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Rock Tumbling FAQ

Posted November 4, 2013 By Admin

Rock Tumblers are one of our biggest sellers but you may have questions – see the FAQ below and it is very likely you will find an answer.

HOW LONG DOES IT TAKE?

Time varies but when using a standard rotary (barrel) tumbler, it can take around 4 to 5 weeks of continuous operation. It is usually a 4-step process:- coarse grind, medium sand, fine sand and polish and it often takes around a week per step.

IS A TUMBLER A GOOD GIFT FOR A CHILD INTERESTED IN ROCKS?

Tumblers are a great way to get started in the lapidary hobby – the process is quite simple and although it takes some time, kids love the end product. An excellent way to learn more about our natural environment.  See this blog article for more info on starter kits.

WHAT ELSE DO I NEED?

Apart from a tumbler, you will need silicon carbide grit, some suitable rock polish and a supply of rocks. The silicon carbide comes in a range of grits from coarse to fine. We sell starter kits of grit/polish – Kits A or B are good for about 3 or 4 batches in a 3 pound tumbler.  All components in the kit are available separately so you can restock as needed.  Rocks are readily sourced from the beach, creeks/rivers or keep an eye out for suitable tumbling rock at your local gem show.  Tumblers are listed with optional starter kits or as a complete package deal – just browse here for rotary tumblers of various size.

CAN I USE SAND TO GRIND ROCKS?

Some people use coarse river sand instead of silicon carbide grit to grind their rocks. This method can work after a fashion but it takes a lot longer (ie. more electricity) and you have much less control over the process. We do not recommend this method.  Silicon carbide grit is relatively cheap and works much better.

HOW MUCH DOES IT COST TO RUN A TUMBLER?

The smaller Lortone tumblers only have a very small motor – they do need to run continuously but they use very little power. The 3A and 33B tumblers have a 0.33 Amp motor – based on 230V power supply and cost of electricity of $0.315 per kW hour, running 24 hours a day will cost around $4 per week.  This is slightly less than leaving an 80 Watt incandescent light bulb on 24 hours a day.  Cost of consumables run at around $2 to $2.50 per week or less if you buy in bulk. If you collect your own rocks, this is a very cheap hobby.

ARE THEY NOISY?

While vibratory tumblers can be quite noisy, the Lortone rotary tumblers use a solid rubber barrel which is extremely quiet. The 3A  has been measured at around 55 decibels which is at the lower end of normal conversation. If you put your tumbler in the garage, you probably wont hear it running at all.

WHAT ABOUT WARRANTY?

Aussie Sapphire provides full warranty support – the warranty period on tumblers is 12 months and is handled at our NSW office/workshop. In many cases, we can remotely diagnose and provide parts – sometimes it is required to send the machine back for assessment. Warranty issues are rarely experienced – these machines are robust and reliable.  We keep a full range of spares and accessories in stock.

TUMBLER MAINTENANCE – WHAT IS REQUIRED?

Rotary machines are quite simple and there is not much to go wrong. We recommend oiling the shaft bearings with a light machine oil (Singer Sewing Machine Oil or similar) – just a drop or two every 30 days of operation. At some point you will have to replace a drive belt – these only cost a few dollars and should last up to a year or more depending on usage.

WHAT SIZE ROCKS CAN I DO?

This depends on what size tumbler you buy. A 3 pound tumbler has a barrel of about 10cm diameter and 10cm depth – you fill the barrel up to 3/4 full of rocks so your rocks need to be small enough to move freely within that barrel size. It is a good idea to have a mix of sizes to optimise the tumbling action. If your rocks are larger, then you need to move up to a larger size barrel. Dimensions of the various barrel sizes are provided in the listings. A good rule of thumb is to tumble rocks that are no larger than half the diameter of the barrel along with a generous mix of smaller rocks – probably only one or two of these larger rocks – remember you need sufficient room for the rocks to tumble and grind.

SHOULD I GET A ROTARY OR VIBRATORY TUMBLER?

