Bridgeport Series 1 J2J head 2hp motor shaft

I have just acquired the above machine FOC. However the motor shaft where the snap ring fits to hold everything in place is worn. Can I just have the groove turned on a lathe and fit a new circlip or do I need a new shaft which only comes as an assembly with the rotor attached and is stupid money.

There is a grub screw in the side of the pulley to keep it on the shaft mine had no cirt clip on it this last year and trudging along fine. Also There is an insurance bolt on the end of the shaft should it poo the bed.if yours not there drill tap install boom.

If the grove is worn, how can remachining it help? It is more usual for the shaft nearer the motor to be worn..

The late John Stevenson, a forum member here, used to repair these shafts as part of his business because of the "stupid money". Does not help you of course.

Is it that badly worn as to be unusable? The retaining ring (circlip) It merely stops the Spring Collar from slipping off.

So I’ve only just got this machine and had to dismantle it to get t into storage. When I took the motor off the spring assembly fell off as the circlip had pretty much worn away. Now, I haven’t had much chance to look at it closely so please don’t take it as gospel I’m just assuming it’s popped out of its groove. I wondered if making the groove it sits in marginally deeper would help with retaining the clip.

In principle there is no reason why the whole snap ring groove area couldn't be turned down and a suitable washer fitted below the new circlip to hold everything in place. Need to turn down a bit further to accommodate the washer and you will end up with a step on the shaft but as it merely holds the spring assembly on I hardly think the small difference in length is worrisome.

Given the known wear issues with the Varispeed arrangement maybe its worth considering dumping the whole lot and going for a VFD drive with a single Vee or multigroove belt. I've always felt the a two speed belt arrangement would be required but its reported that a single speed generally performs well enough. The Varispeed drive is rather inefficient, as demonstrated by the raised temperature of the alloy case after running for several minutes. It is said that reclaiming most of this wasted power covers the deficiencies of trying to run on a single speed using a VFD.

Clive

So what would I need to do to carry out this modification then? Is there a post or thread that explains the process and parts required.

Mark

If you PM me your E-mail I can send you some un-edited text from a thread on another forum relating experiences in converting a Varispeed Bridgeport to VFD with single speed belt drive. The source is reliable and the conversion clearly worked well.

Summarising

The standard Bridgeport motor works fine with a VFD but this machine had single phase motor fitted so a new 1.5 Kw / 2 hp motor was used for the conversion.

He used an Optidrive sensorless vector VFD box to control it. All the Varispeed mechanism was removed. Drive was direct to the spindle via L section toothed belt giving 0.75 - 1 speed reduction between motor and spindle. The Optidrive VFD proved very effective at holding power up at lower rpm. So much so that he later considered that a 1 - 1 drive ratio between motor and spindle might well have been satisfactory.

He used L (3/8 pitch) toothed belt drive primarily because suitable taperloc fitting pulleys were to hand. Ordinary Vee or multigroove would have worked fine and, possibly, been a little less sensitive to alignment.

I plan to do a similar conversion to mine as the head has become noisy.

I have fitted a VFD drive to a step pulley head mill for a friend which works very well. He chooses to divide jobs into high speed and low speed ones finding that the speed reduction on the lower geared of the two middle pulley settings gives enough overlap between VFD control and nominal backgear speed ranges that he almost never needs backgear. Obviously with a single speed belt you won't have enough overlap to do that so and will need to use backgear in the normal way.

Clive

Edited By Clive Foster on 12/06/2020 17:31:45

Edited By Clive Foster on 12/06/2020 17:33:19

Clive, Iv sent you a pm , as I’m also interested in the info.