The Rule of Thumb
The rule of thumb I use
is with my thumb, mostly because I always have it with me.
I use the distance from the tip of my thumb to the end of my thumbnail, which I just measured and it's about 3/4 of an inch and that's about how far away I stay from edges and raised body lines when I sand by hand or machine.
Actually a 1/2" is a pretty good rule of thumb the bigger idea is to
not sand paint where you cannot safely buff with a wool pad, a cutting compound with a rotary buffer.
This is a technique I teach in our wet-sanding classes to give students a simple method or a
simple guideline they can use to know just how far to sand when sanding near a hard body line or the edge of a panel. This is a simple technique that works for me but feel free to come up with your own method.
Show Car and Perfectionist Sanding and Polishing
For those of you wanting to do
perfectionist sanding and polishing, first make sure you're getting paid well because you can sand right up to an edge but removing your sanding marks has to be done carefully and this means it will require you to
invest more time into the project.
How to sand right up to an edge and remove your sanding marks by hand
There is a fix for the issue of sanding right next to an edge or a raised body line and that's by carefully sanding and then using Meguiar's M105 Ultra Compound by hand to remove your sanding marks. Another way to remove sanding marks next to an edge or to a raised body line is to use Spot Repair Pads on a rotary buffer using a technique I call
Edging.
Because M105 is aggressive, (rated at being able to remove #1200 Grit Sanding Marks on fresh paint), and recommended for use by hand, you can easily remove sanding marks by hand if you're willing to
put a little passion behind the pad.
There are a lot of compounds that can be applied by hand to remove sanding marks, but it's the ability of the
super micro abrasive technology, (SMAT), used in M105 that gives it both its' cutting ability and the ability to polish out clear and glossy that makes M105 Ultra Compound a good choice for carefully rubbing out sanding marks right up to an edge or a raised body line
by hand.
Note: The
blue line you see in the pictures below is vinyl tape applied over the top of a body lines on the hood of this 1969 El Camino to make it easier to see and protect them. You can also do this with the edges of a panel.