Thicknesser accuracy??? - Now with Pics

[TrimTheKing]

Hi all

I have had a long standing bugbear with my PT (Axminster 106PT2) in that I was sure it was thicknessing in a wedge (thicker on one side than the other across the table width). I got 20 mins to test it this evening and wanted to see if I am being too picky or if there is something I can do to rectify it.

Here's my quandary, I took a 2' long lump of 40mm beech and:

- Planed it flat (I have already taken time to set up the tables to make sure they are flat/coplanar etc).

- Next I flipped to thicknesser mode and ran it through until it got rid of the small amount of concavity.

- Next I get out the digi caliper to check, and here's what I found...

Imagine the board is fed through and you are looking at it from behind as it is going through, the corner you can see on the left is corner A, the corner in front (along the long edge) is corner B, the corner closest on the right is corner C and in front of that corner D.

My measurements were as follows:

A = 1.500" (38.10mm)
B = 1.493" (38.03mm)
C = 1.479" (37.58mm)
D = 1.482" (37.65mm)

So it looks like it is around 0.5mm out (thicknessing thinner on the right side of the table). My questions are:

- Is this acceptable to you out there?
- Can I fix it? (I think the blades must be out by half a mil on that side of the table, or can the thicknessing bed be moved?)
- Am I being an pineapple and this is perfectly normal and acceptable???

Cheers

Mark

 

[MikeG.]

So it looks like it is around 0.5mm out (thicknessing thinner on the right side of the table). My questions are:

- Is this acceptable to you out there?
- Can I fix it? (I think the blades must be out by half a mil on that side of the table, or can the thicknessing bed be moved?)
- Am I being an pineapple and this is perfectly normal and acceptable???

Mark

No, that is not acceptable (IMO). Have you any way of checking whether the surface of the planer bed is parallel with the thicknesser bed. You might have to make something up with a straight edge.

My thinking is that if you have set the blades of the planer correctly, they will follow the line of the planer table. If they are then producing a slpoed cut in the board below, the the two tables can't be parallel.

What the hell you do about I have no idea, but at least knowing the problem gives you a place to start thinking.

Mike

 

[Steve Maskery]

If, by 40mm, you mean the width of the workpiece, then that is absolutely awful. If 40mm is the thickness, however, how wide is the workpiece? Being out by 0.5mm over 250mm, for example, is not as bad as being out by 0.5mm over 40mm.

Assuming that your knives are set level in the block and level with the planing tables, then the problem must be with the thicknessing table. I don't know the rise & fall mechanism on that one, but my Kity has 4 leadscrews operated by a chain. The only way to adjust them, AFIK, is to unlink the chain, rotate the offending leadscrew by one or more teeth and relinking the chain. I've never done it myself.

HTH
S

 

[RobertMP]

My metabo 260 was doing the wedge thing on thicknessing by about .25mm.

When I turned the blades over I set them using a vernier to jig them off of the cutter block as a reference rather than the outfeed surface and dragging a rule. Result was the thicknessing is now near enough parallel. The Outfeed table was now dragging the ruler on the blade more on one side than the other... so I put a very thin shim under the mounting for the table one side.

Odd thing is I can't detect any difference in outfeed table height to the infeed table side to side - so either that was out in the first instance or it does not matter. Anyway all working correctly now.

 

[crazylilting]

I would suspect that the blades are set to the table and not the planer head. Set the blades parallel with the head and adjust the table to the blades afterward.

But before you do that measure the head to the lower table first to see if there is an issue with it being out. If it is out check to see if there is any play in the bearings in the head. Can you move the head even the tiniest bit?

It will take some time to go through it. But start from the bottom up. Not the top down.

 

[ondablade]

That looks to be a long way out Mark. The thicknesser on the Robland X260 i sold recently (a capable, but by no means a high end machine) was accurate on thickness across a 5 inch or so board to well within 0.1mm or better, and maintained this thickness setting over a run of several 3 - 4 m lengths.

I'm no expert on set up either, but i seem to recall that the starting point is to get thicknesser lifting table set up parallel to the axis of the planer cutter block/cylinder. (i.e. the surface of the solid metal cylinder with stub shafts at each end that the planer knives are mounted in)

That means finding a way to measure the height from the thicknesser table to the drum surface - maybe use a dial gauge mounted on a magnetic stand, and check the table lift for wobble by levering it side to side with a length of timber. (if it's got a significant amount of slop it's not going to cut consistently parallel sides no matter how much you adjust it)

It depends on the machine how to fix this if it's out, but on the Robland i think you were supposed to shim the cutter bearing blocks.

Once that's OK it's down to getting the knives set up parallel lengthwise to the cylinder, projecting equally above the drum, and finally the infeed and the outfeed tables levelled and at the correct heights relative to this.

