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Thread: Hercus 9 Spindle Lock
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22nd Dec 2017, 01:19 PM #1
Hercus 9 Spindle Lock
The subject of how to best lock the spindle so you can undo a stubborn chuck comes up quite often. I purchased a model AR with teeth missing on the bull gear and the back gear, probably due to the previous owner using the back gear to lock the spindle and giving the chuck a good whack. I guess we have all done it.......Anyway, I have come up with a simple method that seems to work and puts minimal strain on things. I came up with this idea, but I would not be surprised if I'm not the first one, so please don't think I am claiming originality. I'm putting it up on the hope that others may find it useful, and/or make some improvements, which we can all benefit from.
The 'too'l is made from 4mm steel plate, thick enough to fit between the bull wheel and it's neighbouring gear. The plate has a slot cut in it to fit around the casting in the bull wheel. The tool fits around this casting and stops the bull wheel from rotating when the tool fouls with the headstock casting. Yes, this is a bit rough on the casting, but I use a piece of wood to soften the impact on the paint work - which seems to work OK for me. I have a 1943 model C, which has plain bearings, so the headstock casting is different to my AR - the tool works fine on both machines. I guess the photos do a better job of telling you how it works than my words do.
I have also attached a drawing of the tool. I originally used 6mm plate because it is a better fit, but the slot fouled with the spring steel holding the bull wheel locking plug, so I milled a recess in the plate to accommodate the spring steel part. Again, you can see this in the photo, but I reckon 4mm plate would solve this problem, without the need to mill anything. I'm sure that if you give this a go, you will soon work out your own version of the dimensions.
Spindle lock 1.jpg
Spindle lock 2.jpg
Spindle lock 3.jpgSpindle lock 3A.jpg
Hercus spindle lock plate.pdf
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22nd Dec 2017, 07:22 PM #2Most Valued Member
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Not trying to negate what you have done, but take care with how much force you use as you may run the risk of cracking the casting that the bull gear pin goes through if your tool moves.
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22nd Dec 2017, 08:05 PM #3
Interesting point. You would need a lot of force (and/or shock loading) to break the bull gear casting. Certainly possible. Trouble is, what is the the more robust alternative spindle locking method that would cope with the force that would break the bull wheel? Not arguing, really honest question.
I've seen some gadgets that grip the end of the spindle at the tumbler gear end, but that puts the torque through the bull gear pin.
It might have been nice if Mr Hercus had built in a locking pin into the design around the bull wheel. Maybe there is an opportunity to retro fit a pin like this.
Sent from my SM-G955F using Tapatalk
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23rd Dec 2017, 01:19 PM #4Most Valued Member
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You may have interpreted what I said incorrectly.
The casting where the bull gear pin goes through may crack or break if your locking plate moves.
I was not referring to the bull gear casting cracking.
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