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I have a miter saw from the company "Elektra Beckum", which went out of business several years ago. The saw worked flawlessly until my house got flooded last summer. Now I had the time to clean it.

The saw runs again, but it is very loud. I want to have a look inside the motor to see if I can change some bearings. Sadly I have no idea how to open the screws on the motor case. It is like a negative slotted screw. The "ridge" is ~2mm thick and ~3mm high.

Can anyone point me to a tool for that?

enter image description here

enter image description here

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  • I tried some long-nose-pliers but they slip because the screws sit very tight. Other pliers that I tested are to big to reach the screws, because of the sidewalls of the casing.
    – steloe
    Commented Jun 9, 2022 at 13:16
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    An adjustable wrench should work. Of course, if the saw got wet, there might be corrosion issues binding up presumably steel screws in an apparently aluminum casing.
    – Ecnerwal
    Commented Jun 9, 2022 at 13:37
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    Obviously if corrosion is present, a little bit of penetrating oil is prudent.
    – DaveM
    Commented Jun 9, 2022 at 15:28
  • Would the square recess on the end of a socket extender fit over those?
    – donjuedo
    Commented Jun 10, 2022 at 0:43
  • Do you know where it was made? There may be manuals/etc available in a foreign language, always hard to search for.
    – Criggie
    Commented Jun 10, 2022 at 11:08

7 Answers 7

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Get a heavy duty bolt with a slotted head that fits the rectangular projection.

Turn it upside down and put the slot on the stuck bolt.

Then you should be able to get a grip on it it. You may need to screw two nuts tight against each other, on the bolt, so you can turn it with a standard wrench.

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    Or saw/grind/file a suitable slot in one, if one with a suitable slot is not handy.
    – Ecnerwal
    Commented Jun 9, 2022 at 15:16
  • That sounds interesting. I will try and report back!
    – steloe
    Commented Jun 9, 2022 at 18:18
  • Does sound like a good answer that should work, and something that most of us would not think of. Maybe after we spent a few days trying other things.
    – crip659
    Commented Jun 9, 2022 at 19:39
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    If you cut a slot in the threaded end of a hex cap bolt then you'll have a nice hex-to-slot adapter tool. Maybe an M10 or M12 or so would be a good fit. If the torque needed is more than a pair of jammed nuts can sustain, then try this!
    – Greg Hill
    Commented Jun 9, 2022 at 20:42
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    Thanks for your suggestion. After searching high and low I found a bolt that I could use. It worked. The screws are off. Sadly that didn't solve my problem. The head of the casing won't come off.
    – steloe
    Commented Jun 22, 2022 at 16:24
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It almost looks like a T head bolt, but not exactly. Due to irregular size, I would recommend a universal socket; those are the sockets with all the little pins in them that are pushed out of the way to confirm to any shape.

Example of said a universal socket; you would want to get one appropriately sized for your need.

enter image description here

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    @isherwood I was thinking maybe an appropriately sized wing nut socket would work too, but since those are normally hollowed out, I thought it might break the tool. This is the closest tool I could think of that might work. Commented Jun 9, 2022 at 18:42
  • I suppose if you applied this one over to the side it would grab.
    – isherwood
    Commented Jun 9, 2022 at 18:47
  • This looks far too wide to fit in the tight space in the photo. If they make one about half the diameter of that it might work? Commented Jun 10, 2022 at 17:26
  • @DarrelHoffman I wasn't recommending a specific size. The photo was just an example of the product I had suggested in case they were unfamiliar with it. Commented Jun 10, 2022 at 17:41
  • Yeah, just saying, I've seen these before, but I don't know if I've seen one that's much smaller than your example. I suspect it'd be a bit too delicate if scaled down much more than that. Commented Jun 10, 2022 at 19:12
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You probably have a gorillion of these:

enter image description here

The diameter of the bit holder looks very similar to the size of your screw heads. So pick one that lost its magnet, and cut it shorter with the angle grinder. Just remove the hollow part that normally holds the bit, keeping the part that is filled with the hex shank, so you have a flat face into which you can machine a slot with the grinder. This will go on the impact wrench nicely.

Alternate solution:

Get hex bolt.

Cut a slot in the head to match your screws.

Put the bolt into a socket wrench. Measure how much thread you need to cut so that when you put the bolt into the socket with the slotted face coming out, it will be almost flush with the socket, just slightly recessed, so the socket will keep the screw head centered and avoid slipping to the side. The socket shouldn't be too large for this reason.

Thread one or two nuts so the bolt will be centered inside the socket wrench, then cut the thread to length.

You now have a wrench matching your bolts. You can even use it with the impact wrench, if you cut it to the proper length so it will fit in the impact wrench socket.

