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How To Change The Drive Sleeve Bearings On The Rf-31 Mill/drill

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mikey

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#1
The drive sleeve, or spindle taper as Rong Fu calls it, sits atop the machine head and transfers rotational force to the spindle. The sleeve is supported by two radial bearings, spaced apart with an aluminum spacer. This spaced arrangement allows for greater resistance to flexion and is commonly found in almost all belt-driven drill presses. There is no provision for preloading these bearings.

The set up works well until the bearings go bad, at which time they allow the sleeve to move about, which leads to the top of the spindle moving about. This leads to premature wear of the spindle and spindle bearings, leading to excessive runout and poor finishes. If you experience bouncing of the indicator needle when checking static runout, there is a very good chance that your sleeve bearings are going and it might be time to change them.

This is a pretty simple job that takes maybe 20-30 minutes if you take your time. To access the drive sleeve you must remove the quill from the machine.

The standard bearings used on the drive sleeve of the RF-31 are 6009ZZ shielded bearings. I replaced them with Nachi 6009-2RS bearings that are permanently lubricated sealed deep groove bearings. Total cost for both bearings, shipped from ebay, was under $28.00 so it’s not too expensive to do.

Ideally, it’s best to use a hydraulic or arbor press for this job. It can also be done with a hammer (Yaayy!) if you have or make a bearing installer that spans across both races at the same time.

To begin, remove the quill from the machine. Then remove the lock nut atop the main pulley; this is a RIGHT HAND thread. I used a Luminar spindle wrench and a Rigid adjustable wrench for this job and the nut came right off; it is just snugged. By the way, if you do not own a Luminar wrench you need to buy one – it’s very useful.

wrenches.jpg

With the nut off, I used a 2-arm puller and popped the pulley off. The tips of my puller matched the bevel of the pulley almost perfectly and it came off the taper easily with no sign of damage to the pulley rim. This tells me that we can rely on the taper to hold the pulley in place and do not have to use a mallet when re-installing it.

Once the pulley is off you can see the retaining ring atop the bearings. The three screws are just snugged and are not on very tight.

retaining ring.jpg

With the retaining ring removed, the upper bearing will be visible. To remove the drive sleeve from the head, push it out from below. (There is a large Circlip under the bottom bearing but that doesn’t have to be removed.) I used a piece of wood and an old scissors jack to push on the snout of the drive sleeve from inside the head. Push it out towards the top; it comes out very easily.

jack.jpg

To remove the bearings, you have to remove a small retaining ring from a groove just under the lower bearing. Note that there is a shoulder just under the pulley taper so you must drive the sleeve out of the bearings. Face the taper down and support the bearings on the press plates of your press and drive the sleeve out.

shoulder.jpg disassembled.jpg

Once the drive sleeve is cleaned and inspected, apply a light coat of oil to the area where the bearings are located. The Nachi bearing’s inner and outer races are at the same level; if both races are supported by your pressing plates during installation no pressing adapters are required.

Press on the upper bearing until it seats on the shoulder of the drive sleeve, then slip the aluminum spacer on and drive the lower bearing into position. This is a light press fit, maybe about 0.0002” or so. Replace the retaining ring and you can re-install the drive sleeve.

Clean and lightly lube the hole for the sleeve and start the lower bearing into the hole. This is a very light slip fit; it feels like maybe 0.0005” or so. Still, if the bearings get cocked going in they will bind. To avoid this I used aluminum pucks and threaded rod to drive it in straight and it went in with almost no effort. The lower nut is fixed and locked with a jam nut below the lower puck. As the upper nut is tightened it pushes the drive sleeve straight in – easy.

drawing in.jpg

Now replace the retaining ring and three screws. After cleaning the tapers of the sleeve and the pulley, install the pulley and lock nut. I just firmly snugged the lock nut. The taper will hold the pulley in place without excessive pressure from the nut.

That’s it – simple bearing change.

Replacing the drive sleeve bearings made a big difference on my machine. Prior to changing the bearings my indicator needle jumped all over the place and getting a reliable static runout reading was impossible. After the bearing change the indicator read smoothly and allowed the spindle to run more accurately.

Hope this helps.


Mike
 

henrivdr

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#2
Thanks for sharing Mike. I did not even know of a Luminar wrench till now.

Sent from my F5321 using Tapatalk
 

mikey

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H-M Supporter-Premium Member
Joined
Dec 20, 2012
Messages
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#3
Thanks for sharing Mike. I did not even know of a Luminar wrench till now.

Sent from my F5321 using Tapatalk
You're welcome - it's a really useful tool and well worth the cost.
 
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