Thread: bearing damage on jointer cutter head

Hi all,

Some time back i was gifted a Gilbro saw table/jointer combination machine. Apart from some surface rust and wood chips/crud from 50 years of use its in pretty good condition. None the less i have done my usual thing of totally stripping, cleaning and replacing the bearings. Up until now there has been nothing to repair and thought i got out of it scott free! However, when it came to the jointer i noticed considerable play on one side of the cutter head. It turns out that for some time the shaft had been turning on the bearing, wearing down the shaft. Not an uncommon problem with neglected machines.

The unworm part of the shaft is 19.05mm (3/4") which takes an RMS6 bearing however the worn part where the bearing seats is 18.68mm so 0.37mm under sized

Anyway i guess i have several options;

1: Cheap and cheerful would be to use a high strength high viscous loctite

2: turn down the shaft, press a sleeve on and turn back to 19.05mm

The 2nd option is a little trickier than i thought, the centre holes at each end of the cutter head do not hold the cutter concentric when held between centres. For some reason, its out by approx 0.25mm tir.

This is not terribly important for the blades because they are placed in position using a jig the places them at even height relative to the table but is important for vibration as it spins at approx 4600 rpm. So i want it to be as concentric as possible.

Rotating the cutter held on V blocks at the bearing locations yeilds a tir of about 0.05mm which seems acceprable.

If i hold one end in the 4 jaw at the bearing location, where would i support the other end? Cant use a steady because its where i want to turn down?

2nd pic you can see the worn section and a small amount of galling.

Any ideas?

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Option 3: turn the worn section down, build up with weld and turn to size?

Could you hold it by the keyed section with enough sticking out to still fit a tool and then have the good bearing journal in a steady?
Or make a cap that's a neat fit over the keyed end with a turning centre in it instead of using the existing bad centre?

You could shrink a ring over the largest od of the drum so the steady fingers don't go into the grooves. Or your cap idea, basically the same outcome probably.

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Simon, you could set it up with the steady then re-cut the centre with a ground up piece of HSS,
then use the centre to hold it for turning and sleeving.

cheers, shed

Simon,
the point you make about the cutter not running true between centres immediately told me that one of the shaft ends is bent. That might be the root cause for the bearing seat wearing as it did. My guess is someone dropped something onto the spindle or caught a splinter between the running spindle and the table and jammed it. The inertial of the spindle and the motor would easily be enough to bend the cutter spindle...
If you have a press, there is no reason why you couldn't straighten it until the centres are true again.
Then I would get hold of a stainless steel sleeve (or turn one up) with an ID of the worn section. Heat it up (probably glowing) until the ID will fit over the 19.03 end and press it on to cover the worn section. once cooled, turn carefully back to 19.03 between centres on the OD and reassemble.
Correcting the bent end by turning true or building up to do so is fraught with risks of distortion....

Thanks for the speedy replies guys. Really appreciate it.

Elan, I had thought about option 3 but I discounted it. Reason is because I have done it once before with a 3 phase motor shaft which I accidently turned undersized. I was never really happy with the result, most likely a result of my lack of skill in that area.

A sleeve on the large drum to cover the cutter housings is something I have given some throught to as well. I ring that is heated and slid on would probably work but I am yet to check if my fixed steady will open up to over 3 inches. That would be a good option if it did.

Joe, the reason why I don't think the shaft is bent is because it runs quite true in V blocks suspending it where the bearings seat. You're pretty switched on with this stuff so I will have a closer look at it. Taking measurements and observations cost nothing and does no damage. Measure twice and cut once is equally applicable to turning as it is carpentry!

I will absorb the above suggestions and report back soon!

Simon

Had another play with things. Now if I support the cutter head on V blocks resting where the bearings sit I get about 0.08mm TIR on the drum at both ends. If I then move the indicator to the end of the shaft (longer end where the pulley is) I get TIR of about 0.2mm.

I don't think the 0.2mm runout at the pulley is going to cause too much issue so I'm not going to attempt to fix that.

The drum of the cutter, which is 3" is too big to fit in my fixed steady. So what I plan on doing is mounting the "good" end in the 4 jaw where the bearing sits, at the other end I will support it with the fixed steady on the shoulder in from the bearing.

I will turn a piece of brass to snuggly slide over the cutter cylinder and use that to indicate off to adjust both the 4 jaw and the steady.

I will then turn down the shaft by approx 1mm, heat up and slide an oversized sleeve on and then turn down to the finished size of 19.05mm.

For this job I will grind up a nice and sharp pieces of HSS which will enable me to take nice light cuts to the shoulder using a saddle stop.

Well, that's the plan anyway....

Simon

Hi Simon,
From the photo I'm guessing that it's the end with the long section of shaft that has the worn section?

If this is the case the problem you may face with shrinking on a sleeve is that the worn section is below the smallest diameter of the shaft so you might have trouble getting a shrink fit sleeve over the unworn section of shaft.

If you can get a sleeve to shrink on by the time you machine it back to the required 0.750" you will have a wall thickness of less than 0.2mm which may not have sufficient strength to stay in place on the shaft.

Making a stepped sleeve that's a shrink fit onto the larger diameter adjacent to the spindle body and using a bearing with the same OD and a larger ID (if one exists) might be a workaround.

Regarding the off centres, I assume from your photo of the spindle mounted on v blocks that the long end of the shaft, the spindle body and the short end of the shaft are all concentric?
When you had the shaft between centres did you measure the run-out of the shaft at each end adjacent to the centre? What I'm asking here is are both centres off relative to the shaft or just one of them?

If it is only one centre that is off you could mount a DIY centre in your four jaw, mount the spindle between this centre and the tail-stock centre then adjust the four jaw until the spindle runs true.
If it's the long end that has the off centre you should have sufficient room to have your drive dog in place and still be able to access the damaged area for machining.
Cheers,
Greg.

Just in case it hasn't come up in people's thoughts, it IS possible (and done a lot) to scrape the centre back to where it belongs with a triangular bearing scraper. It's tedious but not very time consuming....

With all the mucking around that sleeving etc will require, is it quicker to make a complete new spindle?

One other option - machine down the worn section to solid metal and then make up a split sleeve (glue on with Loctite). There is a bearing going over the top, so once installed it will stay put.

Michael

There are processes that deposit metal to repair surfaces. Thermal spray, plasma spray type of processes. You could see if there are any services like that. The costs might not be too high and the resulting metal is one with the original. You can then grind/turn it to size knowing it won't come off nor is there any affect to the original metal's heat treat.

Pete

QC's suggestion is likely the best way to repair it but i like Micheals spltit bush idea also.
Another posibility, maybe a bit rough, is to straight knurl it to expand the metal, flood the knurl with loctite, maybe 620, and press the brg on.

get it hard chromed...and then turn down.

Option #6

If the machine is a keeper take some measurements and see if there is one of those helical cutter heads that will fit, at a guess most similar sized machines would run the same shaft sizing and head dia.
Might cost a bit... but if its a keeper why not

Originally Posted by eskimo

get it hard chromed...and then turn down.

Years ago I got an early twenties Austin 7 crankshaft main bearing journal which had been turning in the seized main roller bearing copper plated and turned it back to size. This worked OK - no problems in the time I owned the car.

Frank.