Bow UP or DOWN?

[Keith Starosta]

I may be doing this incorrectly, or doing it correctly but with some flaw in my technique...

I have a few boards that have a slight bow in them, and I was hoping to run them through my jointer to get a straight edge. My question is, should the bow face up or down? I'm pretty much flying by the seat of my pants with this, as this is my first attempt to straighten out a board. I tried some last night, and somehow managed to get one end of the board narrower than the other end by about 3/4". Not sure how I did that.... :o

Many THANKS for your patience and continued advice from this inexperienced, yet very enthused rookie!! :D

Keith

[Doug Keener]

I may be doing this incorrectly, or doing it correctly but with some flaw in my technique...

I have a few boards that have a slight bow in them, and I was hoping to run them through my jointer to get a straight edge. My question is, should the bow face up or down? I'm pretty much flying by the seat of my pants with this, as this is my first attempt to straighten out a board. I tried some last night, and somehow managed to get one end of the board narrower than the other end by about 3/4". Not sure how I did that.... :o

Many THANKS for your patience and continued advice from this inexperienced, yet very enthused rookie!! :D

Keith

Run the board through bow side up. I've had similar results where one end has more removed than the other, but only by an eighth of an inch or so. If you see this happening, turn the board so that the widest end goes through first. Continue pushing the board through till the bow is at its maximum depth over the cutters and stop. Take the board off and run it through again, this time all the way. This will keep the board a more even width.

When I straighten a board, I like to set the jointer depth at minimum depth. It takes more passes, but I keep track of the dimension and do what I mentioned above to keep it even.

[Eric Apple - Central IN]

I run them bow down for most cases. I found this works best for me when the board is longer then the infeed table (which is often) and the apex of the bow can be rested on the infeed table without the leading edge of the board making contact with the cutter.

I basically start feeding the board accross the cutter without the most leading edge making contact with the cutter. Then the around the center of the bow it will begin cut and then finnally not cutting again as the trailing edge is fed across.

I take light passes of about 1/16 each time. Finally when most of the apex is cut out, then entire board will be jointed.

When starting with the bow down and the trailing edge of the board not making contact with the in feed table, I find it very difficult to keep from making a badly triangle shaped board.

Also, after reading the above post again, I'm not sure we aren't saying the same thing. When I say bow side down; I mean the apex of the outside arc is on the jointer table. Imagine a smily mouth sitting like this on the jointer table: U -- I hope you boards aren't as badly bowed as my example!

[Alan Tolchinsky]

I may be doing this incorrectly, or doing it correctly but with some flaw in my technique...

I have a few boards that have a slight bow in them, and I was hoping to run them through my jointer to get a straight edge. My question is, should the bow face up or down? I'm pretty much flying by the seat of my pants with this, as this is my first attempt to straighten out a board. I tried some last night, and somehow managed to get one end of the board narrower than the other end by about 3/4". Not sure how I did that.... :o

Many THANKS for your patience and continued advice from this inexperienced, yet very enthused rookie!! :D

Keith

I do this with the bow down. That way you don't have any rocking when doing it. The most important thing I think is to cut the board length first to remove as much of the bow as possible. So if you have a 6 foot board that's bowed but only need 3 foot pieces, cut the pieces first and most of the bow will be gone. ?Alan in Md.

[Jim Becker]

"Points down" is the way I do it and most often see it described. You avoid the rocking that could result if the curve is the other way. Each pass shaves off more material from the ends of the board until you are finally "flat". Be sure not to put more pressure on the board than you need to keep it on the tables...you don't want to "flatten" the spring and joint a "curve"!

[Eric Apple - Central IN]

"Points down" is the way I do it and most often see it described. You avoid the rocking that could result if the curve is the other way. Each pass shaves off more material from the ends of the board until you are finally "flat". Be sure not to put more pressure on the board than you need to keep it on the tables...you don't want to "flatten" the spring and joint a "curve"!

