Best Grinding Discs?

[LMB]

Anybody found one type of grinding disc to be superior than another for big material removal jobs? I'm removing gel-coat from the deck of a work boat. Doesn't have to be pretty, just need to get down to the underlying mat quickly.

[Dean Smith]

60 or 80 grit on an angle grinder 7 inch with backing pad, or try Rondella which is esp for aluminium but methinks would work

[LMB]

Started with 7" 24 grit on grinder. Gel-coat is thick and it's a little slow. I sometimes use the flap style discs for smaller areas on a 4.5" grinder which generally work pretty good but I didn't have any larger ones in a courser grit. I figure some materials or brands might last longer as well. All are fairly pricy so I want to stock up on the right thing.

[CatBuilder]

I use 35 or 40 grit on a 7" polisher/buffer. I just use the crap at Home Depot or Lowes. They last forever and tear right through fiberglass like it's butter.

They really don't lose their bite very quickly at all.

[iceboater]

I use 5" inch diamond segment grinding disc. It lasts forever, but you have to be careful to keep the disc moving or it will grind in very fast.

[Landlubber]

"I use 35 or 40 grit on a 7" polisher/buffer."...yep, works for me too...soft backed pad, varieble speed AEG electronic unit and it rips it off and basically never blocks up, you can go coarser too if you like.

[CatBuilder]

"I use 35 or 40 grit on a 7" polisher/buffer."...yep, works for me too...soft backed pad, varieble speed AEG electronic unit and it rips it off and basically never blocks up, you can go coarser too if you like.

Same setup here. Variable speed is the key. I use a rubber back pad, which is less forgiving, but I got very artistic with it after doing hundreds of scarf joints with this tool for my failed wood/epoxy hull. :D

I have a confession to make: I really enjoy this tool. It is my favorite in the entire shop. I even use it to cut peel ply off fiberglass edges! ha ha ha

Only complaint? I filled my entire shop (and several meters outside the shop) with fiberglass dust today taking the overhanging glass off my hull that is nearing time to pull from the mold. Now, it's a very itchy place.:eek:

[PAR]

A polish/buffer type of grinder with a 7", 9", 10" or the rare 12" pad is the fast material removal tool. If you're serious about material removal, then it's all about the grit and speed. 16 grit on my 10" will eat through most anything in very short order. The 10" is a beast and not easily used in confined spaces, plus it has so much torque, you have to use both hands. 24 or 36 grit on the 7" are the usual choices. They cut aggressively, but with a lot more control on the 7". 40 and up grit is for sissies. Do yourself a big favor and learn how to fabricate a hood for this tool and plug the shop vac hose into it.

[ondarvr]

And step up to an actual grinder, 5000 RPM and heavy, it will have a great deal more power than a buffer/sander.

Check your local abrasive supplier if you want better discs, they will a few grades to choose from.

[Landlubber]

"it will have a great deal more power than a buffer/sander."....wrong mate, the AEG is UNSTOPABLE cos it is electronically controlled, it runs same speed no matter how hard you can shove it. Mine is about 10 years old now, has a little light that is supposed to show overload, never seen it on mate. It is a supurb tool.

[War Whoop]

Peeling gelcoat?? I use a makita planer, the carbide knives are cheap and reversible,Cleanup and tight areas with a 4" grinder.

[Frosty]

Do you want to play with it or get the job done,--- 16 grit on a 10inch.

If your ripping anti fouling off as well 60 70 is usless.

Value for money ---Bosch.

[michael pierzga]

Anybody found one type of grinding disc to be superior than another for big material removal jobs? I'm removing gel-coat from the deck of a work boat. Doesn't have to be pretty, just need to get down to the underlying mat quickly.


Power planer does a good job. If its a big job with resonably flat surfaces..

Also consider renting a concrete planner or a PPT.

http://www.novatekco.com/html/ppt.html

http://www.makita.com/en-us/Modules/Tools/ToolDetails.aspx?ID=316444

[Wynand N]

use a buffer/sander type grinder with 60 /80# Abramat discs. Ones with velcro at the back. If clogged up, take it off, knock out the dirt until see through again and go again.

[CDK]

Iceboater in post #5 offers the best solution. You can do the whole boat without changing discs and you don't get tired because there is hardly any pressure required. All you need is someone to wipe the dust away and a long shower afterwards.

[waikikin]

ZEC discs go well http://www.google.com.au/imgres?imgurl=http://www.sculpt.com/pictures/abrasives/Zec/gczec1.jpg&imgrefurl=http://www.sculpt.com/catalog_98/abrasives/zec.htm&usg=__uiIKbiorHJ8NJASUwFY_w6SraF0=&h=245&w=270&sz=25&hl=en&start=0&zoom=1&tbnid=B08o1jfw38PGqM:&tbnh=172&tbnw=190&ei=itiFTa3ONYnuvQPP9ejeCA&prev=/images%3Fq%3Dzec%2Bdisc%2Busa%26hl%3Den%26client%3Dfirefox-a%26hs%3DHpG%26sa%3DX%26rls%3Dorg.mozilla:en-US:official%26biw%3D1280%26bih%3D650%26tbs%3Disch:1%26prmd%3Divns&itbs=1&iact=hc&vpx=630&vpy=95&dur=2779&hovh=196&hovw=216&tx=160&ty=114&oei=TNiFTfjyOYffcfPDlZsD&page=1&ndsp=18&ved=1t:429,r:3,s:0

regards from jeff

[Frosty]

Have I got this right --your ripping off gel coat and antiflouling for osmosis treatment with 60 grit ? Come on guys --60 70 grit, I do my toes nails with that.

