Maverick Abrasives - Industrial Abrasives for Everyone

18 Oct

The Abrasives Prodigy Q & A on Wood Working Chatter

In this week's blog post I do a Q & A on chatter in wood working and what is causing it?

The prodigy Blog: Wood working Abrasives / CHATTER FAQ

Question 1: What causes chatter with respect to sanding belts & wood working?

The Prodigy’s Answer: Chatter marks are most often related to the sanding belt splice or “joint.” A nifty way to check if the belt is causing your chatter problems is to use a piece of chalk or black crayon to mark the splice. After you mark the splice, then run a new, clean work piece through the machine. You will know that the splice is the problem if the chalk or crayon is layered over the chatter marks. Essentially what is causing chatter is the additional thickness of the tape near the joint and thus extra abrasive material digging deeper into the wood than the rest of the belt.

 

Question 2: What other possible causes could there be besides the belts themselves in causing chatter?

The Prodigy’s Answer: Other possible causes of chatter could ALSO be a worn contact drum bearing, Vibration in the machine, worn drive motor bearings, worn idler roll bearings, loose or worn drive belts, flat spots on the drum, out of balance drum or idler, and finally when the conveyer bed is not feeding at a constant rate. Big list I know but I often find that old machines are the true culprit – although its easy to blame the belt itself J

 

Question 3: Okay I know my belts are causing chatter, now how do I fix this chatter issue?

The Prodigy’s Answer: A few things I would do right away. First thing I would do is tighten the drive belts, balance the contact drum, check the conveyer belt/drive belt to make sure its smooth and possibly replace the contact drum bearings (easy and inexpensive fix). Lastly – I would ask your supplier (Maverick Abrasives J ) to make your belts either using a tape on top splice, a top skived belt OR a mavloc splice. I also recommend checking with the manufacturer of your machine … Timesavers Inc. Most likely, or one of the other fine machine manufacturers.

 

Question 4: Okay Mr. Prodigy, how can I identify the chatter marks and eradicate them from the operation?

The Prodigy’s Answer: This is a loaded question but a great one. I have a few thoughts based on my past experiences.

  1. If the marks are uniform and spread across the board, the cause could very well be that the rollers are out of balance or the bearings are worn. Essentially the rollers could have become what we like to call “oval” due to wear and tear.
  2. Poor machine mounting and loose foundation plates on your machine can cause vibration. Check to make sure your machine is mounted correctly and make sure your foundation plates are tightened to shore up any issues with machine vibration, this should be a relatively easy fix.
  3. FINALLY, if you think that the chatter marks are coming from your belt because all other checks seem okay and unlikely, we have a quick and easy way to check if the chatter is caused by the roller or the belt. First sand two work pieces, one of your work pieces at a fast conveyor speed and the second at a slow conveyor speed and then compare the marks. The rule of the thumb is that if the marks are similar, the chatter is coming from the drum, and if the spacing of the marks is different, the abrasive belt splice is causing them. This is because a splice is diagonal and not straight across like a roller.

Question 4: What is generally the cause of most chatter?

Abrasive Prodigy’s answer: In my experience, although the customer always prefers it be the belts problem as this is an easy fix to just get a new batch of belts – it is usually something to do with the steel contact roller. Basically, yes the joint/splice is thicker than the rest of the belt but really its contact roller’s job to absorb the difference in thickness…this is what they are designed to do.

 

Question 5: What is the best way I can be pro-active and prevent chatter marks?

Abrasive Prodigy’s answer:  What I always recommend to my clients is to do what we do – we get all of our machines inspected and maintained on a monthly basis to ensure that everything is functioning properly. Well maintained machines are essential for quality control and we have an engineer / mechanic in house here that comes in one Saturday of every month to make sure all of our machines are running smoothly. I can’t tell you the amount of shops that don’t EVER get their machines inspected and they are always the ones that have to do expensive repairs and spend a ton of money on bringing a consultant out to fix their machine. As I said in my previous question – most of the time it’s a roller issue so always make sure you have a properly functioning drum.

In addition to properly maintaining your machines, there are three other quick fixes I recommend.

