Carter, Iturra, Lenox, Starrett Comparison

[Steve Rowe]

...
I thought I wanted an after market tension gauge until reading and thinking about these threads. I think what too many of us are/were searching for is a more precise, repeatable, and QUICK and EASY way to adjust our bandsaws to some likely totally illusive goal- a number representing the "correct" tension that takes our own abilities out of the equation.

As Mark and others have alluded, in reality there are no precise standard tension- because of differences in blades (steel, size, teeth, etc.), saws, tires, wheels, etc. We are trying to replace experience, knowledge, and, yes, craftsmanship (with all that entails) with a number from a gauge.

...
So, except for Mark and those of you who have weighed in here, who are successfully setting their tension by testing and experimenting (with experience gained over- years?) and getting good cuts, or at least ones that satisfy you, the rest of us need more experience. In my mind, that pretty much negates the need for an after market tension gauge. I still want an easy way to do it that I can trust more than my own craftsmanship if someone can come up with one - it appears no one has figured out how to do that yet.

...

Alan - well said. I have been using bandsaws (3 different ones) for 27 years now and have always used the scale on the saw to set tension. If the setting didn't give an acceptable cut (and this has been rare), all that was ever required was a minor adjustment to the tension. I personally don't see the need for a $150+ gadget to adjust tension to a specific PSI setting as I have yet to purchase a BS blade that even had a recommendation of tension in PSI. I have read on other forums reports of folks snapping their expensive carbide tipped BS blades by using these "accurate" devices making these expensive gadgets even more expensive.
Steve

[lou sansone]

"[quote=Mike Cutler]Using Youngs Modulus value for Carbon Steel, 29,000,000 and trying to achieve 15,000 psi. The amount of strain in inches would be 15,000/29,000,00 or .00051724 in/in.
The value referenced in the Carter Info of 12,500psi would be 12,500/29,000,000 or 0.00043103 in/in.

The variables as I see them are these.

The mechanical tension gages were designed around the particular steel that was in use in steel bands when Starrett first made the device (The Lennox and Ittura are copies o the Starrett). Differing types of steel are going to have different properties and Youngs Modulus values. This would throw the scale readings off. "


My response

I think most steels are close to 29 mega psi and thus have little effect on the reading.

The big sawmill type bandsaws ( two sided blades ) often have hydraulic upper wheel tension mechanisms, which make measuring blade tension a snap. The clamp on Gage will get you close to some supposed value, but what use are they really? If they are not repeatable, then they are not useful at all. An instron would be ideal to test these gadgets. ( maybe someone has already offered to do that ).

lou

[jim gossage]

in response to Mark's plan to do more testing of the gauges, you might ask for advice from the staff at consumer reports. they are extemely experienced in devising jigs and machines to test anything from drill torque to force of car crashes.

[Tom Hamilton]

Facinating discussion, thanks for sharing all this info. And Mark, thanks to you for you first book. Mine is saw-dusty, creased and dog-eared from use in the shop.

And my Duginske set-up Griz 513X performs to my great satisfaction.

Best regards, Tom

[JC Bagley]

I am working with Louis Iturra on resolving and understanding the issues with his gauge and my G0513X. I sent him an email about this thread and suggested he chime in. He replied with:

"Attached to this email is my response to Mark Duginski's article published in Woodworker's Journal Feb. 2007 issue. You may post it online in any internet forum you see fit."

It's a VERY long reply and the SMC server is forcing me to split it up into smaller segments. Here's part one.

