Turning Matching External/Internal Tapers

[rgsparber]

One of the many useful operations possible with a lathe is to cut tapers. These can be external or internal. Sometimes an external taper is cut and I want a matching internal taper. This article presents a procedure that requires no math or measuring to set up to cut the internal taper.

If you are interested, please see

https://rick.sparber.org/MatchingTapers.pdf

Your comments are welcome. All of us are smarter than any one of us.


Thanks,

Rick

[mklotz]

Very clever, Rick. Thanks.

Just to add to this discussion, not meant as a criticism of your method, here's how I've done it before.

Set the compound to track the angle of the rear side of the male taper.

Now mount a boring bar and, lathe running in reverse, cut the (male) taper on the back side of the workpiece.

The lathe is already configured to cut the female taper conventionally.

If your lathe has a chuck that threads onto the spindle, you need to be careful making the male cut. Too deep a cut and the chuck can unscrew. I've machined tapers this way but kept the cut to only a few thousandths per pass.

[rgsparber]

Very clever, Rick. Thanks.

Just to add to this discussion, not meant as a criticism of your method, here's how I've done it before.

Set the compound to track the angle of the rear side of the male taper.

Now mount a boring bar and, lathe running in reverse, cut the (male) taper on the back side of the workpiece.

The lathe is already configured to cut the female taper conventionally.

If your lathe has a chuck that threads onto the spindle, you need to be careful making the male cut. Too deep a cut and the chuck can unscrew. I've machined tapers this way but kept the cut to only a few thousandths per pass.

Marv,

I really like your approach! By not disturbing the compound, you get exactly the same taper for external and internal. Glad you warned about running in reverse with a screw-on chuck.

Thanks!

Rick

[olderdan]

Adding further to the taper turning subject, Joe Peiczynski has an excellent video on his channel here.

for setting the compound slide spot on first time for known tapers without a master.

[rgsparber]

Adding further to the taper turning subject, Joe Peiczynski has an excellent video on his channel here.

for setting the compound slide spot on first time for known tapers without a master.

Olderdan,

Joe Pie is one of the all-time master teachers. I love his use of applied mathematics in the shop. Very powerful.

I understand his angle setting method but I didn't catch how he sets the starting diameter.

Rick

[olderdan]

Olderdan,

Joe Pie is one of the all-time master teachers. I love his use of applied mathematics in the shop. Very powerful.

I understand his angle setting method but I didn't catch how he sets the starting diameter.

Rick

Hi Rick, not sure what you mean by a start dia, all Joe Pie is doing is measuring three sides of a triangle so angle must be correct. I know you get that. A start dia on the work can then be anything you want. If it has to be a size I usually turn a short parallel reference dia and run up the taper from there.

[rgsparber]

Joe Pie mentioned in passing that he was going to explain how to set the diameter at the entrance to the cone. Either it was super quick or he never explained it.

Rick

[mrehmus2]

The only caveat I see with this approach is that unless the cutting tool is on the axial center-line of the spindle, the taper cut will have a concave or convex bow in it. Or so I am told by one master machinist I know.
Also, you can use a line of chalk on the male taper to check the fit in the female taper. It should be smoothly wiped if the fit is good.

[olderdan]

Joe Pie mentioned in passing that he was going to explain how to set the diameter at the entrance to the cone. Either it was super quick or he never explained it.

Rick

Hi Rick, now I know what you are aiming for I only know two ways of doing that, One of the most difficult things to measure is the large end of an internal taper. I either make a gauge like this.


Or turn a short register on the front of the bore which can then be removed. I would be interested in an updated method from Joe Pie, maybe he would respond to a request.
Regards.

[mklotz]

Another way to measure a hole like the exit of an internal taper is to measure how far a precision tooling ball seats into the hole, then do a bit of mathematics to obtain the diameter of the hole.

The accuracy of this method depends heavily on the condition of the hole edge. There can be no chamfer or burs and the ball can not be pressed into the hole.

The associated math looks like this...

Let:

R = radius of tooling ball
H = distance ball descends into hole
D = diameter of hole

Then:

Z = R - H
A = 2 * ACS (Z/ R)
D = 2 * R * SIN (0.5*A)