Bandsaw Blade Tracking Adjustments Etc.

[JPG]

I am creating this thread as an effort to demystify what to me is a very persnickity, difficult to successfully complete without losing yer religion effort.

I dare say there are many units out there which are not properly adjusted and IMHO much of the problems with resawing are made worse because of that lack of proper blade tracking.

This is not a cure-all, since the blade itself can cause problems, but if tracking is adjusted properly the blade will be the only thing screwing things up!

I solicit comments/admonitions/suggestions that will help myself and any one reading this to better understand and perform these adjustments.

I will also attempt to provide descriptions of how some of these assemblies are constructed so one may better understand why the 'procedure' is as it is.

I will begin with the blade tension scale adjustment, then the tracking bearings, then the lower blade backup bearing, and finally the upper blade guide and backup bearing. All but the last are relatively simple and straight forward, but the last is where all the 'issues' reside.

This may take a few days to complete, so please be patient. It will require some disassembly(so as to better illustrate adjustments and show 'internals' of parts being adjusted).

The SS bandsaw wheels are beveled with the rear/inner edge having a slightly larger diameter than the front/outer edge(ignoring the larger lip). The upper wheel is canted(top inward). When canted correctly, the back edge of the blade will track about 1/4" from the rear edge of the wheels and/or 1/8" from the back edge of a correctly installed tire. That should be true for both the upper and the lower wheels. Added 10-15-16

I will create an index here for future quick referencing.

Post 1 Blade Tension scale adjustment.

Post 2 Tracking bearing adjustment.

Post 3 Lower blade backup bearing(s) Adjustment.

Post 4 Lower Blade Backup Bearing(s) Adjustment(cont'd)

Post 5 Upper Blade Post(description only)

Post 6 Post Parallel to Blade Adjustments

Post 7 Upper Backup Bearing After Adjustments


The following adjustment is done with the blade removed and the tension adjustment screw backed out so as to make the upper wheel and scale and spring free floating.

Tension scale slack

tension bar slack.jpg (363.92 KiB) Viewed 38263 times

Note the back edge of the spring bar(red) is out from the edge of the scale.

Tension scale adjusted

tension bar adjusted.jpg (274.83 KiB) Viewed 38235 times

The scale is moved so that that edge is along the back edge of the spring bar. I find it interesting that the bottom edge of the scale also aligns with that edge.

While holding the scale aligned with the spring bar edge, securely tighten the screw.

Edited 8/17/15 to reconcile new attachment procedure.

Added blade tracking with proper cant dimenions 10-15-16.

[JPG]

The tracking bearing is one of the things that makes the ss bandsaw unique. It eliminates having to tweak tracking when changing blades and is automatic once adjusted. It also means the back of ALL blades regardless of size will run in the same location so that the blade backup bearings do not need to be readjusted either.

Blade slack

blade slack.jpg (267.27 KiB) Viewed 38258 times

Notice that when the blade is not tensioned(slack) it bulges out away from the wheel.

Tracking Bearings adjusted

tracking bearings alignment.jpg (343.91 KiB) Viewed 38244 times

In this step and all that follow, the blade is installed and properly tensioned for its size. This is to insure that all adjustments referencing the blade are with the blade positioned in a path tangent to both upper and lower wheels(both front and back.)

There are two goals for this adjustment. The obvious one is to position the dual bearings so that the blade tracks in the groove between them. The less obvious one is to make sure the blade is parallel to the sides of the bearings. That also causes the axis of rotation of the bearings to be perpendicular to the blade path(the bearing mounting bolt).

This is accomplished by loosening the bolt that secures the bracket and moving/rotating(slightly) the bracket.

Rotation is limited by a slot in the bracket that slips over a rib.

I test the centering by pulling the blade away from the bearings down near the lower wheel, then when rotating the wheels, observing the bearings moving as the blade returns to touching them. Both should start turning simultaneously.

When ya get it aligned, securely tighten the bracket mounting bolt, then recheck to make sure nothing shifted while tightening it.

We be assuming the bearing mounting bolt is NOT loose etc.

Edited 8/17/15.

[JPG]

The lower backup bearing is located below the table behind the blade.

Actually it is a lower wheel guide bearing that does the same as the upper wheel guide bearing.

Lower Bearing Bracket Mounting Screw

lower bearing mounting screw.jpg (377.3 KiB) Viewed 38203 times

This screw secures the bracket that must be positioned so that the blade rides in the center of the bearing.

Lower Bearing Bracket Slots

lower bearing mounting slot.jpg (608.73 KiB) Viewed 38254 times

The screw passes trough the slot indicated. The elongated slot allows positioning the bracket towards and away from the throat of the bandsaw. Notice the second slot.

