has anyone tried blocking with a pneumatic straightline or jitterbug sander? is the working action or design of these air sanders too extreme for blocking? thanks. :confused:

I have never tried it but I would think that it would be too aggressive for the fine finish you are looking for when blocking. I was taught to use and have always just used a hand held long board for big areas and a smaller block for the smaller areas. It does not take as much time to do each blocking coat as you would think, but the end result is worth all the time you take.

The only time I use a straightline air sander is to ROUGH body filler, its too aggressive for final shaping filler and sanding primer.

Sorry nothing beats the good ole fashioned hand sanders.

do it by hand, it's the only way you'll have enough control on the operation to make the panels straight.

thanks guys..i'll take your advice. graemlins/thumbsup.gif

I think it would be too aggresive as well. Keep this in mind when blocking too; Too much pressure will make the 'block' follow the imperfections.

keep a 1/2 way light hand and mold the surface into straight and flat piece.
Remove the high spots and leave the low spots filled.
Just keeping these two things in mind while blocking has helped me.

Also, Guide coating the primer before blocking is essential in my opinion. I have an experienced hand for feeling out imperfections but when they get as minute as say .010-.020 of an inch your hand will not feel them. Using a guide coat and your eyes will reveal everything, also work the complete panel with as long of a block possible considering the panels contour, do not work the panel one spot at a time. I have one block that is 36inches long!-which comes in handy on long flat panels. When all the blocking is done and the primer is final sanded to 400 or 600grit I usually then take a grey scotchbrite tripled in thickness and rub the car down to mellow out any imperfections left after the blocking process-the paint will flow like glass. Also, new blocks are usually very sharp along the edges-use some 80 of 180 to round off these sharp edges before you use them. I've also seen many new blocks that were not straight so I usually tune them up with some 80 grit stuck on a flat surface before putting them into use. Good luck! Have patience! You'll know when it's right graemlins/beers.gif

baddbob71,thanks for the great advice! graemlins/hurray.gif

thanks to you,also,Jimmy P! :D

dd

Bowtie, one more thing to remember is use a block that matches the shape of the panel. Say you are sanding a panel that has a concave surface(curves inward) you DONT want to use a flat board. You need a block with some curve to it that somewhat matches the curve of the panel. If you dont and use that flat board it will dig into the panel or not FLOW with the panel.

Some of my own personal curved blocks are door mouldings!! Chrysler products have GREAT door moulding for this purpose, should be able to rob some off cars at the local grocery store :D Mine are from a 99 Concorde and 96 LHS, both have nice curved surfaces each having a different profile.

Can also use stuff like PVC pipe or even a heater hose :eek: Use what it takes to get the job done.
Check out this topic on block sanders http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=3;t=008196#000002

Another thing to check out is 3M's dry guide coat system, kinda pricey at 25 bucks but its a pretty slick unit...Eric