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Removing taper pins

Greg Menke

Diamond
Joined
Feb 22, 2004
Location
Baltimore, MD, USA
I'm almost done removing the shifter handles from the lathe headstock- taper pins everywhere- how do I know? because I believe I've invariably driven each one of the beastly things in by the big end on the first try...

Anyhow, theres just one left, its driven in as a key along the shaft, locking the shifting arm in place. I've tried various combinations of heating the handle and trying to drive the shaft in both directions in an attempt to displace the pin enough to loosen things up.

In the below photo, its locking the middle handle to its shaft, which is at the top of the handle;
lathe5.jpg


Thankfully I can secure the other end of the shaft and apply force- but I've not suceeded in doing much and I don't want to push things too far.

I suppose the next step would be to drill out the pin, but I was hoping there might be another less destructive technique.

Thanks for any hints,

Gregm
 
Hi Greg,

There is no easy way with these buggers unless you can access them from the back.

Here's a test of your machining skills: drill and tap it so you can either get a slide hammer on it to knock it out in reverse, or, at least get a screw into it which you can then try to pry out by its head.

Maybe before you start pulling/prying, try freezing the axle then heating up the handle quickly - difference in temp might expand the handle enough to loosen some of its grip on the pin.
 
I suggest drilling it out. Start by center punching to establish the absolute best center location you can. Go in with a small drill (1/16, say) for a short distance to ensure that bigger drills to follow don't wander. Next, try to figure out what size the small end of the pin is likely to be, say from the other pins you successfully pulled and comparison with Machinery's Handbook. Pick a drill about 1/32 less in diameter and drill just a hair less than the depth of the handle so if you accidently break out of the side of the pin it won't show. I assume you can't get this thing onto a drill press or mill to do the drilling, so try to at least have a level and/or square to guide you while using a drill motor. Next, go in halfway with a drill somewhat smaller than the estimated pin diameter mid-depth. See if the pin has loosened. If not, start increasing the hole sizes and making more of a stepped hole. At some point the remains of the pin will just collapse and the handle will come off. If you have not buggered up the taper hole too badly, just put in a new pin. Otherwise, you can ream to the next bigger pin size (a perfect excuse to make a D-bit reamer), drill a straight hole and use a roll-pin, or think of a more rebuilder-friendly way to attach the handle.
 
Before attempting to extract the pin from the
front, be sure that the entire shaft it is
attached to cannot come out through the front
of the housing, by removing whatever it attaches
to inside.

I've never seen a *taper* pin used in this
fashion. The taper is so gradual that it
would be too long to do it's job in a setup
like that.

My suspicion is that it is simply a short axial
dowel pin (these are sometimes called "dutchmen")
designed to prevent the handle from turning
on the shaft. There may be another cross-pin
or the handle may have been put on from the
backside of the shaft, and it could be driven
off if the shaft were out and on the bench.

All this is pure conjecture on my part of
course, without being able to actually see
the parts in question.

A taper pin seems like an odd choice for
a manufacturer in that application, and I've
found that often I've been suprised at how
sensible and serviceable manufactures tended
to make their designs, on tools of that vintage.

Jim
 
Greg,
Seems to me the easiest way out of this pickle would be to grind it flush, prick punch the center of the pin and drill it out larger for either a roll pin or even fancier tap for a set screw (two as a lock would be even more fancy than that).

jack
 
I am guessing that the pin is a taper since all the other ones have been (the head of the pin is visible at 180 degrees on the joint between the shaft and top of the handle). There was another taper pin through the diameter of the shaft, extending across the width of the handle, locking the handle even more firmly- I pulled that one in the usual way by first driving in the big end before realizing it and switching ends.

I'll try the drill & tap for a screw to extract first and if that strips out, then I'll drill out the pin.

There is a considerable amount of machinery on the shaft in question inside this part of the headstock, which also involves most of the other components in there, so I'm reluctant to pull everything apart. The whole thing weighs something like 150lbs. So I'm kind of stuck with it sitting on the workbench with me periodically grumbling at it.

Thanks everyone.


Gregm
 
I would lean towards what Jom Rozen had to say. It would seem odd that the manufacturer put a "taper pin" in place of a key. Seems more likely to me that this pin is just a straight pin (since you already drove out a cross taper pin)to take the brunt of the force off of the cross taper pin and that the shaft is possibly rusted in place. Try putting something like a small 2 jaw puller on the arm and see if the arm doesn't move. Again, this is not an application for a taper pin.
 
If the back is not easily obtained, I'd soak in Kroil for a day, grind thru the case hadn'g., drill/tap and use a slide hammer.

"AND"- install a pull pin on re-assembly- Jerald
 
It's hard to tell but looks like the pin is slightly above the surface of the mating parts.

If so you might try welding a threaded rod onto the pin with your smallest o/a tip and then gently tapping it out with the slide hammer .. Good luck !

edited to add:

The expansion and subsequent contraction of the pin might also help break the bond.
 
my $.02
Could this be similar to a pivot pin on a saginaw tilt steering column?
If so, perhaps you could drill and tap a hole of the proper size (neighborhood of 8-32) in the pin, THEN s-l-o-l-y EXTRACT the pin with gentle, steady extraction force.
The tool is basically similar to a steering wheel puller. Lisle makes one (not so great but $7) and there is a company that makes a really good 2-diameter type for around $30. OTC is there name, here is the link.
http://www.skywaytools.com/autopg1.html
It is a "Saginaw tilt-steering pin extractor"
In any case, 8-32 is probably much to big for the taper pine, but perhaps you could use it to loosen the shaft. Good luck!
 