===================

01/22/2007

“Letters”
Woodworker’s Journal
4365 Willow Drive
Medina, MN.
55340

Dear Sir,

I read with interest the complimentary issue of your February 2007 magazine and I would like to take this opportunity to respond to the two bandsaw myth busters, Mark Duginski and Aaron Gesicki. But before I do, I would just like to say thank you for the complimentary issue. Your magazine is very informative and gives the home-shop woodworker a new and different perspective to the world of woodworking. I especially appreciate the way your magazine presents difficult and controversial issues that other magazines tend to shy away from. Of particular note, Ron Johnstone’s article on the challenges China’s manufacturing has on domestic sources hits close to home since my company is in the business of manufacturing. I can only say that I understand why most major woodworking manufacturers have moved overseas but I don’t see the war as being already lost. There are still many smaller manufacturers such as my company, Iturra Design, that have been successful due to listening to the voices of the average woodworker and offering innovative products and services that fulfill their needs. It’s only one mans opinion but I believe the larger manufacturers lost out due to their reluctance to change quickly enough. When the Asian invasion first began, larger companies like Delta and Powermatic refused to accept the challenge. They simply refused to improve machine designs which were almost 50 to 60 years old. Since their utility and design patents had expired years ago they had no protection against off-shore manufacturers copying their designs right down to the last nut and bolt. When they finally woke up, they found their foundations severely eroded and in order to save themselves from total collapse they gave in and moved their manufacturing overseas. It’s the same story with our vaporizing automotive industry, domestic manufacturers haven’t moved quickly enough to changing market forces therefore surrendering more and more market share to imports. Confirming my premise is the fact that many of these importers have become domestic manufacturers by opening production plants here on American soil. They’re simply more responsive to the American consumer and what they want. Such is the game of capitalism.

Many experts say we’re simply moving from a manufacturing economy to a service/technology economy. Americans will no longer have to worry about that pesky and dirty business of making things to sell to others, we can simply sell our services and technology to everyone. Frankly, I don’t see it working, most of the high-tech companies are moving manufacturing and R&D overseas and I don’t think selling insurance, flipping hamburgers, or endless telemarketing is good for this country’s economic future. So the way I see it, the fights not over, many small American manufacturers will continue to thrive and prosper. I hate to think about what it will mean for America when that day comes to an end. So please give kudos to Rod Johnstone for a great article that was long overdue.

Before I comment on the article “Blade Tension” let me just point out that I have known Mark Duginski for a number of years and consider him one of my bandsaw mentors. His book, “The Bandsaw Handbook” has been one of the best-selling books written on home-shop bandsaws and I highly recommend it. He has also written several other books and magazine articles on the subject of bandsaws, produced videos and even conducts woodworking classes. As the prior owner of Fasttrak Woodworking, he invented the popular “Cool Blocks” along with other great products designed to make the life of woodworking easier for all of us involved in the field. But unfortunately, after reading his article, “Blade Tension”, there was little I agreed with, which is unusual, because Mark is known for doing his homework. So lets take each of the author’s five questions they chose to answer one by one.


