jointing problems on my bt3000

[glencross]

I want to laminate two pieces of one inch thick cedar (1 x 3 1/2 inches x 30 inches).
Each time i cut, I end up with a perfect fit at each end (about one inch long) but almost a bow out for the rest of the length...
I have checked and double checked everything and can find nothing wrong but after eight attempts I am slowly going bonkers!!!!
what if anything am i doing wrong or is there some problem that someone out there has run into of a similar nature before?+

my bt 3000 is about 10 years old and has performed flawlessly to date except for the switch which i have now replaced with a "proper" type and mounted in the "proper" place on the LEFT side of the saw, where, in my opinion, it should have been in the first place.
All help gratefully acknowledged.....

[Black wallnut]

How much of a bow and when you place the two pieces edge to edge do you have a gap in the middle () or does the middle touch and the ends don't)(.Guess you already answered this. Slight errors in straitness can be caused by a number of things. Perhaps technique being the most common. Are you watching the fence or your blade during the cut? Should be the fence BTW. Is your riving knife assuming you use it out of alignment? There could be stresses in the wood you are using that are being released with each cut. Is your lumber straight grained and free of knots and wild figure?

If the gap is small can you bring is closed with moderate clamp pressure? If so a good glue bond should hold it.

[ragswl4]

How much of a bow and when you place the two pieces edge to edge do you have a gap in the middle () or does the middle touch and the ends don't)(.Guess you already answered this. Slight errors in straitness can be caused by a number of things. Perhaps technique being the most common. Are you watching the fence or your blade during the cut? Should be the fence BTW. Is your riving knife assuming you use it out of alignment? There could be stresses in the wood you are using that are being released with each cut. Is your lumber straight grained and free of knots and wild figure?

If the gap is small can you bring is closed with moderate clamp pressure? If so a good glue bond should hold it.

Great advice on watching the board at the fence and not the blade during the cut.

In addtion, as you may already know, the edge of the board against the fence must be dead straight or any non straight profile in that edge will be transferred to the cut.

I suggest that you measure the width of the board at numerous places along its length. If it is the same width (exactly) at these locations, chances are that the edge of the board on the fence is not straight.

If not the same width then check fence alignment to the blade and riving knife to the blade. Can also be caused by the board moving away from the fence during the cut. Are you experiencing any binding or burning during the cut?

[Uncle Cracker]

Also, don't force the work into the blade. Feed slowly and let the blade find its way.

[Joe DeFazio]

It is certainly worth figuring out why your boards are not being cut properly. One other factor that you may consider is that wood has internal stresses within it that are often relieved by a cut. That means that the wood changes shape as it is being cut. This can certainly cause the symptom you are describing even if the saw and operator are performing flawlessly. In fact, it's one of the main reason's that we need a riving knife or splitter to reduce the chances of kickback.

However, I will just point out that many woodworkers who glue up boards edge-to-edge intentionally hand-plane a slight bow in them (curving in towards the middle), so that when they are laid side by side, a very slight gap exists in the middle. This is called a "sprung joint," and allows the boards to be clamped with very even pressure with only *one* clamp in the middle (I don't use sprung joints, but if I did, I'd probably use more than one clamp). I have read that some wooodworkers feel that this is the best way to edge-glue boards.

As is stated above, I don't use this technique, and am not necessarily recommending it. However, I am mentioning it because if you can lay your boards against each other with the required gap in the middle, it may be possible to glue them just as they are.

Good luck,

Joe

[SARGE..g-47]

Evening Glen...

My first guess would be compression in the stock as already mentioned by Mark and Joe. That's the most common problem that will produce the case you mentioned. And likely that a dull blade.. fence alignment or arbor run-out which you already checked would produce a burn on the edge of the stock.

So... right back to compression stock which most soft-wood is more prone too and cedar ranks near the top. Was the wood properly dryed before you took the shot?

Regards...

[hermit]

I ran into the same problem some time ago, and found it was technique. I was trying so hard to keep the board against the fence that it actually moved slightly away from the fence on the outfeed side, causing the "curved cut". Try concentrating on moving the board FORWARD, and not so much "pushing to the right" to keep it against the fence, and see if that helps you out.

Todd

[glencross]

jointing problems on the bt3000

thanks for all these answers...everything has been checked and double checked and all appears to be in order...however, hermit has a point and I will try recutting keeping very little pressure against the fence and see if that helps...will get back to you on this as son as i recut. again, thanks for all your helpful advice.

[Garasaki]

You may want to consider using a featherboard to hold the stock against the fence.

I use one to hold the stock against the fence and one to hold it down to the table...the result is that the only thing I am "responsible" for is feeding the stock thru...I don't have to worry about feeding it straight or holding it down on the table.

[lakkdainen]

For what it's worth, I had this exact problem when I first got my 21829... happened no matter what kind of wood I cut, even MDF, which definitely has no internal stresses. In my case, the riving knife was slightly bent to one side, and I just had to bend it back.

[Larryl]

You might also check to see if your fence is holding...by concentrating on pushing to the right to keep it against the fence, you may have some slight movement in the fence. Try pushing against it with your hand to make sure it is steady.