|Project by Elyasaf Shweka||posted 04-01-2014 07:54 PM||12243 views||69 times favorited||19 comments|
My thickness drum sander is based on a machine built by Pat Hawley. free plans were drawn by Matthias Wandell and can be found here.
I also referenced (and consulted) Ron Walters sander, which can be found here https://woodgears.ca/reader/walters/drum_sander.html
and made some use of these old plans http://carllance.files.wordpress.com/2008/04/drum-sander.pdf
i found additional information on luthiers (guitar builders) forums, since they use this machine regularly for thickening the guitar top.
the machine is not a hard one to make, and building it is not that complicated, and the parts are not expensive, but it took me a long time to build, since it was hard to find the right parts here in israel, and ive orderd the velcro sandpaper from the states. also i had to built it all over again (twice!) since it wasnt accurate enough. now, when i am much smarter, i assume that it can take 1 day to built, if you have all the right parts with you. not such a big deal.
since i make 3d end grain cutting boards, i figured that this is the only right way to sand those boards. planer cant be used due to the end grain or the changing directions of the grain (with none end grain projects). matter of fact is that instead of approx. 4 hrs of unhealthy and annoying sanding for a board, which gives a non-satisfying finish, i now get a superior finish in less than 12 min.!
motor – 1 hp 3 phs 1200 rpm, pulley
drum – 14 cm diam. birch plywood
table – tilting granite (!), 50 cm width
thickness – from 3mm to 45mm
final rpm – 500
acrylic sheet cover, with high accuracy box joints, made with laser cutting machine. very efficient dust collection. it is very useful to see the wood while its sanded, and im very proud of this cover…
construction made mainly from beech
drum is covered with Velcro (male) and sandpaper comes with female Velcro. for quick replacement
video of the sander at work:
some detailed information about the built:
1. Frame: my first attempt to build the table was with 2”X4” standard pine. i used screws without glue, and after a while of moving it around the workshop, I noticed that the frame got unstable and not aligned. I decided to knock it down and to build it all over again, properly this time. I switched some parts from pine to beech, used glue and screws, added half lap joints (made with the tenon jig), and paid high attention for the overall accuracy.
2. Granite table: on my first attempt i used a double layered 17 cm beech plywood, and i laminated the top. after a few days, I noticed that the table got curved, about 1 mm height on 50 cm width. i assume this happened because only one side was laminated. i was looking for a sturdy material to make the table from. a friend suggested using granite stone as a flat surface. my first thought was that its too heavy, too weird and all over ridiculous, but after giving it a second thought, i decided to try it out. apparently, granite stone is very hard and stable, hard to scratch and can get a fine finish when polished. i was surprised to learn that in applications that require fine flatness, granite stone is used. surprisingly, most professional and expensive pool tables have granite stone as a base for the green cover. i got a nice scrap of high grade granite stone from a kitchen countertops guy. a piece of 50X60 cm weights around 7 kg, and adds robustness to the machine. I am quite happy with the smooth finish and the nice look of it. and it works well with wood, too :)
I had a very annoying problem with the alignment. while sanding the drum to get it leveled with the table, i found out that i am getting a cone shape instead of a cylinder. it took me some time to realize that my surface (table) is not parallel to the drum shaft. it was solved simply by adding some shimes under the lower bearing, but it seems to me that this should be solved easily with a better design. I am not sure how, but i believe that the shaft bearing should lay on the same beams that holds the table hinges. this way the leveling of the surface and of the shaft would be the same.
4. Drum – i used a simple circle jig on my band saw to make the round plates. it seems that the results were not as accurate (me and the band saw don’t get along very well), and ive spent many hours of irritating sanding to get the drum to a perfect round. one of the smart features of this sander is that you true the drum on the machine itself. before gluing the velcro, you true the drum by putting a sandpaper on a board and putting it on the table under the drum. this tures the drum to the table.
after a while of sanding, the round drum started to slip on the shaft. the friction wasn’t enough to hold the drum on the shaft (it wasn’t clear from the plans how to attach the drum to the shaft and i thought that the friction would be enough – big mistake!) i contacted Ron Walters to find a solution for that, and he gave me his opinion, initially, i drilled 6 mm hole from one side to the middle of the shaft, inserted a metal rod and covered it with a wooden plug. now the drum is firmly attached to the shaft – forever… i also canceled the 1 mm gap between the groups of the layers. i glued them all together to one firm piece. with no doubt i should have order the round plates from a CNC machine guy, that would save me so much trouble, sanding and dust. or at least i would do the circle jig on the table saw, this way getting better results.
5. Lift mechanism: im not sure how, but i need to find a way to lock the lift mechanism. while operating the machine, the vibrations tends to move the handle a bit, and thus changing the height of the surface. ive switched the threaded rod to a thicker one, but it is still wobbling a bit.
6. Dust cover
the first that i have noticed while working with the sander, is that its not practical to have a wooden cover on the sander. it is really important to see what is going on, and i wasn’t pleased with the fact that I can see the wood while its being sanded. I designed a box made from 6 mm perspex (acrylic sheet), and carefully designed the box joints to be cut in high accuracy laser cutting machine, so the pressure of the material would be enough to hold it tight in place with no gaps. i love the cool look of the result.
7. Lockable wheels
since I am working in a very tight space, I store this machine in a room next to my work shop. to help moving it around, I added 2 lockable silicon wheels. they look cool too :)
-- Only by the 4th time I realized how it was suppose to be done in the first place.