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PM1340GT with a 3 jaw Pratt Burnerd 6" SETRITE
- Thread starter mksj
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- Aug 12, 2013
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Try doing it with all the adjustment screws backed out. Keep the holding bolts snugged hand tight. DTI to a high spot, tighten the adjustment screw at that spot to half the DTI, than back that screw out again. Spin the chuck, DTI, and go to the next high spot.
The snugged up bolts hold the chuck in position, and only one adjustment screw is in contact with the chuck at a time (while you are adjusting). Keeping the others backed out ensures that you are never fighting with one adjustment screw against another.
The brand I had (don't remember, probably Buck?) had all the adjustment screws at 90 degrees, which made it easier, but this method should still work.
I am glad you brought this up... I will be shopping for a set-true 3 jaw, and want to find one with adjustment screws at 90 degrees. I wonder if Buck holds a patent that makes the other manufacturers put there adjustments at different points?
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- Mar 21, 2013
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Coolidge: Not sure what you mean by "different"? My BTC on the SB and the Pratt have 4 adjustment screws spaced 90 deg. apart. Not any different than zeroing using four jaws really. I can't put it into words but I visualize a series of angles when the high spot doesn't fall on a 90 deg. vector and will go to the smallest angle and adjust according to how far off a 90 deg. vector I am. Probably makes no sense but I don't know how else to explain it. But I'm only letting tension off one screw and tightening the opposing one at any one time. I usually only have to do this a few times and I'm done.
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- Aug 12, 2013
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A quick google shows others complaining of similar issues, and it apparently is somewhat random. Bison makes some chucks with the 90 degree spacing, but other models from Bison set the two pairs of adjustment screws at like 70 degrees to each other. Some other manufacturers make chucks with only 3 adjustment screws.
Haven't tried the other arrangement, but I was very happy with the 90 degree version that I used before.
Bill, do you have a South Bend "zero adjust" chuck? What do you think? They look like 30% cheaper than PBA, Buck, or Bison.
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- Dec 18, 2013
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Correct my Bison SetTru adjusting screws are not at 90 degrees. This makes it way more complicated. Lets say the four set screws are numbered 1,2,3 and 4. You find that you have to loosen BOTH 1 and 3 and tighten BOTH 2 and 4, or you have to loosen 1 a little, 3 a bit more, tighten 2 a little and tighten 4 a bit more its really pretty annoying. I would not purchase another one of these Bison chucks its that annoying to me.
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- Mar 21, 2013
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Wow, thankfully, both of my chucks have the setscrews every 90 deg..
Tim: No, I don't have the South Bend zero adjust. I wasn't aware of it or it wasn't offered yet, but I ended up getting a 5" BTC (import) from a guy on Ebay who said it is similar in quality to Buck. All I know is when I adjust it for a specific diameter it repeats to thou or less.
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- Nov 27, 2012
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Very interesting, first time I've heard adjustable TIR chucks being quicker to adjust than a 4 jaw. I'm quicker adjusting the 4 jaw. I guess it might come down to what your more familiar with.
Another first time I've heard to back out the adjustment screws after dialing in. I prefer to leave them all tight cause if you leave them loose, it's easier for the chuck to get knocked out of round on heavy and/or interrupted cuts or a bump. But I don't use my Set-Tru function often to dial in every part. I dial it in for the lowest TIR so it has great repeatability on parts that are machined (which is why I don't use collets much in the lathe). I use my 4 jaw when I need to dial in a part for best accuracy.
As said the Bison 6.3" & 8" Set-Trus don't have the adjustment screws on 90° (not sure about the larger ones), like an X pattern. But my 5" Bison 6-jaw Set-Tru did have them at 90°. The placement has to do with the amount of pinions, the size out the adjustment screws, & the length of the chuck. The Bison Set-Trus that have large adjustment screws (M18), aren't clocked at 90deg, & have 3 pinions. The PB Set-Rites (up to 12") have 1 pinion & the adjusment screws are at 90°, I have no idea what size they use for the adjusment screws. The 6.5" (yes, 165mm, odd size) chuck on my super spacer has 3 pinions & the adjustment screws are at 90° but the set screws are much smaller than my Bison, like M8 or M10, I forget. I'd rather have them at 90° but it doesn't bother me as I'm used to the X placement now.
But one of the main differences between the Bison & PB adjustable chucks are that the PB Set-Rites are longer than the Bison Set-Trus. A 6.3" Bison is 2.677" long, a 6.3" PB Set-Rite is 2.88" long which gives more room for the adjustment screws to be placed at 90°. That's why the PBs weigh more than the Bisons. Although I don't like the additional hang out I'd still take a PB Set-Rite over the other common brands anytime. IIRC PB's Set-Rite design is Buck's old design, forget where I read that though.
