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Thread: Roll pins vs taper pins
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12th Feb 2014, 07:34 PM #16
pins
The series 1 Land Rover has a similar arrangement with a clevis pin . The damn thing wears and becomes sloppy where the pin goes through , eventually something breaks and that means no clutch . I usually replace the pin with a bolt and lock nut and so far this has worked Mike
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12th Feb 2014, 10:57 PM #17Diamond Member
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13th Feb 2014, 08:35 AM #18Senior Member
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Have you ever seen the damage that roll pins do when they break? Shear pins or bolts shear properly but the spring type steel of roll pins breaks into small pieces and often ends up jamming between the shaft and the other component.
I agree you need to be careful when changing components in machines and we do always take into account the forces applied and what the required mechanical protection is. Most of the changes have been an Agricultural machines that have clutches or belts or are hydraulically driven and that offers the overload protection. Once we even set up a bar 2m long with an old bag scales on the end and pulled until the clutch slipped to measure the torque and compare it with the original shear bolt design. Fortunately when everything flew apart the bits all missed me!!
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13th Feb 2014, 10:11 AM #19Pink 10EE owner
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13th Feb 2014, 10:29 AM #20Distracted Member
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13th Feb 2014, 04:23 PM #21Cba
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What exactly is a roll pin? I think the description is used to describe several quite different types of spring pins. They all have in common, that they are larger than the hole they are supposed to fit. See here: http://en.wikipedia.org/wiki/Spring_pin
Being spring pins, these are all made of springy and thus hard material such as hard bronze or hardenes stainless steel or simply spring steel.
I do not like spring pins used tranfer torque, if they break they often damage the softer parts they were supposed to hold together. I especially hate it when spring pins are abused as safety pins, for example on the leadscrews of cheap lathes. Safety pins should be plain pins and made of soft materials, inserted into reamed holes with sharp edges. Only this can guarantee a controlled and repeatable shear force. Hardened roll pins used as safety pins are unpredictable. Chris
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13th Feb 2014, 06:21 PM #22Most Valued Member
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Originally Posted by cba_melbourne;1747138
"Slotted spring pins are cylindrical pins rolled from a strip of material with a slot to allow the pin to have some flexibility during insertion. Slotted spring pins are also known as roll pins or "C" pins.
I don't see any mention of a coiled/spiral pin being referred to as a roll pin.
RobThe worst that can happen is you will fail.
But at least you tried.
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13th Feb 2014, 08:51 PM #23Senior Member
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Lots of modern automotive gearboxes use roll pins throughout the shift linkages....even old stuff uses em....just did a 50 year old bandsaw shift fork with one installed from standard, if shearing them is commonplace, I suggest, maybe remove the ham from the fist!
One issue now, can only seem to get cheap carp Chinese ones easily.
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13th Feb 2014, 10:47 PM #24
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14th Feb 2014, 09:53 AM #25Pink 10EE owner
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You could just drill the hole out round, turn up a pin that is a firm fit and loctite in...
With the 10EE, in the feedscrew, the knockout clutch was held to it by a taper pin, I made a new feed rod, drill a straight hole through it... Turned up a pin slightly oversize, drilled a hole through the pin, split the pin with a cutting disc on the dremel, inserted beautifully...
I do not have any taper pin reamers here, just like I do not have any woodruff cutters either, so if it seems sensible I modify the design to suit what tools I have on hand... Taper pins have their place, but I am not the biggest fan of them, they had their place 50 years ago, times have moved on since then...Gold, the colour of choice for the discerning person.
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14th Feb 2014, 10:44 AM #26Distracted Member
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What technology is better, glue? I am a fan of taper pins, though I don't yet have the means (reamers) to use them. I think the locking action of a taper is perfect for keeping a pin tight, without requiring very close tolerances and without being difficult to remove. One sharp tap and it pops free. A little wear won't matter for most things, and when it gets too deformed just ream it out a bit and replace the pin. What could be easier? One day I'm going to buy a couple of reamers and taper pin everything in sight.
