My old Makita 3901B router needs new bearings.

They arrived the other day care of a Makita Service agent.

Despite me asking (and showing them how far I'd got) they offered no
hints as to how to do it (obviously grumpy at the fact I wasn't going to
pay them to do it for me).

The front bearing took a little thought and was removed using a gear puller.

I am stumped if I can work out how to remove the rear one!

monospace

shaft
|
v

+---+---+---+
| | | | - rear bearing
+---+---+---+
====+===+==== - washer
XXXX| |XXXX
XXXX| |XXXX - commutator assembly
XXXX| |XXXX

windings etc.

/monospace

There's no gap between the bearing and the washer and certainly nothing
else on the assembly I would rate strong enough to grab with the gear
puller.

I can get a firm grasp on the bearing with a set of multi-grips and have
tried tapping the shaft out with a steel rod (of slightly smaller
diameter) without luck.

Any help would be appreciated!

Cheers, Antony

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address ***

Antony N. Lord writes:

Any help would be appreciated!

It may have been heated and pressed onto the shaft.

You may have to cut it off.

Antony N. Lord wrote:
My old Makita 3901B router needs new bearings.

They arrived the other day care of a Makita Service agent.

Despite me asking (and showing them how far I'd got) they offered no
hints as to how to do it (obviously grumpy at the fact I wasn't going to
pay them to do it for me).

The front bearing took a little thought and was removed using a gear puller.

I am stumped if I can work out how to remove the rear one!

monospace

shaft
|
v

+---+---+---+
| | | | - rear bearing
+---+---+---+
====+===+==== - washer
XXXX| |XXXX
XXXX| |XXXX - commutator assembly
XXXX| |XXXX

windings etc.

/monospace

There's no gap between the bearing and the washer and certainly nothing
else on the assembly I would rate strong enough to grab with the gear
puller.

I can get a firm grasp on the bearing with a set of multi-grips and have
tried tapping the shaft out with a steel rod (of slightly smaller
diameter) without luck.

Any help would be appreciated!

Cheers, Antony


Mcmaster.com has item 6342K2.

This is very similar to what we use here in the shop.

Richard J Kinch wrote:

It may have been heated and pressed onto the shaft.

You may have to cut it off.

The front brearing was tight but not impossible (using the gear puller).

Looks like a long evening with the Dremel perhaps...

Cheers, Antony.

*** If replying via e-mail be sure to remove the obvious typo in my
address ***

My old Makita 3901B router needs new bearings.

[snip]
I am stumped if I can work out how to remove the rear one!

In the end I was able to get the rear bearing off using a Dremel.

I gently replaced the two bearings (front and back) tamping them in
using their centres (or using the gear puller to push).

Sadly I tested it out and the rear bearing got real hot really quick -
something is buggered up.

I gave up in the end and decided to cut my losses and returned the unit
to the local Mikata agent.

They replaced the bearings (again!) and gave the machine back.

On getting it home I discovered :

a) They hadn't tightened up the collet on to the shaft - duh (and I have
no idea how to do that easily)
b) The collet is eccentric (off centre) - bit vibrates as though
something is bent

After much thinking we (here at home) figured the original collet must
have been damaged when we tried to get the front bearing off the first
time. So we ordered a new one to discover the problem remains!

To me this suggests that either the tiny length of shaft (~12mm) that
protrudes beyond the front bearing is bent [unlikely] or it has
something to do with the collet rubbing on the housing. (In fact the
back of the original collect is clearly burnished silver in appearance).

If you put a compass point in the depression of the shaft (no collet)
and spin the router up there is no detectable wobble in the shaft.

Perhaps the shaft is seated too far back in the scheme of things?

I would really like some suggestions here - the toolshop doesn't seem
especially helpful or clueful on this one and I'd love to get the old
girl up and running again (there's so much to be routed!)

Cheers, Antony.

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