Author Topic: 1-1/4" holes in cordierite?  (Read 1031 times)

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Offline red kiosk

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1-1/4" holes in cordierite?
« on: June 07, 2013, 12:05:25 PM »
I'm currently constructing a pizza oven insert for my HastyBake charcoal grill and would like to drill a series of five 1-1/4" holes in a piece of 1" thick cordierite, with the dimensions 3" x 16". The five holes would be equally spaced apart (~1-5/8") and equally distance from the top and bottom (~7/8"). I have access to a diamond tipped 1-1/4" hole saw, so wet drilling the holes will not be a problem. My question is, once this piece is subject to high temperatures (~800F) will it crack? Is there some surface tension, coefficient of expansion or thermo-dynamic what-not that I will be screwing up by drilling these holes? Any help will be greatly appreciated. Thanks in advance!

Jim
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Offline ccgus

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Re: 1-1/4" holes in cordierite?
« Reply #1 on: June 07, 2013, 12:24:19 PM »
I'd imagine that if you just took your time heating up the stone, it'll be fine (I've not had a cordierite stone crack on me yet- they are pretty tough).

I'm curious though- why are you drilling holes in it?  Are you cooking on the stone, or is it going to serve some other purpose?

Offline tombiasi

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Re: 1-1/4" holes in cordierite?
« Reply #2 on: June 07, 2013, 12:27:45 PM »
I'm currently constructing a pizza oven insert for my HastyBake charcoal grill and would like to drill a series of five 1-1/4" holes in a piece of 1" thick cordierite, with the dimensions 3" x 16". The five holes would be equally spaced apart (~1-5/8") and equally distance from the top and bottom (~7/8"). I have access to a diamond tipped 1-1/4" hole saw, so wet drilling the holes will not be a problem. My question is, once this piece is subject to high temperatures (~800F) will it crack? Is there some surface tension, coefficient of expansion or thermo-dynamic what-not that I will be screwing up by drilling these holes? Any help will be greatly appreciated. Thanks in advance!

Jim

I'm no expert in the subject but you definitely altered it's structure. Your concerns are valid. I suspect that you will find out because you will do it anyway :)

Offline red kiosk

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Re: 1-1/4" holes in cordierite?
« Reply #3 on: June 07, 2013, 01:28:21 PM »
Two of these drilled pieces may end up being the sides to the insert box if I need more heat flowing through via the sides. I won't be drilling them if I will breaking well-known thermo-dynamic laws. Right now the un-drilled 3" x 16" sides sit on a 18" x 16" x 1" thick cordierite base and then a 1/4" steel plate serves as the top. This gives me a nice 16" x 16" x 3" oven box. Everything (except the front opening) is covered by a custom 18 gauge stainless steel hood that also covers any exposed grate area of the grill. There is about 1-1/2" space between the top of the steel plate and the custom hood. On top of the custom hood lays a 1"thick piece of #8 ceramic insulation blanket and then the top to the charcoal grill hinges down and rests on the top front lip of the steel plate. The charcoal grill has a large, adjustable-height firebox with a removable heat deflector. My plan is to position the heat deflector directly under the cordierite base and then in the open firebox space on either side of the deflector, in addition to the coals, place chunks of wood. In addition to heat flowing through the oven box out the opening, hopefully the flames and hotter open firebox area will keep the sides and steel plate top as hot as the cordierite base. The holes in the sides are an idea in case I need more of the un-deflected heat and flames entering the box. Another idea is that I could use 1" x 1" x 3" kiln posts on the four corners and really open up the sides. We'll see soon enough. I hope to have some pictures up after this weekend. Thanks again in advance for any help or comments. Take care!

Jim
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Offline Tscarborough

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Re: 1-1/4" holes in cordierite?
« Reply #4 on: June 07, 2013, 05:28:24 PM »
Put a piece of duct tape where you want to drill, top and bottom, and drill through that. Also place the piece to be drilled in contact with wood scrap that you can drill into.  After drilling the hole grind the sharp edge off of it and it shouldn't be a problem.

Offline red kiosk

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Re: 1-1/4" holes in cordierite?
« Reply #5 on: June 07, 2013, 06:40:16 PM »
Tscarborough,

Thanks for for good, solid tips to avoid blow-out and chipping when drilling through the cordierite. I'm still concerned about the thermal integrity of the piece after drilling. Have you gone that route before? Will the grinding of the sharp edges decrease the chances of it cracking outwards from the holes? I know there are bricks with holes, but they are fired after the holes were made in the clay. If no one knows for sure, I just may give it a go next week and see what happens. The more I look at the set-up (did a quick assembly of the box today while I wait for the stainless steel hood to be finished) I think I will need those holes to balance out the temperature. Thanks again for your advice and take care!

Jim
« Last Edit: June 07, 2013, 06:42:28 PM by red kiosk »
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Offline barryvabeach

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Re: 1-1/4" holes in cordierite?
« Reply #6 on: June 09, 2013, 05:24:26 PM »
I have bought a number of pieces of cordierite and cut them to fit diff ovens -  I don't think drilling a hole it in will change its properties .

Offline Tscarborough

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Re: 1-1/4" holes in cordierite?
« Reply #7 on: June 11, 2013, 01:55:04 PM »
As long as you have good clean edges, it should be fine.

Offline Tampa

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Re: 1-1/4" holes in cordierite?
« Reply #8 on: June 11, 2013, 04:50:11 PM »
I think "T" is right - 'you'll be fine' - but I've not seen it done.

I've drilled cordierite and it cuts well.  Use a masonry bit.  I wouldn't worry much about tape on the side you are drilling - it's the backside I'd be more concerned about.  Maybe drill a small hole through the stone, then drill a a little on one side and finish from the other side (to avoid chipping).

In simple terms, the presence or absence of a hole makes no difference in the expansion of a material (such as cordierite).  The interesting part is that when you put a flame on it, then you get thermal stresses (expansion) beginning at the walls of the hole.  Still cordierite, from my experience, is pretty durable stuff - so I think it will work.

Dave

Offline red kiosk

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Re: 1-1/4" holes in cordierite?
« Reply #9 on: June 11, 2013, 06:29:11 PM »
As long as you have good clean edges, it should be fine.

I think "T" is right - 'you'll be fine' - but I've not seen it done.

I've drilled cordierite and it cuts well.  Use a masonry bit.  I wouldn't worry much about tape on the side you are drilling - it's the backside I'd be more concerned about.  Maybe drill a small hole through the stone, then drill a a little on one side and finish from the other side (to avoid chipping).

In simple terms, the presence or absence of a hole makes no difference in the expansion of a material (such as cordierite).  The interesting part is that when you put a flame on it, then you get thermal stresses (expansion) beginning at the walls of the hole.  Still cordierite, from my experience, is pretty durable stuff - so I think it will work.

Dave

Thanks for the info guys. The 1-1/4" diamond tipped hole saw has a 1/4" carbide pilot bit so I should be OK. Plan is to tape the faces of the cordierite and drill on top of a piece of wood 2x4 all under water in a plastic tray. Take care!

Jim

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Offline red kiosk

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Re: 1-1/4" holes in cordierite?
« Reply #10 on: June 15, 2013, 03:55:42 PM »
Well it worked. Had them up past 900F on the grill with lump charcoal and they are still in one piece. Thanks to those that helped with direction. Take care!

Jim

The pathologically precise are annoying, but right!