The arrow also points to a deformation of the bracket caused by some PO(Gorilla type) really tightening the bracket mounting screw. The resulting depression makes sliding the bracket difficult.

Lower Bearing Bracket Stud

lower bearing mounting stud.jpg (617.45 KiB) Viewed 38090 times

That second slot rides over the fixed stud

Backup bearings

lower bearing types.jpg (616.84 KiB) Viewed 38067 times

The single OEM bearing is 7mm x 22mm x 10mm. The modified two bearing set is two 7mm x 22mm x 7mm. The original bearing mounting screw has an unthreaded shoulder that is 7mm od. A different scheme used by others uses 1/4" shouldered screws and bushings with 8mm id bearings(8mm x 22m x 7mm. The intended result is to center the blade on the bearing(s). The double bearing sets provide a groove for the back of the blade to ride in(just like the guide bearings). A better choice would be 7 x 22 x 5mm bearings, but they do not exist!

NOTE: The blade did/does not center on the original bearing. With the dual bearings, they must center to the blade.

This procedure will be demonstrated using the dual bearing set shown, but if the OEM single bearing were being used, the procedure would simply be to center the blade on it.

Since the dual bearing set is wider(14mm) than the OEM one(10mm) the bearings must be mounted differently. The lock washer normally between the single bearing and the tapped hole in the bracket must be left out so as to position the bearings towards the outside of the bandsaw. A jam nut(added) on the end of the screw serves to lock the screw in place.

Edited 8/17/15

[JPG]

Continuing the description of the parts to be adjusted.

Bracket mounting slots

lower bearing bracket slots.jpg (543.62 KiB) Viewed 38005 times

The file marks shown here and elsewhere are the result of filing those surfaces flat(free of burrs etc.).

Interference potential

lower bearing interference.jpg (418.95 KiB) Viewed 37961 times

With the wider dual bearing bearings that mount closer to the bracket(no lockwasher) the bearings may butt up against the bracket. This area of the bracket is usually not close to the single(narrower) bearing. There is considerable flash on the corners that must be removed to increase the clearance. The dual bearing set requires the bracket be positioned 2mm further in. This also places the bracket near the limit of the adjustment range(slot end).

Bearing screw mounting surface

lower bearing screw hole.jpg (524.36 KiB) Viewed 37898 times

Here also the bracket surface needs to be flat. Der gorilla caused this to be deformed also.

Adjustment done

lower bearing aligned.jpg (601.02 KiB) Viewed 37883 times

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After all this parts description, the actual adjustment is simple. Merely position the bracket so the blade is centered(groove on dual bearing or center of single bearing).

Again centering on the dual bearings is tested by pulling the blade out and rotating the wheels until the blade once again contacts the bearings. The blade should contact both bearings simultaneously(that implies the blade does not snap into the groove from either side). I recommend temporarily increasing the blade tension while checking this to ensure the blade is straight between the two wheels.

Edited 8/17/15

[JPG]

First let's take a look at the post up/down lock.

Post locking rod

upper post lock nest.jpg (207.26 KiB) Viewed 37761 times

The flatted lock shaft rides on several ribs inside the back side of the post. When the red handle is rotated, the shaft moves from the round side pressing against the lock spring to the flat side just clearing the spring.

Rod in unlocked position

upper post unlocked 2.jpg (591.04 KiB) Viewed 37791 times

Rod in locked position

upper post locked 2.jpg (584.45 KiB) Viewed 37773 times

Locking spring tension adjusting screw

upper bearing post tension.jpg (422.56 KiB) Viewed 37747 times

This screw has a slot in the end opposite to the head. The head presses against the spring on one end, and the other end of the spring presses against a rib in the base casting. Rotating the screw clockwise decreases tension. As the post front/back parallel to blade screws are adjusted(see next post), the tension may need to be readjusted. Those two screws press against the side of the post opposite to the spring.

I recommend waxing the lock rod.

Edited 5/17/15

[JPG]

The first adjustment is to align the upper backup bearing(s) to the blade and simultaneously position the post parallel to the blade from top to bottom of the post.

I recommend you remove the upper wheel retaining clip and washer so that you can easily remove and replace the wheel so as to eliminate its getting in the way. It will ride on the back side due to the cant, so it is not necessary to replace the clip and washer until you are completely finished.(tensioning and rotation are not affected by the 'missing' clip and washer).


Anti slop screw

upper bearing adj screws.jpg (500.43 KiB) Viewed 37734 times

Notice the screw with a jam nut. This screw is adjusted to allow the post to move up/down in the bracket with no slop, but also without dragging. Your bandsaw may not have this or the screw may vary. After adjusting, tighten the jam nut and recheck the post for binding.
FWIW this is more easily done with the post and bracket out of the bandsaw and in your hands.

