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HF 8x12 Lathe - 3 jaw chuck true up starting at .007 runout - need help
- Thread starter gorlosky
- Start date
- Joined
- Nov 27, 2012
- Messages
- 7,857
I agree with hermetic, what you are measuring at the back end of the jaws is irrelevant. You mentioned adjusting the chuck body to .0005", now if that's case, adjust to the jaws, don't worry about indicating the chuck body unless it is way out of round.
What is acceptable to you? If you want guaranteed under .002" TIR you'll need to get a Set-Tru/Adjust-Tru/Setrite type chuck that allows you to adjust TIR.
Like when I had my HF814, I had a Bison 5" 6-jaw Set-Tru chuck. These easily cost $1000+ & the 5" ones aren't commonly stocked so no discounts on them. And that's not including the backplate which they do not make for this style spindle. I was luckily to find mine used for $600, don't forget I only paid $360 for that lathe brand new from HF. A standard back plate won't work with these chucks so I had to make my own as shown on my thread here.
I loved that chuck & I have the same Bison 6-jaw Set-Tru chuck on my current lathe but in a 6.25" size. I can easily get my TIR down to .0002" measuring on my DTI which is less than what Bison guarantees but you have to pay the price. Fuerda makes a much affordable version now, $400 for a 5"
You can also make any chuck "adjustable" by slightly undersizing the register on the spindle or oversizing on the chuck. The play will allow you to adjust TIR. This is not generally recommended though as the chuck can slip out of round. I've done this with the 3 jaw chuck that came with my current lathe, I can get it down to .0005". But I don't use that chuck much other than for polishing & light work. Grinding the jaws would be the best solution.
What is acceptable to you? If you want guaranteed under .002" TIR you'll need to get a Set-Tru/Adjust-Tru/Setrite type chuck that allows you to adjust TIR.
Like when I had my HF814, I had a Bison 5" 6-jaw Set-Tru chuck. These easily cost $1000+ & the 5" ones aren't commonly stocked so no discounts on them. And that's not including the backplate which they do not make for this style spindle. I was luckily to find mine used for $600, don't forget I only paid $360 for that lathe brand new from HF. A standard back plate won't work with these chucks so I had to make my own as shown on my thread here.
I loved that chuck & I have the same Bison 6-jaw Set-Tru chuck on my current lathe but in a 6.25" size. I can easily get my TIR down to .0002" measuring on my DTI which is less than what Bison guarantees but you have to pay the price. Fuerda makes a much affordable version now, $400 for a 5"
You can also make any chuck "adjustable" by slightly undersizing the register on the spindle or oversizing on the chuck. The play will allow you to adjust TIR. This is not generally recommended though as the chuck can slip out of round. I've done this with the 3 jaw chuck that came with my current lathe, I can get it down to .0005". But I don't use that chuck much other than for polishing & light work. Grinding the jaws would be the best solution.
Thank you all for your patience and helpful thoughts. I did finally sand the pressure side of each jaws threads and there was roughness using 320 grit. I worked it down to .002, and like you all said, there is play in the scroll to shaft, so I will stop there. I'll use .001 shim stock to bring things in a tad closer to .000, but for now that will be good enough and work.
Thanks again.
Thanks again.
Make your chuck adjustable like a buck, i have done several and they work great. Turn the baking plate about -.010 under size, than drill and tap the chuck for the adjustment set screws ( i used 5/16" 24), also grind off the end in a surface grinder so the set screws wont dig in to the backing plate.
I went over to the Shars site:
https://www.shars.com/products/view/943/4quot_3_jaw_Self_Centering_Scroll_Lathe_Chucks_Solid_Jaws
And like some one mention earlier, .003 is typical for these low cost 3 jaw chucks, so I am glad I can get .002.
https://www.shars.com/products/view/943/4quot_3_jaw_Self_Centering_Scroll_Lathe_Chucks_Solid_Jaws
And like some one mention earlier, .003 is typical for these low cost 3 jaw chucks, so I am glad I can get .002.
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The part where you were showing the outside end of the jaw isn't a precision surface. How do the jaws look on the clamping surfaces? You can mount a dremel on the toolpost to true them up temporarily but they will drift off again as the chuck jaws wears on the clamping surfaces and the scroll.
At any rate, other than just knowing what to expect, it doesn't make that much difference. 3-jaw chucks just are not that accurate in general. They are for convenience. The workpiece will still turn round and on center. When you want repeatable accuracy, put on the 4-Jaw chucks and collets.
At any rate, other than just knowing what to expect, it doesn't make that much difference. 3-jaw chucks just are not that accurate in general. They are for convenience. The workpiece will still turn round and on center. When you want repeatable accuracy, put on the 4-Jaw chucks and collets.
I was under the impression the each jaw was to fit in only one particular slot on the chuck.
Thus you would have three options of where to start your insertion of jaw number 1.
I didn't see where you mentioned trying the setup in all possible positions.
Thus you would have three options of where to start your insertion of jaw number 1.
I didn't see where you mentioned trying the setup in all possible positions.
