Table Saw Bearings

[scholar]

My table saw started making a slight rattly sound which I didn’t like the sound of - I couldn’t find anything that seemed loose and so I have stripped it down to look at the bearings.

This is a Scheppach TS4010 table saw - it is an all fabricated steel cabinet (takes a 315mm blade) - I have had it since new in 2001, but I am really such an occasional user that I would be surprised if the bearings have actually worn out.

Anyway, here is the spindle with bearing either end extracted from the frame the bearings sit in - they are just held in holes in the 8mm plates either end (with retaining plates at one end).

The bearings do not seem rough to turn, but there does seem to be some in/out play between the inner and outer races - I will replace them anyway - the existing ones are NSK 6204DU (I was surprised to see British bearings on this German machine). What would be the best replacement? These have plastic seals - is there any advantage in stainless steel seals?

I removed the bearings from the frame just by hand - I don‘t know if they have worn themselves to a loosish fit - we will see how the new ones go I did think the bearing housing would be a bit more sophisticated/heavy duty (I haven‘t yet tried removing the bearings from the spindle).

Does anyone have any observations/recommendations?

Cheers

 

[Orraloon]

I would get the same sealed bearings. NSK are good ones and will be fine.
If they came out of the frame easily then perhaps they are a bit loose in the holes. A tight fit is the usual. I am not familiar with that saw so can you do some pics of the retaining plates and the way they are secured.
Regards
John

 

[clogs]

if ur worried about the fit of the bearing in the frame Locktite make a product just for that....
there are several grades...
if they slide in with no rock or lift, that product will do just fine.....
there is a time limit on the product so dont use it then go for tea....lol....
please DONT use a center punch to dimple the hole in the frame...it really doesnt work....
I have fitted bearings to all maner of machines in the 50 odd years, the biggest being over 3m in diameter...
still cant find the photo to proove it....
as for the seals I always go for the rubber sort....
as an add on, the bearings are lubed on assembly for life.....which is not not my fav way but thats life...
the lube does dry out over years and the bearing can be smooth'ish and rattle at the same time...
on lesser machines I have popped one of the seals washed out the old lube and repacked them...
it does give them a second life if done early...but bearings even good qual ones are quite cheap now....

 

[sawtooth-9]

Agree with clogs, but
If you can remove bearings by hand - they are tfar oo lose.
Locktite bearing retainer is great, and there are a few grades available.
I agree with clogs, centre punching to fit bearings is a last resort !
Unlike clogs, I tend to go for a metal shield - they hold in lubrication from the manufacturer and prevent ingress of ..... , - in my experience for over 30 years !

 

[scholar]

Thank you all for your input - that is very helpful.

I did wonder what gunk would have been applied on the bearing in the housing as you can see some remnants (see picture below).

From a quick look, it seems i have the choice of Loctite 641 - Medium strength or Loctite 638 - High strength. Looks to me like Medium strength is offered for this application, but would I be better going for High strength? (I will ask the bearing supplier when I sort that out).

The retaining plates which hold one bearing are shown below assembled into the frame.

My guess is that it might have been the other bearing that could have been rattling - the outer shell appears a bit shinier in places.

Cheers

 

[Orraloon]

The retainer plates look pretty basic but I guess Scheppach employed an engineer to design the thing and they have done 20 years. Going by Clogs post he has done a lot more bearings than I have so I would go with what he says. I had heard of of a locktite product but have never had to use it as normally they are a right ba$#@rd to get on and off.
Regards
John

 

[Sideways]

I will replace them anyway - the existing ones are NSK 6204DU (I was surprised to see British bearings on this German machine).

?
NSK are top brand bearings with a 100 year history but Japanese, not British
https://www.nsk.com/company/history/index.html
Your Scheppach is a German name but will be made in China so NSK will be easy to source. Then again, I'm sure SKF have bearing factories in that part of the world too.

 

[scholar]

?
NSK are top brand bearings with a 100 year history but Japanese, not British
https://www.nsk.com/company/history/index.html
Your Scheppach is a German name but will be made in China so NSK will be easy to source. Then again, I'm sure SKF have bearing factories in that part of the world too.

@Sideways I realised as soon as I posted that comment about the UK bearings that it may be unclear - I know that NSK is Japanese, but these bearings state “England” on the side - I assume that they would be traced back to RHP - Ransome Hoffman & Pollard (had to look it up to remind myself) that was a UK company - I remember RHP being acquired by NSK (in the ‘90’s?) and being a bit sad about it. Evidently they still have retained some activities in the UK and RHP was rebranded NSK for uniformity in 2000, I have read.

My workshop is mostly Scheppach machines, all dating from around 2000 and all of which were made in Germany - Scheppach does seem to have transformed into badge engineering of Chinese made stuff - I think this started after my machines were made with Chinese sourcing of cast iron table tops - I am not sure that Scheppach make any serious machines now, even in China. I know and knew at the time that there were heavier duty options, but plumped for Scheppach for the range they offered at the time and not least for their mobility and flexibility and interchangeability (in terms of extension tables etc) which is a factor for me in my relatively restricted space. My big planer is Scheppach’s Ixes brand (now defunct) which is a very decent machine.

