What is the benefit of adding bronze, tungsten, or stainless steel powders to the bedding material?

Other than adding some weight to my .458 Lott, I can't see how powder can strengthen the epoxy.

Thanks

Minkman

quote:

Originally posted by Minkman:
What is the benefit of adding bronze, tungsten, or stainless steel powders to the bedding material?

Other than adding some weight to my .458 Lott, I can't see how powder can strengthen the epoxy.

Thanks
Minkman

Added strength and more resistance to compression forces. I use Devcon Titanium putty/epoxy which resists compression forces in excess 18,000 psi and can be machined, threaded, and it isn't affected by most chemicals and solvents. It ain't cheap but it's about the strongest stuff around.

Hate to disagree with Rick, but adding powdered metal to an epoxy glue does not do squat. It makes it shiny and they jack up the price. For metal to have any impact on the compressive or tensile strength, the particles have to be joined in a steel matrix and not in glue. Epoxies can also be machined and threaded all on their own.

Regular AcraGlas will not compress any more than AcraGlas with metal shavings in it.

When it cures, it is hard as a rock and still easy to machine.

I have some atomized bronze powder which I have experimented with and have not found a single advantage to using it over normal AcraGlas.

-Spencer

At the obvious risk of starting a big thing on here, especially with two guys whom I admire, I will only state that in my experience using epoxies (which is not limited to just bedding rifles) and based on numerous discussions with the tech departments of different manufacturers I would respectfully disagree.

Adding metal to an epoxy increases the density of the epoxy and in turn increases the resistance to shearing, impact and compression forces on the cured product. It is not just a "marketing-gimmick" thought up at Brownells.

I have been working in the motion picture business for a little over 30 years as a stunt man and I work very closely with special effects technicians who started adding powdered metal to expoxy many years ago to strengthen it up for specific uses requiring more strength. The military also did this many, many years ago for the track repair kits for the tracks on tanks and AMTRAC's, which included epoxy. Some of the USMC sniper armors actually used the epoxy from those repair kits to bed sniper rifles in Vietnam.

quote:

Originally posted by Customstox:
Hate to disagree with Rick, but adding powdered metal to an epoxy glue does not do squat. It makes it shiny and they jack up the price. For metal to have any impact on the compressive or tensile strength, the particles have to be joined in a steel matrix and not in glue. Epoxies can also be machined and threaded all on their own.

I'm on this side of the discussion!!

However with Brownells runny stuff....not the Gell now... I mix walnut dust from the belt sander to the prepared acraglas only as a stiffener. In other words to make it less runny so I can use it somewhat like a Gel. This has worked well for me but would be remiss to say that it improves the strength of the hardened product.

It certainly works good as a glass bedding compound however.

Rick has it correct. The various fillers do add strength to the final matrix. STeel is better than bronze, Ti is lighter than steel and very strong. I have studied this to death in engineering grad school and done god only knows how many destructive tests on various plastics, composites, epoxies, whatever. It makes the resulting matrix stronger in compression-just fact. It is very hard to measure for the average person though. Unlike crooked barrels, where anyone with a lathe and test indicator can see the run out!

I stand corrected then.

As far as for use with bedding compound, I really cannot see how this will make any real world difference.
Sure, when you are working with machinery and high pressure, high use stuff, I can see why you would be looking for the strongest stuff possible, but not so important for gunstocks.

-Spencer

http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Structure/composite_class.htm

There are a lot of articles on the web, but this summary is written in pretty plain English that the average non-engineer can understand

THink of the forces from the recoil lug to the stock material during firing. It is a very viloent process with a lot of compressive stress. In order to resist deformation, you need a strong bedding compund. THe stornger, the less it will move and deform.

Heck, I might as well throw my two cents in. In my first life I worked with some very high dollar and very strong industrial expoxy's, they all had metal of some kind in them. I'm of the opinon that anything you mix, fiberglass flock, metals etc adds some strenght...........but how much is a question most of us can't answer and you may or may not be able to live on the difference in bedding a rifle.

I'd have to say the boat builders probably understand that question better than most, and bet they say boats built with a chopper gun are not as strong as using cloth, but stronger than just resin. If I had to bet, I'd say something is better than nothing.

Now here is what I think is really important..........how much does it shrink over time, I think the modern expoxy is plenty strong either way....but some shrink more than others. You can look at the specs and some brands have more shrinkage than others thats for sure. And with that I say, if you doing a wood stock do a good job inletting and forget the expoxy.............not that I'm at that point yet........but getting closer

Ok I'll bite too. How can powdered metal have any strength ? Wont adding it to epoxy actualy displace epoxy and create a less dense substance than 100% epoxy ?

Here are the tech specs for the Devcon Titanium Putty that I use...I don't use, nor do I know a damn thing about using Acra-glass or Acra-gel.


Cured Shrinkage = 0.0010"

Adhesive Tensile Shear Strength= 2,000 psi

Compression Strength = 18,800 psi

Flexural Strength = 7,700 psi

It is listed as: A high tech, titanium reinforced epoxy putty engineered for making critical repairs to industrial machinery and precision parts that require a machined finish.

It is highly resistant to heat, solvents and other chemicals.

I have seen this stuff used to repair both pnumatic and hydraulic rams used in motion picture special effects equipment used for decelerating and accelerating both people, and objects up to the size of automobles and even larger, on cables.

Thanks Guys,

Now I'm not sure if this is the way to go.

How about strips of glass mat or cloth. This I think would add some rigidity.

Thanks

Minkman

My main means of livlihood in my life was as a civil engineer. For a time I was the materials engineer for the Wa State DOT. College studies included strength of materials, stuctural engineering and mechanics of materials. Just stating my credentials. You can take it or leave it.

