Preventing Tear out

[Dak0ta52]

I've experienced tear out on the backs of many of my projects. If the material is thin enough, I'll double stack which will allow one without tear out but I still experience it with the bottom piece. This will happen even with reverse type blades. I use shelf liner to attach my patterns using adhesive spray. My question is, has anyone tried attaching shelf liner to the back (bottom) of the project material to help prevent tear out? I plan on trying this on my next project. My idea is that the extra layer of adhesive from the liner will give additional cooling to the blade, help the project move on the table as I'm cutting and help hold the bottom secure and hopefully prevent "some" tear out. Has anyone tried this and if so, was the outcome positive or negative?

[Norm Fengstad]

I cut a lot of baltic birch some pieces seem to be more prone to tear out. also noted that as blades get duller tear out is more pronounced even with  reverse blades. Sometimes I get to aggressive during cutting and that doesn't help either. My conclusion is tear out is condition of our sport

[teachnlearn]

Combination of type material and blade. Tearout happens with circular saws too. Its the tooth existing the wood and pushing the wood and tearing rather then cutting it. Can be the blade is dull. This plagues finish carpenters when using soft woods. Choosing hard wood, taping the cutts or layer as you do helps with soft woods, but its going to happen. RJF

[Dan]

Rodney, I've had success and frustration with using painters tape to prevent tear out. Usually the cuts seem clean and sometimes the tape comes off well and I get a pretty good cut. Other times the tape seems to pull some of the wood fibers up. I usually just live with it. It seem the more cuts on the pattern the less anyone, including myself, notices the tear out. And, if it's on the back, it bothers me none at all. I've also heard of some folks putting one coat of a finish on the project. Not sure if it helps reduce tear out but it may be something else to try.

Good luck! 

[BadBob]

Use something cheap for the bottom layer. Hardboard, MDF, underlayment, plywood, and paneling come to mind. Consider the bottom layer sacrificial and throw it away.

[FrankEV]

Dol you sand the back side?   If not you should!

I sand my panels (ply or solid wood) on both the pattern side and the back side to a min 600 grit finish before cutting.  Takes only a few minutes as I have two palm sanders plugged in and one is fitted with 200 grit paper and the other with 600 grit paper.  I sand untill I get a nice uniform smooth to the touch finish.  Then Tack cloth before attaching the liner materrial.  

This helps in two ways. First the shelf liner/pattern comes off cleaner with minimun lifting of fibers.  Second, eventhough I get lots of fuzzies on the back side because I mainly use spiral blades, I get NO tear out.  However, I must qualify this a little.  Let me say I do not normally cut any softwoods.  I only use quality ply products intended to laser cutting or solid hardwods like Oak, Maple, Walnut, etc.  If you are using inexpensive Luan or other Box store plys and/or softwods like pine or white wood, tearout is  something you will need to live with. 

Blade quality and type can make a diffeence.  Also,  improper blade tension and speed can cause poor cuts.  I try to maintain proper tension but have slowed my blade speed considerably while pushing as lightly as possible letting the saw do the cutting.  Extends blade life and creates cleaner cut lines and less tracking wobble. 

One other thing I do is to clean the back side of a panel frequently during extended cut periods with my sanding mop.  This removes a lot of the loose fuzzies and helps allow the panel to slide on the table unimpeded.  Smooth sliding of the cut panel allows the cut to track better with no unintentional stopping/starting that can occur when there is resistance from a build up of material attached to the back side.  

 

   

[Roberta Moreton]

Frank, I NEVER considered sanding the back during the cutting process. 
I will be doing it from now on!

[Foxfold]

15 hours ago, FrankEV said:

One other thing I do is to clean the back side of a panel frequently during extended cut periods with my sanding mop.  This removes a lot of the loose fuzzies and helps allow the panel to slide on the table unimpeded.  Smooth sliding of the cut panel allows the cut to track better with no unintentional stopping/starting that can occur when there is resistance from a build up of material attached to the back side. 

I do this, but in my naivety I thought it was something everyone did. 

