Planer cutterhead bearing replacement #1: HELP! Can anyone give me advice on replacing bearings on my planer cutterhead?

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Last week my planer blew a bearing on the cutterhead. It is a NuMark 12” planer, more than 30 years old. The company went out of business many years ago.

I cannot determine how to remove the cutterhead. Here’s the issue:
1. The cutterhead casting is a single unit.

2. The bearings on either end are smaller (35mm and 40mm) than the cutterhead diameter (47mm) so the cutterhead cannot be pulled or pushed out either end.

3. From the parts schematic, the cutterhead appears to be one piece (no smaller diameter inside shaft).

I considered attempting to remove the old bearing

and press in a new bearing without removing the cutterhead, but cannot determine how to remove the old bearing. (There doesn’t appear to be any where to get a puller on it.)

Do any of you mechanically-minded woodworkers have a solution for me?


-- “Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.” Benjamin Franklin

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It is impossible to cast the bottom around the cutter head, my guess is that the shaft running through the cutter head is removable it should have a long key way . Look for set screws in the cutter head to release the shaft . If no set screws in may be pressed in . Try taking a punch the size of the shaft and tapping the shaft left or right to release the bearing .

-- Wheaties


Thank you for your advice. The knives and lock bars are already out of the cutterhead. I didn’t want to take a chance on damaging their edges.

The bearings are shielded. The reason for the replacement is that the race cage retainer broke and forced the shields off the bearing shown. Since it was already broken, removing the race cage retainer was fairly simple. The shields had the bearing number stamped in them so I know the correct size and it is readily available.

I had initially thought that I could push the cutterhead through the drive side assembly, but after tearing it down to where it’s at now, I measured and realized that 47mm just can’t fit through a 40mm opening. ;-(

Thus, the cry for help.

I’ll try some of your ideas on Friday to see if I can make it happen.


-- “Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.” Benjamin Franklin

Get a set of verniers and measure the outer bearing cases, from the IPD the assembly you have provided it looks like it is removed from the driven side, meaning its this bearing that the outer case is bigger than the cutter head body, even if its only a clearance size.
(However from your notes and photos this looks impossible to do)
You will/should consider removing the blades first.
Otherwise lever the bearing case out by applying force to the outer case You could do this this with a drift or a expanding bolt
Either way one of the bearings will move along with the cutter head until it touches the side of the housing.

You could also heat the housing and spray the bearing with freeze to loosen it.
It must come out otherwise how did it get assembled in there in the first place.
Now if this does not work,
On the failed bearing remove the ball bearing retainer case, (this is the metal part equally spacing the balls around the bearing) be aware this is fairly brutal work!

Once you have the race cage retainer out push all the balls together upwards leaving a gap at the bottom, then push the shaft down and the balls will snap away from the inner race, allowing you to remove them.
Remove the balls and then in gap between both inner and outer race insert the gear puller legs and remove the remaining bearing shells.
Now remove the second bearing and there may be enough space to swing the cutter assembly out.

Do not throw the bearing cages away as they have size numbers on them possibly in a code, otherwise take them to a bearing service supplier and they will be able to give you direct replacement, even if its a non stock item and has to be ordered in.

-- Regards Rob

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