1953 Colchester Student Mk1 6" gap bed - A restoration project





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  1. #1
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    Default 1953 Colchester Student Mk1 6" gap bed - A restoration project

    To start off, a bit of history on this topic. I bought a Colchester Student lathe a few years back for next to nothing and it has not worked a lot as it was super noisy and had a bad vibration when turning.

    A few months back the electrical switch at the back broke and this started a whole exercise to discover the correct switch to find and install. This in turn bred quite a few babies which in the end resulted in me deciding to rip all the electrical wiring out. In turn this exercise bred more babies so now the broken switch replacement exercise has turned into a restoration process.

    This on top of the following other projects I am busy with and have started threads on:



    A few fellow forumites on the AVF asked that I start a thread so that they can lift my arms when these become tired and give some motivation.

    So I decided to copy the thread here for all you guys loving old machines ...

    The lathe's head before I started working on it. It is a roundhead Student with the head being loose and bolted to a V-bed and a gap in the bed between the head and the carriage way section.





    The switch that started it all.





    And what should be in there ....




    I decided to determine what the existing wiring looks like and found this. A replacement contactor hanging by one screw.




    Insulation that simply fell away from the wire.




    Well joined wire to the coolant pump.




    And the straw that broke my patience ... the main wire leading to the on/off switch melted and welded themselves back together ...




    So ... I had enough of shoddy work and I decided to remove all the wiring and electrical equipment ....


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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    I wanted to start this restoration a while ago, but the one thing that stoppped me was that I did not have a C-spanner to unscrew the chuck's holding nut.

    End of last year I set out and asked on the Colchester group on groups.io for help in designing one. The response was quick and some valuable info came forth.

    After some measurements (no not the bar type) and discussions on the group message I had what I needed.




    It is interesting to note that the C-spanner works on friction and not on the front lip gripping. The lip is just to let the spanner lock into place to get the friction grip created.

    I sat down and designed a new spanner on CAD. If you look at the drawing you can see the surfaces where the friction between spanner and nut is created.





    This CAD design I then sent to a local shop to have it laser cut. I had to pay the minimum fee of a full R250 as the actual cost was a lot less than that. Still a bargain compared to buying and shipping one from overseas at a cost of about US$160.

    After a few days I fetched it and deburred the edges. I also noted that the locking lip is in fact rounded at 90 degrees to the length of the spanner to ensure it fits correctly in the slot grinded into the nut.

    Painted a nice red so that I do not loose the spanner.





    A perfect fit! Job well done.





    Onto restoration then as the chuck can now be removed!

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    After stripping out the electrical switchgear panel, I moved onto getting the coolant pump out.

    Low and behold it was secured to the chassis with only one very loose cap screw.




    The ID tag of the pump for anyone interested.




    Onto cleaning the sump. Why is there only oil in there




    Fortunately I love woodworking by hand so I had a BIG pile of shavings available. This is the best method to soak up oil. So into the sump went two giant handfulls of shavings.




    I let it soak overnight and in the morning simply removed the shavings.

    Excellent natural fire starter these shavings!




    A closer look for anyone that has never done this before.





    The sump after wiping with another handful or ten of shavings.





    And cleaned with some turpentine and rags.


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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    So yeah I really had a battle with the lathe the last two days. I could not get the spindle out. More on that in a later post. I think I must sit down now and try and get this thread up to date. Now where did we leave off?

    Oh yeah, switchgear and coolant pump.

    Let me finish off the coolant pump up to where I am now with it.

    The pump sounding like an old helicopter trying to take off when you switched it on, so I knew it had some trouble with its innards. So onto stripping it.

    Off came the lid.

    The underside of the lid was covered with something that resembled bitumen impregnated gauze of about 4mm thick. This to form a seal to the insides. It was all broken up and not sealing at all.





    The wiring connections. Somewhere, sometime in this space-time continuum an electrical wizard decided to replace only a portion of the cable leading to the pump with a short piece of 4-core cabtyre.










    A rock hard rubber boot. Rubber and oil ain't drinking partners ...





    The sieve at the bottom of the pump was blocked so off that came.




    Then the fun started ... removing the bearings. Normally with a electrical motor you have a cylinder in which the stator is housed. Check. End cover on each end. Check. One cover off, one bearing visible? Check. Then support the cylinder and drive the shaft from the bearing housed. Yes ... OK yes but nothing happens ...

