Adjusting A Taper Bore

[f350ca]

As Chips and More suggested, be careful using a collet as a master. They are naturally sprung open to accept on size stock so the outside would rub in its open state.

Greg

 

[T Bredehoft]

Tom, how did you lap it?

I used first a wooden dowel, then when that had no effect a piece of 3/8 drill rod and some valve grinding compound. A little at a time, check with a blued collet, repeat until exhausted, start again later. not done yet, either.

 

[T Bredehoft]

If the tool is above or below center it will cut a parabola of revolution rather than a cone.

Thanks, John, I couldn't remember "parabola." I just knew it was no longer a cone.

 

[T Bredehoft]

Tom, how did you lap it?

I started with a 1/2" wooden dowel, then when it had no effect I switched to a 3/8 drill rod and valve grinding compound (the longer you use it the finer it gets) It took so long that I'm not done yet. Lap/rub a little, check with blued collet, repeat ad-tedium.

Edit: Stupid, watch what the computer does when you're not looking.

 

[John Hasler]

Hmmmm, I must check that as I altered the bit so it may now be off.
By golly you learn a lot on this forum.
Tom, how did you lap it?

When I lapped the MT3 that I bored into the tailstock ram of my old lathe I glued sandpaper to a male taper. The piece of sandpaper must be rectangular.

 

[Tozguy]

When setting up to cut an ER taper I used trig calculations and dial indicators to get the compound dead nuts on the specified angle.
When checking the fit after with blued collets there was variation from collet to collet. Seems like collets would not be good as gauges.
Also, it left me wondering if ER collets collapse parallel and whether there is an error bias to consider when cutting the taper (as Savarin asked in the original post).

 

[Mark_f]

When setting up to cut an ER taper I used trig calculations and dial indicators to get the compound dead nuts on the specified angle.
When checking the fit after with blued collets there was variation from collet to collet. Seems like collets would not be good as gauges.
Also, it left me wondering if ER collets collapse parallel and whether there is an error bias to consider when cutting the taper.

I agree. That is why I said I use your method as a backup to check the angle.
I never thought about the being on center thing though. I think that is why my last taper bore is off a little. We do learn a lot from one another on here.

 

[savarin]

Its bored, I used a protractor then snuck up on it.
I'm happy with the result so far.
Turning the nose down to cut the thread for the nut. I purchased that as my skills are no where that good enough.

 

[David VanNorman]

Usaing the collet on a piece of drill rod between centers to set the compound . You may want to try more than one collet but most likely you will find they are all pretty close .

 

[Tony Wells]

In theory the collets do collapse in a parallel fashion, but I would be surprised if in a free state the angle was exactly as stated. I don't use any ER series, but perhaps someone who does could answer the question of unconstrained angle by setting up a sine plate or bar and checking a couple out for us.