Plastic filler tips.
I work with an apprentice and I thought I would pass along some things that have helped him.
1. I have started using a procedure that really helps with feeling the filler. A lot of what you are feeling on the final stages finishing off filler are scratches or irregularities in the surface texture and not highs or lows in the filler. When block sanding you are of course going in a number of different directions, this causes an irregular texture that can be felt and throw you off, good and bad ways. You could "think" there is some high spot there that you need to block (and you continue sanding) all the while it was perfect and you were feeling this texture of scratches from previous blocking.
So, what I have begun to use on a regular basis is a piece of 400 and sand the panel in a circular motion to "kill" all the irregular scratches from the blocking.
It works like a charm and you can REALLY feel what you have. The bad part is (or is it good) that many times it is not done and what I thought was perfection is far from it. All I know is now the job goes to the paint dept I KNOW it is right.
2. Be sure it is stripped out far past your filler work. If you are applying epoxy primer to the metal prior to filler work this tip still applies. You need to be way out past your dent with the epoxy. On most restoration projects like you guys are doing this is a moot point of course being the whole panel is likely stripped and possibly covered in epoxy primer. In this case you don’t strip the epoxy off. But you can still use the concept of what I am referring to in that you need to you’re your filler work well beyond the dent. To have a skim coat of transparent polyester putty out over straight metal is no big deal. You need to be feeling METAL and filler only. If you have a poor feathered paint edge that is going to throw you. You are going to need to feather edge it sooner or later, you might as well do it as you do your bodywork. I will always cut the paint off the panel for the repair with 80 on a "hog" but not getting into the metal much if at all. Just cut thru the outer paint layers. Then I switch to 120 on the DA and feather it out further. This way, there are NO 80 grit scratches that could ever be on the feather area where filler isn't covering. If you have metal (or epoxy primer) with 80 grit scratches it MUST be covered with filler or putty (polyester of course). So, if you feather edge out past where you are going to apply filler with 120 you are safe with primer going over that. I rough cut the filler as per my “Basics of Basics” on plastic filler and feather out the paint even more if needed. All I know is when that skim coat of polyester putty is applied it is completely covering any 80 grit scratches in the roughed out filler AND the surrounding metal or epoxy primer.
3. You don’t need to cover the whole area in one application of filler or polyester putty. If you are having a hard time to get it all out smooth before it “kicks”, then break it down into manageable areas. For instance, you would apply the filler or putty only below the body line of a dent that covers above and below the line. Then after you clean your tools and mix up some more and apply the filler to area above the area above the body line. You can even apply filler over the filler before it is sanded. Say you got your filler on and see that there was an area you didn’t apply quite enough, just mix a little more and apply it over the thin spot of filler previously applied. As long as you do this within a short period of time before the filler is totally cured it will be just fine.
Even if you don’t have a body line or some other break off point you can apply the filler feathering out the edge thin with pressure on your spreader and then continue the spreading with newly mixed filler starting at that thin feather edge until the whole area is covered. It isn’t a big deal that the edge is feathered out thin, but it helps to do that and start the additional filler back onto the first section over the feather edge a few inches so that you don’t have a big line at the meeting point.
4. The absolute biggest trick in doing filler is getting the surrounding areas or any area where metal is showing to be transparent. I can’t stress that enough. If your filler ends abruptly and there is shiny metal right next to it, there is a high spot there. The filler should be transparent as it feathers off onto the metal or over metal that “pops up” in the filler. If you work from the outside (straight metal) in towards the center (damaged metal under the filler) and the feather edges are transparent you are going to get the thing flat.