[FrankEV]

1 hour ago, Foxfold said:

I do this, but in my naivety I thought it was something everyone did. 

I know a lot of us wax our tables often to help sliding and I certainly did not think I was the only one who did this.  However, it hasn't been something I had seen mentioned before. 

My entire response was directed toward those who may be realtively new to the Scroll world and might gleem something new and useful from some of the things I myself learned along the way from others and from my own experiences.

Edited September 16, 2021 by FrankEV

[Woodrush]

16 hours ago, Roberta Moreton said:

Frank, I NEVER considered sanding the back during the cutting process. 
I will be doing it from now on!

I used to sand, but now I use a micro torch on the back of all my pieces. It works great, and is super guick

[Foxfold]

5 hours ago, FrankEV said:

My entire response was directed toward those who may be realtively new to the Scroll world and might gleem something new and useful from some of the things I myself learned along the way from others and from my own experiences.

Don't doubt it for a moment Frank, I just hadn't realised that people 'didn't'. Like you say, until something comes up in conversation it doesn't get discussed.  There's a lot of things in life like that I suppose. 

[FrankEV]

2 hours ago, Woodrush said:

I used to sand, but now I use a micro torch on the back of all my pieces. It works great, and is super guick

Yep, I do too.  I was talking about "before cutting" to minimize tearout on the back.

[Jim Blume]

I do most of my portrait cuts on Baltic Birch 1/8" in a 2 or 3 stack. If I am going to be cutting only a single, I use 1/4" instead of the 1/8". I find it easier to control that way. Single 1/8" is difficult for me to control. I don't use shelf paper or tape but simply use a repositioning spray (Locktite 100 or Elmers) to affix the patterns and then mostly use Flying Dutchman # 1 Ultra reverse blades. That style blade is 2 teeth down, one up in repetition throughout the blade. I do get some slight fuzzies on the back side but don't seem to get tear outs. Every 20 cuts or so, I do turn the project over and sand the back with a mouse to get rid of the fuzzies so the project will slide easier on the table. My wife likes the FD Polar blades which are really fine teeth and easy to control but has no reverse teeth and leave lots of fuzzies, but again no tear outs. She also sands the back side with a Mouse every dozen cuts or so.

I have tried all the newer methods and techniques but keep going back to what many refer to as old school. I often say in jest, I do it all wrong according to some of the experts. Old school straight blades and what I had learned many years ago from folks like Patrick Spielman and Dirk Bolman have worked for me for so long, this old dog will keep on using his old tricks.

I often get asked "What is the best way to do this or that? My answer will always be the same. No. My way may not be the best way. It is one way and it is the best way for me. I suggest to all folks who want to develop "their own personal best way", is to try all the different methods, techniques and products available and determine what is the best way for you. And yes, even old dogs can learn new tricks for if not, I would still be tracing patterns with carbon paper onto my work piece.
 

Edited September 22, 2021 by Jim Blume

[FrankEV]

2 hours ago, Jim Blume said:

...If I am going to be cutting only a single, I use 1/4" instead of the 1/8". I find it easier to control that way. Single 1/8" is difficult for me to control.....

I do not disagree with you comment, but in my case I find control of cutting thin material is much easier than thicker panels..  That being said, I really much prefer to use 1/8" (or 5/32") thk panels for my flat work images when the cut panel will be attached to a backer.  When thicker material is used the vertical cut edges are more visible and unless the piece is viewed directly head on, the cutting edges seem, IMHO, to detract from the image.  Plaques, signs, etc. often look better when cut in thick materials. 

I never (should say almost never} stack cut as I prefer to treat each piece as an individual work of art and so stipulate that any on my woek that I sell is a one on a kind..  This statement can not be made when stack cutting. 

