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  1. #1
    Join Date
    Jun 2007
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    sydney ( st marys )
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    Default Gear tooth count on Back/Bull Gear.

    I am curious to hear from any members that might of replaced either there Back Gear or Bull Gear.
    If possable you either repaired or made a new Back Gear or replaced the Ring Gear on the Bull Gear or just replaced the Gears on the Back Shaft either one or both Gears could you tell me the amount of Teeth if you can recall that were on the Gears.

    IF you could also tell me the Model of the particular lathe would also be handy,thankyou.

  2. #2
    Join Date
    Nov 2005
    Location
    adelaide
    Posts
    597

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    i have a spare back gear.... one that has been damaged ( looks like some things been dropped on it) 61t x 23t unknown model it came from
    bull gear on model c is 76 t

  3. #3
    Join Date
    Feb 2008
    Location
    Melbourne
    Posts
    35

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    I've replaced my back gear and repaired the smaller gear on the bull gear shaft (not sure what it's called). I rebuilt a couple of teeth with nickel bronze weld. It worked OK but I would not like to do it again.

    The main gear has 76 & 38 teeth, the back gear has 62 & 24 teeth.

    Greg

  4. #4
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    Jun 2007
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    Default

    Thankyou for the responses,the main reason Im curious as to the tooth count is that untill recently I thought they were the same for all models up to the introduction of the 260.

    Im not 100% sure but I dont think it makes a great difference if a Back Gear or Bull Gear of different tooth counts are fitted.

    I think the difference would only result in the final spindle speed differing slightly.

    The other thing that dosent really matter but needs to be noted is that the Diameters of the Gears is the same across all models,this could catch people out if they work off the standard formula for determining Gear OD.

  5. #5
    Join Date
    Sep 2006
    Location
    Mallacoota,VIC,Australia
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    53
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    HI pipeclay,
    I forget about this question, I had seen it and meant to check it out. I am sure that My Model A plain bearing Hercus has a 76 tooth Bull Gear. I have also got a Model C plain bearing Hercus headstock for parts I am also sure that its Bull Gear has 76 teeth. Where My Brother Works they have a Model C plain bearing Hercus it's Bull Gear has 76 teeth. I also have a second hand Bull Gear (needs one tooth repairing) off Mick Moyles. That I bought for My Model A plain bearing Hercus,this also has 76 teeth.
    I also have a Brand New Bull Gear that I bought of Hercus on eBay. This Bull Gear was bought for My Model A plain bearing Hercus. Questions were asked as to suiting the Plain bearing Model A Hercus, before I bought it - I was told it does. This Bull Gear however I discovered to My disgust quite some Months later has actually only got 75 teeth. I have been meaning to Email Hercus to ask them what is it for or was it cut wrong, but I haven't got around to it. I wondered whether it might be for the Roller Bearing Model A Hercus. Does You anyone else have any ideas to this?.
    I am 99.9% sure from memory that all the Teeth Numbers are correct. I will however verify this later Today.
    All The Best steran50 Stewart

  6. #6
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    Default

    How wide is the gear that was suppied.
    Not sure but from what i have been able to find out the 9" Gears had 76 teeth although the tooth count on the backgears does differ between the models or depending on who made them.
    The 1 that you have could possably be off a 260,the 260's appear to have differing tooth counts.
    If its any interest to you I can repair the bull gears for $70.

  7. #7
    Join Date
    Sep 2006
    Location
    Mallacoota,VIC,Australia
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    HI,
    The Gear Tooth Numbers for each Bull Gear that I listed are spot on. Pipeclay the width of the teeth is about 16mm. Yes, I knew You could repair Bull Gears. I don't know if I will get it or not, maybe next Year. I really want to Buy a bigger Lathe. I have been looking at the Hafco AL-336. Do You or anyone know the Bull Gear Teeth count on the Model B Hercus?. I am going to go know and try and Email Hercus about what the Bull Gear might be for. Oh one last thing although the Bull Gear has one tooth less. The Teeth do appear to be the same, they seem to mesh okay with the opposing one on My Lathe.
    All The Best steran50 Stewart

  8. #8
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    The 260 has 75 teeth on its gear.
    As far as i can workout it dosent matter if the Bull Gear or Backgears have a different count to what you allready have.
    The only thing as far as I no will be either a slight increase/decrease in the final RPM.
    All the gears will fit there diameters are all the same.

  9. #9
    Join Date
    Sep 2006
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    Mallacoota,VIC,Australia
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    HI pipeclay,
    That was quick. Okay so it sounds like your Saying that if I used that Bull Gear on My Lathe. That it will only have a slight increase or decrease in Speed. I would have thought though that the other Gear on the Spindle (with the Pulleys) would have had to be changed to.
    All The Best steran50 Stewart

  10. #10
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    Jun 2007
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    No the gears on the spindle Pulley will be ok,due to the fact that as long as they are all 16DP they will all mesh together ok,irespective of the tooth count because the Bull Gear free wheels untill it engages on the Small Gear on the back Shaft.

  11. #11
    Join Date
    Sep 2006
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    HI pipeclay,
    I see what You Mean, I had a look at how the Back Gears work tonight. The 75 tooth Bull Gear as it is the same diameter as the 76 tooth Bull Gear will work fine. Hercus got back to Me today (three Emails) with some interesting Info. I am going to start a new thread with the Info it will be Titled ' Bull Gear info from F.W. Hercus'.
    Thanks for Help pipeclay.
    All The Best steran50 Stewart

  12. #12
    Join Date
    Jan 2009
    Location
    Captains Flat
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    71
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    122

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    I just noticed this thread having put one up myself yesterday on the bull gear or back gear...not sure of correct name. I have Model ARM lathe, serial no 15015 with 75 teeth on the big gear nearest the headstock. My other thread was about having broken one of these teeth off,

  13. #13
    Join Date
    Jan 2009
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    122

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    I mentioned in another thread that I have a broken tooth on my 75T Bull Gear. I have just picked up a 76T replacement. While I understand that this will slow spindle speed marginally, does it affect screw cutting in anyway or does the lead screw also slow down marginally through the connection of spindle to gearbox via gears?

  14. #14
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    The thread cutting wont be effected,the spindle turns slower in backgear.
    Even if you increased your motor pullet to give your more RPM or decreased or increased the size of the top pulley it would make no effect.
    The leadscrew turns at a certain speed due to the ratio of the gears or gearing.
    Did you end up getting a new one or second hand,how much was it if you dont mind me asking.

  15. #15
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    thanks Pipeclay. Next challenge is to get the 75T gear off the spindle. When I have done that, I may send the 75T gear to you along with the broken tooth to repair and to give me a spare. But one step at a time.

    I got the gear from a box of bits and pieces that are sitting at the back of an engineering supply firm in Canberra. They also have a full ARL (imperial) lathe in good condition (serial number thirteen thousand and something) in their back room for sale but I could not see a price on it.

    I paid $50 (at my suggestion as the staff could not consult the boss who is on holidays). I have also previously got a face plate, back plate (for chuck), drive plate and fixed steady from the same box. All $50, hence my offer of $50 for the bull gear.

    I am still looking for a travelling steady. I saw a fella at the recent Canberra swap meet with 3 fixed steadies and two travelling steadies but he wanted $200 each which was too much for me.

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