Porosity in castings

[Craig Wilcox]

How is everyone handling porosity in such as lock casting?  Most of the many castings that we use to build longrifles are really great, but from time to time we find a casting in which the surface has many small "craters", generally caused by difficulties in the casting process.

I've been polishing up several different locks recently, and the lock plate (and cock) has many large bubbles in the surface.  In the past, with few indications of porosity, I have taken the filing a few thousandths deeper, resulting in a fairly well polished surface.  This one, however, I think I'd have to go down about a tenth of an inch, and I am not comfortable with that - everything gets to be a bit "off".  I will be trying to get, or to buy, if I have to, a new plate, because besides the large pores, the cast-in primer pan has a 3/4" crack through it.

I could probably talk a friend into TIG welding over the area, and the crack, but I am genuinely interested in how others handle the problem.

Thanks in advance for responses.

Craig

[Clark Badgett]

A tenth of an inch (.100") would almost be a hole completely through a lock plate. Do you men a hundreth (.010") of an inch? A good tig welder could easily fill it.

[canadianml1]

One option is to buy a lock that is not cast such as the Kibler which are made from bar stock fully cnc machined. Bar stock is much cleaner than even the best investment castings. My experience trying to get rid of surface defects is that more filling/sanding can uncover formerly concealed defects.........frustrating!

[alacran]

One option is to buy a lock that is not cast such as the Kibler which are made from bar stock fully cnc machined. Bar stock is much cleaner than even the best investment castings. My experience trying to get rid of surface defects is that more filling/sanding can uncover formerly concealed defects.........frustrating!

Really? The reason the locks parts or any parts for that matter that have flaws, lies with the foundries. The care of molds , the care of the overall process. Ruger casts most of their parts and then machines them, some parts are used as cast with minor polishing. They control the whole process. The custom muzzleloading industry is to small to produce quality castings.

[smart dog]

Hi Craig,
The holes can be welded over and the crack in the pan fixed the same way but they are indications of poor casting and there may be hidden problems.  For example, I used a Davis colonial American lock on a rifle.  It looked fine externally but when I drilled for the rear lock bolt, that part of the bolster crumbled into pieces because it was riddled with voids. The flintcock on that lock, which is massive, broke at the neck after 2 shots. There was a void and black crusty metal at the break.  The Brown Bess lock I recently built from TRS parts had a large void right in the lock plate bolster where the frizzen screw was to be threaded.  I filled it with weld and hoped there were no other problems.  In your case, a new lock plate might be best but you can fix those holes by welding. I can forgive a lock company for hidden casting problems but when those problems show on the surface, to continue to use that part for the lock and then sell it is wrong.

dave   

[Bob Roller]

One option is to buy a lock that is not cast such as the Kibler which are made from bar stock fully cnc machined. Bar stock is much cleaner than even the best investment castings. My experience trying to get rid of surface defects is that more filling/sanding can uncover formerly concealed defects.........frustrating!

Really? The reason the locks parts or any parts for that matter that have flaws, lies with the foundries. The care of molds , the care of the overall process. Ruger casts most of their parts and then machines them, some parts are used as cast with minor polishing. They control the whole process. The custom muzzleloading industry is to small to produce quality castings.

This sums it up.I remember L.C.Rice telling me that a foundry owner or foreman told him
that they did production and not quality control.That really inspires confidence doesn't it?
I remember lock plates so hard that they shattered like glass when I tried to straighten them
and frizzens that no drill would bore a hole thru.Anyone that sends out an obviously flawed
cast part is only out for the money and customer satisfaction is not a consideration.
Jim Kibler using CNC machinery is doing the right thing and anyone who still has one good eye
can see he is quality oriented and doesn't want his name tied to profane utterances about what
he is offering.May his tribe increase.He manufactures steel shavings and the lock parts are a by
product that are beneficial to all who use them,

Bob Roller

[Craig Wilcox]

Thanks guys.

Clark, yes, 0.10 depth in the bubble.  Looks like a moon crater, and was a little pin-point when I started polishing.

Canadian, since I already have the lock, that is a moot point.  I really do like the CNC-produced locks, polishing them is fast and simple.  But currently, those are only available in a few styles.

Alacran, I totally agree - our market is measured by the dozen, instead of the thousands.

Dave (Smart Dog), I agree - who knows what lies below the surface.  I shall pursue getting a replacement plate,  I have no idea what steel might have been used in the original casting, and if I cannot get the lockplate replaced, will see if my friend can weld it up with a common filler.

Bob Roller, as usual, you hit the nail on the head!  Currently, tho others are in the process, only Jim Kibler and Firelocks LLC produce CNC locks.  The price difference is certainly worth it, too.

[Mike Brooks]

I love pox. Goes great with my antique finish.

