Best way to repair sintered metal parts?

[Gunner Asch]

Fella brought over a gun part for a Marlin lever action..he was
missing a pin..so I made one up for him and installed it..and as I was
inspecting it..I noticed a rather serious crack starting to develop at
one end of the sintered metal part. I fixed it by using my tig torch
and silver bearing flux..I packed the crack full of the heavy green
flux and zapped it with the tig..sealed it up well enough and I put a
slight layer over the area of the crack. After polishing it up with a
fine wire wheel, it looked good. But...is it?

How well does this sort of thing work with sintered metal parts?

Should I warn the guy to buy a new Widget? (Marlin just closed their
doors...so parts may become hard to find)

Any suggestions for other similar fixs with sintered metal parts?

Gunner


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[Stanley Schaefer]

On Apr 24, 12:07=A0pm, Gunner Asch <gunnera...@gmail.com> wrote:
# Fella brought over a gun part for a Marlin lever action..he was
# missing a pin..so I made one up for him and installed it..and as I was
# inspecting it..I noticed a rather serious crack starting to develop at
# one end of the sintered metal part. =A0 I fixed it by using my tig torch
# and silver bearing flux..I packed the crack full of the heavy green
# flux and zapped it with the tig..sealed it up well enough and I put a
# slight layer over the area of the crack. After polishing it up with a
# fine wire wheel, it looked good. But...is it?
#
# How well does this sort of thing work with sintered metal parts?
#
# Should I warn the guy to buy a new Widget? (Marlin just closed their
# doors...so parts may become hard to find)
#
# Any suggestions for other similar fixs with sintered metal parts?
#
# Gunner
#
I don't think Marlin ever used sintered parts. The carrier in the
centerfires was changed to a precision-cast part from a machined one
in the '80s, if it's older than that, it'll be forged steel and a much
different design. And Marlin lives on, sorta, as Remlin up in New
York state, Kentucky and Missouri. Parts CAN be had, but certain ones
are now factory-install-only. Carrier, bolt, locking block and, I
think, lever all fall in that category. What parts there are in bulk,
Numrich/Gun Parts will have, carriers have been sold out, though.
Brownell's and Midway also carry parts for current guns. If you had
to braze the carrier, it's a low-stress part but almost file-hard,
I've never seen one cracked or broken(what DID he do to it???). There
just aren't that many parts in a Marlin centerfire lever gun. A
somewhat common failure mode is that the spring-loaded carrier pin
loses the riveted washer on the right side, and the lever no longer
drives it up and down to load new rounds. Those parts aren't sold
separately, only as part of a carrier assembly. If the three parts
are saved before they fall out and get lost, they can be re-riveted.
I've had to do this once on my 1894CL made in the mid-'80s. I've had
no problems with my others, including cracks in carriers.

Stan

[Gunner Asch]

This is definately a sintered part..and there are Zero washers on it.
In the parts listings..its 8,9.10

This is the new style I believe

http://www.brownells.com/rifle-parts/bolt-parts/bolt-carrier-parts/bolt-carriers/carrier-assembly-new-style-prod8699.aspx

This is what is actually in that arm.

http://www.schiessen-erzgebirge.de/Blueprints/marlin_1894.gif

Evidently it a much older model.

I repair machinery in machine shops for a living..and have seen a crap
load of sintered (pressed powdered metal) parts in the past 16 yrs.

Gunner

[Rubaiyat of Omar Bradley]

On Saturday, April 27, 2013 4:08:02 AM UTC-6, Gunner Asch wrote:
# have seen a crap
# load of sintered (pressed powdered metal) parts in the past 16 yrs.

How can someone tell the difference between a sintered part and a MIM part?

[Gunner Asch]

On Sun, 28 Apr 2013 19:48:47 +0000 (UTC), Rubaiyat of Omar Bradley
<cowar...@yahoo.com> wrote:

#On Saturday, April 27, 2013 4:08:02 AM UTC-6, Gunner Asch wrote:
## have seen a crap
## load of sintered (pressed powdered metal) parts in the past 16 yrs.
#
#How can someone tell the difference between a sintered part and a MIM part?


http://todaysmachiningworld.com/how-it-works-%E2%80%93-metal-injection-molding/

http://www.flomet.com/mim.html

Largely...one can tell some differences...in how the surface of the
part looks...if its a very matt finish..then put the part in the vise
and hit it with a big hammer. Then examine the part under
magnification. If its small grains of sand in appearence..its probably
PM. If its tiny tiny grains..its probably MIM

Laugh

Gunner

[Stanley Schaefer]

