Bridgeport M head Cutting expectations
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  1. #1
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    Default Bridgeport M head Cutting expectations

    I recently picked up a Bridgeport M head in really nice shape which came with the standard 1/2 hp motor,, iím new to all this but it seems like it just doesnít have that much power when making a cut .. I am not aware of just how deep of a cut I can make letís say with a half inch for fluted end mill but if I tried to remove 1/8 of an inch Iíve material in even aluminum I have to travel extremely slow just to keep it going or just Boggs down and comes to a stop ,, I would think that it would be a little more productive than that rather than having to just hardly nip away at it at super slow speed one 16 of an inch deep every pass I take.. I thought maybe the motor was worn out and I took that in and have them go through it and they said thereís nothing wrong with that at all other then the bearings or slightly worn which I had replaced but other than that they say itís good to go no problem whatsoever with the motor .. and like I said this is when cutting aluminum I can imagine how much worse the situation would be if I were cutting steel ... is this to be expected I know the other Bridgeport machine is like the J head has more power for motors with the M head being the least powerful at 1/2 hp but itís hard to believe that this machine help us get through World War II at the rate it puts out ... does this sound about right ,,is this to be expected using a brand new solid carbide cutting tool..??? Any input on this would be greatly appreciated thank you ...

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    Simple things, but how sharp is your end-mill? Is it the motor that's bogging down or is the belt slipping.

    You are correct in that it's a "light duty" machine, but also remember it was made to be a "details" machine to catch all the little operations that the heavy duty horizontal mills couldn't do. It wasn't until later that they realized how versatile a high speed vertical spindle was with the right horse power and rigidity.

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    i’m new to all this
    Pardon me, but do you know if the rotation is correct? End mills don't do very well running "backwards"

    (In J.C. Penny's years and years ago I watched two young employees trying to drill holes in some display they were putting up. One would try - and then the other - no dice. I leaned over, got their attention and quietly told them they were running the drill bit backwards - magically, they were able to make instant holes afterwards)
    Last edited by johnoder; 11-09-2018 at 10:46 AM.

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    Something does not sound right. Is the motor connected for the right voltage? Once upon a time, I had a 1/2-HP M-head on a Clausing 8520 base, and could throw chips around from a 1/2" end mill pretty nicely without bogging down the motor. I was more limited by machine rigidity than motor horsepower.

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    You said you recently picked it up... perhaps the motor is dying and thats why it was being gotten rid of by the old owner?

    Jon

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    Quote Originally Posted by Bellaru433 View Post
    I recently picked up a Bridgeport M head in really nice shape which came with the standard 1/2 hp motor,, i’m new to all this but it seems like it just doesn’t have that much power when making a cut .. I am not aware of just how deep of a cut I can make let’s say with a half inch for fluted end mill but if I tried to remove 1/8 of an inch I’ve material in even aluminum I have to travel extremely slow just to keep it going or just Boggs down and comes to a stop ,, I would think that it would be a little more productive than that rather than having to just hardly nip away at it at super slow speed one 16 of an inch deep every pass I take.. I thought maybe the motor was worn out and I took that in and have them go through it and they said there’s nothing wrong with that at all other then the bearings or slightly worn which I had replaced but other than that they say it’s good to go no problem whatsoever with the motor .. and like I said this is when cutting aluminum I can imagine how much worse the situation would be if I were cutting steel ... is this to be expected I know the other Bridgeport machine is like the J head has more power for motors with the M head being the least powerful at 1/2 hp but it’s hard to believe that this machine help us get through World War II at the rate it puts out ... does this sound about right ,,is this to be expected using a brand new solid carbide cutting tool..??? Any input on this would be greatly appreciated thank you ...
    As you stated you're new to all this, I suggest a couple of factors to consider. HSS or carbide end mills can be ruined quickly if you do not use the correct cutting speeds. Also aluminum can be aggravating as it may stick to the flutes of the cutter and cause issues even using carbide.

    Verify that you are using a sharp cutter in correct rotation at the correct cutting speed for the material. An M-Head should have no problem cutting 1/8 deep in soft materials. It will do better with 0.060", given the 1/2 HP motor. I have a 3/4 HP DC motor on mine. Also consider using cutting oil or coolant when taking deep cuts in aluminum.