From the varied responses I've read, there are many ways to "skin this cat". This is one of the method of work things that I guess you just will figure out what works best for you !

The problem I have with the crown up method (points down or frown shaped) is when the board is much longer then the in feed table. I happen to frequently joint 6' long stock. As the other "point" comes up onto the infeed table I get a taper following the "in feeding" point leading to triangle shaped stock. For short stock (<3') I agree this is easier then facing the crown down and doing a balancing act.

For long stock I find that balancing act works better for me with the crown down (think shaped like a smile). In other words, I get more usable stock with the crown facing down.

I sometimes take out the bows on the TS with a jig before jointing. So there's another option I reserve for only the most bowed stock - like 1 1/4" over 6' would hit the TS first and only be used as a last resort in a long length.

[Jim Becker]

I sometimes take out the bows on the TS with a jig before jointing. So there's another option I reserve for only the most bowed stock - like 1 1/4" over 6' would hit the TS first and only be used as a last resort in a long length.

This is actually what most of us should consider...and it wouldn't take much time or money to build a simple ripping jig that can easily handle a 6-8' board. Really whacky boards might be best ripped straight with the jig on a bandsaw, however, at least according to the (excellent) article on milling rough lumber in the latest issue of Fine Woodworking that arrived in my mailbox this week.

[John Tarro]

Points down . . . Problem is that you will tend to get a thin to thick board if the bow amounts to much at all. Rememer, the board has two ends, thus two "points" that need to be removed. To avoid the wedging of the board, take a short cut off each end first before joining the entire length of the board. If you have a 1/8 inch bow, take two 1/16 inch cuts off each end (not too far into the board, just until you hear the cutters leaving the wood) then take a cut off the entire length of he board. Works great

[Mel Fulks]

Convex side down is better because any stress relief movement that occurs as you face will help remove the bow .this is correct but unfortunately counterintuitive .fortunately you can prove it to your own satisfaction.take several bowed boards and put a straightedge on the concave side of each and record their respective gaps at midpoint.face each piece with two or three light passes as I have suggested ,then remeasure the gaps.you will find no increase in any them and some gaps will be smaller.you have now straightened both sides by cutting on one side!proceed proudly to planer and dress the rough sides .any further thickness reduction should come off convex side,(or worst side if board is now perfectly straight)

[Chris Friesen]

If the board is short enough to fit on the infeed table, definitely points down. If it's long and the bow is severe I'll snap a chalk line and freehand rip to the line on the bandsaw. In between it varies...whatever works.

The key with going "points up" is that you need to be really careful not to rock the board and it's hard to maximize the resulting thickness of the board.

[Van Huskey]

I have always done points down, I have never been able to run points up (concave up) effectively since I can't hold a long board in a way to get it to just cut the center, though I haven't tried that often. If the box is excessive I just crosscut it so I can get boards of usable thickness from it though obviously shorter. I can see Mel's approach working but it seems a little tedious unless it is a prized board.

[J.R. Rutter]

On long boards , I joint off the high center first. On shorter boards, I joint off the points at each end. If your technique is good, either way works. I agree that for stress relief, jointing the convex edge off works. But if a wide board has significant tension, it will still bow when you rip it into narrower strips.

[Kent A Bathurst]

Yeah - "horns down".

Also - you probably already took care of this - but you're better off if you rough-cut the boards before jointing. I usually go to 1/2" - 1" or so over finished part length, and 1/4" - 1/2" over width. This reduces the effect of the bow & twist on the overall board thickness as you joint & plane.

One last caution...after jointing and planing, stand the boards on edge or sticker them. You want air circulation on all faces.

Laying them flat on a surface like TS will cause them to warp. Or, so I have heard :D.

[Myk Rian]

Points down. Curve up.
I take some off one end, then the other.
Then I run the whole board through.
You'll lose thickness on both ends.

