Gaps in dovetail base lines - Woodworking Talk - Woodworkers Forum
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post #1 of 17 Old 05-28-2017, 09:33 PM Thread Starter
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Gaps in dovetail base lines

Hey guys.. I have been practicing dovetail joints and it seems the majority of the Gap is in the baseline... Any one know why that is or what can be done to prevent that Gap? Everything else fits pretty well... Thanks guys. Still learning
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post #2 of 17 Old 05-28-2017, 11:55 PM
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Put a square on it and see if the bottom cut is off or the drawer face is bowed.
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post #3 of 17 Old 05-29-2017, 07:33 AM
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Are you hand cutting or using a "store bought" dovetail jig?

Most jigs come with instructions of how to correct this problem.

George
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post #4 of 17 Old 05-29-2017, 07:50 AM Thread Starter
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George I'm using. Hand saw
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post #5 of 17 Old 05-29-2017, 08:42 AM
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Originally Posted by chueyjose View Post
George I'm using. Hand saw
Very commendable keeping up the old ways. Cutting dovetail joints are just difficult. It's how the dovetail joint became popular. A couple hundred years ago adhesives weren't so good so the solution to keep a drawer box from coming apart was the dovetail joint. Because then all of them were done by hand and difficult people used to judge the skill of the craftsman by his dovetail joints. The assumption was if his dovetail joints were good the rest of the woodwork would be equality as good. From then good dovetails were a sign of quality. Now fast forward to now the machinery today can make perfectly fitting dovetail joints you could almost train a monkey to run it but still people look to the dovetail as a sign of quality. Now today with modern adhesives the dovetail is not necessary and actually produces a weaker joint than a butt joint. The joint will last for decades without any repairs and those drawers that do have the dovetail the pins normally break off requiring you to replace the drawer sides to make the repair.
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post #6 of 17 Old 05-29-2017, 09:05 AM
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Consider when making dovetails, it is most important to scribe the cutting lines with a very sharp marking knife - rather than a pencil which IMO leaves a wider line. Be safe.
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post #7 of 17 Old 05-29-2017, 10:30 AM
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Originally Posted by Steve Neul View Post
Now today with modern adhesives the dovetail is not necessary and actually produces a weaker joint than a butt joint. The joint will last for decades without any repairs and those drawers that do have the dovetail the pins normally break off requiring you to replace the drawer sides to make the repair.
I have to disagree here. Yes, modern adhesives are amazing, but when time has passed and the wood or adhesive breaks down a well-done and glued dovetail jointed drawer or tool box will still be together after every glued butt jointed drawer has fallen apart. If your pins are breaking then it wasn't a well-done dovetail or cared for box/drawer. I see no reason to start relying on an inappropriate joinery type (for the application) and just glue. A better joint plus the same glue will always be a better joint. Of course a butt jointed box may be plenty strong if all it needs to do is sit there and be admired. Drawers and tool boxes will experience far more unusual forces over their lives. The ones that survive were not done with butt joints.

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post #8 of 17 Old 05-29-2017, 10:44 AM
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I have to disagree here. Yes, modern adhesives are amazing, but when time has passed and the wood or adhesive breaks down a well-done and glued dovetail jointed drawer or tool box will still be together after every glued butt jointed drawer has fallen apart. If your pins are breaking then it wasn't a well-done dovetail or cared for box/drawer. I see no reason to start relying on an inappropriate joinery type (for the application) and just glue. A better joint plus the same glue will always be a better joint. Of course a butt jointed box may be plenty strong if all it needs to do is sit there and be admired. Drawers and tool boxes will experience far more unusual forces over their lives. The ones that survive were not done with butt joints.

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The comments I made were from the experiences from when I had a furniture repair shop. Repairing furniture you see how time affects different joinery. Probably 80% of the drawers that needed repair were done with the dovetail joint. The ones that were butt jointed a little epoxy glue and a few brads and the drawer was good as new. It was a cheap and easy repair. The dovetail joints more often than not still had the pins broken off and still glued into the drawer fronts requiring an expensive repair fabricating new parts to match someone's dovetail work. Very often I would dispose of the drawer box completely and rabbet the dovetail work off the drawer fronts and remake the box with butt joints. My customers were more interested in cost than having the drawer box restored back the way it was.
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post #9 of 17 Old 05-29-2017, 10:48 AM
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I've been making "drawer lock" joints with my shaper for over 40 years and have never had one come apart. I do have an Omnijig, but the shaper is much faster
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post #10 of 17 Old 05-30-2017, 03:53 PM
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Originally Posted by Steve Neul View Post
The comments I made were from the experiences from when I had a furniture repair shop. Repairing furniture you see how time affects different joinery. Probably 80% of the drawers that needed repair were done with the dovetail joint. The ones that were butt jointed a little epoxy glue and a few brads and the drawer was good as new. It was a cheap and easy repair. The dovetail joints more often than not still had the pins broken off and still glued into the drawer fronts requiring an expensive repair fabricating new parts to match someone's dovetail work. Very often I would dispose of the drawer box completely and rabbet the dovetail work off the drawer fronts and remake the box with butt joints. My customers were more interested in cost than having the drawer box restored back the way it was.
Your experience doesn't surprise me. Most that owned cheaply made butt joined cabinet drawers would either "fix" broken ones themselves or simply throw them away. The ones who owned cabinets with dovetailed drawers (well made or poorly made) would more likely look into having them repaired when they failed. New, or even "Good as new" butt joined drawers will still be inferior to a well made dovetailed drawer. The difficulty you have repairing them speaks to the value of their mechanical interlock. The historic reason for dovetailed corners still stands today. Modern improved adhesives can make any joint seem "good enough", but that doesn't make a butt joint better than a dovetail joint for the right application.