I've had good luck setting sprung knives off the out feed table using a sheet of plate glass, but that's really only an option if you know that the cylinder is parallel to the thicknessing table, and the outfeed table parallel to that.

Don't forget to test afterwards that the jointer is producing straight edges - if the out feed table height relative to the knife height isn't quite right it won't give straight edges - depending on which way it's wrong it'll produce a slightly concave or convex (lengthwise) edges. The fix is to tweak the out feed table height.

Here's a couple of pretty decent looking Fine Woodworking video links on knife setting that a quick search brought up:

http://video.google.com/videoplay?docid ... 960322121#

http://video.google.com/videoplay?docid ... ghn&hl=en#

 

[Anonymous]

This is exactly what I was trying to explain in the previous thread,
https://www.ukworkshop.co.uk/forums/view ... hp?t=35937

Koolwabbit

 

[TrimTheKing]

If, by 40mm, you mean the width of the workpiece, then that is absolutely awful. If 40mm is the thickness, however, how wide is the workpiece? Being out by 0.5mm over 250mm, for example, is not as bad as being out by 0.5mm over 40mm.

Assuming that your knives are set level in the block and level with the planing tables, then the problem must be with the thicknessing table. I don't know the rise & fall mechanism on that one, but my Kity has 4 leadscrews operated by a chain. The only way to adjust them, AFIK, is to unlink the chain, rotate the offending leadscrew by one or more teeth and relinking the chain. I've never done it myself.

HTH
S

Steve

The planer is a 10" model, the wood was 40mm thick and about 240mm wide, so the slop is over the full width of the block.

Thanks everyone, I will work something out to check the block/table parallel status then take it from there with all other suggestion.

Thanks for the help, it's much appreciated.

Cheers

Mark

 

[ProShop]

An easy way to check the alignment of the thicknesser table in relation to the cutter block (not the knives) is wind up the thicknesser table to the block and use your calipers to check the gap at each side of the table & block(width) and see if there is any discrepancy. If not you'll know the thicknesser table is correct. So then you can check the aligment of the knives in relation to the block. Once both of these are correct you can then check the planer tables.


hope this helps.

 

[OPJ]

Mark, you're not the only one with this problem. I've never bothered to measure it in the way you clearly have but, for as long as I've had this machine (two-years, now), I've suspected that the cutter block and thicknessing bed are not parallel to one-another. :? I find that, when I'm doing a table top, I will set the boards out before cutting biscuit slots and can feel the minor discrepancy in the thickness of two mating boards.

As far as I know, the thicknessing bed isn't easily adjustable as it only rises and falls on a single, central column (some of the clones - Charnwood, I think - have four additional columns...).

I now understand what koolwabbit meant in the other thread and how using the supplied jig to set the knives parallel to the cutter block will yield inaccurate results, in this situation.

Steve's method may be worth a look... Otherwise, it may be possible to adjust the cutter block? I know you can fiddle with the tension on the feed rollers.

If you do attempt to fix this then, I'd be very interested to hear how you get on. I still prefer to use the supplied jig (even though it's lightweight and it takes me several attempts before I get it right... :roll as I just cannot get along with the magnetic Dakota jigs! :x

 

[TrimTheKing]

An easy way to check the alignment of the thicknesser table in relation to the cutter block (not the knives) is wind up the thicknesser table to the block and use your calipers to check the gap at each side of the table & block(width) and see if there is any discrepancy. If not you'll know the thicknesser table is correct. So then you can check the aligment of the knives in relation to the block. Once both of these are correct you can then check the planer tables.


hope this helps.

I'll see if I can check this, but with the fixed feed rollers either side of the block and the extraction cowl in the way I'm not sure I can get in close enough to the block to check. Will give it a go tomorrow and let you know.

Olly - I definitely want to fix it as I want to make a box and this level of inaccuracy is really throwing out my progress as I want to be able to chuck them through the thicknesser, couple of swishes with finely set plane and rock n roll.

I think you are right about the central column, I think any corrections will have te be to the block or blades (then planer tables).

Will update you tomorrow when I have had a chance to get 'under the hood'.

Cheers

 

[TrimTheKing]

I've just had a bit of a lightbulb moment :idea:

I think that although the thicknessing table is only moved by a single column, that column has a round plate atop it with a flange (I think that's the right term) with 4 holes for the machine screws to hold it to the underside of the table.

If it does turn out to be the table out of whack then I suppose it would be possible to shim one side of the flange(?) to lift it enough?!?

Will have a closer look tomorrow...

