MetallicaJunkie

stainless steel, or alloy steel in terms of torsional(sp) strength?. I want to be able to tighten a bolt with out having to worry that it will break or strip on me.... ive had that happen to me with zinc bolts from the hardware store

Jetdesign

My Feedback: (8)

Depends on the steel; stainless steel is an alloy, and there are different grades. Also, you want the highest tensile strength, not torsional strength. Torsional strength would only matter if the bolt was seized. If you are able to turn the nut on the bolt and it breaks, you are actually pulling the bolt apart, not twisting it.

If you can find a tempered or hardened steel bolt, it will have something like double the tensile strength of a standard carbon-steel-alloy bolt.

While this chart is for larger, industrial grade fastners, it will give you an idea of the materials and tensile strength of bolts made of different types of steel.

http://www.americanfastener.com/tech...ings_steel.asp

Since 'stainless steel' is tempered, I'd go with that.

MetallicaJunkie

http://www.microfasteners.com/catalo...cts/SSCSCA.cfm http://www.microfasteners.com/catalo...cts/SSCSCS.cfm those are the two choices i have.... i want to place an order ... i just want to make sure i order the screws i can tighten the most without worrying about breaking the screw.... im tired of paying 40 cents ascrew when i can get 50-100 for 10 times cheaper ordering in bulk

Jetdesign

My Feedback: (8)

stainless would be the stronger of the two.

bkdavy

My Feedback: (1)

Perhaps some insight on your application might help us help you. Insufficient tightening might not be your problem. For example, if you're using zinc to replace your head bolts, the temperature will cause differential dimensional changes that will cause bolts to come loose. If you're just mounting them into blind nuts on the other side of balsa, you'll crush the wood before you'll break the bolt, even with zinc.

Brad

jetmech05

any screw will strip...either the threads on the bolt or the hole or the nut...something is gonna give....don't over tighten...tight is tight...if after its tight, it becomes loose then it's from heat or vibration that makes it come loose.....safety wire or a lock washer or a cotter key is the answwer not more torque

bruce88123

Not necessarily. Read here under "types or stainless steel" http://en.wikipedia.org/wiki/Stainless_steel .

j.duncker

My Feedback: (2)

OK most hardware stores will sell you low quality steel nuts and bolts. WHY THEY ARE CHEAP.

The tensile strength will be low and the threads will be loose.

If you want to get a better nut and bolt then go to aircraft quality.

SOURCE http://exp-aircraft.com/library/alexande/hardware.html

Stainless steel bolts come in a wide variety of strengths and again those from a typical hardware store will be of poor quality.

There is a supplier of better nuts and bolts that advertises here. www.rtlfasteners.com

MetallicaJunkie

i want these to be strong enough for a bolt through set up on my glow engine exhausts(metal-metal)....i tighten them by putting a nut on the other end to tighten the mufflers. I bout some 2" zinc bolt at the HW store and before i am satisfied with the tightness they break. I would like to use them for motor mounts and stuff like that too, that dont require that kind of tightening

edit thankyou for your input

Adui

Keep in mind that muffler is only aluminum if memory serves me. (Correct me if Im wrong here guys) Even with the backing nut if you over tighten it it could damage other things..

MetallicaJunkie

you are right, but after about a couple of flights of using the bolts from the hardware store(zinc) torqued to the point right before breakage would loosen up....

jetmech05

Gentlemen its not just my name but my job as well...aircraft quality hardware still strips when over torqued..as a matter of fact tightening something just before the breaking point can cause the threads to stretch..and help the bolt to loosen...if your are using through bolts on your muffler and it still loosens...then all you need are crown nuts or jap nuts..these are lock nuts without nylon inserts...you should be able to get them at a good hardware store....

jaka

Hi!
All the black Allen head bolts you see on model engines are harder!
Those are the ones you need! Could be found in lenghts from 4mm -60mm.

bkdavy

My Feedback: (1)

The exhaust bolts are probably subjected to the highest heat of any part on the engine. If I'm not mistaken, the original parts from most manufacturers are probably a specially hardened (heat treated) bolt. For that application, you're better off getting the replacement part from the manufacturer. Zinc will not work in that environment because the heat will soften the metal and lead to deformation. Additionally, I think zinc in contact with aluminum will actually cause preferential corrosion of one or the other (galvanic corossion).

Use locktite on the manufacturers screws. There are versions that are meant for high temperature applications. Also consider adding a gasket which will allow some compression and help resist the screw vibrating loose.

Brad

MetallicaJunkie

thankyou guys for all your help, and suggestions. I will play it safe and go with the black alloy bolts from http://rtlfasteners.com/RC/b.html thanks to those who reccomended them