Pneumatic Grinder & Pad

Does anyone have any recommendations for pneumatic grinders and grinding pads, as well as what grit for taking down lap edges?

some people use the little 90 deg die grinder with a 2" pad

you could use a bigger one but one slip and bye bye

you realy need to regulate the air pressure down, them bad boys want to rev up fast

I think 80 grt is the standard for knocking down laps

i think you should go work in the industry & learn a bit

to many questions ( cheek the archives)

darker than dark


Does anyone have any recommendations for pneumatic grinders and grinding pads, as well as what grit for taking down lap edges?

Forget the pneumatic grinder. Get a good 4.5" grinder with a paddle switch (no thumb switch). Remove the damn safety on the trigger. Get a Bosch mG0500 backing pad and some good quality 5" grinding disks. I only use the Klingspor aluminum zirconia ones, as they last well over a year. Aluminum oxide disks are a joke. Get two 3/4" - 1" pieces of plywood drill a large hole through both of them insert a bolt through both of them with washers on both ends and of course a nut on the back. Put your grinding disks in your new disk press and tighten mercilessly. Keep your disks in the press at all times so they’ll always be flat. Initially, they won’t be perfectly flat until you’ve used them a couple of times each, but the press renders them mostly useable initially and keeps them that way. I use 50, 60 and for ResinX, 36 grit disks. The tool takes some practice to use, but doesn’t run your compressor endlessly, gets everything really flat, and frees you from cutting sandpaper. It is very very important that you only use disks that are very flat, or you’ll chew everything all to hell. Also disks coarser than 50 are not recommended for polyester resin, because it’ll shatter, and even 50 can be borderline on polyester. Epoxy and Resinx are fine with coarser stuff.

Thanks BammBamm.

Chiming in kinda late, but…

Pneumatic grinders, or grinder sanders - well, I have a couple-three of various flavors. My favorite is the 6" pad type that can be either random orbit or straight disc sander. But there’s drawbacks.

First off, they use a Helluva Lot of Air. Even on low speed. Even with the air pressure set down quite a lot.

That can mess with your control some: you’re going along fine and then the airflow goes down as your compressor is trying to catch up and all of a sudden it’s behaving differently. Woops… sorry about that, y’know?

And for doing a fiddly little job like that, let me offer a suggestion: hand tools. A really sharp surform ( with a new blade- a dull one will fuzz the edges on ya) or an equally sharp, clean wood rasp- the file-toothed kind, not the kind with teeth. Or even a very coarse file. Hold it so you are going along the edge, with the tool held at an angle to the edge of the lap and the sharp edges of the tool pretty much at 90 degrees to the edge of your lap.

Kinda like so:

Your control is vastly better, speed is less…but you’re not doing 50 a day anyhow… and you can do it quietly, at your pace and not that of the tool. Better for your head sometimes, hand tools…

hope that’s of use


hey doc,

thanks for the idea.

using a metal file sounds like a good idea.

when I use sanding blocks on the laps ( both free/cut laps)

the sand paper leaves a coloured dust that usually shows

during lamination when the epoxy hit the glass.

any idea how it’s done cleanly without a metal file???

thanks ’


…for pneumatic tools you need a powerfull air comp

if you dont have one, its useless

better cheaper and safety to do a cutlap

If you’re going to cut laps down with a hand file then you should try one of these…

They are “dabomb” when if comes to cutting and leveling bad laps down with the fewest strokes

come back later with a 2’ sanding bar then hand sanding to smooth things out.

probably just as fast as any grinder with a little more control.

an autobody guy’s tool.

One of Uncle D’s greatest hits on Swaylocks.

read about it here:;search_string=file;#235181

well I read all about it and it sounds good.

I found this :

what do you say?

that’s the original:

Right, these fellas have put you in the right direction, I think. And the Vixen files should be a bit more ‘flexible’ when it comes to just exactly how you hold 'em. Those curved teeth are kinda cool.

Now, the cool thing about a file versus sandpaper is that it cuts rather than wears stuff away. So you have shavings…very small shaving, but shavings… you can brush off ( or clean out of the file teeth ) rather than dust which @!%^$ well gets where you don’t want it.

