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Forum topic by Hajimasabi posted 01-31-2011 09:13 AM 1594 views 2 times favorited 11 replies Add to Favorites Watch
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Hajimasabi

4 posts in 2140 days


01-31-2011 09:13 AM

The blade on my contractor saw is dead parallel to the fence at 90 vertical, but the rear of the blade is .22” closer to the fence than the front when tilted to 45. I’ve read a few articles on how to shim the trunnion to fix this, but when I do the math as described here I come up with a vertical shim of half and inch! The distance between the trunnions is 18” and the measuring distance across the blade is 7”. If it matters, its a right tilt saw and I’m measuring from the left miter slot.

Am I doing something wrong? Can .5” be correct and if so, do I risk screwing up my saw by shimming the front trunnion that much? Seems like I might risk throwing things out of whack with respect tot he hand wheels etc.
Thanks


11 replies so far

View Mark Shymanski's profile

Mark Shymanski

5314 posts in 3179 days


#1 posted 02-02-2011 06:02 AM

Almost a quarter of an inch out?! Is your fence square to the tables mitre slots? Is the blade square to the mitre slots? I would check these before I started shimming the trunions. Some photos of what you are working with would help figure out what is going on.

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

View Don's profile

Don

514 posts in 2540 days


#2 posted 02-02-2011 07:41 AM

double check your math. .5” is a lot to be out.
And use the miter slot as a reference, not the fence.

-- Don - I wood work if I could. Redmond WA.

View RetiredCoastie's profile

RetiredCoastie

999 posts in 2650 days


#3 posted 02-02-2011 09:04 AM

Like Mark & Don suggest your miter slot needs to be squared to the blade first, and then square the fence to the blade.

-- www.thepatriotwoodworker.com Proud Supporter of Homes For Our Troops

View IrreverentJack's profile

IrreverentJack

724 posts in 2310 days


#4 posted 02-02-2011 01:22 PM

The trunnions are aligned on two planes. First vertically, with the miter slots, and then horizontally with the table. IMHO these are best sites for table saw allignment. Saw alignment has been a popular topic here. . I’ve used these and found them very helpful. Good luck. -Jack

View docholladay's profile

docholladay

1287 posts in 2526 days


#5 posted 02-02-2011 02:07 PM

The first question that I ask is whether your saw is a genuine contractor saw with cast iron table and the motr hanging off the back of the saw or are we refering to a job site type saw with the universal motor enclosed in the plastic body of the saw. Usually with some sort of aluminum alloy table top. Still, the first thing to do is to begin by making sure that the blade is parallel to the miter slots. Depending on the type of saw this might be adjusted differently, but this is an absolute. The blade needs to be perfectly parallel to the miter slots. Then you also match the fence to the miter slots. If those are dead on and you still have that much of an error, I would then contact the manufacturer because you probably have a much bigger problem than just alignment. If the saw is new/recently purchased, I would simply take it back for refund or exchange. If not new, then I would find out where the nearest authorized service center is and take the saw there.

Doc

-- Hey, woodworking ain't brain surgery. Just do something and keep trying till you get it. Doc

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Hajimasabi

4 posts in 2140 days


#6 posted 02-02-2011 06:46 PM

The saw is a contractor saw with motor hanging out the back and a heavy cast iron table. The blade is perfectly aligned parallel to the miter slot (and fence) within .001”. It’s an older off-brand saw that I bought on craigslist a year or so ago. I believe its called a Transpower. It’s been a great saw and came with a Beismeyer fence that was worth more than I paid for the saw. To be honest, I can’t believe I never noticed that it was out on the 45 by so much. I haven’t done a lot of miter work with it.

I’m measuring with dial indicator mounted to my incra miter fence with the pin at a 90 degree angle to the blade. Measuring from the left miter slot to the blade, there is a .220” difference (yes I triple checked this) from the front to the back of the blade with the back being further from the slot. I marked a spot on the blade and rotated it, measuring from the same stop to remove an error from the blade being out of true. The dist across the blade is 7” and the trunions are 18” apart. If I’m doing the math right, shim thickness should be:
.220/7*18=.56”

View Radu's profile

Radu

324 posts in 2510 days


#7 posted 02-02-2011 07:56 PM

I think I know what kind of saw you have. Just see if you have any bowing or sucking in of the metal side of the saw cabinet when you tilt the blade. There were some discussions here that might help you: http://lumberjocks.com/topics/20420; http://lumberjocks.com/topics/20191. And here is a fix http://lumberjocks.com/projects/37469 (check pics 4 & 5). Thanks to original posters.

