What bearing spec. for jointer?

[J.R. Rutter]

I'm going to be replacing the bearings in my 12" jointer as soon as my production schedule allows. This is a 50s era machine and currently has fittings for greasing the existing bearings.

I assume I can replace these with sealed bearings (?)
What should I ask for in terms of precision?
Can anyone suggest a good point on the price:performance curve?

Thanks

[Rob Will]

I'm going to be replacing the bearings in my 12" jointer as soon as my production schedule allows. This is a 50s era machine and currently has fittings for greasing the existing bearings.

I assume I can replace these with sealed bearings (?)
What should I ask for in terms of precision?
Can anyone suggest a good point on the price:performance curve?

Thanks

We all know that Dev is working on the answer to this right now.
So I want to know how these bearings compare to typical ag / industrial bearing that I get at the local supply house. (??)

Rob

[Dev Emch]

Well that all depends on what you want to do. I dont do modern stuff like brand new grizzlys so what I say may not apply very well.

The top end makers of old iron who made many 12 inch jointers actually used the finest bearings they could find. Those of us who have rebuilt these actually use ABEC class 7 bearings in these brutes.

The best bearings out there are made by companies like Barden and are either ABEC class 7 or 9. These are very expensive bearings and if your not careful, you may be the poster child for a running joke. "How do you make a generic, low cost ABEC class 1 bearing? You use a hammer and 2x4 to install an expensive ABEC class 7 bearing."

Many of the older machines such as jointers and shapers used these high end bearings to help stabilize the cutting flutter. These bearings are milling machine spindle bearings.

Now on some jointers, these bearings are lubricated with zerks and grease while others are oil lubricated. My porter jointer has two oil resoviors in which I can change the bearing oil like the oil in my truck. Many older machines had glass drip oilers that gradually feed oil into the bearings via a wick system. See the oliver 287 shaper or the State B4 spindle sander.

Generally, the old rule is this. Bearings turning at 10,000 RPM and less are run with grease while higher speeds need oil. The faster you go the more heat has be drawn off the bearings. Heat is one thing that can kill a bearing. But this is not fixed. In the old days, the prevailing idea was that oil is a superior lubricant to grease. After all, grease is oil with some soaps added. But grease does not channel heat.

As speeds increase, you may need to go to oil mist injection or oil myst as they say. Companies like Bijur made a living selling machine tool oliers to machine tool companies. For example, my 1940s Onsrud 244 pin router has two speeds... 10,000 and 20,000 RPM. At 20,000 RPM, you need a Bijur oil mist injection system that uses compressed air to spritz an oil myst into the bearing. The myst gets you better coverage and helps remove excess heat from your inner and outer races. Often, this oil was sucked out the bottom of your quill structure and recirculated. So oil myst injection serves two purposes. 1). It lubricates your expensive bearings with a good quality oil and 2). It acts as a bearing cooling system to keep your critical parts cool and running.

Over the last 20 years, the bearing industry has made major strides in lubrication grease and this has allowed for the advent of sealed for life bearings. Many sealed bearings are available in the same sizes as your unsealed bearings. The difference is the addition of a tiny sheet metal like seal and a load of special grease that will last the bearing for its life.

First of all, the bearing is not sealed for life as you think. Its certainly not your life as you will outlive the bearing. That makes this term a bit of an oxymoron does it not? Secondly, the seal is good enough to keep the grease for the most part inside. But it still can out gas volatile vapors which helps to reduce your lube grease into thick sticky soaps. Thirdly very fine saw dust can leach these volatile compounds through the bearing seals and leave you with the same gunky soaps.

So I can see why many designs have gone to cost reduced, sealed for life bearings. But many of the better machines do not use these. My Hofmann shaper does not use any sealed for life bearings with the exception of the SKF linear bearings used in the top rail of the sliding table. The high speed super precision stuff is lubricated with a high grade of Mobile machine grease. I would prefer a liquid oiler like my old oliver 287 had.

So if I were facing your task at hand, I would first look at replaceing those bearings with the best ABEC grade I could afford. ABEC 1 bearings are often generic use bearings found in tractors and often the ones used in non DMD application electric motors. But manufacture of bearings has improved over the years to the point where the class 1 bearings are actually at the quality level of say a class 3 or maybe even a class 5. They just label them as class 1 by tradition. A class 5 should handle most woodworking needs and if your really intense, then you need to look for a class 7. But if you go class 7, make sure to investigate the lubrication system being used.

For what its worth, the bearings in my oliver 299 planer main cutter head, the oliver 166 jointer yoke and my porter 300 jointer yoke are all class 7. The planer uses greased bearings while the oliver was modified for grease (not by me) and the porter uses liquid oil.

Hope this helps a bit...

[Erik Rudd]

Nice bearing primer. All of the ABEC-7 bearings that I've seen are metric, am I missing something?