Shelix mystery

[brian lanning]

Two years ago, before moving to Uruguay, I switched my grizzly jointer over to a Shelix cutter head, made two or three test cuts, then put it in the shipping container. It worked perfectly. For the past two years, I haven't been able to do any woodworking projects. Now i'm getting ready to make kitchen cabinets for the new house, so I'm preparing an area to be a wood shop. I pulled out all the tools, getting them ready. In the process, I looked at the cutter head in the jointer and found somewhat of a disturbing mystery.

16 of the cutters had cracked and fallen apart. When I originally installed it, I took off all the cutters so that I wouldn't damage them during the installation. Then I reinstalled them all using the right torque wrench, then made the three tests cuts I mentioned.

So what happened? I was present for both the loading and unloading of the machine, both uneventful. It wasn't used at all in the two years and no one had access to it. The broken cutters are distributed throughout the circumference of the cutter head. And the guard was in place the whole time. The only thing I can think of is temperature variation. It was winter when I installed the cutters in chicago, and it's summer here now. I remember breaking a couple while installing them before I left. It seems to me like the recommended torque setting (which I can't remember now) was so close to the breaking point of the cutters that I had to turn it down a little. Maybe they moved with heat expansion and cracked?

I believe I have enough inserts to replace the broken ones. But my daughter can bring me more on her way back down in a few weeks.

brian

[Erik Loza]

That seems like the most plausible explanation to me. Possibly the screws stayed torqued at a certain height and the cutterhead expanded, thus putting extra stress on the carbide teeth. I know that those ocean containers can get incredibly hot inside, sitting out on the deck of a cargo ship. Also, carbide is a lot more brittle than steel and possibly the expansion and contraction caused fatigue, which the vibration of transport exacerbated. It might make sense to remove all the teeth and screws if a machine that could be subjected to rapid temperature swings is going to be stored for a while?

Just thinking out loud.

Erik Loza
Minimax USA

[brian lanning]

That seems like the most plausible explanation to me. Possibly the screws stayed torqued at a certain height and the cutterhead expanded, thus putting extra stress on the carbide teeth. I know that those ocean containers can get incredibly hot inside, sitting out on the deck of a cargo ship.

I kind of doubt it was hot inside the container. We brought over things like candles in some of the boxes. Nothing showed even the slightest sign of exposure to heat. They stack those containers 6 or 7 high on the ships. Maybe ours was near the bottom shielded from the heat. Who knows.

But maybe the cutter head or the cutters expanded just from seasonal variation. I think other people would have seen that happen to theirs though.

Also, carbide is a lot more brittle than steel and possibly the expansion and contraction caused fatigue, which the vibration of transport exacerbated. It might make sense to remove all the teeth and screws if a machine that could be subjected to rapid temperature swings is going to be stored for a while?

Just thinking out loud.

Shelix ships these things all over with the cutters installed. So does grizzly for that matter.

Maybe my torque wrench is miscalibrated and I had them too tight so that just a seasonal variation was enough to make the cutters expand and crack?

I have a dewalt planer with those cutters also. Hope they're not broken also.

brian

[Bill A Hagen]

I would say it was a change in temperature. Maybe not extreme high or low, but a significant change in temp over a short time period. The materials of the screw, insert and shaft are all different and they all expand and contract at different rates. The insert is hard but it is also the most brittle, the screw strong (most fasteners with a hex or torx bit head) are made from higher strength materials than most fasteners and the shaft is probably the weakest material.

In a perfect world the fastener should break before the insert or striping the threads. I can only think the inserts broke because the surface they sit on is not perfectly smooth or the fastener didn't seat correctly. In a carbide insert all you need is a high stress point and it will crack. Distribute the load over an area and one of the other parts will fail first.

[John Lanciani]

Did you use a decent torque wrench? 50-55 inch-pounds is the prescribed torque. Ideally you would want to use a torque wrench that puts the desired torque value somewhere between the middle and top end of the range on the instrument for accuracy. I use this one; http://www.amazon.com/Park-Tool-TW-1...+torque+wrench


Alternatively I could see rust growth on the cutter seats creating enough force to ctack the cutters. Any rust present?

