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Cone shaped end when facing on HF 7x14

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senoird

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#1
Just got my first metal lathe and after receiving a set of index cutters decided to try to face a piece of 5/8 aluminum rod. Ever time I face it there ends up being a slight cone rather than a flat end. I am brand new at metal working (moving from wood to metal) and am thinking its pushing back during the operation causing a cone. Is this common and how do I counter it. As far as I can see there is no axis lock on the X axis. I would appreciate any help/suggestions any of you can throw at me.
 

homebrewed

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#2
Hi Seniord,

You can try engaging the half-nuts before starting the facing operation. This usually works for me. If not, you may want to look into getting/making a carriage lock. Edit: if you lock the half-nuts, make sure the lead screw is disengaged -- you don't want the carriage advancing, just locked in place by the lead screw.

You also want to make sure that your gib screws are properly adjusted so there is minimal play. New machines of this type usually need some tweaking before they perform their best. You also want to set the tool height so the cutting tip is well centered. It usually is necessary to put shims underneath the tool to get it on-center....unless you have a quick-change tool post (QCTP).

BTW welcome to the forum!
 

senoird

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#3
Hi Seniord,

You can try engaging the half-nuts before starting the facing operation. This usually works for me. If not, you may want to look into getting/making a carriage lock. Edit: if you lock the half-nuts, make sure the lead screw is disengaged -- you don't want the carriage advancing, just locked in place by the lead screw.

You also want to make sure that your gib screws are properly adjusted so there is minimal play. New machines of this type usually need some tweaking before they perform their best. You also want to set the tool height so the cutting tip is well centered. It usually is necessary to put shims underneath the tool to get it on-center....unless you have a quick-change tool post (QCTP).

BTW welcome to the forum!
Thank you very much. I didnt realize there was a neutral setting for the lead screw. Put it in neutral and locked the half nut down and it worked perfectly. Thanks again.
 

benmychree

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#4
Its hard to imagine that a lathe would not have a carriage lock!
 

Janderso

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#5

homebrewed

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#6
Its hard to imagine that a lathe would not have a carriage lock!
Unfortunately, this class of lathe doesn't have a carriage lock as a standard feature. No tapered gibs, either :(. It also doesn't have a quick-change gearbox, but at least it DOES have gears and a lead screw for threading. The power feed just uses the highest gear ratio and is a bit too fast to get a really good finish. The stock gear-change setup doesn't permit larger gears so folks have made custom gear "banjos" to slow the feed down (see gadgetbuilder's fine-feed mod), or made an adapter to attach a low-speed motor to the lead screw. The low-speed motor approach looks to be a little simpler to me.
 

mlindholm

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#7
I did see you say locking the carriage via the leadscrew helped. Getting a cone shaped nub can also mean your tool is too high. You can use a small steel ruler, razor blade knife, or similar stiff piece of metal to confirm your tool is on-center to the work, by pinching it between the workpiece and your cutting tip. If it tips out at the top, you're too low. In, and you're too high.
 
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