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| Making an accurate spindle with an innacurate chuck. |
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| PekkaNF:
Looking your first picture...do you have a undercut at the end of step? That shoulder on the motor shaft is crisp and if it leans against burr or such it might prevent even very well fitting collar to sit straight. Micrometer blue would give you an idication where it is bearing. Just a tought. My experience says that you really need a some type of fixed steady and to tweak the bar straight/consentric on the four jaw... PekkaNF |
| AdeV:
--- Quote from: S. Heslop on November 21, 2013, 07:12:08 AM ---It's made from 5 inch diameter EN8 steel. It took me two days to saw through it! I didn't imagine such metal would warp. So I took the chuck off and measured the runout on the backplate and it was about 0.02mm, which was a fair bit. So I refaced it, put the chuck back on, and chucked something in the jaws... ...and now the bar wobbles 0.37mm over 90mm! That might be the result of my stupid grinding attempt. I'd say lesson learned but I think my only option now would be to try grind the jaws again. Or I could try reversing them to see if that improves any. --- End quote --- Can you run a dial gauge against the chuck body to see if that's running true? May as well eliminate the obvious first... 2nd, yes, reverse the jaws & see if that makes a difference. You can always buy new jaws if you've stuffed this set up. Another thing to check, is there any discernible "wobble" of the jaws when they are not clamped on something? You should probably check the headstock alignment as well; I believe this can by checked between centres - google "rollie's dad's method" for the easy way to do it. |
| S. Heslop:
--- Quote from: PekkaNF on November 21, 2013, 08:46:26 AM ---Looking your first picture...do you have a undercut at the end of step? That shoulder on the motor shaft is crisp and if it leans against burr or such it might prevent even very well fitting collar to sit straight. Micrometer blue would give you an idication where it is bearing. Just a tought. My experience says that you really need a some type of fixed steady and to tweak the bar straight/consentric on the four jaw... PekkaNF --- End quote --- There's a considerable undercut on the motor's spindle, and a slight one on the spindle I made, but I should maybe try the blue idea. I might've mucked up the other shoulders and it's catching somewhere else before those shoulders mate. I have ordered a steady but it might take a while to arrive. --- Quote from: AdeV on November 21, 2013, 08:58:28 AM ---Can you run a dial gauge against the chuck body to see if that's running true? May as well eliminate the obvious first... 2nd, yes, reverse the jaws & see if that makes a difference. You can always buy new jaws if you've stuffed this set up. Another thing to check, is there any discernible "wobble" of the jaws when they are not clamped on something? You should probably check the headstock alignment as well; I believe this can by checked between centres - google "rollie's dad's method" for the easy way to do it. --- End quote --- Just checked the face of the chuck and the wobble is pretty huge. With the jaws in place I could only turn it about 40 degrees but the dial moved about 0.15mm in that small arc. I then checked the backplate face (it overhangs a bit so I can check without removing the chuck) and thats still running perfect. I dont think headstock alignment should be a problem for this though, any misalignment would just lead to a tapered shoulder on the spindle. The jaws themselves are very loose in the chuck body's tracks. I guess I just bought a rubbish chuck! |
| lordedmond:
Simon is the chuck sitting correctly on the back plate i.e. is the correct face in contact with the back plate? have you got the spigot on the backplate to long which will not allow it to sit down correctly on its mounting flange have you tried to blue the back of the chuck register to check for bumps Stuart |
| S. Heslop:
--- Quote from: lordedmond on November 21, 2013, 09:59:49 AM ---Simon is the chuck sitting correctly on the back plate i.e. is the correct face in contact with the back plate? have you got the spigot on the backplate to long which will not allow it to sit down correctly on its mounting flange have you tried to blue the back of the chuck register to check for bumps Stuart --- End quote --- I just checked and yeah it seems to be contacting the back plate fine. With the chuck off the backplate I decided to get out my surface plate(of glass) and i'm getting the same measurement from that. |
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