    After trying to get the shaft to move from the bearing for two hours, the shaft suddenly moved. Yes, the complete bearing with shaft broke free from the housing when the bottom circlip bent, broke part of the bearing house and sprang loose.








    Quite a number of shimming washers between the top bearing and the top circlip.






    The bearing gave way with a very big puller. It was rusted to the shaft ....





    The bottom bearing came out from the housing as it should.





    Then onto getting the shaft from the bearing. Placing two supports under the bearing and giving the end of the shaft a sharp hit with a bronze hammer did the trick.





    First time I have seen these little corrugated rings fitted between the housing and the outside surface of the bearing.











    A wise gentleman from the groups.io group says that these act as a spring to give way to make the non-self centering bearings align correctly on the shaft. Interesting! Never too old to learn.

    Of interest is that these bearings are in fact metric. Very strange to find metric bearings in a 1953 British made lathe...

    For reference the bearings that were installed are GMN 6200 sealed spindle bearings. The oil seal being a MIS06. Here is a picture of the bearings and the oil seal.






    Removing the oil seal, shows it was not only rock hard, but in fact fractured.



    So my common sense tells me that as the motor would heat up, it would push air out of the housing through the broken seals at each end and when cooling down new humid air will be sucked into the housing allowing the moisture to ingress everywhere inside the housing. I guess I will have to bake the stator as well.





    Onto cleaning the bottom section of the pump. Looks much better.












    Cleaning the shaft, bearing surfaces and rotor worked well with one of those green dishwasher sanding cloths. The electrical connection plate I soaked in @Family_Dog's favourite drink.





    Cleaning the top surface of the housing ...





    ... and it revealed it was hit by a hammer in it's past life! I sanded it down on 250 grit wet paper glued to a pane of 6mm glass to get rid of most of the dings. This is good enough to get a seal again.





    That is how far I got with the pump. Now onto getting the paint off the housing and the top cover and spray everything with an oil proof epoxy paint.

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Next portion to cover to get this thread up to date is the electrical wiring and panel.

    I could not figure out how the electrical circuit works as my lathe did not have the original switch fitted (refer above) and what I could see did not make any sense.

    So back to the group I went. Another kind gentleman, Richard, had the same issue during restoration of his Colchester Student lathe. You can read his struggles here. Between him and the gentleman helping him, Phil, I could start to understand what is what.

    Apparently the switch is a no-voltage limit switch and together with the contactor forms a circuit where the lathe cannot start again when the power supply goes down whilst the stop/start handle is in the "ON" position. You manually have to move the handle back to "OFF" and then back to "ON" to get the lathe to run again after the power supply is restored.

    As per Phil's hand drawn diagram,





    which is based on either of these two wiring diagrams







    the switch works as follows:

    "Refering to the drawing you will see what we call the limit switch (because that is what it says on the case) is referred to as the Craig and Derricot release switch.

    Starting at the contactor coil, you will see that one side of the coil is connected to L1 which is an incoming phase. Remeber that the coil works between two phases, there is no neutral in this set up!

    The other side of the coil connects to terminal 2 on the contactor, and then to the red wire which goes to the C&D switch terminal 3.

    The other phase used is L3 which goes via a link wire through terminals 10 and 9 on the contactor, which are the overload cut out switches, and then on through the yellow wire from terminal 9, through the end cover and lock switches to terminal 1 on the C&D switch. Note a mistake on the drawing, in that the yellow and red wires which cross adjacent to terminal 3 on the C&D switch are NOT connected but the semicircle has been ommitted from the drawing!

    When the end cover is fitted, and the key switch is on, terminal one, yellow wire on the C&D switch is "live".

    When the switch is lifted from the off position to the intermediate position, (we will call the unmarked terminal on the C&D switch 4) 1 and 4 are connected together, and 2 and 3 remain connected. the live goes from1 to 4, down the link to terminal 2 across the switch to 3 and back to the coil on the red wire, and the contactor pulls in/motor starts.

    on the contactor, the holding in contacts close the circuit between 1 and 2, and as the start handle is moved fully in to the on position, the C&D switch opens 2 and 3, and 1 and 4 remain closed. Machine is now running, and terminals 1 and 4 on the C&D switch have become part of the holding in circuit and the machine will continue to run till the contact is broken by pushing the lever to stop, or if the power fails, the end cover is removed, or the key switch is turned off."


    Wow, I thought to myself, let me really understand this. So I spent an hour doing my own diagram of the description. Obviously in those yonder years, a contactor and a switch was an expensive item so the designers had to make do with as a smart design working on limited equipment. Well, their logic and method works fine. Just not the way we would do it today with our cheaper and much more efficient and effective switchgear.

