Trouble using jointer for tight edge joints on glue-up table top - Woodworking Talk - Woodworkers Forum
 
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post #1 of 20 Old 01-09-2012, 03:56 PM Thread Starter
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Trouble using jointer for tight edge joints on glue-up table top

I hope I'm not duplicating a previous question but my searching didn't find anything on my problem.
I'm using an old craftsman jointer to clean up the edges for glueing 1"x 5" X 6' hardwood boards together to make up a new workshop table.
Even after multiple passes I continue to get a "slight" bowing in the center of the boards. Measurment of the gap at the center is less than the thickness of a piece of paper but enough to see light through, which I assume will weaken the bond.. Every one of the 7 joints (14 edges) is the same. Pretty soon I won't have any boards left so I stopped to get some help. I figure it is something wrong with my technique but can't figure out what I'm doing wrong.
Please educate me someone!!
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post #2 of 20 Old 01-09-2012, 04:16 PM Thread Starter
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correction

After I made the original post I checked more carefully and the gap at the center is big enough to slide a sheet of copier paper through for about 3' at the center.
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post #3 of 20 Old 01-09-2012, 04:23 PM
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check the knives

Your technique may be fine.....no way to tell from here
But if the knives are set too high above the "fixed" outfeed table it will leave a concave edge. They should be at the same height as the table. bill

see 1:15 in how to check on the cheap!

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 01-09-2012 at 04:26 PM.
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post #4 of 20 Old 01-09-2012, 05:57 PM Thread Starter
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Originally Posted by woodnthings View Post
Your technique may be fine.....no way to tell from here
But if the knives are set too high above the "fixed" outfeed table it will leave a concave edge. They should be at the same height as the table. bill

see 1:15 in how to check on the cheap!
Setting Straight Jointer Knives - YouTube

Thanks for the input. I set the knives using a metal straight edge extending out from the "fixed" table. I have them adjusted so that they just scrap the surface of the metal straight edge as judged by sound and feel but do not actually grab the straight edge and move it. I don't have access to a dial guage down here in the primitive lands of Belize. So don't know how I could get any more accurate.
Plus as I think about it, if the knives were too high and cutting more wood than the "fixed table is dictating, would that not also mean cutting the extra off of the tail end of the piece and not cutting a perfect bow from end to end as is happening?
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post #5 of 20 Old 01-09-2012, 06:05 PM
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Quote:
Originally Posted by torrey View Post
I hope I'm not duplicating a previous question but my searching didn't find anything on my problem.
I'm using an old craftsman jointer to clean up the edges for glueing 1"x 5" X 6' hardwood boards together to make up a new workshop table.
Even after multiple passes I continue to get a "slight" bowing in the center of the boards. Measurment of the gap at the center is less than the thickness of a piece of paper but enough to see light through, which I assume will weaken the bond.. Every one of the 7 joints (14 edges) is the same. Pretty soon I won't have any boards left so I stopped to get some help. I figure it is something wrong with my technique but can't figure out what I'm doing wrong.
Please educate me someone!!
I assume that you are jointing both edges of all the center boards. Does this bowing occur on both (each) edge?

Do you run the boards through the jointer in one direction only, or do you alternate direction?

George
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post #6 of 20 Old 01-09-2012, 06:38 PM Thread Starter
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Originally Posted by GeorgeC View Post
I assume that you are jointing both edges of all the center boards. Does this bowing occur on both (each) edge?

Do you run the boards through the jointer in one direction only, or do you alternate direction?

George
Yes George, there are a total of 7 boards so both eges are being joined of all but the two outside boards. The bowing occurs on all edges. When I lay the edge of one board on my metal straight edge (8' metal level) the gap in the center is so samll it just barely allows for sliding a sheet of copier paper in the center back and forth approx 2.5 feet. The gap is perfectly centered and even.But when I put two boards together the effect is magnified double so that the gap is noticable.
I have been running the boards in one direction only.
I ha
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post #7 of 20 Old 01-09-2012, 06:41 PM
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Quote:
Originally Posted by torrey View Post
Thanks for the input. I set the knives using a metal straight edge extending out from the "fixed" table. I have them adjusted so that they just scrap the surface of the metal straight edge as judged by sound and feel but do not actually grab the straight edge and move it. I don't have access to a dial guage down here in the primitive lands of Belize. So don't know how I could get any more accurate.
Plus as I think about it, if the knives were too high and cutting more wood than the "fixed table is dictating, would that not also mean cutting the extra off of the tail end of the piece and not cutting a perfect bow from end to end as is happening?
One more thing to check. See if a straight edge like an 48" aluminum level will lay flat on both the infeed and outfeed tables when the infeed is raised to the same height as the outfeed. It's possible that the infeed is sloped toward the operator's end. That would require shimming the ways if they are not in the same plane.

Now if I were to joint a 6ft long board, I would first sight down it to see if it's got a concave or convex curve on the edge holding it vertically as you would jointing it against the fence.....even a slight concave will be hard to eliminate totally, unless you remove a small amount from each end by flipping it end for end after each pass. and take very small cuts 1/32".
The jointer is not a "one pass, and you're done" machine and it requires a bit of finesse and feel to obtain perfectly straight edges, constantly sighting the board for your progress. A known straight edge 6 ft, as a reference would be handy to have. Having said all that a slight concave 1/64th in the center of the boards should not be a big issue since the clamps will bring the centers together. That's just my opinion however and I always strive for perfection regardless. bill

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 01-09-2012 at 06:53 PM.
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post #8 of 20 Old 01-09-2012, 06:47 PM
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Are you putting to much downward pressure over the cutter head as it passes threw?
Hand placement is critical when jointing.
Especially longer boards.

