Official Luthiers Forum!

Greetings,
I am thinking of buying the Porter Cable 390 low profile Sander previously mentioned in a different thread. I would like to know if it is best to get the hook and loop style or the peel and stick kind. And furthermore, I will now ask possibly the dumbest question ever...does it work like an air-powered sander? I have a dynabrade, and I love how it works, but my wee compressor weeps at the sight of it, and ends up drooling hot water all over my guitars as I'm finish sanding. Will the electric one sand as good as the air one?
Thanks

Do not think that you can wet sand with the PC!!!
That said, the PC is a good sander for sanding wood, smoother than my Makita although I think the Makita is seeing its last days. I use H & L on it and stick on my Makita. The only problem I have with it is that I can only hold it from the top and I can hold the Makita from top or side.
Eh, maybe I misread your post...

Hi-
Both types have their advantages.
I've used/own both PSA (stick-on) and 'hook-and-loop' sanders. I've had a couple of the 'velcro' style eventually 'lose their grip' and require a new pad or diy repair of some sort. Unless it's an expensive sander, it makes more sense to throw it out at that point. My PSA sander doesn't have holes in the pad- not sure if this is the rule or not- so some may find this a problem (dust control is more difficult). I actually prefer it since I do 90% of my sanding semi-outdoors.. However, PSA sanders are not really good for small jobs where you are moving up in grits- though you can 'save' the paper for next time if you are careful. Keeping double sets of sanding discs on hand is expensive.

So you would probably be happy with either choice.

A water trap (or two) in your air line might make the Dynabrade usable for you- from what I've heard, they're superior to most electric sanders. Make sure you keep your air tank drained of water- it sounds like you have pretty high humidity.

After saying all that, I don't use the electric sander that much for guitar building. A hand sanding block seems to give a flatter surface, and is almost as fast, and safer from mistakes (for me).

Cheers
John

I've got half a dozen random orbital sanders in my shop. 2-3 Porter Cables will burn up before 1 Dewalt will.

I don't like using air sanders even though I have a faily large compressor; the compressor runs and runs and I don't like the continual noise.

Electric R.O.s do just as good a job as pneumatics although they are not quite as aggressive.

Get hook and loop and replace the disc when it wears out. Guitar building requires that various grits will be needed long before the disc is shot. With PSA discs, my experience has been that once it's removed there's usually not enough adhesive to hold it on again the second time.

I would recommend the hook and loop also. My Makita got to where the sandpaper would not hold on very well and a replacement disk was easy to get and quite reasonable.

_________________
Steve Smith
"Music is what feelings sound like"

Get the Hook and Loop. I think are much easier to use.

I have a Dewalt variable speed Orbital Sander. I like if very much. I also have a couple of the Harbor Freight round orbital sanders. They are one speed only. I use them a lot too. And at $19.00 on sale, they can be thrown away when they wear out. They are also 8 hole hook and loop. like my Dewalt.

Ken

Thanks folks,
Does anyone use a hook and loop for final sanding the finish prior to buffing? I just wonder if it is too soft to imparts a perfectly flat surface...

I block sand by hand to level the finish. I've worn out several sanders on furniture but I don't have that much experience with guitar finishing.

_________________
Steve Smith
"Music is what feelings sound like"

I have that 390 and it might be one of my threads you are refering to (then again, maybe not). Yet, its a very good sander. I would still have a mouse sander handy. Lots of reasons for that. Oh yeah, H&L

Mike

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I have used micromesh hook and loop pads for wet finial finish sanding using my pneumatic RO and it did ok but I real prefer wet sanding and by hand.

Please due not attempt to wet sand with an electric RO! The electrical shock hazard is significant and we would like to keep you around a bit longer

What i do not like about electric orbitals on finishes is if the paper loads up they can leave the worlds worst swirl marks.

What I was hoping to avoid was hand sanding the finish at all. I've been able to flat sand it (dry) with 15mic on a PSA airsander, but that still leaves some fairly deep swirls to account for. So I tried 9mic, but it balled up and seemed to leave even deeper scratches. I'm not lazy, but I work a lot, 8hrs of fretting, sanding, clamping, unclamping, etc. and then off home to do it all again for another five or six hours. The wear and tear adds up, and buffing is one of the worst tasks, I always wake up the next day with the claw. So I'm hoping to find a way to machine sand to some grit or micron level that makes buffing a lot easier. Would you be willing to share precisely what you do?
Thanks

You might PM James Orr (I hope I'm not wrong about that) and ask him. If I remember correctly (highly unlikely) he was using a Festool sander with the Brilliant and Platin papers successfully for finish leveling prior to buffing.

A Festool is an amazing ROS.

_________________
Eagles may soar, but weasels don't get sucked into jet engines.

I'm not a finishing expert, but if you are getting deep swirls (dry) sanding with 15 micron (~600grit)/9 micron (~1000grit) on the PSA, something is wrong. It sounds like you have either finish balling up (as Michael alluded to) or grit contamination from coarser paper.
One possibility is that the finish is not (yet) hard enough to sand without balling up.

Also, I don't understand why you don't wet-sand- especially if you are using an air sander. With 320 and above grits I always wet sand, and wipe off the surface often to check on the progress. You should be getting a nice 'matte' finish as you move from grit to grit.

Finishing is always tricky for me, and my hands are acting up more lately, so I 'feel your pain'.

Cheers
John

Thanks for the replies all.
The finish is definitely dry, it's UV cure poly. I've never tried wetsanding with the air sander, I always thought that it's advantage was that you didn't have to. It never occured to me that you could.

I recently replaced my ROS (the 10 year old DeWalt finally died). I checked fine woodworking reviews and they tested current offerings about 1 year ago. One of the tests was the scratch pattern that each sander left on a piece of plexiglas. The Bosch ROS left the finest,, least scratchy pattern. I bought one on that basis. Wow!..best ever. Use hook and loop paper as well as Abralon pads (up to 4000) prior to buffing. It has made an incredible difference in my finishing time. Highly recommended.

The advantage of wet sanding is due to the hydroplaning your scratches are shallower, the paper loads less, much of the solids removed are washed away and the surface is cooled by the water.

Pneumatic and electric powered sanders advantage is purely mechanical power. One disadvantage of power sanders is heat build up brought on by this excessive mecanical power that can cause the removed solids to gum up on paper leading to bad swirls on the surface.

Advantage of any random orbital sander is the random orbital rotation of the scratch pattern. My personal opinion this is no real advantage when rubbing out a finish. Micromesh orbital pad and other micro-finishing pads make it possible to have a near swirl free surface but the possible chance of swirls caused by load up of solids on the pad is still there when using power sanders.

Tools from the same company seem to change over the years- glad your new Bosch is working well.

I've had two Bosch ROS, and I wouldn't recommend them over the competition. My first Bosch (years ago) had the hook pad fail after a year or two and the replacement was expensive (in my book, anyhow- $35 for a pad on a $120 sander..). The second Bosch was one I bought (about 5 yrs ago) because it had what I thought was a good dust hose/vac adapter. It's worked well but has always had a lot of vibration, and is heavier than I like as well. I've got 2-3 cheap, light, low-vibration yellow deWalts around the shop that get most of the use on utility jobs. If they'd all co-operate and break, I'd probably go for a Festool, which has excellent reviews but is in a different price category. (Also doesn't use standard discs?)

Cheers
John