What do you get 10 seconds a pad, no wait 5 seconds.

What do you think they make 16 grit for?

[CatBuilder]

A real man uses two grit! You're all a bunch of sissies! ;)

[LMB]

I appreciate the input and can relate to most responses. For moderate material removal and prep a disc sander with 36 grit on a soft back up pad has worked well. For rough stuff that might tear up a pad I usually use the 24 grit flap discs on a 4.5" grinder. Neither of those are cutting it for this job. I tried the somewhat standard 7" 24 grit on a 5000 rpm grinder and was not overly impressed either. The 16 grit was not readily available but I may special order. I'd also like to try the 7" flap wheel in a 16 or 24 grit to see how it compares. Those Zec wheels look real interesting too. Similar to the flap wheels which have worked well for me.

I'm also going to try a dust collection shroud. Product called the dust muzzle is cheap enough and looks like it might work. I'm open to suggestions here. Not my first rodeo but I'm always looking a better way.

[Frosty]

2 grit might work, but if you really want to get on with the job tie 2 house bricks on some 6mm steel wire on a good 110 V drill.

The dust is a problem,-- If I had air drills I would use 16 grit and have the wife stand by with a hose pipe.

16 grit wont clog,--well like 60 would, a 16 will last a long time.

I recently had a cock up with a job joining a dinghy to make it smaller . The resin did not go fully off,-- I guess the hardener was old or something. I didnt have time to mess about. The 16 grit ripped off a 2 meter by 4 inch strip of soft resin and glass in minutes. I used but 1 16 disc and it is still usable. On the floor was a bunches of cotton wool like mush.

[ondarvr]

I had a crew of 6 guys that would grind for 8 to 10 hours a day, we used 16, 24 and 36 grit on big grinders (5000 RPM), finer grit than that and we would drop down to a lower RPM. We used several different brands of grinders, each had a purpose.

At the time the diamond discs weren't as easy to get and cost far more than they do now. If you want the surface to be smooth it may be difficult for less experienced person to do it with a stiff diamond wheel.

A 4.5" is OK for small stuff, but won't cut it for high speed removal of material.

There is huge difference between a polisher/buffer and a high speed grinder, even if its an electronically speed controlled model. We burned of several models of these when guys would use them in place of the big grinders, they would use them because they are lighter and easier to hold in difficult positions.

Flapper discs are a waist of time because you are always grinding with worn out grit, rookies like them because they are easier to control and remove material slower. If the backing wore away quicker it would expose fresh grit faster and speed things up.

How big of an area are you working on?

[waikikin]

Those Zec wheels look real interesting too. Similar to the flap wheels which have worked well for me.

I'm also going to try a dust collection shroud. Product called the dust muzzle is cheap enough and looks like it might work. I'm open to suggestions here. Not my first rodeo but I'm always looking a better way.

Believe me, the ZEC discs will leave a flap disc behind in a cloud of dust, last like 10-20 times as long as an ordinary disc & cut well until worn right out. Regards from Jeff.

[CatBuilder]

Lmb: thanks for the tip about the dust hood. Will get one of those before my next grinding job.

[Steve W]

Agree, those zec discs are the ****, 16 or 24 grit work best,i actually prefer the 24grit. You can make your own dust shroud out of fiberglass which is what we did 20yrs ago when you couldnt buy them,we screw on one of those bristle type door sweeps to the bottom, i buy them at home depot and cut to length,when we first made the shroud we actually used a seal on the bottom edge and drilled a series of holes in the shroud that we could tape over to adjust the vacuum so that with it on a milwaukee grinder we could grind a hull bottom with the vacuum supporting the weight of the tool. We have just recently bought some metabo shrouds for 4 1/2" and 9" grinders which are made of urethane so are flexible, we bought one of those clear lexan ones too but decided upon looking at it that its too wimpy for shop use,probably fine for home handyman use.
Steve.

[michael pierzga]

Lmb: thanks for the tip about the dust hood. Will get one of those before my next grinding job.

get a Dustie' then "Bust your ass for fiberglass "

http://www.dustlesstechnologies.com/dustie.htm

[LMB]

All great input. I ordered a 16 grit Zec this morning. Based on responses I may go ahead and order a few more. ondarvr, you definitely get where I'm coming from. When grinding I routinely change tools, discs, grits and RPMs to fit the task. The current job is really not so big - but it has caused me to look for a more efficient system. Just a 17 foot skiff with maybe 100 square feet of sole to be stipped down to the mat. Sounds easy enough but there is probably 1/16" of gel-coat on this thing ( part of the problem). After about 3 hours of grinding we've stipped maybe 15 square feet. That's using a 7" 24 grit on a 5000RPM grinder. I'm a patient guy - but not that paitent.