    There is a wealth of info on speeds and feeds here on PM. Hope this helps.

    Best Regards,
    Bob

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    I have an "M" head on one of my K&T Horizontals with #2 Morse taper spindle.. Mine would easily make the cut you are trying to make.. It may even do it in steel with a very sharp end mill and plenty of oil flowing on the cutter...As others have stated, make sure your cutter is sharp, the direction of rotation is correct, the belt is not slipping, the cutter is running the correct speed, the motor is running on the correct voltage...I also have a Milwaukee Midget Mill but I much prefer the Bridgeport "M" head.. Ramsay 1

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    You might try getting someone who is experienced just to demonstrate how its done. Or possibly enroll in some sort of entry level machine shop class. There you will meet people and can get help. And you will learn more at a faster rate. Barring that, see what you can learn from the internet, youtube, etc. And get a good machine shop textbook. I got this one back in the early 1990's when I got started as a newb. And still occasionally refer to it. There is a section on cutting speeds and feeds that might be helpful for the situation you wrote about that you are having.

    I linked the edition I got from the 1990's. You could just as well use an earlier or later edition. But you don't need the latest version for what you are doing.

    Machine Tool Practices 135418488 | eBay

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    1/2 hp motor with belt drive maybe 50% hp available at spindle. use low gear maybe 30% hp available at spindle of 1/6hp
    .
    steel need 1hp to turn cubic inch per minute into chips. so you can machine 1/4 to 1/6 of a cubic inch per minute into chips maximum.
    .
    sometimes a tight belt or thick gear oil can absorb a lot of hp. oil gets thicker when cold. often cold machine wont even turn spindle at full rpm

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    Yes I checked everything the rotation is right,,,the end mill is brand new .. it doesnít seem like the belt is slipping and I actually brought the motor inn and have them rebuild it thinking it was worn out and they said thereís nothing wrong with that other than the bearings were slightly worn which they replaced..Like I said it does have that variable speed device on there that enables me to speed up or lower the RPMs by pushing the up or down button and the guy at the motor repair place said itís also a converter that changes it from three phase power to single phase power and thatís why the motor starts up slowly and builds up speed rather than just kicking on instantly. like I said it does have that variable speed device on there that enables me to speed up or lower the RPMs by pushing the up or down button and the guy at the motor repair play said itís also a converter that changes it from three phase power to single phase power and thatís why the motor starts up slowly and Bills up speed rather than just kicking on instantly . like I said Iím new to this and thatís why always ask IW professionals out there for help it just seems that I should be able to make at least an eighth of an inch cut in aluminum at a fairly reasonable travel speed without the motor bogging down in coming to a complete stop ...???

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    What is the variable speed device? Sounds like a VFD. Post pics or at least make and model. It could need adjustments on its settings IF it is VFD.

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    Quote Originally Posted by Rob F. View Post
    What is the variable speed device? Sounds like a VFD. Post pics or at least make and model. It could need adjustments on its settings IF it is VFD.
    Agree with Rob F. Sounds like VFD is not set up right. Most likely scenario. OTH If it's Static Phase Converter, then it wont produce full power for the motor. Perhaps as little as 60%. Please post pics of the variable speed device you described.

    Best Regards,
    Bob

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    People new to using a VFD often do not know the torque or power versus frequency relationship. Normally, the torque will be constant from the lowest practical frequency up to 60 Hz, and then the power will be constant from 60 Hz up.

    What that means is that running a 1/2 HP motor at 30 Hz will cut the power in half to 1/4 HP. Running at 90 Hz, you still have 1/2 HP. It is usually best to run the motor at 60 or more HZ and use the step pulleys to get the spindle speed you need. But keep in mind that old motors may not like to be run at much over 60 HZ. I usually stop at 90 or 120 HZ, but that is with a modern Baldor motor rated at 1150 RPM at 60 Hz. Such a motor can easily run at 2350 RPM (120 Hz), since the same bearings and shaft would be used in a similar motor rated 3450 RPM at 60 Hz.

    Similarly, people new to milling may not realize the proper RPM for a 1/2" carbide end mill cutting aluminum. I did not look it up, but the quick answer is FAST. Hand feeding such a cutter with the spindle running way too slow would certainly stall the spindle, either slipping the belt or stalling the motor.

    Larry


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