Question about a new wood…
March 22, 2010 by admin
Filed under Router Tips
Has anybody uses Robusta?
Here is the answer from the wood expert Keith Stephens…
John, I would be pleased to comment on the wood but we need to sort out what it is. Robusta is species name associated with several trees. Grevillea robusta, Australian Silky Oak, would be a likely candidate. Here is our information page:
Here is John’s problem:
OK John, Maybe someone out there can shed some light on the characteristics of the wood you are using. In the mean time I have a few suggestions as shown below:
The feed rate and the width of the pieces,
The feed speed is one of the most important part of making cuts with the router. I would suggest two things 1) increase the width of your pieces to match 2 X 4 or 8 inches. Then when you have the joint on the ends you can cut the pieces apart to match the desired 4″ width. To prevent the burning you need to experiment with the speed of the feed past the router bit. This is a practice thing
Next the spiral bit…
The problem with the router bit pulling the piece out of your hand is one of the evil trates of the spiral bit. This will always be there and can happen with about ever kind of wood. Once you realize the trates of the spiral bit you will know how to hold it into position.
It sounds like maybe he had the wood between the bit and the fence… In other words, on the wrong side of the router bit and the bit took the wood away from him. It happens!!!
Try a down spiral bit … it may help hold the work piece to the table.
That is what he is using…Rick
I assume he is using the up cut spiral bit because the router bit is pulling the debris out of the hole or in this case out of the dado and towards the router. The spiral bit is pulling the piece forward, which is something prevalent with all spiral bits…It is not moving the piece off the table.
Not sure changing to the down cut spiral is go to work better because now you are pushing the waste material into the dado and not pulling it down into the router. Making it so the waste material has no place to go but up into the dado…
Just my thoughts,
Rick
John, I would be pleased to comment on the wood but we need to sort out what it is. Robusta is species name associated with several trees. Grevillea robusta, Australian Silky Oak, would be a likely candidate. Here is our information page:
http://www.woodworkerssource.com/online_show_wood.php?wood=Grevillea robusta.
If that is not the wood post some information about the wood you have. Where it came from, the weight and denisity, color, hardness, anything at all and some pictures showing both the face and end grain.
Keith Stephens
keith@woodworkerssource.com
Keith, Eucalyptus robusta is the most common introduced species to Hawaii. It grows to between 50 and 100 feet tall and 4 feet in diameter. When young the wood is light red in color and turns to dark mahogany color with age. It is very heavy with a speciific gravity of .8. It is quite hard and cannot be worked by any but the sharpest tools. See http://www.hawaiiislandhardwoods.com/hawaiian.html
john stark
Thanks for the specific identification. While several species of Eucalyptus are available on the mainland I am not framilar with this wood but found a great write up. http://www.fs.fed.us/psw/publications/documents/psw_rp009/psw_rp009.pdf
The paper starts with this quote:
Many adverse opinions are expressed, such as : “Eucalyptus? it’s brittle–too heavy–too weak–too hard–splits in nailing–can’t be dried!” While the paper offers some alternative opinions, it is clear that Eucalyptus robusta is one tough customer.
Sharp carbide cutters, light cuts, a slow feed rate and the right router speed are all needed to work any of the super hard woods. Experiment with different set ups. A holding jig might be helpful to minimize any unexpected movement.
Keith Stephens
What I finally did to complete the job. This solution is probably only practical for “one of a kind” jobs.
I took the pieces that required the Dado portion of the joint over to my table saw crosscut sled and plowed a one quarter inch groove through the center of each three eigths inch dado location to create a tunnel for sawdust. it allowed me to much more easily use the jig to complete the Dados. I didn’t go the full width of the Dados because I liked the fit obtained using the jig. I did the rabbitts on the jig without any use of the table saw.
john stark
Thanks for the comments John…Rick