Not really, the general rule is to not to have a stick out of more than 4-5X the diameter of the rod, the 5X is for more rigid machines. You do not describe the cutter you are using, but the DOC is a function of the nose radius and cutting edge profile/rake/edge, too shallow a depth/incorrect feed rate and you will get a finish like you have. My experience with with 5C collets, which is my primary used chuck is that they do not hold stock very rigid and they are prone to skew the work due to the nature of the 5C collet. I would use a standard chuck or an ER collet chuck. If you want to do light cuts and longer stock unsupported. I would use a larger diameter rod stock like aluminum and use a sharp cutting tool HSS or ground edge insert with the feed set appropriately for the material, and/or do a two collar test. You cannot cut a 1" steel bar out to 9" unsupported, it will deflect and the finish will be bad no matter what the material.
Do not induce bed twist in a new machine to compensate for other factors that are causing your problems. The first thing I would recommend is check the headstock alignment, as just about every 1236T/1340GT I have encountered was out of alignment, and most individuals were trying to twist the bed to compensate. Get a MT5 precision test bar or use Rollie's Dad's Lathe Headstock Alignment Method which works very well, and then you can do the two collar test. Be aware that lathes/work will flex, and the cutter DOC you read on a DRO/Dial will often be slightly off from what you measure. So even if you tail stock is perfectly aligned, you may have to do very small adjustment to get accuracy in the sub 0.001" range on work supported with the tail stock.
Lots of previous threads on this subject:
Hello every one. Got a question for the group. I just got my new lathe in finally and getting it all set up. After doing some measurements, what is an acceptable taper from tailstock to head stock on a normal turn, say.....along a 12" turn? Thanks
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I have an interesting issue with my PM-1340GT that I am trying to figure out. I put a 2”x12" bar in the chuck and performed a collar alignment test (with no tailstock). Took light cuts (.002") -- I then put a .0001" indicator on the carriage and ran the indicator over both collars -- I am off...
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