  1. Use a platen – When finish sanding use a platen, this will sand less per pass while also spreading the sand over a larger surface are because it is wider than the contact roller. If you run your work piece through a few times during the finishing process with the platen activated, it should give you an unbeatable smooth finish.
  2. SLOW AND STEADY – Tone your conveyor speed down and this will allow more time for your sanding belt to remove the chatter marks.
  3. Rubber hardness – I recommend a durometer of 60 for almost all sanding applications. A harder roller will obviously have less give and cause the belt to eat more into the work piece…which is causing, YOU GUESSED IT….Chatter! J
05 Sep

The basics of sandpaper for a woodworker

Daily Grind / MAVERICK ABRASIVES

Choosing the right sandpaper for your woodworking or metalworking operation can be difficult and recommendations can vary from person to person. There are some basics to keep in mind when determining what process might be right for you. Things you need to take into account are grit, grain structure, type of backing & what material. If you are woodworker or do any kind of wood fabricating and you want to learn a few of the basics of sandpaper as it pertains to your craft – give this article a read!

Know your grits

One of the most basic components of choosing the right sandpaper is figuring out what grit and grit sequence is right for you. Before you can decide the sequence it is first important to know what “grit” actually means. Grit is defined by the number of abrasive particles per square inch on any given piece of sandpaper. This also means that the small the number the courser and larger the grain particle is. For example – a 36 grit grain is much larger and courser than a 120 grit grain.

As a general rule of thumb, sandpaper is generally referred to as course between grits (24 – 80) , with medium being in the (80-150) range, fine being in the (180-220) range & Very Fine being in (240-280) range.

A normal grit sequence in wood fabrication for sanding belts will be grits 80, 120, 150 & finish with 180. Generally, from these 4 grits the woodworker or fabricator will then blend the finish with either a jitter bug or orbital sander using 220 grit. It is important to know that as you progress along your grit sequence from a courser grit to a finer grit what you are doing is removing scratches left behind by the previous grit. When hobbyists or woodworkers fail to properly blend in an even finish along the work piece, you will be left with ripples or an inconsistent finish when you go to stain the wood.

 

Grit Structure – Half Pregnant?

Lets break this down:

Closed Coat Sandpaper – This essentially means that a almost all of the surface area of the belt is covered in abrasive grains, with almost no space between grains. This obviously means that there is more grain on the belt which leads to longer life & more aggressive cuts. This should be the material of choice if you are sanding hard woods such as pine, cedar, douglas fir, redwood, ash, birch, cherry & mahogany. This is always recommended as well if you are working with metal.

Open Coat Sandpaper – Open coat sandpaper means that there is more space between grain particles on the surface of the abrasive sheet or belt. The reason why this particular material is engineered this way is because when you are sanding soft woods such as araucaria, cedar, celery-top pine, cypress, hemlock etc. is there is sap and wood debris that will clog the surface of the belt and the space between grains. This is problematic because as the space between grains gets packed with wood & sap the belt becomes a smooth surface prevent the grains from creating any grab or friction along the surface of the material you are sanding. We do stock open coat material and I recommend you give us a call if you think this might solve some clogging issues you are experiencing.

Semi-Open Coat – Semi open coat generally means that there is roughly 30% less grain on the surface of the belt. This is our standard material that you will find on our woodworking belt pages and we find that this is a great standard because it will fit almost all cases and still give great life.

I will never forget a conversation I had with our old Hermes abrasives rep back when I first started here at Maverick…I asked him do you have any products that are semi-open coat for wood? His reply was “there is no such thing as semi-open coat! That is like being half pregnant!” Needless to say he was wrong…kind of. While semi-open coat VS full open coat is largely arbitrary I will never forget his response & needless to say he didn’t last very long with Hermes Abrasives haha!

 

Types of Backings

Backing types can always be a confusing thing to someone unfamiliar with sandpaper. There are two main types of backings – Paper & Cloth.

Paper – Paper backings are generally most common on two types of products in woodworking, sanding discs & wide belts for timesavers. Paper sanding discs almost always will come in gold or white and are usually 5” diameter or 6” diameter with no holes or various hole patters, a common one being the festool hole pattern. One other important distinction that can be made here is that these discs can also come in two types of applications, PSA which means pressure sensitive adhesive (sticky back) or Hook & Loop (Velcro) which there are advantages to both.

Paper abrasive products can also come in stroke sanding belt form or more commonly for wide belts. The wide belt paper material we carry here at Maverick is widely regarded as one of the best woodworker paper belts on the market in the B317 which is manufactured by Sun Abrasives and is an E/F weight paper. Woodworkers generally go with paper wide belts for their time saver because of a few advantages: Thinner splice which means less chatter, Cost-effective (cost less than cloth), & the paper belt will leave a better finish on the final pass (Pro tip: Use paper belt on last head or last grit of sanding). Obviously the down sides of using a cloth X-weight belt is that they are more expensive & the splice will be thicker and can lead to more chatter issues, although it is still relatively uncommon.