The first, “How accurate are the standard built-in gauges on band saws?” The authors found that the standard tension gauges built into bandsaws are accurate enough to provide proper blade tension readings. I disagree because of the simplistic way they work. In order to build a tension gauge of this type you’re forced to make certain assumptions which may not correspond with reality. First, you must determine a correct blade tension level for all of the wide variety of bandsaw blades being produced today. In this case, Mark and Aaron reported that industry sources for both band saw blades and saws said the optimal value was 15,000psi. Then you must assume that all of the bandsaw blades are going to be of the same thickness because you only want one mark for each blade size. Then you must assume that all the tension springs you install in the band saw will have the exact same spring rate and will never wear out or shorten in length. Then you must assume that the markings you place on the band saws scale will be understandable by the end user. That’s a lot of assumptions! Way too many for my taste, for we all know what can happen when we assume something. So lets take the first of these assumptions, the 15,000psi benchmark for optimal blade tension. This 15,000psi benchmark is not consistent with what we have been told nor what has been published by several blade manufacturers in the past. We’ve been a distributor of Lenox bandsaw blades for many years now and Lenox has always recommended 30,000psi as their ideal tension. Up until just recently they have published this recommendation in their blade catalogs. Also, if one looks closely at the Lenox tension meter pictured on page 66 of the article, you can see that Lenox color codes their gauge indicating their recommendations, green zone starts at 25,000psi and goes up to 32,500psi. Starrett, which has been manufacturing tension meters for several decades, and was one of the four meters tested, provides tension recommendations included in the meter’s instructions for their bandsaw blades. Their recommendations range from 20,000psi for carbon steel blades and up to 35,000psi for bimetal blades. Other sources such as the popular “Timberwolf” blades which are marketed as “low tension blades” do recommend 15,000psi although their main distributor Sulfolk Machinery recommends using a flutter test to set tension. The manufacturer of our “Blade Runner” thin kerf blades recommend 15,000 to 17,000psi as does Highland Hardware’s “Wood Slicer”. Olsen recommends 9000 to 12,000psi for their blades. All of these blade tension recommendations are a bit dated, having been obtained from the manufacturers back in 2000 when we launched the introduction of our own blade tension meter, the Blade Gage which the authors tested in the article. They may have since changed, I called Lenox tech. support and was told that Lenox now recommends 30,000psi when using their blades on a metal-cutting bandsaw and 15,000 to 20,000psi when using a woodcutting bandsaw with the caveat emptor of “if your bandsaw is capable of such tension levels”. As a matter of fairness, I have sent letters to all the current blade manufacturers requesting official clarification on this matter and I’ll publish their responses in our next catalog issue next month. Now remember the authors reported that the saw manufacturers also agreed on this benchmark as well. So refer to an article posted on their website and published in June 2003 by Popular Woodworking magazine titled “Steel-frame Band Saws” written by David Thiel. He quotes Kendall Smith, product manager for band saws at Delta Machinery, “tensioning capacity of the saws also is important, and Delta’s tensioning spring (recently upgraded to a die spring) will tension a ¾” blade to 12,000psi”. Why did he say 12,000psi? According to Mark it should be 15,000psi but one could argue that was in 2003, they may have changed their minds…reconsidered. If so, has Delta once again up-graded their tension springs or re-calibrated their built-in tension gage? I haven’t seen any evidence of this yet in their band saws, if Mark has, please let him point it out to me so I can pass it on to my customers.

Now lets examine the second assumption, for the built-in tension gauge to be accurate, the manufacturer had to assume that all blade thicknesses would be the same. Why? Because listing other blade thicknesses on the gauge would make the scale complicated and hard to read. To be accurate, instead of having just one mark for a ½” blade, you would now need 4 or 5 different markings corresponding to each blade thickness. Blade manufacturers produce ½” blades in .018”,.020”,.022”,.025”, and .035” thicknesses. A .018” thick ½” wide blade would require less force to tension to 15,000psi than a .035” thick ½” wide blade. So they each would require a different marking on the built-in tension gauge of the bandsaw.

The third assumption that all the tension springs would have the same spring rate and wouldn’t wear out or shorten would have to be true if the gauge is to remain accurate. If the bandsaw manufacturers used milled springs it would be an accurate assumption to a degree, but they don’t. A milled spring is cut out by CNC lathes from a solid piece of round bar stock. All current springs used for bandsaws utilize wound springs, which are wound with wire on CNC lathes to form a spring. The best wound springs have a 10 to 15% variance in spring rate and will shorten (more on this later). This variance is for the best-made springs, most manufacturers are using poorer quality springs. The greater spring rate variance there is and any change in spring length due to various factors will degrade the accuracy of the built-in tension gauge.

Continued in another post...

[JC Bagley]

Louis Iturra's reply continues...

============

The last assumption boils down to whether or not the end user understands what the markings on the gauge mean and how to use them. Most manufacturers utilize blade width markings but I have seen some European saws whose scales have no correlation at all to blade width, or use metric scales, leaving the end user in the dark. To conclude, the built-in tension scales used on bandsaws are a low tech. method of determining proper blade tension. Simply put, the manufacturer arbitrarily determined what the tension should be for several different blade sizes and provided marking on a scale for same. This method doesn’t take into account the many different ideal tension levels recommended by different blade manufacturers nor does it take into account the variety of blade thicknesses available for today’s band saw blades nor does it take into account the differences in spring rates from one spring to another nor the different scales used.


Their second question, Are these gauges adequate for the average user? is subjective but is partially answered above. The average user needs and wants a reliable gauge that gives them usable information. Truthfully, I don’t believe these built-in gauges can do that in all cases.


