Thread: Fab Shop Workhorse..........The Humble Grinder

Hey there

Cutt off wheels should be quality ................. believe me u dont want a failure mid use. So is worthwhile leaning towards more well known respected brands.

For trade use the new thinner style of wheels offer a few advantages. I use a 1mm wheel with my 4 1/2 inch grinder.The thinner wheels minimise the surface area contact between the material and the wheel due to the reduced surface width of the wheel.

The reduced surface cutting area offers the following benefiits:

1. Improves surface finish on the cut material
2. Generates less heat
3. REduces base material loss during the cutting operation
4. Requires less force for cutting

When working with stainless steel and other high nickel alloys cut off wheels that are sulfer and chloride free should be used to prevent contamination of the stock................In a nutshell ask for an abrasive that suits the material you are working on.

For example different abrasives are used for Mild Steel, Stainless n Aluminium

Always be in control of your grinder particularly when cutting n never try to use a cutting wheel as a grinder

REgards Lou

Gidday

The jurys out on this one for me................I cant honestly say yet which I prefer they both have there place n I prefer different types of wheels for different jobs..........Im hoping a few of the more experienced can give counsel on this one.............

However the recently introduced flap discs grind and finish in one step reducing both the time needed and expense of finishing a product.

When using flap discs its really important to remember that a user can extend the working life of a flap disc by 50% by keeping the angle grinders rpm between 5000 & 8000............

REgards Lou

Generally theres around three types of abrasive coating to look out for when using flap disks..........

The type of coated abrasive you use could impact on your results depending on the job at hand and what type of material your attempting to grind

Types of coated abrasive for flap disks are as follows:

Good: Aluminium oxide is suitable to most general purpose applications. It is specified for use on wood and most metals.

Better:Zirconia alumina grains are sharp and durable providing speedy stock removal and improved service life. Zirconia Alumina based disks are used to best affect in course grits on heavy duty metalworking stock removal applications.........Usually lasts twice as long as aluminium oxide

Best: Ceramic grain abrasives are available in a variety of grits as special products for aggressive and cool grinding. They ensure faster grinding with the addition of offering better surface quality and excellent stock removal rates.

Their cool working properties ensure longer service life & minimise surface discoloration of the workpiece.

Ceramic based abrasives excell for grinding high alloyed steels, titanium, nickel alloys and all extreamly hard materials. Ceramics will usually last 50% longer than zirconia alumina abrasives

So there you have it a nice little basic guide to help you choose the right flap disk for the job.......................

Theres a great little primer on abrasive types from the Australian Industrial Abrasives webpage here:

http://www.australianabrasives.com/belts.htm


Regards Lou

Gidday

Heres a List of my Fav suppliers in regards to Grinding gear to date:

Abrasives Australia
http://www.specialabrasives.com/index.htm

Australian Idustrial Abrasives
http://www.australianabrasives.com/flexiblegrinding.htm

Abrasive Products
http://www.abrasiveproducts.com.au/index.html

Hermes Abrasives
http://www.hermes.com.au/

Saint Cobain Abrasives Australia
http://www.saint-gobain.com.au/

REgards Lou

I find my 5" variable speed Bosch suits my needs. I am a auto body fabricator. I use the fast speeds for grinding and cutting, and the slower speeds using the old fashioned flap discs for weld blending.

I also have a 4" Makita for tight spots. Smaller and much less power, so not as dangerous, and useable with one hand operation when safe to do so.

As for abrasives, it depends what I am building. Regular automotive sheetmetal panels, polished aluminium panels, stainless steel covers, copper radiator housings etc. To do things right I have ended up with no less than 30 different sizes, grits and base material built sanding products to suit my grinders.

Originally Posted by NewLou

Gidday

The Humble right angle grinder in 4 1/2 n 9 Inch forms are the work horses of most metal working shops particularly when it comes to Weld Grinding,

Which of course you wont have to do once you get good at it..

Brickie,
I agree!
Lou knows my attitude to weld grinding.I am quite sure he meant to say weld preparation grinding.

For those individuals still learning the craft, I do urge you to learn the cause of welding defects and how they are avoided. It's all out there on the net if you choose to look.


Sadly, many less well skilled welding operators display their lack of basic welding ability by taking the grinder to almost every bit of weld they lay.

Defect removal is not nearly as effective as defect avoidance.

It costs :

• A time loss
  
• Consumable waste
  
• Energy (as in electric power) loss.

When I taught certification welding welding, I saw those who barely need the grinder had little trouble in achieving a pass where as those that used the grinder as a crutch to attempt the test, fail time and again.

Grahame

Its been a while, but when I was welding the weld looked soooo nice, with stick I used to get the slag pealing off in one long line all by itself..

Originally Posted by peter_sm

I find my 5" variable speed Bosch suits my needs.

The good thing with the 5" grinders is that they have the same size bore as the 9" grinder, so when the 9" wheel has worn down it can be used in the 5"..

If I was to have the opportunity to buy a new smaller grinder I would buy the 5" one..

Thanks Lou,
You have done an excellent job in adding to the groups knowledge of abrasives.

When teaching the senior cherubs I am on their backs about the hazards of angle grinders.
Ignorance and laziness are terrible companions to work with if you are a senior engineering student with a poor safety attitude.
Some don't care about how they get the job done and that includes use of the angle grinder.
I often need to stop the classes and point out hazards

like this:

1. No handle on the grinder-one handed grinding
   
2. Guard removed to get better job access
   
3. Input cable cut to core wire by grinder wheel - no control-see No 1
   
4. The wrong type backing plate fitted to the grinder-dished and flat types.
   
5. The wrong diameter wheel (ie 115mm fitted to a grinder say 100mm ) -extreme vibration.
6. Cracked or damaged wheels left on a grinder

and thats just the angle grinders

Of course none of us would ever do that.

Grahame

Originally Posted by Brickie

The good thing with the 5" grinders is that they have the same size bore as the 9" grinder, so when the 9" wheel has worn down it can be used in the 5"..

If I was to have the opportunity to buy a new smaller grinder I would buy the 5" one..

If you do this, check that the rpm rating of the 9" wheel is suitable for the 5" rating as well. The 5" rpm is a lot higher then the 9" so check first or you might have an exploding disc due to the extra speed.

I have both these sizes and will not use the 9" on my 5" as I have seen them explode and have also been hit by bits as well. The person responsible for this got his behind severely kicked by a few of us that were in the firing line.

Originally Posted by NewLou

..................American made Milwakee units are by far the most popular grinders in our shop.............Will be interesting to see how my German units hold up against em........................

Lou,
just wondering if the Milwaukee grinders are in fact US made now. They were bought out (AFAIK) by Atlas Copco (Swedish multi national) who also bought out AEG (German). They sell some seemingly similar tools with the different branding on it. Might be interesting to check the stickers on them to see of they say "made in USA" or just "Milwaukee, USA"

Mick

Intersting DJ, I worked in a factory for some years welding and they only used the 5" and 9" grinders, I never once saw the wheels disintegrate, and that was over a 7 year period.

Mind you, that was when all the wheels were made here in Oz..

Moral of the story, dont buy the cheap Chinese crap.

That's all good Brickie, but as I said, check the speed rating. The guy from my story use a lower speed rated one and that's why it exploded.