Installing a Bandsaw Riser Block

Installing a Bandsaw Riser Block

by Robert Feeser

This article first appeared in a thread on theWoodNet woodworking forum. It was compiled and reproduced here for easier public consumption. All Text are the property of Robert Feeser.

This is obviously in response to a specific question, and the question isn't here. But the response is general:

First, maybe it will make you feel better to know that when I bought my Jet 14" bandsaw (POS) 10 - 15 years ago and the Jet riser block made for that saw the alignment pins were out of position enough to be worthless. Jet at the time acknowledged the fact but said it was perfectly safe to leave the pins off. I felt uncomfortable about that, so set the riser block aside and did not install it. A couple of years ago I decided to install it and called them about it again, and was told again that that's the solution. After giving it some thought, I decided to go ahead. About a month or two ago it occurred to me to ask this forum for opinions. Do a search and you will find the thread. Everyone assured me that in their opinion it is safe; just tighten that bolt down firmly. I'm all right so far. So, I expect that's the answer you will get, though you can never tell around here.

Cast iron drills very nicely, so that would be no problem.

The question of how far off is too far depends. After you install the riser block, which of the below conditions do you want?

The wheels are parallel. Accomplishing this requires twisting the top on the riser block.
The wheels are coplanar. This requires shimming one wheel and/or shifting the top forward or backward once the wheels are parallel.
The top wheel is directly above the lower one. This requires shifting the top left or right once the wheels are parallel.
The upper side guides do not have to be readjusted when you raise or lower the guide. This requires tipping (shimming) the top left or right and then shifting it in the opposite direction to keep the top wheel directly above the lower one.
The upper rear guide does not have to be readjusted when raised or lowered. This requires tipping (shimming) the top forward or back and sliding it in the opposite direction to keep the wheels coplanar.
Blade perpendicular to the table. This requires readjusting the left to right 90 degree stop and raising (shimming) the front or back of the table.

That sounds like fun, and I can assure you that it is. I can also assure you that it is possible to accomplish all of the above simultaneously. It ain't easy, but should only have to be done once if you get that bolt really tight, and makes the saw a pleasure to use.

All the paint should be removed from the both mating surfaces on the block and top and bottom castings. Scrape and file it off. Flatten the mating surfaces as well as possible.

Shims made of aluminum cola cans are easy to use and hold up well. You can make finer adjustments sliding the top than you can by shimming, so get the shimming as close as possible and then shift the top very slightly to get the alignments dead on. That way you can get the guides so they stay within about 0.001 in. of the same position relative to the blade all the way up and down, but since you can only shim by several thousandths at a time you may have throw the position of the upper wheel relative to the lower one off a few hundredths, which matters not at all.

Of course, most of these alignments are interdependent. When you improve one you may well throw another off. You just have to keep checking all of them, correcting the one that's farthest off over and over again, bringing everything slowly into alignment. The alignments in the fore-and-aft plane tend to be independent of those in the left-right plane, but you will find that you cannot confine adjustments completely to one of those planes-there is sure to be a little bit of unavoidable movement in the other as well.

When shimming, make full shims that lay across the entire width or depth of the joint. That way if you start with a joint that is flat and doesn't rock you will continue to maintain a joint that does not rock. That doesn't seem very clear to me. Let me try it this way. Say there were four bolts in the joint, one on each corner. A good way to shim would be to make little washer shapes and place the shims around the bolts. Then what I am suggesting is always put two identical shims on at a time, always on adjacent bolts, never on diagonally opposite bolts. Put just one shim in the joint, or one on each of two diagonal bolts and you have a loose, rocking joint.

All the alignments have to be made with a blade tensioned because these saws castings deflect under the load. So how much tension? Because if you align things for one tension they will not be quite right for any other tension. You have the choice of aligning for the blade and tension you use the most, or you can align for the blade and tension you use that is most critical. In the first case, most people would tension a 1/4" blade and align with that tension. In the second, you would tension the thickest blade you will be using--the one you resaw with--because proper alignment can make a big difference when resawing.

You have to really crank that bolt down every time you check alignments because that flexes the riser block a little, too, changing alignment.

If you make the tiny movements by tapping on the riser block or the top you will probably have to tap fairly hard. Don't use a metal hammer directly on the castings; they will break. A dead blow hammer or a wood block cushion under the hammer is necessary.

So the simple answer to your question how far off for the positioning pins is too far off is it depends. If you want to just take what you get and live with that the pins can be a little of. If you want to try to align everything, I don't think it is possible to use pins at all because there is no way to position them accurately enough.

All this really makes you wish you had a saw that let you simply adjust the angle of the top guide post. It would be so much easier.

I spent about a week making these alignments on my Jet saw, spending about a half hour a day. I can only work at that kind of thing for so long at a time before I just say, "To hell with it; it's close enough." But I can come back re-energized the next day and work at it some more. Eventually you reach the point where it isn't worth it to you to try to get it any better. Happily, my end result was an alignment good enough that the guides do not have to be reset no matter how high or low I move them. I cheated and did the alignment with the tension halfway between what I use for a 3/8" blade. The wheels are coplanar and one is directly above the other. Blades track.

I have only put myself through this once; the first alignment I made (about a year and a half ago) is still holding.

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