I've been on the lookout for a reasonably priced parallel test bar for certain lathe setup operations. I'd be happy with a cylindrical blank say 14" long as long as it had accurate centers ground on both ends. For some reason, 100% cylindrical test bars seem to be kind of rare. But lots with MT# taper ground on one side. OK, I can make that work too as long as the cylindrical section is long enough and I guess the MT will give me some added utility for different setups if I set it in my MT tailstock.
Basically I want to set up custom taper angles on my lathe compound using sine bar & gage blocks, items which I already have. In my mind this seems like a rapid way to get the compound orientated. I've done the DTI traversing across a known MT arbor shank. That works of course, but is also a bit fussy and one is always 'replicating' whatever that happened to be along with any errors as opposed to setting up from base [taper/foot] offset type standard taper dimensions.
So here is what I'm visualizing. Does this procedure make sense to you guys? Something like:
- put parallel test bar between centers, ensure headstock/tailstock centers aligned with various DTI measurements (which lathe should be to begin with anyway)
- set compound to zero protractor scribe line (just rough reference)
- loosen toolholder, set sine bar in tool holder & align so both lobes contact test bar simultaneously, tighten, zero reference established
- loosen compound, swivel rotate & use appropriate gage block stack under one sine bar lobe. Other lobe is contacting test bar, similar to angle setup in a mill vise.
- compound is now set to cut that taper angle & is repeatable. No coupon MT arbors were required. Also any desired angle within stack-up range should be achievable using method.
There seem to be lots of parallel bars like this on ebay claiming 0.0001" runout. Cheaper than I could make one to anything close to this accuracy. Any experience or feedback in this regard and/or my proposed methodology?
http://www.ebay.ca/itm/ETOOLS-3MT-1...=c2a0bfdd3ab34652ad56360073c9da0f&pid=100022&
Basically I want to set up custom taper angles on my lathe compound using sine bar & gage blocks, items which I already have. In my mind this seems like a rapid way to get the compound orientated. I've done the DTI traversing across a known MT arbor shank. That works of course, but is also a bit fussy and one is always 'replicating' whatever that happened to be along with any errors as opposed to setting up from base [taper/foot] offset type standard taper dimensions.
So here is what I'm visualizing. Does this procedure make sense to you guys? Something like:
- put parallel test bar between centers, ensure headstock/tailstock centers aligned with various DTI measurements (which lathe should be to begin with anyway)
- set compound to zero protractor scribe line (just rough reference)
- loosen toolholder, set sine bar in tool holder & align so both lobes contact test bar simultaneously, tighten, zero reference established
- loosen compound, swivel rotate & use appropriate gage block stack under one sine bar lobe. Other lobe is contacting test bar, similar to angle setup in a mill vise.
- compound is now set to cut that taper angle & is repeatable. No coupon MT arbors were required. Also any desired angle within stack-up range should be achievable using method.
There seem to be lots of parallel bars like this on ebay claiming 0.0001" runout. Cheaper than I could make one to anything close to this accuracy. Any experience or feedback in this regard and/or my proposed methodology?
http://www.ebay.ca/itm/ETOOLS-3MT-1...=c2a0bfdd3ab34652ad56360073c9da0f&pid=100022&