On Jan 20, 5:52*pm, "Steve Lusardi" wrote:
Ed,
That's a good explanation of the use of tapered pins, but as a user of tapered pins over many years I have to disagree with them
ever falling out. In point of fact, once they are set, they can be very difficult to remove. Also, another really big advantage
they have over other types of pins is that they do not remove as much shaft strength, as other types often cause shaft failure at
the drilled hole.
Steve

"Ed Huntress" wrote in ...

"Bob Engelhardt" wrote in ...
A taper pin is so much more work to use - is it that much better than a split pin (aka spring pin)? *Or, putting it another way,
in what circumstances would a split/spring pin be inadequate and a taper pin be required?

Thanks,
Bob

Roll pins (spring pins) are made to keep things from falling apart. Taper pins are made for precisely locating parts relative to
each other.

For example, a roll pin might be used to hold a flexible joint onto a shaft. A taper pin (or pairs of them, actually) might be
used to locate the sections of a multi-part stamping die on a common die plate.

There has been some inappropriate use of taper pins in the past. Today, there is some inappropriate use of roll pins. Roll pins
flex and have limited ability to locate. But their shear strength is adequate for many jobs that formerly depended upon straight
pins.

To get the big picture, you have to consider four kinds of pins. Straight pins are used like roll pins, only they're capable of
handling much greater shear loads. They might be used to hold a drill chuck onto a spindle, in a light-duty application. To keep
the pin from falling out and to prevent backlash, the pin might be a press fit into its hole.

A roll pin is a cheaper way to accomplish the same thing, with much less shear strength but with an easier press fit. They've
replaced straight pins in many production applications.

A taper pin should not be used to hold things together, without some kind of clamping or other locating to hold them in place. A
screw tapped alongside of the head of the taper pin, with the screw head overlapping the edge of the pin, is one way to
accomplish this. In much tool work, the pins are not subject to strong shear loads so they may hold without a clamp. But they
can slip out of their holes without a clamp.

The fourth kind of pin is just a further illustration of what the taper pin is about. It's a tapered diamond pin. It only
contacts the work along two lines, rather than a long the sides of a cone. It's used only for super-precision locating in gage
work, and in making master tooling that's used only to qualify the production tooling. The idea is that you can't get perfect
contact on each of any pair of tapered pins, but you can locate one tapered pin perfectly and then restrain motion relative to
that pin by locking the part along two lines that lie on the radius of an arc from the tapered pin.

I know, following that in words -- or my words -- can give you a headache. g If it's important, I'll try again. But the point
is that there are two ends of the scale in terms of locating precision, and roll pins are at the low end. But roll pins stay in
place and do the job well when all that's required is to keep parts from slipping apart.

--
Ed Huntress



I had a Saab 96 that used a taper pin to connect the ~15mm diam.
shifter shaft to the gearbox. In this application it had torsion and
longitudinal loads applied but it was sized properly for the loads and
worked great. What was neat was that both ends of the tapered pin had
an external thread - after sliding it into place, a nut on one side of
the shaft pulled it home and retained it. To remove the pin you just
took the nut off and put it on the opposite end and used it to pull
the pin out. Nice, and no trauma to the shaft or gearbox from hammer
blows to drive out a stuck pin!