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Home: General Discussions: Classes & Instruction:
Bead Reamers, enlarging or smoothing holes

 

 


pugdog
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May 2, 2005, 6:07 AM

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Just saw an article on another forum about bead reamers. The writer was obviously excited about "discovering" this tool, but some of the advice was a bit "off". I really dislike misinformation, or partial information, or supposition presented as fact, especially in places people are likely to believe it. Diamond tools are some of the most misunderstood tools. Sort of like the "horror" movies where they pick up a bone saw, and brandish it as a weapon! It's a _bone_ saw. It won't cut skin. It won't cut through your skull unless you remove the skin first. It's an oscillatory blade, that moves about a millimeter back and forth, and uses this motion to cut through HARD substances, not soft plyable ones.

If you look at diamond blades vs regular cutting blades, a diamond blade is blunt, dull, not sharp, and depending on how fine it is, may feel smooth or a bit like sand paper. It will cut through solid granite or concrete like butter, but will go much slower on things like wood or skin which are softer and don't "fight back" as hard. On the other hand, a wood blade may have points, be sharp enough to draw blood on a light touch sitting on the bench, and when powered on, most certainly will chew through your arm or leg in an instant, or slice through that plywood sheet, but it will barely make a dent in that granite block.

So what's going on? Don't sharp tools cut better?

First off, an understanding of "diamond" bits, drills, blades, etc.

"Keeping things wet" is a good advice. But why? Does water help the cutting or grinding? Is there something magical about moisture? Perhaps, but I've done some great grinds _DRY_ as a bone. So, What's up with water?

A diamond blade or bit, uses ABRASIVE action to grind away material. Unlike a "saw" blade with "teeth", or a slicing edge of a surgically sharp tool, a diamond tool uses micro particles of diamond dust to abrade away the material in almost nano particles. But, like with the Dremmel, speed and finesse win out over brute force. The sheer number of little diamonds and the speed of the blade rotation determine how fast it cuts. The fact diamond is also the hardest substand known helps a bit too.

Diamond is _hard_ but it's fragile. Hmmm. Hardest substance known, but fragile? Diamonds cleave. They crack. Hit them hard enough and one diamond becomes two or more. You don't want to "bang" them. You want to let them slide over the material, and scrape it away. Hardness is *not* stregth. Even if we could, we probably would not want to use diamonds to build build bridges or buildings, steel is a much better choice.

*AND* then there is HEAT BUILD UP.

The #1 enemy of a diamond bit is HEAT.

Heat will cause the bit to deform and weaken. It will cause the metal holding the diamonds in place to weaken, release the diamonds, or gloss over the diamonds. Heat build up can also cause the material being cut to crack or shatter. There are numerous other issues, but those are some of the main ones.

A few minutes of excessive heat, and a $20,000 blade can be rendered worthless.

So... back to water. For hand tools, and bead reaming, the items are small, speeds are slow, and heat build up minimal (compared to cutting a 4x6 foot block of granite). Water is ok (and safe) for a lubricant and for heat control.

The bigger the blade, the bigger the block to be cut, the longer the blade will be running, the more heat there is, so the better the coolant and lubricant you need to use. Water is rarely used when cutting larger stones, tiles or blocks.

Ok, most of our bead reamers are under $10 for a set. But that means two things. 1) if we we mess up, it's not too bad, and 2) they are *CHEAP* (eg: CHEAPLY MADE) and not high-tech so heat will damage them more quickly, as will improper use.

Rather than high-tech bonding materials, these are usually just rolled in diamond dust when warm, and the diamonds are embedded in the metal, and held in in little "pits". I realize a picture would be worth a thousand words, but just imagine that the warm metal holds the diamonds like cookie dough holds the chocolate chip. Except, the metal when it gets warm, has a tendency to expand (remember highschool science?) and when it expands, those tiny little dust particles of diamonds can fall out, or be more easily pulled out -- hence rendering the tool useless.

We use the standard bits you can get at the craft stores. For about $10 they come with a pin vise and 3 different bits. We use them in our Dremmel.

We don't do a lot of drilling, or reaming, but when we need to, it's great to be able to make that troublesome bead "fit".

We've found that on the variable speed tools, a setting between 2 and 3 works well. But, a little faster or slower depending on the materials comes from practice.

We use a gentle in and out motion, allowing the bit to grind a little, but withdrawing it to let it cool, let new water into the hole, and to remove some of the ground particles that can clog the bit and slow grinding.

As you practice, you'll get the feel for it, and you'll see how different materials drill differently.

Because bits are tapered, you need to drill a hole from both sides. Sometimes, turning the bead around and drilling from the other side for just a few seconds, can change the hole enough to allow you to continue drilling from the other side again. (Sometimes you want a larger hole on one side). To get a uniform hole, though, you'll have to drill from both sides, then use a much smaller bit to smooth out the middle of the hole where it will be the narrowest. These sets come with a long skinny bit we use for that, as well as a long narrow taper, and a short fat taper. The short fat taper is great for deburring beads and smoothing the holes so they don't cut through or apply too much edge tension on the stringing materials.

Glass beads are a whole other problem. The inexpensive Indian (India) beads are often poorly annealed, and poor quality, and even a few strokes of a HAND reamer will cause them to split or even shatter. Use of extremly GENTLE pressure and light strokes is mandatory. If you are just attempting to deburr it, dipping your tool in water and using light pressure is often enough. This almost dry process is slow, but can work especially for delcate beads. The water is a more of a lubricant and "glue" to hold the dust. Heat build up should be negligible since it's a slow process. A few strokes or turns, dip, a few more. etc.

Bead reaming is an _art_, with just a bit of science (understanding your tools). The more you do, the more you'll learn. And you _will_ ruin a few tools, breat a whole lot of beads, and get quite frustrated in the process. But anything worth doing, takes a bit of effort.

Heat build up is the enemy, and is what you have to watch out for.

Water is not a magic or mystical fluid, just a heat sink, and means to float off the ground material.

(In dry reaming, I rub the blades on a cloth or chamoise to remove the dust, or just dip in water. Some materials I don't want to wet, others, don't need it for hand reaming).

Much if this is practice, and you will ruin a few tools -- it's inevitable. Old diamond reamers may still have life, as higher or lower on the shaft there is still diamond. It might wear out at the most common points, but can still be used for larger holes.

But, the point of this article is it's *NOT* just keeping the tool WET, it's avoiding HEAT. At low speeds, and for small items, water can be sufficient.
PUGDOG's Rock & Bead Shop
Pittsburgh, PA 15217

 
 
 


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