If that IS a taper pin, if you can move it AT ALL, it will come right out with the handle.

Some possibilities. (neither of first 2 at all likely IMO).

1) it is big end in. If so (totally crazy, of course) the handle would pull right off, because it would be loosening off the pin as it moved.

2) it is big end out...if so , it would pull out with the handle. But it will likely fight, soak it in PBBlaster etc.

3) it's a straight pin......in which case nothing at all is holding it in except friction, so pull the handle off as usual. soak it first.

Any way it works, no problem.

It ain't made of self-swelling unobtanium.....they meant it to be removable.
 
I agree a taper pin doesn't make loads of sense in this application... OTOH, the head is slightly rounded and protrudes just like the big ends of the taper pins do. As far as I can tell it does not extend the thickness of the handle casting, it certainly doesn't protrude past it.

I did get the handle to move a little- confirmed by sighting thru the hole I pulled the cross pin from. But that look more force than I was really comfy applying; I slid the shaft out by 5/16" or so and put a screwdriver shaft between the handle and the headstock casing, butted a brass rod on the end of the shaft and started banging away on the rod with a hammer. I got the tiniest bit of movement and that was it. After shifting things around, I banged it back into place, no movement of the pin was apparent.

If I get home at a reasonable hour tonight I'll give the drill & tap approach a try.

The other 2 handles came off with very little persuasion, so I don't think its substantially a rust issue. I'm going to have to get a couple pullers one of these days...

Gregm
 
It looks pretty clean, but is there a set screw hidden under the paint/gunk? It seems like overkill, having a round key, a cross pin, and a set screw, but I can't remember having seen a key in this kind of application without a set screw before. Of course, I haven't seen a lot of round keys, either...

Even if the others were easy to get off, penetrating oil seems like a good idea here, to see if you can get it off with as little brute force as possible.

Andrew
 
Greg, something doesn't add up. If it's
a taper pin, the large end would have to
be on the outside, right?

Which means that the taper is in the direction
such that if that were the only retention,
it *should* just pull right off. The pin
should be able to slide past the part of the
hole reamed in the handle itself.

I think there's got to be something else
holding that handle to the shaft.

Jim
 
It looks as if its a factory feature, there is no obvious sign anyone has been into the guts of the headstock- just the usual indications of knuckle-dragging troglodytes bashing stuff up on the carriage.

I'll hit the top of that handle with a wire-wheel tonight. I'm pretty sure there is no setscrew because theres no room for one, unless its pretty small and covered over with paint. But after the torch treatments, the paint is pretty well all gone and theres no sign I've found of a divot where a setscrew might be hiding.

I agree there may well be something else holding things together given the fairly assertive persuasion I gave it last night. Maybe the wire-wheel will bring something to light...

Gregm
 
Greg, if I were designing that, I would make
the the three shafts visible all to the same
diamter where they pass though the casting.

Then I would retain the handle on the middle
one by putting a larger diameter boss on the
end of the shaft, and slip the handle on from
the backside before it was installed in the
headstock.

The handle would have a stepped hole in it,
larger in the front than in the back.

Is there any way you could slip something
in behind the handle to measure it's diameter
as it enters the casting?

You may be trying to pull it off over the
larger diameter flange on the end of the shaft.

Jim
 
I have an old apron hand wheel in my junk box (from the teens or twenties) with the B&S taper pin still seated in the tapered groove. So it is possible to remove this type of part/key config as one.
 
I got the handle off. The key pin was straight and soft, extending maybe half the thickness of the handle. I extracted it by drilling, tapping and pulling with a claw hammer- it came out easy. I didn't tear up the pin, so I imagine I'll stick it back in, leaving the threads available for the next sucker.

The handle is a tight press fit, no setscrews or any other locking features. I teased it off with a brass drift against the shaft and sucessively thicker shims between the handle and headstock casting.

The shaft is thicker on the casting side, the handle mounting on a turned down section and butting up onto the shoulder. At the moment, I think I'll reassemble after loosening up the fit a little- perhaps I can ream the key hole for a tighter pin if necessary.

Gregm
 
Greg:

Interesting use of claw hammer to get that pin out !

Guess on reassembly, you could just drive in a nail using the same hammer. Just joking !!

Seriously, I would not relieve the hole nor the shaft to make reassembly easier - you will just end up with a handle that will never stay tight. I am sure that when this machine was built, this was a snug slip fit that at most might have required a light tap with a soft face hammer.

Lightly clean up ( do not polish ) the mating surfaces with Scotch brite and oil. Remove any burrs that may be around the pin hole. Oil them up and slowly work the handle back on by swinging thru a small arc. Hammer not required ! You may need to do this in small increments, removing and replenishing the oil until you have full engagement. Do this now as part of the clean up before painting.

Have used this procedure many times on the old machines I have refurbed.

Jim C.
 








 
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