1953 Colchester Student Mk1 6" gap bed - A restoration project - Page 3





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  1. #41
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by plunger View Post
    The change gears are generally cast iron and the headstock gears normally are case hardened or induction hardened because they have to mesh during changes and not only just go round in circles. I would be suprized if they are not hardened but a file test will tell you.
    As you know www.lathes .uk is the go to source for all quality lathes to get info..We have recently had gears made for a southbend rebuild. They came in at about R400 per gear.These are gears made on a shaper

    I wasnt prepared to pay over R2000 for my gear so I made it myself. But I made a cutter and hobbed it using the homemade cutter.
    In this pic you can see the gear set up in a dividing head and I have pre gashed it. The homemade hardened hob is the cutter below . It is simply wound into the free spinning bronze precut gear and it self generates a close to perfect worm gear.
    Came out real nice and in use for ten years now.Attachment 572233
    I had a gear expert friend of mine over. He tested each gear and all are mild steel in the headstock and gearbox. The gears in the apron are cast steel as is the one gear cutting exchange gear. He was quite interested when I mentioned that on another forum, the guys take weight lifting weights (which are cast steel) and machine their cast steel gears from this.

    Thanks for the info. Interesting. Here is another great video on this topic. https://youtu.be/YWaF_QhcxA0

  2. #42
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Let's continue on our journey. We are going to do some time travelling now. First into the future up to 20 May 2020 which is actually today, but that is a few days in the future in this thread's timeline.

    I took the bronze bushes to be resleeved at a friend of mine who builds miniature steam locomotives. He said no problem. Then I went to one of his friends who is selling his whole hobby workshop and spent about two hours there looking at all the drill bits, chucks, reamers etc etc and etc. I hope he will accept my offer ...

    Then I went to buy primer to paint the lathe with. Just a teaser!

    Now back into the past, a few days from where we left off in the previous post. ... "Bridge to engine room. Hyperdrive power Scotty!"

    We left off where I was pondering on how to remove the speed selector gear from the shaft. One thing your brain needs to solve an issue is time. So, stop fretting about the problem, move onto something else and your brain will tinker on its own towards the solution.

    The gearbox was next to be stripped.

    The first step is to get the gear selector arm removed from its shaft. On Richard's thread he states that he gave up on getting it off. I took a deep look at the arm on this lathe and it had a grub screw fitting to what looked like the cap. So that came out. Then out came the big mamma of a cap screw in the arm. OK the arm should now move.

    On went the puller.





    And no luck. The arm did not budge at all. All we did was to damage the entry to the threaded hole in the cap. So out came the countersunk reamer and the needle file. Working on the opening with a bright light showed me that the treaded hole is actually quite deep. Aha, said my brain. Screw one of the gearbox cap screws into the hole and see if something moves when you pull. Nope that did not work as the thread in the hole was filthy and the cap screw only went in by about two turns.

    Out came the taps. Thank heavens I bought a whole lot of old taps a while back. I found what I needed.

    Next was the ratchet tap wrench and off we went for a tapping ride.





    As I cleaned the thread the tap hit the hole bottom, locked and suddenly the whole cap turned and I could pull it loose! Wow, so simple.





    Hmmm, what do we have here?





    Two locking grub screws. No wonder the puller did nothing. Out they came and the arm simply slid off like you would slide on your bum on ice. Smoothly!





    BTW, I posted this method on Richard's thread and he had no hassles replacing the leather seal. Only issue is he forgot there is oil in his gearbox and it leaked out all over the show. Here is a picture he posted showing how easy it is if you know how!





    That's done. What is the next step?

    Aha some coffee! Pondering on what to do over a cup of good coffee is good for the soul. OK, it is an either/or on where to start on the gearbox. The lid or the lid. Whichever you choose. For us Afrikaans Boere a "deksel" is a "deksel" whether it is upside down, on top or on the side. (A lid is a "deksel" in Afrikaans for the overseas folks).

    So we chose the lid. The top one. Out came the cap screws and wow, gears! Looks like we can get the one gearset out but how?

    I went to our friend DuckDuckGo (no ... not Mr Google if you love your privacy a tiny whee bit) and found this video on disassembling a similar gearbox.

    So I removed the change gear.




    The shaft is stuck.





    OK there is the circlip the guy mentioned. Opening it up with the circlip pliers allowed it to snap promptly. Why do you always pick the incorrect direction pliers first





    For future reference, the OD of the slot where the circlip fits is 17,86mm. Somewhere around 45/64"






    This allowed us to pull the top left shaft and gears from the gearbox.

