Hard Coat Anodize + masking. Anyone have experience?

[E30TECH]

I'm looking to get some aluminum parts hard coated. However, some of the areas have small threaded holes (4-40) and need to be masked. I was hoping someone here may have some experience with this.

 

I was wondering if I can mask the areas by using Alodine.

 

Any insight is appreciated.

 

Thanks

[Jerry Johnston]

No experience but why can't you just put a screw in the hole? If you don't screw it in all the way it should be better than masking.

[E30TECH]

I thought about that, but forgot to mention it. I wasn't sure if a SS screw would be affected by the process. That would be the easiest way.

 

I would put an oring on the screw to help seal the hole.

[Lineareagle]

Not sure why you would want to plug the holes.

Typical hard anodizing, Type III, will generally add .002" to a part thus you are likely to see a .004" in the threaded hole. That is well within most screw tolerances and should not be a problem.

 

Even if it did make the holes a little tight you could CHASE the holes with a thread chaser and still maintain some of the benefits of anodizing the hole and get a good fit.

Chasing as opposed to re-threading, note.

 

 

 

 

[E30TECH]

I wasn't sure how difficult it would be to chase hard coat as I don't have much experience with it. I thought it might cause the threads to tear. I guess this wouldn't be the case?

[dwightm]

It has been awhile since I have had any anodizing done but this is what I remember.

 

The thread won’t tear, just put some cutting fluid on the tap or die. The .002 is the buildup the hard coat also penetrates into the aluminum just as deep.

 

If the holes need to be masked tell the anodizer they can take care of it for you. Don't put screws in the holes, anodizing is a electrochemical process and you could destroy the part.

 

[E30TECH]

I have no problem chasing the threads if that is the preferred way of doing it. I'm sending this thru with a job from work, so its a freebie. I dont want to ask the anodizer to plug the holes.

 

Thanks for the replies

[Spartan]

Plug all tapped holes. You will not be able to chase a hard anodized hole without destoying the tap. With normal .001 thick plating you will not get the screw in. The plater is set up for this and it should not ad to the cost of plating.

[E30TECH]

Plug all tapped holes. You will not be able to chase a hard anodized hole without destoying the tap. With normal .001 thick plating you will not get the screw in. The plater is set up for this and it should not ad to the cost of plating.

 

I was talking to someone at work and they said he same thing - the tap will break. I'll find out what the plater is willing to do.

 

Do you know what they plug the holes with? Teflon or rubber plugs?

[Spartan]

The plater will use rubber plugs. We designed and machined thousands of parts and had hard anodizing done almost every week for years. Plugging threads was standard proceedure with the several platers we used.

[E30TECH]

I have reprorubber quick setting putty at work. Do you think that would work? Since this is a "G" job, I'd like to do all the prep work myself.

 

Thanks for your insight

 

 

[Spartan]

I have no idea if reprorubber will work. I would just let the plater handle pluging the threads.

[James Clark]

I have reprorubber quick setting putty at work. Do you think that would work? Since this is a "G" job, I'd like to do all the prep work myself.

 

Thanks for your insight

 

 

Got candles?

[cali_beemer]

I am a mechanical design engineer and I have designed many items hard ano with masking. If you have threads you will definately want them masked. the build up on a hard ano is typically .002" each side (keep in mind a diameter builds up double), however I have seen platers go over that build-up. Dont assume it will be exactly .002" As noted already you will not tap into hard ano, that stuff is hard and becomes difficult top even machine. Alodine prior to ano is great if you are looking for corrosion protection in the threaded holes, plus if you go with gold alodine, which is the most common (or often reffered to as yellow), it looks really cool as well. Take note that the alodine will wear off relatively easy as its simply a chemical conversion coating.