Forging bronze drifts and bolts

[Figment]

The long flathead bolts that fasten my stemstrap are due for replacement. I thought I had a source, but it didn't work out, so I'm beginning to think that I may just wind up making new ones from scratch. They're nothing really heroic... 3/8" x 9" or so.

Can anyone point me toward a good source of info on the process of forming a head onto the end of a bronze rod? The "Drifts" part of the FAQ points to a missing thread.

[pcford]

Unless I am not understanding something:
Thread both ends. Put a washer and nut on one end. Peen that end. Insert and put washer and nut on other end.

[Jay Greer]

I made the clinch ring production boards for Larry Pardy which he used for both of his boats. Ask Pete Langley at the Port Townsend foundry if he still has a board for casting bronze clinch rings. This is the best way to go.
The rod can be heated to just under the melting point, clamped in a vise and peen headed so as to mushroom enough to prevent it from sliding through the clinch ring. Over peening will cause the head to work harden and crack to be careful.
Taper forging the entry end will make the drift drive easier.
Be sure to drill the holes for the drifts slightly undersize. A bit of tallow on the rod tip will ease the driving. Friction will take over at the end. The rods can be also burred along the length, in oposition to withdrawl direction, by using a chisle or sculpters adze.

[Jay Greer]

I just noted that this is a replacement job so clinch rings on the end that will be buried and plugged with nuts and washers on the exposed side are the traditional way to go.

[ishmael]

What Jay said. I've also used steel dies for various sized rod which after the head was made the stock was driven into to make ridges, sort of fake Herreshoff heads, if it was to butt up to wood. A cross ridge in the bottom of the head. Not the thing for fasteming a strap, but FWIW.

I'm trying to remember how the dies were made. It was fairly simple grinding IIRC. Bronze is pretty soft when hot.

[Jay Greer]

What you are speaking of is the Herreshoff "Fin Headed Bolt". A two piece die can be made by drilling on the parting line, then doing a counter sink, taking the halves apart and grinding in the wing sections with a die grinder. A couple of bolts or locating pins will allow one to clamp the die into a vise with the rod running through the hole. Heat the rod, and pound it down into the counter bar. Should end up with a nice fin head.

[formerlyknownasprince]

Here is how we did it - a two piece die. We used a press. Prior to this tool we used a hammer and a flaring tool in a vice.

http://www.imagestation.com/picture/sraid101/p6a4a969b0ba8eaba9a9529ca6aab44d7/f9d62018.jpg

These are 1/2" bolts.

Ian

[PeterSibley]

I've made up fin heads in copper ,not bronze so far.Good result.

Jay, just for the interest.....when making up a multiple pattern board do you turn inividual patterns or make up a master and cast the lot in something ? Up to now I've made up individual patterns but recently thought of making up a mold and casting everything in polyester or equivalent.

[Jay Greer]

I used individual galvanised clinch rings for patterns. I polished them smooth and then glued them on the board with tapered sprues made of honduras mahogony. The pattern looked like a money tree branch attached to the main sprue. The whole works was carefully filleted with bees wax and coated with shellac.
We could get about thirty rings per run.

[PeterSibley]

Jay...I assume the rings are in gunmetal? I don't have much experience with gunmetal,most of my stuff is in manganese bronze.What size do you make your feeders,main and laterals for something the size of a clench ring.Does it shrink much?Manganese bronze is particularly horrible!

[Figment]

Perhaps I've phrased the problem incorrectly.
Here's the application:
http://cerjanickuss.com/bearsjunk/Stemstrap.jpg
The stemstrap is cast for four countersunk flathead fasteners. The bottom three are long bolts, the top one is a bigass woodscrew
http://cerjanickuss.com/bearsjunk/Bolt1.jpg
This is one of the bolts. 3/8" shank, 8" length, head diameter 3/4". The shank diameter is corroded down below 5/16" in a few spots
http://cerjanickuss.com/bearsjunk/boltshank.jpg

So, what I think I need to do is to start with some rod, peen a tapered head onto the end, file it flat, cut a slot, etc.

I have a die (from a tubing flare kit) for forming the tapered part of the head.

How hot does the bronze need to be? just Fing hot, or nearly molten? How concerned do I need to be about work-hardening, etc?

I'm sure there are a dozen questions that I don't even know enough to ask, so thanks for chipping in, fellas.

[ 11-04-2005, 11:13 AM: Message edited by: Figment ]

[PeterSibley]

Figment,I have some experience of one type of bronze,unfortunately its not the one you're using.You can either experiment or possibly a better idea,ask your metal supplier for info on forging,
cheers,
Peter

[Paul Pless]

bigass woodscrew

That description should be standardized and used in more catalogs :D

[Figment]

Well, "Fatass woodscrew" would be more appropriate.

3/8" shank and 3/4" head, but only about 3" long.

[AHall]

Ian: i am very interested in the construction/use of your drift heading die.

would you mind elaborating?

do the two horizontal rods and plate control the lenght of the drifts, or do they prevent buckling of the bronze when in the press?

Would it be worth making one for making say 20 1/2" dia drifts?

I have acess to a lathe and milling machine, but would not call myself a machinist.

Thanks in advance,
Andy Hall

[Mrleft8]

Did you try the Nutty company? If they don't have it, they can usually get it in less than a week.

[Jay Greer]

We chose Navy Bronze for our clinch rings. That choice being because it is not as prone as manganese bronze is towards fracture when struck when driving drifts. We also did a slight ream and counter sink on the rings to make the job cleaner. Shrink is of not that much concern for this type of casting. Certainly for more critical pattern work metal shrink is taken into consideration. A shrink scale is a handy tool to have in that case.

[PeterSibley]

The problem with shrinkage Jay is not just the obvious one of you casting being smaller by the shrinkage amount,but with a metal like manganese bronze ,with a very high shrinkage,as it solidifies in the mold the smaller sections solidify first and draw material away from larger sections.The results can be confusing til you realise whats going on.The reason for my question is that with manganese bronze small feeds can actually suck metal back out of the casting.Not good.

[Jay Greer]

Well, I grant you that can be a problem. It didin't happen to us cuz we opted for a differnt alloy.
In addition, the clinch rings and small branch sprues were on the cope. The main sprue was quite big and in the drag. This allowed the weight of the pour to prevent the rings from being sucked back by any shrinkage as they cooled first.

[ 11-05-2005, 08:41 PM: Message edited by: Jay Greer ]