Since, eventhough I'm old (you could say achient), I have not been at this Scroll Sawing for too long now.  So my ways of doing thingss are from the newer/modern school and thoughts that  I have learned from many, including many old timers like yourself, in this forum.  Much of what I do has come from the school of "learing on the job".   From the beginning I delibertly avoided tutorials or instruction "How to do" videos.  I worked hard to hone my skills to inable me to produce the best work I can.  I stepped out of that perverbial box by adding colorization to much of my work which has proven to be appreciated by many.  I seem to have been rewarded for my efforts by my piers with their very positive acknowlegments of my work and from those who have actually spent significant $$$$ to hang my work in their homes and businesses. 

Just some musing from this OLD newbie!      

 

[Dak0ta52]

Well... I've started a new project and decided to try shelf paper on the back. I'm no where near finished as it is one of Jim Blume's patterns, but my experience so far is that the holes drilled through the frets leave a little dimple. I thought this may be a problem with the project sliding on the table but to the contrary, the plastic film of the shelving liner and the dimples actually allow the project to slid on the table easier than the bare wood. I'm using a WEN saw that doesn't have the arm that lifts so I'm a bottom feeder by necessity, not by choice. Again, I thought the dimples would hinder feeding the blades from the bottom but found I could feel the dimple with my fingers to help guide me to the hole I'm trying to feed the blade. I will say I do use an awl to assure the hole is open and free of any fibers that may block the way. I usually do this after drilling all my holes.

Now, as far as tear-out. Even with some very thin cuts there have been none. I do get some fuzz, especially when the blade starts getting dull, but I'm not sure to what degree because some of the fuzz is adhered to the adhesive on the shelving liner on the bottom of the piece. The piece I'm working with right now is 1/4 Maple ply. Pieces in the past would tear away the bottom layer of veneer at the very least. I know the bottom is usually glued to a backer board but I guess it's just my OCD toying with me. A lot will be determined when the project is finished and I remove the bottom layer of shelving liner.

I'm only able to scroll on weekends because of my job and we are starting to work 6-days a week. So I'll have one day to catch up on honey-dos before I can get back on the saw. I'm about half-way through this project and so far I've worked on it about 4 hours total off and on. I'll definitely give updates as I learn more from this test.

[Jim Blume]

I am interested to see how your experiment works out. Hope it works out for you and am looking forward to seeing your end project.

[Dak0ta52]

So I finished the project and yes, I still had some tear-out but it was minimal. Considering how thin some the cuts were from Jim's pattern, I feel there would have been a bunch more if the shelving liner had not been on the back. There did seem to be more fuzzies but I attribute that to them sticking to the bottom (back) adhesive on the shelving liner, however the fuzzies did appear to be thinner than when not using the shelving liner on the back. I didn't have any problems with shelving liner lifting on the front or the back and the pattern stayed secure throughout the cut.

One thing I consider a huge advantage is being able to bottom feed much easier. As I said in a previous post, the drill leaves a little dimple and you can actually feel this when trying to align the blade with the hole from underneath. For those having a saw where the arm lifts I'm sure this isn't an issue. Unfortunately, the arm on my WEN doesn't lift and you almost have to stand on your head to feed from the bottom. The dimples did not hinder the cutting in any way. Typically I pre-sand both front and back, drill my holes, and then sand again. I also sand throughout the cut. With the shelving liner attached to the back, there was no snagging as I initially expected. I guess I could have sanded the back even with the shelving liner attached but I preferred having the dimples to help locate the holes.

Removing the shelving material from the back was no different than removing it from the front. It just takes a little time and patience. Just don't get in a hurry and pull the fragile areas that might break.

In summery, if you don't mind using the extra shelving liner or blue tape, I feel it would be advantageous in preventing tear-out and reducing the number of chip-outs on the back of your project, especially if there are a lot of frets and thin areas. I will definitely use liner on the back again on pieces with a lot of fret work but not necessarily on simpler projects. Something else I would consider doing would be to stick a patch of shelving liner to the back of areas that have a high risk for tear-out or chipping, but not necessarily cover the entire back of the piece.

I hope my little test helps others. To me, the possibility of saving a project from tear-out or chipping after spending hours and hours cutting is well worth the cost of a little extra shelving liner or tape.