me to believe I may need an aluminum oxide wheel for high speed steel. I thought for sure a G hardness would break down easily enough to do the job.

What do you mean often on the grind side?

Robert R said:

The manual on page E6 states that the hydraulic system is purged of air by running the grinder for an hour with the table throttle in the off position. The hydraulic pressure should be 25 psi. The normal operating pressure is 120 psi.

On page D2 it recommends running the table at the highest speed with the trip dogs set far apart. I suspect the same procedure applies to the cross feed.
It may be time to replace the return line hydraulic filter. A clogged filter may be part of the problem.


According to the manual the grinder is designed for a step cross feed only. The cross feed should be done while the grinding wheel is off the work. The table left and right hand stops need to be set far enough away from the work to allow the complete cross feed to take place. If the feed is inconsistent or delayed the feed will occur during the grind. The inconsistent cross feed motion may be part of the reason why the wheel is slowing down.

Robert

Click to expand...

ewlsey said:

The grinder should have 3 cross feed options, incremental feed, rapid, and wheel dress. In incremental, the head moves forward or back at each table reversal. In rapid or dress mode, the table does not cycle. The table speed lever is used to control the speed of the cross feed, which is continuous.

The cross feed is done with a simple hydraulic cylinder. Pressure is applied to the circuit and it lifts the cross feed nut off the screw. Then it supplies oil to the cylinder. Running it front to back a few times in rapid should be sufficient to bleed out any air.

These grinders tend to have issues with the cross feed nut sticking. It's spring loaded and raised by hydraulics. If the machines sit too long, the nut get sticky. Usually you can get them working by cycling from auto to manual cross feed a few times.

Check the linkages from the levers to the actual control valve. It's vert common for the set screws and pins to come out or work loose. The actual valves are very hardy and are rarely the cause of the problem.

Click to expand...

Thanks guys. I’ll get this stuff checked out along with the oil filter and run it some more. I know it sat for a few years at least. It might just need some air bled out as you say. Also the wheel is off the work when the cross feed steps over. The last shop I worked at had a DoAll grinder. I would occasionally use that for jobs and I never had a problem. It seemed like anything put in there would grind fine. I’d just dress the wheel and go. I’m hoping to get this grinder to run that good.

Seems you biggest problem is mechanical or electrical not the wheel. I’m not the machine repair guy so others can give better advice there.

I like aluminum oxide for material such as you are grinding. But ceramic is ok also. G is pretty soft so should break down easily, perhaps too much so causing more wheel use.. Possible that wheel is Ok if giving needed surface finish and not burning the part. If the wheel speed is stalling you can increase the over travel at the ends a little to give spindle a chance to regain full speed. likely you can use it up.

Might mark the wheel pulleys and see if the belts at letting the spindle slip. Might clean the pulleys with auto carb cleaner. It may melt paint so take care with that to only get on the pulleys. New belts may help. Don’t know if you can add a couple extra belts..Yes they would be stacking on the pulley so may cause a problem (and more side pressure on the bearing).

Chasing wheels can be costly. 46 K is my normal starting wheel then go to change hardness and or grit size. Not needing super finish a 36 k AO can be good for some work..Burning, stalling and wheel wear are the cause to seek a different wheel. Wheel break down and frequent need to dress are the wheel wear problems. Ceramic is a harder grit and AO has sharper facets IMHO..

michiganbuck said:

Here find the manual for free download
http://vintagemachinery.org/pubs/2185/6029.pdf
Sounds like you are saying the cross feed stops mid part, Check to see of hydraulic motor is stopping, oil is full and as Robert said some times you have to travel full cross travel back and forth to bleed lines.

How does the cross travel feel doing so manually..That machine travels the whole casting so you need to be sure the bed ways are getting proper oil..

Wheel selection along with being sure you have a full count of belts..I have run that machine (a larger micromaster) on material it would hardy cut for slipping belts. Think it was cpm t-14 or the like. With having an Ok surface finish you may wish to go to a courser wheel. What wheel are you using? ....And be sure you have turned the diamond to fresh facet. Going softer wheel for harder stock is the norm but sometimes softer just will not hold up to super-hard material and acts like you are trying to grind carbide with an aluminum oxide wheel..Sometimes the harder wheel may need more sfpm , a smaller wheel area contact or a different grit material.....

You stock should not be a problem but sometimes with a stalling spindle you may go to a softer wheel, a courser grit, more often dress, slower long travel, one side only feed(often on the grind side) and like someone said be sure the motor is getting the correct voltage.

I once stuck a chuck in a bucket of oil the free up the magnets..it worked,.

You- tube on chucks https://www.youtube.com/watch?v=cG-01vY36W0

Click to expand...

you may also want this manual, just in case things need to be fixed

http://vintagemachinery.org/pubs/2185/16566.pdf

dee
;-D

Has anybody used a CBN wheel? I’m wondering if that would be the way to go with hardened high speed steal.

A.Delaney said:

Has anybody used a CBN wheel? I’m wondering if that would be the way to go with hardened high speed steal.

Click to expand...

This is a new topic. Please start a new thread rather than attach it to the Brown and Sharpe discussion. I suspect that your question should be "What grinding wheel design consumes the least energy per cubic inch of metal removed"

Robert

Okay I marked the belt and pulley. I made several passes and this is what I saw. This leads me to believe the belt is slipping however is it possible the pulleys aren't identical? That after thousands of rotations the marks wouldn't line up anyway?

Never mind. I answered my own question. When turning the pulley by hand the marks don't stay in the same spot. That test does not show whether the belt is slipping or not.

I did notice something else though grinding without coolant. If the cross feed is feeding away from me taking a cut of .0004". When it reaches the other side I lower the spindle .0004" and kick the cross feed on to come back towards me. It doesn't start cutting until after I am about an inch across the part. Then it will start to cut. I have since only been taking cuts from one direction.