This weekend I was helping my neighbor build a fireplace mantle. the plans called for the two side columns to be mitered and glued to form a box. I cut the lengthwise miters at 45 degrees, checking the angle of the tablesaw blade with both a miter square and a digital angle finder (Wixie) to be sure the angle was correct, then ran all the stock at that setting…when I glued the pieces together there were various gaps along the edges that I guess I’ll fill with epoxy sawdust mixture. None of the gaps are more than 1/16″ and most were small so that I could close them with the burnishing trick using the shaft of a screwdriver. So why the gaps and how can I prevent them in the future?
Knowledge gap Neil
Replies
I'd think the gaps might be caused by several things, including some minor play in the saw blade, the boards not being perfectly flat/straight, variations in feed pressure against your fence, or even play in the fence itself.
Well, I didn't suface the boards so I can't comment on their overall flatness ...the saw and fence are from SawStop..but I did have to use a Freud thin kerf blade which does deflect and the finger board was abit tight on a few of the passes necessitating uneven pushing...normally I use a Woodworker II but my SawStop misfired wrecking aperfectly good blade so maybe that was the reason. Thanks.
Slightly more knowledgeable Neil
Your SawStop misfired? I'd be calling the manufacturer for a replacement blade.
Hi Ralph,
I emailed them yesterday but haven't heard back...my understanding is that they'll replace the brake cartridge but not the blade..too bad cause the blade was more expensive...I contacted Forrest about a repair of the blade since at least one and probably two teeth were damaged but they said that the blade was probably bent and they had little success straightening them...so I went ahead and ordered a new one...I should charge my neighbor but I like him too much.
Out of pocket Neil
Neil,I'd go with others about not having properly surfaced wood to start with but the more interesting question is the SawStop misfire.
Just to be clear, are you saying the saw misfired on this project and the result was using an alternate blade or had it misfired prior to this project and thus then the more flexible different blade?Do you or SawStop have a indication what may have triggered the firing?
What kind of wood was it and do you know what it's moisture content was?
I ask in that in many cases mantle wood is very thick (I have seven inch thick mantles with mitered corners) and although the outside could be in the 6-10% range, the core wood could easily be up in the 18 or higher percent range and thus trigger the misfire on the saw.
Did it trigger without your hands being close to the blade?Boiler
Boilerbay,
What happened was that I was trying to tilt the blade to 45 degrees but the zero clearance throatplate wouldn't allow the last few degrees so I decided to cut a new one. The throatplate is larger than most so I used an "official throat plate blank" produced, I assume, by SawStop. I slowly raised the blade and just after it came through, maybe cutting a swath of 2 1/2 " there was a "pop", the blade disappeared and the saw shut down...there was brief confusion and then stunned silence as we realized what happened....kinda ruined the spirit for awhile but then the excitement of buiding something returned....
Neil, still waiting to hear from SawStop
curiouser and curiouserBB
Glad you are not hurt , how long has it been since you contacted SS ?
This thread may tell others what type of customer service or lack there of SS provides after the sale .
As far as the miters did you say exactly how you cut them , face up face down or against a fence or what ? Lot's of variables .
dusty
Hey Dusty,
Thanks for the well wish..I cut the miter face down to the left of the fence....I used a finger board to keep the board steady but occasionally the fit was a bit tight and I had to push hard to get past the finger board so that may have contributed to the uneveness
As to the brake firing I learned what I did wrong..the SawStop rep asked me if while raising the blade I still had the riving knife in place...turns out there's no slot for the front of the knife and so when I raise the blade into the throatplate, the riving knife is deflected downward and forward into the blade, closing the circuit...said it happenend to him...so I guess I don't get my free replacement brake...c'est la vie...
Wish I had a shaper but since I bought a new bandsaw the shaper is a ways down the road.
Thanks for everyone's helpful input and interest
sadder but wiser Neil
nn,
Not sure if it is left tilt or right for your saw , sounds like a right tilt , try face up when cutting miters you will not get tear out on the bottom of the cut in this case the face .
dusty
Neil, I just skimmed the other post, but didn't see any mention of making sure that the stock stays in contact with the saw table as you feed it. This is probably the easiest mistake for miter rips, which leads to the problem you describe.
Neil,
The gaps in the long miters could have been caused by a couple of things: inaccurate maching and clamping protocol. Or perhaps a bit of both.
You said in a later post that you hadn't surfaced or flattened the boards prior to cutting the miters. That could have led to inaccurate miter angles.
For instance, if you run a cupped board through a tablesaw with the blade set at a 45 degree angle, if the convex side of the board is facing down, it has the opportunity to rock side to side while being cut. That can lead to miters that might be anywhere from 43 degrees to 47 - or maybe even further off than that.
It would have been better to first joint one side of the boards flat, then plane off the other side to make the two sides parallel. Then you'd have a flat reference surface to lay on the saw. And if the saw was cutting accurately, the miters should be precise and accurate as well.
As to clamping up long miters, I've used packing tape to help keep things aligned. You lay the boards inside surface down on a flat surface, sharp mitered edges touching. Run packing tape over all the boards in at least three areas, perpendicular to the miters, and then simply roll the whole assembly up. The tape keeps the miters from squirming out of position as the glue sets. Very simple, but quite effective.
In many cases you don't even need any other clamps when you tape up miters this way.
Try it again with flat boards and tape to help clamp the posts up and you'll likely have a much better result.
Another thing I do, which is something I learned doing carpentry work, is to not cut things "exactly" to what, theoretically, they should be. Four 45 degree corners often result in open gaps at the outside edges. Four 45 1/2 degree corners result in tight outer edges. The insides might be a little open, but so what? It's the outside, or "show" areas that count. This is called "backcutting."
Zolton
If you see a possum running around in here, kill it. It's not a pet. - Jackie Moon
Thanks Zolton,
I hadn't thought about making the angle slightly larger or using packing tape..the boards were jointed and surfaced by a guy at our local lumber yard who is a woodworker himself and probably were pretty flat...I just have never had him surface any lumber because I prefer doing it myself. Anyway, on my next project I will take your advice.
Neil
I have been using a sawstop for three years and it continues to be the best saw that I have used; however, for long miters like you are making the lock miter joint made on a shaper is almost an ideal solution.
The lock miter will be much easier to glue up and gives the joint an additional dimension of strength as well.
Moksha
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