New DA sander not working

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PostPosted: Tue Aug 16, 2022 11:03 pm
I tried disc sanding a car for a he first time today and need some advice, it went too slow. I need to get this car- 61 Morris Minor- painted before it gets cold, as I don’t have a spray booth and it’s shelf life is up. I’m using a 6” DynaBrade with 10 cfm continuous. 90 psi. 80 grit, and it’s taking forever. Took 15 minutes I guess, to do about 5” X 9”. Do electric DAs have more power? This seems pretty gutless. The old lacquer paint is really sticking, could it be the paint? It’s the factory paint 60 yeas old. I’ll tempted to give it a light sand and start spraying. I have a blaster but don’t want the mess. I don’t have a spray booth. Any opinion would be very welcome.

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PostPosted: Wed Aug 17, 2022 8:56 am
Lacquer should come off fast with 80 grit.
It may be your paper.
For a more aggressive sander for stripping I use my buffer.
A DA works pretty good but anything that isn't dual action,
something that spins only, is much faster.
Random orbit sanders are even slower than either one.
JC.

(It's not custom painting-it's custom sanding)

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PostPosted: Wed Aug 17, 2022 10:18 am
I use a 125mm grinder with paint stripping discs. No pressure. Fast! Finish with P80 on a DA.
Chris



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PostPosted: Wed Aug 17, 2022 11:11 am
Thanks very much. I did get cheap paper discs so thats one possibility. I’ll get some Nortons. And I’ll get a regular grinder without the DA. A 5 inch diameter instead.
I got the DA because it has a vacuum attachment but right now I just want to get some paint off. If I have to I’ll rig up some kind if plastic booth and blast it off outside. I have 33 CFM when I combine both compressors. And a Clemco 3 cf pot

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PostPosted: Wed Aug 17, 2022 12:20 pm
Using the grinder will get it off quickly but remember not to apply a lot of pressure because you don't want swirl marks in the metal.

When done with the grinder be sure to go over everything with 80 grit on a the DA. This will give a nice even surface for your epoxy primer.
1968 Coronet R/T


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PostPosted: Wed Aug 17, 2022 12:36 pm
it sounds like you have a finish D/A for fine sanding with fine paper, not ideal for heavy sanding. hence the lower power, the Dynabrade is good quality though. DON'T GET A GRINDER the rpms are too fast. look into a Makita 9227C its light weight and variable speed with plenty of power. you can use it to sand and buff makes an excellent buffer. there are several types of abrasives you can use they should be 7" or 8" if you can find them. you can use the black abrasive pads on a backer disc like this Velcro one https://www.hisco.com/Product/00048011094502-31196 or a 3m 7" soft pad with 36 grit to remove paint. i'm experienced but with the Makita i could probably strip 96% of the paint off in about 2 hours, not working hard. some of the old nitro lacquer can be a problem with pugging up the paper, a coarse grit and a slow disc speed helps a lot.
Jay D.
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PostPosted: Wed Aug 17, 2022 2:15 pm
'68 Coronet R/T wrote:Using the grinder will get it off quickly but remember not to apply a lot of pressure because you don't want swirl marks in the metal.

When done with the grinder be sure to go over everything with 80 grit on a the DA. This will give a nice even surface for your epoxy primer.


Thanks, what I was thinking. If by grinder you mean a disc sander with heavy grit paper.



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PostPosted: Wed Aug 17, 2022 2:33 pm
badsix wrote:it sounds like you have a finish D/A for fine sanding with fine paper, not ideal for heavy sanding. hence the lower power, the Dynabrade is good quality though. DON'T GET A GRINDER the rpms are too fast. look into a Makita 9227C its light weight and variable speed with plenty of power. you can use it to sand and buff makes an excellent buffer. there are several types of abrasives you can use they should be 7" or 8" if you can find them. you can use the black abrasive pads on a backer disc like this Velcro one https://www.hisco.com/Product/00048011094502-31196 or a 3m 7" soft pad with 36 grit to remove paint. i'm experienced but with the Makita i could probably strip 96% of the paint off in about 2 hours, not working hard. some of the old nitro lacquer can be a problem with pugging up the paper, a coarse grit and a slow disc speed helps a lot.
Jay D.


Thanks, I was wondering if 50 or 60 would work, so may as well try 36.
The backers disc is for that Makita?

When I said “ grinder”. I meant a disc sander with paper.
I’m very reluctant to get a 7” sander unless it comes with a nice big electric motor and unless I can return it if I don’t like it because that 6” one of mine is way underpowered. Unless it’s supposed to run on 150 psi which I doubt. It sounds like the Makita you recommended is 7 or 8”? I’ll find out, but my tentative plan now is getting the 5” DeWalt at our lumber yard which is not DA and has hook and loop. Use 36 ir 50 grit on that then finish getting the last of the thin paint with the 6” with 100 or 150 grit. But need more info on the Makita first



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PostPosted: Wed Aug 17, 2022 3:04 pm
The Makita 9227 looks great, thanks for that suggestion. Wow, variable speed with electronic speed control, and variety of backers. Hope I can find one close by, there’s a 9237-CX3 here but don’t know the difference yet. Looks the same so far



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PostPosted: Wed Aug 17, 2022 3:30 pm
I don't know what Dewalt you're looking at, i think they have a variable speed one. you should get the variable speed though as it will double as a buffer. my Makita has plenty of power to run 7"and 8" sanding and buffing pads, 7 and 8" discs really speed up the process. your Dynabrade should work good and have good power but as said before it sounds like a finish sander and may not have the power of a regular DA. does the wheel or pad have a lock out on it this is so you can lock out the DA action (no oscillations) this is normally what one would do to remove paint or do heavy sanding.100 psi should be plenty of air pres, it needs to constant as in CFM. do you have the speed control valve open all the way its not only speed but power if you have the speed turned down so is the power. almost all heavy-duty sanders and buffers, except DA's will have 5/8 threaded shafts likewise most all pads will also.
Jay D.
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