Thread: Roll pins vs taper pins

Hi Bob,
A taper pin is easier to remove plus I have seen roll pins crack opposite the slit.
Lastly I prefer to put stuff back together as close to original as possible.
The last one is just me though.

Phil

Depends on the forces involved - a solid taper pin is going to be stronger than a hollow roll pin

Michael

Hi,

I agree with Steamwhisperer but I've used roll pins within roll pins to decrease the chance of them failing (this application was called for by the relevant technically authorities after single roll pins cracked in everyday use of the equipment); just locate the splits opposite to each other.

Ben.

ps it was originally a roll pin application

Originally Posted by bwal74

Hi,

I agree with Steamwhisperer but I've used roll pins within roll pins to decrease the chance of them failing (this application was called for by the relevant technically authorities after single roll pins cracked in everyday use of the equipment); just locate the splits opposite to each other.

Ben.

ps it was originally a roll pin application

Hi Ben,
I was going to click 'like' on this post but now I can't find the 'like' button.
Sooo "like"
Anyone know where it has gone or is this 'another' senior moment.

Phil

I wouldn't use a roll pin with a shearing motion like that.

Definitely a job for a taper pin.

The trouble with roll pins in this situation is that they will compress and deform, eventually failing from the two way shearing effect of the shaft and cylinder.

The other alternative is to use a bolt and lock nut rather than a roll pin (if clearance allows).

Rob

I really dislike roll pins. If they are used in an application like that they could well brake as described above. I feel they are a cheap alternative used by many manufacturers now and also the hole doesn't need to be as accurate in size so it is a cheaper manufacture. I have replaced many roll pins in machines with bolts, steel dowels or tapered pins. Roll pins have there place, like holding a collar on the end of a shaft, but I don't like to see them where they transmit any force or torque.

I would stay with the taper pins.

Roger

I would use the welder

Originally Posted by Burner

I have replaced many roll pins in machines with bolts, steel dowels or tapered pins. Roll pins have there place, like holding a collar on the end of a shaft, but I don't like to see them where they transmit any force or torque.

I understand your dislike but at the same time you have to be really careful doing that as the designer may have used a roll pin as a sacrificial element (like shear pins used to be designed into things) that will prevent greater damage further down the chain.

Michael

I have developed an immense dislike for roll pins. I am yet to remove a roll pin that behaves nicely when struck with a pin punch or drift. While I never replace with a new roll pin, I am wondering whether it is proper practice to only use them once! Conversely, nothing feels nicer than removing or installing a nice fitting taper pin. Such a nice positive fit. The leadscrew on my lathe is driven with a roll pin. I assume this is commonplace (at least amongst Chinese lathes) but over time it's becoming quite loose.

Anyway, I agree with what's been said about their use….

Simon

Originally Posted by simonl

The leadscrew on my lathe is driven with a roll pin. I assume this is commonplace (at least amongst Chinese lathes) but over time it's becoming quite loose.

Simon

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

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

Something similar happened here last week, except it was a roll pin that dropped out of the hand wheel drive coupling, after pulling it apart and recovering the roll pin with a magnet from the bottom of the saddle.. we replaced the roll pin with a tapered brass pin. Josh reamed it with a 49:1 tapered reamer, and then suddenly realized we couldn't make a tapered pin without the lathe.. So I hand turned a tapered brass pin on the wood lathe with a file and hand held chisels. Came out spot on ... well that's my opinion.

Ray

Originally Posted by RayG

Something similar happened here last week, except it was a roll pin that dropped out of the hand wheel drive coupling, after pulling it apart and recovering the roll pin with a magnet from the bottom of the saddle.. we replaced the roll pin with a tapered brass pin. Josh reamed it with a 49:1 tapered reamer, and then suddenly realized we couldn't make a tapered pin without the lathe.. So I hand turned a tapered brass pin on the wood lathe with a file and hand held chisels. Came out spot on ... well that's my opinion.

Ray

Is that a special taper Ray? Normal Imperial pins are 1:48 and metric 1:50.

Lex.

Originally Posted by Techo1

Is that a special taper Ray? Normal Imperial pins are 1:48 and metric 1:50.

Lex.

Yes it's one of those...

Ray