I felt it was a compromise at the time to have an alloy table on the table saw in the interests of mobility (all my other machines are cast iron), but for my careful use this has been fine - it has a sliding table but I still yearn for a proper slider adjacent to the blade. - just need more space!

Cheers

 

[Sideways]

Ahhh
Interesting history there. I also remember RHP and come across their bearings fitted from time to time. Quality.
Looking at your alloy tables, I'm now reminded of seeing that model or it's relatives in the showroom back when Alan Holtham owned a teaching and woodwork retail business called The Old Stores Turnery near Nantwich. That would have been v early 90's I think. The shade of yellow metalwork, extruded alloys and brown plastic control knobs were trademark Scheppach at the time.

Scheppach sold for slightly higher prices than Kity who were a contemporary back then. Others from the time included AEG in grey and red livery, Lurem who did a stint as part of AEG, Metabo (dark green at the time as they are again) and Electra Beckum (pale green, pre Record Power). Many of these machines are still in production somewhere but they have have been bought, sold and badged so many times that the same machines are found in many different liveries over the years.

This store was the first place I ever encountered Felder in the shape of their BF5 combo. It would have been a fairly new design back then. At £5000, heavy and finely machined, that left an impression.

 

[scholar]

Ahhh
Interesting history there. I also remember RHP and come across their bearings fitted from time to time. Quality.
Looking at your alloy tables, I'm now reminded of seeing that model or it's relatives in the showroom back when Alan Holtham owned a teaching and woodwork retail business called The Old Stores Turnery near Nantwich. That would have been v early 90's I think. The shade of yellow metalwork, extruded alloys and brown plastic control knobs were trademark Scheppach at the time.

Scheppach sold for slightly higher prices than Kity who were a contemporary back then. Others from the time included AEG in grey and red livery, Lurem who did a stint as part of AEG, Metabo (dark green at the time as they are again) and Electra Beckum (pale green, pre Record Power). Many of these machines are still in production somewhere but they have have been bought, sold and badged so many times that the same machines are found in many different liveries over the years.

This store was the first place I ever encountered Felder in the shape of their BF5 combo. It would have been a fairly new design back then. At £5000, heavy and finely machined, that left an impression.

Yep, I looked at many of those alternatives at the time - I went to Milton Keynes to have a close look at the Felder stuff - that is my reference point for a sliding table! But I didn’t have the space and actually, I have no regrets about going with the Scheppach stuff - I do move everything around very easily and it has served me well for what I do - also parts availability through NMA has been excellent.

Anyway, I have now ordered some bearings - whoever knew there was so much to know about bearings…!

My existing bearings are 6204DU but this seems to be universally substituted with DDU - I have gone with these, but I did read that DU (single seal, brown plastic) vs DDU (double seal) might be used to prevent a vacuum building up in the bearing - they are rated for 11,000 rpm whereas the table saw only goes at 2,800 rpm, so hopefully the DDU will be fine.

Cheers

 

[Spectric]

Maybe the english bit is just the plastic side covers! They also supply bearings with different fits for shafts and housings.

 

[Sideways]

I would not worry about this but looking at the photo of your bearing, there is C3 etched on the side of the outer race.
This has a meaning.
When replacing the bearings on an AC motor, it is common for the rear, sometimes smaller bearing to be a C3 variant while the drive shaft end is not. If I remember rightly these are made with slightly greater clearances than standard and I always thought of them as accommodating any SMALL axial misalignment between the two bearings or possibly heat expansion. It might be worth looking to see if your bearing from the non blade end is a C3 and whether the blade end bearing is the same or different.
Whatever you have ordered, I don't think I'd bother changing your order, just one more "who knew" for next time

( ignore me if I'm teaching granny ....)

 

[scholar]

That is interesting - it is very feint, but the C3 marking is on both bearings.

There is a difference in the markings on the plastic side covers - both bearings have one side that says A17; the other sides say A03 and A09. I am guessing that somehow this refers to the one side having the seal, but why the others are different I don’t know (I did find a pdf of NSK specs that was about 150 pages long, but DU did not feature, making me conclude it has been discontinued and superseded by DDU.

