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Pugaboo

Choosing An Angle Grinder

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I am looking to get an angle grinder for doing kiln shelves. There are a lot of different models out there, what should I look for so that I get one that will work for doing kiln shelves.

 

Here are some of the things I have found I need to choose from (so far):

Amps 7, 9, or 11

Weight of the tool 5-7 pounds

9,000-12,000 rpm

Type of control switch... paddle seems to be preferred

Disc sizes 41/2 or 7

Brand, I recognize quite a few and have always had good luck with DEWALT tools.

 

Once I decide on the model to get I need to know what kind of grinding wheel I will need:

General grinding wheel

Masonry grinding wheel

Diamond

Grinding CUP

Flat grinding wheel

Etc

 

So those of you that have one and use it to do kiln shelves any recommendations? Anything I am not considering?

 

Thanks for your help.

T

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I got a nice Makita on eBay. As Neil says, kiln wash dust will eventually kill the motor. I also got diamond cups and wheels of eBay at a great price. Living in rural areas, I get a lot of my supplies on line. Milwaukee grinders are very heavy duty also.

 

 

Marcia

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Nobody (and I do mean nobody) is a bigger tool Nazi than myself. I went through the grinder deal myself about two years ago and it took me about 6 months to make my selection.  I look at things like design durability and replacement parts availability as well as initial cost.

 

Man, woman or child, union or non union shop or field hand, it doesn't matter; get a rat tailed grinder not the paddle switch.

 

I suffered through paddle switches all of my life having learned on dad's stuff from work in the field. IMO nothing is a bigger improvement in the grinder world than a rat tailed trigger switch grinder. More comfort, better control, max flux capacity; you name it-it's got it. This is true especially if you have smallish hands compared to most men(most ladies and myself :lol: ). My buddy had one of these and I fell in love with it:"

 

https://www.lowes.com/pd/PORTER-CABLE-4-1-2-in-7-Amp-Trigger-Corded-Angle-Grinder/1208961

 

 

I went and bought mine at a pawn shop for $20. It's a good unit and I run mine with a 9" wheel for sharpening mower blades ( I don't recommend this as there is some danger involved) and it's held up well. You don't need a ton of power for a kiln shelf. I don't think you'll be hanging upside down from 360' on a high line with it so you don't need an industrial grade tool. While better grinders do exist, there is no need to go that route (and it does get expensive).  I tend to torture things which is why I usually buy nothing but the best (or the best I can afford depending). I haven't killed it yet despite running oversized wheels on it doing fab work. I'm very happy with it and I am very hard to please when it comes to tools. (ok, well most everything else too.)

 

That being said, I use a belt sander for kiln shelves but not to get glaze off.

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Guest JBaymore

As already said above ... dust kills the motors.  That high RPM motor has to "breathe" to cool itself.  It breathes in a lot of air... with the VERY abrasive dust. 

 

I have a "good" one that I use for cleaning up pots.  But for the kiln shelf business....... Harbor Freight.  Decent tool..... VERY cheap.  A "throw away".   I use GOOD wheels on it however... the Harbor Freight diamond wheels are not as good as Dewalt or something like that.

 

If you are grinding corderite shelves or alumina shelves.... be careful with diamond wheels.  They can eat into such a shelf FAST.  For silicon carbide... diamond is THE way to go.

 

Some people prefer diamond flat wheels... some cup wheels.  If you have a REAL mess..... the cups are great.

 

On a safety note here...........

 

Any crystalline silica that is at temperature over about 2012 F converts to the cristobalite form (different molecular arrangement of the crystal).  The amount that converts is linerally related to the time at temperatures over 2012 F.  Kiln shelves get fired to that temperature and above over and over.  The cristobalite form is more hazardous to breathe than the "normal" microcrystalline form of quartz or flint.  Kiln shelf washes are DESIGNED not to melt the silica component in them.  The more they are fired to high temperatures.... the more of a % of the silica in them is in the cristobalite form.  Kiln shelf dust from grinding is one of THE most hazardous dusts we are exposed to.  Very important to have good ventilation and a well fitting respirator.

 

best,

 

.................john

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I have been using a Makita 4 1/2" grinder for about 15 years. I use it for cutting granite slabs, concrete, and steel...dry diamond blades for the granite & concrete, metal cutting blade for the steel. The tool cost me around $100 when I bought it refurbished and I've had to replace the brushes in it once.

Harbor Freight sells grinders, and all the accessories. The grinders cost around $15. Go to:

http://www.harborfreight.com/power-tools/grinders-buffers.html  to check them out.

To keep the dust from being a problem for the tool as well as you while you're wearing your respirator, do your grinding outside and set up a fan to blow the dust away.