[Jerome Stanek]

I run it through the table saw attached to a straight edge.

[Keith Starosta]

Yeah - "horns down".

Also - you probably already took care of this - but, you're better off if you rough-cut the boards before jointing. I usually go to 1/2" - 1" or so over finished part length, and 1/4" - 1/2" over width. This reduces the effect of the bow & twist on the overall board thickness as you joint & plane.

One last caution...after jointing and planing, stand the boards on edge or sticker them. You want air circulation on all faces.

Laying them flat on a surface like TS will cause them to warp. Or, so I have heard :D.


I appreciate all the advice, and continued support of the great folks here are The Creek. I was finally able to improve my technique.....in the NINE YEARS since I first posted this question. :D :eek:

[Sam Murdoch]

First off I recommend to everyone who will listen - cross cut every long board to as short as you need + 4" to 6" (depending on how snipe free your thickness planer is). I would rather have 16 door parts at 24" then 32 at at 48" when it comes to the purpose of jointing your stock for flat or straight. More pieces but much less work and much more positive results in the end. Having said that I mostly run the points down with a very light touch ( I don't hold the wood to the jointer bed, I pass it over the cutter knives.) and end for ending as I work the board to get an even full body pass. In some boards you will find that you can only pass over the jointer in one direction or get tear out, but most often these light initial passes to clean the ends is pretty forgiving of end for ending.

I believe that Mel is correct though - that the convex side should be down for best results, but for me boards that are in that much tension are simply rejected. The most often slightly curved boards get jointed and planed on opposite faces in such away and in so many passes as to relieve all the tension. At least this is how I prefer to work. No rules are set in stone. Lots of this is feeling and the sharpness of the cutters, the ease of the touch as you pass over the jointer and the final use of the wood.

[Kent A Bathurst]

I appreciate all the advice, and continued support of the great folks here are The Creek. I was finally able to improve my technique.....in the NINE YEARS since I first posted this question. :D :eek:

Hey - Keith - I spent >9 years learning this stuff. And, most valuable, learning during those eyars how to correct mistakes on-the-fly, or change designs/dimensions on-the-fly to accommodate the mistakes. In fact - I just finished correcting the odd error on some dining table chairs............

The really hilarious part - One would think that any given mistake would be made only once.

But - Nooooooooo. :p

Carry on.

[Kent A Bathurst]

I run it through the table saw attached to a straight edge.

Correct solution. Your condition, however is crook, not bow. Same concept,different orientation.

http://unitecboatbuildingtradeterms2011.wikispaces.com/file/view/wood_fault.jpg/214408834/wood_fault.jpg

[Richard Dragin]

I would like to congratulate Mel Fulks for one of the oldest thread resurrections ever! Crown up, points down. Feed just the ends till it's close. Don't press down too hard on the middle.

[Sam Murdoch]

I had to laugh. I got sucked in too :D. Oh well, some newcomers might benefit...

[Keith Westfall]

Good advice never goes out of fashion... :cool:

[Mel Fulks]

The thread is indeed old,but the topic is always current somewhere.I had worked in custom architectural woodwork about 8 years when I was assigned a job working with Albert,the older lead shop guy,his father had worked there too.I had to make some vertical louvre slats about10 feet long which had to be straight.I looked thru the the pile and determined we did not have enough appropriate wood. When I informed him he went thru and picked 8 or 10 more pcs with a long even bow. He told me to face them convex side down and BOTH sides would start to straighten. News to me. It worked and I have been using that technique, and winning bets with it, for 30 some years. Thanks Albert.

[Jeff Duncan]

Nine years may be about right to feel comfortable enough to try a new technique;)

I started out using the points down method for several years. Finally having heard the benefits to crown down enough I tried it and have never gone back. A bit more difficult to control stock though, especially for beginners. When I have to teach a new employee I teach them crown up as it's easier for them to handle. Of course then I have to run the 'important' parts myself:o

good luck,
JeffD