Why are my rips off?

[davidtu]

I just did some rips using a new Leitz made Irwin 24T rip blade and the results were really poor. Mainly I was trimming a small amount (varried between ~1/8"-1") off the sides of pieces that are just over a foot long and are about 6-7" wide. When I placed the ripped edge alongside a straightedge it seems that the cut wasn't really straight, but rather curved inwards... thus creating a concave edge... it's only off by 1/32-1/64 depending to the piece, but its definitely not straight. Was using a featherboard, btw.

I later did rips of some scrap pieces and had the same effect... these pieces were narrow (4" or so) but much longer (2-3') and I cut them in half or so. Same or similar problems.

What is this a symptom of? Are the pieces too short? (If so what is the correct way to make the cut?) Am I not pushing the piece in the right spot & causing it to curve? (Where should I be applying push pressure?) Is there a blade issue? Setup issue? (Checked saw setup... found blade just a hair off perpendicular to the table, measured fence from blade back 1/32 further than front)

Thanks!

[LJR]

I think for that to happen something has to move during the cut. The fence or the board or the sawblade. Fence is easy enough to check - does it lock down solidly. Board movement during the cut is a matter of technique and featherboards.

Blade flexing during the cut? A thin kerf blade is more prone to do this than a "standard" kerf. Try a different blade and see if your results change. If you have a blade that's flexing that much it may need to be run with a stiffener all the time.

[Ken Massingale]

Have you put a straightedge against the rip fence, David? There have been reports of a couple of rip fences with slight curves.

[Imadunatic]

Is your stock unstable or a touch moist? I do almost all my ripping with that blade with fantastic results. I have ripped 10/4 Red Oak with a little burning but the cut was still relatively straight. I would be interested to hear what the problem is if you track it down.

Kevin

[Ken Weaver]

In addition to what they've said, is the side of the board against the fence true? In other words you need a reference side that is flat and square. If the reference edge is concave, the cut edge won't be true.

[cabinetman]

I gave Bruce this advice.
The series of steps for "alignment" are about all you can do without changing the curvature of the Earth.

First, with the saw unplugged, run the blade all the way up. Next, mark a tooth and roll it to the front near the table. Measure the distance to the edge of the slot or a line built into the table that runs from the front of the saw to the rear. Next, roll the sawblade to the rear of the table and measure to the same place. If there is a discrepency of any sort, you'll have to adjust the table to the blade, or the arbor to the table, whichever ability the brand of saw allows you.

Once that is completed, while the blade is still in it's up position, measure the same tooth at the front to the locked down fence, and at the rear of the fence with the same tooth. That measurement should be the same. If it isn't, adjust the fence so that it is.

After this is all done, you can perform this all over again with a different tooth that is 180 deg from the one you first used. If it is out, you have runout.

Don't totally disregard the option of changing the curvature of the Earth.

Good luck, and keep us posted.



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

[LCHIEN]

something has to be moving. If you kept the piece against the fence (And I recommend gently but firmly against the fence, not "hard" against the fence.) - then the culprit is usually the rip fence.

The blade flexing? Hard to believe even for a thin kerf. Spinning at 5000 RPM should keep it pretty flat (picture the spinning Pizza dough, it wants to flatten out when hand spun). Stiffener? Don't think so, a stiffener for a rip blade is ridiculous what with the loss of cut depth.

Check your rip fence for movement when "locked", the BT3 has a unique fence and a locking mechanism in back, read the FAQ and make sure the locking mechanism is working as described.

[davidtu]

Wow, that's a great set of suggestions and help, guys--thanks! I'll check all of these out and post whatever I find.

The one test mentioned above that I did perform was from the manual where I measure a reference point on the blade to the fence 180 degrees apart and that came out ok.

As for the fence, should be able to apply a fair amount of pressure (say like you're tightening a nut sort of pressure) without ANY movement or is the locking mechanism only designed to resist very slight pressure?

I don't think the wood itself (moisture) is the culprit since it is happening with three different stocks -- wenge, zebrawood, douglas fir. I do have a moisture meter tho and will check it to be sure.