    Now onto removing the lid. The "or" one. The side cover plate.

    Off it came and there is the reason why there was no oil in the gearbox. A broken gasket... wow, a gasket ??!!?? Mr Butcher you missed one!





    Take note of the brass rectangular thingeys. Three of those.







    Now you know why I said make a note of the one in the headstock. I did warn you!

    The gearbox looks impressive!









    All angles covered? Nope ...





    The video shows the next step is to remove the selector bar. It is fixed to the bottom of the gearbox with two cap screws.





    Carl cleaned the cap screw heads, and promptly bent Uncle Allen's key to a position where it could shoot arrows. The cap screws refused to move. OK, you know the drill. No beer, so we go to the coffee machine for some good Ethiopian Rasta coffee. OK, leave this step for later ...





    Let's try the slide's locking bolt. It is a 7/16" AF spanner that works there.








    That snapped loose with a loud click. OK, so if that snapped loose, the cap screws will be locked in place due to age and should also snap loose. Keep that in mind brain.

    At this stage we have reached the point in this dimensional space where we meet up with the late afternoon before the morning of the day where I made the gear puller. Therefore in our time, time to relax. Not that working on the lathe is not relaxing.

  3. #43
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by mygoggie View Post
    Another wish item is the VFD ... maybe I must open a Patreon account and compile an Amazon or RSOnline wishlist ... nudge nudge, wink wink!
    If you are willing to pay the courier fees I can borrow you a 2.2 kW 1ph to 3ph VFD for as long as you need it.

  4. #44
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by Tiaan Pot View Post
    If you are willing to pay the courier fees I can borrow you a 2.2 kW 1ph to 3ph VFD for as long as you need it.
    Sjoe, Tiaan Pot, enige tyd. Ek PM jou.

  5. #45
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    I am just putting feelers out as to the gear repairs. Is there anyone in this community that is willing to donate some machine time to cut teeth for the broken gears? A mate of mine will do the welding and brazing required. Another has offered to turn the gears to size ready for teeth cutting. So the only puzzle left to complete the picture is the teeth cutting.

  6. #46
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by mygoggie View Post
    I am just putting feelers out as to the gear repairs. Is there anyone in this community that is willing to donate some machine time to cut teeth for the broken gears? A mate of mine will do the welding and brazing required. Another has offered to turn the gears to size ready for teeth cutting. So the only puzzle left to complete the picture is the teeth cutting.
    I could have possibly helped but I'm too much of a hobbyist machinist and also too scared that I might stuff it up even further. Don't even know if this is possible.

    My train of thought is as follows:
    How to put this, Firstly, the space width between the teeth at the dedendum would limit us to a certain diameter EndMill. If it was possible to find an endmill with a diameter that could give us full gear cut depth then I would have done the following.
    Draw the gear out in CAD to match the Tooth size.
    Mount the gear flat on the mill bed and somehow try and align a tooth so that it's perpendicular to one of the mills axis 'X' or 'Y'
    Then setup a toolpath and get the center off the gear, press the button and hold thumbs.
    GaryG

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  7. #47
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Theoretically if you can get your lathe to work you could cut the gear yourself by grinding a piece of hss for a fly cutter. I have made a 20 spline broach tool using the top slide as a shaper and the indexing I did by making a mandrel that fits into the back of the spindle and expands to hold a 100 tooth gear . Then I just used a spring loaded plunger to index every fifth tooth and it gave me my 20 cuts on the broach.
    If you did a cad drawing(jealous I cant draw) on carboard and glued it to a mdf board and drilled 109 or whatever holes in it you would get an extremely accurate indexing ring in order to cut your gear.I used my top slide as a shaper but you can also just use the rack.

    If you filed the bulk away (you will be suprised how close a file will get to being good enough)then you could just clean it up .I have always wanted to try gearcutting but the gearcutters are expensive. That gear I showed you that I made is a different process altogether. It generates itself. It picks up the gashes in the teeth and hobs it away.
    For the change gear I would ask your laser company to quote you on the cost to cut one. If you know the dp and pressure angles this could be wirecut or lasercut .I have no idea how accurate laser cutting would be . Do you think they could do it.

    As for the headstock gear if you look at the video of how they make colchesters you will see the teeth are individually induction hardened under water .I think it may not work well if that gear is not hardened because everytime you change speed these gears crash into each other to mesh . If you use a vfd and change speeds to an absolute minimum then maybe you will get away with it.

