Sedgwick MB Planer Thicknesser Full Refurbishment

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The arbour was mounted in the lathe and the sprockets slipped on and held firmly by tightening the grub screw.
The boss had to be tuned down to match the original as they sit against the cast blocks that hold the infeed and outfeed rollers. Any larger and they will also rest against the side castings of the machine which would reduce the amount of end play.


Finally all of the new sprockets are mounted to the machine.

Just for interest, this is what the original sprocket teeth looked like, very badly worn. The shape of the wear indicates that the sprockets and chain were not properly aligned which has rounded over one side of the teeth. These are now going into the bin.

A new chain has been made to length, the one on the machine was actually too long. We guess that it had been replaced at some point possible due to the chain jumping the sprockets due to the wear. The longer chain meant that the tensioning system was not working properly and again would cause the chain to jump.
Sideways had finished wiring the machine up, so it was time for a test of the thicknesser rollers.

You can hear a slight ‘chinking’ as the chain is running. This is due to the chain just lightly brushing against the spindle pulley. Although the new sprockets are exactly the same size as the old after machining and are properly aligned, there is simply not enough space to adjust this ‘collision’ out with them as they are. We will take them off again and machine a little more off the back of the sprockets to allow more adjustment. This is a common issue with these machines, they work, but they can be refined with a little engineering And as a consequence will run quieter and last even longer with out attention.
1000v insulation resistance test, Live and Neutral to Earth on both motors and starters...
Deema's holding the contactors in and pressing "go".
Bosses of the sprockets shortened, sprockets refitted and lined up using a long straight edge.
You don't need much misalignment before the chain runs erratically and clicks as the sprocket teeth catch on the side links of the chain.

I'd say these were lined up better than 2mm from top sprockets to the motor sprocket.

If you don't have the straight edge, measure from a consistent point on the chain like the end of the rivets to the side casting.

This only works for the upper half as the pressed steel base is offset relative to the casting and it's fussy to work out the alignment on the motor sprocket.

The spring loaded tension adjuster has to sit very close to the casting for everything to align. If it is placed correctly, the idler pulley which floats freely will align with the chain instead of trying to pull it out of line

All good, now for the spindle V belt

Straightedge used for alignment as before. Belt fitted and tensioned.

Clearance between the belt, pulleys and chain must be checked to make sure that nothing vmcan foul. The clearances are a little snug especially at the top.

Then CHECK THE CUTTERBLOCK and run it up. Tweak the tension as the belt warms up and beds in.
Refit the blades:



Note that the wedges are marked and must be matched to the correct slot in the block


Jacking screws at each end of each blade should be wound all the way in,

one at a time the wedges then blades are inserted and the wedges gently nipped up.




The jacking screws are accessible in this position so gently unscrew them to raise the blade until it stands parallel to the outfeed table and a few thou higher at top dead centre.


This distance depends on the diameter of the cutting circle etc so if you were setting up a different planer it would be different. The height can be calculated by geometry. For a first cutting test we just measured Deema's Sedgwick CP and used the same setting.

Once levelled, tighten up the 5 big allen bolts on each wedge tightly so you won't lose the blade or wedge when the block spins up. It's a great way to smash the end off your infeed table !
Looking pretty with a brand new original dust chut£££


This is thicknessing position.
For planing it sits under the block and the thicknessing table is raised to lock it in place.

Some quick test cuts (without extraction) and then off for tea.
The tables are still covered in anti rust wax and haven't been buffed, but it certainly cuts. Nearly there !

The thicknesser needed setting up, the two rollers and the springs needed adjusting to the blades that we had already fitted. The manual gives a method using a piece of wood to establish bottom dead centre of the cutter block. We use measurement as we feel is more accurate.

First off use a OneWay we measure the bottom of the blade, rotating is to get the maximum reading and then set the clock to zero……I did for the setup correct the minuscule error in zero😂


The plane roller at the back is set to be 2mm or 80 thou below the cutter.

The front serrated roller is set to be 1mm below the cutter.


here is the instruction from the manual. We use a small engineers ruler to set the spring length. We generally set the sprocket side 5mm tighter than specified at 60mm and the other at 55mm.

This only needs doing usually of the rollers have been removed.
We generally set the sprocket side 5mm tighter than specified at 60mm
So you meant 'looser', then, not tighter? Since there's a bit of downward pull from the chain drive and this is to compensate ... ;-)

Ideally one would adjust the rollers to a higher pressure for heavier workpieces, and lighter pressure for lighter workpieces. But unless doing a big batch of similar stuff, it's easier to aim for a compromise.
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I compress the spring on the chain side to 55mm rather than the 60mm specified, ie tighter. I have found that this works better, the chain does create a force on the rollers which is why it doesn’t need as much compression in this side.
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Well done, a very comprehensive account.

Back in 1983 I bought my MB new from Tewkesbury Saw Company and it's been in daily use since then. Mainly for light work in my furniture workshop. Less now that I've just retired.

There is one thing that has plagued me...the self aligning bearing on the cutter block keeps failing, it's been replaced with SKF bearings about half a dozen times. When replaced it purrs as it should but after a couple of months it starts to whine.

I'm careful when replacing the bearings and make sure it's all running true etc.

It's time to replace it again now, do you have any suggestions on how I can get it to last longer?


There arn’t that many causes for a bearing to fail. Typically it’s dirt ingress, damaged race due to excess force when fitting, heat due to it rotating in the bearing housing / on the journal. So, I‘m guessing, but I suspect the bearing is a sloppy fit somewhere and it’s rotating with the shaft rather than acting as a bearing. I’d use some bearing lock to retain it if this is the case.
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