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Home made lapidary grinder - Project ---UPDATED-- !

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AlainTernet
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« on: February 25, 2010, 10:16:02 pm »

I'm planning the making of my home made lapidary grinder soon.
The chaft and beiring is the most difficult part to find for me but
after a lot of research I think to use a buffer assemblies (see picture)
as starting point to hold 3 wheels each side.
http://www.woodstockint.com/products/W1681/

But my biggest concern is whether it can work (I think so but...).
In the product manual it is written:

Never use a grinding wheel on this machine
It is strictly designed for buffing and polishing only

But Lortone sell a very similar model (for twice the price) and it seems
to be make for the lapidary work (see second picture)

What do you think? Somebody have already used this kind shaft to
run diamond wheels or expandable drum ?
Thanks for your help !



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« Last Edit: April 22, 2010, 01:04:23 am by AlainTernet » Report Spam   Logged

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Pondmn
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« Reply #1 on: February 25, 2010, 10:30:42 pm »

While in Quartsite I found a  unit manufactured on a limited basis using eight inch wheels.  The motor used was from Jet Woodworking tools and was heavy duty and held 6 wheels.  When put together it looked almost like a Diamond Pacific Titan.  You might contact Jet as the motor is like the one you picture but much heavier duty with two long shafts.  Jerry
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AlainTernet
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« Reply #2 on: February 25, 2010, 11:06:05 pm »

I see the "Theimage" grinder made with a big Jet motor
http://gemstone.smfforfree4.com/index.php/topic,2150.0.html
but I rejected this solution because of the motor price (and especially the shipping
price to Canada, too expensive for heavy items, and I do not find similar item locally). 
Also, I already have old motors and I plan to use only 6" wheel because of the diamond wheels price...

I found the buffing assembly for $ 129 (Canadian $) with free shipping ... It's pretty affordable I think.
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Taogem
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« Reply #3 on: February 26, 2010, 03:01:48 am »

I did a little Google searching in Canada and had no luck finding a dual shaft motor either.

Also checked eBay Canada, and Quebec Craigslistings. 

I just wonder how much one of these type of arbors with the separate electric motors would vibrate with 6 wheels on them.  Maybe not at all... !
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mirkaba
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« Reply #4 on: February 26, 2010, 05:24:09 am »

Looks to me like it would probably work. 3/4 inch shaft should handle 6 inch wheels OK. My main concern would be the bearings. Should have good sealed ball bearings. Sawdust is a bit more foregiving than silicon carbide, diamond and rock dust.....Bob
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Bob

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AlainTernet
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« Reply #5 on: February 27, 2010, 10:07:13 pm »

I do a lot of search too and I did not find any other low cost alternatives.
Finally I ordered today ... I will try it and I'll keep you informed.

I plan to protect bearing as mutch as possible with the frame and splash
guard design (anyway, bearing can be replaced). 
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AlainTernet
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« Reply #6 on: February 27, 2010, 10:33:48 pm »

Now my next questioning, which is best for water:

1- Water gravity drip (fresh water)
2- Spritzers (water recirculation)
3- Pump? (fresh water)

And where is the best place to send the water jet or the drops.
I guess if it's too far (like D on the picture) the water will be
expelled by centrifugal force ? Is that the best place is closest
to the working zone and the cab (like A on the picture) ?


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bobby1
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« Reply #7 on: February 28, 2010, 07:49:18 am »

Though I may be too late for any help, Grizzly Industrial has the same arbor shown above for $109.95.
Bob
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« Reply #8 on: February 28, 2010, 08:17:18 am »

  I built my first grinder with the water drip in the C position because that was how my Highland Park was built.  It finally dawned on me that I was using way more water than I really needed for the job because if I didn't have enough, it would not spread evenly over the wheel.  I built the next one with the drip in the D position.  Not much better.  Overall I'd say it really doesn't make a lot of difference.  If you want enough water to act as a flush, then it should be on top, but even underneath the wheel works well enough to keep the abrasive cool and lubed.  Diamond Pacific uses that for their most expensive units and I've never heard anyone badmouth it.
   As for the source of water, I don't have live plumbing and I hate constant maintenance so I use a five gallon bucket and a one gallon bucket in a cascade settling system and pump clean water from several inches above the bottom of the five gallon bucket.  This also allows me to add borax to the water as a surfactant.
  The buffer arbor is not recommended for grinding because of the length and slenderness ratio of the shaft.  If you get too much weight at the end of a long thin shaft it will start to bend.  Add torque and the bend becomes a twist.  That twist will constantly wind and unwind as the shaft turns, especially if you add drag as in grinding.  This induces vibration which quickly becomes dangerous and a vitreous wheel disintegrates explosively due to the centrifugal force.  Stronger wheels will only cause the shaft to pretzel.  I wouldn't want to be near it in either case.  The math involved in predicting this type of failure is quite involved.  If you are versed in partial differential equations you can find it in most engineering level strength of materials texts.  In any case you would be best advised to keep the heavier wheels as close to the bearings as possible and the lighter wheels further out.  Higher quality steel helps, but it is unlikely you will be able to get access to the steel spec for anything made in China.  A much larger effect can be obtained by moving the bearings further apart and by using a larger diameter shaft, as the shaft stiffness goes up with the cube of the diameter.
Hope this helps
Steve
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« Reply #9 on: February 28, 2010, 08:30:02 am »

