Uneven thicknessing

[Hemsby]

Hi

I recently purchased a Elektra Bekum 260K. The machine is in very good condition but I have a problem when using the thicknesser. It consistently produces a taper of approx .5 m/m taper across a 200 m/m width timber (50m/m thick)

I have fitted new blades and set them from the fixed table using a dial indicator clock, both blades are parallel to the table and with each other to within .05m/m

There seems to be no noticeable independent movement in the 4 table jack threads or the thicknesser table.

Does anyone know if it is possible to to adjust opposite pairs of table threads to rectify this problem or could there be another cause??

Thank you

 

[Jacob]

0.5mm isn't a lot in woodworking terms so just living with it is one option. Or if you want perfection is there somewhere you could pack in some thin shims or something similar?

 

[blackrodd]

I would start with checking the drive chain that moves the thicknesser bed up and down,
If the chain, which is rarely oiled or checked were to be fairly slack through the chain being badly adjusted.
0.5 MM would be only a small amount of "travel". A good indication would be a small amount of play, between the up and down movement, when using the bed wheel.
Get a handbook for you're machine and there will be a maintainance chapter to tell you all you will need to know.
Other wise do as Jacob said, with shims!
HTH Regards Rodders

 

[andypa]

Not sure about this but could uneven feed roller pressure cause this :?: There are 4 bolts/springs that can be adjusted.

 

[SurreyHills]

I have a very old EB p/t of the same model and experienced a similar problem (I caused it trying to take too much off in one pass). The drive chain for my model uses toothed pulleys underneath the table for each of the jack threads. It is possible to remove the retaining bolts and clips that hold the drive chain, but not very easy. Then you can adjust the height of the 4 rods independently. However it is a real pain and would only do this as a last resort.

Have you checked the level of the thicknesser bed to the cutter block? It's difficult to do as the access is restricted. I used a set of digital calipers to the fixed rods that hold the sides of the machines, if this shows the bed to be out of level then try above. Another option is to make a sled that sits along the length of the thicknessing bed and compensates for the uneven table. I made one for thicknessing thinner stock out of mdf with oak ends so that it doesn't get pulled through with the wood (similar to a shooting board).

 

[monkeybiter]

I'm not familiar with the machine but wonder could a bearing be worn at one end of the cutter block allowing it to lift slightly when cutting?

 

[Giff]

might be an obvious question but are the blades set properly ?

 

[Hemsby]

Hi,

Firstly thanks to all for your replies & suggestions.

After checking all the possible causes I did think of screw thread adjustment and looks like Blackrodd & Surreyhills are on the right track.


I have been advised that the independent adjustment of the 4 jacks is something that is quite a common task that needs doing, however not an easy task outside of the factory environment.

It requires the machine placing on its side ( in my case HC260K the case also needs to be removed) then before removing the close toothed chain that drives the sprockets attached to each screwthread marking their relationship of each sprocket tooth & chain. Then removing the chain and making small adjustments to the appropriate screwthread up or down, re attaching the chain getting the machine upright again then making a test cut and repeating the procedure if necessary.

It does seem a lot of work but I am determined to get it correct.

Will be attempting the work next week so will post a update then if I am still sane #-o

Again thank you to all

 

[blackrodd]

DO NOT TAKE THE CHAIN OFF! Can i suggest you get a look at any thicknesser on you tube or whatever that has a similar layout of bed movement and you will soon see that you can either move each threaded adjuster by one tooth of the drive chain, which will be far too much.
The .5 mm difference that you are looking for is more than likely because of a SLACK DRIVE CHAIN, and the chain needs adjusting to the correct working tension that will be hopefully mentioned in the maintainance section of the machine's handbook.
Or just tighten the chain a "Smidge" and check a test piece through the thicknesser.
As you can appreciate the balance or "timing" of two sprockets need only be out a few degrees of thread movement for an in balance and therefor a small difference in TOTAL movement. HTH Regards Rodders

 

[Hemsby]

Hi Rodders.

Thanks for the warning I will just have a look first, to see if and how the chain can be adjusted. I do have the Handbook & Parts book but they are as much use as a Chocolate Tea Pot

I have been a Precision Engineer all my life and find it difficult to cope with small "errors" in anything and need to correct them if at all possible :-k

The machine is otherwise in very good condition which makes this small problem even more annoying.

Again thank you for the info I will have a good look first and let you know ASAP

Regards Keith

 

[blackrodd]

HI Hemsby,
There should be a "jocky" wheel tension arrangement, or a sliding tensioner.
The chain is either bicycle or possibly 3/8 x 5/8 in size, depending on the size of the thicknesser bed
I am confidant that the problem is a very slack chain, in need of adjustment.
A lot of people are not aware that the chain exists! Regards Rodders

 

[Hemsby]

Hi Rodders,

In the parts book it says & shows the chain, description is 210 link 6m/m chain, quite small!! In the exploded part list there does not seem to be any sort of tensioner and no mention of it in the parts description which is a bit suprising.

I hope there is as you say some sort of tensioner. I was going to look at it next week but I am now curious so will try to have a quick look tomorrow.

Thanks again for your trouble.
Regards
Keith

 

[SurreyHills]

As Rodders say there is a tensioner but it will only tighten the chain slightly and may not be enough to sort out your problem. You can easily adjust it. A quick way to check how loose it is is to turn the height adjustment handle and see how much backlash (slack) there is before the bed starts to move.