Having been in the construction business for more than 35 years, I've learned that by paying the price for good tools, I've actually saved money over time. I used to buy cheap Black & Decker drills and saber saws. I would pay $20-$30 apiece for them and they would last about 6 months with hard use. I bought my first Makita saber saw for around $170 and it lasted for more than 20 years. The same applied to my drills. I've calculated that by buying good tools I've saved more than $3000 over the 20 year period.

The choice depends on how much you are going to use the tool and how much you want to spend.

JohnnyK

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I hate HF grinders with a passion for many reasons but especially dislike anything with a lock-on thumb switch.

 

A bit about safety:

 

   As a child, I was taught early on that a grinder is an unforgiving monster that will eat your face off if you aren't careful. Thirty five years later, I had a good friend (and very capable guy) have a 4 1/2" wire wheel run up his shirt and across his face. How he isn't blind is beyond me, but it ran across his eye socket and now he looks like a German war veteran. Pug, if you aren't accustom to running one you must pay attention at all times. Loose clothing and a grinder are a recipe for disaster; throw in a lock-on thumb switch and it could eat you alive.

 

Wire and diamond wheels are especially prone to grabbing and sucking in clothing and will not let go. Don't be frightened of it but do give it much respect. They can be very dangerous tools if mishandled.

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I have two Makitas and a few Milwaukees-I tend to use the smaller 4 inch Makitas on most shelve work.I have them in corded and cordless.

Any 4 inch brand will do this job

Get a Masonry grinding wheel and a
Diamond wheel for the shelve work

Be careful with the diamond wheel as it can eat up the softer shelves most use in electrics-the mullite ones that are tan are soft-wether they are solid or hollow core they are soft.I only bisque on them so I never grind them

 

I use grinder is other things beside ceramics so I have some options

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I have a cheapo right angle drill that I use mostly for sanding wood that is on my wood lathe. I also have some grinding wheels that I can attach to it. Sawdust also kills electric motors and I figured it wouldn't hurt to much when I had to replace it.  After each use I use a compressor to blow out the dust. After 10 years I'm still waiting for it to die.

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Wow thanks everyone! Lots of great info... thank you for all the extra safety tips I will definitely use them, I am a firm believer in safety first! I think I will get a smaller model so it's easier for me to control and I will try and get one without a lock on switch or if it has one not use it. I am comfortable with power tools but also treat them with respect, loaded gun respect since they can do just as much damage if not used carefully.

 

My kilns at home I keep kiln washed and know my glazes so other than the once in a blue moon pencil eraser size dot of glaze I only have to do anything with the shelves when the kiln wash starts to flake and chip. Then I go outside, use my mask and a hand tool that looks like a big eraser but has rough stuff on it. It only takes about and hour to remove the old wash and then replace it.

 

The issue I have now is.... drumroll please....

 

I got a job. Yup someone actually decided to hire me.

 

I will be the new Pottery Director at our local art center. I am thrilled to be able to do something I LOVE and actually get paid for it. It's also nice that it is part time so I can still continue growing my own business. I have found I love teaching and it allows me to spend more time doing that as well. I think it will be a good fit, just have to implement some changes to improve it for everyone.

 

In preparation for taking the job I have gone through and checked what needs work and such. Well quite frankly the kilns are in desperate need. One of the first things I noticed is that their kiln shelves are approaching modern art status. They don't look like they have been kiln washed in years, nor has most of the glaze been removed, I sliced my thumb open just picking one up to see if the other side was any better, there was a jagged glaze blob right on the underside. Sigh that was fun. So anyhow there is no way I am getting them in any kind of shape without a major tool to help me... hence the angle grinder search. Personally if I owned them I would just buy new ones, but then if I owned them they wouldn't be in the shape they are in.

 

I think I also figured out the reason they are having so much glaze run off their pots and onto their shelves... their thermocouples are shot, or at least that's my opinion. One of them looks more like a broken corroded pipe than a solid round tipped thermocouple and they use the same thermocouples that my kiln uses so I know what they should look like. I have no idea what cone it's actually firing to, I looked for some cones to put in and test with the load of pieces but couldn't find any anywhere, I'll have to bring some from home to get started helping me figure out just what is going on inside that kiln. I won't know for sure until I fire a load with cones in several places throughout the kiln.

 

I am also going to have to patch some of the kiln bricks, they haven't been using a shelf on the bottom but placing pots right on the floor, along with the accompanying globs of glaze.

 

Don't even get me started on the second kiln that's for another day and another question on brick repairs and digital controller repairs.

 

T

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f12e41be-dfe8-4a6a-9e59-0058d7edc395_400

The motors do not burn out: the brushes clog with dust, preventing them from making contact- so the motor will not engage (start).

I put the picture up: see where the aluminum housing meets the yellow plastic body - right where the handle is attached?