Cloth – Cloth belts are by far the most common types of belts used in almost all industries such as woodworking, metalworking, glass fabrication etc. This is because cloth belts are made from a sturdier, more heavy duty backing generally made from a blend of polyester and cotton. Because of the polyester that is in these backings, these belts are very versatile and can be run in wet applications when warranted. Although you don’t see this in wood applications it is very common in metal fabrication. The advantage of having a polyester backing in woodworking is that you can power wash or clean your belts of any sap or debris that might be clogging your belts. This little trick will extend the life of your sanding belts by 15-20%…HOLY COW!!! J

 

Material – Aluminum Oxide? Zirconia? Ceramic?

Choosing between Aluminum oxide, Zirconia & Ceramic is rather straight forward. Since Zirconia and ceramic are hard structured grains and do not break down easily, they are almost exclusively used for stock removal. Zirconia and Ceramic are only available in grits 24, 36, 40, 50, 60, 80, 100 & 120. While zirconia and ceramic and not that common in woodworking & dimensioning, you do see it in some industries such as the particle board industry where large blocks of wood or particle board need to be ground down. Additionally – zirconia & ceramic will last longer for stock removal and generate less heat…thus less loading from resinous & oily wood as well as glue. PRO tip: you will have less of a chance of burning maple and cherry if you go the route of zirconia or ceramic on your grinding & timesaver operation.

Aluminum oxide is by far the most common abrasive material used in woodworking and depending on the operation you can use anywhere from 60 grit all the way up to 220 grit although if you prefer less aggressive line grains than a zirconia you can go all the way down to 24 grit as well. The reason it is so popular for woodworking is because of how well it fragments under heat and pressure in whats called “friability.” Chances are if you are wondering what material is the best for you in starting your woodworking project, aluminum oxide is the way to go.

02 Aug

Maverick Abrasives Weekly Grind – Sandpaper Joint / Splice – What joint is right for you?

In this article we will be talking about one of the most important aspects of a sanding belt – the splice, which Is the point where the sanding belt is joined together to form a “belt.”

There are 5 main types of joints to consider for your operation:

  1. Butt Splice – This is by far the most common type of joint that you will see and in most cases this is the best option. The butt splice is a splice that will allow your belting operation to be run bi-directionally, meaning it doesn’t matter which way you slide the belt on the machine. It is very common for most sanding belt materials to have an arrow pointing in a specific direction that is essentially an instruction that manufacturer and the customer must abide by if they are making what’s called an “overlap splice” which I will discuss later. The downside with the butt splice is that it is not a 0 tolerance joint however most operations this is not a problem. The normal angle for this butt splice is 67 degrees.
  2. Sine-Lock Splice – This splice is similar to the butt splice in that the joint joins directly with each other, however this has a wave like or zig-zag pattern going along the joint. This joint is most common in glass fabrication or woodworking operations. This pattern allows the belt to run smoothly, without hinging in either direction. This is very common to see on everything from narrow belts to wide belts and even belts for Hetran type machines.
  3. Top Skive – For a top skive belt, the abrasive grain near the joint is removed and shaved off using our scuffing machine. This is used specifically on cloth x weight sanding belts where the joint is leaving a scuff on your work piece. This is most common in wood or furniture manufacturing.
  4. Tape on Top – A tape on top joint is just that, a sanding belt joint with the tape on top of the belt as opposed to on the back side of the sanding belt. This is another form of adding a scuff free joint when sanding across your work piece. This is also very common with woodworking and a special made product

 

NOTES:

The contact drum sandwiches the belt splice between itself and the wood being sanded so when the thickness of the belt is different than the splice, the rest of the belt is prone to leaving a mark. This is due to the joint passing through the contact point, which is generally about 1/8” of an inch through most timesaver machines & this force pushes the abrasive grains on the belt deeper into the work piece you are sanding. The FIX – Use a belt with tape on top or a top skive. These issues are not extremely common so chances are most of the time the butt splice which is the standard manufacturing procedure for manufacturers will be good enough.

The quickest and easiest method to determine if the chatter marks are caused by the belt splice is to take a lumber crayon (or pencil) and draw on the abrasive belt at the spice point.  Then, very lightly, sand a piece of wood and notice where the crayon rubbed off on the wood.  If the distance between marks is the same as what the chatter marks in question were, then the splice is to blame.