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Thread: Boss 3 head questions, paging Machintek

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    Default Boss 3 head questions, paging Machintek

    Machintek has always been the human encyclopedia of bridgeports, hopefully he can help me again this time, Edited: looks like he hasn't been on in many months, hope all is ok. Maybe someone else has the info, lots have done belt conversions on varispeed heads.

    I have a old Boss 3 (tilt/nod varispeed head) that has been totally retrofitted and brought up to date. I have a VFD running the stock varispeed head which is driving me crazy with the noise especially at 5000 rpms.

    Well, I have had enough ! I ordered a set of poly V pulleys to swap out the varispeed setup. The pulleys are taper lock type

    The question is : Do yu know the shaft sizes for front and rear so I can order the taper lock bushings ahead of time?

    Any idea lwhat the center distance on the shafts is? I would like to order the belt at the same time.

    Last, please confirm that 6000 rpm is ok with the new setup, what about 6500? more? I use a lot of 1/8 and 1/16 endmills and speed is king.

    Thanks much !
    George

    PS 4 pole motor 17xx rpm, 1.722 belt ratio, so at 120hz/3600rpm I should be at 6200 rpm, give or take a bit.

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    Last edited by Sparky_NY; 08-10-2018 at 09:12 PM.


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    Default Re: Boss 3 head questions, paging Machintek

    Quote Originally Posted by Sparky_NY View Post
    Machintek has always been the human encyclopedia of bridgeports, hopefully he can help me again this time, Edited: looks like he hasn't been on in many months, hope all is ok. Maybe someone else has the info, lots have done belt conversions on varispeed heads.

    I have a old Boss 3 (tilt/nod varispeed head) that has been totally retrofitted and brought up to date. I have a VFD running the stock varispeed head which is driving me crazy with the noise especially at 5000 rpms.

    Well, I have had enough ! I ordered a set of poly V pulleys to swap out the varispeed setup. The pulleys are taper lock type

    The question is : Do yu know the shaft sizes for front and rear so I can order the taper lock bushings ahead of time?

    Any idea lwhat the center distance on the shafts is? I would like to order the belt at the same time.

    Last, please confirm that 6000 rpm is ok with the new setup, what about 6500? more? I use a lot of 1/8 and 1/16 endmills and speed is king.

    Thanks much !
    George

    PS 4 pole motor 17xx rpm, 1.722 belt ratio, so at 120hz/3600rpm I should be at 6200 rpm, give or take a bit.
    There are more too it then just adding two pulleys and a belt, if you want those speeds you will have to balance the motor use quality Bearings in the motor and cut the shaft down on the motor, if you are never going to change it back

    The Motor shaft Diameter is 1.1785" there are some with different shaft sizes, so you will have to measure the one you have, there are other Bearings that are under the front drive, that can create noise, as for the front shaft, I have never used the original parts, and custom made new shafts, for the machine builds I used to do, you may be better off replacing the Motor with a Baldor wash down motor which are rated to 6,000 RPM, or similar motor from other manufactures

    The front Bull Gear Shaft is 1.378" but your could be a different size also

    You would be better off to get a speed doubler, or make one to mount on your spindle, so you can run those small cutters, here is one for an idea, they can be more compact than this, there was one available for Bridgeport Mills https://www.tormach.com/store/index....ef=speeder_kit

    Attached Thumbnails Attached Thumbnails Boss 3 head questions,  paging Machintek-bridgeport-head-mod-2-jpg  
    Mactec54


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    Default Re: Boss 3 head questions, paging Machintek

    Great info, thanks so much !l

    I read many threads on the subject here and all the info you posted in them. I was under the impression that 6000 wasn't a big deal and all the extradordiany measures didn't really come into play unless you went above that. I have run mine regularily at 5300 with the varispeed and the vfd without issues except its getting more noisy over the years.

    My motor is a 1740 rpm so at the 6000 speed mentioned it would be spinning around 3600 at the motor.

    Last edited by Sparky_NY; 08-11-2018 at 12:53 PM.


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    Default Re: Boss 3 head questions, paging Machintek

    Quote Originally Posted by Sparky_NY View Post
    Great info, thanks so much !l

    I read many threads on the subject here and all the info you posted in them. I was under the impression that 6000 wasn't a big deal and all the extradordiany measures didn't really come into play unless you went above that. I have run mine regularily at 5300 with the varispeed and the vfd without issues except its getting more noisy over the years.

    My motor is a 1740 rpm so at the 6000 speed mentioned it would be spinning around 3600 at the motor.
    I would not expect your motor to last very long, if not rebuilt 3600 is more than 120Hz which is the max for a motor like this even after it is rebuilt with new Bearing and Balanced, you can not use it above 120Hz

    Some Bridgeport machines had a 2 pole 3480 motor as standard, this was easy to get it to run at 6,000 plus, which I have done on many builds, the varispeed will flog itself to death over the rated 4200 RPM spec for the varispeed so probably why it is making a lot of noise

    Mactec54


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    Default Re: Boss 3 head questions, paging Machintek

    If you have a #30 or #40 taper QC spindle, you could do something like this for high speed.

    I used a Harbor Freight pencil air grinder, and stuffed it into a 5/8 endmill holder. Works great for small diameter endmills and engraving cutters.

    Boss 3 head questions,  paging Machintek-img_0134-jpg

    Ran the air line down through the drawbar hole.

    Boss 3 head questions,  paging Machintek-img_0137-jpg

    Just don't turn the spindle on
    Boss 3 head questions,  paging Machintek-img_0138-jpg

    Boss 3 head questions,  paging Machintek-img_0146-jpg

    I also did the same conversion that you are doing. I started with poly-V pulleys at a 1:1 ratio, and later changed over to a 1.5:1 timing belt drive to get higher speed. The reason I went with a timing belt drive is for rigid tapping because the encoder is on the motor. I am running a 3HP, 4 pole Baldor motor rated at 6000 RPM, but I've never ran it at over 4500 RPM.

