# porter cable 7800



## stratford (Sep 14, 2016)

Hey all, Just signed up for the forum.
Just finished preping 4000 sq ft of board. Decided to pull the trigger and get a sander.
The unit arrived new this morning. tried it for 5 minutes and burned down to the paper real fast, and lots of swirls. Didn't use much pressure. Not impressed.
So looking at it closer, I figure that one of the problems is that the head is very stiff and doesn't pivot easily when I put it against the wall, so one side of the disk hits first. Second problem is the "standard disk" is pretty course (maybe 80 grit?). Have that problem being resolved tomorrow with a Full circle Power pad and 150 grit disks. Third problem, not sure if anyone has seen this. It looks like one side of the springs that hold the outside shroud (with the bristles) are weaker than the other side. Standing up the unit, the left side appears to have some wobble (weak springs?), and the right side is very firm. So when you put this on the wall (with the unit on), the left side weak springs let the sanding disk touch the wall right away. So before I even got ready to start moving, the machine had swirled up a bunch of top coat, and buffed up the paper. The was like no resistance to make contact with the wall on one sidel. Make sense?
Anyway, not sure if this is normal, but any input would be great. I'll be trying again tomorrow.

Cheers.


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## VANMAN (Jan 14, 2011)

stratford said:


> Hey all, Just signed up for the forum.
> Just finished preping 4000 sq ft of board. Decided to pull the trigger and get a sander.
> The unit arrived new this morning. tried it for 5 minutes and burned down to the paper real fast, and lots of swirls. Didn't use much pressure. Not impressed.
> So looking at it closer, I figure that one of the problems is that the head is very stiff and doesn't pivot easily when I put it against the wall, so one side of the disk hits first. Second problem is the "standard disk" is pretty course (maybe 80 grit?). Have that problem being resolved tomorrow with a Full circle Power pad and 150 grit disks. Third problem, not sure if anyone has seen this. It looks like one side of the springs that hold the outside shroud (with the bristles) are weaker than the other side. Standing up the unit, the left side appears to have some wobble (weak springs?), and the right side is very firm. So when you put this on the wall (with the unit on), the left side weak springs let the sanding disk touch the wall right away. So before I even got ready to start moving, the machine had swirled up a bunch of top coat, and buffed up the paper. The was like no resistance to make contact with the wall on one sidel. Make sense?
> ...


The heads can b stiff on those!
80 grit is way to much! Depends on mud u r using but I use 320 Abranet disks which leave no swirl marks! Always start on the board and keep it moving ! Also try on a slower setting till u get into the swing of things!:thumbsup:


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## gazman (Apr 29, 2011)

Been using the PC for years, no issues like you described. I use a norton backer.

https://www.amazon.com/Norton-9-Inch-Back-Up-Porter-Drywall/dp/B000PDOCOW

Depending on what mud I use, pads are either 220 or 180. A tight headvcan be caused by the drive cable being too long. Take it out and cut 1/4 inch off it. If it helps and it is still a bit firm take a little more off. There is a fair bit of depth to the bit where the cable geos in so there is a bit of wiggle room.


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## thefinisher (Sep 2, 2011)

Pretty much what others said... Also really depends on what type of mud you use. You may have to just sand your screws first to break it in and get a feel for it. If leaving swirl marks then either the grit is too much or the pads aren't centered correctly making it wobble. Like they said, never start sanding directly on the mud! Place the head on the paper first and then move it onto the mud. If you are just learning I suggest going with much finer paper than you think you need until it breaks in and you get a feel for it.


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## Mr.Brightstar (Dec 2, 2011)

Up grading the pad will solve most the swirls problem. I use the joist 220 grit, smooth as glass. Sometimes mine has a wobble to it and sometimes it don't. Once you get the hang of it you'll never go back to the dark days of drywall.


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## stratford (Sep 14, 2016)

Thanks to all of you. I have a Full Circle power pad coming tomorrow, and a bunch of 150, 220 and 320 disks. We'll try a second test!


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## stratford (Sep 14, 2016)

So, here is the end of the story. I returned the unit for a full refund. Before doing this, I spoke with Porter Cable and a repair depot, who all told me that the "something didn't sound right", and that I should return the unit for exchange. So after trying a new pad, new disks (220 and 320) I still wasn't convinced and went back and finished the job (4000 sq ft of board) by hand with my 360 radius pole and flex edge sander. Because I had used the flushers and flat boxes for all mudding, it turns out there really wasn't much to sand anyway, just a touch up and the 3-way corners. Didn't take me long. I gave everything a quick vacuum and have already primed and painted the ceiling.
I took the unit back to the vendor and they showed me 2 demo models that had the same stiff head. Couldn't talk me into it.
So moral of the story (for me, at least) is that I will stick with hand sanding. The only thing I will try to find is some vacuum attachment for the radius 360. I certainly liked the idea of the vacuum to keep the dust down. 
Thanks again for everyone's contribution.


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## cazna (Mar 28, 2010)

Don't give up. That's a cheap sander and goes great.


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## gazman (Apr 29, 2011)

The PC works great for me, it is worth persevering with.

https://www.youtube.com/watch?v=gf20qumozuA


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## thefinisher (Sep 2, 2011)

Many have probably wanted to throw away our power Sanders after the first go as it's a learning experience. I would keep it and only do the screws and maybe edges of angles for a while. After a bit the head will loosen up considerably. Watch some vids and learn how to approach the mud correctly. Not a tool that you can just buy and expect perfection from it.


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