Is investment casting OK?

Tropical Z · October 17, 2001, 12:46 PM

My new SAM 1911 has a frame that is investment cast of 4140 steel.I have always been a big fan of milling so i'm wary of other procedures.While we're at it how close is forging to investment casting?

gunny6 · October 17, 2001, 04:33 PM

I think that Ruger makes all of their handguns using investment casting, along with many other items..If you can say 1 thing about Ruger`s, they are hell for stout.......

Handy · October 17, 2001, 04:35 PM

I think Ruger has shown that investment casting can be a really wonderful way to make something, as long as that something was designed to be a cast part.

I'm having a hard time imagining a frame that's normally machined from a forging being very strong or wear resistant, but they make aluminum 1911 frames too, so maybe it's okay. (The aluminum framed 1911's do wear out, though.)

Either way, I hope this is a very inexpensive ($250 or less) 1911 that it would be made in this manner.

Dfariswheel · October 18, 2001, 02:35 AM

Lost wax casting is just as good as forging, provided it's done right. For a good example of the right way, take a look at a Kahr Arms frame. Casting got a bad name in the mid 70's when a number of companies (who not surprisingly aren't with us anymore) did some really BAD guns by casting them. They used casting just because it was cheap, and the result looked like it.

I had a early 70's VEGA stainless 45 auto kit. The slide and frame were cast, and nothing fit properly. Both were full of pits and voids, and there were areas that were so poorly cast, it looked like the part had been removed from the mold while still molten.

Ruger was the first to really get it right, and showed everyone else how guns could be made both cheaper and still good.

In some cases, a cast part can be stronger than milled steel, because there are no internal stresses in a casting.

I still prefer forged and milled, but I was astounded by the smooth, burr-free interior of the Kahr K9 I bought. It is the egual of any milled frame.

Jim March · October 18, 2001, 03:27 AM

Yes, it's true, there are some stocks that are so devalued, the best thing you can do with the useless paper is to make fishing lures out of 'em so in that sense, yes, "investment casting" is OK.

Wait...you meant...never mind

WESHOOT2 · October 18, 2001, 06:26 AM

My 1911 frame is an investment cast Caspian frame.

Best quality. Relax, be happy.

stellarpod · October 18, 2001, 07:29 AM

"Investment casting" and "forging" really have nothing to do with "milling". Both casting and forging are a method of turning raw material (alloy steel, iron, aluminum, etc.) into a semi-finished form that approximates the shape of the finished object. Milling is a machining method which removes material from a piece of raw material, casting or forging, usually in the latter stages of manufacture. Virtually all gun frames, regardless of the methods used to fabricate the initial frame blank, utilize milling in one aspect or another. Some people use the term "milled" generically to represent a part who's form is machined enmass from a solid chunk of material.

Forging utilizes metal in a semi-molten state being "pressed" into a resemblance of the finished part using specially formed dies and presses which generate literally tons of pressure. The resulting part is a very strong, very homogenous part, but with a good deal of extra material that must be machined off - much of it by milling. And the forging dies can be prohibitively expensive for a small manufacturing company.

Casting utilizes liquid molten metal poured into a mold - usually formed in sand - to form the part. It is critical that the "brew" have the proper chemical components, that the temperature is maintained properly and that the mold is designed with proper input ports (gates) and vents (risers) to effect a consistent flow throughout the mold. Once the part is shaken out of the sand and cooled, there is a significant amount of grinding and clean-up to do to present a casting who's shape is consistent enough to be machined in mass production fixtures. The patterns necessary to create the molds in the sand are not cheap, but are usually a more economic option than forging dies. The downside is that a sand casting is much more suseptible to foreign material in the casting, voids or gaps in the part, and results in more wasted material.

Investment casting, as opposed to the more common sand-cast methods, yields a semi-finished part which is much closer to the finished dimensions, thereby requiring less clean up and machining. The cosmetic capabilities are incredible as compared to common cast parts. The net result for the manufacturer is hopefully a more cost effective method of producing the part. When done properly an investment casting can be every bit as reliable as a forging.

All of these methods are used to one degree or another in the firearms market. I personally have no problem what so ever with a firearm that is manufactured using an investment casting.

Sorry for the droaning...

Tropical Z · October 18, 2001, 01:43 PM

Great answers!
Now i know a lot more than before.
Supposedly SAM has a state of the art manufacturing facility,so i don't think i'll worry anymore.
Thanx

James K · October 18, 2001, 02:04 PM

There is not necessarily a "right" way for all cases. Two old techniques, machining from rolled bar stock straight from the steel mill and forging with finish machining, are both good, but expensive. Casting, when done right, is far less expensive, but when strength is involved, castings may need to be thicker than forgings. (Most Ruger parts are thicker than comparable forged parts, making Ruger guns more massive than the forged products, but stronger than products cast to the original forged sizes.)

Another method which has come into use recently, is metal injection molding (MIM), in which powdered metal is compressed to shape under enormous pressure.

A good designer will use the manufacturing method which will be appropriate to the use of the part and which will be the most cost effective. Even non-metals (plastic, polymers, etc.) have come into use in firearms in relatively recent times, and have proven highly satisfactory when used appropriately.

Trouble arises when a manufacturer decides to cut cost by using a less expensive manufacturing method in an inappropriate manner. That is when alloy parts peen or crack, MIM parts dissolve, or plastic parts break. These failures usually occur when the accounting department overrides the engineering department or when some small company decides it doesn't need engineers and takes the word of a sub-contractor that his production method will be OK.

Any materials and any manufacturing method can be satisfactory in the right place. But I will skip plastic barrels, thank you.

Jim

Wild Romanian · October 18, 2001, 07:59 PM

I personally have always loathed and hated castings.

1. They make the weapon far heavier than need be. Why? because castings have air holes in them and must be made more massive because of the strength factor.

2. Cosmetically most of them look horrendous. In some Rugers you can even see the air holes. They are the little pitts one sees on the surface of the casting.

3. Low temperature affects the strength of some castings making them more brittle.

4. Some castings are well know for shattering when dropped on a hard surface.

5. When sending a weapon in for repair that has a cast frame make sure the gunsmith is aware that the frame is a casting or he make crack it when he attempts to tighten the slide to frame fit.

Forgings because of their superior strength can and are made thinner resulting in a lighter but ever bit as durabale weapon.

Although it is true that castings have been improved recently the value of your weapon will be less in resale if it has a cast frame. Many people like myself avoid cast frames and slides like the plague.

I do own some cast weapons and I find no pride of ownership or aesthetic appeal in them. W.R.