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  1. #1
    Join Date
    Aug 2014
    Location
    Queensland
    Posts
    18

    Default Removing the Hercus O Mill Standard Arbor

    Have had this mill sitting for about a year now and am starting to look now into getting it going.

    Before I start looking at the motor conversion or replacement I was hoping to see that everything is in good order before I spend any money. When trying to see if the vertical head fits and it has all of the required bits I got stauck on the arbor.

    I can see from some of the documentation that I have that the standard arbor has a No.3 morse taper, a collar sort of thing then the parts that you can see. The cutter and the various spacers held on by a nut.

    I have tried backing off the nut at the motor end a few turns then hitting it with a piece of timber and a hammer. This sounds very solid so I havent wanted to go too hard.

    Does the collar have any fixings in it to keep it from coming loose? Or do I need to give it a good whack? There is an allen key but it looks like it belongs to the spindle nose rather than the arbor.

    Is there a trick to locking the arbor in place to undo the lock nut? Tried placing some timber on the bed and raising the bed to stop the cutter from turning but didnt work. The timber just rotated and pushed the timebr out.

    Lastly, any good tips on removing the surface rust? Both the lathe and mill have more than their fair share. I ruined the paint of the lathe by using degreaser so I am a little shy about just jumping in.

    See attached PDF for a illustration of what I am talking about if needed.

    Would very much appreciate any advice given. Thanks!!
    Attached Files Attached Files

  2. #2
    Join Date
    Nov 2008
    Location
    Perth WA
    Age
    65
    Posts
    5,894

    Default

    Noob,

    To lock the arbor, ensure that the spring loaded bull gear/ cone pulley engagement pin is engaged ( pushed in ) and then engage back gear by lifting the back gear lever up into its engaged position. ( A lot of engagements! )

    The cap screws you see on the spindle nose secure the drive dogs for the arbor. They must be removed to install the vertical head's geared arbor .

    Try some gentle heat on the spindle. Mine was stuck and was hard to remove. I made a puller from some thick plate and installed it on the saw arbor using the spacers and nut to retain it. From memory I had a pair of cap screws bearing on the spindle nose. They were screwed through threaded holes in the plate. A combination of heat, tension on the screws and pounding on the drawbolt with a big hammer and a block of wood popped the arbor.

    Hope this helps.

    Bob.

  3. #3
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    3,828

    Default

    I used a hot air gun on 650șC and the larger of these two mallets.
    The handle is redgum and the head is made from Rockoak and weight in at boy 1kg (double the other mallet) it packs a decent wallop!
    IMG_6166.jpg

  4. #4
    Join Date
    Jun 2007
    Location
    sydney ( st marys )
    Age
    59
    Posts
    3,913

    Default

    I would remove the Arbor nut , spacers and cutter from the Arbor 1st before attempting to remove the Arbor from the spindle.

    You would need to return the overarm to the correct position for horizontal use, and then re-install the yoke,once this is down support will be give to the Arbor and should reduce any chance of it bending.

    You could try putting the spindle into back gear and giving the Arbor nut a good hit with a block hammer or something similar with some weight behind it.

    If you want you could put stillsons around the Arbor spacers , this may also hold the spindle from turning and take the load off the back gear.

    To remove the Arbor from the spindle release the drawbolt about 1 turn or 1/16" and give the head of the drawbolteither 1 Ora couple of good hits with the block hammer.

    If your concerned you could place a good piece of hardwood on the end of the bolt and give that a hit or use any sort of suitable dolly if desired.

  5. #5
    Join Date
    Jul 2012
    Location
    Griffith NSW
    Posts
    370

    Default

    At my last school, we had a hercus O mill that had an arbor stuck in the spindle. Previous teachers were fairly unconcerned about it, so it stayed in it for well over a decade. Well, it was at least a decade because the spindle never moved from the machine in the time I went from being a year 7 student to being a fresh out of university teacher, you could probably add a number of years on top of that quite easily. The arbor was very, very stuck. I ended up taking the spindle out of the machine and to a mate with a 100T press. We dropped a 20mm bar down the spindle and loaded it up. The 20mm bar curled up like a noodle as the pressure built up, and we were about to back it off and move to an even bigger press when it finally let go at 89 tonnes. A spark even came out of the taper when it released with an almighty bang.