On Apr 27, 4:08=A0am, Gunner Asch <gunnera...@gmail.com> wrote:
# This is definately a sintered part..and there are Zero washers on it.
# In the parts listings..its 8,9.10
#
# This is the new style I believe
#
# http://www.brownells.com/rifle-parts/bolt-parts/bolt-carrier-parts/bo...
#
# This is what is actually in that arm.
#
# http://www.schiessen-erzgebirge.de/Blueprints/marlin_1894.gif
#
# Evidently it a much older model.
#
# I repair machinery in machine shops for a living..and have seen a crap
# load of sintered (pressed powdered metal) parts in the past 16 yrs.
#
# Gunner
#
Actually there IS a washer, it can be seen in the top picture on the
Brownell's site URL that you furnished. The end of the pin is riveted
over on it to hold the pin and spring captive. Like I said, this
fastening can fail, leading to loss of all three parts. If the one
you fixed didn't have the washer around the pin or all the those parts
were gone, that's what happened. I had to use a magnet to recover all
the parts out of the grass when that happened to my .32-20.

The German site shows the later carrier, just is missing the riveted
retainer washer for the carrier pin for some reason. Machts nichts,
they never sold those parts separately.

Guys have used E-clips to replace the washer if lost, some with better
results than others. I prefer to re-rivet.

Here's a better picture of the pin+retainer:
http://www.brownells.com/rifle-parts/bolt-parts/bolt-carrier-parts/bolt-car=
riers/carrier-assembly-new-style-prod8698.aspx

Brophy's tome on Marlins just says the later carrier is a precision
casting, no details on what method was used. I figured that given the
era and the surface finish that it was an investment casting. It was
the latter part of the '80s when they made the change, I figured that
sintered and MIM gun parts really hadn't caught hold yet. I've filed
on these, there was no apparent porosity, so a very good job, if
sintered. In any case, I still haven't seen a carrier that was
cracked. It's such a low-stress part, like I said before. Only load
on it is what's needed to pivot it up with a loaded round aboard.

Stan

[Gunner Asch]

This was NOT the same carrier. It was evidently a much older model.

As you will notice in the link I provided

http://www.schiessen-erzgebirge.de/Blueprints/marlin_1894.gif

The carrier rocker (part 9) is exposed through an opening in the side
of the carrier..which is NOT in the "new and improved" versions..and
there is no washer/rivet

The cracks in the powdered metal...appeared at the junction of the
tang (see screw #12) and the body of the carrier, around the area of
the pin hole(s) where the carrier rocker is attached.

I really should have taken some photos dang it..Im set up for macros.

Shrug.

And indeed...it is a very lightly loaded part..which is why I was most
surprised to see the crack. Then.. I put the part under the
microscope and could see the granular make up of the material in the
area of the hairline cracks.

I was given this part to repair....and not the entire rifle..so I
honestly dont know what condition the rest of the arm is in. The owner
is a gentleman and gun owner of some note..so I cannot believe he was
hammering or otherwise stressing that part. He may have horse traded
for it from someone. No idea of even the age of the arm, but I just
put in a call and Ill ask him about the age range when he calls back.

Gunner

[Gunner Asch]

#
#I was given this part to repair....and not the entire rifle..so I
#honestly dont know what condition the rest of the arm is in. The owner
#is a gentleman and gun owner of some note..so I cannot believe he was
#hammering or otherwise stressing that part. He may have horse traded
#for it from someone. No idea of even the age of the arm, but I just
#put in a call and Ill ask him about the age range when he calls back.
#
#Gunner

I just got a call back from the owner. He says he doesnt know the age,
but remembers it came from a version that had a 2 yr range of
manufacture and after that..it was changed internally a bit. When he
gets home, he will look up the years of manufacture.

[Stanley Schaefer]

On Apr 29, 4:54=A0pm, Gunner Asch <gunnera...@gmail.com> wrote:
# #

# #I was given this part to repair....and not the entire rifle..so I

# #honestly dont know what condition the rest of the arm is in. The owner
# #is a gentleman and gun owner of some note..so I cannot believe he was
# #hammering or otherwise stressing that part. =A0He may have horse traded
# #for it from someone. No idea of even the age of the arm, but I just
# #put in a call and Ill ask him about the age range when he calls back.
# #
# #Gunner
#
# I just got a call back from the owner. He says he doesnt know the age,
# but remembers it came from a version that had a 2 yr range of
# manufacture and after that..it was changed internally a bit. When he
# gets home, he will look up the years of manufacture.
#
# Gunner
#
Subract the first two serial digits from 2000 to get the year, e.g.
"21" means 1979. What you describe is a cast version of the old-style
machined carrier. Haven't seen one of those, hence my confustion, and
if it were mine and a shooter, I'd probably replace it with the new-
style version. That's if a new carrier could be found for it. They
all interchange. Brophy doesn't describe all the production changes.
Looks like this was another short-run cost-cutting attempt that was
dropped later. The sheet metal ejector was another such, which that
drawing also shows. Unfortunately, there's no substitute for those.