The third question, Is there a problem with the built-in blade tensioning components, as some authors suggest? More specifically, is there a problem with the blade tension spring? Well, back in the year 1999, my company was the first to offer improved tension springs for the Delta and JET 14” bandsaws. We began advocating their use due to some disturbing results we found when testing these bandsaws. With a ½” blade installed, neither machine was capable of properly tensioning the blade to the blade manufacturers recommendations. We published these results in our catalog, listing exactly what tension levels were obtained at each of the blade size markings these machines use for a tension gage. Surprisingly, the maximum tension levels we obtained for a ½” blade at the ½” marking on the saw’s tension gauge was only 5600psi, well below Mark and Aaron’s magical 15,000psi benchmark. But for arguments sake lets assume Mark is correct and all blade and saw manufacturers do indeed agree on 15,000psi as the optimal tension for a bandsaw blade. We have tested many bandsaw springs and have found many unable to obtain 15,000psi for the maximum width blade the manufacturer recommends for their bandsaw. Take the current Delta’s X5 14” bandsaw model 28-475X, since its introduction several years ago it comes equipped with an up-graded spring (die spring) and even with this spring it still can not properly tension a ¾” bandsaw blade to the author’s benchmark 15,000psi. This is why I and many other experts advocate the use of a ½” blade on these smaller bandsaws. Can Mark or Aaron explain why Delta hasn’t up-graded its other current 14” models with this new spring? There are several models which still use the older tension springs such as the 28-206 and 28-276 models made in China or all the previous Delta 14” bandsaws which have been produced by Delta since 1937 when the 14” machine was first introduce. As I’ve stated above, we tested these older springs and have published our results for all our customers to see in everyone of our catalogs since 2000. One of our customers took us to task back in 2001 when he performed his own test on his JET 14”. His results contradicted ours and we were at a loss to explain why his reading were almost twice as much as ours. After he sent us his spring we discovered why. JET had obviously been reading our reviews on this bandsaw and had decided to upgrade their springs! We again published photos showing the upgrade compared to the older OEM spring JET had previously been using and informed customers of the newer (2001 or newer) JET 14” bandsaws not to buy our high tension spring until they experienced problems with the upgraded JET spring. We also have to note here that JET also beefed up their tracking arm to prevent such problems that Mark illustrates is caused by too much tension in the top photo on page 67 of the article. In a nutshell the point is: the bandsaw manufacturers knew their original OEM springs couldn’t obtain the necessary tension levels for the maximum blade width they currently advertise their bandsaws can handle! Also, Mark knew this if he read the many copies of our catalog that have been sent to him and by the many phone conversations we have had on this very subject!