Also, I've been post-poning dust collection for a while but its at the fore front again. Between the health risks, the mess and lost time cleaning up I've got to employ a better system. I'm a small tight budget operation but I think I'm onto some cost effective solutions. Thanks michael for the link to the dustie. Their line of products is the kind of stuff I'm looking. Call me a sissy, but I'm looking the cleanest, safest, most efficient tools and processes, that I can afford to use.

[Frosty]

Im interested in the dustbag. I have a rotten little job on the bathroom window.

Do you get in the bag or do you work outside it--if you do how do you see or work the grinder.

I was thinking of taping a black bin liner round it but got no further.

[mark775]

Yes, Zeks take off some material but listen to Par on this one. Course grit, large disc, more control (larger area in contact at one time) with larger diameter for more even finish. I am happy leaning on a nine inch Milwaukee. You're gonna end up with a comparatively choppy surface with the Zek.

[waikikin]

All great input. I ordered a 16 grit Zec this morning. Based on responses I may go ahead and order a few more. ondarvr, you definitely get where I'm coming from. When grinding I routinely change tools, discs, grits and RPMs to fit the task. The current job is really not so big - but it has caused me to look for a more efficient system. Just a 17 foot skiff with maybe 100 square feet of sole to be stipped down to the mat. Sounds easy enough but there is probably 1/16" of gel-coat on this thing ( part of the problem). After about 3 hours of grinding we've stipped maybe 15 square feet. That's using a 7" 24 grit on a 5000RPM grinder. I'm a patient guy - but not that paitent.

Also, I've been post-poning dust collection for a while but its at the fore front again. Between the health risks, the mess and lost time cleaning up I've got to employ a better system. I'm a small tight budget operation but I think I'm onto some cost effective solutions. Thanks michael for the link to the dustie. Their line of products is the kind of stuff I'm looking. Call me a sissy, but I'm looking the cleanest, safest, most efficient tools and processes, that I can afford to use.

Sounds like you've got it sorted, typically when I've ground out a cockpit sole say for a 40' game boat say 10' x 10' / 9-10m2 prepping for an overlay decking, including tenting & clean up would be about 4 hours.
As Mark alludes to using a large "footprint" does the job most evenly on the job, I see plenty of people driving sanders around on the edge of the disc only & "chopping" up the surface, try & tell em, some listen, some.........
With your 7" sander/polisher an 8" soft pad set up for velcro discs is a handy addition too.
Regards from Jeff.

[tunnels]

Have found over the years the really coarse disc's are not nessasrily the quickest or best . If the disc is just glogging up Take them off and drop them in acetone ! the grap just falls off revealling an almost unused disc . :D
let them dry before you refit to the grinder . The saving on discs can off set the price a litre of acetone . :P

[Landlubber]

...or slow down the speed.....they should only be doing well under 2000 for heavy grinding, I run mine at 1400 with 36 grit.

[Frosty]

Landlubber --what the hell is your avatar, I cant make out what it is , is it a woolly mammoth with a hat on near your bedroom window?

I don't know what the hell that is.

4 inch 16 grit 4000 RPM the skill is in your hand not the machine.

16 grit is like self cleaning, like a mud tyre, it self cleans.

[Landlubber]

...Frosty, have a look here, the "real" Landlubber...poor bugger has no "real" boat, this is what happens when you only have a dinghy, no more ocean boats to play with....don't let this happen to you.
http://www.tonmo.com/articles/olsen.php

[Frosty]

I don't know what you are smoking but I would give it up if I were you.

Im a sensative boy, I will be having night mares now after looking at those distorted figures.

Change your avatar to a crankshaft or something nice, as long as its not a cute kitten or i'lle have to smash my lap top in.

[LMB]

Just thought I should follow-up and say that the Zec is the deal. About twice as fast as regular 16 grit disc and no problems chopping up the surface - just hold it flat. One wheel did the whole job too so no lost time changing discs. I did follow with the 36 grit soft pad on buffer to finesse it a little. Not the tool for every grinding application but if you need aggressive material removal this is it. Thanks to all.

[Roy Gorman]

Iceboater in post #5 offers the best solution. You can do the whole boat without changing discs and you don't get tired because there is hardly any pressure required. All you need is someone to wipe the dust away and a long shower afterwards.
Dear CDK: Where do you buy the diamond segment grinding disc? Thanks, Roy

[CDK]

Roy, this is the kind of disc designed for cutting relatively soft but abrasive materials like limestone or marble. I bought mine in a department store a few years ago. It came as a set of 3 different discs, the others for ceramic tiles and granite.

You should have no problem buying such discs on Ebay.