filing old bondo

[supernaut]

i just got in from filing 4 year old bondo on the right front fender of my '75 k5. the flat and round file 10" blades are both worn down after about 20 minutes each. now they kind of shine the bondo instead of grinding it off in long curled shavings. the file blades are pretty low end, "bondo" brand i got at the local shuck's auto supply.

is my problem the bondo being old and hard or the blades being cheap? maybe there are some hardened steel type file blades i should seek out at a body shop supply joint. maybe i should get some sanding blocks and go with 120 grit or so instead? i fear that i will just clog up the sand paper with bondo after only a few minutes tho...

pointers anyone?

 

[ryoken]

i assume your talking about "cheesegraters".. if so, they are only meant for fresh bondo when it has first flashed off..

hit it with 36 grit on a block, then 80...

 

[supernaut]

yeah ryoken. "cheesegraters". thanks for the information, i'll try that out.

 

[JK5]

LOL....I thought I was the only one that still used those....

 

[velocitiii]

nice fresh strip of 36 grit is the way to go

 

[diesel4me]

Yup--Cheesegraters!

We sold lots of those!--"Stanley" tools calls them a "Surefom" file...but as stated,they only work good on freshly applied bondo--one of the hardest things to get off a vehicle is old "tiger hair" or other long strand fiberglass filler(not ordinary "bondo")---about the only way to get it off quickly is to use a 16 grit grinding disc on a 7 or 9 " grinder,and a mask!(or use a propane torch!)--its like concrete once its been on a vehicle for several months...I see a lot of that stuff here--most GM trucks are practically MADE of it around here!...the lower 12" of most of them here are no longer made of steel...

 

[supernaut]

thx again for your replys guys! i'll pick up some sandpaper today or tomorrow and prime up my arm joints with elbow grease.

 

[ryoken]

there are other options if you have access to air, electric... you can rough it into shape with a DA or palm sander first letting the machine do the work. then finish it off with a block or longboard.. i do as much bondo work as i can get to with a cheesegrater then an air longboard..

cutting on angled crosshatchs with the sanding block will give you best results usually. have fun

 

[supernaut]

i went commando on the old bondo with 36 grit and a rubber-like sanding block. it worked beautifully! cut right through the old bondo and in less than an hour i was shaping rather than just removing excess filler. i tried the crosshatch motion, but the area i was working in pretty much limited my options. it's in the front of the right front fender where the line takes a 90 degree turn.

towards the end of sanding i found some high spots of metal coming through. i'm thinking i'll have to beat these back in a bit and put filler over them. i'm pretty sure i caused them before i put the bondo on way back when. i was trying to reshape the metal back into place a little bit with a prybar from the rear side. I may have been a bit over zealous in spots. ah well, it should give me an opportunity to drill a few holes in those spots. i've read that the holes are desireable for the bondo to adhere to.

in the meantime i'm going to sand down and bondo/primer over a few spots that are rusty. i would post pics but, you know...i'm not a MEMBER. i should put 'em on the web somewhere and get a link to them going here.

any suggestions or tips would be welcome!

 

[NJBLZ]

If I'm removing a lot of old bondo I'll go right to the grinder, then re-bondo it.