    Anyway, my point is that you need to be aware that theres a time to call it quits on belting the back of the arbor and pull the spindle. All that force youre banging through its being taken up by the spindle bearings and when youve gotten tiny tim out, you need to start wondering how much abuse that bearing is taking.

  6. #6
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    3,828

    Default

    Potential damage is a product of applied force x time, so sometimes a press is not the right thing to use either. A series of short sharp hard impacts may be a better way to go. That's why impact guns do such a good job at removing stuck bolts/nuts. At the mens shed we had a stuck chuck on a small MW lathe and the blokes kept bending more and more metal bars stuck between the chuck jaws, with a locked back gear. At one point there were two blokes hanging of a bar and it would not budge and it was threatening to tip . The 87 year old fitter and turner (Our third oldest member) put some hex bar in the chuck and applied a rattle gun and it came loose.

  7. #7
    Join Date
    Jul 2012
    Location
    Griffith NSW
    Posts
    370

    Default

    Youre right, sometimes a hit is a good thing, but it only works because you can build up a given amount of energy before transfering it into the thing being pushed. Its just like getting a run up for a jump, rather than getting all that forward energy in one push, you build energy by running towards the place to jump. But the reality is that the force required to remove a taper is going to be the same whether you take a running jump or a slow push and theres no way anyone is going to be developing 89 tonnes of force with a hammer.

    Also, the risk of hitting stuff with a hammer is that youre going to peen things over, including the back of the taper. The 20mm rod we inserted into the arbor was threaded on the end so that both a shoulder and the thread was bearing on the arbor to try to disperse the load out as far as possible across the back of it.

  8. #8
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    3,828

    Default

    Quote Originally Posted by scottyd View Post
    Youre right, sometimes a hit is a good thing, but it only works because you can build up a given amount of energy before transfering it into the thing being pushed. Its just like getting a run up for a jump, rather than getting all that forward energy in one push, you build energy by running towards the place to jump. But the reality is that the force required to remove a taper is going to be the same whether you take a running jump or a slow push and theres no way anyone is going to be developing 89 tonnes of force with a hammer.
    I really doubt anywhere near 89 tones of force would have been needed if short sharp impacts had been used.

    Most people give up too soon when using impacts. Think about how many impacts a rattle gun generates before something often moves. I had to hit mine about 20 times before it even moved and then another 5-6 more after that to get it out. If we were to really magnify the contact surfaces between a plug and socket we would see a few higher points on each in contact with each other and the loosening is a question of breaking these so called "stiction" points. When using something like a press it tries to break them all at the same time where as when impacts are used it breaks the grip of a few % of the "stiction" points at each blow.

    A much more relevant comparison than a jump is pushing nail into a block of wood with a press versus using a hammer. I've demoed this in front of students a number of times whereby a 4" nail usually used required around 700 - 800 kg to drive it into a block of hardwood, yet I could drive that same nail into the same block with 1 kg hammer.

    Also, the risk of hitting stuff with a hammer is that youre going to peen things over, including the back of the taper. The 20mm rod we inserted into the arbor was threaded on the end so that both a shoulder and the thread was bearing on the arbor to try to disperse the load out as far as possible across the back of it.
    I agree damage can be a problem but there are very easy ways to protect metal parts being struck using hardwood blocks or a lead or copper faced hammer. OTOH a press is much better than a hammer for things like bearings because you cannot protect the surfaces in between the bearings and race.

  9. #9
    Join Date
    Aug 2014
    Location
    Queensland
    Posts
    18

    Default

    Thanks to all for the responses. Very much appreciated.

    I have found the engagement pin on the large gear. That was the part I had overlooked. The locknut came off easily after that.

    Does the end spacer pictured below also come off? When I try to remove it makes a sound off metal hitting metal. Could it be that it has worn a groove into the arbor or is it not meant to be removed?

    Also BobL and AnorakBob where do you apply the heat? from the inside with the door open? or from the front? Tried asking this is Bob's "i just bought a new mill" thread but it hasn't appeared. I am a compete newbie to using forums. Not really 100% sure what I am doing or even the etiquette. Hopefully I have got the second part right? I have given it a fair whack with a fairly big block hammer. Still no luck but will try again with the heat gun if I know where I should be heating.


    IMAG0206.jpg
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