[Rockhounds] Color of Minerals (now: need saw blade recommendation)

[Kris Rowe]

jb, thanks for the great info! This is a great start for a basic primer,
something to work on for one of the Rockhounds @ drizzle' new websites.
Perhaps a primer section for various tasks & equipment?

Thankfully, I've had a little experience with smaller saws, and the 18"
arrived in my hands through the time honored tradition of "Get that UGLY
thing out of the garage!" by a friends wife. I've experienced the 'cutting
edge' breaking, due to allowing a new lapidary (also known as a "friend with
a rock") practice their slicing skills with my 6" trim saw. Amazingly,
suppliers don't want to replace a brand new blade in such a situation.
Imagine that!

Strangely enough, my friend ended up bartering some of his thundereggs (One
word or two? Opinions? I've heard that the Oregon legislature says it's one
word ... and they're the experts, right?) to get the rest sliced open. I may
freehand trimming preforms, but eggs always get clamped securely, since they
always seem to twist when a void opens up. And yes, I know that it's silly
to open eggs with a 6", but ya' works with what you gots!

So, perhaps rule #1 of the primer could be: Be careful *who* uses your saw!

Then there's the 4" thin kerf "Crystal Blade" that I use as an ash tray, one
of many sacrificed to experience. Ah, the things we nonchalantly "forget" to
mention when showing our skills to others, like the heap of dollars each box
of "dished" blades represents! "The dog broke my blade! HONEST!"

So, if I can sweet talk my "Queen of Receipts" into unchaining the Royal
Exchequer (I've learned to duck *quickly*), the MK - 303 will adorn the 18",
and a converted '60's vintage Craftsman arbor will host a Chinese blade in a
homemade tank. Ain't it fun to fabricate? Mechanically speaking, of course.
};)

Thanks for the great input, my friends!
                                                            Kris



On Fri, Mar 20, 2009 at 2:40 AM, jb <jabac at hal-pc.org> wrote:

