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Lapidary Equipment Archive

Comparison: Lortone QT12 and Thumler Model B

Posted April 14, 2017 By Admin

When polishing rifle brass, wet tumbling with stainless steel media is now the preferred method – for reloaders, this process is faster and much more effective. There are a number of options when deciding which tumbler to buy.  The Qt12 and the Thumler B tumblers are two of the most popular models so we thought it might be useful to do a detailed comparison to help you choose.  Note for reference – the Lortone tumbler is blue and the Thumler tumbler is red. The following table shows the main differences which will be discussed in more detail below:

Table showing differences between Lortone QT12 and Thumbler Model B tumblers (compiled by Aussie Sapphire)

Footprint of the tumblers is very similar although the base of the Lortone is more robust and substantial.  The design is simple and all parts on both are replaceable/available so you can keep your tumbler operational for years and years.

Both tumblers are belt driven. Note that there is NO belt tension adjustment on the Thumler so once the belt starts to stretch, you will need to replace immediately while the Lortone allows some tightening by moving the motor mounting bolts in the slotted holes. There is a belt guard on the Lortone while the Thumler polycord belt is unguarded.

 

The barrels are very similar size (see dimensions in table above) – the Thumler has a slightly larger total volume but is also heavier. When weight rating and optimal load volume is taken into account, this means the load capacity is very similar between the two machines. The Lortone barrel is solid rubber with a double lid system with a single central thumb nut (the boot gasket on the inner lid is replaceable) and 10 internal sides for optimal tumbling action. The Thumler barrel is steel with a rubber liner and separate rubber gasket under the lid which is secured by 6 wingnuts – it is hexagonal shaped. Unlike rock tumbling, brass polishing is a non-abrasive process so you are unlikely to wear out liners or gaskets.

Motors are very similar – the Lortone is fitted with a slightly more powerful version but both handle the job easily.  Both run hot – it is normal for either motor to run too hot to touch but they are designed to work continuously for years (replacement motors are readily available and easily fitted). The Lortone has an in-line switch while the Thumler must be turned on/off at the power point. The Thumler is mounted via two bolts on an L-shaped bracket – if you find the motor vibrates in use, you can block underneath it with a small piece of dense foam. The Lortone is more securely mounted to the base frame with two slotted holes for belt tension adjustment.  Note that it is possible to fit a high-speed motor to the Thumler – the standard speed motor is fitted by default but it can be swapped out if desired.

 

Rotary tumblers run a drive shaft and an idler shaft both of which have nylon bearings.  These should be oiled before use and regularly thereafter with a suitable light oil (suggest Singer Sewing Machine Oil or similar product).  Use of a thick grease or other unsuitable product can damage shafts and cause other problems (gummed-up shafts can also damage drive belts for example). The motor on the Thumler should also be oiled (there are two oil ports either end of the motor) – the Lortone motor does not require oiling.

The Thumler shafts have rubber guides to keep the barrel in place – it should be placed with the lid nuts facing away from the pulley. The Lortone has a barrel guide which fits the lid nut recess as shown below.

Ultimately, either of these tumblers will do a good job polishing rifle brass. Which one you select is down to your particular needs and budget. Note that we do stock smaller Lortone tumblers for those who do not need the capacity of either of these two options – similarly, if you need even more capacity, we suggest you consider the larger Lortone commercial series tumblers (up to 40 pounds compared to the 12-15 pounds of the Qt12/ModelB). When considering what size you need, please use the volumetric capacity data given in this data sheet.

Our full range of rotary tumbler is listed on our website here. If considering other options, please consider availability of spare parts and warranty support from an Australian dealer who is subject to local consumer protection law.  Compared to the very cheap reloader vibe tumblers, these rotary tumblers are a significant investment – make sure you choose one that will be reliable for many years of use and buy from a dealer who can support you with a full range of spare parts.

Note:  this information compiled by Aussie Sapphire for the benefit of our customers. Copying or distributing without permission is not permitted   Click here for a downloadable version of this article.

 

Diamond Saw Blade Types

Posted February 26, 2017 By Admin

Have had a few questions recently about the different types of saw blades so thought it worth a post.

