Hammering out cast brass

[BarryE]

I have a triggerguard that is the perfect profile for a project.  It is, however, way too narrow at the front finial.  There is a bit of excess there that, if hammered out, would possibly be adequate for the job.  My question is can this be done without cracking a casting and how to best do that work? Is simple annealing adequate or would something else work better?  Thanks!

[Elnathan]

It will probably depend a lot on the casting...a lot of investment cast parts are notoriously hard to even bend without breaking them. Reaves Goering castings would hammer out, and maybe a Chambers or one of Mike Brook's new castings based on what others have said about them. Dunno about the sand castings that Track and others sell.

[Goo]

Anneal it first, then go slow and easy with the hammer.   Anneal in between courses of hammer strikes.

[Hungry Horse]

Is it yellow brass, or a bronze alloy? If its brass you can work it slowly, and carefully, as mentioned, but if its bronze, the likelihood of it surviving the attempted drawing out are pretty slim.

  Hungry Horse

[smart dog]

Hi Barry,
If it is wax cast, you will be very limited in expanding it even after annealing.  If sand cast, you will have much better luck.  I do this kind of thing very often and much prefer to work with sand cast parts for that purpose.

dave

[Goo]

Hi Barry,
If it is wax cast, you will be very limited in expanding it even after annealing.  If sand cast, you will have much better luck.  I do this kind of thing very often and much prefer to work with sand cast parts for that purpose.

dave

Why would sand vs investment cast have an effect on on forging or compressing / stretching / hammer forming the brass?      There is usually more porosity iin sand cast parts.  Sand castings are generally more porus due to gassing off when the molten metal reacts with the mold media as it enters the cavity.     Investment castings can have porosity but it takes a higher temperature Spike to cause the reaction.   Respectfully just want to know what lead you to this determination.

[smart dog]

Hi,
A lot of experience led me to that conclusion in addition that wax cast parts appear to usually be a different alloy than sand cast parts and they have much less excess metal with which to work.

dave

[bob in the woods]

Ref " The Gunsmith of Williamsburg"  Wallace Gusler casts brass sheet to be used for thimble and patchbox construction.
After casting, he hammers it out using a flatter .  I think you'll be fine if you anneal often

[G_T]

I've done a fair bit of hammering ingots out from jewelry metals and brass has some similarities.

Begin the process by annealing the brass. You want it dead soft. People can tell you temperatures and time to hold before letting air cool, but it is best to get a feel for it. Get some strips of brass such as that K&S stuff that you can find in hobby shops and some hardware stores. Heat one to what you see as a dull red preferrably in a reducing atmosphere and then let air cool. Heat another one just a little brighter red. Etc. When cooled, bend each in your hand. That will give you an idea of how soft you might want it.

To see the color of the metal best when heating, dim the lights.

You want the area you are going to be hammering to be dead soft. Ideally you'd like the rest of the trigger guard to stay pretty hard! So just apply the heat to the region you want to soften.

When hammering, I'd recommend using a hammer that weighs less than a pound, and at least 100 grams. You probably should use a cross-peen hammer. Make sure the bladed side is smooth without sharp edges. Actually, make sure both sides are smooth that way.

Use the cross-peen side to stretch the metal. The metal will want to extend in the direction perpendicular to the line of the hammer. So walk a series of light hits in the direction you want to go. Do not hit it hard! Have patience. Light taps will get it done. Whacks will get it destroyed.

Use the flatter side to dress up the surface so you have less filing to do.

If the metal gets hard enough that it is getting bouncy, before you get the metal moved far enough, then you'll have to anneal again. Otherwise you risk cracking the metal.

It is best to work one side of the metal a little bit, flip it, and work the other.

Of course ideally you'd like the brass to end up at least somewhat work hardened by the time you are done. So if you need to move the metal a lot, you might consider timing your annealing so you still have a little hammering to do after the last anneal.

Gerald

[jerrywh]

I have cast a lot of brass both precision investment cast and sand cast. The method of casting doesn't make any difference on the hardness or brittleness of the casting. It is the alloy that makes the difference.  Somewhere on your casting there is a sprue or there was.
You can take a small piece off of that sprue and test it by hammering it to see how brittle it is. If that small piece hammers out well then you are OK. Soft yellow brass will bend very easily. Silicone Bronze will not bend at all and is somewhat silvery in color. Sand castings can be as bad as any other.

[JCKelly]

Good information.

One thing not mentioned is LEAD

California doesn't like lead in drinking water so a decade ir two ago they banned lead in cast brass faucets. Lead may also be added to bar to improve machinability, or to sheet to help engraving. Maybe 1% lead is added to cast alloys to help make a sounder casting.

Ho-hum who cares.

You might, if you try heating up your brass to better hammer it. Lead melts 621F, and any melted lead in your casting gives that casting all the ductility of molten lead. That is, the casting will crumble when hit. Likewise if you anneal your casting, it is a good idea to cool it by water quench. Helps keep that lead where it belongs.

I know nothing about silicon bronze. I have had industrial experience to suggest that whatever alloy that foundry normally pours is what wll be in your casting if even only a small amount.

[BarryE]

Thanks to all.  I will give it a try using your advice.

[Mike Brooks]

We eat lead for breakfast in Iowa. 

[rich pierce]

We usta mine lead in Missouri.

On topic, yes you can work most brass quite a bit. If you want best control get a helper and use the cross peen hammer like a chisel.  Place the peen end carefully then strike the mammmer face.  One holds em and the other one hits em.

[Dan Fruth]

You can also tell what kind of material you have by filling it. A lot of investment castings are actually a silica bronze, and the file tends to "skate" rather than dig in. Yellow brass will file easily......Just my 2 cents.

[jerrywh]

We eat lead for breakfast in Iowa. 

So now we know what's wrong with Mike.