are all sanding discs equal?

General Discussion
1

stoopid question i know - but here goes anyway…

Up till now iv’e been using grits 120 - 180 to sand down my hotcoats - the thing is that i have been using sanding disks labelled as “To Be Used on Metal” - now, before you laugh at me - is a 120 grit disc of this type the same as a 120 grit made for say wood not metal? to my thinking 120 is 120 no matter what it is made for - but maybe im wrong - am i getting more sand throughs for this very reason?

should i be using a specific type - the one is use for the lower grits is a type of resin paper.

sorry for the stooopid question

ado

2

120 grit should be 120 grit no matter the brand.

Others can chime in on “made for metal” but I would venture it has to do with the adhesive used to stick the grit to the backing.

Starting hotcoat sanding with 120 is kinda fine, and going to 180 is unnecessary. I use 60 grit on a soft pad, then hand work the rails with the pad. If I will pinstripe, I’ll go directly to 220 wet sanding by hand. It really smooths off the roughness left by the 60 grit. But this is just me, and I’ve been thinking to substitute 80 in place of the 60. It’s just that I bought a big stack of 60 so I’m bound to use it. I don’t have any problems with it; like everything it can work well if you’re used to it and have a light touch. Careful on the rails and nose area though, or it can cut through pronto.

Some brands are more durable than others. I used Norton Adalox for years until the white Hermes stuff came out. The latter is much more durable although I think the abrasive is still aluminum oxide with a better adhesive. Could be wrong about the grit, but the durability is definitely better.

3
Quote:
120 grit should be 120 grit no matter the brand.

Hi Charlie - it almost sounds like he’s using 120g in one of those hard resin discs made for grinders … wouldn’t that give much different results than using the same 120grit in sandpaper with a surfboard specific backing pad?

4

AJ72,

The guys are right, those automotive discs are resin-impregnated for METAL.

Leaves way too much scarring on the work part, and is much harder to handle.

You will need a certain degree of flexibility in your assortment of discs and in

the paper. Usually we start with a large rectangle of paper and cut it to fit

our particular discs. We very rarely use the pre-made resin-backed discs,

with the exception of 3M Green Discs which we use for quick take-down of

hardware, or heavy ding repair sanding.

Like Charlie says, the Aluminum Oxide product is what gets used the most. Some newer

tech papers like Hermes, KlingSpor, etc. are ‘stearated’ papers. This reduces clogging

and maintains more tooth for a longer timeand accurate cut, BUT many builders find it

leaves a wax-like residue on the work part. This can act as a contaminant for subsequent

layers of resin.

Papers for wood tend to be too soft. One to avoid is Garnet, which is way too soft except

for some specialty work.

Good luck on your quest for good paper!

George

5

CHeers for your advice gentlemen…just trying to get smoother results in my glassing which is already such a pain in the ass…i’ll stay away from those heavy duty metal resin paper for the main sanding and use them to take down boxes etc.

ado

6

Besides clogging, early sandpaper failures come from too much heat (can also ruin powerpads). This melts the adhesive and the grit comes off (sometimes imbedded in the glass). Watch the pressure on the sander and keep it moving. The main difference in sandpaper made for metal is the backing material, which is normally an impregnated fabric so that it won’t easily tear going over sharp metal projections. If you’re sanding down finboxes or repairs around jagged glass, the stiffer disks are much better since the edges don’t catch easily like paper backing.