Will bandsaw bearing guides handle small blades?

[pooka]

Jet sent me a set of these bandsaw bearing guides recently for my JWBS-14, as a result of the problems I was having with fitting blades sized according to their old (incorrect) manuals. The bearings are oriented so that the edge bears against the side of the blade (also the photo in the above link is wrong - there are double bearings on each side of the blade, rather than a single bearing, although that probably makes no difference in the context of my question).

I plan to fit the bearing guides to the machine over the next few weeks, but one question that has sprung to mind is whether I can use the same range of blades with these bearing guides as I can use with the current guide blocks? Larger blades should be fine but my concern is about my smallest blade, which is 3mm wide. Am I likely to face any problems running a 3mm blade with these bearing guides does anyone know?

Thanks.

As an aside (and at the risk of starting a religious war on the topic :wink, have people generally found bearing guides to be preferable to guide blocks? I am inclined to think they will be louder on my saw (current blocks are just made of plastic), but am curious to see if they will do a better job of guiding the blade.

 

[Guest]

I fitted those bearings on my band saw and have had no trouble at all.You will have to adjust the side bearings for different size blades but it only takes a minute or two.

 

[pooka]

Thanks jaymar.

Incidentally, have you found that these bearings have improved the performance of the saw?

 

[Garrett in Victoria BC CA]

Obviously, experience varies.

My saw (20" 3 HP) came with bearing guides. I ruined a few bands and eventually traced the problem to inadequate lateral support from the guides. First, there is very little contact surface between bearing and band to start, and that's further reduced by the need to keep the bearings well back of the teeth.

The orientation of the bearing holders enabled me to make some "cool blocks" from teak that I soaked in mineral oil for a few days and then zapped in the microwave for a minute. The teeth cut their own kerf, and the blocks provide full contact. I haven't had a problem since, and the blocks don't seem to wear much.

Cheers, Garrett

 

[GCR]

Like Garrett, I fitted "cool blocks" but purchased them from Axminster. The thrust bearing is a ball race used side on. 3mm blades run perfectly well as long as the blocks and thrust race are positioned carefully. I find the blocks quieter than the original and don't need much adjustment.

Bob

 

[pooka]

Thanks for the responses. I have been debating whether to try Cool Blocks in the saw or to fit the bearing guides - the current plastic blocks that came with the saw are not great, so either should be an improvement. I may order some Cool Blocks but try the bearings in the meantime.

I was thinking that maybe Cool Blocks (or even homemade wooden blocks as Garrett suggests) may be better with the really narrow blades as they'll potentially provide more contact area with the blade and therefore greater support, which seems to have been Garrett's experience. Mind you, once I have the bearing guides fitted I may just find that I won't want the bother of swapping back to guide blocks for the occasional use that the narrow blade will get. Time to "suck it and see" I guess.

 

[Jake]

The old-style block arrangement can also provide support closer to the cutting surface, albeit by a small amount (i.e. the bearing radius).

 

[Jarviser]

I have a Recordpower BS250 with these roller bearings fitted. The downsides I have found are:
1: The guide rollers, which are glass hard, must not go beyond the gullets or the teeth set could be flattened, which would leave you about 1 or 2 mm on a 3mm blade. Tricky to set as the bearings will have a rounded edge.
2: They look like they are metal shielded bearings (possibly 626-ZZ). I have found these fill with dust and jam up after a few months. I am currently using rubber sealed bearings (eg 626-2RS)
See thread
https://www.ukworkshop.co.uk/forums/viewtopic.php?t=6703

 

[dickm]

Does anyone know why so many bandsaws have the blade running across the <side> of the rear bearing? It seems a very odd idea, because the bearings aren't designed for a thrust in that direction, and some of the rotation is across the back of the blade. But there don't seem to be many (any?) where the blade runs against the circumference of the rear bearing, even though this seems a more rational system.
(but then, my old Startrite 352 just has a steel bar as a rear support)

 

[Scrit]

...but then, my old Startrite 352 just has a steel bar as a rear support

Yes, but isn't it beautifully simple!