These are very different – if you are just starting out in rock tumbling, we generally recommend a rotary tumbler as these are easier to use for beginners and do not require as much monitoring during use. Vibratory tumblers work faster, use less consumables (grit/polish) but require checking twice daily to monitor correct slurry consistency. Rotary tumblers are slower but can be left to work without fuss between stages and are generally much quieter during operation.

WHAT THE DIFFERENCE BETWEEN STARTER KITS?

For rotary tumblers, we recommend two starter kits – A or B. Both kits contain the same 3 grades of silicon carbide grit (500 grams each of #80, #220 and #600) – you normally use about 3 to 5 tablespoons of grit per kilogram of rock. You do need to throw out the silicon carbide slurry after about a week of grinding – it is not toxic so you can dry it and throw out in the garbage.

Kit A has 250 grams of Cerium Oxide polish – this one is good for rocks around hardness 6 to 7 which includes the quartz group (petrified wood, jasper, agate, amethyst, etc) or glass (natural or man-made). Kit B has 250 grams of Tin Oxide which is more general purpose and works well on harder rocks such as garnet or topaz as well as the softer rocks – it also contains an additional pre-polish step (500 grams #1500 Alumina) which can help if you are having trouble getting a good polish.  Note that you can recycle polish slurry a few times before discarding.

Both Kit A or B should do around 3 or 4 batches in a 3 pound tumbler. They also contain a small packet of plastic pellets which are used as filler in later stages.

I WANT TO POLISH METAL INSTEAD OF ROCKS – IS THIS POSSIBLE?

Tumblers are great for metal polishing – we sell many tumblers (both rotary and vibratory) for this job. The most popular tumblers for polishing silver jewellery is the Lortone 3A or the Gyroc Model B. Larger tumblers are generally preferred for polishing brass for reloading. You need different media for working with metal – for polishing only, we recommend stainless steel shot and burnishing compound.  This blog article has more information on using the 3A for polishing jewellery.

PAYMENT AND POSTAGE OPTIONS?

We post every day. Note that due to the heavy weight of these items, courier delivery is via Star Track Express – this is a road service and is NOT necessarily faster to some locations. If you need your tumbler in a hurry, please check with us first but it is better to plan your purchase allowing for postage time. You can check postage cost by adding item(s) to the shopping cart and using the shipping estimator on that page – you can do this any time.   We have a range of payment options to suit you – select at the checkout from Visa/Mastercard, PayPal, Bank Deposit or Cheque/Money Order.

Do you have even more questions?  You are bound to find the answer in one of the following websites:

http://rocktumbler.com/questions.shtml
http://www.dadsrockshop.com/faq/faq_tumblers.html#1

Info about Stainless Steel

Posted January 31, 2013 By Admin

Stainless steel is an important material in the lapidary industry so we thought it might be a good idea to go over some information to help you understand more about it.

Stainless steel is an alloy of steel with a minimum content of Chromium (at least 10.5%) – there are a range of different alloys available which are designed for different jobs and have different properties.  The commonly used alloys have a chromium content of around 18% but content of other metals (notably nickel) varies and does alter physical properties of the steel. When comparing between products or suppliers, it is a good idea to know exactly what you are purchasing.

IMPORTANT: Although Stainless Steel does not readily corrode, rust or stain with water like carbon steel, is CAN rust or discolour under certain types of conditions (namely high humidity, salinity, etc). A more accurate name would be stain-resistant steel – not quite as catchy but it would alert people that you still need to take care of your stainless steel products. Important warning: do not mix stainless steel and carbon steel shot when tumbling – the carbon steel shot may contaminate the stainless and cause rusting.

The 3 most common types of stainless steel we would normally encounter are as follows:

  • Grade 202 – low nickel alloy with less corrosion resistance compared to the 300 series alloys (less common in Australia)
  • Grade 304 – General Purpose; the most common grade with good corrosion resistance for most jobs
  • Grade 316 – Marine Grade; more expensive but recommended where high corrosion resistance is required

The two main products we stock that are made of stainless steel are the Stainless Steel Shot (mixed shapes) and various sized cabbing arbors.

