(12-12-2017, 08:30 AM)pprobus Wrote: Depends on what you are up against.  More rust than paint?  More paint than rust?  I can say that "sandblasting" (safety monitors might prefer the use of the term "abrasive blasting" as using sand can cause silicosis without proper respiratory protection) is not necessarily the best and fastest, actually, abrasive blasting can be downright slow, especially if you try to remove large amounts of sound paint, rust removal can be quick if its mostly surface rust, but deeper rust is slow going.  Like others have said, wire wheels in drills and angle grinders is about the best alternative to abrasive blasting (not either or, but depending on the case use of both tools with wire wheels), also, if you need to get into tight areas, the use of a dremel type tool with a wire brush can be helpful, too.  I don't really recommend the use of sanding discs in angle grinders as they will leave deep scratches and can remove too much metal, but the use of a pad or RO sander are OK if you have deep down rust.  Regardless of rust removal method, chances are you won't get everything, so soaking in Evaporust or equivalent is highly recommended.  Its supposed to be safe for paint, but I have found that it will soften paint so, if you have a piece that has mostly sound paint and only has portions with rust, if you can soak just those local areas in ER, try that, ER says that you can soak rags and place them on areas of rust if the part cannot be submerged, but I have not tried this method, or remove as much rust as possible, feather back the paint and use a rusty metal type primer and hope it works. 

If you need to strip large amounts of paint, the best method I have found is to use paint stripper.  But like others have said, if you have large areas of sound paint, treat the rust as above, feather back the paint around the rust repair with a pad or RO sander with fine grit sandpaper, roughen up the paint over the rest of the part to knock down the shine, then prime the rust treated areas  with a bare metal primer then use either a primer-sealer or primer that can be used over paint over the whole piece (rust repaired and roughened paint) and then put your top coat on. 

You're focused on the rust removal, but you also need to seriously consider the paint.  Are you planning on using rattle cans?  With all the work you're about to put in, you're going to use rattle cans?  While I do use rattle cans for priming because I was unable to find a local source for inexpensive self-etching primer (O'Reilly's autoparts carries it, now that we have them in my area), so I have been using Rustoleum self-eltching primer with good results (I have had to do some re-work due to paint issues and the primer is pretty resistant to abrasive blasting).  But use self etching primer only on bare metal.  If you want a better base, you need to move to automotive style epoxy primer (much more money too), but for machine tools that will spend the majority of their lives inside and not subject to the elements, I think self-etching primer is good enough.  Now the important part, the paint.  Yes, you can rattle can it, but frankly, I have found a lot to be desired.  My main complaint is that the "enamel" paint never hardens into a nice hard "enamel" and found the parts easily scratched (even after waiting a month on one piece, due to getting pulled into another project).   I have found that to get any kind of paint that will standup to the kind of abuse a machine tool will see will have to be a two-part paint, mixed and sprayed using a paint sprayer.  I know you say you don't have enough compressor for abrasive blasting, so if you do use a compressed air spray system, you will likely want to use either a LVLP gun or a conventional paint gun or some paints can be sprayed with those airless sprayers (Tractor Supply's paint recommends it).  As for the paint, I have been playing with a couple of different locally available, low-cost, enamel paints, Rustoleum and Tractor Supply's house brand (I think its Majic?).  They are relatively low cost and when you use the TSC hardener (Rustoleum does not offer a hardener, I have used TSC's with Rustoleum enamel with good results) in either paint you get a decently hard enamel paint that will hold up better than the paint sprayed without hardener, obviously its not powdercoating but much more durable than rattlecan or sprayed without the hardener.  The problem with those paints is that the color variety is lacking.  If you have a machine color that does not conform to Rustoleum or Majic's standard colors, you need to find a local paint supplier who carries enamels that can be mixed (not sure if the local Sherwin Williams or PPG dealers have enamels I mainly see them advertise house paints) and I am not sure about the step up in cost.    I just hate to see you put all your work into de-rusting and re-finishing your machines only to be unhappy with the final product, as I had been (luckily I noticed how easily the Rustoleum rattle can paint scratched before I completed the entire machine). 

Paul

(12-12-2017, 08:41 AM)pprobus Wrote:  I forgot to mention while talking about wire wheels, I have found the artificial wire wheels to work very well and they are less "grabby".  The one issue that I HATE about wire wheels is that when you get to the edge of a piece, the wire wheel can grab and pull the grinder/drill and either just mess up your rhythm or I have had it bend the edge on sheetmetal.  If you can aim the wire wheel so that the wheel is always spinning in a way it won't grab an edge, you can avoid that, but sometimes you can't or you are moving in a good rhythm and would have to stop to switch spin direction (on a drill) or shift position with a grinder.  The artificial wire wheels will grab, but are less agressive when they do grab (I think because the abrasive tears away) and they are less prone to grab.  The downsides are that they wear out quicker, are a bit expensive given their lifespan, they can load up with a "gummy" paint (not too common)  and are slightly less aggressive than wire wheels.

(12-12-2017, 09:13 AM)UpstateNYdude Wrote: When you say artificial do you mean the nylon brushes? Also what kind of cup wheel are you using the knotted or unknotted, I've been mostly using the unknotted version along with one of those hard porous abrasive disks to remove most of the paint. I have an auto body place almost literally right next door to me so I may see how much it would cost me to get them all primed and painted there.

(12-12-2017, 08:32 AM)Kudzu Wrote: If paint is old and loose it will make quick work of it.  If it is still strongly attached I leave it and sand the edges to feather it. If it still attached well there isn't a lot reason to remove it.

(12-19-2017, 11:09 PM)daddo Wrote: You can't beat sandblasting, however I don't use sand, but use "Black Diamond" grit instead.
I'll use the pressure washer on some items and it might get some of the rust off- sometimes a lot of it- it depends on how thick it is.
Wire brushes do ok but leave a lot of spots behind, especially in corners and nooks and that rust always tries to come back. Sometimes the wire just polishes the rust and makes it look like it is gone, but it isn't.
Here is a product I haven't tried, but it looks nice; http://www.nortonsandblasting.com/nsbpowertool-mbx.html

I know one thing- If you sandblast it down to the bare metal and paint it correctly, it won't rust for many years even in the weather. If you can get it blasted- do it.