Deck / Grinding question

kenny26

Petty Officer 2nd Class
Joined
Sep 16, 2009
Messages
111
I bought a pretty cheap electric 4 1/2" angle grinder and some flap wheels to use for my deck replacement. I cut out the seat bases today with my sawzall, and then i tried grinding the remainder away. The flap wheel (60 grit) kept bogging down the grinder and i didn't get much accomplished and ended up burning out the grinder. Was my grinder just too cheap? What kind of grinders do you guys use? I'm assuming with a better grinder I should get better results... It took like a 1/2 hour to grind out about a 7-8" section of 1/2" plywood/fiberglass that was only and inch wide. I'm assuming it was the poor torque of the grinder and it bogging down that caused my problems. Thoughts? Is a pnuematic grinder better than and electric for this purpose?
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
Joined
May 19, 2001
Messages
26,019
Re: Deck / Grinding question

it has to do with grinder power. I actually have a craftsman and it is strong but bulky...... I have used a makita that was very light and had the same power.

People will chime in but I also have many Northern Tool "off brand" power tools but....Northern has a good (or better then most) warranty attached.

Many other people use harbor freight off brands and I am not familiar with the warranties.

Get a new electric one and use it to death and if it goes replace it with the warranty.
 

83vert

Petty Officer 1st Class
Joined
Sep 10, 2009
Messages
394
Re: Deck / Grinding question

I have a Craftsman that you can not bog down with a flapper. It has got to be the grinder is not up to par.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: Deck / Grinding question

There are a couple of things that may be creating the problem.

60 grit is too fine for removal of large amounts of glass, use 36 grit and try the individual discs, I've never found the flapper type to work that well.

Having plywood in the mix is a killer, it slows the work with a grinder, as you've seen.

The cheapest grinders (I've paid as little as $9.99 at H/F) just don't have much power and when used in a heavy duty application may not hold up for long. They do work very well in light duty though.

You can also get cutoff wheels for the small grinders, they work much better for removing material like you described.
 

Friscoboater

Captain
Joined
Jul 3, 2009
Messages
3,095
Re: Deck / Grinding question

The flappers do not work. I had to go with a really course 36 grit wheel. The flappers just polish.

My grinder is a cheap chicago tool from harbor frieght
 

mark mcj

Seaman Apprentice
Joined
Sep 15, 2009
Messages
45
Re: Deck / Grinding question

I agree with the other posts.
There are different disc for the grinder.
There are cut-off, grinding and sanding disc and more.

Pick the right one for the particular job your doing. I have two cut-off disc one is labeled for finish and one is rough cut. I also have one 4" course grinding disc and one 7" course disc.

For the demo work I've completed so far, I've used a sawzall, cirular saw, 7 inch grinder, 4 inch grinder and an air hammer. :D
This project did justify a new $69 Makita grinder, it included a $24 cut-off disc.
 

system-f

Senior Chief Petty Officer
Joined
Dec 3, 2008
Messages
667
Re: Deck / Grinding question

This is what I have learned:

I have been doing TONS of fiberglass grinding. Sometimes grinding through 1/2" of glass at a time. As was said any wood in the mix will slow down the process big time.

I have two harbor freight grinders one old and one new. Both work great. I have used just about every grinder in existence doing metal work and in the 4-4 1/2" range all are about the same power wise except the cheeper models are much louder. My grinders won't bog unless I really put some pressure on them, but this isn't letting the grinder do the work.

In order to remove A LOT of glass at one time and small amounts of wood use a metal or masonary grinding wheel. The metal wheels are blue at Home Depot and the masonary ones are green. Home depot carries Norton brand and they are by far the best..much better than the Dewalt brands at LOWEs. Be careful though as these grinding wheels will go through a LOT of glass fast. I have done about 80% of my hull and am still on the first grinding wheel AND it shows little signs of wear. I have also found that metal cut off wheels can provide very fast and accurate cutting through glass, but tend to bog when wood is added.

If you grinder is bogging down make sure you do not have too long of a power cord. Although these usually only suck around 6 amps with 100feet or longer of thin cheap power cord this can create enough resistance to matter.

Since fiberglass tends to eat the motors in grinders (you can add a panty hose cover over the air intake/exhaust) I would go with the cheap grinder. Good brands such as Makita, Dewalt, and Craftsman tend to have much more quiet motors. I was really impressed when I used these, but could not justify the cost difference with the kind of abuse my metal working tools get. Though, I have owned one Harbor Freight grinder for 4 years and the other for two without issue except needing the brushes replaced.