    OK, I understood the logic now, but I had no idea the lathe had the two switches as stated in the description and the wiring diagram. So I asked a few questions and was directed as to where I must look. Lo and behold I found them. I really had to scrape a lot of gunk away!

    The key switch at the tailstock end in the upper back corner of the drawer.





    No, there is not a key like you will recognise today. It is a simple cupboard type lock with the hollow shaft key!






    The switch model and type.





    The cover switch was even more obscure to find. Find it I did as I was determined ...

    It is here somewhere ...





    Almost there ...





    Gottit





    I would never have thought to look there!








    And a close up of the cover switch.





    So that is the switching circuit sorted out. Onto getting the wiring panel stripped and cleaned.

    The panel connects to the lathe's supply circuit with a three prong plug as seen at the bottom of this earlier posted photo.







    It appears that the panel was wired by a third party and then simply plugged into the lathe.






    The female socket mounted inside the lathe and made from Bakelite or some form of organic cellulose sheets.






    The "new" contactor is a Telemechanique and it looked like it can still function after a good clean.







    Aaah ... fuses!









    The one fuse contacts were spark eroded, so I cleaned it up and soldered a new surface to it.







    ... and promptly lost it somewhere in my workshop when it went flying from my hand ... find it I will.


    The coolant pump switch on the left and the ON/OFF/REVERSE main switch on the right. Massive three phase switches made from bakelite.









    All stripped from the cast aluminium panel.







    Electrical switches and fuses went into @Family_Dog's favourite drink and I left them there for four hours. Came out very clean and the brass even was sparky .. I mean sparkling ...







    All cleaned and waiting to be assembled.





    To get the main switch's selector handle off was a mission. Some monkey snapped the locking machine screw in this handle and it broke in two, lodged secure at an angle in the handle. I had to break the handle to get to the screw and then remove it.





    I made a thread here on how to repair it.

    Well, this is as far as I got with the electrical wiring and logic. My next step was to determine the status of the main bearings of the lathe as these would dictate if it is worth the while (and money) to fix the lathe. More later in a next posting ...

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Before I start restoring, I wanted to understand why the headstock was filled with grease and why at high speed it was so noisy. Maybe something expensive needs to be replaced which will make this whole exercise fruitless and not worth the money.

    So ... bring it on grease monkey.

    First step normally is to remove the side cover. Check. Did that a few days back and battled to get it off as the standoffs it is fastened to are bent. Remember it is cast something so no hammering!

    Then onto removing the drive belts. These must be a matched set. The belts are the same size, but that does not help anything in this type of installation.








    I could not find any markings stating that the two V-belts are a matched pair so that explains the vibration in the drive train. In non-matched pairs one belt is always longer than the other and will hunt will turning causing a vibration. For this reason I always use Nu-T belts. A lot more expensive but lasts forever and does not care about the condition of the pulley's groove.





    OK, this is turning into a nightmare ... the belts cannot be replaces without removing the drive pulley ...





    This means I need to get to the electrical motor and get that slacked off and then remove the drive pulley. First step is to move the lathe away from the wall. Now ... because I threw or gave away all my odds and ends with the planned move to NZ, this included my roller set. OK, I managed to find three short pieces of 3/4" pipes and with two wedges and a crowbar I managed to move the lathe enough so that I could get to the electrical motor.





    Now for the motor experience ...

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Wow, amazing. Thanks for taking the time to share this with us.

    Iím still trying to get my hands on a Myford or Boxford at a reasonable price but not having much luck at the moment.
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    This is awesome! Thanks for posting this, i enjoy it, and admire your patience!

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Beautiful to see! The fact that you can take it to pieces and then put it all back together again is what is really a skill that is scarce nowadays.

    It's really sad that nobody fixes anything nowadays. Throw it away and buy a new one!

    Can't wait to see the video of it working again.

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by NewLandy View Post
    Beautiful to see! The fact that you can take it to pieces and then put it all back together again is what is really a skill that is scarce nowadays.

    It's really sad that nobody fixes anything nowadays. Throw it away and buy a new one!

    Can't wait to see the video of it working again.
    Yes, I hate the fact that everything is throwaway these days. This is just a giant Mecanno set and I should be able to fix it to a usable standard.

