Best pad for 4.5" grinder

[davidpm]

If I want to cut fiberglass quickly what tools do you recommend.

I usually use a 4.5" grinder (don't have a 7" yet) and have tried different wheels.
The 1/4" masonry, the flap sanders like below.

Lets say you have a 3/4" hull with a hole so you want to grind a taper back 9" what will do the job the fastest?



Amazon.com: 3M SandBlaster 9678 4-1/2-Inch 36-Grit Right Angle Grinder Multi-Layer Disc: Home Improvement

[bljones]

why the hell would you want to taper a 9" radius around a 3/4" hole? In any event, I would use a die grinder with a cone burr rather than a 4" angle grinder for the heavy work, then change to a small detail sander to finish up.

[davidpm]

Originally Posted by bljones

why the hell would you want to taper a 9" radius around a 3/4" hole? In any event, I would use a die grinder with a cone burr rather than a 4" angle grinder for the heavy work, then change to a small detail sander to finish up.

Just a hypothetical 12 to 1 taper for a repair, Yes?

[Hudsonian]

I take it the hull is 3/4 " thick and that you are trying to acheive a 1:12 bevel aound the hole. For similar projects I have just used a sanding disc on a 4.5" angle grinder. As I recall, I used an 80 grit disc. It works quite quickly. Of course, wear proper protective gear to include long sleeves, eye protection and a respirator

[Stillraining]

I agree.... a 80 grit flap disk on your 4 1/2 grinder is killer for this...you will be done in 10 min.

[sailingdog]

Originally Posted by bljones

why the hell would you want to taper a 9" radius around a 3/4" hole?

To create a proper 12:1 taper to spread the loading of the repair over the hull with. This prevents the repair from having a hard edge and causing future fatigue and stress related problems, since the repair, if made with epoxy resin, is often stronger than the original hull.

In any event, I would use a die grinder with a cone burr rather than a 4" angle grinder for the heavy work, then change to a small detail sander to finish up.

Die grinders are awfully good at chewing up a lot of fiberglass really quickly, and too quickly to control the taper well. I seriously doubt that you really need more than 60-80 grit...

[bljones]

Ah, crap.
Sorry, david, I had a brainfart. You wrote 3/4", for some reason i read 3/8".
Carry on.

[Capnblu]

The disc you show will work great, maybe a little aggressive, so go gently. You will be finished grinding within a minute. Any more than a light pressure will cause alot of hull to be turned to dust! Hold on real good the first time you touch down, you may be startled how much material can be removed by accident.