[glenn bradley]

+1 on torque. When using something narrow like inch-pounds a questionable wrench can send you way off target. 50-55 inch pounds is what I used (but I have a Grizzly head) and it isn't much. There was a flurry of Byrd threads about breaking inserts but, I believe the consensus was that people were not cleaning things up adequately. IMHO you would be hard pressed to crack an insert at those torque levels if the seat is clean.

[brian lanning]

Did you use a decent torque wrench? 50-55 inch-pounds is the prescribed torque. Ideally you would want to use a torque wrench that puts the desired torque value somewhere between the middle and top end of the range on the instrument for accuracy. I use this one; http://www.amazon.com/Park-Tool-TW-1...+torque+wrench

I used an in-lb click wrench from harbor freight. It seemed to get good reviews before.

Alternatively I could see rust growth on the cutter seats creating enough force to ctack the cutters. Any rust present?

Ah! Humidity and rust are huge problems here. I had a lot of cleanup to do on the various cast iron tops. But the cutter head looked totally rust-free. It might not take much though.

brian

[brian lanning]

+1 on torque. When using something narrow like inch-pounds a questionable wrench can send you way off target. 50-55 inch pounds is what I used and it isn't much. There was a flurry of Byrd threads about breaking inserts but, I believe the consensus was that people were not cleaning things up adequately. IMHO you would be hard pressed to crack an insert at those torque levels if the seat is clean.

It's possible I suppose that I had some sawdust on the seats. I would have had to be really fine dust, like from a sander. But maybe that was it.

[Jim Andrew]

Do you remember what torque setting you used to tighten your cutters? If I recall correctly my instructions were to torque at 40 inch pounds.

[William M Johnson]

A couple of thoughts if you look up the expansion of tungston carbide with tempurature you will find that even for a 100deg swing in tempurature you will not be able to measure the expansion with normal measuring tools (micrometer). I doubt this is the problem.

When I was building my helicopter (Safari Helicopter) I send out all 3 of my torque wrenchs for calibration. Only the Snap On passed. The others were also name brand (not Sears or HF). I was shocked. The Proto I had built many VW/Porsche engines with over the years. When measuring in inch pounds you need a torque wrench marked as such. If you are using a typical 3/8" drive 0 - 75 ft/lb I can guarantee it is not accurate at 4 -5 ft/lb (50 - 55 inch/lb). Don't even consider a 1/2" drive wrench. These wrenches are accurate within the middle 80% of the scale.

I threw them all away, except the snap-on.

Bill

[Ken Fitzgerald]

Until my retirement 3 years ago, I carried a set of calibrated, tested and certified torque wrenches. We were required to have them calibrated and tested annually to a National Bureau of Standards standard.

While it's possible that being over torqued could have caused the problem, I wonder if the vibration of the ship could have added to or caused the problem. I know that while in the Navy, we were told they electronics we worked on was designed to withstand the vibration experienced from the ships movement.

[Myk Rian]

I've had some crack apart not long after replacing them. You MUST make sure everything is clean, and they are seated properly before tightening.
Have your Daughter bring a couple packs of spares over what you need now.

[brian lanning]

Do you remember what torque setting you used to tighten your cutters? If I recall correctly my instructions were to torque at 40 inch pounds.

I don't remember. I looked it up at the time and everyone agreed so that was the number I used. Like I said, it felt too tight because I cracked a couple.

[brian lanning]

I've had some crack apart not long after replacing them. You MUST make sure everything is clean, and they are seated properly before tightening.
Have your Daughter bring a couple packs of spares over what you need now.

I think I have 20 or so now, so I'll have her bring another 20. The inserts aren't available here.

I'm going to have her bring all kinds of things. Shipping things down here directly ranges from expensive to impossible. But bringing things through in the luggage is easy. The problem becomes weight and what the airline charges. To give you an idea, it's far cheaper to buy another piece of luggage and fill it rather than pay to ship something here and deal with customs. Last time I went up there, I brought back an entire kitchenaid mixer for my wife in the luggage.

The crazy freight, customs charges, import duties, and VAT taxes make prices just insane. Festool costs double. I like this store, but the prices are eye-watering. All prices are in US dollars: http://www.todoobra.com.uy/products.php?categoria=38

I'm going to have her bring a moisture meter and metal detector also. Should I have her bring anything else? :-)

brian

[Jim Andrew]

Brian, how were the charges when you brought the shipping container with you?