We know that E works, because that is how the Diamond Pacific Genie is set up with spritzers.  I would think that A and B would be best for a drip system.  I think the drip system would be preferable as you get clean water and no carry over rock dust or diamond grit, but you need a water supply like a water hookup or a pump and a bucket of water.  The spritzer form is really for using the machine where there is no water hookup, like at a mine or a rock show, where you just poor water into the tray and the spritzers shoot it up onto the wheels along with contaminants like rock dust and diamond grit.  If you have a water hookup or pump and bucket, that would be the way to go in my book and i plan to set that up someday for my Genie.  Here's an example of why we shouldn't use spritzers and recycled water from the tray.  Imagine some really dirty and/or gritty stone.  While grinding it to shape on the first wheel, you get a bunch of rock dust and grit (not to mention diamond grit).  Now for the rest of the process, your spritzers are pulling that gunk up and spraying it onto your wheels and contaminating each wheel along the way.  Not only are you using contaminated water to polish your cab, but your system is sucking the crap up and sending it through your pump which can't be good for the life of the pump.

Mark
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« Reply #10 on: February 28, 2010, 08:41:57 am »

I would agree with Steve on the length of the shafts and their thiness and strength.  They are fine for buffing where there isn't a lot of weight on the end of the shaft, but put a bunch of metal grinding wheels and that is too much weight.  The wheels would need to be right next to the motor and the lighter plastic polishing wheels could go farther out.  I would still be leery of it.  You push down and into the wheels while grinding and polishing and that's similar to adding weight to the end of the shaft.  You should lift one of the sintered grinding wheels and see how heavy they are.  You don't want one of those on the end of the shaft spinning at 1800 rpm.  Oh, and what is the rpm of the buffer or is it adjustable.  It seems like more cabbing machines spin around 1700 to 1900 rpm with 1750 being common.  The cabbing wheels are made to work at these speeds.  I don't think you want to run them at like 3000 rmp, something else to think of.

Mark
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« Reply #11 on: February 28, 2010, 09:19:23 am »

Again, I have no experience with using the softer wheels like so commonly used on the Genies.

With the Diamond bonded type wheels I use on my Highland Park, ( 80, 220, 400 ) I was afraid that the drip system was just not enough water. Especially on my 80 and 220.. As expensive as they are I like a lot ( probably excessive ) of water running over them.

So I place enough water in the tray, with a large sponge in it and beneath the wheels.

I use position C on my 8" expando drums, but dislike that the outer area of the belts don't receive the same amount of water.
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AlainTernet
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« Reply #12 on: February 28, 2010, 11:24:17 pm »

I would like to thank all those who answer my questions!
I know that some questions may seem simple for you, but for my limited
experience in this area, it is very instructive for me.
I never used or saw lapidary grinder other than smalls pictures on the web.
And excuse me for bad English...

Quote
Though I may be too late for any help, Grizzly Industrial has the same arbor shown above for $109.95.

Yes, I saw it, but if I add the shipping cost and customs fee and exchange rates, the final cost will be 2 to 3 time
more expensive... (I am in Canada and it's really frustrating.  And UPS is really the worst! Now I boycot UPS since
some years after  several bad experiences.  Las time I used UPS I ordered a 50$ item, I paid 20$ for UPS shipping,
and when the package  was delivered I had to pay a other 45$ for brockage and custom fees !!!   UPS is robbery
when you shif from USA to Canada...

Quote
...In any case you would be best advised to keep the heavier wheels as close to the bearings as possible and
the lighter wheels further out.
Quote
I would agree with Steve on the length of the shafts and their thiness and strength.

I will try and see what happens.  I'll put the heaviest wheels near the center.
If 6 wheels is too mutch for the shaft, I will use only 4...

About water feed, I will see if I can fin a inexpensive water pump... I think it will be the most practical.
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AlainTernet
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« Reply #13 on: February 28, 2010, 11:55:10 pm »

I make some initial plans of my futur grinder . I have several aluminum plates
that I will use and I adjusted my measurements related to the dimensions of
these pieces of aluminum (some pices are already folded)  My dimensions are slightly
larger than a Genie, but I do not know if I should reduce them...

According to my plan below, what do you think about:

A - Bottom tray height
My bottom tray is 1" higher than the Genie, it is a problem ?
I think it can catch more splash  but maybe a higher edge can be
less practical for work and supporting the arms?

F - Bottom tray depth
The same as above, I plan to make the bottom tray more deeper (about 3 1/2")
than the Genie to have more room to work and to catch more  splash
(I do not want to take a shower every time I use this grinder).
I think that does not cause problems to have more room ?

E - Wheel height
According to my plans I will have the wheels a little higher (the space
between the bottom tray and the bottom of the wheel).
A smaller space is it better to offer the possibility to support hands
in bottom tray ? Or maybe more space allows more movement freedom ?


Alain M-D


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Taogem
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« Reply #14 on: March 01, 2010, 12:53:00 am »

Looks like a great plan to me !

Bet your getting a little excited as you get closer and closer to building this project !

Not sure what "B" is... Maybe a clear plexy or possibly a splash guard ?

Either way... Not to sure about it's location. Looks like it could be in your way while cabbing.

When Ron built his, it was designed around the use of 8" wheels..  I know they are a heck of a lot more expensive.

Would be my first choice if I could afford such a unit..

But just wanted to say that perhaps... Just perhaps, if you left yourself enough room within your housing so as you could always use any kind of 8" diameter wheels down the road..  Looks like the only place you might have to leave just a little more room would be towards the back of the unit.

Just a thought....   :)

Lots of fun watching this come together for you !
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