Is it possible to etch a pre-drilled enclosure?

[mikemaddux]

If so:
What would be suitable to cover/plug the holes?
Should it be brushed on in this case?

It is just a regular 1590B.

Thanks

[GREEN FUZ]

It`s definitely possible as I`ve just done one. Take care to cover any areas you don`t want etched. I used blackboard paint from a spray can ensuring that the interior was also covered. You can touch up any areas you may have missed. You may want to take some extra precautions with the screw holes. I contemplated pouring melted candle wax into them, but in the end didn`t bother.

[mikemaddux]

Thanks, is it really necessary to dunk the whole enclosure in? (this is my first time=virgin etch  ) 
I ask this b/c you had mentioned something about protecting the screwholes.  Was this protection from dunking or some kind of splash?

I was really trying to avoid etching the inside.  Will any kind of tape hold up to the etchant? Possibly painters or duct tape or something similar on the inside of the holes? 

are the hole sizes going to change if they are etched.....i.e. etching a bigger hole?

I was planning on masking the top of the enclosure off and spraying the sides with black spray paint.  That spray paint should keep the sides from being etched while it sits in the etchant, right?

Thanks for answering the noob questions....

[GREEN FUZ]

Thanks, is it really necessary to dunk the whole enclosure in? (this is my first time=virgin etch  ) 
I ask this b/c you had mentioned something about protecting the screwholes.  Was this protection from dunking or some kind of splash?

How do you intend to apply the etchant? I have read reports of some people applying it in a very localized manner with a cotton bud or something similar. What I do is fill a shallow plastic tray with Ferric and dip the surface of the enclosure in while gently agitating the liquid, rinsing with fresh water to check the progress periodically. I was only suggesting covering the screw-holes as some extra insurance. If you`re careful, as I was, you shouldn`t need to.

I was really trying to avoid etching the inside.  Will any kind of tape hold up to the etchant? Possibly painters or duct tape or something similar on the inside of the holes?

As your enclosure has already been drilled it will be almost impossible to avoid getting some etchant inside, if you`re dipping it. I believe  tape can be used to mask off areas. I haven`t tried it. I wouldn`t be confident of achieving complete coverage. I guess it depends on the amount of time the enclosure is immersed. The longer it`s in there the more time the liquid has to get into all the little nooks and crannies.
Here`s a post about what can go wrong using masking tape.
http://www.diystompboxes.com/smfforum/index.php?topic=49436.0
It kind of put me off the idea.

Oh yeah, on a related note.
http://www.diystompboxes.com/smfforum/index.php?topic=61680.0
Thanks Jonathan (resident etching crash test dummy?) for both illustrations on how not to do things  . Shouldn`t laugh really.

are the hole sizes going to change if they are etched.....i.e. etching a bigger hole?

Possibly not drastically depending on the amount of time they are exposed to the etchant. My concern is that they would be weakened. I imagine stepping on the stomp-switch and the whole assembly caving in. That may just be paranoia  .

I was planning on masking the top of the enclosure off and spraying the sides with black spray paint.  That spray paint should keep the sides from being etched while it sits in the etchant, right?

Yup, that`s the basic idea.

Thanks for answering the noob questions....

You`re welcome. Good luck.

[bean]

Done it many times, myself. Use the "gravity etch" method. After you transfer your PnP, tape off everything that doesn't need to be etched. I usually use packing tape and then cover it with soft, tan tape. then apply the etchant with a small syringe over the areas you want to etch. The etchant will pool there. So long as you keep the enclosure level, you won't have much of it dripping off the sides (tape those too). You will need to apply several "doses". Between doses I put the top down in a pan of water then gently brush it off with a paper towel. Then apply another dose.

It should take 4-5 doses and about 15 minutes.

[axg20202]

If you haven't etched aluminium in ferric chloride before, be aware that this reaction is more spectacular than with copper PCBs. The rate of etching is much, much faster and considerably exothermic. You don't want the whole caboodle to heat up too much, so rinsing off the etched area with cold water regularly throughout the process will keep things cool and allow you to check progress. For lettering etc, you don't need to etch 3mm deep holes! You will lose definition around the edges of your design/lettering if you etch for too long, not mention etchant breaking through the masked off areas. Use a stopwatch and make a mental note to rinse and check at set intervals - if it works out great, make a note of your method and timings so that you can repeat it next time. If it goes wrong, you have a method to refine.

As for etching a pre-drilled box, shouldn't be a problem but obviously best avoided for less hassle. Maybe you could use cork to block the holes off?

[MikeH]

You either have to THOROUGHLY coat the inside of the enclosure with etch resist, or plug the holes.  Since it's hard to really coat the enclosure with resist- especially around the sharp angles where the holes are drilled, I think plugging the holes might be your best bet.  I'd suggest trying your local hardware; sometimes they have little bags with various sizes of rubber stoppers you can buy.  And maybe you can get the right sizes to seal up the holes.