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  • +1 for "gorrillion" I'm stealing that :)
    – Criggie
    Commented Jun 10, 2022 at 22:59
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I would look at the other end of the motor's housing/case, and see if there's a matching bolt-end with a different fastener. These four bolts look like they are very long and go through the entire motor casing, underneath the radiator fins and probably stop just short of the black-painted metal blade guard. I hope there's four nylock nuts down there, or it might be threaded into the end-plate (which leaves you back to square 1)

There's a chance they're not threaded fasteners either, could be a post that has been peened over by pressure at assembly time to form a one-time "rivet"

Being a motor its a high vibration environment, so if it is threaded there may be threadlocker involved too.

If you can't turn the visible head by pliers and moderate force, stop and look elsewhere before damaging the visible faces.

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    Thanks for your suggestion. The screws are indeed very long. They run all the way along the fins and the screwthread is within a metal plate, just before the blade guard. So I had to access them from the top.
    – steloe
    Commented Jun 22, 2022 at 16:28
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I'd try long reach needle nose vice grip pliers. You can get them 15" long.

https://www.amazon.ca/Titan-60762-Straight-Locking-Pliers/dp/B003YE02V6/ref=asc_df_B003YE02V6

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What about Vise grips? When clamped and tightened with a hex tool, they won’t let go. I got a frozen bolt off of my alternator using a pair, and the bolt was sitting maybe 2 mm proud of the flange surrounding it. I could’ve lifted the engine block out with it, it was on so tight.

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  • Great idea - they seem to be recessed inside the housing, so perhaps the needle-nosed variant might work here.
    – Criggie
    Commented Jun 10, 2022 at 10:59
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Your question states the approximate thickness and height of "ridge" (which I'll term a "tab") of "~2mm thick and ~3mm high". The approximate width is needed for my answer, but only you need to measure it.

I have a medium large set of hex nut drivers with screwdriver handles, which are common tools used in bench electronics disassembly.

So first I'd measure the width of the screw/bolt head's tab (probably termed a "bolt" in motors) with an outside vernier caliper.* Then I'd turn it over, and use the inside vernier caliper to sort through my nut driver socket heads until I found two nut driver sizes that were the closest fits over the inside caliper (as previously set equal to the tab width). Then try both nut drivers on the tab-head, smallest first, and feel if it fits closely (hex corner to opposite hex corner), and then turns.

But warning about what is a coincidental fit. The worse the fit, the less torque you can apply without risk of rounding the tab (bad outcome). Look closely with bright light. If the tool barely starts to turn, but the bolt doesn't, stop, move to the next idea.

This method requires some luck, but at a repair bench (not manufacturing), luck saves time and money.

(*Plastic vernier calipers to use like a ruler are very cheap. Being non-precision, just throw it in the toolbox tray. But it's helpful to pay more for a plastic one that has a measurement lock.)

If this didn't work for me, I'd next try the socket extender idea, if you have one, but only if it fits the inside caliper setting closely.

Next I'd personally try the long-reach needle nose vise grip pliers idea. (Because I own one; I recommend this tool as worth the money.)

To make that work, you probably need to lock-grip the tab-head at an angle to the bolt axis (not straight in-line).

Careful, it's easy to round the tab (or any bolt's shoulder head) with careless use of any vise grips. Again use a bright light and watch closely.

The problem is that you don't know without a torque trial (and having skill with setting the vise grips bite pressure), whether the bolt is rusted in place. (I agree with the pre-oil comment, but just a drop while a paper towel is stuffed near, or the motor may stink if the oil heats up later.)

I can't tell for sure from the photos whether you have access to the tab-head's shoulder, or just the tab?

If you have access to the shoulder, first try to remove the bolt by vise-gripping only the shoulder.

The advantage of this trick is that you can bite deep grooves into the shoulder at an angle for more torque (yes, it's ugly), and hopefully break loose a stuck bolt without damaging the tab for later reassembly using normal tab-head driver torque. If you don't set the vise grips bite exactly right (takes practice), and peel or mangle the shoulder when you turn, you get several more tries and hopefully still haven't damaged the head-tab.

Elektra Beckum Machines (now Metabo) was a German company, so the tab-head driver is surely available as a German/EU tool. But, I don't see it named by casually looking at bolt head charts on the web.

(Sorry, not Stackexchange well-formatted, they won't let me.)

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  • Welcome to the site - that's a fine answer. Not sure what the formatting bit is referring to, text looks fine to me.
    – Criggie
    Commented Jun 10, 2022 at 23:00
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    Thanks. Re formatting: There are several included items that should be Comments, but I don't currently have enough reputation to Comment others. Also, strictly, I might supposed to have posted two answers, but not sure since DIY is a holistic craft where fixes are often tried in a sequence.
    – alstring
    Commented Jun 11, 2022 at 4:10
  • Thanks for pointing out that they now belong to Metabo. I didn't know that. I wrote an email to their support, but haven't heard back from them.
    – steloe
    Commented Jun 22, 2022 at 16:30

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