How do I cut my MT2 Blanks, it's under 1 thou in the mill but 3 thou in lathe w/ adapter

[woodchucker]

Ran into a little problem with the MT2 blanks I bought, not with them, but how to cut them. My runout is under 1 thou in the mill. But my lathe has a MT3, so I need to use an adapter. But with the adapter I am consistently getting 3 thou runnout. I tried clocking it different, it still out. I could order a new adapter, but it too could be out. I could try grinding the adapter, but my grinder will not reach in, and it only accepts 1/8 shank points. It's an old Themac.
So looking for some advice that would work for me.

 

[Ianagos]

Seems odd that it’s only .001” in the mill but suddenly .003” in the lathe. I’d would check the taper in your lathe and the blue the taper and check the bore to see if contact is being made. Before you do that you might check the runout in the mill in a couple different clockings and make sure that .001” was not a fluke.

To determine whether it’s your spindle or not and if the previous methods don’t help you you can mark the high spot on the adaptor with a sharpie then remove it and clock it 90 degrees and see if the high spot follows the adaptor. If it does I’d say get a new one but if it stay mostly in the same place in relation to the spindle as you clock the adaptor around I’d say something is wrong with your spindle.

Hopefully you understood my mumble jumble of words. English is hard.

 

[woodchucker]

Seems odd that it’s only .001” in the mill but suddenly .003” in the lathe. I’d would check the taper in your lathe and the blue the taper and check the bore to see if contact is being made. Before you do that you might check the runout in the mill in a couple different clockings and make sure that .001” was not a fluke.

To determine whether it’s your spindle or not and if the previous methods don’t help you you can mark the high spot on the adaptor with a sharpie then remove it and clock it 90 degrees and see if the high spot follows the adaptor. If it does I’d say get a new one but if it stay mostly in the same place in relation to the spindle as you clock the adaptor around I’d say something is wrong with your spindle.

Hopefully you understood my mumble jumble of words. English is hard.

its not the lathe taper, it's the adapter. What are the chances of getting a better one? Or maybe a worse one. My mt3 dead center has under 1 though runout. So it's the adapter.

 

[benmychree]

Generally you use a soft center in the headstock so you can true it up with a turning tool id doing work where perfect running is important.

 

[woodchucker]

hmmm. simple. but won't the threads in the drawbar end induce some runnout? ..
just tried. I am out by about a thou by the drawbar, and 1.5 at the blank end.
Not sure how to read this. It's under 1 thou in the mill, all 5 are. 1.5 is usuable.
let me rough it down, and see how it does in the mill before I thread it.

 

[Ianagos]

Seems odd that it’s only .001” in the mill but suddenly .003” in the lathe. I’d would check the taper in your lathe and the blue the taper and check the bore to see if contact is being made. Before you do that you might check the runout in the mill in a couple different clockings and make sure that .001” was not a fluke.

To determine whether it’s your spindle or not and if the previous methods don’t help you you can mark the high spot on the adaptor with a sharpie then remove it and clock it 90 degrees and see if the high spot follows the adaptor. If it does I’d say get a new one but if it stay mostly in the same place in relation to the spindle as you clock the adaptor around I’d say something is wrong with your spindle.

Hopefully you understood my mumble jumble of words. English is hard.

its not the lathe taper, it's the adapter. What are the chances of getting a better one? Or maybe a worse one. My mt3 dead center has under 1 though runout. So it's the adapter.

Ah I understand then if you know it’s the adaptor I would just buy a decent quality one and surely it will be better. If it’s not return it.

 

[Tozguy]

Hopefully the MT3 taper in the lathe spindle runs true, but what if you insert the adapter and do a skim cut on the MT2 taper with a boring bar?
Give the adapter a couple of taps with a dead blow hammer and it should hold well enough in the spindle for the job.
I would expect that the adapter is soft enough to cut easily (at least the adapter I recut was).
Put an index mark on the adapter before taking it out of the spindle and that should do it.
Draw bar pressure should not override a good fitting MT taper.

 

[woodchucker]

I was thinking the amount of was not going to easily clean up with a boring bar. It's just such a little amount. I was thinking grinding.

Anyway, I did the first one using centers. The metal was much softer than I thought it would be. I was out less than b4, but was hoping for under 1. I settled for this one at 1.5 approx. I didn't put my tenths indicator on, just eyed it. I used the first for my boring head. I had already made a straight one, but wanted a second with a drawbar, it will get used on the mill, and the lathe as a taper offset in the tailstock. I was going to use it as a ball turner, but have nixed that for now.

 

[woodchucker]

Generally you use a soft center in the headstock so you can true it up with a turning tool id doing work where perfect running is important.

I wasn't sure if you meant a center 60degree or the adapter. I decided to use centers, it worked, not perfectly.
If you meant truing up the adapter, I'll have to try it. we are talking a small cut, under 1 thou I believe to offset the 3 thou. That's a very small cut. This is a tanged adapter, not an open rear. So taking too much will move the mt2 too far in.
Thanks for the idea, even if it wasn't what you meant, I got out of the "NEED TO USE THE ADAPTER" mode.