[tjbaudio]

As I look at all the conversions for small mills like the x2 I see a mix of aluminum and steel parts. I am planing a similar conversion and was wondering if mixing these causes any corrosion problems? I was planing on all the machined parts being aluminum because I can machine it fairly easy. However they will be bolted to the cast iron machine and probably mild steel parts mixed in as well.

I did some searching here and on google. Found lots of info saying its bad and special precautions need to be taken. At the same time I see lots of builds here that mix the two with no isolation.
Thank you.

[SCzEngrgGroup]

As these machines come from the factory, many of the contain aluminum parts bolted to steel and cast iron parts. You're worrying over nothing.

Regards,
Ray L.

[awerby]

Just don't try to operate it underwater, especially under the sea...

Andrew Werby
www.computersculpture.com

[691175002]

Technically a problem, doesn't really happen in practice. If your mill is in a situation where it will rust, you are screwed regardless of whether the aluminium speeds up the process.

[tjbaudio]

Technically a problem, doesn't really happen in practice. If your mill is in a situation where it will rust, you are screwed regardless of whether the aluminum speeds up the process.

Thanks guys. I was just thinking back to all the pluming projects I had when I bought this old house, LOTS of various metal parts and all corroded to crap at transitions.
I tend to leave it with a film of oil or wd40. No water or water based coolants at this time.

[outsider787]

TJBaudio,
If you're really worried, you could always anodize the aluminum parts which helps resist oxidizing (rusting) of the aluminum.
However as most have already replied, the dis-similar metal corrosion is not really an issue in the life of your mill. You may have seen corrosion in metal parts in your old house because the house is OLD. I would imagine you're talking about 50-100 year old home. If you keep your mill that long and pour regular tap water on it regularly (coolant I believe is not corrosive) then your mill may suffer the same fate, but I doubt your mill will be around in that kind of time frame.

[steve123]

How about about steel bolts into aluminum. Is there any advantage to using stainless bolts vs. alloy?

[outsider787]

Stainless steel tends to have better corrosion properties and is generally a stronger alloy then alloy steel.
The price difference is also significant as stainless steel parts tends to be more expensive.

If you're using proper coolant (which usually have rust inhibitor compounds mixed in) there's no need to worry about parts rusting (at least not in your life time).
On the other hand, if salt water is your only option for coolant then stainless steel bolts will outlive the rest of your machine

[SCzEngrgGroup]

Mixing stainless and mild steel is a BAD idea, as stainless is prone to galling, which can make the bolt nearly impossible to remove. And there is really no tangible advantage - the cost is much higher, the extra strength, if any, is simply not needed. Most of the time, "good enough" is good enough, and "better" really isn't. Look at how the basic machine is built, and follow that lead, rather than looking for potential problems. You'll likely just create more problems for yourself by trying to "improve" everything.

Regards,
Ray L.

[hoss2006]

How about about steel bolts into aluminum. Is there any advantage to using stainless bolts vs. alloy?

This chart on galvanic corrosion shows steel hardware in contact with aluminum base material poses marginal risk.
Stainless is no better.
Hoss

[outsider787]

This chart on galvanic corrosion shows steel hardware in contact with aluminum base material poses marginal risk.
Stainless is no better.
Hoss

Thanks Hoss.
The chart also shows that aluminum and cast iron (what most of our mills are made of) also have very little interaction with one another (on a galvanic level) which was the original question in this thread.

[RomanLini]

Mixing stainless and mild steel is a BAD idea, as stainless is prone to galling, which can make the bolt nearly impossible to remove. And there is really no tangible advantage - the cost is much higher, the extra strength, if any, is simply not needed.
...

Generally that's right but there are still advantages to stainless bolts. I rebuild old Harleys for fun and I only stock stainless steel bolts, as I live somewhere hot with high humidity and things tend to rust here.

I have not had a galling issue with stainless bolts in steel or aluminium (which I do all the time) but I'm also in the habit of using blue (light duty) loctite (I think 243?) on all bolts it means they never vibrate loose but are still easy enough to remove, and I'm not in the habit of overtightening bolts (which you don't need to do with loctite, thebolts can be tightened to the correct torque instead).