Z saw teeth break

[Paul Armes]

Hi.
Twice now when using a Japanese Z saw to cut off protruding dowels, some of the teeth on the saw break off. What is causing this? Glue? (Tite Bond) I am bewildered... Thanks. Paul

[Jim Koepke]

Howdy Paul and Welcome to the posting side of the Creek. I see you have been around quietly for a long time.

I can not tell the exact cause of teeth breaking on pull saws, but it happens to me. It may be because the metal is much thinner than western saws and likely bend first and then get sheered off in the work.

My Japanese type saws still get used occasionally but it isn't likely for me to be buying anymore. Thankfully none of mine have been high priced models. Maybe the expensive ones might fare a little better.

jtk

[Derek Cohen]

I suspect that the most common cause for breaking teeth on Japanese saws is twisting the blade/plate. The plates are very thin and flexible, especially if they do not have a back to stiffen it. The way one saws is responsible, and especially flush cutting would place the teeth at risk.

The correct way (as I know it) to start a cut with a Japanese saw is at the heel of the plate (the section closest to the hands). The saw plate is stiffest in this area, and there is less flex of the plate likely. On the other hand, beginning a cut at the toe, where there is least stiffness/support, will flex the plate and the teeth will bend as well.

It is especially important to make a smooth, flowing movement with these saws. Any jerkiness can translate into twisting, and then the teeth are at risk.

So, start the cut at the heel, and keep it there until there is a decent kerf to support the plate.

I have z-saws in use that are 10 years old and have not lost teeth. That said, if one loses concentration and forgets the rule, it is easy to do worse that lose a tooth or two, and to kink the saw plate. Be dutiful and the saw will last a long time.

Regards from Perth

Derek

[Frederick Skelly]

Welcome Paul!

I've had good results gently pressing down on the saw with one hand while sawing slowly. Doing this keeps the saw flat, which gives it support and results in a better, flusher cut. I start the cut near the heel too. In about 2 years of doing this, I have not bent a saw or broken a tooth. YMMV.

As an aside, I never could get good results doing the thing they show in all the pictures - where the saw is bent 45* to the handle while taking a cut. I gouge the wood and get a crappy cut too.

Fred

[george wilson]

Really,I see no need for those tall,stalky saw teeth,which are excessively easy to break off. But,I am not a devotee of any Japanese tools. Western tools have served me very well all my life. And have done everything I have tried to do.

[Brian Holcombe]

I prefer a hardwood profile for dowels. I hardly ever (never) use softwood dowels, so once I moved to the proper tooth profile I've yet to have tooth breakage issues.

Also, sometimes it's better just to saw them with a dozuki or ryoba and then plane flush. I really only use a flush cut saw on a finished piece of furniture, where I dont want to chance having to plane something flush.

[Malcolm Schweizer]

Good day Paul,

Japanese saws are much more hardened than western saws- so much that the preferred method of sharpening is a diamond file, because they are so hard that a metal file will have difficulty sharpening them. With hardness comes brittleness, and it is not unusual for teeth to sometimes break off. Of course it usually coincides with some operator error, like flexing the saw during cutting, but it happens. The good news is that a Japanese saw still works very well with a few missing teeth, as long as they aren't all in a row.

One thing to consider when cutting with a Japanese saw is to let the saw do the work and don't try to push downwards on it- just use the pulling motion and let the saw work itself through the wood. Trying to force the saw through the wood is a common reason for teeth to break off. That said, it could just happen due to the teeth being brittle, so I am stating it only to give you some ideas of possible reasons for teeth breaking.

[Stanley Covington]

I have broken lots of teeth over the years. In each case, it was my fault for either using the saw wrong, or using it for the wrong application. Z saws are definitely worth owning and worth learning how to use, especially if you value light weight, great cutting speed, and a smooth cut, but don't want to spend time sharpening your saws.

Z saw teeth, at least the ones with induction-hardened ones, are much harder than Western saws, and therefore more brittle. The extra hardness has huge positive benefits, but as with all things, there is no free lunch. They need to be used with a minimum amount of skill and caution. They are not suited for extremely hard wood either.

The tall skinny teeth also offer huge advantages, but as with all things, there is no free lunch. The downside is the teeth are more fragile.

I agree with Derek. You are probably twisting the plate, or at least allowing it to bind. When a sawblade binds, and you don't stop pulling soon enough, a tremendous amount of stress is placed on a few teeth. Sometimes they can't handle the load, and decide to stay behind.

If the saw is binding, please realize that there is either something is wrong with your stroke, or the kerf is closing.

Stan

[Charles Guest]

Hi.
Twice now when using a Japanese Z saw to cut off protruding dowels, some of the teeth on the saw break off. What is causing this? Glue? (Tite Bond) I am bewildered... Thanks. Paul

Will do the job you mentioned with a minimum of fuss and the teeth won't break:

https://www.amazon.com/Crown-187F-Flush-Trim-Saw/dp/B001C009T4

[Jim Koepke]

break off a Western style saw tooth,it is a LOT easier to re file the saw.

The difficulty seems to be doing a good job of it. DAMHIKT! :eek:

jtk

[george wilson]

It would be very difficult indeed,for very nearly anyone to correctly remove all the saw teeth from a Japanese saw,and re file all of them to completely restore a blade. You'd have to be quite expert with a file and very patient to do that job. I could do it,but I am a career experienced craftsman. Much easier for a person to re tooth a Western style saw if needed. At least more people could manage to do that than the number of people who could restore a Japanese saw.

You say that you've had difficulty refiling a Western style saw,Jim? So have quite a few "craftsmen" in Williamsburg. I had to make them send saws back to me for sharpening. Imagine then,the difficulty of restoring the teeth of a Japanese saw.

And,when a Western saw gets too heavy for me to manage,I may as well just check it in and get into lamp shade painting!:)

[Patrick Chase]

Hi.
Twice now when using a Japanese Z saw to cut off protruding dowels, some of the teeth on the saw break off. What is causing this? Glue? (Tite Bond) I am bewildered... Thanks. Paul

Disposable Japanese saws like the Z saw have two features that make them susceptible to tooth breakage, particularly when mishandled.

1. As Jim noted, the sawplate is pretty thin and the teeth are very acutely angled (narrow base relative to the tooth's height), so there just isn't that much cross-sectional area there to withstand the load.

2. The teeth on the disposable ones are impulse-hardened. This helps them stay sharp for a long time (which is why it's done) but it also significantly reduces the toughness of the metal. The higher-end resharpenable Japanese saws are softer and therefore tougher, and don't have this problem to the same degree. Then again they also don't stay sharp as long. As with everything it's a tradeoff.

The bottom line is that any sort of impact or impulsive load is likely to cause breakage with something like a Z-saw. I personally have had good luck with such saws, but I also keep their limitations in mind when I use them. The only time I can recall breaking teeth was when I was using a softwood-optimized saw in a dense hardwood, and hit a knot. Ping!

Are you using a flush-cutting saw with no set to cut your dowels? I can't remember if Z saw makes one, but if you're using a conventional saw with set then that might be part of the problem, if the teeth on the bottom are "digging in".

[Patrick Chase]

I prefer a hardwood profile for dowels. I hardly ever (never) use softwood dowels, so once I moved to the proper tooth profile I've yet to have tooth breakage issues.

This is an important point, that I also alluded to in #16 but probably didn't emphasize enough: More so than Western tools, Japanese saws come in "softwood-optimized" variants. I'll let somebody who knows more than I about Japanese woodworking traditions explain why :-). Those have more vulnerable tooth profiles in my experience, so you (OP) should probably make sure you're not using one of them.

[Stewie Simpson]

Z saw teeth, at least the ones with induction-hardened ones, are much harder than Western saws, and therefore more brittle. The extra hardness has huge positive benefits, but as with all things, there is no free lunch. They need to be used with a minimum amount of skill and caution. They are not suited for extremely hard wood either.

Stanley, your advice to the OP should be helpful.

[Pat Barry]

Hi.
Twice now when using a Japanese Z saw to cut off protruding dowels, some of the teeth on the saw break off. What is causing this? Glue? (Tite Bond) I am bewildered... Thanks. Paul
There are two possible causes. The first is a defective saw. It could have been damaged or may have been hardened incorrectly or the teeth may have been set and reset, etc. The second cause is using the tool improperly. Improper use could include forcing the cut, twisting or bending the teeth, cutting wood that is too hard for the tooth profile coupled with excessive force, etc.

[george wilson]

3 causes,really. The 3rd. is weak saw tooth design.

[Bruce Page]

Folks, I have edited and removed several posts in this thread. I believe the thread contains good information for the OP and anyone else interested in the subject. If you wish to add to the thread please stay on topic and refrain from needless squabbling.

Bruce

[Malcolm McLeod]

I have a Kataba Z-saw (http://www.traditionalwoodworker.com/Kataba-Z-Saw-Heavy-Duty-Carpentry/productinfo/406-15014/), purchased 6 years ago as an experiment to work 10x10 cypress timber. It worked very well and I continue to use it regularly. I work mostly cherry/oak/maple, and don't use a hand saw much, but it has become the first I reach for when the need arises. I just replaced the (disposable) blade, so should be set for another 6 years.

I'm not able to offer any insight on how to avoid broken teeth, because it's never happened to me. I don't typically trim dowels with it, but I suspect anything less than 1/2" is much too narrow for the length and spacing of the teeth. I'd think it would be a bear to start, with such a small bearing area as offered by a dowel...?

Bruce, thanks for cleaning things up.