Taper pin vs split pin
Bob Engelhardt
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
sta...@prolynx.com
One thing would be where you want your joint assembled in one position
and one position only. Kind of hard assembling a taper pinned joint
with the inner part 180 degrees out. Appearance would be another.
For most things they used to use taper pins, though, a roll pin will
work.
Stan
Robert Swinney
Bob Swinney
"Bob Engelhardt" <bobeng...@comcast.net> wrote in message news:hj766...@news4.newsguy.com...
dca...@krl.org
A spring pin has obviously some spring in it. So where a control arm
is secured to a shaft with a spring pin and the arm is moved in both
directions, the spring pin will wallow out. A taper pin especially
one with a threaded small end will not wallow out.
See Cub Cadet steering arm as an example of a control arm secured with
a spring pin.
See Ebay for people selling taper pin replacements for the Cub Cadet.
Dan
Ed Huntress
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
Jim Stewart
> "Bob Engelhardt" <bobeng...@comcast.net> wrote in message
> news:hj766...@news4.newsguy.com...
>> 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.
A taper pin in AL, subject to shock loads, will
flex and batter the walls until failure. Not a
pretty sight.
Ed Huntress
"Jim Stewart" <jste...@jkmicro.com> wrote in message
news:hj7i12$q4i$1...@news.eternal-september.org...
Sure. But that's not the pin's fault. That's an inappropriate use of a
pin -- any kind of pin of that size. The problem there is that the material
(aluminum) doesn't have sufficient compressive yield strength for the chosen
fastener/locator: the pin.
Since a steel pin has roughly 3X the stiffness (Young's Modulus) of the
aluminum, and many times its strength, it's probably a case of the aluminum
yielding locally.
--
Ed Huntress
Gunner Asch
The hole was reamed with a taper?
Gunner
The current Democratic party has lost its ideological basis for
existence.
- It is NOT fiscally responsible.
- It is NOT ethically honorable.
- It has started wars based on lies.
- It does not support the well-being of americans - only billionaires.
- It has suppresed constitutional guaranteed liberties.
- It has foisted a liar as president upon America.
- It has violated US national sovereignty in trade treaties.
- It has refused to enforce the national borders.
...It no longer has valid reasons to exist.
Lorad474
spaco
steering mechanism. The Torque applied to the place they were used
caused the metal in the holes to wear, leaving the pin loose and causing
an annoying amount of "slop" in the steering mechanism. A taper pin
totally solves the problem.
See: http://www.spaco.org/loose.htm
Actually, I see it as less work to use. The exact size of the tapered
hole isn't even important, as long as the taper pin isn't too short.
Pete Stanaitis
------------------
Steve Lusardi
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" <hunt...@optonline.net> wrote in message news:4b574207$0$22522$607e...@cv.net...
Steve Lusardi
welds in place. As Ed stated, they work extremely well if the loading isn't high. Higher loads require keys and key ways and then
if very high, splines are more appropriate. Pins were was once very common in punch card equipment, card punches, sorters and
collators.
Steve
"Gunner Asch" <gun...@lightspeed.net> wrote in message news:5oqel5h3or31it5m2...@4ax.com...
Ed Huntress
"Steve Lusardi" <steve...@lusardi.de> wrote in message
news:hj81e8$5j3$00$1...@news.t-online.com...
> 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
Yeah, the "falling out" is more theoretical than real. If you press a steel
pin into a steel hole with any force, even if it's tapered, it can stick
there like it's welded.
But, technically, even a locking taper can't take certain kinds of cyclic
forces without coming loose. Anyone with a B&S-taper milling machine, or
even a Morse or other "self-locking" taper, probably has had a tool drop out
at some time in their lives. Hopefully, it's been a rare experience for
those who have had it happen (I have).
I never did any real-world toolmaking but I studied the hell out of it
decades ago, when I covered tooling for magazines and then when I sold EDMs.
Once upon a time I knew more about tapered pins, much of which I've
forgotten. But the basic principles are there.
In any case, their purpose really is locating rather than retaining.
Straight pins and roll pins are for retaining.
--
Ed Huntress
David Billington
nomenclature in different parts of the world. In the UK I think I know
what a taper pin is but what are you referring to as a split pin (spring
pin), see http://www.ondrives.com/mechanical-dowel-spring-pins.html ,
they mention slotted and coiled spring pins (often referred to as spiral
pins here IIRC). I suspect it makes a difference. I've seen the slotted
spring pins fail but not the coiled, yet!. Taper cotters used on many
bikes with steel cranks in the US IIRC and the likes of MG midget
kingpin to lower trunnion, but they are cylindrical with a tapered flat.
British born, but lived in the US for 12 years, I'm glad I had UK
parents so made adapting back to the UK easy. Confusing for some in the
US though as some language differences are notable. Confused one of my
English teachers no end for a short while as I pronounced "schedule" the
English way.
