06-11-2013, 08:55 PM
Hi,
WOW; I think I've caught up a bit at least can have a breather after three weeks solid restoring/upgrading this Graduate.
I have the Graduate running through the controls I removed from the Jubilee which are mounted on the wall behind the lathe but I am about to add additional wiring allowing me to use the original start/stop buttons. I've never had the need previously to understand how relays worked; the relays I've used and wired up have been motor contactors supplied with connection diagrams.
I tried wiring the original start/stop controls and at first couldn't understand why the lathe would only run if I held in the start button and it stopped as soon as the button was released?
I had installed a "latching" button on the Jubilee and this single button controlled both start and stop; I had also added an emergency stop to the Jubilee this too being latching.
I want the Graduate buttons to work correctly neither of them are latching; the start button is the standard momentary push to make and the stop button is push to break. The outcome is that I've now done a bit of web browsing and obtained the information I require together with a circuit diagram I can understand.
I need a relay? OK so I bought a pair of 12V relays through eBay not knowing there were a number of types of relay. I mentioned this to Big Al whilst he was visiting us on Sunday and it turns out I bought the wrong type of relay which by the way they both arrived today. Alan kindly offered to dig out a suitable relay for me which is generous of him and thanks for this Alan; Alan also sent me an eBay number of the correct type of relay I need so as these are cheap I bought two which should arrive shortly.
I'm using the relay in a low voltage signal circuit of 10V to control the 3 phase VFD and I'm being extremely careful not to do anything silly because these VFD's are not cheap and easily damaged. I've got the Graduate running OK so all I now need to do is to incorporate the new relay when it arrives and I'm home and dry. I realize relays are common place in electrical work but don't come under the training of mechanical engineering? I enjoy learning as I go along and it's been interesting researching relays and how they work; there are lots of videos on the subject on YouTube. I'm powering the relay coil through a small 12V PSU independent of the VFD because I don't know how the VFD would react to the relay coil being turned off and it's possibly safer than adding a diode or guessing what current is available at the VFD 10V supply ?
Now back to what I do more naturally which is mechanical engineering. The final job on the Graduate was to sort out the tail-stock. At some previous time the eccentric locking cam has been bodged in fact there was absolutely no sing of the original cam; in its place someone had drilled and tapped off center to accept a set screw which was meant to act as a cam; this set screw was very loose being only located by a few threads; it locates through an eye bolt and at each side of the eye bolt a washer had been added; the threads were mutilated by rubbing against the eye bolt and even the original lever had been replaced by a length of threaded rod the end of which had been covered with plastic tubing.
Had the lathe come from a private seller this sort of bodge wouldn't have bothered me in the least but the Graduate came from a school and sported a sticky label to the its head-stock saying it had only been fully serviced last year.
I've just spent a couple of days sorting the tail-stock out. I've now made a brand new complete spindle/cam and brand new lever. Turning the spindle was easy using the small Clarke lathe but turning the cam on the spindle end in this small lathe was a test of patience because of the huge overhang from the four jaw chuck. With the spindle chucked and running eccentrically there was a real risk of forcing the spindle from the chuck but with a lot of patience and light cuts all went well. The spindle is a precision fit and the cam was turned at maximum diameter just to allow entry into the eye bolt.
The lever was nothing more than a length on BMS and this was threaded 8mm at each end then polished in the lathe under power. The spindle end was drilled and tapped 8mm at an angle to accept the new lever then a new plastic knob was turned and fitted; just for good measure I also made two plastic caps to cover two exposed threads. Everything was given a liberal greasing then assembled and the tail-stock is now working as it should.
Once the relay is added the Graduate will be then completed and ready for some serious turning during winter but before then I'll disappear again whilst I continue to make the garage into my workshop.
Kind regards, Col.
WOW; I think I've caught up a bit at least can have a breather after three weeks solid restoring/upgrading this Graduate.
I have the Graduate running through the controls I removed from the Jubilee which are mounted on the wall behind the lathe but I am about to add additional wiring allowing me to use the original start/stop buttons. I've never had the need previously to understand how relays worked; the relays I've used and wired up have been motor contactors supplied with connection diagrams.
I tried wiring the original start/stop controls and at first couldn't understand why the lathe would only run if I held in the start button and it stopped as soon as the button was released?
I had installed a "latching" button on the Jubilee and this single button controlled both start and stop; I had also added an emergency stop to the Jubilee this too being latching.
I want the Graduate buttons to work correctly neither of them are latching; the start button is the standard momentary push to make and the stop button is push to break. The outcome is that I've now done a bit of web browsing and obtained the information I require together with a circuit diagram I can understand.
I need a relay? OK so I bought a pair of 12V relays through eBay not knowing there were a number of types of relay. I mentioned this to Big Al whilst he was visiting us on Sunday and it turns out I bought the wrong type of relay which by the way they both arrived today. Alan kindly offered to dig out a suitable relay for me which is generous of him and thanks for this Alan; Alan also sent me an eBay number of the correct type of relay I need so as these are cheap I bought two which should arrive shortly.
I'm using the relay in a low voltage signal circuit of 10V to control the 3 phase VFD and I'm being extremely careful not to do anything silly because these VFD's are not cheap and easily damaged. I've got the Graduate running OK so all I now need to do is to incorporate the new relay when it arrives and I'm home and dry. I realize relays are common place in electrical work but don't come under the training of mechanical engineering? I enjoy learning as I go along and it's been interesting researching relays and how they work; there are lots of videos on the subject on YouTube. I'm powering the relay coil through a small 12V PSU independent of the VFD because I don't know how the VFD would react to the relay coil being turned off and it's possibly safer than adding a diode or guessing what current is available at the VFD 10V supply ?
Now back to what I do more naturally which is mechanical engineering. The final job on the Graduate was to sort out the tail-stock. At some previous time the eccentric locking cam has been bodged in fact there was absolutely no sing of the original cam; in its place someone had drilled and tapped off center to accept a set screw which was meant to act as a cam; this set screw was very loose being only located by a few threads; it locates through an eye bolt and at each side of the eye bolt a washer had been added; the threads were mutilated by rubbing against the eye bolt and even the original lever had been replaced by a length of threaded rod the end of which had been covered with plastic tubing.
Had the lathe come from a private seller this sort of bodge wouldn't have bothered me in the least but the Graduate came from a school and sported a sticky label to the its head-stock saying it had only been fully serviced last year.
I've just spent a couple of days sorting the tail-stock out. I've now made a brand new complete spindle/cam and brand new lever. Turning the spindle was easy using the small Clarke lathe but turning the cam on the spindle end in this small lathe was a test of patience because of the huge overhang from the four jaw chuck. With the spindle chucked and running eccentrically there was a real risk of forcing the spindle from the chuck but with a lot of patience and light cuts all went well. The spindle is a precision fit and the cam was turned at maximum diameter just to allow entry into the eye bolt.
The lever was nothing more than a length on BMS and this was threaded 8mm at each end then polished in the lathe under power. The spindle end was drilled and tapped 8mm at an angle to accept the new lever then a new plastic knob was turned and fitted; just for good measure I also made two plastic caps to cover two exposed threads. Everything was given a liberal greasing then assembled and the tail-stock is now working as it should.
Once the relay is added the Graduate will be then completed and ready for some serious turning during winter but before then I'll disappear again whilst I continue to make the garage into my workshop.
Kind regards, Col.
Happiness is a wreck of a cabinet to restore.
