I need help with Block sanding

[fireman_1983]

It seem that i am doing something wrong. I am still learning bodywork i keep sanding my body filler off and the wave or dent comes back. am i not applying my filler right? what am i doing wrong? I have the same problem with primer.

[danbob67]

Hard to answer question without seeing exactly what your doing. first off you need to get the area as straight as you can to begin with either hammer and dolly stud gun, picks or whatever your methods may be. after you get it as staight as you can before filler. ruff up the area you are going to apply filler, wipe it as even as you can, start with a coarser grit to begin with, end with 180 before you apply primer. always keep your block flat and try to do a X pattern while blocking.

[Mike Holleman]

Are you working too small of an area? If you are concentrating on a single small dent instead of say two or three feet of panel at a time you will get the result of just putting it on and sanding it off. Try a bigger section of panel and see if the dent still comes back.
Mike Holleman

[Norwoodx55]

Maybe a bigger/longer sanding block would help out also.

[stewy]

Tap the shiney high spots with a body hammer if they keep coming back. Put body filler a couple inches past the dents. Block sand it flat with 80, then with 180, leave enough plastic filler on for the 180/120 grit step, otherwise you will sand too much off trying to get rid of the 80 grit scratches.

[Z- man]

Here is how I do it. Don't think of it like your "taking out a dent" think of it as making the whole panel straight. Kinda hard to explain but use the longest sanding block you can use and this will yield the best results, work an area roughly2-3 times the size of the dent. A couple of years back I blocked out a 55 Nomad and I used a 24 inch block. we primed and blocked it out 3 times! It was a LOT of sanding but the car was ARROW straight when done. Stick with it, body work is one of those things you can't learn from reading a book you have to get out there and do it, but it will come to you and the car will thank you. good luck!

[CSI:QUINCY]

one of the hardest thinks to master. when to switch from 80 to 120 then 180. very hard to do. yes the longer the block the better but you can't always use a long block. take your time the body work makes a paint job. lack of time spent sanding and blocking. no mather if the best painter in the area sprays the surface. the body work will shine thought. so don't rush it take your time and if you think you got it you might just prime and sand one more time to be sure.

p.s. guide coat is a trick that can help but take your time is the best trick.

[dhutton]

I used the 3M dry guide coat when block sanding my car. It's easy to apply and it helps show the high and low spots. The other trick I used is to alternate coats of buff and gray high build primer. It makes it easy to see when you have gone too far. It costs a little more to buy two gallons but when you think of what it would cost to pay someone to do the work it's worth it.

Don

[OneQuickCoupe]

I used the 3M dry guide coat when block sanding my car. It's easy to apply and it helps show the high and low spots. The other trick I used is to alternate coats of buff and gray high build primer. It makes it easy to see when you have gone too far. It costs a little more to buy two gallons but when you think of what it would cost to pay someone to do the work it's worth it.

Don

Good advice Don. I haven't tried the dry guide yet. In the past I applied light gray surfacer then sprayed a light dust coat of black spray paint. Just a dusting worked very well. Alternating the primer colors is a great idea. Just want to make sure the finished primer/sealer is all the same color.

A lot of the custom guys are putting on a skim coat of filler over the complete panel to include over the door, hood and trunk seams. They block the filler using an extremely long and wide board. They come back after the block work to open up the seams. Makes for a super straight job.

Mr. Fireman,

One of the things I had to learn when I first started out doing body work was to not press hard on the panel i was sanding. Let the sand paper do the work. Flexing the panel will cause all kinds of problems when trying to get things arrow straight. A light touch equals arrow straight.

D.J.