Unwanted taper

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Wino1442

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Hi all....Attached is a photo of piece I am turning down with the purpose of putting an MT2 on it. My problem is this: I am getting a .005" taper over 2 1/2 inches and I'm having trouble figuring out why. I have measured and calibrated numerous times. I have a test bar from Edge Technologies and when I put an indicator on that I end up only .001" off over 12 inches. The diameter is larger on the right and decreases moving to the left.
One thing that I see as I cut from right to left, using the power feed, is that as the tool makes contact with the workpiece the tool appears to push back very slightly. Before I engage the half-nut I pull back on the tool post to remove any back lash in the cross slide.
Oh! The other thing is this....the taper I'm getting doesn't always stay the same....sometimes when I make a pass I'll get no taper at all.
So I'm a little miffed as to what can be my problem...I make sure everything is tightened up and still end up with the problem.

I'd be more than happy to hear any ideas you all might have. Thanks!952401CE-A77C-4C52-B933-864D834405A9.jpeg
 
Carbide tools are not particularly free cutting, especially the type that you picture, for accurate cutting, I use a TPG uncoated insert that has a much sharper edge than the one shown, also cutting left to right is not something that is generally done, even much less done with the insert shown.
 
Sounds like your taper is opposite the usual way wear at the chuck. Does your tailstock quill move off center when you tighten the lock? Are the gibs on your carriage adjusted to optimum? Does your spindle deflect (probably would do opposite taper from what you have)? A misalignment on spindle "nod" could in theory give this type of taper, especially if the work climbs your tool as you approach the headstock.
 
I'd try a .001 cut with a SHARP HSS cutter to eliminate spring. The tailstock may not be preventing a tiny bit of spring.
 
Try pulling back hard on your cross slide before going in for your depth of cut
 
If the taper is due to bed wear a workaround is to use the compound only,keep the crosslide stationery. For example: if experiencing a +5 degree taper then set the compound to a -5 degrees and you shuld be at 0. Limited to the maximum travel of your compound.
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If you are making it an MT2, why concern yourself with taper? Just compensate for it in the cutting of the taper that will be there anyway.

I have found it easier to set up for cutting Morse tapers by setting up the tailstock by the taper per inch times the length of the stock divided by 2. Way easier to do it that way than to adjust the compound and then cut in 2" sections. If I had a taper attachment I would look into that but it is so dang easy to offset the tailstock using a dial indicator I don't know that I would do it any different.
 
Meta Key said:
Just to be certain, are you LOCKING the cross slide and the compound before you take a cut?

MK
Click to expand...
Does your cross slide/ compound have a lock? I have never seen that?
Robert
 
I had tried using a HSS cutter, but I was getting a lot of chatter and couldn't figure out how to get rid of it.
 
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