I will recheck today with a freshly jointed edge, just to be sure there is no problem with the refernce edges.

As for technique... well I posted this in the Getting Started forum for good reason--I am a newbie and technique could be the cause. So... if anyone wants to post a concise instruction on proper technique or point me to same online somewhere, please do! I am also re-reading the Table Saw book to see if I am forgetting some of the basics. Wouldn't surprise me, I've been trying to take in a lot of info all at once!

Best regards, and thanks for all the advice and interest.
-David

[LarryG]

Best pointer on technique that comes to my mind is the one I always mention, which is: watch the fence, not the blade.

Where the workpiece meets the fence is the table saw equivalent of where the rubber meets the road. Maintaining the stock in contact with the fence at all times is crucial for good results, and to do that you need to direct your vision there.

Obviously you want to always be fully aware of where your hands and body are relative to the blade, either by using your peripheral vision or by glancing at it quickly from time to time. But for the most part, you should be watching the fence. The blade is going to cut whether you're looking at it or not. Keep your eyes (mostly) on the fence and the blade will take care of itself.

[LCHIEN]

Wow, that's a great set of suggestions and help, guys--thanks! I'll check all of these out and post whatever I find.

The one test mentioned above that I did perform was from the manual where I measure a reference point on the blade to the fence 180 degrees apart and that came out ok.

As for the fence, should be able to apply a fair amount of pressure (say like you're tightening a nut sort of pressure) without ANY movement or is the locking mechanism only designed to resist very slight pressure?

I don't think the wood itself (moisture) is the culprit since it is happening with three different stocks -- wenge, zebrawood, douglas fir. I do have a moisture meter tho and will check it to be sure.

I will recheck today with a freshly jointed edge, just to be sure there is no problem with the refernce edges.

As for technique... well I posted this in the Getting Started forum for good reason--I am a newbie and technique could be the cause. So... if anyone wants to post a concise instruction on proper technique or point me to same online somewhere, please do! I am also re-reading the Table Saw book to see if I am forgetting some of the basics. Wouldn't surprise me, I've been trying to take in a lot of info all at once!

Best regards, and thanks for all the advice and interest.
-David

The fence should be able to withstand a fair amount of pressure when locked but you should obviously only have a small portion of what it can stand against it when in use.

A featherboard keeping the material tightly to the fence is an important accessory when ripping. I'll admit I don't always use one but you should, it'll keep one more variable under control when ripping.
Make sure the pressure of the featherboard is applied in front of the blade lest the force cause the blade to be pinched with highly undesirable results.

Here's a pic of how I do mine with the BT.

[davidtu]

My featherboard is straight out of the BT3100 manual... its the very first thing I did on the saw. As per that instruction, it has 3 holes through it for putting the 5/16" screw thru to the miter gauge slot. So I am not using the miter fence w/ the board.

I have to admit that I am not using an auxilliary clamp (besides the screw down knob on the featherboard) to hold the FB in place, as suggested in the manual. Could this be part of the problem?

Btw, what sort of clamp is that you have coming off your miter fence? Looks wild!

[LJR]

The clamp that is on Loring's miter fence is a hold down clamp. Looks like a "regular" hold down clamp for this saw. If you don't have one yet you'll save yourself a bit of grief and trouble by getting and using one. Won't solve your rip problem, but it will solve some others.

[LarryG]

The clamp that is on Loring's miter fence is a hold down clamp. Looks like a "regular" hold down clamp for this saw.

That's the clamp that comes in the BT accessory kit. One of the few items in the kit that quite a few people say is actually worth owning. (I'm not much impressed, rarely use mine.)

[David Coleman]

I had the same problem which was more noticeable when I glued up some ripped boards for a tabletop. I thought if I kept pressure on the board laterally against the front of the rip fence I'd get a more precise cut. Unfortunately the pressure was making the board turn out ever so slightly at the rear of the fence--longer the board, the bigger the gap became. My solution was to supply much less pressure to keep the board against the front of the rip fence, but keep my eye on the board as it passed the rear of the fence to eliminate any gap developing. That's two cents from a fellow newbie, but I get perfectly straight rips now.