Bandsaw Squeal

[BuckeyeDennis]

IIUC, you maintained solid contact of the inner races to each other, and decreased the outer race clearance by shimming with tape.

AIUI that would decrease 'wobble' of the outer races and create a consistent width of the 'groove' between the bearings(blade 'slot') which is likely wider than when the bearings were new.

This is similar to Bill Mayo's use of shims between the home brew upper and lower blade dual bearings, but his shimmed the inner races as well thus also increasing the groove width.

My thinking is add a pop can shim or two(0.003 each) that has a clearance hole in the center to clear the inner races.

I will try that when the squeak appears.

You do understand correctly, and explained it much more succinctly than I!

As for the shim material, anything of the proper thickness will space the outer bearing races correctly. The tape may also have better vibration-damping properties. I seem to recall a similar film material being used underneath brake pads to combat brake squeal. Regardless, it sure is easy to apply!

If anyone tries this, be sure not to use too thick of a shim. In my case, the difference in rolling drag with a 0.004" shim and a 0.006" shim was pretty large. Too much rolling drag, and the bandsaw blade will just slide on the outer races, instead of turning them. Probably making yet another squealing noise!

[dusty]

Would it have the same effect using shim washers on ONLY the inner (smaller) races.

[BuckeyeDennis]

Would it have the same effect using shim washers on ONLY the inner (smaller) races.

No, that wouldn't take the play out of the bearings. Ball beaings are manufactured with just a bit of extra space between the balls and the races. This freeplay is normally taken up by pre-loading them when installed. Shimming the outer races (with the inner races clamped together by the shoulder bolt) will take the play out, but shimming just the inner races will not. It would, however, widen the gap between the outer races, so that the bandsaw blade could go in deeper. That may or may not affect the squealing.

[JPG]

Would it have the same effect using shim washers on ONLY the inner (smaller) races.

I think not. It could increase the propensity to wobble while increasing the 'groove' width. Perhaps allowing the blade to 'penetrate' the groove further would lessen the opportunity to squeal. Adding shims between the inner races would allow the blade to contact a different area on the outer surface of the bearing (in de groove).

Tis a balancing act between surface friction on the outer surface of he bearings(groove), inner friction of the balls and races and surface of the back of the blade as well as consistent contact between the blade and the groove. Any tendency for the blade to slide on the bearings will increase the potential for 'squeak'.

I believe this is the first time a well documented approach has achieved some success albeit it remains to be seen how durable it is. I think better understanding of the squeal cause has resulted.

I wonder(as apparently Dusty as well) if Bill Mayo's shimming the home brew guide bearings has eliminated squeal there(most relevant would be the lower bearing which serves the same purpose as the rear guide bearing).

An interesting experiment would be to scuff up the bevel on the bearing(groove) to see if increasing the friction there would have a positive effect on minimizing squeal. Alas, mine don't squeal so I cannot!:)

[billmayo]

I think not. It could increase the propensity to wobble while increasing the 'groove' width. Perhaps allowing the blade to 'penetrate' the groove further would lessen the opportunity to squeal. Adding shims between the inner races would allow the blade to contact a different area on the outer surface of the bearing (in de groove).

Tis a balancing act between surface friction on the outer surface of he bearings(groove), inner friction of the balls and races and surface of the back of the blade as well as consistent contact between the blade and the groove. Any tendency for the blade to slide on the bearings will increase the potential for 'squeak'.

I believe this is the first time a well documented approach has achieved some success albeit it remains to be seen how durable it is. I think better understanding of the squeal cause has resulted.

I wonder(as apparently Dusty as well) if Bill Mayo's shimming the home brew guide bearings has eliminated squeal there(most relevant would be the lower bearing which serves the same purpose as the rear guide bearing).

An interesting experiment would be to scuff up the bevel on the bearing(groove) to see if increasing the friction there would have a positive effect on minimizing squeal. Alas, mine don't squeal so I cannot!:)

The shim from the roller bushing is .012" that I use between the two bearings. I never tried any other thickness as these were available from the roller bushings. I lightly honed the back edges of the bandsaw blade so that the blade rode a few thousands down between the bearings. I always used ABEC3 rated bearings which was a higher quality bearing than the original bearings. I operated several different bandsaws myself for many years without any squeals or noise from this bearing setup. I found this setup worked well for narrow blades that I used to saw somewhat sharp curves and circles. I have installed this setup on a few dozen bandsaws. The customers never came back to me with any problems with their bandsaws. I did take the time to insure the bearing groove always aligned with the back of the bandsaw blade. Sometimes, this took a few adjustment attempts for the blade guides bearings to be aligned with the blade. I found any bearings with squealing problems always needed replacement due to wear and poor bearing quality.

[dusty]

I thought that both of my bandsaws were of the double bearing configuration but they are not. I went to the shop this morning to shim some bearings on a squealing bandsaw only to discover that it has the single but wider bearings (I think that is the original configuration).

