Cool.

What about nickel or chrome plated steel bolts? Strength of steel, but those will be somewhat rust proof.

I looked at mcmaster-carr to see if they had these, and in the bolt section they have some nickel/copper alloy hardware that's apparently used on boats and will not rust as readily when in contact with salt water. Would want to check to see if there's any lead in those, though, and other drawback includes smal selection of non-metric sizes (i.e. limited).

Hi Jed:

I got those bolts at the advice of a guy who's been servicing espresso machines for decades. He said zinc plated would be good but the main point was to go for this grade of steel and protect them using anti-seize compound. He warned me away from stainless as that's softer than regular steel, so when tightened down the threads can strip. He also warned me away from using brass nuts as different metals tend to react to each other.

Doc G, I read that in your earlier posts!

I was asking about other alternatives which were not mentioned; this includes nickel and/or chrome plated steel, and the corrosion resistant nickel/copper alloy found at m-m. Combination of curiosity, seeking understanding, and ever so slightly a possible restoration project of my own. I wouldn't use zinc-plated hardware, that stuff's made for outside doohickeys like fences and lawnmowers.

ss is not necessarely softer but more brittle. when ss bolts break they do so more rapidly. they also can seize in combination ss bolt/ ss nut. anti seizure compound can prevent this. very important is to use a torque wrench. over-torqueing is the main reason for seizure.
ss is being used in all kind of application especially in the food industry, heat and pressure involved...
the boiler pressure is barely 1.4 bar, the temp less than 120 degrees celsius. that's nothing in comparison to many industrial applications.

drgary wrote:Hi Jed:

I got those bolts at the advice of a guy who's been servicing espresso machines for decades. He said zinc plated would be good but the main point was to go for this grade of steel and protect them using anti-seize compound. He warned me away from stainless as that's softer than regular steel, so when tightened down the threads can strip. He also warned me away from using brass nuts as different metals tend to react to each other.

Black oxide should be fine. Or you can gun blue them.

I just made a bracket for my daughter's crib out of 1/4 steel rod - heat treated it and gun blued it. Took all of 5 minutes, but it came out nice. You can buy super gun blue at any store which sells gun supplies usually. Here's an example of how the finish looks (my hook on top, the original one on the bottom; one was missing when my girlfriend's parents gave us the crib).

Do the bolts go clear through a flange on the boiler or do they thread into the boiler? If the bolts go through and then there is a nut on the other side, then there is no reason not to use Stainless Gary. I would use 316SS though and just make sure you use anti-seize on the threads (and as mentioned above, don't over torque them).

If you want to get really trick, use Titanium. Steel is fine also. I personally am not a big fan of zinc plated stuff. I think it looks cheap myself.

As long as your espresso machine never finds itself at the bottom of the ocean, then using SS or steel should be fine. You keep your stuff so clean and serviced that I don't think you need to worry about having any problems with the bolts. But if you use SS, definitely make sure you use anti-seize on the threads. I think you mentioned the torque on each bolt is only about 25 ft/lbs. You aren't going to get into any galling issues or have any thread binding problems with that sort of torque.

Steel bolts are stronger than SS, but if you have a bunch of nuts and bolts, then I don't think it will make much difference.

Use allen head cap screws if you have room. They look nicer and are generally easier to work with than hex head.

Ray

Thanks, Ray. I've got the bolts pictured above, which are not zinc plated. They are not stainless steel but are grade 8. I've also ordered food safe anti-seize compound. What would bluing add to this?

At this point I'm going to use the bolts I've got because it's time to move this project forward and as you say, I'm not going to over-tighten and I will make sure the machine is well-maintained so they don't create the kind of stuck bolt problem I struggled with earlier in the thread. The bolts thread through a flange at the outer edge of the boiler and I promise not to leave the machine with the case off in the rain, which is close to what might have happened to it before I got it.

drgary wrote:Thanks, Ray. I've got the bolts pictured above, which are not zinc plated. They are not stainless steel but are grade 8. I've also ordered food safe anti-seize compound. What would bluing add to this?

Those look pretty zinc plated to me, but it's hard to tell from the photo. Most hardware store stuff is either zinc plated, black oxide or stainless.

I personally don't care much for zinc plated, but I also spend $75 for one nut on my motorcycle Zinc should be fine for what you are doing. Stainless steel is my 1st choice for your application though (316 alloy, not 18-8).

If the bolts are stainless (i.e. designed not to rust), you aren't going to be able to blue them, because bluing (as TomC correctly points out), is a form of oxidation (i.e. rusting). Stainless is designed not to rust. If they are zinc plated, you also can't blue them, because you can't blue zinc. If they are raw steel, then you can blue them, but I doubt very much that they are raw steel, because they would rust all over the place (just from the moisture in the air or by the sweat on your fingers, etc.) if they were.

Also, SS usually only has slightly less tensile strength than steel (depending on the grade, etc.) But you certainly wouldn't describe stainless as "soft". It's actually probably harder than most steel, due to the nickel content of the alloy ("hard" being a different measure than "strength" - in other words, glass is hard, but it ain't very strong). Either way, the strength of stainless bolts should far exceed your requirements here - by a mile.

I don't know what kind of nuts and bolts you have purchased there, but my vote is return them to the hardware store and buy some 316SS hardware off McMaster.com - if you really want a first class job with this I mean.

Ray