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Offset headstock measurement ?
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William Ayerst
开云体育Reading the project files ‘Edenstaal Cannon’ - page 1 talks about offsetting the headstock to attain a taper. I’ve tried this with some brass and so I’m broadly familiar with the idea, but actually measuring it is a mystery to me. The text reads:‘Place the faceplate on the lathe and mount the work between centres, driving with a lathe dog. Offset the headstock away from the tool post by 9/64” and turn the tapered portion of the barrel as illustrated’ How do I measure this 9/64” offset? From where?? Many thanks, |
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alf yahoo
开云体育I can't specifically address your numbers there, but I can see my way to working out the geometry first on paper. Personally I either remember back to high school geometry and when that fails me - it _has_ been 62 years - I go to google for geometric problem solving.alf, On Apr 22, 2020, at 07:52, William Ayerst <willayerst@...> wrote:
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William Ayerst
Thanks Alf - I'm a little confused as to what my datum point would be - presumably I could set a tool at the edge of the faced rod at one extreme end of the taper, and then rotate the headstock so the distance between the tool and the work is now 9/64" (i.e. 140 thou) - just wasn't sure that's what I needed!
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Alfred Fickensher
开云体育The point of a dead center inserted into the tailstock and the tailstock moved as far left as possible would (should, ought) give you the datum for measuring headstock offset from.alf, On Apr 22, 2020, at 08:29, William Ayerst <willayerst@...> wrote:
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If I am holding the barrel blank in my 3 or 4 jaw, I have excess material at the breech.? I wouldlet my tool touch the blank at the muzzle end and back the cross slice out 3.57 mm 3.55 or 3.6 easy marks on the handwheel.? Swing the headstock so the tool touches the muzzle end of the cannon blank and lock the headstock you should have your taper dialed in
Ed Samsen |
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Put a dead center in the spindle.
Clamp a machinists scale on top of a bit in the tool holder on the cross slide (make sure it is set to 90 degrees). Adjust the cross slide until an inch line meets the dead center point. Remove the locating pin and loosen the tightening bolt and rotate the headstock counterclockwise until you measure 9/64". Because the tip of the dead center will move in an arc you may need to move the cross slide slightly toward the headstock for an accurate measurement. Lock the headstock in place. |
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I think that there is probably a misprint in the directions. To turn a taper between centers I would offset the tail stock from the center line between the head stock and tail stock. I don’t have my uni out to look at it right now but I don’t remember unit having the centering scale at the end of the tail stock to measure how far off they are. My two large lathes have this scale. Have to confess though that I haven’t turned tapers between centers in about twenty years as I cheat and use taper attachment on one of the large lathes when needed.
Good luck, SSK |
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No misprint. The Unimat DB/SL HS offsets, the TS doesn't. The following is the correct procedure, per "bluerandonee":
Put a dead center in the spindle. Clamp a machinists scale on top of a bit in the tool holder on the cross slide (make sure it is set to 90 degrees). Adjust the cross slide until an inch line meets the dead center point. Remove the locating pin and loosen the tightening bolt and rotate the headstock counterclockwise until you measure 9/64". Because the tip of the dead center will move in an arc you may need to move the cross slide slightly toward the headstock for an accurate measurement. Lock the headstock in place. -----Original Message-----
I think that there is probably a misprint in the directions. To turn a taper between centers I would offset the tail stock from the center line between the head stock and tail stock. I don’t have my uni out to look at it right now but I don’t remember unit having the centering scale at the end of the tail stock to measure how far off they are. My two large lathes have this scale. Have to confess though that I haven’t turned tapers between centers in about twenty years as I cheat and use taper attachment on one of the large lathes when needed.
Good luck, SSK |
Bubba Kay
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