> DonH wrote:
>
>> Kris Rowe wrote:
>>
>>  I'm currently converting an 18" saw from oil lube to water. Thankfully,
>>> the
>>> saw is equipped with greasable bearings, rather than sealed, and can be
>>> used
>>> with water. A full circulation and filtering system is being installed
>>> and
>>> will hopefuly work! (Mumbling my prayers ...)
>>> I'd love to get some opinions and recommendations on blades for this saw
>>> before spending the precious dollars. What say you, dear list members?
>>> Buy 1
>>> top quality (expensive) blade, or start with cheap import blades and
>>> simply
>>> replace more often?
>>>
>>
>>
>> Greetings!
>>
>> First, by way of helping out, notice that I modified the subject.  You
>> will definitely find on this list that not everyone reads every thread, and
>> if you need help with a specific thing, it's a good idea to post a new
>> message with a new subject... in this case, it would have been good to say
>> "help needed with 18" saw blades."  There are several people on this list
>> who have quite a bit of related experience!  I hope this logic makes sense
>> and it is helpful to you in the future.
>>
>> Now, as far as blades, my experience is limited to 10" and less. However,
>> I can say with certainty that I have always received what I paid for.  Now,
>> I can't compare dollar-for-dollar and brand-for-brand, but in general, as
>> groups, the name brand and more expensive blades perform better, last
>> longer, and warp less than the cheaper ones I have bought.
>>
>> However, I can also say that quality control in developing countries such
>> as China and India is improving by leaps and bounds.  It may well be true to
>> that a Chinese blade of a certain edge style and kerf, though costing 1/3
>> less, may perform as well as one of the big names.
>>
>>  ,,,,
>
>> Good luck,
>> Don
>>
>>
> As noted elsewhere, the MK-303 blades are about the best for general
> lapidary cutting. They have a consistent thin kerf, cut very smoothly, and
> last a long time. I have used all manner of blades in the past decade or so
> with all manner of self-collected (read bashed-up-real-world) materials
> ranging from serpentines to corundum, and the original "Black Blazer" that
> came with the saw and the MK series have been the best performers. I think
> the MK series are better as they are sintered.
>
> For cutting of bulk materials, a good blade to use is the Harbor Freight  7
> or 10 in. diamond blade. They are good and cheap and they last a very long
> time. They are intended for cutting tile but work well on my lapidary saw.
> The disadvantage is that they have a thick kerf and "waste" a lot of
> material. For example, it might take three turns and a little more of the
> screw advance on the rock vise to cut a 1/4 in slab with the Mk-303, but it
> will take six turns to cut the same slab with the H.F. blade. And the H.F.
> blade cuts a much rougher surface, which translates into more time at the
> grinding wheel. The Houston Gem and Mineral Society shop has made very
> effective rough grinders for large spheres, etc. by mounting eight or ten of
> these together on the same shaft; imagine a 10 in. diamond grinder for about
> $350.
>
> Use the MK-303 for your better materials, and the H.F. blade for cutting
> bulk or splintery material into usable slabs. The H. F. blade is excellent
> for beginners to use as it is much harder to destroy it as it is so heavy.
>
> That being said, the principal cause of blade loss is not mis-alignment;
> nor is it wear. The principal way to lose a blade is by not securing the
> rock in the vise enough. Any movement at all of the rock in the vise will
> bend, warp, and otherwise damage the blade, and it might not be apparent to
> you, the user, until a few slabs later when it starts to "not cut right". So
> don't be afraid to cut some of the sharp edges off the rock before you
> attempt to mount it in the vise. Have handy an assortment of wooden spacers
> and wedges to make sure that the rock really is secure.  Test and test again
> to make sure that the rock will not move. Test it again. Only when you are
> sure it is secure do you turn on the saw.
>
> Sometimes a rock will break during sawing from a hidden crack or flaw. It
> happens. It is good shop practice to provide pretty close observation to cut
> things off when it does happen. You may not be able to save the blade, but
> you certainly won't if you don't keep track. A *lightly* bent blade may be
> straightened by tapping on it on a smooth flat surface with a hammer in a
> spiral motion from near the center to near the edge; do not go to the edge
> as it may bend the diamond carrier slightly out of vertical to the blade
> body. Not good. I sometimes can recover blades for more use with a
> lead-filled dead-weight hammer. In any case, the runout on the blade (or
> side-to-side motion of the edge while running) should not exceed a half mm.
> or so. If it's more, the blade will bind and drift in its cut about half way
> into the slab, and cause heat, mist, and eventual shutdown. Incidentally,
> ordinary concrete floors are not usually smooth enough to use in "repairing"
> the blade.
>
> Another thing to watch out for is eccentricity or having a blade that is
> just a bit out of round at the edge. You can tell by the sound of the
> sawing. There will be a little "pulse" in the sound as the  bite into the
> rock varies.  This is caused by not having the blade perfectly centered,
> usually by some kind of bearing wear or bad machining or worn spacers where
> the blade mounts to the shaft. And don't forget to make sure that the flange
> is centered and secure. It is very important in damping vibration and
> keeping the thin blade from destroying itself.
>
> It does not pay to try a professional repair on a blade less than 18 in.
> Just replace it if it is bent too far out of shape.
>
> All of this assumes, of course, that the arbor, blade, and vise have been
> perfectly aligned to begin with. Pay very close attention to alignment,
> especially if the arbor has been repaired or replaced. Being off by a few
> thousandths at the center of the blade translates to 1/8 mm or more at the
> rim of a 10 in. blade, even more for the larger blades. And make sure the
> vise is really at right angles to the blade and is at the same distance
>  from it along its entire length.
>
> Good luck, and enjoy your saw.
>
>
> john
>
>
> --
> _______________________________________________
> Rockhounds at drizzle Mailing List
> Subscription Services:
> http://lists.drizzle.com/mailman/listinfo/rockhounds
> List Home Page, with a link to the List Usage Policy:
> http://www.eclecticlapidary.com/Rockhounds/index.html
>


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
---