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Basic questions about dual lathe toolholders
« on: August 09, 2012, 02:56:50 PM »
I’m getting closer & closer to actually cutting metal with my Denford ORAC lathe retrofit project and am seeking some basic tooling knowledge from ye grizzled CNC lathe vets. ;D

The ORAC is pretty small (8” swing) and has a small t-slot table on the carriage.  It didn’t come with the turret option unfortunately.  My plan is to bolt on an extension plate (5/8” x 4” x 10” ish steel) via the slots, install 1 AXA100 wedge QCTP in the normal location and either a 2nd identical QCTP on t’other end of the plate or make a parting blade holder to go on the end of the plate.

1)  Do dual QCTP’s make sense in the real world or is that a waste of money on such a small lathe?  I have one for the lathe now and would have to purchase a 2nd one if I go that route.

2)  Do the tool table & offset features in Mach work pretty well in preventing crashes with dual tool holders?  I can’t afford “real” lathe CAM at this time so I’ll be using the Wizards and doing some hand coding.  I’m still reading and trying to get my head around tool tables, tip radius and the like.

3)  Do any basic dual tool holder tips or hard earned lessons come to mind?  I have a lot to learn and any thoughts on the matter would be greatly appreciated.

Thanks!
Milton from Tennessee ya'll.

Offline Hood

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Re: Basic questions about dual lathe toolholders
« Reply #1 on: August 09, 2012, 03:16:59 PM »
1. You might struggle for room, I had a dual turret setup on the big lathe and eventually did away with it as it was always a worry when first running code as there were tools sticking out all over the place.

2. Tooltable and offsets work fine with the exception of you really only want to use all tools designated as Front OR Rear and not a mix. This part of Mach has never worked well so its best to avoid. The offsets etc will not stop you crashing, that is the operators responsibility and unless you have a very fancy CAM package then it wouldnt help you either.

3. Best advice is take it easy and do a dry run cutting air before you commit to cutting metal especially with dual turret/toolpost setups.

Hood
Re: Basic questions about dual lathe toolholders
« Reply #2 on: August 10, 2012, 10:23:32 AM »
Thanks Hood, I appreciate it.  Fortunately this little machine will be used for small jobs that won't have tight timelines so I should have time to proceed with caution and cut enough air to save huge crashes...hopefully.

Another question though...I totally forgot about the considerable amount of weight that an extension plate and extra QCTP/toolholder will add.  My planned extension plate will weigh about 7 lbs plus the weight of an extra AXA100 QCTP and a toolholder (5 or 6 lbs probably)  I had to use the stepper motors & driver I had on hand which are only about 220 in/oz torque.  When hooked up & running via the original Denford timing belt drives and ballscrews they "feel" amazingly strong (compared to my wimpy little Denford MicroMill) but now I'm worried about the added weight.  Not being a production machine the feedrates and acceleration can be slowed down to help but am I crazy to try this?  

Come to think about it, the optional Denford turret probably wasn't what one could call light though.
Milton from Tennessee ya'll.

Offline Hood

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Re: Basic questions about dual lathe toolholders
« Reply #3 on: August 10, 2012, 03:42:48 PM »
Easiest thing to do would be put a load of weight (bits of scrap or whatever) on the slide and see how it performs.
Hood
Re: Basic questions about dual lathe toolholders
« Reply #4 on: August 11, 2012, 09:39:01 AM »
That's way too easy! ;D

(Thanks, great idea....I'll try it.)
Milton from Tennessee ya'll.