Post mounting bracket adjustment slots.

upper anti slop screw.jpg (444.2 KiB) Viewed 37768 times

The bracket mounting screws are inserted through the slots and are threaded into the base casting. The slots allow left/right movement of the bracket, but also allow the bracket to rotate.

Therefore two things must be observed when adjusting the bracket.
1) Centering the blade on either the center of a single bearing or the groove between a dual bearing setup.(actually we are centering the bearing to the blade).
2) The post(installed in the bracket) being parallel to the back of the blade. This parallelism is verified by checking for the blade centered(to the bearing(s) with the post moved both at a low position and near the top. The backup bearing should not touch the blade, but needs to be close to enable seeing this. The next adjustment will set the blade clearance of the bearing at both top and bottom, but if clearance is excessive at either the top or bottom position, you may need to adjust that then come back and complete this adjustment.

The next adjustment is where difficulty ensues! The next two pix illustrate what is inside the bracket, and how the adjustments position the sliding position of the post as it is raised/lowered.

Outer side of post slot

upper slide guide 1.jpg (482.91 KiB) Viewed 37701 times

Notice the two raised surfaces indicated by the two arrows. The post slides on these two surfaces.

Inner side of post slot

upper slide guide 2.jpg (505.14 KiB) Viewed 37687 times

Notice the double arrows again. The post would slide on those two surfaces, but if the anti-slop screw is present(see the single arrow), the post rides against it.

Notice the two brass screws. They are to be adjusted next. The tension spring is rotated away from the slot in these pix, but normally it is positioned across the post slot. The two brass screws are adjusted to position the post in the slot so that when the post is raised or lowered, the post(and attached backup bearing) remain the same distance from the back side of the blade. Thus the back side of the post presses against the lock spring, and the front surface of the post rests on the two brass screws.

The tricky part is to maintain no front to rear slop when adjusting the brass screws. If one is backed out 1/4 turn, the other must also be turned in 1/4 turn.

The adjustments are checked by observing the same distance from the back of the blade to the backup bearing(s). This should be checked with the lock set. It may become necessary to readjust the tension on the spring during this.

All adjustments should be made very gradually (no more than 1/4 turn). The jam nuts must be loosened and snugged as each adjustment is made(loosen nut, adjust screw, snug nut).


To increase the clearance at the top, back the lower screw out, and run the top screw in.

Realize all the movement of the two screws affects the blade to bearing clearance at both the top and bottom positions of the post. You are 'tilting' the post.


A different description of this adjustment is found at post #60 in this thread. Thanks Ed!!!



As a side note, the next pix shows the screw that attaches the two parts of the post to each other.

upper post screw.jpg (620.31 KiB) Viewed 37707 times

I would be a good idea to go back to the beginning and verify all adjustments are still correct. As with the lower bearing adjustments, I recommend more than 'normal' tension on the blade to again ensure the blade is tangent between both the upper and the lower wheel.


Table to blade and guide to blade adjustments are beyond the intended scope of this thread, but are no less important nor less necessary than those included.


5/22/14 Added link to Ed's description.
8/17/15 edited pix

[JPG]

These pix show the position of the backup bearings relative to the back of the blade when adjustments are completed.

The first two pix show the bearing with the post raised almost to the top limit.

UPPER BEARING CENTERED.jpg (463.94 KiB) Viewed 37623 times

UPPER BEARING CLEAR.jpg (472.26 KiB) Viewed 37623 times

Upper position blade centered and clearance


The last two pix show the bearing with the post lowered almost to the table.

UPPER BEARING CENTERED AT BOTTOM.jpg (413.48 KiB) Viewed 37599 times

UPPER BEARING CLEAR AT BOTTOM.jpg (436.56 KiB) Viewed 37593 times

Lower position blade centered and clearance

The back of the blades are not perfectly straight. This one brushes against the bearings a couple of places around the blade.

Edit 8/17/15

[bvrsbro]

Thanks for this thread, this will help me tweak my bandsaw.

[dusty]

Thanks for this thread, this will help me tweak my bandsaw.

Tweaking is sometimes not a good thing. If your bandsaw needs tweaking, this thread is an excellent tutorial but if your bandsaw is already tuned - this thread and the tutorial could have you saying words the kids best not hear.

If done from scratch, bandsaw alignment can be an all day task.

Good luck with your tweaks.

[Gene Howe]

This goes in my favorites for that time when mine does need tweaking.
Thanks for all your work, JPG.