Archive for December, 2011
A lot of folks there expressed interest in turning bowls, and now that I’ve got about 100 under my belt, I think I’m ready to tackle it. The trouble is that it takes more than a couple of hours to teach bowl turning, especially with several students, so I’m going to work on a class model where 2-3 students work on a single bowl and the finished product goes on display at TechShop.
There are only two lathes at the shop, and really only one is good enough for teaching. That means there isn’t enough time for everyone to turn their own project to completion.
So I’ll be putting the class handouts together here in sections as blog posts. It’ll be a compilation of the steps, skills and techniques I’ve learned from other turners and gathered from my own experiences over the last few years. I guess I should technically call it “how I turn a bowl.”
Stay tuned for posts in this series on topics like:
- Wood Selection
- Mounting a blank
- Turning the outer shape
- Establishing the foot
- Hollowing the bowl
- Final foot detail
- Sanding & finishing
I finished my platter plans for the holidays with these six offerings. All are in the 11-12″ range and have been laser etched with family names and dates — weddings and birthdays — to personalize them.
After watching a Mike Mahoney demonstration on heirloom pieces, I got the idea to create platters that could serve to honor families in much the way we used to mark the inside cover of old bibles with the birth of each new child.
These are designed to be somewhat functional platters, but really intended to be displayed on the mantel or left on the family dining table to be seen, not filled.
I used the Epilog laser at TechShopRDU to etch the pieces after spending several hours planning the presentation and process.
The design was done on the computer using Corel Draw after taking the critical measurements of each platter… diameters of each piece and any special beading or curve details that needed to be taken into consideration.
The text was then typed in and set to follow the curve of the appropriate diameter. After significant experimenting, I determined the best look was to place the family name across the top — looking down on the piece — in a slightly larger font. For the rest of the rim, I flipped the text to be read from the outside and filled it with the names of the married couple, their wedding date, followed by the names of each child and their birth dates.
For smaller families, I used the complete names with “born on January 13th, 1993″ formatting. For larger families, or for grandparent versions, I simply used name and ##/##/## formats.
I struggled with fonts for a while, but settled on a freehand script for its more formal and artful appearance.
Alignment would be tricky, but I had a plan worked out based on my previous experience with the laser.
The laser driver has an option to draw from a set center point instead of a top-left x/y axis. It also has a red light indicator to let you run the tool path without doing any etching. Lastly, it also let’s you print simple outlines in the much faster vector mode — following the drawn lines — rather than raster which moves like an old dot matrix printer in tiny increments.
So at the laser I set the center point somewhat randomly near the middle of the bed. After setting the focus to the height of the printing region for each particular platter, I dead-reckoned the center alignment for each platter. Then in vector mode and with only the preview laser on, I “printed” the critical diameter onto the platter.
The single-line job only takes about 20 seconds to complete at 100% speed, so I watched the laser light trace across the piece and nudged it as needed, running the print job a few times to make sure I was as close as possible.
I made sure in my designs that the actual offset from the critical diameter was sufficient, and even increased that a bit on the fly when the laser showed that the platter was perceptibly out of round. The farther from the edge or line, the less the eye would notice the changing gap.
This worked well for all but one platter, which was so wet when I turned it that it was now far from round. I measured the difference in diameters from horizontal to vertical, which was now more than 1/2″, and adjusted my circle in Corel to match that more oval shape. Problem solved.
Almost solved, anyway. The shape change also increased the height of the lip across the shorter dimension — the patter curled up — which meant the focal point would be different. I decided to chance it and really there was negligeable difference.
This etching process sounds pretty reasonable, but the fact is you only get one shot at this because there is no way you could move the piece and hope to get it back to the exact same position for a second run.
So for the first few I even ran the preview mode on the entire text — in vector mode — to make sure the path would work as predicted. Then I crossed my fingers and let it run for real. The vector jobs ran in under 10 minutes each, depending on the quantity of text. I ran at 100% speed and about 50% power on the laser. The pieces were already sanded so I wouldn’t need the etching to be very deep, and you can’t be sure how some woods react to the laser heat.
By the second run I decided to follow the vector job with raster, to fill-in the outline text for a more consistent effect. Since I didn’t touch the piece in the laser, it was perfectly fine to run the second job on top of the first. The raster/etching process took much longer to complete, however, between 15 and 20 minutes each run.
This was all well and good until the severely out-of-round piece. I thought I had checked the clearance well enough, but I guess the raster operation covers a bit more surface area because about two-thirds through I heard the platter get knocked aside by the printing head. I moved just quickly enough to stop any serious damage, but what happened was that a piece of air-flow tubing on the printing head just touched the highest point of the curled-up rim.
Luckily I caught it before another pass destroyed the work, but now I could not finish the raster etching because the piece was moved. If I tried it, I would most certainly end up with a ghost or shadow etching offset form the first run. Even more luck — where the etching stopped was where some spalting had darkened the wood enough that you wouldn’t notice the lack of filled-in text.
In all I etched five platters in about 2 hours of time on the laser, though I spent much mo time in the design and planning stages at home. I’ll be doing this again, I’m sure, depending on how well received these gifts are.
At some point, I want to try etching images across a wide rimmed platter, but I need time to figure out a good way to bend them to the curve with minimal distortion.
The holiday pressure has me turning at a higher frequency these days, thankfully. I was enjoying platter work so I wen looking for more blanks. My EBay supplier NCWood had a few waiting auction, but I wanted some for the weekend so I gave him a call.
He had some Ambrosia maple and black walnut at 12″x2″, but nothing larger. He cuts those sizes to maximize his eBay/mail business. I suspected the maple was very wet from the weight of the blanks, which he said were cut and waxed a few months ago.
They were wet indeed. At several stop points there were a few water drops hanging from my tool edge and the shavings curled and flew as I rounded the piece. Given the dramatic moisture, I especially had to work fast and finish the outer areas before progressing toward the center.
I got through the first blank fairly quickly, bagging it on the lathe with plastic while I broke for lunch. It didn’t appear to warp while I worked it, but I really and to sharpen my tool for final cuts to limit the end grain fiber tear-out. Scraping took down any ridges in my work, but did nothing for torn end grain. There was also some slight cracking in two spalted areas along the rim, but it looks like I hit them with thin CA glue early enough to stop them from spreading.
There were several holes from the ambrosia beetle, and I left the unfilled to give the piece more character. The beetle leaves tiny, clean holes that do little damage to the wood integrity, but many of them go all the way through.
The finished work was down to about 3/8 and even thickness, which is good because the edges began to warp in less than 24 hours.
Sunday I decided to try the lack walnut, which was lighter and therefore much more dry. The smell of fresh-cut walnut is quite nice, but the dust level from this dry piece was enough to send me for breathing protection. After working the wet wood yesterday, this walnut seemed to put up more of a fight. But it was worth it. The luster from the dark grain is gorgeous, especially after adding a coat of seal-a-cell to protect and give it that wet look.
Sanding was a bear though as I had more end-grain tear out to deal with. I tried some mineral oil to raise the fibers, but that just destroyed my sandpaper. I switched to one more scraping pass to try and eliminate the tears as well as scrape away the oil so I could complete the sanding.
I chose a closed-lip shape which forced me to do a bit more scraping than cutting, so I should not be surprised at the tear out. I’m not 100% happy with the shape, but I’ll admit I rushed this one a bit. I think the color and grain make up for my weak design detail.
Still have another wet ambrosia maple blank to work on this week. Will have to try different shape this time. Perhaps I’ll try a square cornered platter this time, if there’s enough room over the bed to swing the blank.