The hype is not on Brownells although they may well be feeding on it. The hype is perpetrated by the companies making it. Adding powdered metal in a matrix of epoxy will add to the density of the final mix as the metal will almost always be heavier than the epoxy it displaces. It will not add to the strength as the metal particles are individual in the mixture and have no opportunity to act as a unit. Shear strength of a material is a measuere of the resistance to the shear forces. The metal in the mixture does not contribute. It can't.

I correspond with Rick often and I do not worry about disagreeing with a friend such as him. We can surive these differences of opinion.

I am going to do some searches for strengths of various pure epoxies and maybe the comparisons will help.

Epic Resins

0114
"Epic 0114 is a one component, rigid epoxy adhesive. It features excellent physical properties and good adhesion to metal. 0114 is a high viscosity adhesive that cures in one hour at 300 degrees F and exhibits tensile shear strength of 3,500 psi."

S7055
"Epic S7055 is a two component, 1 to 1 mix ratio by weight, epoxy adhesive. It is a thixotropic paste that exhibits a tensile shear strength of more than 3,000 psi when cured at room temperature. S7055 is an excellent adhesive for polyester or epoxy composites'

S7033
"Epic S7033 is a general purpose, versatile epoxy paste adhesive with a convenient 1 to 1 mix ratio. S7033 features a two hour pot life, tensile shear of 2,800 psi and an overnight cure to handling strength."

Hexply formulated Epoxy resin link

"hexply is a formulated epoxy resin.

Flexure strength 19.7 ksi (19,700 psi)"

I was not able to find any compressive strength figures on pure epoxies. A lot of information on epoxy and other material laminates were shown but it is of no value in this discussiion.

Hey, Chic...I never get upset or pissed in these discussions because I can't recall a one of them where I haven't learned something I didn't know before.

I don't have your background in engineering or in rifle building...but I have used a ton of epoxies over the years and through personal experience I have observed that the Devcon line of steel based expoxies are much stronger and will withstand far more compression forces than any plain based epoxy (including Devcon's) that I have seen or used.

Granted, we may be talking about a degree of strength that has no practical advantage with what rifle bedding is subjected to, but being too strong shouldn't pose any problems either.

Scientifically, my theory and observations may not pass muster...but remember, it was a Scientist that said, aerodynamically speaking, that Bumble Bees can't fly!

Hi Guys (my 1st post ,

Some trawling of the Devcon web site yielded the following table. Note the compressive strength of the Ti putty, and compare the compressive strength of the plas steel liquid with the 2 Ton epoxy. I'm only an electronics engineer - can anyone work out the pressure exerted on a recoil lug bearing surface so we can work out what compressive strength we really need?

(Sorry about the table formatting - wont hold the format from the edit screen)

Murray

Epoxy Adhesive Compressive Flex Shrinkage
Plastic Steel Liquid 2800psi 10200psi 7480psi 0.0006 in/in
Plastic Steel Putty 2800 8260 5600 0.001
Stainless Putty 2385 8400 5280 0.001
Titanium Putty 2000 18800 7700 0.001
Aluminium Liquid 2700 9820 3540 0.0009
Bronze Putty 2680 8540 6180 0.001
Carbide Putty 1350 8160 5480 0.0009
2 Ton Epoxy 2250 11000 ? ?

These look pretty good figures - anyone know what the corresponding figures are for low temp (as in not action or barrel wrecking) silver solder or to put it another way are some of these high end epoxies capable of being used for mounts?

Rick,
there may be some advantage to an additive for compressive strength. I did see where fly ash was used as an additive and the strength fell off after 10% was reached. The idea of Portland cement concrete is another idea of additives, sand and gravel versus just the cement. We did compresseive strength tests on the concrete cylinders and also on "biscuits" made from just the mortar. For the life of me I do not remember the relationship between the two. In concrete, the mixture had other properties that were beneficial also.

Chic,

I'm sorry...but I draw the line at burning up a bunch of poor little flies just to make epoxy stronger, I don't want to get the PETA crowd coming after me!

Hello the campfire:
What properties are we takling about as desirable in bedding materials? Please excuse my lack of knowledge, but it seems to me that the ideal bedding for recoil lugs and rear tangs would be a steel or at least aluminum. I refer to OLD Gunsmithing books that advised inletting a small steel plate beming the recoil lug and spotting the lug to it with Prussen Blue. As most of us are not as good at fiting steel as epoxie, this has taken over.
But what in fact do you gain by bedding this way over wood? Stability maybe, resistance to fiber compression over years of shooting, repeatability?
I can understand routing the whole action out of a stock and bedding the whole action, but just bedding the recoil lug and rear tang seems to me a way to get away with sloppy wood work.
How much bedding do you need? .10 inch, .25 inch? what does it actually take to make a differance in the accuracy of a rifle? If it makes that big a differance and you need( want ) that why not just go with a synthetic stock and bed directly to the stock with an aluminum piller system?
Inquiring minds are a little off to day.
Judge Sharpe

Rick,
Like Hugh Grant's Vegan blind date in Notting Hill (who would only eat fruit that has fallen from the tree and is already dead- damn spare me), we only take flies whose lives have ended and they died on my window sill. I have what is often referred to as a "shit pot of them."

Judge, fitting a steel plate the recoil area and then fitting the steel recoil lug to the steel plate seems incredibly redundant. No wonder it did not survive. The questioning mind of it's day no doubt found a better way.

Judge,

Like Chic said, that sounds pretty redundant. In addition you would then have a thicker recoil lug acting against an even thinner section of wood than you had in the first place.

Personally, I think any rifle worth bedding is worth pillar bedding...but that's just my opinion, and I am sure there are other ideas on the subject.