Thread: Roll pins vs taper pins

> I have found situations where manufacturers have installed them where the knocking out side is impossible to get to without much greater disassembly

Taper pins used in such situations should have a tapped hole at the thicker end - to insert a screw for extraction. I was surprised even my cheap Chinese Sieg mill came with such tapered pins with threaded holes!

Nearly everything I work on has a taper pin somewhere on it.
Like a morse taper, cleanliness is paramount when installing them. I have found over the years that ensuring a clean, burr free tapered hole gives me no grief when it is removal time.
The hole 'must' be free from little ridges and chatter marks from the reamer which then requires not much more than a gentle tap with the 'appropriate' hammer.
Maybe it's method rather than design that can cause some consternation.
I have even resorted to making my own pins and always try to err on the big end being slightly bigger of course which is standard practise.
love 'em.

Phil

I believe that the pin holes are purposely drilled off center so that the parts cannot be put together 180deg out and the tapers in the parts not being correct.
I have only ever had 2 taper pins i could not get out-one that was probably 100 years old and one that there was no way of getting to the back side of. If you have ever had a roll pin break you will know the mess they can make, give me taper pins anyday. I even have a few taper reamers.....
If you cannot tap them out with a decent tap don't wallop them! If the part is small enough put it in a press or even make a J shaped puller that holds on to the back of the part and presses on the small end of the pin.

Ew

Originally Posted by Ueee

I believe that the pin holes are purposely drilled off center so that the parts cannot be put together 180deg out and the tapers in the parts not being correct.
Ew

Hi Ewan, You beat me to it.. Several of the gearbox tapered pins on the Deckel FP2LB are offset just like that, and for exactly that reason. They only go one way. The pins we have been making also have a turned flange on the end, so that you pull them out rather that hitting the small end.

We make them the same as Phil by the sounds of it.. with one end bigger than the other

Ray

This is the tapered pin type I was referring to in the earlier post.

IMG_0681.JPG

Ray

Yeah. Looks like a 1:49 taper.

Michael

Originally Posted by Michael G

Yeah. Looks like a 1:49 taper.

Michael

Ha ha.. This one is 1:50 I'm only set up to do 1:49 in brass on the precision wood lathe.. with a precision file of course..

Ray

Originally Posted by nearnexus

Is that supposed to act as a shear pin Simon ?

I don't think they're even any good at that.

On my Chinese lathe the leadscrew drive coupling had two cast steel tapered shear pins. These work well, but I replaced a broken one with a piece of GP hard bronze brazing rod and it shears nicely and does the same job.

Rob

The roll pin on my Chinese lathe was supposed to act as a shear pin.Instead an $80 shaft that drove the rack pinion become a sacrificial element to save the 20c roll pin.

Note to Chinese lathe owners with the lead screw covers,that the carriage can bind on the cover as it acts like a big sleeve near the end of its travel. Mine has a bit of brazing rod in there now.

Grahame

Originally Posted by Grahame Collins

The roll pin on my Chinese lathe was supposed to act as a shear pin.Instead an $80 shaft that drove the rack pinion become a sacrificial element to save the 20c roll pin.

Note to Chinese lathe owners with the lead screw covers,that the carriage can bind on the cover as it acts like a big sleeve near the end of its travel. Mine has a bit of brazing rod in there now.

Grahame

I've used hard bronze brazing rod as the shear pin for years. Works well. The original shear pin was cast steel taper pin.

Roll pins never shear cleanly. Bad thing to use.

Try oiling the outside of the spiral steel leadscrew cover and you should find it won't bind.

Mine work great. Excellent invention.

Also I use Loctite 767 lube on the leadscrew.

After 10 years use there's no discolouration in the lube, and the bronze half nuts are a good as new.

Rob

Originally Posted by simonl

I am yet to remove a roll pin that behaves nicely when struck with a pin punch or drift.
Simon

Someone showed me a safer way to remove a roll pin: Put in a solid pin that just fits inside, clamp over the roll pin with vice-grips (or even a vice) and it won't then collapse or break. Then use a tyre lever or whatever under the vice-grip jaws to lever it out.

It's taken me a long time to appreciate that a pin punch is not a drift. After smashing several of them in vain attempts to dislodge a stubborn pin, I realised that a strong, tapered drift is a better tool to just start it moving. Then when the end of the pin is flush with the surface, use the biggest pin punch that will fit to complete removal.

Jordan