My pen blank fell apart

[ndep]

I tried to make a segmented blank for the first time, and it fell apart while sanding. At a high level, I did a simplified plastic/resin version of a celtic knot style blank. Here are the specific steps:

(a) Sandwiched red plexiglass between white pickguard plastic; all surfaces sanded and laminated with CA glue.
(b) cut a green acrylic pen blank at a 45 degree angle
(c) CA glued the green blank back together, but with the red & white laminated (from "a") in between
(d) cut the green blank again, bisecting the red & white laminate
(e) CA glued it back together with another square of red & white laminate ==> result is an "X" pattern of red & white laminate
(f) cut the blank in half at the intersection of the "X"
(g) CA glued a blue piece of plexiglass into the final cut.

At this point, I have a green acrylic blank with the "X" from the red & white laminate; and the X is cut in half with a sliver of blue plexiglass.

The blank has been left to dry for more than a week.

I cut it to size, drill it out and glue in the sanded brass tubes.

I turn it successfully on the lathe.

When I sand it, the red & white parts fall off.

Suggestions?

 

[KenB259]

Sanding can generate a lot of heat. Since you already had it turned close to size, there's not much glue holding it together. At that point if it gets to warm it'll come apart in a hurry.

 

[Penchant 4]

Plexiglas is very difficult to bond to dissimilar materials, IME, especially with typical adhesives, i.e. affordable. Perhaps substitute a different red material.

 

[ndep]

Sanding can generate a lot of heat. Since you already had it turned close to size, there's not much glue holding it together. At that point if it gets to warm it'll come apart in a hurry.

What would you do differently?

 

[ndep]

Plexiglas is very difficult to bond to dissimilar materials, IME, especially with typical adhesives, i.e. affordable. Perhaps substitute a different red material.

What would you recommend as a substitute material?

 

[KenB259]

What would you do differently?

I try not to sand segmented blanks at all. If you practice you can get a very smooth surface with a skew or even carbide, where no sanding is needed. A lot of times, with differing materials, for example ebony and holly, sanding will just make a mess of things. I have no experience with plexiglas, so I can't help you there. I can tell you CA doesn't work very well with some plastics. Sounds like plexiglas is one of them.

 

[jttheclockman]

The problem with the whole project is the use of CA. Not a fan. It is a brittle glue that needs alot of surface area to really adhere well. yes heat can play a roll. You mentioned a few times plexiglass, are you sure that is what you were using and not an acrylic?? I suggest you not cut all the way through your blank. Leave about 1/16" to 3/32" material left and now fill in the kerfs with the exact size material of choice to match the kerf of the blade. This is basically how Celtic knots are made. I prefer 2 part epoxies. especially when gluing in tubes. The tube will lock all pieces together for a strong bond.

 

[magpens]

Abandon CA for segmenting glue-ups.

Stick with 2-part epoxy, as John said.

 

[Penchant 4]

What would you recommend as a substitute material?

I have had excellent results, with CA, using Segmenting Accents, a product available from Bear Tooth Woods in several solid and layered colors. I scuff the surface of the accent material with medium grit sandpaper, clean it off; and bond it to whatever other material...wood, resin, other accent sheet.

 

[ndep]

I have had excellent results, with CA, using Segmenting Accents, a product available from Bear Tooth Woods in several solid and layered colors. I scuff the surface of the accent material with medium grit sandpaper, clean it off; and bond it to whatever other material...wood, resin, other accent sheet.

Do you know what type of plastic Bear Tooth Woods is using in its segmenting accents?

 

[jttheclockman]

Do you know what type of plastic Bear Tooth Woods is using in its segmenting accents?

It is an acrylic sheet that was designed for the Gisis's and they took ownership. They are very flexible. They are actually precision inlay material with exact trueness in dimensions which makes them a bit more expensive. But if you want accuracy they work well. If you ever used pickguard material you will notice that many times if using multi layered material that one side of the layer the outside layer is thinner than the rest because they adhere them and then sand to finished size. Many times you may not see it but I have over the years and basically stopped using it.

 

[Penchant 4]

Do you know what type of plastic Bear Tooth Woods is using in its segmenting accents?

I could not say, with authority. A solvent used to bond ABS, Styrene, or Acrylic does attack the surface of a sample piece. Texas Knifemaker's Supply is another source for the material in larger pieces (6" X 12") than the size Bear Tooth lists (3" X 6"). That source calls it 'engraving stock' spacer material. Whereas Bear Tooth offers multiple colored layers as well as solid colors; Texas Knifemaker's appears to only carry solid color through the 0.024" thickness.

 

[Todd in PA]

I try not to sand segmented blanks at all. If you practice you can get a very smooth surface with a skew...

Firstly, I'm pretty new to pen making.

I also received this "no sanding" advice when I suggested that I wanted to try incorporating some aluminum into a blank. Ken, Hank and others said the aluminum dust would soil the wood grain and so I should not sand aluminum. Being new, I figured this is graduate level technique. Happily, it is NOT that hard. With only a small amount of practice I am able to get a very clean-- better than sanded-- finish on a blank with a skew. It saves a lot of time in sanding and so I now always finish my shaping this way whether or not I used aluminum.

My technique, which I'm sure came from a youtube video somewhere, is to raise up the tool rest slightly higher than center, and touch the sharpened skew to the lower half of the blank, gently. The scraping cut produces fine dust, not chips. I have tried the same with a square tip carbide, and can get close to the same results, but sometimes have trouble if the blank has any roundness. The skew must be sharp. Give it a try and don't be intimidated!

Todd

 

[KenB259]

Firstly, I'm pretty new to pen making.

I also received this "no sanding" advice when I suggested that I wanted to try incorporating some aluminum into a blank. Ken, Hank and others said the aluminum dust would soil the wood grain and so I should not sand aluminum. Being new, I figured this is graduate level technique. Happily, it is NOT that hard. With only a small amount of practice I am able to get a very clean-- better than sanded-- finish on a blank with a skew. It saves a lot of time in sanding and so I now always finish my shaping this way whether or not I used aluminum.

My technique, which I'm sure came from a youtube video somewhere, is to raise up the tool rest slightly higher than center, and touch the sharpened skew to the lower half of the blank, gently. The scraping cut produces fine dust, not chips. I have tried the same with a square tip carbide, and can get close to the same results, but sometimes have trouble if the blank has any roundness. The skew must be sharp. Give it a try and don't be intimidated!

Todd

You will never be sorry for having learned how to use a skew. The Sorby spindlemaster is an under rated tool that can be used in place of a skew. It is far less intimidating and they come in various sizes including pen size. Also very easy to sharpen.

 

[henry1164]

You will never be sorry for having learned how to use a skew. The Sorby spindlemaster is an under rated tool that can be used in place of a skew. It is far less intimidating and they come in various sizes including pen size. Also very easy to sharpen.

After your kind words on the Sorby Spindlemaster I looked at that item and saw a couple of videos. Looks like something that zI would want. Your opinion please on the size I should get (can only afford one now) - 1", 3/4" or 1/2"? I would use it only on wood and acrylic pens. Thanks.

 

[KenB259]

After your kind words on the Sorby Spindlemaster I looked at that item and saw a couple of videos. Looks like something that zI would want. Your opinion please on the size I should get (can only afford one now) - 1", 3/4" or 1/2"? I would use it only on wood and acrylic pens. Thanks.

My opinion the 1/2 is the best size for pens.