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14th Feb 2014, 12:23 PM #27Most Valued Member
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A hardened steel taper pin has to be more solid than a roll pin of the same size, given one is hollow and one is not.
I think roll pins are used more commonly now as they are cheap to make, and do not require any special tools.
Just drill a hole and bang it in.
They do the job in low load situations, but I don't really like them.
I would use a bolt in preference every time, when any significant loading is going to occur.
Roll pins always remind me of Cotter pins in regard to durability. A throw away item.
RobThe worst that can happen is you will fail.
But at least you tried.
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14th Feb 2014, 02:12 PM #28
Maybe I missed something, what's wrong with tapered pins?..
Just because they have been used over a long time doesn't constitute a reason not to use them, quite the reverse, the fact that they have been used successfully over a long period is a very good reason to use them... I don't see roll pins or loctite as being an improvement.
Ray
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14th Feb 2014, 02:18 PM #29Golden Member
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Hi Brian,
Re "One sharp tap and it pops free", I wish it was so. I have recently had the rotten job of trying to drill out two taper pins from the power feed drive shaft of a Deckel FP1. No 'previous owner maintenance' was to blame for it being impossible to remove by driving them out - the taper pins had been untouched since new. And I am not the only one to have this problem - PM has many similar reports.
First point is that it can be difficult to determine which end of the pin is smaller, particularly if the pin is not easy to see, and has with domed ends, level with a chamfered hole. A measuring 'scope would have been perfect for the job.
With a suitable pin punch in good condition applied it to the small end of the pin, a sharp tap was delivered, then another - and a sharper tap. I think it was all over by the time a small flat appeared on the domed end of the pin, indicating that the end of the pin had spread a tiny bit and locked itself into the hole even tighter. Next a few more solid belts but no joy.
Plan B:
First, on both ends of the pin a small centre punch was carefully applied to get a mark as close to centre as possible.
Next a drill guide was made to keep the drill square to the shaft and lined up with the shaft axis - due to the restricted approach this guide could only be held by hand. On each end of the pin a cordless drill and a small bit was used to drill in slowly, checking alignment by eye as well as using the guide, but this was difficult with no end view possible, and very awkward to hold the guide with fingers.
MWF Drilling taper pin.jpg
Gradually increased drill size 'till the pin came out. Bummer! - drill did not go down the middle due user error + pin installed off axis (note the drill guide was made assuming the pin would be on-axis).
MWF Taper pin off centre .JPG
Fortunately I have been able to ream out the damaged hole to clean up reasonably.
Next, repeated the procedure for the next pin on the shaft.
This has tempered my enthusiasm for taper pins. They are great for securing precise alignment in bolted parts. In rotating parts the pins must be tight, and that can make removal difficult. When replacing the taper pins that I removed by drilling, the plan is to turn down the small ends a trifle for a short distance, so that if a firm hit spreads the end, the pin will not be locked into the hole.
For future reference with a recalcitrant pin, I would seriously consider making up a C shaped drill guide that locates on both ends of the pin before drilling.
That said, the FP1 has very nice treatment of taper pins in blind holes: they are threaded on the large end and fitted with a withdrawal nut, or tapped to allow a threaded rod and nut to be used. These removal aids are not fitted to pins in rotating parts, where the main job of the pin is not to come loose.
Finally, it is hard to know when you have tapped in a taper pin tight enough, but not too tight.
On many jobs, or if you don't have pins/reamer to hand, RC's recommendation for a nicely fitted parallel pin plus a spot of Loctite is the way to go.
Cheers,
Bill
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14th Feb 2014, 05:22 PM #30
At work we have 2 inch water valves of the Saunders type. They can get very hard to operate due to poor maintenance. The handles are held on to the shaft with a roll pin. Sometimes these pins shear when trying to turn the water off. 2 inch stream of water at about 5 bar pressure.
Dean
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