Twenty five years ago I bought a Bridgeport mill that came with a partial 2J vari-drive head (missing motor & vari pulleys).? I never found a reasonable priced motor back then and ended up buying a step belt J head to complete the mill - the 2J head went into storage in the garage attic - and still there.? ?Fast forward to my current Bport mill - also a?step belt with a 1.5 hp (2-pole?, 3475 rpm motor, stock US Electric motor) that I run on a static phase converter.? With the 3475 rpm motor, spindle speeds range from 160 to 5440 rpm.? ?Last fall I got (3) Bport vari-drive motors at a local auction for a modest amount of money.? ? One of the three motors was fried and I sold it to a Bport rebuilder as a core.? That leaves me with a 1.5 hp and a 2 hp 2J motor.? ?I suddenly have mill head options.? ? BTW, I'm a bit lazy and typically use the mill as if it only had 2 speeds (Hi-Low, though I did have a reason to go up to the 5440 rpm belt setting last week) - this is for hobby use, I do not have to be efficient?with my time or my tooling.??

Option 1: is to keep the step belt and get a VFD (with a brake resistor).? ?This was my intent prior to acquiring the 2J head motors last fall.? ?I would also complete assemble the 2J head and sell it and also sell off the extra unused 2J motor for more tooling monies.

Option 2: is to refresh the 2J head and install one of the 2J motors for use on my mill & maybe buy a VFD, sell off the remaining 2J motor and sell off the step belt head.? ?I have collected motor vari-drive pulleys for both 1.5 and 2 hp configurations.? ?I'm thinking that there is no reason to use the 1.5 hp motor if I have a 2 hp motor available.? ? Am I correct in understanding that the only difference between a 1.5 hp and 2 hp Bport head is the motor and the motor related pulley asm - all other parts being the same in the head?? I have a Textron vintage Bport manual but it only shows the 1.5 hp 2J head so I can not cross check P/Ns.

Your thoughts?

I've maybe moved the belts twice in the 15 or so years I've had my 1J- but I adjust the vfd speed frequently and occasionally drop into backgear.??? Never have maxed out the 1J but perhaps I don't push the machine super hard.?? If I had to get another mill I'd immediately go for a vfd solution unless it had a really gonzo transmission that afforded a similar range of adjustment.?? A friend of mine had a nice Kempsmith universal horizontal mill that I lusted after- a trans producting at least 8 speeds on the spindle not counting the lineshaft drive cone pulley IIRC- that level of fancy might be a reasonable substitute.

A full-on 2J adjustable head would maybe be fine... but in the end I prefer the simplicity of a motor & cone pulley and vfd.

Greg

On 3/28/2023 7:52 PM, aribert2 wrote:

Twenty five years ago I bought a Bridgeport mill that came with a partial 2J vari-drive head (missing motor & vari pulleys).? I never found a reasonable priced motor back then and ended up buying a step belt J head to complete the mill - the 2J head went into storage in the garage attic - and still there.? ?Fast forward to my current Bport mill - also a?step belt with a 1.5 hp (2-pole?, 3475 rpm motor, stock US Electric motor) that I run on a static phase converter.? With the 3475 rpm motor, spindle speeds range from 160 to 5440 rpm.? ?Last fall I got (3) Bport vari-drive motors at a local auction for a modest amount of money.? ? One of the three motors was fried and I sold it to a Bport rebuilder as a core.? That leaves me with a 1.5 hp and a 2 hp 2J motor.? ?I suddenly have mill head options.? ? BTW, I'm a bit lazy and typically use the mill as if it only had 2 speeds (Hi-Low, though I did have a reason to go up to the 5440 rpm belt setting last week) - this is for hobby use, I do not have to be efficient?with my time or my tooling.??

Option 1: is to keep the step belt and get a VFD (with a brake resistor).? ?This was my intent prior to acquiring the 2J head motors last fall.? ?I would also complete assemble the 2J head and sell it and also sell off the extra unused 2J motor for more tooling monies.

Option 2: is to refresh the 2J head and install one of the 2J motors for use on my mill & maybe buy a VFD, sell off the remaining 2J motor and sell off the step belt head.? ?I have collected motor vari-drive pulleys for both 1.5 and 2 hp configurations.? ?I'm thinking that there is no reason to use the 1.5 hp motor if I have a 2 hp motor available.? ? Am I correct in understanding that the only difference between a 1.5 hp and 2 hp Bport head is the motor and the motor related pulley asm - all other parts being the same in the head?? I have a Textron vintage Bport manual but it only shows the 1.5 hp 2J head so I can not cross check P/Ns.

Your thoughts?