 

[MikeH]

As a temporary fix can't you just use the piece of timber that you machined as a sub table? It will have been machined parallel to the blades so anything else you put through on top of it will be parallel to the blades by definition. Probably not a permanent solution and of course you loose a bit of thicknessing capacity but short term until you fix the underlying problem it may get you out of a jam. Might need something like a formica top to make it slippy enough.

Unless I am completely mising the point here!

 

[woodbloke]

I've just had a bit of a lightbulb moment :idea:

I think that although the thicknessing table is only moved by a single column, that column has a round plate atop it with a flange (I think that's the right term) with 4 holes for the machine screws to hold it to the underside of the table.

If it does turn out to be the table out of whack then I suppose it would be possible to shim one side of the flange(?) to lift it enough?!?

Will have a closer look tomorrow...

Mark - it may even be a rough bit of casting on the flange surface or a burr on a hole which is throwing the thicknessing table out - Rob

 

[OPJ]

Yes, Mike, you've got the right idea. :wink: In fact, I think David Charlesworth advocates such a thing in his book, where he talks about using a false bed to thickness very thin stuff and how the usual sheet of MDF may not give accurate results.

Formica would be a good addition, as would a hook on the front end to stop the base from also being pulled through the machine! Of course, the biggest problem in using a width of solid timber is that it will be prone to cupping in time. Unless you stack-laminated it from narrow widths... :-k

 

[TrimTheKing]

Sorry to bump this one chaps but I have finally managed to find the time to have a bash at this, and after 5 hours in the workshop yesterday I have got to the bottom of it!

I will try and take, and post, some pics later to cut the story into a less boring one

I checked the gap between thicknessing bed and cutter block and found it to be out by a small amount. Nowhere near as much as the discrepancy I was seeing, but I wanted it right, so undid all the hex bolts and shimmed up the left side (as you look at it when feeding in stock for thicknessing). This is now almost bang on!

Then I run though some stock and find that the error is now worse than before even though I have shimmed it up!!! :shock:

Next I took out, cleaned, honed and replaced the blades making sure they were bang on.

Error even worse now!!!

The manual (as anyone who has this machine will attest) is a pile of Chaiwanese translated pap, containing nothing more than a few vague destructions. With that in mind I did what any self respecting machinery owner would do, and pulled the bl00dy thing apart

When you look inside the thicknessing table 'area' there is a plate screwed onto one side wall, so I undid these screws and found the adjusting pins for the feed rollers located inside. These are mchine screws fixed into the axle of the rollers, through a lug in the casting and with a spring attached and fixed with a nut.

Not having a scooby what they would do I began tweaking...

It seems that maybe the springs weren't tensioned enough because after an hour of feeding stock, measuring the thickness, tightening the feed rollers one at a time (to get rid of the tendency for tht stock to get pulled violently to one side when hitting the outfeed roller, which was another thing that had bothered me), I have now got the machine pulling the stock in perfectly straight for the full length of the cut and the discrepancy is now 0.02mm across 300mm width.

I'm quite happy with that, but SWMBO is taking baby out this afternoon for coffee with the wives, so I have another couple of hours to tweak that and see if I can get it absolutely bang on.

Anyway Olly, I will post some pics a bit later to hopefully illustrate these ramblings a bit better and maybe you can get yours sorted too.

Cheers all

Mark

 

[OPJ]

Sounds very promising, Mark. I look forward to seeing the photos later. ...And also, how you managed to fit a 300mm width of timber through a machine with a capacity of 250mm!

I did look at leaving one table down when thicknessing, by the way. It exposes such a large gap at both ends of the cutter block (even with the black tab removed) that I didn't want to try and switch it on. :?

 

[TrimTheKing]

Sounds very promising, Mark. I look forward to seeing the photos later. ...And also, how you managed to fit a 300mm width of timber through a machine with a capacity of 250mm!

Well I did say I pulled it to pieces I made a few mods to it on the way...

Nothing more than a brain fart, of course it is 250mm, the piece of beech I was feeding through is a shade under 10" wide.

Shame though, all this work to get it right has taken a lovely 52mm thick, 250mm wide, 2' long piece of beech down to 20mm thick to get it right. Suppose it will save more timber going forwards though, so needs must.

 

[lurker]

Is it OK to let babies drink coffee?

AND how many wives do you have :shock:

 

[TrimTheKing]

Is it OK to let babies drink coffee?

AND how many wives do you have :shock:

She only drinks latte's, which is mostly milk, so I think it's okay

I think there will be around 5 of them meeting up today, there's somewhere in the region of 9. Got to keep your options open

And to add to that, I have managed to get the thicknesser to around 2/1000" across the width which I have tried a few times, with different boards of different thicknesses and it is pretty repeatable, to within a couple of thou each time.