how to slightly open small (.093" Diameter) hole

BobM3 · Mar 19, 2020

An assembly of ours consists of a worm mounted to a shaft. The two are held together by a roll (shear) pin. The hole diameter is .093" and the worm hub diameter is .50". Our best hammering guy retired a short time ago and the rest of the crew has trouble getting the pin inserted and pounded in. I was looking to find a way for the assemblers to open up the hole a bit (a couple of thousands would help). We use flexible hones on other items and they work well but it doesn't appear they are available for a .093" hole. The worm is hardened to 50 Rc which limits what would work and hold up. Any ideas?

Limy Sami · Mar 19, 2020

Any help? Acro lap, Needle Eye Laps, Midget Lap

Terry Keeley · Mar 19, 2020

Drill #88?

L Vanice · Mar 19, 2020

You could chuck the roll pin in a battery drill and rotate the pin end against a grinder to put a longer bevel on the pin. Standard 3/32 roll pins are designed to fit a 3/32 hole, so there should be no need to enlarge the hole. But it would be easy to modify the pin to make it easier to start in the hole.

Think about pressing the pin in the hole rather than hammering on it. One simple tool for pressing a small pin is a Knipex Plier Wrench, a big pliers with jaws that close parallel to each other. They come in several sizes and are available with smooth jaws.

https://www.knipex.com/index.php?id=1216&L=1&page=group_detail&parentID=1368&groupID=1500

Another trick I have used is to squeeze the pin in pliers and push the end of the pin into the hole while using the pliers to both squeeze and push. The Knipex tool is good for that job, and then can be used to press the pin all the way into the hole.

You should know that Mac and others make special pin punches for driving roll pins out of holes. Very handy for that job.

Larry

thermite · Mar 19, 2020

BobM3 said:
An assembly of ours consists of a worm mounted to a shaft. The two are held together by a roll (shear) pin. The hole diameter is .093" and the worm hub diameter is .50". Our best hammering guy retired a short time ago and the rest of the crew has trouble getting the pin inserted and pounded in. I was looking to find a way for the assemblers to open up the hole a bit (a couple of thousands would help). We use flexible hones on other items and they work well but it doesn't appear they are available for a .093" hole. The worm is hardened to 50 Rc which limits what would work and hold up. Any ideas?

Hole worked for the craftsman, hoel is not at fault.

Fix the problem cheaply. Not the bystander "the hard way". Always.

Rolled spring-steel pin is for assembly, BTW. They make dead-lousy "shear" pins if only 'coz they are MESSY and unpredictably raggedy-assed if/as/when stressed to failure.

We've covered this already.."Right here, on PM". Where else?

Anyone Know How to Build a Roll Pin Installation Machine?

Here's another:

Excelta Roll Pin Insertion Plier

Can't find one, just MAKE one.

Made one ages ago back in the "why doesn't someone make.." days. "Eifel geared plierench" the horse it rode on:

Eifel Geared Plierench — Rust Magazine

EG: Lot of us did DIY as "deja vu all over again" in the years before google and the internet showed us someone DID already make ... most anything useful.

Illinoyance · Mar 20, 2020

A lap is not going to remove much metal. A slightly larger drill is likely to screw itself into the hole. Put a slight chamfer on the hole to aid starting. Hold the pin in pliers.
A groove across thew jaws helps hold the pin. Compress the pin slightly with the pliers. Tap gently into the hole. It takes a little finesse so not everyone can do it.

L Vanice · Mar 20, 2020

thermite said:
...Made one ages ago back in the "why doesn't someone make.." days. "Eifel geared plierench" the horse it rode on:

Eifel Geared Plierench — Rust Magazine

EG: Lot of us did DIY as "deja vu all over again" in the years before google and the internet showed us someone DID already make ... most anything useful.

I got my first Eifel Plierench around 1954 and have treasured it ever since. I have around fifty of them now, from the first (Model 8-A-21 of 1921) to the last models, along with the printed literature. I have the Vaco version made after the original business was sold. There was a company (Galland Henning Nopak, Inc.) that bought the name and rights in 1996 and was still making them as recently as the late 1990's or so. The various original Eifel versions are very easy to find on eBay because they were a very useful, well-made and unique tool and probably a million were sold over about eighty years of production.

Larry

CarbideBob · Mar 20, 2020

thermite said:
Rolled spring-steel pin is for assembly, BTW.

Rolled spring pins suck for attaching a pin held gear to a shaft.
The have no torsional resistance which is why they are easy to install.
If done be careful where you orient the seam or know your loading.
Done in places and works, others the pin walks it way out with time and then you wonder why my assembly failed after months, years or decades of working.
Bob

thermite · Mar 20, 2020

CarbideBob said:
Rolled spring pins suck for attaching a pin held gear to a shaft.
The have no torsional resistance which is why they are easy to install.
If done be careful where you orient the seam or know your loading.
Done in places and works, others the pin walks it way out with time and then you wonder why my assembly failed after months, years or decades of working.
Bob

Get you a "shop cat", then. Half a drop of cat urine, the roll-pin will corrode solid in-place.

Or so it seems to have been done to those I need to EXTRACT!

EPAIII · Mar 21, 2020

Perhaps what you need is a (or several) guide block to assist the low skill level people. Make it about 1/2 to 2/3 the length of the pins and with a hole a thousandth or two larger in diameter than an uncompressed one for an easy fit. Then they can use the guide to start the pin straight and remove it when it gets down to the surface of the guide block.

BobM3 said:
An assembly of ours consists of a worm mounted to a shaft. The two are held together by a roll (shear) pin. The hole diameter is .093" and the worm hub diameter is .50". Our best hammering guy retired a short time ago and the rest of the crew has trouble getting the pin inserted and pounded in. I was looking to find a way for the assemblers to open up the hole a bit (a couple of thousands would help). We use flexible hones on other items and they work well but it doesn't appear they are available for a .093" hole. The worm is hardened to 50 Rc which limits what would work and hold up. Any ideas?

deltap · Mar 21, 2020

May be a problem with aligning the holes while pounding. A pin from the back side will keep the holes lined up.

dian · Mar 21, 2020

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matt_isserstedt · Mar 21, 2020

Don't know sizes but if abrasive cord came in a size small enough to go thru, a little back and forth action could help out.

The downside of course is the abrasive dust left behind that would have to be cleaned up.

Can the holes be made slightly larger on the next generation of parts? You could potentially remachine existing parts but have to set them back in in a machine...

Roll pin can also benefit from a generous chamfer.

rifle guy · Mar 21, 2020

These are the best thing I've found for smaller pins. If they cant get them started right with one of these you have other problems.

BROWNELLS PREMIUM ROLL PIN HOLDERS | Brownells

BobM3 · Mar 30, 2020

Great ideas everyone! I had thought about modifying a pliers but I see from the above they are readily available. I tried chamfering a pin - that did help get the pin started in straight. I did come up with a jig years ago that I use but no one else likes to use. I'm going to work on a better jig that lines the holes up as best I can.

I'm able to easily slip a .093 drill through the holes so hole size and position are fine. This product has been around for 50+ years and there's never been a failure of the pinned assembly so I think there's a lot of tolerance for the different techniques used through the years. I will try to make a small jig to press in the pin instead of hammering.

I'm going to inquire about adding a slight countersink to the worm hub hole next time the worm blanks are made.

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