    I can't help you with shaft sizes.

    Attached Thumbnails Attached Thumbnails Boss 3 head questions,  paging Machintek-img_0146-jpg   Boss 3 head questions,  paging Machintek-img_0138-jpg   Boss 3 head questions,  paging Machintek-img_0137-jpg   Boss 3 head questions,  paging Machintek-img_0134-jpg  

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Boss 3 head questions, paging Machintek

    Thats a great idea Jim. Unfortunately, the spindle on the qc30 boss on mine isn't hollow. Some cnc's are hollow for a drawbar, some are not.



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    Default Re: Boss 3 head questions, paging Machintek

    Thank you !

    I guess it wouldn't be too hard to make a special holder that was ported for air and port in from the side, below the nut.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Boss 3 head questions, paging Machintek

    Thanks for the info Martec54 ! I am thinking the plan will be to shorten the motor shaft and take it to the local motor shop to have it balanced for higher rpm's. the browning poly vee pulleys I have on the way are balanced. I am pretty sure the original bridgeport motor used quality bearings, I am assuming you are speaking of just replacing them with a fresh set of quality name brand type, the same that is on there now. Back gear will be left intact for low rpm steel hogging. I also plan to ditch the motor cooling fan and go with a electric fan. I should get 6000 spindle rpm at just under 120HZ to the motor with the belt ratio setup in the first post.

    Its worth noting also that this is a hobby machine so it will never see 8 hr a day type usage and top rpms will only be for those rare occasions with tiny endmills.



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    Default Re: Boss 3 head questions, paging Machintek

    Quote Originally Posted by Sparky_NY View Post
    Thanks for the info Martec54 ! I am thinking the plan will be to shorten the motor shaft and take it to the local motor shop to have it balanced for higher rpm's. the browning poly vee pulleys I have on the way are balanced. I am pretty sure the original bridgeport motor used quality bearings, I am assuming you are speaking of just replacing them with a fresh set of quality name brand type, the same that is on there now. Back gear will be left intact for low rpm steel hogging. I also plan to ditch the motor cooling fan and go with a electric fan. I should get 6000 spindle rpm at just under 120HZ to the motor with the belt ratio setup in the first post.

    Its worth noting also that this is a hobby machine so it will never see 8 hr a day type usage and top rpms will only be for those rare occasions with tiny endmills.
    The standard Bearing are just a basic ABEC 3 bearing, I always replaced them with a NSK sealed bearings ABEC 5

    You will need to slot the Motor mounting holes for adjustment, yes a simple fan on top is all that is needed

    Don't cut the motor shaft until you have done an install to know how much you can take off, these shafts are case hardened so the first part of the cut is hard to machine if you don't have good tooling for your lathe

    Mactec54


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    Default Re: Boss 3 head questions, paging Machintek

    Any idea what the front shaft to motor shaft distance is? I would like to have the belt on hand when I start. I might get more than one length belt to be on the safe side anyway.



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    Default Re: Boss 3 head questions, paging Machintek

    All done, worked out great. The motor armature required quite a bit of balancing which was surprising. Maybe BP only static balanced them back in the day. Before balancing I mounted the new pulley on the motor (no belt) and there was a lot of vibration. No balancing was needed on the pulley by the motor shop, only the armature. I put new quality bearings in everything up top except the actual spindle.

    Its very smooth and quiet now. I have run it as high as 6500 with no noticeable concerns but will self impose a limit of 6000 until I get some hours on it.



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    Default Re: Boss 3 head questions, paging Machintek

    Quote Originally Posted by Sparky_NY View Post
    All done, worked out great. The motor armature required quite a bit of balancing which was surprising. Maybe BP only static balanced them back in the day. Before balancing I mounted the new pulley on the motor (no belt) and there was a lot of vibration. No balancing was needed on the pulley by the motor shop, only the armature. I put new quality bearings in everything up top except the actual spindle.

    Its very smooth and quiet now. I have run it as high as 6500 with no noticeable concerns but will self impose a limit of 6000 until I get some hours on it.
    Yes the Rotors are only factory balanced for low speed 1740 RPM, that is why it is important to balance all moving parts, spindle is normally fine even at 12,5000 RPM I have run them

    Mactec54


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    Quote Originally Posted by Sparky_NY View Post
    Machintek has always been the human encyclopedia of bridgeports, hopefully he can help me again this time, Edited: looks like he hasn't been on in many months, hope all is ok. Maybe someone else has the info, lots have done belt conversions on varispeed heads.

    I have a old Boss 3 (tilt/nod varispeed head) that has been totally retrofitted and brought up to date. I have a VFD running the stock varispeed head which is driving me crazy with the noise especially at 5000 rpms.

    Well, I have had enough ! I ordered a set of poly V pulleys to swap out the varispeed setup. The pulleys are taper lock type

    The question is : Do yu know the shaft sizes for front and rear so I can order the taper lock bushings ahead of time?

    Any idea lwhat the center distance on the shafts is? I would like to order the belt at the same time.

    Last, please confirm that 6000 rpm is ok with the new setup, what about 6500? more? I use a lot of 1/8 and 1/16 endmills and speed is king.

    Thanks much !
    George

    PS 4 pole motor 17xx rpm, 1.722 belt ratio, so at 120hz/3600rpm I should be at 6200 rpm, give or take a bit.
    Please, if anyone can help. I have a BP Boss5 that flashes 60001 at start up and then no digits at control it wont recognize any types info. All axis work and so does spindle forward and backwards. I do not have the maintenance manual for this machine and I'm at a loss. Thanks bob



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