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Planer Thicknesser Mod

After struggling to hand plane timber to correct and precise dimensions, we have finally taken the plunge and got a planer thicknesser. The planer part should allow us to make two precise, flat surfaces at an exact angle to each other. And the thicknessing facility should, well, let us work a bunch of wood to a certain thickness.   So one of the latest e-bay adventures is this ‘over and under’ style Kity 439 planer thicknesser.  Like most tools it obviously required a bit of a strip down and rebuild before it’s fully accepted into the workshop.

The first little mods were ones to get it working with the dust sniper’s two vacuum hoses, rather than one big conventional dust or chip extractor hose.

The polycarbonate guard above replaces the overly large and rattly sheet metal dust attachment that comes as standard (see outlined on right).  When in thicknessing mode, when the wood is fed through underneath the main table, this hanging metal bit swings up and onto the planer table and covers (with some annoying gaps) the spinning planer knives and block. The new guard/extractor hood was quickly knocked together with a polycarbonate pint glass, split down the middle and glued together with some hot melt glue. The edges that rest on the table have a rubber (cut from an old inner tube) footing, that provides a nice non-slip seal. The two plug-in attachments are some scrap waste pipe, which has been heat bent at the ends to accept the vacuum hose nicely. It is held in place with a rare earth magnet (left over from some super drill projecting) one side and a little tab that fits under the guide fence the other.

When used in thicknessing mode the new extractor hood works a charm – nothing escapes, and it looks fantastically cool. So yeah, I will have to get a video of it in action at some point, because just watching the chips being flung up and sucked away makes thicknessing wood quite exciting.

Aside from the dust hood, there were a few other problems with it. First, the motor pulley had come loose on its shaft, and was vibrating about a lot – I guess this might be why it was for sale in the first place.  The drive belt is a poly-v type, which is a good choice for this kind of application, but the motor pulley itself is plastic and fairly flimsy :(  A small amount of internet research suggests that it is not that easy to get an off-the-shelf poly-v pulley this small.  So I after fixing that problem with some JB weld, and a new securing bolt and thread, it turns out there is also an overheating issue with the motor.

At the moment this remains unresolved – I can get about fifteen minutes of use out of it before the motor starts complaining and then in short order is shut down by the thermal cut-out (at least that is working and the motor isn’t burnt out). Those fifteen minuets are good, but this is a bit of a problem – ideas welcome ;)

Responses to Planer Thicknesser Mod

  1. Olly Parry-Jones

    Hi Bongo,

    Your new extraction ‘hood’ looks good. Not sure what to suggest on the motor front, though…

    Have you tried running the motor with the belt disconnected? Does it still get warm? I wonder if it’s a case of the tension being too tight, perhaps?

    If the worst comes to it, I can’t imagine a replacement motor would cost as much as £100…

    All the best,


  2. Bongo

    I have tried the motor without the belt, though not for 10 minutes or more (which is about how long it takes), so I should probably try that.

    The belt tension was one of my first thoughts so I have played about with this and it is now only just tight enough to prevent slipping – so I can probably rule that out..

    I suspect it might be the bearings of the cutter block itself being overly stiff. When I spin the cutter block by hand, it comes to rest in under 2 seconds, no matter how hard I spin it. To be honest though I don’t know it that is normal? I am guessing they will be a bit stiffer than your average bearings, because they are (should be) well sealed. Anyone else know how long it should spin before coming to rest?

  3. Bongo

    Ok so tested the motor. Running it, without the belt on for 10-15 minuets makes it too hot to put hands on. And that was with the case off, so it had max ventilation & the fan was whizzing round as well… So that doesn’t seem too good to me. My only thought now is to try replacing the run capacitor.

    I could strip down the motor, but I don’t know of anything particularly ‘serviceable’ inside an induction motor, save for the bearings, and I can see that those are running free and relatively smoothly.

  4. Olly Parry-Jones

    Well, I only know how to make induction motors worse, not fix them… :oops: ;-)

    However, I do know of a man who may be able to help – his name is Bob and his username on the UK woodworking forums is “9fingers”. Not sure whether you’re already a member but, you can find him at both The Wood Haven and UKworkshop.

    It’s definitely worth getting in touch with him for advice – if there’s anything he doesn’t know about these motors then, it’s only the kind of information that isn’t worth knowing! ;-)

    Thinking about it, the motor on my chip extractor (Axminster ADE1200) gets quite warm while it’s running but, I would only say that it is that (warm) and certainly not too hot to handle. No idea how warm the motor on my planer gets as it’s well encased inside the machine.


  5. Bongo

    Thanks for this. I will look Bob up.
    Tried a new capacitor today, and although the motor seems slightly smoother (that might just be in my head), after ten minuets or so it is still getting quite hot – and again that is with no load and maximum ventilation :(

  6. 9fingers

    Hi Bongo,

    Remote de-bugging motors tend to come down to probabilities of possible causes.
    I used to have a Kity combination woodworker and I did find that the motor was not generously designed and could take a long time to start in cold weather and this might have happened in the past to your motor – such are the joys of secondhand purchases.