    Interesting reading is the way Sweden has now forbidden throwing away of equipment. All must go to service centres where old toppies with skills teach the owner how to repair it. If FUBAR then the old toppie teached them how to strip it for usable parts etc and then how to recycle it.
    Last edited by mygoggie; 2020/05/20 at 09:37 AM.

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Re the grease, I believe that some modern gearboxes are filled with something like grease from new, those sealed for life gearboxes I think that are found in some German cars. Perhaps the butcher heard about this or could the grease have been used if there was too much of an oil leak going on.
    Last edited by B Murr; 2020/05/20 at 09:50 AM.

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by B Murr View Post
    Re the grease, I believe that some modern gearboxes are filled with something like grease from new, those sealed for life gearboxes I think that are found in some German cars. Perhaps the butcher heard about this or could the grease have been used if there was too much of an oil leak going on.
    Roger the Bodger probably read about a property of some greases called Thixotropy and bunged some random, unsuitable grease in it.
    Cheers,
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    Thumbs up Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    I have had various requests to get my backside in line and start doing all these projects of mine on video as well.

    So please give the poll at the top of this page ^^^ (yes, up there!) a vote so that I can motivate myself!

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    The old paint was a kind of fluffy raised surface that almost look like sandpaper with spikey points. Any idea what this paint is called?
    Crackle Paint?
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by 4eTouareg View Post
    Crackle Paint?
    Unfortunately it is not crackle paint. If you look at this photo you will see what I mean. It looks like sandpaper with spiky points.


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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Very enjoyable project to read, maybe not so much to be doing. You show alot of patience, I would have broken some cast iron by now.
    Do you have to replace the bearings,?Grease amazing. Are those not gammet bearings, They cost about 30k in some lathes.

    As for the gears ,I soppose they can be rebuilt or remanufactured. The thread gear could be bronze welded and remachined, . The spindle bearing I think are hardened and ground. That will be much more expensive to make.
    That looks like a very robust lathe in a small footprint.I suspect thats a 50mm spindle.If so very nice. I notice most colchester lathes have their gaps missing. Look on gumtree and everyone is missing the gap.

    I forgot if you told us what you do.? And whats this reference to New Zealand?

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by plunger View Post
    Very enjoyable project to read, maybe not so much to be doing. You show alot of patience, I would have broken some cast iron by now.
    Do you have to replace the bearings,?Grease amazing. Are those not gammet bearings, They cost about 30k in some lathes.

    As for the gears ,I soppose they can be rebuilt or remanufactured. The thread gear could be bronze welded and remachined, . The spindle bearing I think are hardened and ground. That will be much more expensive to make.
    That looks like a very robust lathe in a small footprint.I suspect thats a 50mm spindle.If so very nice. I notice most colchester lathes have their gaps missing. Look on gumtree and everyone is missing the gap.

    I forgot if you told us what you do.? And whats this reference to New Zealand?
    This lathe has no Gammet bearings, a fact which nobody in the Colchester circles have heard about. It has Hamilton and SKF super precision bearings, all original. I am not going to replace the bearings as the amount will be close to R25k for the three bearings and they are designed to last forever. OK in oil ...

    Yes, the cast steel gears I will have to remake. Maybe someone here has a divider head and a shaper that can cut some gears for me? Some of the mild steel gears I should be able to add pins and braze over these and shape new teeth.

    I am a Civil Engineer and this is just my hobby. My big passion is woodwork using only hand tools and I am actually quite good at this. Yeah, NZ ... I was offered a very good position in NZ and thought why not? Closed the business, sold most of the stuff and gave a lot away and fortunately did not sell the house. So bags packed and at the door and the first set of flights got cancelled. Found new flights, booked and three days later these were cancelled as well ... so then NZ went into lockdown and I had to move back into the home. No job this side nor that side ... so now I am thinking of getting into my love for woodwork and going into building high end record players for those that have money. For that reason I need a sturdy lathe ...
    Last edited by mygoggie; 2020/05/20 at 03:58 PM.

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    I see you have a machine vice. ? Do you have a milling machine.?

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by ViperR View Post
    Wow, amazing. Thanks for taking the time to share this with us.

    Iím still trying to get my hands on a Myford or Boxford at a reasonable price but not having much luck at the moment.
    I am going to see a chap this morning that is selling both his Myford and Boxford lathes. I will see what I can negotiate for you. PM with what you can afford to pay.

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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    I'm with B Murr on this one. I think the Butcher tried to alleviate the oil leaks by using grease instead.
    Awesome job there. Great respect.
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