Knots ????

[Tanner]

I've seen many pens lately with knots in them. I've noticed that in some cases the knots don't match up perfectly. Before I attempt one of these cool looking pens, I want to know if there is a way to get the lines to match up perfectly. Do you just have to eye ball the lines? I don't want to go through the process of making one of these to have the finished products lines not match up real good.

 

[leehljp]

Two very recent posts:
http://www.penturners.org/forum/topic.asp?TOPIC_ID=26225
http://www.penturners.org/forum/topic.asp?TOPIC_ID=26269

 

[Tanner]

I see a lot of talk about kerf sizes and such. Nothing about why the lines don't match up. To be honest I have not seen many pens where the lines do match up perfectly. Some slightly off, some way off. This must be in the glueing process.

 

[GaryMGg]

Tim,

When you read George's (texatdurango) tutorial you'll learn that to have the rings aligned is a matter of marking the blank properly and using hold-downs and stops to keep the blank in the proper location for each cut.
http://www.georgeandsirik.com/knot-tutorial.html

Simply, Suppose I cut 1/8" at 45-degrees from a 1" X 1" X 6" blank.
Then, glue in a slice of wood 1/16" thick.
When the second cut is made with an 1/8" thick blade, part of the slice disappears and maintaining alignment becomes a matter of luck rather than controlled accuracy.
That's where the slice thickness == blade thickness comes in.

If you glue in an 1/8" thick slice, parity is maintained and you can continue.
Now, rotate the blank 180-degrees to make the second 45-degree cut, the center of the cut must go through the center of the first glued-in slice.
This is how they'll intersect. Otherwise, the rings of the knot won't line up.
Each following ring uses the last as it's foundation, so you have to maintain a constant size to maintain alignment.

I hope that's clear and correct.
Gary

 

[Tanner]

Thank you very much for the explanation Gary!!!! It takes me awhile to catch on.[:I]

 

[Texatdurango]

Tim,

I made several of these knot designs lately and one thing I think is just as important as cutting through the centerline are the segment thicknesses themselves.

I recently made some pens and got a bit sloppy with my segment slice thicknesses. Most were between .072" and .075" but a couple were .080". Doesn't sound like much difference but when they were glued up, the intersecting lines grew farther off as I went around gluing up the blank. I would now say that the most critical step is to insure the segment slices are as close to the saw kerf thickness as possible. Of course, keeping the glue ups nice and tight is still critical.

The best way to see what we're saying is to just get an el-cheapo blank and some el-cheapo contrasting wood and cut and glue. The offsets will become easily noticable if you get sloppy.

George