#11  
Old 05-24-2011, 02:21 PM
brickie in oz's Avatar
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Default Re: Saw blade question.

Quote:
Originally Posted by Cheesehead View Post
So you're saying I should try to cut a piece of concrete to see if I can rejuvenate the blade?
The professional brick cutters here run the blade through a piece of old hard mortar.

When cutting hard bricks they slightly melt and deposit a glaze on the blabe, running it through the dry mortar removes the glaze.
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  #12  
Old 05-24-2011, 02:55 PM
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Default Re: Saw blade question.

I think if he is cutting on a table saw and not a tile saw then he would be burning through blades quickly if not having water to do it's thing. I did a quick thing so look at my picture and if your blade looks like the right side of my picture you need a new blade. If you have some of the "rough stuff" left you will need to de-glaze the blade. Hope this helps
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  #13  
Old 05-24-2011, 05:16 PM
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Default Re: Saw blade question.

Quote:
Originally Posted by Faith In Virginia View Post
I think if he is cutting on a table saw and not a tile saw then he would be burning through blades quickly if not having water to do it's thing. I did a quick thing so look at my picture and if your blade looks like the right side of my picture you need a new blade. If you have some of the "rough stuff" left you will need to de-glaze the blade. Hope this helps
Definitely got a lot of "stuff" left on the blade, about a quarter inch that has diamonds embedded. And it cuts concrete, and limestone, just not firebrick very well.

Sounds like it's the de-glazing route. I've got some old chunks of mortar & concrete around here that I'll try running through in the morning. If nothing else, I was planning to cut pieces of limestone for the decorative outside arch, I might start cutting that.

I know a tile saw is recommended, but the old cast-iron table saw is what I've got, so I figured I'd give it a go. Worked really well... up until this afternoon.
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  #14  
Old 05-24-2011, 05:31 PM
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Default Re: Saw blade question.

Does the blade show signs of rainbowing?
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  #15  
Old 05-24-2011, 11:11 PM
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Default Re: Saw blade question.

Hi All,

Diamond Saw Blade 101

Here is how to tell if the blade is worn out. Look at the working edge with magnification. If you see the steel core and no diamonds on it then its worn out. There may still be diamonds on the sides of the rim but that is not where the work is done.

Some types of diamond blades are notched and the notches are filled with brazing metal and diamond grit. The notches are only so deep. When they wear down and nearly disappear then the blade is worn out. You may notice an uneven wear pattern because the arbor was not true and one edge of the blade got more action per rotation.

Diamonds do wear out too. Diamonds get chipped and knocked out of their metal matrix and often the blade metal will glaze over the diamonds causing it to slow its cutting ability. This usually happens when cutting very hard material. Diamond blades contain various size diamond grit from fine to coarse depending on the intended purpose of the blade. A small diameter gem sawing blade contains fine diamonds. Larger diamonds are used for rock and masonry. Premium blades usually contain a higher concentration of diamonds than less expensive blades.

Would you like to know how a raw diamond is cut and polished before it is placed in a setting? It is cut with other diamonds. Professional diamond cutters use huge, flat, iron disks divided into several circular segments. They rotate horizontally on a table with a motorized arbor. Fine diamond grit called boart is placed near the center, then the next coarsest grit, etc. (You wouldn't want to place the coarse diamond grit near the center of the wheel because centrifugal force makes it migrate to the outer edge thereby contaminating other segments). Placing the fine polishing boart near the center doesn't affect the larger grit in the outer segments. Up to four diamonds can be polished at a time on the same large disk, in some shops, each one in a different stage of cut/polishing. In the example I saw it took about ten hours to facet the diamond.

Cheers,
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  #16  
Old 05-25-2011, 07:48 AM
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Default Re: Saw blade question.

Quote:
Originally Posted by Tscarborough View Post
Does the blade show signs of rainbowing?
If you're asking if the metal has taken on color due to overheating, no.

I'll cut some concrete & maybe some stone with it today and see if that improves the situation for firebrick, otherwise I'll get another blade.
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  #17  
Old 05-25-2011, 05:45 PM
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Default Bricks need to be soaked!

The blade is OK. I ran some concrete through it, and then cut a few notches out of a piece of basalt.

The first batch of firebrick I worked with had been sitting outside before I bought them and they cut like knife through butter. The second batch were a real b*tch.

Well, those little directions about having to soak the bricks before cutting them? Yeah, d'oh, that means me. Because once I wetted down the new bricks, and deglazed the blade, it's back to cutting like butter. When they were dry, I'd have to run concrete through the blade after every brick or two, and the cutting was a chore.

Getting a little water into the bricks not only cuts the dust down a little, but really helps out in the cutting. I'm pretty confident that I'll be able to get through this project with just the one blade.
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  #18  
Old 05-25-2011, 06:26 PM
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Default Re: Saw blade question.

MK is a good blade, I mostly bought the cheap chinese ones in the tile isle of the big box stores. A proper diamond blade (read: an expensive one) will have sintered diamonds in matrix all the way down to the bottom of the "brass" looking rim of the wheel. The cheapies look like the sintered blades, but the diamonds aren't much below the surface.
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Old 05-25-2011, 07:48 PM
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Default Re: Saw blade question.

Glad you got it sorted out.
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  #20  
Old 05-26-2011, 09:55 AM
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Default Re: Saw blade question.

The killer on the diamond/matrix blades is heat. This melts the matrix. The best is to run them wet or, if that is not possible, then get the bricks soaked.
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