What type of pin is this?

Some sort of shear pin from my milling machine, anyone know it's name?

Thanks,

Edited By Chris Denton on 29/09/2014 12:02:59

Looks to be a variation to a standard roll pin....

You could replace it with a piece of brass if the shear forces are not too great.....

Why has it broke? What did you do/what happened for it to break?

Never seen a pin like that, looks pretty neat!

A very common type of Roll Pin, often used in instruments to keep collars in place and also used where there are plastic parts. A bother to remove and I use a stepped punch specially made for each size I deal with.

Clive

It was on the drive shaft on a milling machine. The handle from the X axis hit a piece of wood that protects the Z axis DRO from splashes. Usually it just knocks it out of the way but this time it didn't!

Yes it was a right pain to remove, I'll probably just use a standard roll pin, would this be ok?

> Yes it was a right pain to remove, I'll probably just use a standard roll pin, would this be ok?

It did it's job, what would have broken if you had used a solid pin?

Neil

I'm meaning these:

http://s689.photobucket.com/user/richardtomes/media/rollpin.jpg.html

Hi Chris Denton

I recently acquired some tools that included a set of these: **LINK** they were used by a family relative now passed on. He was a skilled gunsmith.

From the US Lyman roll Pin punches. Each one has a small pip on the end to engage the hole on the roll pin and keep it centred. They work very well. In the past I have used plain flat ended engineers punches, most of the time they work fine however the locating pip on these punches and the slightly recessed step on the end makes them far easier to use than plain punches, and they do not mar the roll pin as they are correctly centred.

Other manufacturers make them as well. or make your own from silver steel.

Regards
john

My opinion? No! It is a sacrificial pin and is designed to shear ....I'd recommend you use brass....defo not Silver Steel.....

Look at it this way, if the pin doesnt break, something else will ! .....and it could be expensive and could contribute to you being injured....

Your call....

Edited By John Rudd on 29/09/2014 16:06:43

Most shear pins I have come across were Aluminium and very soft! The end having been knurled with a straight knurl to make a tight fit. Emco Lathes use an Aluminium pin on the leadscrew on the Maximat 11.I would not use a steel or brass roll pin on any drive shaft as a safety device.

Clive

Ok, rather than turning this into a pissing contest as to who's advice is best, I'll leave it to the op to make his own mind up.....

Having 40 years experience in heavy engineering doesnt seem to count for much these, as there are too many arm chair experts...

This one of the reasons I dont post much....

Admin, feel free to delete my account and posts......

Edited By John Rudd on 29/09/2014 17:56:41

I may as well throw my oar in.

If the function of the OPs pin in his picture was as a shear pin then it not a well made/designed machine. The pin shown is quite hard steel, possibly spring steel or maybe stainless. Unless both parts of the drive that the pin passes through are hardened the odds are they will be damaged when the pin shears. On reflection since the pin shown has not sheared then maybe it is NOT a shear pin after all.

Aluminium or copper are probably far more suitable, brass might be ok too.

Clive, do you have a punch for those pins that are 1mm diameter? I struggled to remove one last week. At least the good thing is that they are 'sprung' so reusable and self locking.

Ian P.

Well Mr. Rudd, that is as good an example of someone spitting out their dummy as I have seen in a long time. I have no doubt that the chap WILL make up his own mind anyway, and what has HEAVY engineering got to do with hobby engineering ???

Cheers Derek.

There only seem to be two opinions here:

1. If its a shear pin, it should be replaced by a shear pin.
2. If it is just a roll pin, use a roll pin but be aware they can be tricky.

I can't see any one-upmanship of major disagreement going on?

Neil

FWIW experience with car doors has shown me that roll pins can shear for reasons not to do with excessive torque, but fretting corrosion and wear at the joint line.

Neil, regards the car door roll pins, when I look at the failure it seems to me that they have, 'Twisted' and broken.

Ian P, I make up a punch by drilling a bit of bar and putting a short hard pin the same diameter in the hole and punch it through. Always fit a new one, never replace the old one. Starting them in the hole can also be a pain.

Clive

Just to futher stoke the fires..

I often see shear pins in outboard motors...as sacrificial between prop..and gearbox shaft.

These use a ccopper alloy..which I think is brass..it matches workshop properties of brass..

I say maybe brass since brass is not a material I would choose for salt water...

But the shear strength is comparable so..and colour isn't bronze..but still. .

To the point ..

brass is used as a sacrificial component between ss and the plastic of the prop...

I have seen steel.. ( notched)..bronze and brass shear components...

I have not seen ali but thats my loss..

Still keen to learn.

Btw..looks like a roll pin to me..I hope those two funtions weren't combined but it might be..again still keen to learn. ..

Clive

Our experiences of these pins differs. I find them easy install than parallel pins mainly because they have a slight taper lead and hold themselves in the sleeve, also they stay in place if one part needs moving to align the holes.

Whenever I have made a drift to press them out I have turned a spigot on the end of a bar, drilling up the end especially if the drift is hard steel sounds like hard work.

The picture shows some 1.4mm diameter pins (shafts are 4mm). I have also seen some a bit smaller. maybe 1.2mm (I must have imagined the the 1mm ones), These are in some Japanese camera equipment and are not magnetic.

I see no reason not to re-use this springy roll pins and I would not like to try and source small quantities in the UK.

Ian P

If the roll pin is definitely an original fitment I would be surprised if it was intended to shear, as previously mentioned a hardened roll pin can make a mess when it shears. As it has sheared I think I would replace with a soft material and if nuisance shearing occurs work up to tougher materials or larger size. Some shear pins are steel but waisted so a weak point is defined. The waisted section can be increased in diameter until nuisance breakage does not occur but it is still the weak point that we want to break first.

Mike

As for shear pins, I used to have to work on big stuff (snow ploughs etc.) and these had shear pins in the plough drive shafts. These pins are solid steel with a head at one end looking like a clevis pin on steroids with a machined annular groove at the shear point to provide a weak point in the pin. Try google for the term "shear pin" and look at the pictures! Brass, copper, steel - it matters little what you use as long as it will shear before deforming the associated parts and at the correct shear load. i suppose you also want it to shear clean rather than have a brittle fracture leaving debris all over the place!

Mark

Just tried typing "spring pin" in and looking at the pictures - there are lots of the type you have and they seem to be distinguished as "spring" pins rather than roll pins or selloc pins. I always think of spring pins as having a parallel slit and a roll pin as being a rolled up strip but everyone seems to have their own ideas on naming them! I think what you have is a "skew proof" spring pin

Edited By Mark C on 29/09/2014 22:53:40

The pin had broken, it was originally 29mm long.

As the shaft it is in has two universal joints there as a further three of these pins in the same shaft. I didn't explain this at the beginning.

Where can I buy these pins, has anyone seen them for sale in the UK?