Well, dual bearings or no, I still have the squeal which was isolated to the lower backup bearing (right side). I confirmed that by applying pressure to the back side of the bearing. No spin, no squeal.

Inspection shows that the bearing has been grooved by the saw blade so I moved the bearing by shimming it. The blade now tracks in a different location (not centered on the bearing face).

No squeal. Some noise but no squeal.

Is there a technical reason why this bearing, which has virtually no loading, needs to be centered on the blade?

BTW, some of you may think you understand this squeal thing but I sure don't and I have had the issue for years and worked to eliminate it many times. I usually give up because the squeal is not much worse than the noise contributed by the Power Station (which is where I normally operate my bandsaw).

[BuckeyeDennis]

I thought that both of my bandsaws were of the double bearing configuration but they are not. I went to the shop this morning to shim some bearings on a squealing bandsaw only to discover that it has the single but wider bearings (I think that is the original configuration).

Well, dual bearings or no, I still have the squeal which was isolated to the lower backup bearing (right side). I confirmed that by applying pressure to the back side of the bearing. No spin, no squeal.

Inspection shows that the bearing has been grooved by the saw blade so I moved the bearing by shimming it. The blade now tracks in a different location (not centered on the bearing face).

No squeal. Some noise but no squeal.

Is there a technical reason why this bearing, which has virtually no loading, needs to be centered on the blade?

BTW, some of you may think you understand this squeal thing but I sure don't and I have had the issue for years and worked to eliminate it many times. I usually give up because the squael is not much worse than the noise contributed by the Power Station (which is where I normally operate my bandsaw).

Your question motivated me to do a Google search, and I found a pretty good paper on bearing noise published by NSK. It turns out that even they have a limited understanding of various bearing noises. Here's what they have to say about "squeal noise":

3.1.3 Squeal noise
Squeal noise is a metallic noise that can be rather loud in some cases. It sounds like metal sliding on metal and we express it in Japanese as “kyuru kyuru.” With squeal noise, bearing temperature does not generally rise and
bearing and grease life are not adversely affected. In fact, beyond the noise problem (if indeed it is actually a problem), there is no other hindrance to bearing operation.

Squeal noise tends to occur with relatively large bearings used under a radial load. It occurs frequently in cylindrical roller bearings, but may also occur in ball bearings. The characteristics of squeal noise are:
(1) It tends to occur when radial clearance is large.
(2) It occurs mostly with grease lubrication and only rarely with oil lubrication.
(3) It occurs more often in winter.
(4) It occurs within a certain speed range that tends to become lower as bearing size increases.
(5) Its generation is inconsistent and unpredictable, and depends on the kind and amount of grease, as well as bearing operating conditions.

Influenced by the lubrication used and increasing vibration of the outer ring, the friction between the outer ring and rolling elements is considered to be the cause of squeal noise. Squeal noise is attributed to self-induced
vibration related to lubrication. However, there is an important question: From what part of the circumference of the outer ring is squeal noise emitted? The jury is still out on this question as some experts believe the noise is generated in the load zone while others argue that it is generated in the no-load zone. Effective countermeasures to squeal noise include reducing the radial clearance and employing a very shallow groove in the outer ring raceway of the bearing.

Here's the whole paper, complete with pretty illustrations .. it covers a LOT of different types of bearing noises. [ATTACH]23157[/ATTACH]

So the bearing is acting sorta like a violin string, and the bandsaw blade like a violin bow. How the bearing vibrates depends on where you press it, and how you excite it. If the vibrations are at audio frequencies, they make sound waves that we can hear.

I didn't try it on my bandsaw, but it would be interesting to see if the squeal happens only at certain blade speeds.

[JPG]

Dusty I cannot think of a reason for the lower guide bearing to be centered on the blade other than to prevent the blade applying an uneven load to the bearing, but I cannot think of a reason that would matter.

I think the squeal is created by the blade skewing on the bearing. Moving it to a new 'contact' area should change the friction and possibly alter the squeal conditions.

The NSK stuff above implies an internal noise source likely caused by the balls scraping the races rather than rolling on them. I think in our case, the blade scrapes the bearing outer surface of the outer ring.

Question is, is it an alignment issue, a load issue(internal friction makes blade sliding more likely) and would smoother or rougher outer surface alter the squeal?

[BuckeyeDennis]

A new thread on bandsaw bearing squeal reminded me of this one. Time for an update.

Over two years have passed since I placed a 0.004" packing-tape ring shim between the outer races of my SS-issue auto-track bearings. The squeal has never recurred.

[JPG]

A new thread on bandsaw bearing squeal reminded me of this one. Time for an update.

Over two years have passed since I placed a 0.004" packing-tape ring shim between the outer races of my SS-issue auto-track bearings. The squeal has never recurred.

So the outer races were 'scrubbing'?