I've been teaching furniture design for the last 4 decades. We often show students how easy it is to break an end grain to face grain butt joint in any wood compared to the strength of box or dovetails or modern CNC-cut variations in the same wood. When they've made the mistake of cutting their parts to inside dimension (where butt joints seem like the only joinery option) we'll still advise dowels or dominos to greatly improve the joint.

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post #11 of 17 Old 05-30-2017, 04:53 PM
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Your experience doesn't surprise me. Most that owned cheaply made butt joined cabinet drawers would either "fix" broken ones themselves or simply throw them away. The ones who owned cabinets with dovetailed drawers (well made or poorly made) would more likely look into having them repaired when they failed. New, or even "Good as new" butt joined drawers will still be inferior to a well made dovetailed drawer. The difficulty you have repairing them speaks to the value of their mechanical interlock. The historic reason for dovetailed corners still stands today. Modern improved adhesives can make any joint seem "good enough", but that doesn't make a butt joint better than a dovetail joint for the right application.

I've been teaching furniture design for the last 4 decades. We often show students how easy it is to break an end grain to face grain butt joint in any wood compared to the strength of box or dovetails or modern CNC-cut variations in the same wood. When they've made the mistake of cutting their parts to inside dimension (where butt joints seem like the only joinery option) we'll still advise dowels or dominos to greatly improve the joint.

4D
I just will never believe this. A lot of the furniture I was working on was some really well made high dollar furniture. It's evident the root cause of the joint failure was due to the dovetail joints. All that was holding the drawer together was the dovetail pins. Once they were broken it just had the end grain butting into the drawer front which had no chance of holding. Now some of the very old dovetail joints which had larger pins spread out had a much better chance of holding but those were few and far between.
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post #12 of 17 Old 05-30-2017, 07:35 PM
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I just will never believe this. A lot of the furniture I was working on was some really well made high dollar furniture. It's evident the root cause of the joint failure was due to the dovetail joints. All that was holding the drawer together was the dovetail pins. Once they were broken it just had the end grain butting into the drawer front which had no chance of holding. Now some of the very old dovetail joints which had larger pins spread out had a much better chance of holding but those were few and far between.
I'm not trying to start an argument. I agree with and believe everything you've said except " the dovetail ... actually produces a weaker joint than a butt joint". Butt joint easier to fix? Sure. Likely to show up in a furniture repair shop? Less. Any drawer joint can fail over time or abuse. As I already agreed you would see more broken dovetail joints because they came from more valuable homes/cabinetry.

When I see that a student has made a corner butt joint between two or more boards I ask what the box being made will hold. If it is for lightweight nicknacks and not expected to resist dynamic loads then I let it be. If it is to be a sliding drawer under repeated push and pull then almost any interlocking joint at the front and back corners will be a better option. More glue surface area for the improved modern glues is always better than the minimal glue surface area between end grain and face grain of any butt joint done with the same glue. Butt joints like any other joint can fail over time. Quickly if the glue fails. In a butt joint any lift or push or pull works against the glue. In a dovetail joint that push/pull force is borne by the wedging faces between pins and tails. The glue can break down completely and a good dovetail joint can still be holding the drawer together. The strength in your repaired butt joints is in the brads you used. Once you use a brad it is no longer a simple butt joint.

I design and test new joinery that we can cut on our CNCs to solve unique furniture part connection challenges every semester. You can see some of my samples here: http://4dfurniture.blogspot.com/2016...r-cnc-cut.html. If I can break a sample I've created under 10x the load the intended project might expect then I rethink it and try again. I consider grain orientation, strength and fracturability of the wood species being used to come up with the best joinery options.

4D
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post #13 of 17 Old 05-30-2017, 09:19 PM Thread Starter
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Does anyone have any insight towards the gaps in the base line? Lol
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post #14 of 17 Old 05-30-2017, 09:37 PM
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Does anyone have any insight towards the gaps in the base line? Lol
Did you try putting a square on the joint. The part in your left hand may have a slight cup warp or perhaps you cut a little too much off the bottom part of the side.
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post #15 of 17 Old 05-31-2017, 06:39 AM Thread Starter
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Yes. I think the baselines are not square where chisel down
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post #16 of 17 Old 05-31-2017, 06:51 AM
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Yes. I think the baselines are not square where chisel down
You did better than I would have. I go years between occasions I use a hand saw.
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post #17 of 17 Old 06-19-2017, 03:50 PM
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Originally Posted by chueyjose View Post
Hey guys.. I have been practicing dovetail joints and it seems the majority of the Gap is in the baseline... Any one know why that is or what can be done to prevent that Gap? Everything else fits pretty well... Thanks guys. Still learning

First, nice job! The fit on those looks quite good, despite the gap.

I've had a few issues lead to base-line gaps.

1) Cutting below the line. This is easily the problem I have most often. Especially on the edge of the board, it's easy to cut in just a little too deep, which means there will be a gap.

2) Not cutting square across. Is there a gap on the inside? If not, you angled the cut a little bit.

There are others, but they don't actually make sense here. On this board, I'd check to see if there's a gap inside. If so, you cut below the line. If not, you didn't make the cut square across the tail board.
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