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Taper
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Good evening everyone,
Anyone else get a kick out of the Complimentary Small Plastic Ruler Metrology? So I'm just up from checking the taper on the B-4. I'm smaller at the tailstock end by .006. Guess I know what I'll be doing this weekend. Just for fun I checked with the calipers and the micrometer and the calipers were off by a thousandth on the actual dimension but the difference was the same. Dave |
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Hello Dave,
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What is the diameter of your test bar? R.T. :D --- In daltonlathes@..., "Dave" <dkirk_4@...> wrote:
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--- In daltonlathes@..., "R.T." <redlupmi2@...> wrote:
At the moment, the test bar diameter is .946. I'm using a piece of 12L14 steel since I only have a 5/8 piece of aluminum that's long enough. Last time I did this I started out with a 1" piece of aluminum and it was just under 1/2" by the time I was done! There is about 7" extending out the chuck, and I get some vibration cutting down the tailstock end of the test bar, so I'm wondering if maybe, due to the length, and there only being about two inches on the other side of the chuck jaws since the spindle ID is only 3/4, if the test bar is in there a little crooked. I think I should put some smaller diameter stock in there just so I have plenty through the spindle so I know it's in there straight, to see if I still come up with the same .006 taper before I go any furthur. Dave |
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Hello Dave,
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I would bet the bar is flexing causing the taper. Larger diameter is preferred, such as 2", can even be pipe or tubing. The material behind the chuck shouldn't matter as long as it is well secured. TIGHT in the chuck. Don't want the part rocking there either. Let's see if Dennis agrees. :o) R.T. :D The Notorious Alabama Dalton Gangster --- In daltonlathes@..., "Dave" <dkirk_4@...> wrote:
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¿ªÔÆÌåÓýAs a non machinist lurking in the background here, I wonder if
the taper would be the same if you cut from right to left and left to right. I
have the same problem with my Senica Falls 103 year old lathe which is very worn
and had been abused.
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Ed Stoller
New Fairfield, CT ?
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Hi Ed,
No, it wouldn't matter which direction you were cutting. The taper is a result of a changing distance between the tool point and the spindle axis. Dave, your chuck may not be a factor in your taper. If the test bar is tight and not moving in the jaws, a little clearance at the ends of the jaws wont matter. As others have mentioned, the test bar should fairly large in OD. I'm using a piece of 1 3/4" 6061. I think the journals are down to about 1.680 now with a slightly smaller relief in between. Yes, I can see a new chuck in your future.... :-) Your chuck is probably worn to a point where new jaws wouldn't help. Even if you got new jaws, it's my understanding that they would have to be ground to to match your chuck. I wonder if Dennis has a trick to "load" the jaws under tension so you could use a boring bar to true up your existing jaws. Jim --- In daltonlathes@..., "Ed stoller" <edstoller@...> wrote: taper would be the same if you cut from right to left and left to right. I have the same problem with my Senica Falls 103 year old lathe which is very worn and had been abused. chuck jaws. I can fit a .002 feeler gage in between the jaws and thework. Sooo, anybody know if there are jaws still available for aCushman, or is it time for a new chuck? |
Ed Stoller
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