 

[Racers]

Don't forget that a oiled chain is shorter than a dry one, the thickness of the film of oil multiplied by the number of links in the chain dose add up.
I all always lube my motorbike chain before adjusting it it makes a surprising difference.

Pete

 

[WellsWood]

As Andy has suggested, checking that the cutter block is parallel to the thicknessing table should be your first move. There is a specific order of work to setting a PT, and this is at the top of the list.

Once it is, then the outfeed table you originally set the blades to needs the same treatment. I don't know that machine, but these are commonly adjustable for this exact purpose - either with setscrews or by shimming.

The infeed table can then be checked for parallel to the outfeed table both across its width and longitudinally.

Finally, once it has been confirmed that all the tables are parallel to the cutter block (and therefore, each other) can the knives be set to them rather than the block, (as it now amounts to the same thing) and the only thing to worry about is their height relative to the outfeed table to eliminate snipe and/or bowed cuts.

I may be stating the obvious here (actually almost certainly if your background is precision engineering), but I'd be reluctant to start dismantling the rise and fall mechanism unless as a last resort. Sometimes it's the really obvious aspects of a problem which elude us with the most efficiency.

 

[scholar]

As has been said, you really want to avoid messing with the table rise/fall chain set up - obviously adjustment can be achieved by moving one or more sprockets around, but you might end up making it worse. Unless the chain has come off before, it should have been set up reasonably accurately at the factory and won't need adjusting.

So I would start by checking the chain and sprockets and threaded rise/fall pillars - brush off any crud, lubricate and tension (quite taut); then wind the table up and down a few times to make sure the lube is all run in and everything is moving nicely.

Then I would get two blocks of a very consistent thickness (I have used 25mm mdf, alternatively you may have some metal blocks of a suitable size, just check them all round with a micrometer) and place them on either side under the planer head (the body, not the blades as these will be set later). Wind the table up tight so the blocks (or more likely one of them ) touches the underside of the planer head body. You will see how much adjustment is required to one side or the other (a feeler gauge is useful). You should be able to find a way of adjusting the bearing fixing of that end of the head (may need shims).

Once the planer head is parallel to the thicknessing table, the planing tables can be checked and adjusted as necessary, starting with the fixed rear out feed table - adjust it so it is parallel to the planer head body; then adjust the in feed table, ensuring it is in the same plane (sorry) as the out feed table.

Then adjust the knives' seating as appropriate.

It is worth spending the time to do this once - you will then expect differences of a fraction of 0.5mm, dependent only on the accuracy of your knife setting (which is another specialist subject - best done with two dial indicators....)

Cheers

 

[Hemsby]

Great success :-({|=

I Now have a thicknesses that machines parallel consistently hard or soft wood.

Before contacting the forum I checked all the normal possibilities, bearing play, thread backlash etc also set the blades from the fixed planer table accurately with a dial indicator, after checking the blade block was parallel with the thicknesses table.

However after receiving all the suggestions and warnings about interfering with the table chain I went back through my original checks, only to find that I had been unlucky when checking the planer block against the thicknesses table, there is in fact a small flat area on the blade block at one end which of course is the point I chose, giving me a false reading indicating the table was not parallel to the planer block

Today I managed to get the dial indicator in the thickness area to check the block again which was perfectly parallel with the thicknesses table.

The cause of the problem was with inaccurate machining of the location point on one side of the fixed planer table which meant that the blade setting was correct to the table but not the block, in turn with the thickness table.

I had to insert a 150 m/m long x 1 m/m thick shim under the location point, reset the blades to the table which has corrected the .5 m/m error

As I mentioned previously the machine has had little use and I can only assume that the previous owner was either unaware of the error or had no issue with it.

Thank you all for the assistance ccasion5:

Keith

 

[blackrodd]

I'm pleased that you have re-checked and found that the planer thicknesseris not .5mm "out".
If the flat spot is just before the chip breaker, this could be attributed to sharpening blades in situ, the blade angle and projection being very tight.
For some strange reason I thought that you had measured the work piece produced by the thicknesser, and giving you a measurement discrepency.
Good lesson there, measure the finished work!
Regards Rodders

 

[Hemsby]

Hi Rodders,

Its the way I phrased my last reply. Yes I did measure the timber with a digital vernier and found the .5 m/m Taper, that's where it all started.

In my last post I meant to say that when I first measured the gap from the thicknesser table to the cutter block I thought there was a difference from one end to the other across the cutting width, I now realize (due to the difficulty working under the table) that there was a flat spot on the radius of the cutter block itself at one end so I thought that the thicknesser table was not parallel with the block, then started looking for ways to correct the thicknesser table. But when I checked again today clearly there was not a problem with the thicknesser table.

The problem was the fixed planer table that was out, by putting the 1 m/m packing under one side and re setting the blades to the fixed table it rectified the problem.

To convince myself that all is now well I removed my new 1 m/m shim re set the blades and did some trial cuts and the .5 m/m taper in the timber returned. Then replaced the shim re set the blades again more trial cuts and it is perfectly parallel again.

My conclusion is that either the original machining of the top faces of the machine were incorrect to the axis of the thicknesser mechanism or there was some bad handling during delivery, possibly in transit to me. You may be aware that this machine is basically an Aluminium casting. I could wonder for ever what caused the problem but the main thing is all is well now

Sorry for the confusion

Thanks again for you help.

Regards
Keith

 

[blackrodd]

You're welcome, Like others here, I'm only too pleased to be of some help. Regards Rodders