Stainless Steel bolts for pellet stoves?

Hello

I like the resistance to corrosion stainless steel bolts have, however they can stretch and snap!
Galling can also occur. There are harder formulations of SS bolts however the common SS bolts are 304 Stainless Steel 18-8 which is 18% Chromium and 8% Nickel
Example of 10-32 Hex Tap bolt
Hex Bolt - Stainless Steel Bolt | #10-32 Hex Tap Bolt 18-8 Stainless Steel

They are not much harder than grade 2 steel bolts. See chart below.

Therefore is Grade 5 or Grade 8 better to use in high heat places like the fire box?
That is the area in question?

Also is there a way to tell what grade this bolt in the pic below is?
It holds the glass bracket in the 25-PDVC Fire Door

 

I prefer the grade 5 or 8 in the stoves.
Inside the firebox for the glass clips I like the Allen head or button head Allens.
Just slobber the never seize into the threads before snugging them down.

Use the never seize compound in the caustic areas like the fire box.

The big killer is that the factories use the self tapping screws, and these make a very tight thread with little to no clearance in the threads to hold any lube.

This is why these screws are so hard to get loose once they corrode a bit.

The sheet metal stuff is pretty benign, and gives minimal issue

As you mentioned the stainless steel can stretch and twist off.

If the stainless bolt is threaded into cast iron (Door etc) and or mild steel the galling is far less of an issue.

Stainless bolts with stainless nuts (Same materials) can gall easily.

The biggy is to use the never seize anywhere there can be a caustic and or a chance of rust and or a hot area.

 

Thanks for your comments Snowy, I am still looking for some good 10-32 bolts locally. Got one more place to try.

 

I just bought a bunch for the project stove this afternoon.

10-32 and some 1/4-20

Our local ACE hardware has a great selection of screws, bolts, nuts, washers and all manner of fasteners.

A pellet stove guru's heaven for sure.
They carry most of the rope seal, paint (If ya like black) bronze bushings, and just about everything you can want.

 

I just realized that the bolts I removed from the Englander door glass brackets had no markings so according to the chart I posted above, that makes them Grade 2 so SS or Grade 5 or 8 is still better.
What grade are the original bolts that you removed from your Whits?

 

NOT sure.

Vintage rust grade
The self tapping screws are a lot harder than most regular bolts to be able to actually cut threads.

I am thinking that the threads may be case hardened to about.030" or ???
Several processes that could be used to get the threads really hard and still leave the core material tough and not brittle.

A regular grade 5 or 8 bolt/screw is very tough with good tensile strength but they will not cut threads, and if there is any issue with the threads they will gall and tear the threads.

Grade 5 is a good all around bolt to use for mechanical things.
Grade 8 is much much tougher, and is normally not used except in conditions where extreme strength is needed.

Brackets on truck frames, heavy machinery etc.

Standard grade 2 (Butter bolts as they are called in the machinery building trade) are fine for bolting wood beams together and light duty tasks that do not require high tensile strength.

Here are a couple pix of the new self tapping ones I bought recently for use outside the fire box in the chassis and sheet metal.

As I mentioned before, in the fire box I like to use Allen head screws.

These are generally grade 8.

The good purchase in the socket head with the Allen key can allow the ability to remove them easily.

Buttttttttttttttttttttttt, they can rust/corrode in the hellish environment of the firebox unless treated.

I think JT mentioned the copper anti seaze.

A tube in the tool box or on the bench is worth a lot.

Far better than all the Blaster stuff.

Prevention is better than remedy any day.

Glass clips
Exhaust fan set screws and the shaft as it slides on
Auger motor shaft where it goes into the auger
The auger set screw/bolt
A dab on the door hinge pins and latch pin.

Great stuff.

If the factory did nothing more than use it on the exhaust fan set screws and the glass clip screws, life would be 1000% better for the poor soul having to work on these wretches down the road a few years.

But the assembly floor at the factory is not geared to this sort of "Detail work"

If I was selling stoves I would do a few of these little niceties during pre-delivery just to make life better down the road.

CAUSE YA KNOW WHO IS GONNA HAVE TO FIGHT THE SUCKER LATER ON

 

Those self tapping screws are very nice. What size are they?

 

10-32

I bough a big selection of screws, nuts, bolts and such to have on hand during the process of rebuilding the stoves.

Always seems that I get ready to put parts on and the originals are rusty, been replaced with the wrong stuff or just left out.

I hate "HASH" (Stuff done shoddy)

Ahhhh, I found some specs on the self tapping screws

Case hardened to 45 Rockwell C to a depth of .004" to .009"
Core hardness is about 35 Rockwell C

45 C is pretty good.

These are favored by the stove builders as they greatly simplify the assembly process.

The holes in the parts are all either punched or jig drilled when they are made and the assembler simply uses an air or electric driver to install them in the part.

To tap all the holes would take a huge amount of time and labor costs would soar.

Tapping would be better, and is certainly preferred when repairing a unit as the threads are better formed.

A lot of the threads from the self tapping screws are either poor or nearly torn out when they are first done and after a few times apart for service strip out leaving no threads at all.

 

The earlier Whits had the hardened steel "Quick nuts" (Hardened steel clip that slipped over the edges of the sheet metal in certain places and were fitted with regular machine screws.

This was a very nice touch, but undoubtedly added costs that the manufacture felt was unwarranted and the practice was discontinued in favor of standard sheet metal screws.

 

Hello

Well I ended up going with 10-32 Stainless Steel bolts and SS washers, I finally found.
They are still better than the #2 original bolts that were in there and with the Dry Moly on the SS threads going into a different metal in this case cast iron, there should never have any galling.
I like the Dry Moly better than never seize because it is dry and not greasy.

Pic 1 - Stainless Steel 10-32 bolts and SS washers
Pic 2 - Dry Moly on Threads
Pic 3 - Bolts in Fire Door
Pic 4 - Repainted Fire Door with clean glass, new graphite impregnated glass flat tape gasket, and new graphite impregnated Fire Door 3/4" gasket

Click pic to enlarge: