Lost tooth on new blade

[Scott Haddix]

I purchased my first high-quality TS blade (Forrest WWII) for a table saw I purchased and had run less than 100 linear board feed of material through it prior to this week. This weekend was my first big project on the new saw and I was cutting 4/4 red oak when I got thumped hard on the chest. I couldn't see any obvious issues with the wood or the cut, so I completed the cut, stopped the saw, unplugged it, raised the blade and spun it around and sure enough a tooth was gone, which I then found on the floor.

So, two things - First, I wear glasses so I am never without eye protection, but this highlighted just how important eye protection is. I had a whelp where I got hit in the chest, through my shirt. Had that gone directly into my eye, I suspect they would have had to dig it out.

Second, is this normal? I've relatively new to woodworking (a couple years in), but I've never lost a tooth on any factory blade or on any of the Irwin blades I've used in the past. Should I send the blade to have the tooth replaced, or is it okay to run it this way until it has dulled and needs resharpened?

[Scott Kuykendall]

I would contact Forest about sending it back for a replacement or to have it repaired.
Scott

[Gary Herrmann]

You didn't hit a nail or anything? I'd contact Forrest and see what they say. They're usually pretty good to deal with.

I've sawn through knots with my WWII and haven't lost a tooth, but I've never hit any metal (so far). Hopefully they'll give you an answer you like.

[Matt Meiser]

I've had the edges crumble on a different brand of blade but I've never lost a tooth either. If you are sure you didn't hit anything (remember even good lumber can hide old nails, rocks, etc,) I'd give Forrest a call this morning. If you did hit something, a good sharpener, including Forrest, can replace the tooth and do any other necessary repairs.

[Peter Quinn]

Do not use that blade until it is repaired/replaced.

[CPeter James]

It probably was a bad braze. If only one tooth shows damage, I doubt you hit anything. I have cut a few nails with both Forrest and Ridge blades and did not see any damage to them. I have heard of carbide tools loosing the carbide before, usually router bits.

CPeter

[Scott Haddix]

Yeah, I checked the wood after the cut (since it's next stop was to the router table as well) and there was no metal. The wood was free of knots as well. And it was just this one tooth, the rest of the blade seemed fine.

To know knowledge, in the blades' young life I've never cut through a piece of metal with it. Most of the prior cuts were in plywood, in fact.

And, to be honest, I don't have a high quality spare blade yet (once is already on order), so I used the blade the rest of the weekend and cut a ton more wood with no problems. However, per the advise, I will take it off, and contact Forrest on the best way to get it repaired/replaced.

I'll post the resolution they provide for those of you who are curious.

[Greg Hines, MD]

Certainly Forrest should replace the blade.

Doc

[Tom Walz]

I have been doing failure analyses on saw blades and tools for about 20 years. In an automated manufacturing process it is unusual to have just one braze joint be bad. I would return it to Forrest. In addition a missing tip puts ore strain on the following tips.

If you are really interested I can send you some pdf files. One is Braze Failure Analysis which shows various kinds of braze failure in saw blades and explains why they happened. The other is Building Superior Brazed Tools. We sell them both on cafepress but I do have some free versions.

The info will be on the web shortly but we are rebuilding our web sites so it will be a few days.

Some of the chapters are up at:
http://www.carbideprocessors.com/level3brazetechinfo.htm (http://www.carbideprocessors.com/level3brazetechinfo.htm)

tom

[Ellen Benkin]

No, it's not "usual" and yes, it is very dangerous. Don't use the blade until it is repaired by Forrest. Even if you have to go out and get an emergency spare. Don't use that blade!

[Mike Henderson]

In apologize for the highjack - but I'd like to explore the safety issue.

Why is it dangerous to use a blade with a missing carbide tooth?

Is it because the missing tooth might just be a symptom of bad brazing of all the teeth?

Or that whatever caused the one tooth to come off might have weakened others?

Or does a missing tooth cause a problem for the cut, even if all the other teeth are okay?

Or what?

Thanks to anyone who can answer this.

Mike

[John Thompson]

I would take Tom's advice and return it for new.. not a fix! I wouldn't settle for anything short of that as more brazes on that particular blade may be bad.

I use a cheap Oldham carbide tipped circular saw blade to cut down ore modity shop cabinets on occasion. I have en-counterd and cut through about 6 screws over the years with the $8 Oldham.. and not one missing tooth or even chipped tooth on the blade. I would expect the Forrest to be a touch above Oldham quality.

Get a new Forrest blade that is finished properly and should be at that price.

Sarge..

[Ben Cadotte]

I have never lost a tooth on even my cheap china blades, let alone the good Freuds I have. I think its just a case of the brazing failing. If you have too, go get a so so blade from a borg and send the Forrest back. Don't use it! They will fix it or send you another one. Its not a big deal. The lumber processors do it all the time on their big blades. Most have their own shop where they sharpen and replace carbides.

[Richard Bazemore]

I recently ordered a WWII thru Amazon. I inspected the teeth carefully prior to use after reading about the QC issues with this blade. One tooth was clearly not brazed properly - I could wiggle it with finger pressure. Contacted Forrest directly, they replaced it within 10 days or so. Replacement appears ok.

Forrest should know better.

[glenn bradley]

First, I wear glasses so I am never without eye protection

You mean prescription safety glasses right? Regular glasses frames and lenses are not designed for impact from the front. Just double checking in case you're thinking regular glasses are OK. ;-)

[Chris Barnett]

You could wiggle it with your fingers.:eek: Aside from the extra dollars spent, how could this pass QC? Is their QC adequate? Recently purchased all new Forrest blades and spares; guess I need to take protective film off and do the inspection Forrest should have done. Is their blade just hype? By all means, please post your findings. That blade is going 60 revs per second, very fast. Anyone want to calculate the tangential velocity and kinetic energy? Scary...

[Robert Waddell]

Everyone here is saying it is braising but it might not be. I had a new Freud spit teeth and upon examination it was the carbide breaking. The rear side of the tooth was still braised to the blade. It could be a problem with the binder in the carbide. Look closely at the blade and give Forrest a call.
Rob

[Scott Haddix]

I just checked the blade and there was no portion of the carbide tooth remaining. It appears the braising failed.

I have switched my Irwin blade back onto the saw while I wait for my previously ordered backup blade (which shipped today) to arrive. I appreciate the feedback to stop using the failed blade in the meantime. I sent Forrest an email today but did not get a reply yet. I'll call them tomorrow and get their directions on how to return it for a replacement.

As noted earlier, I was wearing standard glasses at the time, not prescription safety glasses. I have a pair of prescription safety glasses for racquetball that I'll check to see if they offer sufficient protection, and if they don't, I'll get a pair of appropriate glasses. If I need to go that route, does anybody have a recommendation for glass frames suitable to woodworking?

[Gary Keedwell]

About a year ago I lost a tooth on a pratically new Forrest WWll blade. I sent it back and they fixed it but kept sending me a bill for it. After a few calls and alot of weeks gone by the bills finally stopped coming in the mail.:( I have done woodworking for over 20 years and this is the first time I lost a tooth from a table saw blade.
Gary

[Tom Walz]

Mike Henderson,

In 1981 I started working with Weyerhaeuser to prevent tooth loss and breakage. I have been doing it ever since. I have analyzed several hundred blades as well as hundreds of other tools. I have written two papers on the subject called Building Superior Brazed Tools (250 pages) and Braze Failure Analysis (60 pages.)

I will not comment on Forrest but, in my opinion, (notice first amendment protection) there is no reason for a saw tip to come off a saw clean. My company supplies hundreds of saw shops and mills with teeth that do not come off, do not crumble, are extremely hard to shatter and that last 2, 3, 4 times as long as ordinary carbide.

If you have doubts about my experience I will send you free pdf copies of the two books.

Some of this is online at:
http://www.carbideprocessors.com/level3brazetechinfo.htm

They are working on upgrading the website so there are broken links al over but that one works.

Mike, the reasons you gave are all relevant. A missing tooth puts more pressure on the next tooth and that may fail. A missing tooth is a symptom of a serious manufacturing problem, in my opinion.

There are saw manufacturers who never have tip loss and these are people who provide huge saws for extreme cutting.

Tom

[Tom Walz]

Robert Waddell,

In the industry what you describe is generally categorized as heat stress. During brazing steel grows about 2.5 to 3 times as much as carbide. When it cools it pulls on the carbide and causes stress. Think of pent up energy as in a drawn bow. This makes the carbide much easier to break. If there is only carbide at the bottom I would suspect that there were problems with the carbide surface treatment.

The common braze alloy used to be AWS Bag-3 which was 50% with Cadmium. When the government dramatically increased the limits on Cadmium exposure most of the industry went to Bag-24 which was Cadmium free. About 1992 I worked with Weyerhaeuser, SystiMatic and Cascade Southern on this. The Bag-24 was about 40% weaker than Bag-3. We did find a Bag-22 alloy which has Manganese in it that is as good or better for brazing carbide. It is widely used but not by everyone as it requires very good equipment.

Braze joint thickness is incredibly important. To much braze alloy and you have a weak joint. Not enough alloy and you don’t have good impact protection.

During laser cutting the carbon in the steel lattice migrates to the surface and this area needs to be ground back. Some sandblast it which is cheaper and easier but not as certain a process.

Carbide is hard to braze and needs to be surface treated, not just sandblasted.

If the joint between the carbide and the steel is not uniform then the overall joint is weaker and there are gaps where there is no bonding at all.

Older carbide grades, such as C-4, were made to be long wearing and may have had a Transverse Rupture Strength of 300,000 psi. tensile. Modern grades are much longer wearing and tougher with a Transverse Rupture Strength of well over 500,000 psi. tensile.

In the industrial world your carbide rupture problem would be addressed with a tougher grade of carbide and a tougher braze alloy.

I do not know what Freud uses.

Tom

[Scott Haddix]

Well, so far I've left two voice messages and two emails with Customer Service at Forrest, but have gotten no reply to either. I'll obviously keep trying to get in contact with them and keep the group posted on their response once I get to talk to an actual person.

[Jeffrey Makiel]

I was at a Woodworking Show in Edison NJ a few years ago where a person was demonstrating a Forrest blade. He asked the crowd if anyone owns a Forrest blade. A few folks said yes. Then he asked how they liked it. The folks replied postively except for the guy standing next to me that said a tooth came off his blade. The demonstrator did not reply. Perhaps he did not hear the man.

I've been spinning carbide blades ever since they became common and affordable back in the 1970s. They were all consumer grade products from B&D, Oldham, Sears, etc. I've also beat the living heck out of some of them on the jobsite cutting suspect materials. Now in days, I try to buy decent stuff and soley use it in my hobby shop. And, I've never had a tooth fly off the blade. Perhaps I'm lucky. However, I did have a tooth fly out of my mouth which is much worse. :)

I hope Forrest makes everything OK for you. I hear a lot of positive things about them which must have some foundation to it. I hope they aren't becoming a victim offshore competition or the excessive cost of doing business in NJ these days.

-Jeff :)

[Scott Haddix]

I heard back from Forrest today and they have agreed to replace the blade at no charge, which obviously makes me happy.

As a follow-up to an earlier part of this thread, does anybody have a recommendation for prescription glass frames that are ideally suited to woodworking to address the issue with eye protection in the event of a situation like this?

[Mike Henderson]

I heard back from Forrest today and they have agreed to replace the blade at no charge, which obviously makes me happy.

As a follow-up to an earlier part of this thread, does anybody have a recommendation for prescription glass frames that are ideally suited to woodworking to address the issue with eye protection in the event of a situation like this?
I only need help for close vision and found some bifocal safety glasses for $12.50 each. Nothing in the top and you pick your diopter for the bottom. I'll see if I have their URL if that will work for you. But a google for bifocal safety glasses will probably give you the same info.

I bought a couple of pair just to have a backup for when I lose one.

Mike