Essentially, there are three main types of diamond saw blades used in the lapidary field – all have their pros and cons.

A) Sintered Blades

Sometimes referred to as Continuous Rim Blades, these blades are more expensive but tend to be longer lasting and offer better performance. Sintered blades are made embedding diamond particles in a metal bond around the rim of the blade – the diamond extends through the full depth of the rim and so as the metal bond rim wears away, new diamond particles are exposed and keep the blade cutting.

These blades are available in premium or economy versions – the manufacturing process is essentially the same but a premium blade will be better quality.  Please note that even though the sintering process will give a more durable blade, they can easily be damaged by incorrect usage (insufficient cooling, rock jams, etc).

For smaller blades, the sintered metal bond rim will be continuous around the whole rim while for larger blades (say above 16″ diameter), there may be sections cut out along the rim to improve coolant flow and debris removal – these are called Segmented Blades.

The 301 Gemking Blade made by Barranca/MK Diamond is often called a Notched Rim Blade but this is a bit misleading.  This one is still a sintered blade but the deep notches along the sintered metal bond rim allow for better coolant flow. This blade is designed for cutting of harder material but MUST be used with oil – water should not be used with these blades. This blade is just a slightly different type of sintered blade.

As the diamond particles are embedded in a metal rim, over time the surface of the metal bond can glaze over the diamond particles and affect cutting performance.  If you feel that the blade is not cutting as it should, we recommend “dressing” the blade by cutting into it a few times with an abrasive material (ie. dressing stick, old silicon carbide wheel, house brick, etc).  This process re-exposes the diamond particles allowing the blade to cut properly again.

B) Notched Rim

A classic notched rim diamond blade is made by pressing diamond grit into the edge of a solid steel core – the process leaves small notches along the rim where the diamond works to cut the material.  This is a much cheaper process compared to sintering and so these blades are generally much cheaper.  They will not last as long but are very low cost for those on a budget.

They can be made very thin which can be useful for those cutting material where you want minimal wastage.  The notches can be very thin or slightly thicker as shown in the photo at left but there will be less diamond to work with compared to a sintered blade so factor this in when considering a blade of this type.

Like the sintered blades, these ones can be dressed if they appear to be slowing down but do this only as needed as these blades are nowhere near as durable as a sintered blade.

C) Electroplated 

Electroplated blades are made by electroplating a thin layer of diamond usually in a nickel metal bond on to the surface of the steel blade. As the diamond is only adhered in a very thin layer onto the surface of the blade rim, these blades are not as durable as a sintered blade.  They are generally quite a bit cheaper than a sintered blade but will not last as long – we do feel that they are better quality than the very cheap pressed Notched Rim blades though.

One advantage is that they can be made very thin so may suit applications where you want minimal wastage of valuable material.  They have also proved popular with our glass customers as a blade that cuts clean with less chipping. Generally not available in very large diameter blades and not suitable for slab saw applications.

These blades should NOT be dressed – this will just wear them out with no benefit. Make sure you are using plenty of coolant – the diamond will rip off in seconds if these blades are used dry or with insufficient coolant.

These are the three most commonly available lapidary saw blades – there are a few other less common types suitable for specialised applications (eg. CBN blades for cutting meteorites or iron-rich material).  Please consider your usage and available budget when selecting a diamond blade.  The three most important specifications are blade diameter, blade thickness and bore size (ie. centre hole) – please note that these measurements are usually quoted in imperial measurements (inches).

If we can assist with any advice, please email us any time.

Gyroc Model B – what’s the problem??

Posted September 17, 2015 By Admin

The Gyroc Model B has been the workhorse machine in many jewellery studios for many years – the smallest 3 pound model is an ideal size for the small scale polishing requirements of jewellery makers.  While the 3A Lortone Rotary tumbler is a similar size and also a fantastic machine for the job, we do find that there are a lot of people out there who learned to use a vibe tumbler and prefer to continue with the method they are familiar with.

Unfortunately, the manufacturer of the Gyroc Model B can no longer supply a working 230V version of this tumbler and therefore we (and other Australian dealers) can no longer supply this machine.  The story is a bit more complicated (you can read more below if you are interested) but here is the current situation.