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post #9 of 20 Old 01-09-2012, 06:55 PM Thread Starter
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Originally Posted by woodnthings View Post
One more thing to check. See if a straight edge like an 48" aluminum level will lay flat on both the infeed and outfeed tables when the infeed is raised to the same height as the outfeed. It's possible that the infeed is sloped toward the operator's end. That would require shimming the ways if they are not in the same plane.

Now if I were to joint a 6ft long board, I would first sight down it to see if it's got a con cave or convex curve on the edge holding it vertically as you would jointing it against the fence.....even a slight concave will be hard to eliminate totally.
Unless you remove a small amount from each end by flipping it end for end after each pass. and take very small cuts 1/32".
The jointer is not a "one pass, and you're done" machine and it requires a bit of finesse and feel to obtain perfectly straight edges, constantly sighting the board for your progress. A known straight edge 6 ft, as a reference would be handy to have. Having said all that a slight concave 1/64th in the center of the boards should not be a big issue since the clamps will bring the centers together. That's just my opinion however and I always strive for perfection regardless. bill
I checked the two tables as you suggested with an aluminum level before I started to use it and they are perfectly straight. I made 4 to 8 passes with each edge. (of course I was taking larger cuts than you mentioned so now my boards are alot narrower.) I noticed the bowing after the first couple of cuts so kept trying again and again to fix the problem. End result= still the same bow only on narrower boards. thats when I quit to ask for help.

Last edited by torrey; 01-09-2012 at 06:58 PM. Reason: forgot to mention that on one joint the clamps will handle it but after 7 joints the problem will be too big
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post #10 of 20 Old 01-09-2012, 07:23 PM
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sighting the board

Sighting the board for progress, lighter cuts and flipping end for end should fix your problem. BTW are you using a Metric hammer, if so that's the problem or just a loose connection.... bill

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #11 of 20 Old 01-09-2012, 07:28 PM Thread Starter
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Sighting the board for progress, lighter cuts and flipping end for end should fix your problem. BTW are you using a Metric hammer, if so that's the problem or just a loose connection.... bill
I'll try what you suggest tomorrow and let you know how it goes.
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post #12 of 20 Old 01-10-2012, 08:12 AM Thread Starter
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Originally Posted by Dominick View Post
Are you putting to much downward pressure over the cutter head as it passes threw?
Hand placement is critical when jointing.
Especially longer boards.
I have been putting a lot of down pressure. How can i get info on how to do it . Do you know of a video to help me learn the correct hand placement
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post #13 of 20 Old 01-10-2012, 08:17 AM
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how big is the jointer?

Learning more about tools everyday
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post #14 of 20 Old 01-10-2012, 08:34 AM
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I have been putting a lot of down pressure. How can i get info on how to do it . Do you know of a video to help me learn the correct hand placement
Dominick is correct. Your knife adjustment sounds right to the outfeed table. Where you set the infeed table is what gets milled off.

Getting the hang of technique comes with practice, and trial and error. The trick is to maintain steady pressure on the infeed table as the stock gets to the cutterhead.

As it passes over the cutter slight pressure only to maintain contact is necessary. This infeed pressure and outfeed pressure remains the same for the length, and as the stock gets close to the end, the same steadying pressure is exerted on the outfeed table and just enough on the infeed table.

IOW, there's a transfer of pressure to maintain table contact without pressing down midstream.






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post #15 of 20 Old 01-10-2012, 08:34 AM
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Originally Posted by torrey View Post
I have been putting a lot of down pressure. How can i get info on how to do it . Do you know of a video to help me learn the correct hand placement




AT 5:00 this video link will discuss the concave issue you posted above:

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 01-10-2012 at 09:08 AM.
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post #16 of 20 Old 01-10-2012, 08:46 AM
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Quote:
Originally Posted by torrey
I have been putting a lot of down pressure. How can i get info on how to do it . Do you know of a video to help me learn the correct hand placement
Don't you have a manual that came with your jointer?
Most manuals explain the technique.
If not you can look it up on you tube.

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post #17 of 20 Old 01-10-2012, 12:10 PM
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Originally Posted by torrey View Post
Yes George, there are a total of 7 boards so both eges are being joined of all but the two outside boards. The bowing occurs on all edges. When I lay the edge of one board on my metal straight edge (8' metal level) the gap in the center is so samll it just barely allows for sliding a sheet of copier paper in the center back and forth approx 2.5 feet. The gap is perfectly centered and even.But when I put two boards together the effect is magnified double so that the gap is noticable.
I have been running the boards in one direction only.
I ha
Try alternating the direction of the feed and see what happens. Be sure the finish feed is down grain.

George
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post #18 of 20 Old 01-10-2012, 12:28 PM Thread Starter
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Originally Posted by tcleve4911 View Post
how big is the jointer?
The jointer is 3' long and uses 6" blades
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post #19 of 20 Old 01-10-2012, 01:05 PM Thread Starter
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"WOODNTHINGS": Thanks for the video links, very helpful.
"DOMONIC": This is an old planer that my landlord is loaning me, no manual. The U-tube videos helped. At least now I know what to practice.
"GEORGEC" Thanks, I am doing that now.

EVERYONE: Thanks so much for all the input. I have started using the suggestions given and the problem is just about cleared up. I now get the cuts down to .003" gap along part of the 6' boards.
When I began the glue up I saw that as I suspected, clamping in the center closed the gap at the joint and accentuated the bow on the two remaining edges. So I glued them up in pairs and then restraightened the edges of each pair then glued the 3 pairs together giving me results that I am good with.
Thanks to all again!
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post #20 of 20 Old 01-10-2012, 01:10 PM
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Cool deal.
Practice make you (almost as good as kenbo)

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