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1:6 and a 1:8

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Forum topic by Justin posted 02-28-2008 04:33 AM 1467 views 0 times favorited 10 replies Add to Favorites Watch
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Justin

36 posts in 4261 days


02-28-2008 04:33 AM

Ok so I have a question for you guys, And I think this is the right place to post it. For setting up dovetails the rule of thumb is to use the two angles of 1:6 and 1:8. I understand how the angle is achieved. What I am wondering is how did they derive with these to angles. I have heard one is for hardwoods and one softer woods.
I am guessing the 1:8 is for the hardwood? Please exsplane this to me, I am curious.

Justin


10 replies so far

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lew

12859 posts in 4260 days


#1 posted 02-28-2008 04:43 AM

Justin,

You are correct about the 1:8 being for hardwood. The 1 and 8 are the base and altitude of a right triangle. Layout a right triangle with the base at 1 inch and the altitude (height) at 8 inches and then connect the points to complete the hypotenuse. Use your sliding bevel square to match the base/hypotenuse angle. Now you can transfer the angle to your work piece to layout the dovetails. You can make a reference board with both the 1:6 and 1:8 layouts for quick, future reference. I have even seen these permenantly scribed on workbenches and even the outfeed table of a table saw.

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

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Sawdust2

1466 posts in 4592 days


#2 posted 02-28-2008 05:03 AM

You can take Lew’s explanation to the bank.

Lee

-- No piece is cut too short. It was meant for a smaller project.

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Eric

875 posts in 4288 days


#3 posted 02-28-2008 05:32 AM

I posted about making a dovetail template (and posted it as a project), which has the layout angles as well as a square. I also had to issue a retraction when I realized that I needed to have both directions of an angle represented on the template – whoops! So look at the template and see where I went wrong. If you did one, you could do 1:6 on one side and 1:8 on the other (with no square), or just split the difference and do both ways of a 1:7 and a square.

Dovetail Template

-- Eric at https://adventuresinwoodworking.wordpress.com/

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Justin

36 posts in 4261 days


#4 posted 02-28-2008 05:35 AM

Thanks for the Reply Lew,

How did they come up with them numbers. They just looked the best, What made them the standers to go by? Why not a 1:7 and a 1:5?

Sorry to be a pain,

Justin

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lew

12859 posts in 4260 days


#5 posted 02-28-2008 06:16 AM

I am not sure about the origin and in fact have seen the numbers 1:7 listed some place. Maybe, like you said, these are pleasing to the eye. Maybe they provide the best ratio of strength to size factors. I am sure that one of the Lumberjocks members has more knowledge than me and hopefully they can give us both the answer.

I really like Eric’s setup jig. It makes it alot easier to quickly set the bevel guage instead of trying to align the blade with a scribed line, on a piece of wood.

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

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Eric

875 posts in 4288 days


#6 posted 02-28-2008 02:06 PM

Actually, the jig is intended to replace the bevel gauge, not set it up. You put the appropriate ratio (like 1:6) on the edge of the board, and the part of the template hanging down is your line to mark. Plus, having a square on it as well really helps with quicker and easier layout of the squared lines on your dovetail.

-- Eric at https://adventuresinwoodworking.wordpress.com/

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lew

12859 posts in 4260 days


#7 posted 02-28-2008 02:10 PM

Even better!

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View Alin Dobra's profile

Alin Dobra

351 posts in 4392 days


#8 posted 02-29-2008 05:35 AM

Justin,

It turns out that it does not really matter. Fine Woodworking(FW) tested dovetails with both angles and the results came up the same. What you want, really, it to pick a visually interesting angle. I cut my dovetails without any guide and none of my angles are the same. I am guessing I make the angle random between 1:5 to 1:8.

The FW people debunked a lot of myths about dovetails in that article, not only the 1:6 vs 1:8 angles. They also showed that skinny pins are not weaker that wide pins (they are actually slightly stronger).

Alin

-- -- Alin Dobra, Gainesville, Florida

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Justin

36 posts in 4261 days


#9 posted 03-01-2008 01:15 AM

Thanks for the reply guys.

Justin

View damnHippie's profile

damnHippie

35 posts in 4280 days


#10 posted 03-01-2008 01:28 AM

Here’s the article Alin is referencing: http://www.taunton.com/finewoodworking/SkillsAndTechniques/SkillsAndTechniquesPDF.aspx?id=2712

-- 10 fingers, 2 eyes, and healthy lungs. for now. :P

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