(And btw @Sideways, you are not teaching granny, I am an just an enthusiastic amateur)

Cheers

 

[clogs]

scholar,
the photo of the ur bearing prooves they have spun in the housing, ur lucky u cought it early...

c3 bearing is the modern name but in the old days they were know as three spot or dot bearings....
they were made loose, that means the balls n carriers were just slightly looser fit....
as said above they were allowed to take higher RPMs without ball scuffing.....
now nobody want's their ball scuffed....lol...
also those 3 dot bearing are used in extremes of cold....think of tooling in Alaska...
and yes they would take a little radial off-set....
as for Locktite bearing fit, basically it all the same but the different colours mean how much clearance they will take.....I cant remember the colour codes now...
there was /is one that will take 10 thou between the bearing and the case...
it's fairly slow to cure as when using this u have to assemble the machine or part there-off....
if ur's has no slop u can just used stud fix.....def not screw fix....
I like the plasticizes rubber seals as it's poss to pop one off/out and just top up the bearing a little...quite often there is just not enough lube....although u can have to much...
to much lube can make the ball slide NOT roll giving flat spots on ur balls...no more jokes about B's....u'll be pleased to here...
Metal seals or shields are as far as I'm concerned are to protect from heat....
PS,
those 3meter bearings I mentioned, we used to play with weigh'd in at over 2 tons and were hand made as far as assembly was concered....the outter cases and assembly was in Switzerland, the ball's came from Japan, the plastic seperators were made in Italy....
loads'a fun bearings....
lastley, pretty much most bearings are made in China under western supervision....
the no name cheap and nasties that are available on line are the unacceptable seconds or even thirds....hahaha.....
good luck....

 

[scholar]

An update on this job that has turned into a bigger one!

I bought some new bearings - NSK to match; these ones are made in Poland. Got it all assembled - a tight fit requiring cooling the shaft in the freezer to get the bearings on, then freezing that assembly and heating (a bit) the frame to get the bearings in the frame - I secured everything with Loctite 641 and put the whole machine back together.

Problem 1: the saw blade now does not line up with the riving knife. I had spotted that there was some left/right adjustment in the bearing retainers and can probably fix that, except it will require releasing the Loctite 641 - looks like this will require heat 250°C. However, on closer examination of this problem, I found that the blade was not square to the irving knife and has a wobble. So resolved to disassemble and have a good look.

Problem 2: the end of the shaft seems to be bent as the following runout summary illustrates:

The runout at either end of the bearing frame is barely detectable, but where the blade is fixed is about 0.23mm which translates to quite a wobble at the periphery of a 305mm sawblade.

So I conclude that the new bearings as installed are OK, but the end of the shaft is bent - how this has happened is a mystery and it is possible that it has always been so, I just don‘t know. I have been having some minor dissatisfaction with the cut sometimes and was hoping this was due to the bearing issue.

Anyway, I have enquired of NMA whether a replacement shaft is available - otherwise, I assume it is possible to get one machined.

Could do without this really.

Cheers

 

[TheTiddles]

Some lateral movement on bearings is common/required.

Properly applied bearing retainer is incredibly strong, I’ve destroyed things assembled with it (when they should have used thread retaining compound)

There is not enough meat all around those bearings to accommodate a press fit without a risk of distortion and that design is not one made to take a lot of thrust, so wouldn’t need that. Also, think how thermal expansion of the shaft would affect it if they were tightly fixed in

 

[scholar]

Good news is that the excellent chaps at NMA have sourced a replacement spindle - this comes with bearings already attached. I will see if I can get some technical guidance on whether the new bearings should be fixed into the frame with bearing compound.

As far as I could tell at least one of the old ones I removed appeared to have a trace of something - the other didn’t, but that had evidently spun in its housing (which is what I want to avoid recurring).

Cheers

 

[Fergie 307]

An update on this job that has turned into a bigger one!

I bought some new bearings - NSK to match; these ones are made in Poland. Got it all assembled - a tight fit requiring cooling the shaft in the freezer to get the bearings on, then freezing that assembly and heating (a bit) the frame to get the bearings in the frame - I secured everything with Loctite 641 and put the whole machine back together.

Problem 1: the saw blade now does not line up with the riving knife. I had spotted that there was some left/right adjustment in the bearing retainers and can probably fix that, except it will require releasing the Loctite 641 - looks like this will require heat 250°C. However, on closer examination of this problem, I found that the blade was not square to the irving knife and has a wobble. So resolved to disassemble and have a good look.

Problem 2: the end of the shaft seems to be bent as the following runout summary illustrates:
View attachment 139557

The runout at either end of the bearing frame is barely detectable, but where the blade is fixed is about 0.23mm which translates to quite a wobble at the periphery of a 305mm sawblade.

So I conclude that the new bearings as installed are OK, but the end of the shaft is bent - how this has happened is a mystery and it is possible that it has always been so, I just don‘t know. I have been having some minor dissatisfaction with the cut sometimes and was hoping this was due to the bearing issue.

Anyway, I have enquired of NMA whether a replacement shaft is available - otherwise, I assume it is possible to get one machined.

Could do without this really.

Cheers

I feel for you. I had a similar issue with a Kity planer. Didn't realise till I started putting it all back together that the bearings have to be adjusted to the correct depth in the side retainer plates for it to go back together properly. Fortunately no heat involved but still a PITA. Great result finding a replacement shaft.