The authors also said, ”Contrary to what you may have read elsewhere, even if the spring is fully compressed, such that the coils are actually touching, the spring will never go bad, get tired, or lose strength. Actually, if the spring provides adequate tension on the first day you use the saw, it will always provide adequate tension.” Those of you that have sleep on an old worn out mattress would probably take exception to this statement, but according to the authors, if I read it correctly, you should never have to replace that spring filled mattress again. I use this example only because my wife and I are currently shopping for a replacement mattress for our girls bedroom. You see, when they were little and had a sleepover with their friends, they used their mattress as a trampoline. Yes, we would tell them not too but you can’t police them every minute. So now as I inspect their mattress, what I see is compressed springs in the middle which don’t spring back to their original length anymore, causing the mattress to sag in the middle. So I had to chuckle just a little when I originally read the author’s statement. But on a more serious note, going back to the JET spring upgrade I mentioned earlier, we tested this spring, measuring its uncompressed length (free length) before and after it was fully compressed (solid height) only once and found the spring had decreased in length by approximately ¼”! This happens when the elastic limit is exceeded and the spring doesn’t return to its original length when the load is released, spring manufacturers call this “Permanent Set”. Now what do you believe will happen in terms of providing accurate readings if this shorten spring is used to determine proper tension levels with the built-in tension scale supplied with the bandsaw? Will it be accurate? I should note here that all the high tension springs we sell for the Delta and JET 14” bandsaws come with a tension chart which we have made up using a tension meter that indicates what tension level is present at the bandsaws tension gauge markings using all the current width blades that can be utilized for that bandsaw (1/16” to ¾”). But these charts are only accurate to 10-15%, since that’s as accurate a spring rate as we can get from one spring to the next without milling the spring from solid instead of coiling (milled springs of the size and spring rate needed would be cost prohibitive). It also doesn’t take into account the shortening of the spring if it exceeds it elastic limits. Even our high quality high tension springs will shorten if fully compressed for an extended period. So why would a woodworker buy one of our high tension springs? Well for the same reason one buys better parts for their auto, to get better performance and reliability from it. Our springs are made from the finest steel, vacuum degassed, valve spring quality chromium vanadium in accordance with ASTM-A232 specifications. The ends are closed during the coiling operation to provide a large bearing surface and finished square by grinding. This allows the spring to stand on their own base and compress evenly under load. The modified trapezoidal cross section changes to a “D” cross section during coiling which significantly lowers maximum stress levels compared to springs using flattened round wire which so many of the bandsaw manufacturers use. Our springs are also subjected to several additional manufacturing steps including heat treating, tempering, shot peening to reduce working stresses, and presetting by compressing to solid for increased set resistance and greater fatigue resistance. Woodworkers buy our springs because they are of higher quality than the OEM springs and in most cases, if properly selected, they will provide them with higher tension levels compared to the OEM springs which will allow them to utilize wider bandsaw blades and/or operate their blades closer to blade manufacturers recommendations (15,000psi ?). This does not mean the woodworker should ever operate their spring at close to full compression. At no time have I ever heard or read any expert advocate fully compressing the tension spring on a bandsaw. The spring must be able to act as a shock absorber as well as providing the necessary tension on a bandsaw. Mark simply needs to tension a ¾” wide blade on the JET 14” bandsaw pictured in the article and tension it to 15,000psi. He would find that the JET spring would be at full or close to full compression, ( the JET 14” bandsaw we tested couldn’t obtain 15,000psi without fully compressing the spring) yet JET documents this machine can handle up to a ¾” blade. If what Mark says is correct about the blade and saw manufacturers believing 15,000psi is the optimal value for bandsaw blades, why can’t the JET bandsaw properly handle the ¾” blade?


The fourth question, Do aftermarket tension gauges provide accurate, useful information that is valuable to band saw users? Mark and Aaron can only recommend the Carter electronic version. This is the only conclusion where I half-way agree with them. I love the Carter tension meter, I wish that the bandsaw manufacturers would incorporate this meter in all the bandsaws they make in the future. It’s great to watch the blade tension while the bandsaw is actually in operation, in many cases you can actually see how blade tension is effected by the blade heating up and expanding. But Carter’s electronic meter doesn’t actually measure blade tension, it simply measures the force directly under the tension rod with a load cell. This eliminates the stick-slip problem (I‘ll explain this later), making the readings extremely linear and repeatable. But there’s several limitations to this meter that Mark and Aaron failed to tell your readers about. First, it can be used only on cast iron 14” bandsaws since it’s specifically designed only for them. This leads to its second limitation, it’s not portable. It can only be used on one bandsaw, unlike the three mechanical versions which can be used on a wide variety of different bandsaws without limitations. The third limitation is the fact that it’s not measuring actual blade stretch or tension, as I said before, its measuring the force under the tension rod only. I discovered this can be a limitation when I was releasing the tension on a Delta 14” bandsaw. After releasing the tension by watching the reading on the electronic display return to zero, I noticed that the blade still had tension on it and couldn’t be removed. After closer inspection I discovered that the bottom of the tracking arm had caught on the opening on the upper wheel guard preventing the sliding bracket from dropping down and releasing the tension on the blade. A fourth limitation is that the electronic display doesn’t read out in psi like the mechanical versions, almost all the blade manufacturers express blade tension in psi requiring the owners of Carter’s electronic tension meter to convert the reading to psi thru manual calculation.

========

Continued in another post...

