Dutch Pins: How To?

I need to lock some cast iron 1"-32 threaded plugs into an aluminum block. I was planning on using a "Dutch pin" technique, but have never done so. Is there anything to watch out for on this?

(By Dutch pin I mean a pin that is dropped into a hole which was drilled and reamed across a threaded fastener, thus locking the fastener in place)

The reason I ask is that normally I would just go ahead and drill and ream, however the dissimilar materials make things more complicated. I am wary of using a striaght-flute reamer because the hole is different materials on each side, and I figure any reamer is going to tend to cut the aluminum more than the cast iron (an oval hole is no good). Should I use a drill followed by an endmill, and just pick an oversize pin?

Sorry for the basic question, but I'm no toolmaker, and it's been hard to find references for things like this. If anyone has any references for different jig and pinning techniques, I am all ears. This is a world way beyond the basic mill/lathe stuff I've been doing up to now. I know reading won't make me a toolmaker, but I'd like to at least know about what techniques are out there.

Seems like a lot of work with some risk. What about Loctite or some such thing.

maybe a spring pin? could save you some greif

I am Dutch but never heard of a thing like that
So sorry no help from me

Peter from Holland

It will be interesting to see the responses as I have has zero luck with the combination you propose. One time, when I was desperate trying to fit an AL hub to a steel shaft, I inserted the steel shaft to be drilled into a dummy steel blank to drill the hole. Then inserting the drilled steel shaft into the AL hub I used the half hole to guide the drill into the AL.

Perhaps if a very short drill is used and you don't have to drill to deep a more direct method would suffice.

+1 for the spring pin, as the stud is already located and held by the thread, you only need the locking pin to keep it from turning.
With a spring pin you only have to drill the hole, no reaming needed, and even if the hole end up oval due to dissimilar materials, it will be OK for the spring pin.

But. If the application does not involve extreme heat, Loctite will do a superb job, and will be a lot quicker.

Vladimir

I vote for loctite. or how about a broached keyway? that should keep things square to each other

Have you thought of drilling a smaller hole thru in case a situation arises which makes the pin removal necessary?

Dutch pin location

You don't specify the thickness of the aluminum block but in any case I would make sure the pin hole is located in the center of the meeting point of the CI & aluminum & drill a pilot hole for the use of a no. 4 tapered pin reamer. The reamer will finish up any irregularities in the pilot hole (if any) & will allow you to set the tapered pin in the hole for positive positioning. Of course the hole for the tapered reamer MUST be drilled all the way through

I never knew that was called a "Dutch Pin", thanks.

+1 for using a ball mill on the iron plugs before installation, then drilling the aluminum after installation.

You should be able to find a spiral flute reamer to do the job.

Who cares if it's slightly off-center toward the aluminum? It's only there to keep it from rotating. In fact, you could ball-mill to 70% depth in the iron, and it would drill much nicer.

You don't specify, but I infer you are drilling a hole with an axis parallel to the axis of the cast iron plug. In the Anglo world these are called 'Scotch Keys' and are quite often used to hold the rim (say bronze or alloy steel) onto a wheel centre (say CI or steel, eg for a wormwheel or a gear wheel).

As others have said (those who made the same assumption I am) this is tricky when the material on one side is so much softer than on the other, and you want the central axis of the drill to stay on the interface.

One way I've got around this is to machine the keyway on the shaft (plug, in your case) by lying it down in a vertical mill and using a ball nose cutter (as Racer Al seems to suggest)

However, a safer (albeit more laborious) way to do the other half-hole:

Plug the block with a dummy made from a scrap piece of aluminium turned to a close fit. To get the fit right, you could tap a jacking hole and another hole to be able to turn the plug, drill slightly undersize and use an expanding reamer. Because the materials are the same, the straight flutes (should!) not jam.

This will require removing the dummy every time you want to try how the fit is shaping up with the plug, so it's a bit tedious.

Halcohead wrote, "...drilled and reamed across a threaded fastener ..." I take this to mean that the axis of the locking pin is perpendicular to the axis of the plug.

Weirsdale George said:

Halcohead wrote, "...drilled and reamed across a threaded fastener ..." I take this to mean that the axis of the locking pin is perpendicular to the axis of the plug.

Click to expand...

Yes, I agree that if he had been writing in UK or New England English that would seem to be a safe bet, and any of my English teachers would have taken your side.

I think however he may mean 'across' in the sense that the drill is crossing two different materials as it sweeps.
I have noticed that in parts of the US directions are conveyed differently from what I am used to.
eg certain Americans talk of which way a road sign is 'pointing' when to me what they're talking about is which way it is 'facing' (given that the sign may also have an arrow on it pointing left or right, or even up.)

I based my inference on the fact that he also wrote:

<<I am wary of using a striaght-flute reamer because the hole is different materials on each side, and I figure any reamer is going to tend to cut the aluminum more than the cast iron (an oval hole is no good)>>

This, combined with the obvious Dutch / Scotch crossover seems to me to tell a different story.

(actually I'm not being entirely facetious on this naming thing: if he meant what you think he meant, it's hardly a novel technique requiring a special name)

It also strikes me that unless there's a boss in the block projecting well past the general profile (or alternatively it's right at the top or bottom of the face), it would simply not be possible to cross-drill as you infer.

However you may well be right, it's hard to come by an unambiguous OP in these troubled times.


[note to Peterve: I wouldn't read too much into the "Dutch" - Pennsylvania Dutch, to take one example, are in fact of German extraction (Deutsch)

We're no better down here: I've lost count of how often I've been in engineering works where it turns out that 'Dutch Pete' is actually Polish, Latvian or whatever. Kind of a 'default foreign person who talks funny' label. (Cringe)]

Troup -- I see your point. I missed the "... the hole is different materials on each side ..." reference. All the more reason to use Loctite!

Thanks for the ideas and methods guys. It's been very helpful.

I recognize that my original post was slightly vague. It is my understanding (as taught by an old toolmaker) that a dutch pin is a locking pin pressed into a hole whose axis is parallel to the axis of the threads which are to be locked, with 1/2 of the hole in the threaded part, and the other half in the tapped part. I hope that clears any confusion.

The parts do need to be held together across a relatively wide temperature range (<0º C up to >120º C), so locktite is not ideal. Of course, with such a large temperature range, it is also possible that the aluminum will expand enough more than the CI to loosen up any pressed pins or threads.

I will use the ball-endmill technique, followed by StanP's suggestions for a tapered pin. it seems like the best way to get at least a reasonably round hole, followed by a good press fit.

Don't take my word that it's called a dutch pin. That was the name given to me by a toolmaker whose been in the business for 35 years, but then again he's got his share of naming quirks. Troup, call me dense, but you seem to imply that the actual name is a Scotch pin? I'm skeptical :P.

Is it a Dutchman?

A Dutchman is a woodworking patch.

Dutchman is also a conveyor belt patch, also known as a saddle.

Dutchman can mean a number of different things. Not a term I use myself,but have heard it used.

A Dutchman is a person from Denmark