Scrit

 

[Jake]

Does anyone know why so many bandsaws have the blade running across the <side> of the rear bearing? It seems a very odd idea, because the bearings aren't designed for a thrust in that direction, and some of the rotation is across the back of the blade. But there don't seem to be many (any?) where the blade runs against the circumference of the rear bearing, even though this seems a more rational system.
(but then, my old Startrite 352 just has a steel bar as a rear support)

I'm guessing that it is to increase the amount of blade support provided. Like the footprint of a car tyre, the area of the bearing touching the blade will be miniscule when touching circumferentially (to make up a word because I'm tired - pun unintentional).

I';ve always wondered whether the whole idea of bearing guides is a bit of an gimmick really - but I haven't enough experience of both to make up my mind.

 

[Scrit]

I'm guessing that it is to increase the amount of blade support provided. Like the footprint of a car tyre, the area of the bearing touching the blade will be miniscule when touching circumferentially....

If you think about it when you set up a blade properly (possibly except for cool blocks) NONE of the guides should be touching the blade at all when the saw is idling (read your saw's manual, you'll see what I mean). The purpose of the rear guide is to support the blade when you push timber through and if you're pushing the timber through so hard that you're wearing bearings out all the time either you're feeding too aggressively, the blade isn't under enough tension or your blade is dull . The side bearings are there to support the blade when making turning cuts and the reduce blade wander, although again if your blade is bowing a lot in cut then it probably isn't under enough tension. There is also (probably) a secondary safety function there as well because the blade guides do double as guards.

I've always wondered whether the whole idea of bearing guides is a bit of an gimmick really - but I haven't enough experience of both to make up my mind.

One of the best regarded professional blade guide systems, the Chaco, uses Bakelite side bearings with a bearing rear thrust, although that rear thrust does have a heavy steel "cap" over it. Older Startrite saws always had mehanite (cast iron) side thrusts with hardened steel rear thrusts - they can be noisy, but work very well, and at least you can face them off yourself if they get marked up, the only downside is that they can be a bit noisy. I find it interesting that there is a move towards ceramic guide bearings these days - a high-tech solid bearing.....

Scrit

 

[Jake]

If you think about it when you set up a blade properly (possibly except for cool blocks) NONE of the guides should be touching the blade at all when the saw is idling (read your saw's manual, you'll see what I mean).

Sure, but the guides aren't there to do nothing when the saw is idling.

The purpose of the rear guide is to support the blade when you push timber through and if you're pushing the timber through so hard that you're wearing bearings out all the time either you're feeding too aggressively, the blade isn't under enough tension or your blade is dull .

I quite agree again, but it isn't really a response to what I was saying in the bit you quoted, or if it is, I've missed your point. What I was saying was that when the blade does need support and the guides do come into play, a bearing at a right angle to the blade can give support over a greater length of the rear of the blade than one in-line with the blade.

One of the best regarded professional blade guide systems, the Chaco, uses Bakelite side bearings with a bearing rear thrust, although that rear thrust does have a heavy steel "cap" over it. Older Startrite saws always had mehanite (cast iron) side thrusts with hardened steel rear thrusts - they can be noisy, but work very well, and at least you can face them off yourself if they get marked up, the only downside is that they can be a bit noisy. I find it interesting that there is a move towards ceramic guide bearings these days - a high-tech solid bearing.....

Interesting stuff as ever, Scrit - it's great to have someone with your depth of experience on here. Hadn't noticed the ceramic guides - I guess the point being that they are self-lubricating but very hard indeed?

 

[Scrit]

Hi Jake

I probably didn't express myself very well

What I was saying was that when the blade does need support and the guides do come into play, a bearing at a right angle to the blade can give support over a greater length of the rear of the blade than one in-line with the blade.