[JC Bagley]

Louis Iturra's reply continues...

============

I find it difficult to comment on the test results of the mechanical tension meters since neither of the authors describe how they were obtained. They did report that they carefully compressed the spring in measured increments from zero to 15,000psi and back to zero. So I’ll make the assumption they simply counted the number of turns on the tension rod in applying incremental tension on the spring. If this is true, then their results are invalid since they didn’t take into account a phenomena known as stick-slip. This is basically the frictional element between two sliding members, in this case the sliding bracket that contains the tension spring and the ways machined into the upper arm casting of the bandsaw. Stick-slip makes the up and down movement of the sliding bracket nonlinear and probably accounts for the non uniform results obtained in their testing. For example, they may find that 5 complete revolutions of the tension knob may result in 8000psi on the ½” blade but when they attempt to repeat the test they may have to use a total of 5-1/4 complete turns to again obtain 8000psi. Why? Because the friction between the sliding surfaces may change due to the loose tolerances machined in the ways, the sliding bracket may temporarily jam and require more force to move it again. Does this make the mechanical tension meters unless? No, these mechanical tension meters are measuring tension where the rubber meets the road, at the blade. A better test would have been to measure tension with a known quantity of dead weight suspended from a short length of blade attached to a fixed point. This is how we actually calibrate our own tension meter, the Blade Gage. This method eliminates any frictional resistance in the system being tested. Any discrepancies between the three tension meters to each other in their readings may be attributed to improper mounting of the tension meter on the blade. One must ensure that the captured length between the clamping thumbscrews is not curved when comparing the tension meters to each other. If one tension meter captures a straight length of de-tensioned blade and another captures a length with just a small amount of slack in the blade its readings will not be accurate. Also improper handling either during shipment or rough handling in service can adversely affect their calibration. Even the way the tension meter is stored can affect accuracy if corrosion is allowed to develop within the moving parts. This is why we have a policy here at Iturra Design that allows the original owners of our Blade Gage to ship it back to us and for $5 (cost of return shipping) we will check and/or recalibrate the gage (this is a life-time guarantee). These gages are extremely precise instruments measuring blade stretch in 0.0001” graduations which makes them very expensive and delicate. But all of these gauges have distinct advantages over built-in tension gauges, they’re not affected by weak or shorten springs, they’re not affected by differences in blade widths or thicknesses, and they allow the user to adjust the blade to the blade manufacturers ideal tension recommendations. Worldwide, mechanical tension meters have been used successfully for decades in industry, setting up production bandsaws to produce reliable consistent cuts day after day. Almost all bandsaw blade techinians recommend their use.


The last question the authors attempt to answer, What is the most efficient way to properly tension band saw blades? The authors recommend simply using the built-in tension gauge; that you can get top-notch performance right out of the box. In many cases, this may be true, if the user knows what the ideal tension is for the blade they’re using and the bandsaw they purchased can obtain those tension levels and the built-in tension gauge has been calibrated for those tension levels. Lots of “ifs”, and judging from customer feedback and commonly asked questions here at Iturra Design, it’s a subject that sorely needs addressing by your magazine and others. So many subjective methods for properly setting blade tension have been given by so called experts, such as pushing on the side of the blade and looking for ¼” deflection, plucking the blade and listening for a pure musical note and watching for flutter in the blade. All of these methods are just that, subjective, which means it depends on the person performing the test. An example of this would be: I may push on the side of the blade with 5 pounds of pressure to obtain ¼” deflection but you on the other hand may apply 10 pounds of finger pressure. We would both end up with different tension levels on the same blade. In order to be consistent, a bandsaw user must have a measuring device that can obtain accurate and repeatable results. He can only obtain that with a blade tension meter. I often use the analogy of car tires to explain this aspect of bandsaws to woodworkers. If one purchased new tires for their car and the tire manufacturer recommends 32psi for maximum performance and life, how would one know when the tires were properly inflated? Simple, they would use a tire pressure gauge because they’re readily available and inexpensive. But years ago, before they became commonplace, people would simply kick the tires to check for proper inflation. Was this an accurate method? No. Did users get maximum life and performance from their tires? Probably not. But someone somewhere saw a need for an accurate way to measure tire pressure and the tire pressure gauge was born. We are slowly approaching the same period with blade tension meters, very few woodworkers have used them since their cost has been extremely expensive. Here at Iturra Design we saw a need for an inexpensive tension meter, a tension meter any woodworker could afford and introduced the Blade Gage which sells for $150, which is half the cost of what was currently on the market. We still believe that this is still too expensive and are currently working on a second version which hopefully will retail for half the cost of our Blade Gage. So the real question one needs to ask themselves when properly tensioning their bandsaw blades is this. Do I want to be a tire kicker or do I utilize tools and components which enables me to obtain accurate blade manufacturers tension levels? Thus achieving optimal performance and longevity from their bandsaw blades.