Flash
very thorough and concise job.
I would like to add one application of taper pins which is not so common -
in fixing the wing-spars of some aircraft, a taper pin is used, with some
kind of keeper. Usually, the small end is threaeded, and a nut with washer
keeps it in place, thus allowing no slop or flex. There is an element of
shear involved here.
Flash
"Ed Huntress" <hunt...@optonline.net> wrote in message
news:4b574207$0$22522$607e...@cv.net...
>
oldjag
> 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
>
>
> > "Bob Engelhardt" <bobengelha...@comcast.net> wrote in messagenews:hj766...@news4.newsguy.com...
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!
dca...@krl.org
> 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.
>
> Ed Huntress
Morse tapers are designed to release. Jacobs tapers have less taper
and are designed to hold but can be released. I believe that taper
pins are designed to be harder to release than Jacobs tapers.
Standard taper pins have a taper of 1/4 inch per foot.
In my previous post, I mentioned taper pins with a threaded section on
the small end. My mistake. They do not exist. There are taper pins
with a threaded section on the big end so a nut can be used to pull
the pin. Sorry about that.
Dan
Ed Huntress
"Flash" <flash...@embarqmail.com> wrote in message
news:hj8keo$g83$1...@news.eternal-september.org...
> Ed, I admire your ability to describe this with clarity and precision. A
> very thorough and concise job.
>
> I would like to add one application of taper pins which is not so common -
> in fixing the wing-spars of some aircraft, a taper pin is used, with some
> kind of keeper. Usually, the small end is threaeded, and a nut with washer
> keeps it in place, thus allowing no slop or flex. There is an element of
> shear involved here.
>
> Flash
Thanks, Flash. Those tapered fasteners with the threaded small end are an
interesting case. Someone mentioned tie-rod ends, or some other suspension
part, that's tapered and held tight that same way. Once you put a screw on
the end you have something that's functionally a little different, but which
does have that property of generating a tight fit along the whole cone -- in
this case, with a preload that can be adjusted with the screw.
The refinement of tapered locating pins came along a little over a century
ago, when the art and science of precision toolmaking and gage making went
through a rapid period of development. It happens that I had to study that
work and that period to help write the 100th Anniversary Issue of _American
Machinist_, back in 1977, and since then it's been one of the most
interesting parts of the machine trades to me. There were a lot of brilliant
people who perfected the art, and then turned the whole thing into a
combination of art and science. There are few people I can talk to about
things like diamond pins, toolmaker's buttons, and toolmaker's faceplate
work. They don't believe that people could work to tenths, or even better,
in 1900. Or, they think I'm nuts to care about it. d8-)
--
Ed Huntress
Ed Huntress
"oldjag" <msmit...@comcast.net> wrote in message
news:46e5e261-fb12-4e44...@b2g2000yqi.googlegroups.com...
I love to see that kind of finesse in the mechanical details. I've never
worked on a Rolls-Royce, but I've been told by people who have that they
used to be -- maybe still are -- things of mechanical beauty like that.
Finesse is a great thing. Unfortunately, it's not cost-effective. <g>
--
Ed Huntress
Ed Huntress
<dca...@krl.org> wrote in message
news:cc061926-1ee6-4802...@l30g2000yqb.googlegroups.com...
> Ed Huntress
You were sort of right the first time! <g> I wouldn't call them "pins," but
there are tapered fasteners that are threaded on the small end. I have one
in my fastener junk box. I don't know what it was used for; I inherited the
junk box.
I don't think they were used the way we think of tapered pins, but that
concept has been used in various mechanical fasteners, where you need both
the tight fit of a taper and a preload to hold the thing in place, or to
hold parts together.
--
Ed Huntress
Bill McKee
All those counters in the mechanical cash registers and bank proof machines
were put together with taper pins. As well as a lot of the shift plates.
In years of working for NCR I only saw a couple pins come loose. Most
likely because someone did not set them forcefully enough. They keep parts
precisely aligned.
Jim Wilkins
http://www.archive.org/stream/locomotivebuildi00flanrich/locomotivebuildi00flanrich_djvu.txt
Also engine flywheels and propellors.
I've seen the propellor shaft for a nuclear sub on the lathe at the
Portsmouth naval shipyard. The prop end is a keyed taper and threads
just like the crank on my old B&S lawnmower engine, naturally MUCH
larger. However the thread pitch is about the same.
jsw
Bob Engelhardt
...
> To get the big picture, you have to consider four kinds of pins. ...
Thanks - nice explanation. (Your writing background coming to the
benefit of RCM'ers once again <G>.)
The background for my question as this: I had made slip rolls and
fastened the handle to the roll with a taper pin. My reasoning was that
I could get a better fit than _I_ could with a straight pin & avoid
wallowing out from a loose fit. But a split/spring/roll pin would have
been so much easier. Not nearly as good, I see now.
Thanks to all,
Bob