  • 230V/50Hz Gyroc Model B tumblers are no longer available. The 60 Hertz motor will NOT work correctly in Australia.

Current Options for people needing a tumbler:

  • You can still purchase a 110V version from the USA and run through a power transformer – warranty support will be limited or non-existent but this is an option you may consider.
  • You can refurbish an older or 110V machine by fitting a compatible 230V motor – available here. This is a simple job that does not require any electrical wiring.
  • You can buy a rotary tumbler such as the Lortone 3A instead for cheaper option with similar capacity.
  • You can buy the slightly bigger Thumler Mini Bowl  (available now) – these have a better build quality compared to the Gyroc but offers only one speed as opposed to the two speed pulley of the Gyroc.

gyrocIf we can answer any other questions about tumblers for jewellery polishing, please email us.  For more on the whole sorry saga, read more below: Read the remainder of this entry »

Slab Saw Coolants

Posted November 23, 2014 By Admin

We are often asked what is the best coolant to use in a rock saw and given that there are lot of different “recipes” out there, we thought a more thorough look at this topic would be useful.

The job of the coolant is three-fold:

  • to cool both the blade and the material being cut
  • to flush out abrasive particles formed while cutting
  • and provide lubrication to keep the cutting edge clean.

It is vitally important that you use an appropriate coolant in your saw – this will extend blade life and improve cutting performance. Excess heat on any diamond tool (including saw blades) is the fastest way to damage the tool – using an inappropriate coolant will kill your blade quickly so choose carefully.

TRIM SAWS: for these smaller saws (up to 6″/6″ size), water is generally fine to use as the coolant. Some users choose to add a coolant additive to the water which has a rust inhibitor and surfactants to improve cutting performance. Please note that these additives will not completely prevent rust (you will still see rust forming at the water line if you leave the blade in water) – so we always recommend emptying out the saw reservoir after use. Examples of suitable coolant additives are Covington Koolerant #1 or Tool Cool – there are many others out there.

MEDIUM SIZE SAWS: for saws in the 8″ to 10″ range, we start to need a more efficient coolant such as oil. In a reservoir type saw, water usually does not pick up on the blade well enough to use as the coolant. For saws that use an overhead water supply via a pump, then water can be used as long as it is supplied freely at the point of the cut to provide maximum effect. Excess heat can cause blade glazing in sintered blades or remove diamond entirely for electroplated or cheap notched rim blades.

SLAB SAWS: Water should not be used in large power feed slab saws – water (alone or with an additive) is just not able to cool efficiently and can damage the power feed mechanism. We recommend a good quality cutting oil (light mineral oil) for best results in slab saws – for very heavy duty cutting, you may choose to use a cutting oil additive for better results on very hard stone. We recommend Covington Rockhound Oil but there are other similar products available.

What about the old diesel or kero/oil mix??  This is a traditional coolant and many still use it but there are a few good reasons NOT to use in your saw:

  • These mixes are very flammable with low flash point temperature – it is just not worth the risk of fire or explosion.
  • The unpleasant smell makes it annoying during the cutting and it is very difficult to wash off the slabs after cutting.
  • Dangerous to your health – even when used in an enclosed slab saw, the mist generated during cutting can be harmful. Can also cause skin irritations.

 

A light mineral oil has a much higher flash point (110°C or more) so are much safer to use – if you are cutting very hard rock. adding a bit of Covington Koolerant #2 will increase the flash point even more.  These oils have almost no smell at all, are easy to clean off the slabs after cutting and are much kinder to your body (hands, lungs, etc).  Play it safe – just use the right stuff.

If you are concerned about cost – note that these light oils can be filtered and cleaned for re-use. Low tech filtering can be done using layers of paper bag filters but Aussie Sapphire is now importing the EasyClean oil cleaning units to fit to your slab saw. These will conveniently clean your cutting oil and separate out the sludge for disposal – one initial investment means your oil will last longer, your blade will cut better and your saw will stay in good condition.

See this document from Barranca Diamond for more information on Slab Saw Coolants.

Also review this helpful document on Care and Feeding of Rock Saws (Richard Gindhart).

 

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