I finally recently replaced my stock 3-jaw chuck (my least used chuck) with an inexpensive TMX semi-steel 6.3" Set-Tru. Figured it would just be a China copy of the Bison. Boy was I wrong & I sent that crap back the day after I received it. I went with the TMX cause it had 3 pinions which I prefer over 1 pinion. It had the adjustment screws off 90°. So now I have on the way a Fuerda (Gator) semi-steel adjustable but has only 1 pinion (their forged body version has 3 pinions). I believe the adjustment screws are at 90° but I'm not sure, I'll know later this week. I'm pretty happy with their 4-jaw, I should have went with Fuerda to begin with as my gut feeling told me to.
Another first time I've heard to back out the adjustment screws after dialing in. I prefer to leave them all tight cause if you leave them loose, it's easier for the chuck to get knocked out of round on heavy and/or interrupted cuts or a bump. But I don't use my Set-Tru function often to dial in every part. I dial it in for the lowest TIR so it has great repeatability on parts that are machined (which is why I don't use collets much in the lathe). I use my 4 jaw when I need to dial in a part for best accuracy.
As said the Bison 6.3" & 8" Set-Trus don't have the adjustment screws on 90° (not sure about the larger ones), like an X pattern. But my 5" Bison 6-jaw Set-Tru did have them at 90°. The placement has to do with the amount of pinions, the size out the adjustment screws, & the length of the chuck. The Bison Set-Trus that have large adjustment screws (M18), aren't clocked at 90deg, & have 3 pinions. The PB Set-Rites (up to 12") have 1 pinion & the adjusment screws are at 90°, I have no idea what size they use for the adjusment screws. The 6.5" (yes, 165mm, odd size) chuck on my super spacer has 3 pinions & the adjustment screws are at 90° but the set screws are much smaller than my Bison, like M8 or M10, I forget. I'd rather have them at 90° but it doesn't bother me as I'm used to the X placement now.
But one of the main differences between the Bison & PB adjustable chucks are that the PB Set-Rites are longer than the Bison Set-Trus. A 6.3" Bison is 2.677" long, a 6.3" PB Set-Rite is 2.88" long which gives more room for the adjustment screws to be placed at 90°. That's why the PBs weigh more than the Bisons. Although I don't like the additional hang out I'd still take a PB Set-Rite over the other common brands anytime. IIRC PB's Set-Rite design is Buck's old design, forget where I read that though.
I finally recently replaced my stock 3-jaw chuck (my least used chuck) with an inexpensive TMX semi-steel 6.3" Set-Tru. Figured it would just be a China copy of the Bison. Boy was I wrong & I sent that crap back the day after I received it. I went with the TMX cause it had 3 pinions which I prefer over 1 pinion. It had the adjustment screws off 90°. So now I have on the way a Fuerda (Gator) semi-steel adjustable but has only 1 pinion (their forged body version has 3 pinions). I believe the adjustment screws are at 90° but I'm not sure, I'll know later this week. I'm pretty happy with their 4-jaw, I should have went with Fuerda to begin with as my gut feeling told me to.
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- Nov 22, 2014
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I wonder if I might get everyone's opinion on a somewhat unrelated topic. Still talking about the 1340GT and tolerance, so if you stretch really hard it sorta goes in here. Question is "How important is a DRO to you?" I have more or less spent my budget (and then some) on this new machine, but I wanted something that would be good quality and last me a long time. I would like to purchase the DRO option, but that's REALLY stretching. I understand that every measurement can be made with manual instruments -- calipers, mics, etc, but the DRO seems like it would make things soooo much nicer until you get down to absolute finish dimensions. If I don't purchase the DRO with delivery of my new lathe, chances are that I will never purchase it. The money can be made available, I may just have to sleep on the couch for a while. ;-) I'll have to make a decision in the next day or two. Thoughts?
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- Nov 27, 2012
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To me, very important...now. You don't "need" a DRO just like you don't "need" a QCTP. It's one of those things that after having one, you wouldn't want to be without one. A DRO won't necessarily make your parts more accurate or make you a better machinist but it will make operations much faster & easier.
I purchased my current lathe without a DRO, mainly cause I wanted to install my own setup but also cause I wanted to get familiar with the lathe without a DRO first. When I took the conventional machining classes at the local CC with my brother (he needed the credits & I was his ride anyway), I specifically did not want to use the lathes & mills with DROs. If you aren't already, you should really get familar with using machines without DROs first. That way you aren't "useless" if one fails or anytime you need to use a machine without one.
IMO a DRO is much useful on a mill than on a lathe. I can get by on a lathe without a DRO no problem without cussing, but on a mill without a DRO, operations & keeping track of coordinates is extremely more time consuming compared to not having a DRO on a lathe.
I'd opt for the DRO if you can. But if you can't & really want some sort of DRO, you could always mount some of those iGaging scales. They're like long digital calipers with remote readouts. Not as great a true DRO with limited functionality & accuracy but they are very inexpensive.