The authors attempted to answer five questions and in every instance drew questionable conclusions. The authors blame over-tensioning as the cause of component failure and provide photos of broken components attributed to over tensioning. They don’t recommend high tension springs believing the OEM springs are adequate. Truth is, many of these components are substandard even if you believe in Mark’s benchmark optimal blade tension of 15,000psi. Fact is, some manufacturers such as JET beefed up their tracking arms when they up-graded their tension springs several years ago because of component failure in this area. But buyer beware, because many manufacturers haven’t followed suit. So is it wrong to offer customers improved and stronger made parts to replace OEM components that constantly fail, I think not! Is there a problem with the OEM tension springs? In most cases the answer is uncertain without actually testing the bandsaw with the widest blade recommended by its manufacturer with a tension meter. In the case of the JET 14” bandsaw pictured in the article, even the improved OEM spring is incapable of providing Mark’s 15,000psi to the maximum width blade(¾”) JET claims it can handle!

The authors state,” So there you have it. We’ve found no good technical reasons for over tensioning. We suspect it has more to do with compensating for other tune-up issues rather than blade tension system deficiencies.” Mark and Aaron, no one has ever recommended over tensioning! We simply believe that if a woodworker purchases a bandsaw whose manufacturer claims can use a certain maximum width blade, then that bandsaw should properly tension that blade. If you want to agree on a benchmark of 15,000psi then that bandsaw should be able to apply 15,000psi to that blade width. If it doesn’t, don’t blame us for selling the woodworker a spring that can or selling improved components that won’t break. Instead of myth-busting, experts such as yourselves should be advocating that blade manufacturers disclose on the packaging what they consider to be optimal blade tension for their blades. Have saw manufacturers disclose what ideal or average tension level was used to calibrate their built-in tension gauges. Also have saw manufacturers disclose what tension level was used to determine the maximum width blade recommended for the bandsaw.


Unfortunately, in this day and age, disinformation is everywhere, which is why we publish our catalog with information we believe to be true and correct. At anytime, anyone can take us to task on the validity of this information and if we believe it furthers the efforts of providing a better understanding of bandsaws we’ll publish their arguments. This provides a forum to our customers so they can decide for themselves which is the better course of action to improve bandsaw performance. A healthy suspicion of popular opinion is a valuable intellectual quality but one has to closely examine the rational for that popular opinion. Weigh the reasons it came about and then make an appropriate choice, for no one likes living in a fools paradise.

I sincerely hope that Mark and his friend reconsider their conclusions on blade tension.

Sincerely,
Louis A. Iturra

[lou sansone]

long article by Mr iturra. I still don't see anyone providing a sound engineering reason for the 15000 psi value, except my attempt in a few posts back. What good does it do to spend several pages saying that any meter can read the magic 15kpsi value, when the value is really the question in the first place.

still wondering

lou

[Dennis McDonaugh]

I think everyone with a dog in this fight has his own fish to fry. How's that for mixing metaphors? They are all salesmen whether they are selling books or bandsaw springs. In the end you have to evaluate the claims and make your decision on who to believe. I tuned Mr. Duginski out when he called Louis Iturra a self promoter. How many times has Mr. Duginski mentioned his new book in these threads? I find it pretty convenient that he mentioned several times how he hates to visit these forums yet here he is. Kinda like watching the movie stars make the rounds with Jay Leno and Lettermen when they have a new movie coming out. Having to retract statments made as fact just reinforced my opinion. But then again, maybe I've become too cynical.