Stainless Steel Shot for tumbling - Aussie SapphireIt is important to note that our Stainless Shot is made from Grade 304 with accompanying certification tests from the manufacturer.  We have noticed some other suppliers selling Grade 202 shot – if made from 202, then it SHOULD be cheaper and will be less rust resistant. When comparing prices, be aware that these products are NOT the same.

We do recommend that whatever grade of steel your shot is made from, it should either be stored completely dry OR completely covered by shot storage solution. If you store your shot in a sealed container when it is still damp, even stainless will rust under these conditions. If you notice some discolouration on your stainless shot, then quick action can retrieve the situation if you wash it thoroughly in a weak acidic solution.

More info in the link below:

http://www.cooltools.us/v/vspfiles/images/tumblercontamination.pdf

Stainless Steel Arbors - Lortone - Aussie Sapphire

 

For your reference, our Lortone Stainless Steel arbors are made from Grade 304 stainless with grade 416 shafts for maximum strength. This gives the best combination of corrosion resistance and strength – they are more expensive than the power-coated classic options but you know you are buying long-lasting quality.

Even so, we always recommend wiping down your arbor after each use to keep it in top-top condition. Cleanliness when cabbing or faceting is a good habit to get into – it helps protect your equipment and significantly reduces the chance of scratching occuring due to rock dust/diamond contamination.

 

See these links for further reading:

Hope this information helps clarify some issues around stainless steel – if you have any other queries, feel free to contact us any time.

Cheers from the Aussie Sapphire team

www.aussiesapphire.com.au

Rock Tumbling for Kids

Posted November 25, 2011 By Admin

At this time of year, we tend to get a number of enquiries from parents wanting to buy a rock tumbler for their children as a gift.

Kids Tumbling Kit - 3A Tumbler with Accessories from Aussie SapphireWe find that many children are already very interested in the rocks and stones they find in their environment and excited to learn more about them.  Tumbling is a fantastic way to encourage and develop this interest.

Rock tumbling is a very simple process and affordable to get started – younger children may need some assistance and/or supervision but this is a really good opportunity to spend time with your children.

Basically rock tumbling is the process where rough rocks are polished into smooth and shiny stones which can be used for a variety of purposes.

We have designed a kit specially for parents needing a gift idea – this kit contains a 3A tumbler and everything you need to get started in one convenient package – great for anyone aged 7 to 107.  If you want to get a bit more serious, we also have a 33B kit which contains the double barrel tumbler.

Types of Tumblers:

Choosing the correct type of tumbler is very important.  “Toy” type tumblers are readily available from Ebay and some toy shops – these are specially designed to appeal as a gift for children but have some serious limitations.  These usually sell for just under $100 and come with a small kit of abrasive grit and rocks so you can get started straight away.  A couple of examples are pictured below:
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rolling-stones-rock-tumbler

WE DO NOT RECOMMEND THESE TUMBLERS

While these types of tumblers seem very cheap, we do not recommend them for a few reasons:

  • Small barrel size restricts how much rock you can process.
  • Light plastic construction does not last well – we have had reports of barrels cracking and leaking after only 1 or 2 batches.
  • Small size of motor – tends not to last, may fail very quickly – cannot be replaced or repaired.
  • Plastic barrel with lack of sound proofing means these are very noisy to operate.
  • Once they fail, difficult or impossible to get spare parts.

When buying tumblers for children, parents are often concerned whether the interest will be a lasting one.  Even though the “toy” type tumblers are somewhat cheaper compared to good hobbyist machines, their short life span and operating limitations mean that you are likely to be disappointed in your investment.  We find a number of customers upgrading to a Lortone tumbler once their toy tumbler fails (often after only one or two batches) so in these cases, it would have been much better to buy a more reliable machine in the first place.

