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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?
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.
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.
You probably have a gorillion of these:
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.
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.
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
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.
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.)