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

    The other way you could do this I think is if you put a bar between centers and crossdrill in the bar to make a fly cutter in the shape of a tooth . Then if you made a free spinning mandrel that can be locked and bolt it to the t slot in your carriage top. Then you make an indexing pin on the side to go into the teeth of the gear you could use the existing gear as your indexer.

  9. #49
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by ViperR View Post
    I could have possibly helped but I'm too much of a hobbyist machinist and also too scared that I might stuff it up even further. Don't even know if this is possible.

    My train of thought is as follows:
    How to put this, Firstly, the space width between the teeth at the dedendum would limit us to a certain diameter EndMill. If it was possible to find an endmill with a diameter that could give us full gear cut depth then I would have done the following.
    Draw the gear out in CAD to match the Tooth size.
    Mount the gear flat on the mill bed and somehow try and align a tooth so that it's perpendicular to one of the mills axis 'X' or 'Y'
    Then setup a toolpath and get the center off the gear, press the button and hold thumbs.
    There are ways to do this by cutting vees at the correct pitch distance into a piece of tool steel and hardening it . Then it can also generate a fairly accurate tooth. Its in Ivan Laws book . I will try find a link. Change gears are very forgiving. Those headstock gears are a totally different story.
    In this link you can see a piece of hss thats been ground in the shape of a tooth.http://mikesworkshop.weebly.com/maki...r-cutters.html
    Last edited by plunger; 2020/05/21 at 10:30 AM.

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  11. #50
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project


  12. #51
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Yeah, "This Old Tony" - I love watching his channel.

    The best way is to find/buy a cutting wheel for the 16TP gear, use a dividing head (** wishlist) and a milling machine.

    https://youtu.be/YWaF_QhcxA0

    Thanks for all the leads and info and tips. I will look at each in detail! Munch appreciated!

  13. #52
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by plunger View Post
    For the change gear I would ask your laser company to quote you on the cost to cut one. If you know the dp and pressure angles this could be wirecut or lasercut .I have no idea how accurate laser cutting would be . Do you think they could do it.
    They can water jet cut it accurately. I was thinking of going this route with the change gears.

  14. #53
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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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  15. #54
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    R5k for one that's needs a bit of love
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  16. #55
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    I have just finished rebuilding a Boxford lathe and had to repair some gears and make up others from scratch as it is just too expensive to import these. To repair a missing tooth or two, I cut a slot across the gear and brazed in a piece of the same material (cast iron) Then I ground a fly cutter bit using the good teeth as a gauge. Gashed out with a slitting saw on the mill and then finished with the fly cutter and touched up with a needle file - got a perfect result.

    The new gears I turned, gashed out with a slitting saw and then fly cut to profile. A bit slow but the end result is great. I made myself a simple indexer using laser cut plates to get the required divisions. Gears are cut on a mandrel which replaces the chuck - a 3-jaw chuck has runout and does not center the workpiece accurately enough to cut gears.
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  18. #56
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by JohnnoK View Post
    Roger the Bodger probably read about a property of some greases called Thixotropy and bunged some random, unsuitable grease in it.
    Had a good laugh now. Yeah, thixotropy must have sounded very important to him.

    He forgot that old grease becomes rheopectic if it is thixotropic in the first place ... ;-)

  19. #57
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Water jet cuts to a slight taper so you would still need to clean up the teeth with a fly cutter or shaper to get them accurate and parallel.
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  20. #58
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by mygoggie View Post
    I am just putting feelers out as to the gear repairs. Is there anyone in this community that is willing to donate some machine time to cut teeth for the broken gears? A mate of mine will do the welding and brazing required. Another has offered to turn the gears to size ready for teeth cutting. So the only puzzle left to complete the picture is the teeth cutting.
    What about having it waterjet or laser cut?
    Waterjet will give you down to 0.001" tolerance if the machine is capable and well set up.
    Cheers,
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Both waterjet and laser are very accurate but cut to a slight relief angle so the cut face ends up being slightly tapered. The surface finish is also not good enough for a gear and needs to be smoothed off. Tried this, was not happy with the results.
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    Default Re: 1953 Colchester Student Mk1 6" gap bed - A restoration project

    Quote Originally Posted by John Lindsay View Post
    Both waterjet and laser are very accurate but cut to a slight relief angle so the cut face ends up being slightly tapered. The surface finish is also not good enough for a gear and needs to be smoothed off. Tried this, was not happy with the results.
    Good to know @John I will not waste my time on this then.

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