[Jim Dailey]

Dennis,

I think you are making a personal attack. If I an reading this wrong... my apology.

I had the opportunity to have lunch last week with Mark Duganiske. He was very down to earth. I did also have a chance to look very briefly at his new unpublished book. His updated book appeared to be very well polished, incredible graphics and much more substantial then his previous book on bandsaws.

I have also on several occasion spoke to Louis Iturra over the phone. And have purchased a number of items from him it the past, and will both purchase & recommend him in the future.

I have gained insights from many sources... experts, tradesman & novices.... no one has a monopoly on good ideas.

Personal attacks however are not appropriate. Please keep an open mind.

Again if I an reading this wrong... my apology.

jim

[Dennis McDonaugh]

Dennis,

I think you are making a personal attack. If I an reading this wrong... my apology.

I had the opportunity to have lunch last week with Mark Duganiske. He was very down to earth. I did also have a chance to look very briefly at his new unpublished book. His updated book appeared to be very well polished, incredible graphics and much more substantial then his previous book on bandsaws.

I have also on several occasion spoke to Louis Iturra over the phone. And have purchased a number of items from him it the past, and will both purchase & recommend him in the future.

I have gained insights from many sources... experts, tradesman & novices.... no one has a monopoly on good ideas.

Personal attacks however are not appropriate. Please keep an open mind.

Again if I an reading this wrong... my apology.

jim

Apology accepted Jim. I am merely pointing out what went on earlier in this thread and made an observation. I didn't accuse anyone of anything. I have his book and use it regularly. I also buy from Louis Iturra. PM me if you'd like to discuss it off line.

[lou sansone]

long article by Mr iturra. I still don't see anyone providing a sound engineering reason for the 15000 psi value, except my attempt in a few posts back. What good does it do to spend several pages saying that any meter can read the magic 15kpsi value, when the value is really the question in the first place.

still wondering

lou

Still wondering .... are there any engineers out there ?

[Dick Sylvan]

Mark,
Since we met in Sacramento I have been looking for your book, but it doesn't seem to be out yet. Do you have any more details?

[Tom Hamilton]

Hi Dick: The book vendor we use at our Church Bookstore shows that Mark's new book is due in May 07.


The New Complete Guide to the Band Saw: Everything You Need to Know about the Most Important Saw in the Shop
Contributor(s): Duginske, Mark (Author) ISBN: 1565233182 EAN: 9781565233188 Publisher: Fox Chapel Publishing Company US SRP: $ 19.95 US - (Discount: REG) Binding: Paperback Pub Date: May 2007 Publisher Marketing: This essential guide to woodworking's most versatile tool includes a thorough analysis on everything needed to know in order to purchase, setup, use, and maintain a band saw. This book details what woodworkers need to know before purchasing a saw--including the eight questions to ask before buying a used saw--along with topics such as a part-by-part overview of every component of the saw, techniques of set-up and alignment, choosing the right blade, and understanding hand positioning to provide any woodworker with the most complete guide to a band saw. Special sections are devoted to band saw accessories, how to deal with common problems, and how to maintain a band saw to keep it running effectively and efficiently for years.Should be in the stores fairly soon.

Best regards, Tom, in Houston, with a copy on order!

[Dave MacArthur]

Good information in this thread, and good discussion. After reading all the information, I strongly feel that Mr. Iturra's response has been the most logical, well reasoned, and scientifically sound. I was very impressed with the obvious research and thought he has put into the subject. As someone with a master's degree myself in probablility and statistics, and a good bit of study in test design and data analysis, I must say that his conclusions ring true to me, and I was quite pleased to see previous descriptions of him as engaging, articulate, and caring borne out by his thoughtful response.

Can't say when I've enjoyed reading an internet thread so much, and I am also impressed with the maturity and respect demonstrated by the forum readers here!