Shopsmith Forums

This is my 2nd bowl. I had a few tool marks on my 1st attempt, but they weren't this bad. I've tried sanding them out with 120 grit, but I'm not making much progress.
How do I prevent or correct this? I'm shaping at 745 RPM, using carbide tools (S1 and R1 tips), and sanding at 945 RPM.

I am guessing the tool was not held securely enough to prevent digging in.

I'm not that much of a bowl guy but from my note book this table seems like it might be useful for you:

The rpm will vary, but a general rule for getting a concept are these published recommendations from Dale Nish:

(Diameter, roughing rpm, finishing rpm)

5" 1200 to 1800
6" 1000 to 1500
7" 850 to 1250
8" 750 to 1125
9" 650 to 1000
10" 600 to 900
12" 500 to 720

Sanding is always best done a lower rpm. While cutting is the best way to get to the finish you can sand but you might have to go to say 80 grit and work your way up. Keep in mind the sandpaper is going to leave a lot of scratches so these have to get taken out by finer paper, a slow and less refined way to go.

The wood you use is always a major consideration, wood with a hard/soft grain pattern is harder to work with then one with a pretty consistent hardness.

While carbide tools are in use it is always nice to have a fresh edge to do finishing. Some people have an insert they use for ruffing then switch to another one for finishing.....

Now some of the bowl turners can add some more experienced advice..... I can only talk of turning in general.

Ed

Hard maple, right? Especially hard to not have tool marks at end grain with the carbide easy wood tools.
I’m fighting the same battle. I’m hoping to have better results next time using very sharp “fingernail style” bowl gouges with very light final cuts.

[youtube]https://www.youtube.com/watch?v=qnym1IyOPgE[/youtube]

[youtube]https://www.youtube.com/watch?v=xBNAkRe9bxw[/youtube]

[youtube]https://www.youtube.com/watch?v=kBydG7sWSRI[/youtube]

are` you using a single or double bearing quill ?

If you are using the very small carbide cutters they will sometimes leave tool marks that are difficult to remove. For final cuts I use a bowl scraper and take a very light cut. The wood will come off like very small wisps of wood almost like snow flakes..
The very small cutters can leave a groove on the surface similar to the groove on a record. (Please don't ask what a record is)
Following with the same cutter will have the cutter follow in the previous grooves. Using the larger radius bowl scraper will bridge the small grooves and remove the ridges. Then you can start sanding at 220 rather than 80 grit.
Bill V
PS JPG is also correct about holding the tool securely.
Remember the ABC rules of turning
A ANCHOR the tool on the tool rest
B Rub the BEVEL
C Make the CUT

Thank you all for the great information.
I found some 60 grit, so I went over the inside with that. I still have just a few marks; I know they're there (and y'all may see them), but I think most people won't notice. I'm satisfied with it as it is, so I can move on.
I went 60, 120, 220, 400 and 600.

krzink wrote:Thank you all for the great information.
I found some 60 grit, so I went over the inside with that. I still have just a few marks; I know they're there (and y'all may see them), but I think most people won't notice. I'm satisfied with it as it is, so I can move on.
I went 60, 120, 220, 400 and 600.

She looks great, krzink!

I had the same problem with my first, and so far only, bowl. Before I turn another, I plan to get a scraper with more suitable profile for large bowl interiors. Something like the one at the link below.

https://www.woodcraft.com/products/sorb ... ng-inboard

Using the carbide cutters means you are scraping the wood and not cutting. Try using a gouge with a very sharp fingernail grind or a scew and cut instead of scrape. You will need to adjust the speed according to the type of wood. You can achieve very smooth surfaces that require very little sanding that way. It takes practice but you should be seeing shavings from cutting and not chips from scraping. If you are going to buy new chisels I highly recommend Thompson Tools. Very high grade cryogenic steel that holds an edge considerably longer. You can buy his handle system or make your own. Making your own is a lot of fun. A great way to practice working with your chisels is turning spindles from scrap wood. Sanding to a mirror finish is not difficult but it is a process. I start with 80 grit and go up in 80-100-120-150-220-320-440-600 increments and then to 0000 steel wool. At the 80-100 level reverse the direction of the piece. If you have a Mk7 just hit reverse. If you have a Mk5 take it off the arbor and switch it to the other side of the headstock. When you get to the 220 point stop and look for rough spots. There will always be some. I go back to the 150 and hand sand those areas with the machine off and then proceed back to 220 and progress through the grits again with the machine running. Hope all this helps.
Paul