    Firstly is the time taken to trip the thermal cutout if you just run the motor with the belt off significantly longer than that when driving the machine?

    If not then you can possibly rule out frictional losses in the machine itself.
    to make the measurement reliable I suggest you get the motor from cold to the tripping point first, then make timing measurement to the second and subsequent tripping points with and without the belt on.

    Assuming the problem is in the motor then the most likely fault is either the run winding has a shorted turn or few due to slow start-up internal cooking as mentioned about. Very difficult to test but a rewind shop will have something called a growler which they use to diagnose shorted turns.
    Before needing to use their services, you could try and see if the starting winding is remaining in circuit after initial starting.

    To check for this insert a heavy current mains voltage switch in series with the starting capacitor. If there are two capacitors, the starting one will be the higher value one.
    With the switch closed, start the motor and then open the switch. If the over heat problem goes away then the internal centrifugal switch in the motor has failed shut. The contacts will have welded together. Usually these can be parted and cleaned up with fine emery cloth.

    It is not normally possible to get new switches as by the time these problems start, the motor design has been superseded and spares are unavailable. If the contacts are really knackered, the judicious dismantling of the contacts from a car contact breaker can yield two new contact surfaces and some homemade copper rivets hold them in place.

    Let me know how you get on and give my regards to Olly



  7. Bongo

    Hay Bob,
    Thanks for all the advice. I haven’t actually tried to get the motor to tripping point, with or without the belt attached. Being a bit nervous about the thought of having it go that hot, I hadn’t let that happen again. So it has only happened once, after about 25min light use. Since then I have been nervously checking the temp with my hand – figuring it is ‘overheating’ when I can no longer rest my hand on the motor can for more than a second or two (I am starting to wonder if that is actually too hot or just standard?).

    It doesn’t seem to have a start capacitor, just a run one. Does that make it a Permanent-split capacitor motor by chance or am I missing something?

    I guess I need to get it open and have a look for anything obvious before proceeding? I have a feeling that the pulley-side bearing might be very slightly loose in the motor housing anyway. I am getting a periodic belt flapping vibration every few seconds, that makes me think the bearing might be slowly ‘walking’ round its housing.

    Many thanks,

  8. 9fingers

    Hi Bongo,

    Modern winding wire insulation is capable of running at very high temperatures and so designers seem to interpret that as the motor should get hot. Not unusual to have a motor running at 60 C above ambient these days to that would be a case temperature of 75C at least so too hot to keep your hands on.

    Very surprised that there is no starting capacitor, as a permanent split phase cap motor usually has minimal starting torque. Considering the motor needs to get a belt drive going and a speed up drive to the heavy-ish cutter block.
    Maybe with the extra flexibility of a poly V belt they can get away with it?

    If the bearing is loose then fix it with some gloop asap (quickset epoxy is quite effective if you don’t have the proper stuff) A steel bearing fretting in an aluminium casting will wear away very quickly.

  9. Bongo

    Yeah, I do remember reading that, about the windings heat resistances these days and that motors could run hot, I just didn’t think they would do it without a load attached!

    I hear you about the start-up issue, it does sound particularly strained when it starts (given that it comes up to full speed almost instantly). The belt is currently set quite tight to avoid it slipping lots when the block spins up to speed. It was tighter when I first got it, but I figured that was going to be taking it out of the bearings so…

    Will have a look at that bearing housing today if I get the time.

  10. Paul

    What I’d do is check the current draw and if it was right then it has to be OK right? I suppose you could measure the temperature and have a number as opposed to the more subjective, “it is hot” statement to work with too.

    Then if any of that wasn’t right I’d want to make sure of a few things:
    Is the motor lubricated properly and spinning easily even when it is warmed up?
    Is start winding contacting properly?
    Is the motor wired for the right voltage it is using? (this is usually pretty obvious by how the motor runs)
    Is the motor undervolting because of inadequate supply leads? Sometimes called running a motor brown, or in brownout.
    Is it running on the right frequency?

    Those are all the common motor problems I can think of in the order I’ve encountered them. Well, start switches may be the biggest headaches in induction motors. But don’t overlook running motors under voltage either. Measure the voltage while the motor is running right at the motor. Even a few volts under the motor’s rating can lead to heating.

  11. cop

    hi Bongo
    I also have a kity 439 and I have a little problem with the tension belt 710x6mm.
    Now the belt slips and I don’t know where I adjust the tension of this belt (710x6mm)or if I have to replace it.

  12. Bongo

    Hi there, maybe I will get a chance to strip it down and take some photos for you. From what I remember it is quite easy to adjust the belt tension. Mine needs a bit of a fettle at the moment, I keep using it, but the feed in table needs some adjustment, it’s starting to bind badly.

  13. cop

    Hi Bongo, thank your for your support. I’ve finally solved my headache.

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