There is also a Chainsaw like attachment wheel for the grinder you can get at harbor freight. It is expensive and works great until it dulls which it does quickly when used on fiberglass.
 

drewpster

Commander
Joined
Oct 17, 2006
Messages
2,059
Re: Deck / Grinding question

I had great luck using a plain old cheapo Harbor Freight $30 4 1/2" grinder, Dewalt cutoff wheels and course grit flapper wheels. I did buy a fiber sanding disc backing pad for it and it works great also. I use the flat sanding discs when I am concerned about maintaining shapes because it yields a little better control. If I just want maximum materiel removal I use a flapper.
I also recommend a die grinder (HF) or the Harbor Freight cutout tool. When either of these are used with a good spiral burr you can get in to tight areas and make deep cuts. Be careful with the burr though, it zips through the glass and takes getting used to. I mentioned the die grinder ($40 HF) because the cutout tool quit on me. The die grinder is probably better suited for using a burr.

DSC01064.jpg


By the way, I do not recommend using these tools with there guards removed. The picture is for display only.
 

TitanTea

Petty Officer 2nd Class
Joined
Oct 4, 2009
Messages
102
Re: Deck / Grinding question

Man I used a Harbour Freight grinder and Harbour Freight 4 1/2" ( I think 60 grit) flap wheels and it removed material quick.... almost too quick sometimes....Dont force the tool. Let the tool do the work.
 

kenny26

Petty Officer 2nd Class
Joined
Sep 16, 2009
Messages
111
Re: Deck / Grinding question

The flap wheel removed fiberglass well, but when i tried it to remove the edge of the plywood seatbox core it would bog with the slightest pressure. I have the norton 36 grit disk from Home depot and when i tried it, it bogged down even worse. I think I had a REALLY junk grinder. I'll pick up another one soon, and try the cutoff disks first so i'm not trying to grind so much wood.
 

drewpster

Commander
Joined
Oct 17, 2006
Messages
2,059
Re: Deck / Grinding question

The flap wheel removed fiberglass well, but when i tried it to remove the edge of the plywood seatbox core it would bog with the slightest pressure. I have the norton 36 grit disk from Home depot and when i tried it, it bogged down even worse. I think I had a REALLY junk grinder. I'll pick up another one soon, and try the cutoff disks first so i'm not trying to grind so much wood.

Good idea. The cutoff wheels are definitely better for cutting the big pieces away. The grinder comes into play when you want an area down flush. The cutoff wheels also will allow you to make very fine, small, controlled cut lines. It will smoke some when cutting wood but I still prefer them over a saw. Especially in tight areas and small pieces.
 

kenny26

Petty Officer 2nd Class
Joined
Sep 16, 2009
Messages
111
Re: Deck / Grinding question

Good idea. The cutoff wheels are definitely better for cutting the big pieces away. The grinder comes into play when you want an area down flush. The cutoff wheels also will allow you to make very fine, small, controlled cut lines. It will smoke some when cutting wood but I still prefer them over a saw. Especially in tight areas and small pieces.

Ya, the thought of sawing a hole in the hull and having to repair it doesn't appeal to me :p
 

Squid Billy

Petty Officer 2nd Class
Joined
Jun 3, 2008
Messages
152
Re: Deck / Grinding question

If you promise to keep this just between the two of us, I will tell you my secret.

Here is something I picked up from Harbor Freight for $37.99 and worth every single penny of it. It paid for it self in about 1/2 hours time!
 

Attachments

  • grindersaw.jpg
    grindersaw.jpg
    75.9 KB · Views: 0
  • grindersaw1.jpg
    grindersaw1.jpg
    61.8 KB · Views: 0

kenny26

Petty Officer 2nd Class
Joined
Sep 16, 2009
Messages
111
Re: Deck / Grinding question

I went and bought a new Black and Decker grinder and it is working MUCH better. I still want to pick up that chainsaw wheel for it though that thing looks awesome.
 

F14CRAZY

Ensign
Joined
Aug 12, 2008
Messages
945
Re: Deck / Grinding question

The flappers do not work. I had to go with a really course 36 grit wheel. The flappers just polish.

My grinder is a cheap chicago tool from harbor frieght

go to Home Depot and get the Norton 24 grit disc :D I ain't got time for 36.

and yeah, to me, those flap wheels suck. A 24 grit 4 1/2'' disc on an angle grinder will work wonders. You'll grind glass to oblivion rather quickly. They work great for doing things like making adjustments to your new stringers and deck. Buy a few after a while they tend to break around the arbor.
 
Top