Did you know that some older saws sometimes had only a top bearing set with the bottom set being optional? Whilst the rear bearing is there to support the blade in extremis I don't feel it should be regarded as an essential. With the exception of really fine blades I still feel that if you are bearing heavily on the rear thrust bearings then either your blade isn't sufficiently tensioned, your blade is dull or you are feeding too quickly. The main function of that bearing therefore is to prevent you from pushing the blades off the wheels, in which case you shouldn't expect to run against it at all times. I'd say that this is even the case in small shop/home shop bandsaws despite the fact that few of them can get the sort of beam strength (tension) that is needed for optimum cutting thus making blade deformation in cut more likely.

Very narrow blades (e.g. 3mm) pose a different problem in that in order to generate sufficient beam strength in the blade to overcome the tendency to bow in cut you'd need to put the blade under so much tension that it would quite possibly snap before you even made your cut. In that instance you have to run under tension and have a rear thrust support.

The larger the contact surface area of the rear thrust bearing the less likely the blade is to deform - two bearings running with the bearing sleeve against the back of the blade, Carter style, provide you with just two contact points - two bearings running side on, Euro style, provide you with a much longer contact patch or two patches per bearing and theoretically should allow the blade to deflect much less, and is is deflection which kills blades. I believe that the bearings inside the Euro style thrust bearings are thrust bearings in any case. I have to admitm, though, that this is merely personal preference.

BTW the ceramic guides were oroiginally offered by Laguna in the States but are now appearing on Italian machines such as ACM and Centauro as well.

Scrit

 

[bob_c]

I have a Jet /axminster smallish bandsaw which had what looks like metal blocks for the sides.i replaced them with similar size bronze ones which i made on my small mill,the rear bearing is a right pain and if i feed anything too heavy the blade beds into the bearing and seazes.I havent figured a suitable way to replace the rear bearing yet,with something better.I dont really see the point of the rear bearing and how its supposed to work.

 

[beech1948]

Hi,
I have a Startrite 352 which has solid Metanite bearing surfaces. These are triangular in shape with the long edge facing the blade. The rear thrust support is a steel round bar with a very hard tip of about 8 mm in length and of about 6 mm diameter.

If your in a hurry it can be a bit tectchy to set up for a new blade BUT the bearing surfaces provide a longer and more stable edge than circular bearing now in fashion. I have them for both top and bottom bearings so there is maybe 22 mm of support top and bottom. Circular bearings only provide a minute amount of support.

Drawbacks are only that care needs to be taken to prevent the Metanite bearings surfaces from being gouged.

I have only once had to use the Scary Sharp method to dress these and that was some 6 years ago when I bought it.

I do wonder if the modern circular bearings are simply fashionable rather than the most practical.

By the way my 352 cuts straight, has no drift, does not break bands, does not dull bands other than by sawing wood, is quiet and simply works just fine. Sorry to gloat.

regards
alan

 

[Jarviser]

Who woke me up with an enchanted notification?

My opinion on ballbearing guides after a couple of years - Ruddy noisy, especially when you get softwood resin making their surfaces lumpy.

The sealed bearings are much better than the ones supplied, but brass or coolblock rubbing guides are far superior.

Back into the teapot for me.

zzzzzzzzzz.

 

[Digit]

Does anyone know why so many bandsaws have the blade running across the <side> of the rear bearing?

Yes! It's cheaper that way! On large pro machines the blade runs on the rolling face of the bearing, the logical way.
My saw's guides were useless when I got it (Cheap, non runner) and I had to make guides, running the blade on the face of the bearing was immediately rejected as a non-starter, but ended up that way anyway!
What tends to happen is that, eventually saw dust gets into the bearing and it stops rotating, the result is that a groove is cut across the bearing and it never rotates again.
If you have that system the bearing can be turned back to front if you can get it cleaned and running again.

Roy.

 

[Jarviser]

eventually saw dust gets into the bearing and it stops rotating,

There is a fix if you can find sealed versions - e.g. on ebay

http://www.jarviser.co.uk/jarviser/tools5.html

 

[Digit]

The sealed ones don't keep the dust out for ever, just delay the inevitable, unfortunately.

Roy.