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LTX repairs


Peter Argyropoulos

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This is about a slightly older Metabo LTX, so newer ones may have undergone some design changes to correct the issues I found.

 

I wasn't able to film it, but I'll give a rundown on this weekends teardown of a LTX drill. My Metabo is a few years old, so once I got the new Fein drill, I've retired the LTX, it's four batteries and two chargers to the garage for "around the house" projects. This last week we had a 60 year-old Chinese tree of some sort removed from our yard which had to be climbed since there's no way to get a bucket to it. Access through the freestanding garage means that it's also not possible to get a stump grinder in there, so we have a massive stump to kill. That's where the Metabo came in.

 

I got my 1-1/2" Milwaukee Selfeed bit out and started drilling 6-inch deep holes into the stump to fill with rock salt to kill it. Despite the low temperature, the gear housing (not the motor) was getting so hot within 4-5 holes that the thermal cutoff kicked in and I couldn't do any more work. The torque control knob was too hot to touch at that point, as well. I let it cool off once and touched up the bit, but the second time around was even worse, with only 3-4 holes getting made. I took the drill down to my workbench to open it up and check it out. Inside, the Metabos are really well made and it shows. There's nothing in there to suggest they're cutting corners. But, like so many German products the devil is in the details when it comes to engineering. The gear housing attaches to the motor with a turn-and-latch setup, so after getting the two apart, you can look into the first layer of planetary gears. They use a black grease, but VERY sparsely, so there was a minimal coating left on that first layer of gears. To get to the next layer of gears, which houses two sets of planetaries for the high/low gears, you have to unscrew four small metric screws (about the size of a #4 screw) which hold a vinyl retaining ring to the back side of the aluminum housing which you see on the front of the drill when it's assembled. Either those screws were overtorqued at the factory or they torqued themselves in under use, but either way, three of the heads snapped off leaving a good 1/2-5/8" of steel screw shaft embedded in the aluminum housing. Fack.

 

So, once the retaining ring was off, I could see into the heart of the gearbox. It looked almost totally dry and barely greased. I'm guessing an engineer determined the ideal, minimum volume of grease to use to keep weight down, etc. and that's all they put in there. The gears were not very well lubricated anymore since there wasn't enough grease to throw back onto them and definitely not enough to transfer heat to the aluminum housing (each of the nine planetary gears has a nylon insert with roller bearings, further reducing the heat transfer to the case). In addition, some of that precious grease had spit out the sides where the speed control lever enters that layer of the gear housing. So I tore it apart completely till I had just the shaft on the back side of the chuck showing, cleaned it out and started filling it with fresh black grease. 

 

Once that was done, I got to the point where I was ready to address those broken off screws. I have a mini drill press, but with the height of the gearbox together with the chuck on it, there's no way I'd be able to get it clamped securely, so I put the gear housing into a 4-inch vice, got as close to center of the broken screws as I could by eye and drilled them out by hand using an M12 drill and three different sized bits. I had to go larger than those metrique screws and the smallest size I have a tap for is 6-32, so that's what she got. Three fresh holes tapped to 6-32 and I left the fourth as it is. The screws also needed to be both shortened and the heads made smaller to fit in the notches on the vinyl retaining ring. Finally I got it all back together. 

 

There were some mishaps along the way, like dropping the gear housing and busting off the torque control knob, but I cobbled a replacement and got that working again. Finally I was ready to go back to that tree stump and start drilling again. 

 

Whereas at the start of this whole mess I was able to drill about 4-5 holes before the temp sensor kicked in and shut the drill down, I was now able to complete the entire job and drilled all the remaining seven holes with just a small increase in temperature of the gearbox. 

 

Lessons learned:

- Greasing gearboxes in power tools is something we often don't do to cordless tools, but it's still an important maintenance procedure to remember.

- Even a good tool may not be set up from the factory for best performance, either through oversight or planned obsolescence.

- Always keep a junky camera on hand so you can take pictures with grease covered hands ;)

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I think someone took a photo of the new Dewalt Brush less high torque impact wrench and the gears had barley any grease on them. I don't know why they are so sparing on the grease in the gear box but it seems to be an issue with a lot of new tools. Old Sill Saw wormdrive saws had a huge reservoir for gear oil built in to the tool. They still even have that on the new ones just not as much capacity as the gears got smaller over the years.

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I know people who have returned new tools as defective because of some grease leaking places on the first couples uses so I can see manufacturers reducing grease to avoid that and accidentally under-greasing on occasion.  Metabo though I would expect to air on the side of overgreasing though since I can't imagine people who buy a metabo tool worrying about some grease oozing out of a new tool.

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