View DrDirt's profile

DrDirt

4169 posts in 3209 days


#8 posted 02-02-2011 08:34 PM

I think there is something fundamentally wrong to be that far out.
Is it possible that the casting is cracked, that when the trunion hits the 45degree stop there is some kind of flex (or opening of a break)?

Easy check might be to tilt to 30 degrees and lock it, then see if you get an ‘intermediate’ value between 0.001@0 degree tilt to the 0.220” at 45.
being out a almost a quarter inch from front to back on a saw with only a 7 inch blade would be completely unusable and dangerous, not just give you poor/burned cuts.

I think your geometry calculation is right, but there is something major wrong with the saw to be so far off.

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

View Gofor's profile

Gofor

470 posts in 3254 days


#9 posted 02-03-2011 05:05 AM

First: Validate your technique: Using a machinist scale laying flat on the table and the end square and flush to the fence or edge of miter slot, measure the corner of the selected tooth to the fence. Rotate blade to back and remeasure. If it does not show almost 1/4” difference with the blade at 45 degrees, your technique with the dial indicator is flawed. Any change in the elevation of the dial indicator tip when moved will throw a major discrepancy in your measurement.

If the blade is indeed out, then back off the 45 degree stop so that it is not inducing any stress wracking in the trunnion. Do the same with the 90. If the trunnion is wracked against either stop, your measurements relative to each other are not reliable, as the wracking is in opposite directions. Redo the measurements, setting the blade angle with a wixey guage (Set vertical to the table over the arbor for both measurements) or with a handle piece of a combination square setting against the flat of the blade and over the arbor. Use the machinist scale to validate the dial indicator measurements somewhat. (accuracy with a machinist scale is only about .005”)

If wracking is the problem, forget the stops. You will have to reset the angle by measurement every time you change the bevel. Age and wear have taken their toll. Set them to where they apply no stress when the bevel is achieved.

If it is still out, then shimming the trunnion may or may not help. It depends on if the guides that the trunnion registers on when beveling are worn, mal-machined, or just crudded up with debris. Debris can be cleaned, the others probably cannot be corrected. (Don’t know without seeing the saw)

Good luck.

Go

PS. I noticed this is a right tilt saw and you aligned the blade to the left miter slot. If this is the primary slot in which you use the miter gauge, good on ya. If not, realign to the one you most commonly use. The only reason for aligning the blade to the miter slot is for the use of the miter gauge. Most slots are not exactly parallel. I see many people who have left tilt saws who align their saws to the right slot, because that is where the fence sits, so they then align the fence. They then wonder why the miter gauge seems to be off a smidgeon when they use it in the left slot, which was never referenced in any of the adjustments.

-- Go http://ncwoodworker.net/pp/showgallery.php?cat=500&ppuser=730

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Hajimasabi

4 posts in 2140 days


#10 posted 02-07-2011 08:47 PM

Ok, I figured it out. What had happened was that the rear bracket was loose and had allowed the trunion to actually slip partially out of the groove throwing the blade way out of whack. Glad I caught this as it seems horribly unsafe. Hate to think what would could have happened if it slipped all the way out. When I got it all put together, it was still out by .02 on the 45 which required some shims but not a quarter inch worth.

I ended up taking the whole thing apart to the nuts and cleaning & relubricating the whole mechanism while I was at it. I have to say, the whole process of aligning the blade was the single most frustrating activity I’ve ever encountered in the shop. I managed to get it within .001 on the verticle and .008 on the 45 which was good enough for me after 5 hours of contortions under the saw.

Thanks for all the helpful tips.

View teejk's profile

teejk

1215 posts in 2151 days


#11 posted 02-07-2011 11:53 PM

haji…hope you used some locktite on the bolts when you put it back together!

5 hours on a TS comes in just a little over of replacing jointer knives or trying to align tables on a portable planer so get used to it!

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