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The saw disc on my KDR 103 N tablesaw looks like this:

enter image description here

As you can hopefully see, there is a big hexagonal nut. Inside there is an Allen bolt opening.

Inside of this Allen bolt is something surprisingly resembling yet another, smaller, Allen bolt opening.

enter image description here

What is the purpose of this bolt?

I cannot turn the hex nut even when using a lever on the wrench. Likewise, the Allen bolt seems to be at least very hard to unfasten. I haven't used force on it yet.

enter image description here

Furthermore, the Allen bolt is not even in the schematic.

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  • My first thought is that someone replaced the normal nut with that one. I can't think why you would want an allen lock bolt on to threads...
    – bowlturner
    Jul 27, 2022 at 13:38
  • Make and model of saw would be helpful. The only thing I can think of is that you put an Allen key inside the hex head to act as the spindle lock while unscrewing the nut with an open end wrench. However, that seems awkward at best as Allen keys are usually rather short and wouldn't give much leverage.
    – FreeMan
    Jul 27, 2022 at 14:10
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    "I cannot turn the hex nut even when using a lever on the wrench" You know this already, but be careful here. Before you try to just use more force to overcome how strongly it was tightened by the factory installer or previous user (either one of which could easily have been a gorilla who customarily overtightened things!) do apply some penetrating lubricant like WD-40 as it can make a very great difference. And in case it needs to be said: confirm you're turning the nut the right way!
    – Graphus
    Jul 27, 2022 at 16:27
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    I thought this would be as easy as an internet search for instruction manual KDR 103 N. I found some sales info, but no instruction manuals for it. If you got this second hand (or have simply misplaced the manual - no shame in that), try giving them a call or contact them online to ask for a manual. They might just send you one for free.
    – FreeMan
    Jul 28, 2022 at 12:15
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    "held in with a hex nut and Allen bolt?" I think this idea might have distracted us from seeing the problem more clearly. I don't know what we're looking at 'inside' the nut on the end of the arbor but I think we can ignore it and simply go about this as any TS blade-retention nut is loosened. Once the arbor is locked or held firmly, or a wedged piece of wood prevents the blade from moving, it's time to apply increasing amounts of force to the spanner, with gentle mallet or hammer blows to apply some shock force if necessary.
    – Graphus
    Jul 28, 2022 at 19:35

2 Answers 2

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I don't know for certain what you're seeing, so take the first part of this answer as a hypothesis, not as definitive.

First, I don't think there is any hex screw, as such. I think someone has bored out the end of the orginal arbor, and broached a hex recess into it, probably, as suggested by commenter @Freeman, to use as an arbor lock when removing the blade retention nut. I have no idea what the torx shaped recess in the metal at the bottom of the hex recess is about. It's off-center, badly machined, and brazed. Some kind of poorly executed hack related to the hex recess, but I don't know what the intention was.

I am reasonably confident though, that the hex recess is in the actual arbor, and not an extraneous screw, because the the blade flange and retention nut appear to be original, and the arbor would actually extend roughly as far as the picture shows beyond a properly installed blade, flange and nut. Some evidence of the shenanigans the hacker got up to is apparent in the picture. There are horizontal file marks on the arbor end, e.g., and the hex recess shows clear deformation at the corners. One suspects that the process of broaching the recess raised burrs on the arbor end, and the hacker filed them off. A machined shaft end would not contain horizontal machining marks, but, if any, circular concentric marks from facing off on a lathe.

As for removing the blade retention nut, I would take this as a typical frozen nut problem. Your tools for getting it loose are penetrating lubricant, heat, and high-impulse torque (impact, in other words). First, as suggested by @Graphus, do be certain you're loosening in the proper direction (clockwise as you face the arbor end, in the case of your particular saw). Second, immobilize the arbor as firmly as you can (you must already have done this in your attempts to loosen the nut). I would then try impact. If you can get an impact driver on the nut, do that. Otherwise, use a well fitted box-end wrench and a large diameter punch. Put the wrench on the nut, and use a hammer and the punch to apply sharp blows to the wrench 5 or so centimeters from the arbor center. This should release the nut. If it doesn't apply mild heat using a gas torch, as much as possible to the nut only (be sure to thoroughly clean away flammable sawdust and other materials first, of course). Then try the impact again. If still no love, heat again, and apply a penetrating lubricant after heating the nut to the shaft. Wait and try impact again.

If all these methods fail, then I'd get a die grinder (dremel will do fine), and grind a slot in the nut to split it. Open the slot with a cold chisel, but apply the splitting force parallel to the arbor shaft, not perpendicular. You don't want to hose your bearings, or put runout into the arbor.

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  • +1. Can I just check something, don't some saws have nuts that tighten one way and others the opposite way?
    – Graphus
    Jul 28, 2022 at 19:40
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    @Graphus: Yes. But Martin has provided us a picture showing that his saw, like most European Format saws which have the motor and trunions to the right of the blade, spins the blade clockwise as viewed from the free end of the arbor. Thus the blade retention nut loosens clockwise. A typical American left-tilt cabinet saw would be the opposite, as the motor and trunions are left of the blade, and thus the blade spins anti-clockwise as viewed from the arbor end. Jul 28, 2022 at 21:09
  • @Graphus - I must be missing something. How would you change what I wrote to make it more clear? Jul 29, 2022 at 13:36
  • @Graphus I am not in the workshop now, but the manual says that the nut loosens clockwise. Jul 29, 2022 at 16:05
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    Sorry it's me who is missing something. I got so fucussed on the idea of reverse threading I blanked on what that actually meant. *doh* Nothing to see here, move along!
    – Graphus
    Jul 29, 2022 at 18:10
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It turns out the solution was to rotate the Allen bolt in a clockwise direction.

I found the solution by following @WalnutClose's awesome "frozen nut escalation ladder". I got to the point where I tried several different lubricants and the one that did the trick was something that I don't know how to translate. In Slovak it is 'petrolej', which is machine translated to 'coal oil' or 'kerosine'.

When the nut finally gave way, I realized that it has no threads at all and that I just indirectly unfastened the Allen bolt, by unfastening the nut.

enter image description here enter image description here enter image description here

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    So the arbor is drilled and tapped to receive the male thread of the hex screw, and the "nut" is integral to the blade retention flange? If so, WOW. I have never seen such an arrangement on a saw. Aug 2, 2022 at 17:09
  • @WalnutClose, not standard that's for sure!
    – Graphus
    Aug 2, 2022 at 20:07
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    "I got to the point where I tried several different lubricants and the one that did the trick" Er, be careful of ascribing the fix to the last thing used here. You can't discount the effects of anything you used previously (or the combination of them)..... or even the time interval between applying the second-last thing and the final attempt :-)
    – Graphus
    Aug 2, 2022 at 20:12
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    That explains those two holes in the washer. I'll bet the saw originally came with a pin wrench that fit those holes and made it easy to hold the washer steady as you turn the screw.
    – Caleb
    Aug 3, 2022 at 18:46
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    Based on the looks of the hex head in that bolt, I'd seriously contemplate getting a replacement before tightening it back down. Also, some Naval Jelly (the first few results) to clean up the rust on the blade mount would be a good idea, too. Just be sure to push some paper towel down into the blade gap to catch the drips.
    – FreeMan
    Aug 11, 2022 at 18:36

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