Ever cut leather on a scroll saw?

[Douglaslais]

I recently purchased a scroll saw to do production cutting on very thick leather, about 3/16" to 1/4". I have a small craft business, making leather helmets and selling them at Renaissance Festivals. It's all I use the saw for, so I purchased an inexpensive Wilton. I use pinned blades, with the coarsest teeth I could find. I was doing fine for a month, but now I've been breaking a blade every few minutes. They break about a half inch from the top, and sometimes just break when I'm pausing for a moment. I've tried different tensions, but I'm down to feeding at about an inch per minute. The leather texture is firm, about like soft wood, but is more flexible. I use the guard to hold it down, or it would be bouncing badly. A couple days ago I did make a few improvements in my second tabletop, which sets on top of the saw table, and is large enough to support a 24" long piece of leather. It has legs on the ends, and is velcroed down to the saw table to prevent it's shifting and bumping into the blade. That's when the blades started to break. So, any ideas? Thanks, Doug

[CanadianScroller]

Ideas are all I have, some of them are good, and some are bad.

I like the idea of the auxiliary table. I presume the function is to support a larger piece of leather while you cut.
If the blades were not breaking before you attached the second tabletop to the first you may want to leave the top of the table free.
Cutting a hole in the board and having the table sit inside the hole
That way you get the support of the table but the blade wont brush against it.

I am not sure if I would go for the coarsest blade, I would experiment with any blades you can get. You will find with finer blades the leather wont bounce as much. There is nothing wrong with pinned blades for this application.
You may try stacking several pieces of leather together sandwiched between two thin pieces of ply.

Once you have cut the first batch out you can use the top piece of plywood as a template. Even that alone should stop the leather from bouncing.

[B Smith]

You may want to contact Mike. Private Message me for his website address. He may have some advice as to what you can do.Another one who might be able to helphttp://www.scrollsaws.com/.
Hope this helps.

[SharonW0111]

It seems to me that there is something on your table top that is causeing your blade to overheat and break. I could be wrong but that is what comes to mind.I'd try a smaller blade also
Sharon

[GrayBeard Phil]

Doug:

Advise above is good. However, I am going another direction, which may not be your problem at all.

From my experience, when a blade breaks very near the top or bottom blade chuck, the problem is blade slippage in the blade chuck. Sometimes the slippage is in the opposite chuck than the one near the breakage.

There are two major causes of slippage: oil on the blade ends, and blade chuck clamping error. About a dozen rare and unusual causes of blade chuck slippage which we won't go into.

Suggestions:
1 - Clean both chucks as best you can, however you can. A broken piece from a while ago could be wedged in there giving you a false clamping pressure.

2 - Examine your chucks, however you can, and compare top and bottom looking for wear, gouges, anything that jumps out at you as being not the same. (Scroll Saw chucks do wear out and have to be replaced.)

3 - Before mounting your next blade, get a small jar (like baby food jar) filled with Paint Thinner. Dip both ends in paint thinner, and wipe clean. If you don't want the smell of paint thinner, use Wet / Dry sandpaper from your local consumer Automotive parts store; Sand the ends of the Blades to remove the oil.

4 - Mount a blade, turn saw on with your table tops off. Don't cut anything, just let it run. Time how long the blade lasts. If it lasts at least 10 minutes then it should be OK. No need to let the test run more than 15 minutes. If your blade breaks in less than 10 minutes, post back as you have a mechanical problem.

5 - Repeat the run time test, but with the table tops installed. Remimber, don't cut anything, just let the saw run at your normal up/down speed you use.

Phil

PS: again, the advise above is good and my suggestions may have nothing to do with your problem.

[millwab]

Phil,

From my experience, when a blade breaks very near the top or bottom blade chuck, the problem is blade slippage in the blade chuck.

Would he have this problem with pinned blades?

Bruce

[GrayBeard Phil]

Bruce:

In response to your question: I don't know. I have no idea what the tension mechanism is, nor how it works. But the blade chuck must somehow grab the blade and apply tension. Pinned on not. The breakage near the chuck is many, so-o many times caused by the gradual loss of tension of the blade. What is allowing the blade to gradually lose tension, I don't know.

As the blade cycles thru the up / down motion, the upper and lower arms / chucks can never be perfectly synchronized because this is the real world and the motor is only attached to one arm. {insert heavy engineering math here} As the saw runs, normally there will be an insignificant change in blade tension as the blade changes from up-stroke to down-stroke and vice versa

However, if blade tension is gradually lost, then the lack of synchronization may cause the blade to cycle in and out of tension, flexing the blade at one end of the blade. Flexing of scroll saw blades will cause failure of the metal. {the metal is in tension and is made to be in tension. The blades will fail if you attempt compression.}

Again, I don't know if this is the problem, as I mentioned in my post.

Phil

[CanadianScroller]

Your post makes lots of sense Phil, it reminds me of the Tacoma Narrows Bridge,
Galloping Gertie.


Vibration is literally our double edge sword. We need it in order to produce the cutting action of the blade but me must control it or the result will be failure in one of the components.

[Douglaslais]

Thanks for the help

Thanks for the great replies, people. I did get some finer blades, and it has helped much. I've cut leather with my homemede tabletop removed, and installed, and it works both ways now. But I do think there's a chuck problem. My lower chuck is difficult to get tight enough, and a couple of times the blade has just fallen out of it when I loosen the upper chuck. Today's project. Love the video clip of the bridge!
Doug

[Douglaslais]

It was the chuck

Thanks Phil,
There WAS a problem with the lower chuck. When the chuck assembly was screwed onto the saw it actually prevented the jaws that hold the blade from tightening all the way. No flex. I just reattached the assembly with the jaws already snugged together, so now they loosen and tighten enough to both hold and release the blade. It also passed the 5 minute function test. Looks like Leatherhelms is back in production.
Doug

[SharonW0111]

Doug- not know what type of clamp you have may I add another nickels worth? I have a screw that sets my blades and they tend to get burs on them and that will keep them from tighting up on a blade- the solution is simple- just swipe it across sand paper until smooth and it will fit that problem-also if you have a saw like mine with a hex screw on one side and a setting screw on the other make sure your hex screw is set flush with the holder- I had heck keeping my blades in until i loosened the hex screw to set flat--hench fixed that problem too.
Good luck on the helmets and please post a picture -- I for one would like to see them
Sharon

[Douglaslais]

Sharon,
I'll try to attach a couple of pictures. Hrer goes...If you don't get 'em, I can't figure it out. Doug

[CanadianScroller]

Thats awesome. You should get Bob to put them in the alternate materials section.

I would sure like to get a pattern of that My son makes chain mail. It would be a great gift for him.