I am writing this blog article to discuss an issue I have run into with saw blade length. This issue is a moot point for the parallel link saws I have used, as they have a slot the blade goes in and the blade can be moved up and down in the slot. For the Hawk and the Shopsmith, the blade is fully inserted to the bottoms of the blade holders. It appears that the Hegner saws would be impacted as well.
First, a little background to understand why blade length is important. I have used a few different saws through the years. I previously wrote some comparison articles on the different saws. For these comparisons, I cut similar puzzles with no images on each of three different saws. You can see the first article here where I explain the different cutting mechanisms: Scroll Saws (Part 1 – Basic Info).
Follow on articles go into more detail on experiences using the saws. In Scroll Saws (Part 3 – Cutting Comparison), I delve into the blade motion front to back while cutting. I use a little bit of geometry and rough drawings to explain how that blade motion happens and how much motion could be expected. I explained that I felt I had much more control of the cut using the two different parallel arm saws than I did using the parallel link saw.
In Scroll Saws – (Part 4 – blade movement – I only thought I was done), I actually measured the back-and-forth movement of the blade on two of the saws. My calculations in Part 3 were made on an assumption that assumed best case. In Part 4, I look at worst case and discover my Dewalt was not even close to the best case. At this point, I really became interested in making the parallel arm Hawk G426 work for me for puzzle cutting.
In the interim, my DeWalt started having issues, and I replaced it with a new Seyco ST-21. The Seyco also uses the parallel link mechanism. It is indeed adjustable with respect to blade front to back motion, but I was not able to get it down to the best case calculation. Scroll Saws (Part 5 – Seyco ST-21).
The Seyco has some outstanding characteristics, but I still wanted to get the Hawk to work for puzzle cutting so I had more control while cutting detailed pieces. In Blade Kerf Concerns, I resolved my issue of the reverse tooth blades coming through the top of the puzzle image and tearing it. Now I was ready to cut a puzzle with an image on it!
Having bored the readers with a little review, I want to address an issue that came up while using my Hawk to cut the large puzzle in my previous blog post. That issue to me is a matter of quality control on the part of blade manufacturers.
For the constant tension parallel arm scroll saw, it is critical that the length of the saw blade is identical between blades as they get changed out. Look at the simplistic image below.
When you change the blade, the tension is first released with the tension release lever. The blade is changed out with the new blade fully inserted/bottomed out in the blade holders. Then the tension is reapplied with the tension release lever. The resulting tension on the blade should still be the same amount as it was for the last blade. But, if the blade length is different, the tension applied will vary based on the length of that blade. If the blade is longer, the tension will be less and the blade will not cut and track correctly. If it is shorter, the tension will be more and might even be high enough to break the blade when you reapply the tension. If it does not break immediately upon applying tension, it might break in the middle of cutting the second or third piece.
In either case, if the blade length is different, you need to adjust the tension. For the Hawk, adjusting the blade tension requires moving to the back of the saw and messing with the tension adjustment mechanism. You cannot just reach out from the front of the saw and twist a knob. Even if it was a matter of twisting a knob, you still would have a hard time due to the length of the saw arm. You just cannot reach it.
In my case, moving to the back of the saw is neither convenient nor an efficient use of time! It is definitely not something you want to do every time you change out the blade for another of the same size from the same manufacturer. For my last project, I used over 150 saw blades. It is not a small issue.
Which gets me to my gripe! My preferred blade for puzzle cutting is the Pegas MGT 2/0R. Once installed in the saw, it performs the best of any blade I have used for puzzle cutting. However, they are not all the same length in the same batch! Very frustrating! Look at the next couple of pictures. I have some loose blades on a piece of white paper. I used a metal straight edge to align the left side of the blades. Look at the right side!
The next two photos show the effect on blade tension. The first one shows the long blade, the second shows the shorter blade. This is without adjusting the tension, it is just from the difference in blade length.
Here is an image of the chart showing proper tension adjustment by blade size.
I ended up resolving this with a wire cutter. I drew two parallel lines on a piece of paper based on the shortest blade in the pile of blades. Every time I installed a blade, I cut it to length so that I had uniformity in blade length. This worked like a champ, but I don’t think I should have to do it!
I thought perhaps I had a bad batch. This batch was bought April 4, 2024. I had two newer batches, so I checked them as well. Here’s a sample from the batch bought September 9, 2024.
The discrepancy was even higher being 3/32″!
Here’s a batch bought just a couple of months ago.
And what’s with the little nibs on the end of the blades? Some of the nibs are long enough that they are part of the surface area the blade clamp screw engages with. None of the other blades in my possession have those, they are all cut square.
Some other manufacturers seem to be better on uniform blade lengths. Here are some examples.
Even other Pegas blades are better in uniformity and do not have the nibs on the ends.
Some of the others are not uniform in length.
This was never an issue to me before because of the blade clamp mechanism of the parallel link saws. Now it is an issue because I want to take advantage of the better control from the parallel arm saw. It seems like everything is always a compromise. I find the Dewalt blade clamp/tension system the quickest and easiest to use, but the front to back motion of the blade seems excessive as compared to the Hawk.
I have no real solution to this other than to change the blade I use or keep cutting them to length. As I like the way they cut, I will keep cutting them to length when I use this saw.
Hopefully this is interesting to those who read it.
Check out my Etsy store for puzzles for sale. It will be a couple of months before any new ones are posted. I have a back log of custom puzzle orders to get through.
Happy Puzzling!
Bob