RECOMMENDED TUMBLERS 

When selecting a tumbler for children or those new to the hobby, we recommend you purchase a more reliable machine.  If you buy wisely, even if you find that your children lose interest, you should be able to sell your tumbler for a good price.  We believe this is a much better way to go.

lortone-3a    ar1-tumbler

The Lortone 3A is a good choice for this purpose as it is widely sold in Australia, extremely reliable and great value for money.  There are other brands of rotary tumbler in this category such as Thumler which are also good choices.

What to look for:

  • Rock tumbling will always make some noise but the Lortone has a rubber barrel to drastically cut down on noise.
  • Rotary tumblers are very simple but spare parts (drive belts, barrels) are readily available for the Lortone and other good hobbyist machines
  • Motors are designed to work continuously for long periods without any problem – your Lortone tumbler should work trouble free for years with just regular oiling as indicated and perhaps an occasional drive belt replacement.
  • Good re-sale value – there is a strong market for used lapidary gear of good quality.
  •  Versatility – these tumblers are useful for other jobs as well – polishing small metal parts or jewellery, processing glass for mosaic work, and a variety of other arts and craft uses.

REMEMBER:

Rock tumbling is a slow process  – you wont get results overnight so make sure your kids are prepared for this.  Some of the harder rocks can take weeks to complete (4 – 6 weeks is typical).   This is not a big problem for 2 reasons:  a) your kids will learn the value of patience as they work through the process and b) the weekly cycle of grit changeover can work in well with your lifestyle where we all tend to be busy with school and work during the week but can spend a little time on the weekend with hobbies and activities.

You will need a range of grinding and polishing grits to smooth and polish your rocks.  Replacement grit is readily available and cheap but you will need some to start so check this when purchasing.  Different polishes are used for different types of material so you may find some trial and error is required to fine tune the process.

tumbled-stones

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Not all rocks will polish – a rule of thumb is if the rock is shiny when wet, it should polish well in a tumbler; if it stays dull when wet, it is unlikely to polish well.  You should not polish rocks of very different hardnesses in one batch as the soft rocks may be worn away by the harder ones.

You can tumble other materials – try tumbling pieces of glass for mosaic work or for a “beach glass” effect, pieces of metal or various types of “sea beans”.  These may require different types of polish but the possibilities are endless.

Hope this gives you some information to start with when considering buying a small rock tumbler.  We are always happy to answer questions on this so feel free to contact us.   If you want to do a bit more reading on the subject, see the article on our website.  If you are ready to buy, we suggest our special Kid’s Tumbling Kit with everything ready to go in one package.

Good Luck from Aussie Sapphire

Gyroc Tumblers – How Much Shot?

Posted August 20, 2011 By Admin

The Model B Gyroc Tumbler is a really popular tumbler for jewellery makers – this fast and reliable tumbler is an ideal size for polishing small batches of gold or silver jewellery.  However, it can be difficult to know exactly how much media to use – we get quite a few enquiries on this so thought we’d take a few photographs to help you out on this issue. Please click the link below to see these photographs and rest of the article.

Vibratory tumblers tend to work best when they are filled quite full – for best results you can fill the bowl up to about 15mm from the top.  However, if you use a very heavy media such as stainless steel shot, you run the risk of overloading the tumbler if you add too much.  So if you want to use shot as your polishing media, you need to compromise between adding enough to polish well but not so much that it overloads your tumbler motor.

The Gyroc Model B is rated as a 3 pound tumbler – this means you should try and keep the maximum weight under 3 pounds if possible – ie. when the bowl is loaded with parts, media and water, the total weight should not exceed 1.4kg.