[yulzari]

There is the fact that actual period brass castings were also prone to the same defects.They were simply poured into sand moulds formed around wooden patterns and often used mixed scrap.

[Bob Roller]

There is the fact that actual period brass castings were also prone to the same defects.They were simply poured into sand moulds formed around wooden patterns and often used mixed scrap.

The fact that antiques are flawed shouldn't make them acceptable today and if it's
tolerated it will be continued forever. Locks being sent with defects that a visually
impaired person can see should never be accepted and poor assembly only compounds
the problem.Better is now being offered and should be embraced.
Bob Roller

[jerrywh]

 I have done many such repairs in my lock engraving.  At first I use to tig weld them and it took me a little time to learn how to do it with very little refinishing.  Now I repair them with iron inlays and there is no way they can be seen. The only thing that will expose a iron inlay is heat bluing. almost  any fix will show on a heat blued finish.  Below are some flaws I repaired with inlays. Then the finished lock as engraved latter.  This lock plate had many other defects that were repaired in the same manner.

[davec2]

Castings are often plagued with porosity.  Welding will often help but sometimes, if the flaw is an inclusion rather than a void, whatever is in the inclusion will outgas during welding and make an even bigger mess.  Companies like Ruger, while they use a lot of castings, also send all of their castings through a process called HIP (Hot Isostatic Pressing)

https://en.wikipedia.org/wiki/Hot_isostatic_pressing

This process eliminates all voids and gives castings near wrought material properties.  Basically as good as machining the part from bar stock.  This process can be used on any alloy from aluminum castings to high strength nickel "super" alloys.  If it was cost effective, you could easily improve the quality of all our cast gun parts by HIPing.

If a cast part has too many flaws, or flaws that are too large, it is far easier / cheaper / better in the long run to replace it (either by getting the manufacturer to replace it or by buying a new part) than to spend time and energy trying to fix it. (Unless your more interested in fixing casting problems than in building the gun... )

JerryWH taught me how to do the iron inlay method and I have used that many times to repair small defects.  The same technique also works on brass parts.

By the way, I have seen some wild "Damascus" steel billets produced by HIPing.  All manner of steel and iron components, like ball bearings, iron powder, fence wire, concrete nails, etc) are used to fill a piece of pipe with welded on ends.  The pipe then goes through the HIP furnace and the whole mass is welded into a solid billet that is then forged into a knife, axe, whatever.

[Craig Wilcox]

Dave, one can only wish for HIP to come to our world!  I can picture a lock plate being pressed between two large rollers.  Especially one with a cast-in primer pan!

I doubt that our low-volume needs will get treatment such as this.  And while I have tried brass-inlays, I would be very reluctant to try doing an inlay of steel on a cast steel plate.  Along with my spinal problems, or because of them, I find that my manual dexterity is gradually disappearing.  Very hard for me to make the bottom of the excavated area smooth and continuous, much less cut the new steel exactly to fill the empty space.  I would undoubtedly make the problem visually much worse.  I do keep steel sheet stock in hand, but mostly 1095 for spring work.

Still, I will probably give it a try, if I can get a replacement lock plate "just in case".  We shall see what the original vendor has to say as for a replacement.  I shall also ask my (Amish) welder friend about his ability in correcting the defects.  I predict a LOT of file work if he tries.

Really appreciate all the hints, tips, and recommendations.  Best bunch of guys and ladies ever!!

[Craig Wilcox]

My Amish friend fixed the big pit in the casting.  He used a 1/8" drill bit to make a little divot and expose fresh, clean metal, then took about half a second to put a drop of welding rod in the divot.  Bit of filing, sanding, and polishing, and there is no indication there was ever a problem.

I asked him about the crack on the outside bottom of the pan.  He looked at it a good while, then said not to worry, as it didn't penetrate the pan.

So, the plate is now polished and blued, and looks pretty fair.

I used Brownell's Oxpho Blue on it - 3 coats with a steel wool polish after each coating.  I did all the external parts that way.

Thanks to each of you for your input.

[jerrywh]

I'm just curious to know how do you put in a drop of welding rod.  somebody please explain

[Craig Wilcox]

I was watching him, Jerry.  He barely touched the lock plate with his mild steel rod when he flashed the TIG.  Really did look like a small tear drop.
I think drilling with that 1/8" bit helped a lot - he made the divot a bit deeper than the pore in the metal, got rid of the as-cast portion.  About half the thickness of the plate.
It surprised me when I looked at it after - just a slight bulge above the plate, which I filed then sanded - looked like the hole was never there.
He usually welds on combines, corn picking machines, and tractors, so it was amazing to see how delicate he was on the lock plate.
Been moving, so things are a bit discombobulated - will take a pic when I can.