After use, with the motor running: lightly tap on the aluminum housing with a hammer to knock the dust loose. It will blow out the vent ribs, repeat until there is no more dust.   I use mine several times a week, and have for over ten years- but I tap it after use to keep the dust off the brushes and motor.

 

Nerd

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Guest JBaymore

Pugaboo,

 

The best way to "start over" every so often in an institutional setting (or your own studio if it is a big operation) is to take the whole stack of kiln shelves to a commercial sand blasting place.    If they are silicon carbide... tell the folks there to take them down until they are black.  If corderite... tell them to blast til they are beige.

 

It will not cost all that much.  And they will look close to new.  ALL the kiln wash gone.... level surface.

 

This also fits within the H+S idea of "Transference of Risk".  Sandblasting places are set up to handle toxic dust.  You have zero exposure to the process.  And you don't have to invest in appropriate ventilation or make sure respirators fit and so on.

 

We do it at the college every so often...and I do it at my studio.

 

best,

 

................john

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The issue I have now is.... drumroll please....

 

I got a job. Yup someone actually decided to hire me.

 

I will be the new Pottery Director at our local art center.

 

 

 

Congratulations and good luck at your new job

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Nerd's is what I would have gotten had I not bought the PC. It's a really nice grinder (but $100 more). Some, if not all Dewalt's tools sold at HD do not have replacement parts available (either they make a different model or just use a different number with no parts listed). If you do pop for top crop, google the model number and make sure you can get parts for it first. I have run into that problem more than once.

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Pugaboo,

 

The best way to "start over" every so often in an institutional setting (or your own studio if it is a big operation) is to take the whole stack of kiln shelves to a commercial sand blasting place.    If they are silicon carbide... tell the folks there to take them down until they are black.  If corderite... tell them to blast til they are beige.

 

It will not cost all that much.  And they will look close to new.  ALL the kiln wash gone.... level surface.

 

This also fits within the H+S idea of "Transference of Risk".  Sandblasting places are set up to handle toxic dust.  You have zero exposure to the process.  And you don't have to invest in appropriate ventilation or make sure respirators fit and so on.

 

We do it at the college every so often...and I do it at my studio.

 

best,

 

................john

EXCELLENT IDEA JOHN!

I will google sandblasting places and see if there is one near here. I will have to count the number of shelves and call to get a quote. I would so much rather do this than do it with a grinder myself. I am hoping the quote is reasonable and I can sell it to the board as being more cost effective than paying me to grind away at them for hours and still have gouged and pitted shelves at the end. The shelves are the original ones that came with the kilns which I do believe are corderite. Since they are kind if a beige-y color under all the nasty. Sandblasting making the surfaces level again is also a huge bonus.

 

One question is removing that much surface going to make them weaker?

 

You guys are amazing here I never thought of this option thanks again!

 

T

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I am hoping the quote is reasonable and I can sell it to the board as being more cost effective than paying me to grind away at them for hours and still have gouged and pitted shelves at the end............

 

You guys are amazing here I never thought of this option thanks again!

 

T

 

 

Don't even suggest to the board that this is something you could do yourself.  Get a quote and pass it on as a professional service that is required, much like getting in an electrician.  I can't image that the "Pottery Director" job description includes grinding that many shelves.

 

Congrats on the job.

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( If corderite... tell them to blast til they are beige.)

​this means they just take off the the wash-

if you have craters and glaze bumps-they will just blast those areas until they are beige-The wash will be gone but any craters would still be there just biege craters now.

​This all makes sense if you have lots of shelves-if you are only dealing with a few the grinder -coveralls-mask-goggles to me makes more sense

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congrats, terry! :)   you deserve it!   wish you earn a million with it.

 

for any of you really beginning beginners, notice terry's info posted with her member name.  she really was a total beginner with clay when she started in feb of 2013.   look at her now!   she sat with her kiln during the entire first firing just waiting for a  disaster.

 

so, it can be done.  terry has done it fast, she was willing to listen to people and try out the ideas given.  was not afraid of much after the beginning and even replaced scary electrical stuff.  

 

it can be done with willingness to accept the info given and ask reasonable questions after researching whatever was necessary to understand stuff that seemed strange.  bet she has a library of basic books and we all know her studio is CLEAN.

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Like said above, clay dust kills motors...so I no longer buy fancy grinders or drills for studio.  I have a backup pneumatic grinder, but it's limited to being near air supply (and you have to have a large air compressor to keep up with the CFM requirements)

 

I've had no issues with the Harbor Freight grinder (not the $20 one, the $40 version) for the last 3 years, I'm very surprised with the quality of them, especially since I only expect it to last as long as a brand name Milwaukee/Dewalt/Bosch, etc in a ceramics studio, so why spend more?

 

I LOVE the solid-core diamond grinding wheel I got from Si Products, haven't tried one of those "scalloped" diamond cup wheels yet.

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