If you buy your stainless steel shot from the USA, you will often find that it is sold in 1 pound lots – this is about 450 grams and in my opinion, is not enough to do the job properly.  Please note that there should be no need to buy your shot overseas – our prices are really competitive so please check before you pay expensive freight costs.  I feel that 1kg is a much more appropriate amount – perhaps even a little bit more.  View the photos further down in this article to see what I mean…

Read the remainder of this entry »

Expanding Drums

Posted April 22, 2011 By Admin

People looking to get into cabbing will often choose an arbor with vertically mounted wheels to grind and polish their gems.  These machines come in a variety of formats with 2, 4 and 6 wheels set-ups being common.

If you have a machine with 6 wheels, generally you will have the full range of grits readily available to you so that you can process your stone without having to change wheels.  If you have a 2 or 4 wheel machine, the need to change wheels can be a little inconvenient.

expdrum

If you are in this situation, you might like to consider using an Expanding Drum which allows you to easily slip a belt on and off in moments.  A cheap and convenient option with the versatility of being able to run silicon carbide or diamond belts – even other materials such as felt.

 

General Notes

Most belts should fit easily and tighten when drum is run at recommended speeds.  If you have a belt that appears to be too loose, you can try fitting belt so that it runs in the opposite direction or running drum at a slightly faster speed.  Drums need to run at a speed of at least 1725 rpm or the rubber will not expand enough to hold the belt securely on while running.

Do not use too much pressure – a light touch is recommended so that you do not damage or move the belt on the drum.  Heavy handed operators may find flexible wheels more forgiving in this case but you will get better results with a gentle touch when cabbing so it is something to keep in mind generally.

Diamond belts MUST be run with water – do not run dry or you will damage the belt.  Ensure that you have a good coverage of coolant over the whole width of the belt to avoid overheating problems.

Although diamond belts are far more consistent over their lifespan compared to silicon carbide belts, they can benefit from a “break-in” period – this particularly applies to the finer grit belts (#3000 or finer).  If you find your new diamond belt is scratching, we recommend dressing the belt by lightly running a piece of aluminium oxide dressing stick or agate over the surface – make sure you flush well with water while doing this.

Silicon Carbide OR Diamond – which is best?

No easy answer as both have their place.  Silicon Carbide belts are much cheaper so the initial investment is lower.  The main difference here is that the action of silicon carbide belts will change over time – the grinding action starts out aggressive and then gets finer as the silicon carbide particles wear.  Diamond belts are more stable over their lifespan with a more consistent cut rate and surface.

Note that you can mix and match using cheaper silicon carbide belts for rough grinding material and then move to the more expensive consistent diamond belts for the finer touch up work.  If you find that your finer grit silicon carbide belts are wearing quite quickly compared to the coarser grades, you may consider upgrading to diamond belts for these and using the cheaper silicon carbide belts for roughing out.

Expanding Drums or Flex Wheels – which is best?

When deciding how to set up your machine for diamond, the obvious choice is Expanding Drum or Flex Wheel (Nova or similar type).  If you have sufficient space to run a full set of Flex Wheels, this is a convenient way to operate.  However, the use of an Expanding Drum gives you two important advantages:

  1. Flexibility to quickly swap between grits and different belt types.
  2. Wider belts mean extra work space for cabbing.

A standard 6″ Flex Wheel is 1½ wide but an expanding drum belt is 2½” wide – this means using a 6″ expanding drum gives you 66% more surface area of diamond compared to a standard 1½” wheel.   Using an 8″ expanding drum gives you 50% more surface area compared to a 2″ wide flex wheel and a massive 100% more area (double) compared to a 1½” wheel.  Apart from more diamond, the generous width gives you more room to work across the belt making it easier to cab larger stones.   Something to consider when the budget is tight!

Compare size of 6" Wheel or DrumCompare 8" Wheel or Drum Size

Where to Buy?

Aussie Sapphire has a complete range of Expanding Drum belts for the 2 most common sizes:  6″ x 2½”  or 8″ x 3″.  Click the links below to browse our range:

Aussie Sapphire also has a wide range of 6″ and 8″ cabbing machines, expanding drums, etc.  If you need advice, please feel free to contact us any time.  We aim to stock the largest range so you can have maximum choice in lapidary gear.