Although - you describe a colored dust that’s deposited that really shows up when you put on subsequent coats. I dunno if that is necessarily the dust from what you’re sanding so much as it may be escaped abrasive from your sanding discs. Leastwise, that has happened to me especially when I was using kinda cheezy discs.

Hope that’s of use


right you are my friend.

I meant to that evil residue left by the sandpaper .

I tried several brands of abrasives, some show and some not, but in the end, they’re all just sandpapers

and I don’t want to take chances anymore.

I tried SIAFAST- CAR ( blue line) is seems like a good one. tried the SIAFAST - LAC series but, if I remember right, they show after lam.

my recent attempt with the SUP, I grinded the lap with the microplane on that stanly yellow surform base, but after I got rid of all the bumps

it just slides over the lap and doesn’t really grind it to the foam’s level. I used a brown 80grit abrasive I cut from a beltsander on a block,

it was good and the lap remained clean and white after lamminating

I wish I could go to one of the 3 big ( and only) shapers we have here in Israel and see how they work from A to Z , but

unfoutunatly israel is a small country , and I think they feel threatened when someone gets into their nish ( is this how this word written?)

and they don’t really want to release any info…

lucky me I have you guys … and you’re 10X better :slight_smile:


Filing/scraping/sanding laps is one of those things where there are many good techniques and

it’s mainly finding which one works best for you. I know several top-notch laminators and they all

have their own pet method, all different.

If you use the air tool, make sure you have a good water trap so you don’t get droplets coming through the sander

and onto your work.

Heee- ‘evil residue’ - I like that. Kind of the story of my life.

But-the bigger the abrasive, the better, I think. That plus the harder the abrasive the better. Aluminum oxide, crocus cloth and the cheapos…especially that white stuff, whatever it is, may its creators burn slowly… they stay ‘sharp’ by breaking off little bits that leave a new, sharp edge rather than staying had and sharp all by themselves. And that’s what I think is getting you.

Now, once opon a time in Panama, I ran into some Bear brand ( a brand name of the US company Norton Abrasives - they also make some very nice sharpening stones) wet/dry paper that was 100 grit. And that stuff really performed. Silicon carbide abrasive, the black stuff, that’s hard enough to deal with metal. And it never broke off, never got dull, I used it for pretty near everything. As there was no power to speak of there, it was all hand sanding anyways, and this stuff would really cut fast.

Now, I haven’t found that 100 grit silicon carbide wet/dry paper here in the States, but I suspect that the coarsest wet/dry paper you can find might do the trick for you.


Could be ‘niche’ - originally a kind of hole or recess in the wall where you’d keep religious relics or statues, has now become a synonym for a particular spot, location or business. As in ‘he’s found his niche in life’ .

Or it could be ‘knish’, the filled dough items of Eastern European origin, generally dough around potato, meat ( lamb is nice) , onion and so forth that is then fried or baked…personally, I like them better fried, like dim sum. But if somebody went and got into my knish, I’d be kinda ticked off. My ex-wife’s aunt used to make really, really good ones too…

And when you think about it,the development of language being the weird thing that it is, could be either one.

And on that note, it’s suppertime

Hope that’s of some help


yeah that’s more than “some help” ! , thanks.

well, some of you might just lough at me , saying I’m a fag or somt’ , but I’m a vegetarian for 19 years now,

having that said…

yes, I meant “niche”… not “knish” :slight_smile:


bon appetit,


My little 90degree air grinder is really handy.I got it at Harbour Freight for around $18.00.I use the rolllock twist on discs 2" green color 60 grit.They don’t leave residue and the little sander doesn’t use much air.You can adjust the speed with the dial.I even soak the discs in acetone to get them clean.Is acetone still legal around here???

dean im assuming you are doing cutlaps yeah

oldschool is the new newschool

I have had two experiences with air sanders…

One was gutless,

The other one was noisy.

However, they are good for aircon.


Same here. It’s what our glass shop uses to grid laps. Can’t beat the price.

Freelaps for me. I did cutlap once but I took the genius step of letting the resin completely dry. Fun! Add that to the fact I’ve never pinlined before either.