What did I do wrong? Chip out on square turning

[MarkAndrews]

I'm attempting to turn a 6" square edged bowl. This is the first time I've turned something that wasn't round. I'm actually really pleased with how it's coming out but I did get some chip out on one of the edges that had end grain (see pic1)1. I'm wondering how to avoid that? I used both a 5/8" Bowl Gouge and I EasyWood Easy Finisher. Both worked well and I took very light passes (or at least I tried to). I had the bowl spinning at 1000rpm. It seemed like the faster I went the the better the result. I used a SuperNova 2 Chuck with the worm screw screwed into the face along with a flat tail stock (see pic2) against the bottom, so I think I'm working safe. There was a little vibration when I started but it disappeared once I started taking it down.
I'm using poplar as a test run before I commit a nice piece of wood to the bowl. I got the idea from this web post http://bobhamswwing.com/Articles/LiddedBowl/Turning a Lidded Bowl.htm and then watched a YouTube video by the Naked Turner https://www.youtube.com/watch?v=5vZ6XLlkkVE
Any suggestions?

 

[john lucas]

You have 2 potential area for tearout on square bowls They are the two areas opposite each other where the cutter is going uphill into the grain. If you turn the bowl in reverse these 2 areas will cut clean and the 2 opposit corners will get tearout. The way to reduce this is to use sharp bevel rubbing tools and most importantly don't force the cut.

Don't use a scraper I do t care if they do call it a finisher. Also reduce the amount of pressure you put on the bevel. I know we say ride the bevel but in this case you should glide the bevel If you listen the wood will tell you. If you push on the bevel you get a fairly loud noise as the wings of the bowl hit the tool. The lighter you are on the bevel the less noise it makes.

I practice this cut frequently since I turn so many mirrors. They start as square. Since I know I'm going to turn this area away I can feel free to try different cuts to see what works best withou worrying about ruining a project

 

[Bill Boehme]

I would try making a shear cut if you are familiar with that type of cut. It is somewhat similar to a shear scrape except that it is a bevel rubbing cut. I usually drop the bowl gouge handle really low and let the bevel just barely make contact with the wood. Having a very sharp edge is critical or else you will find yourself pushing the tool against the wood. The orientation of the square also makes a difference. If two sides are parallel to the grain direction and two sides are across the grain, there will be a more pronounced difference than orienting the square so that the sides are all on a 45° diagonal with the grain. Finally, I see one other thing -- the exterior slope of the bowl is rather steep because of the large diameter of the foot. If you reduce the size of the foot to a much smaller diameter ... say roughly a third or half the present diameter then the cut will be more like a rift cut that ought to cut more cleanly where you are now getting tearout because it is currently more like a cross grain cut.

 

[hockenbery]

John and Bill have good suggestions.

If you use a side ground gouge I would suggest trying a pull cut.
This gives me a great surface on an interrupted cut and it also forces a light cut.
Usually cuts the bark well on a natural edge form which is the problem you have cutting into air at the rim no fibers supporting the cut coming into air.

Light cuts, sharp tool, light cuts, high angle of the pull cut, and light cuts.

Poplar is a good test wood. It splits easily and if you can turn the poplar cleanly you will likely succeed with harder woods.
You might try a soft maple test bowl too it would be more tolerant of cuts into air.

Have fun, Al

 

[Ian Robertson]

One of the best videos I have seen on the subject: https://www.youtube.com/watch?v=Vmz5BKXBGLA

 

[MarkAndrews]

I would try making a shear cut if you are familiar with that type of cut. It is somewhat similar to a shear scrape except that it is a bevel rubbing cut. I usually drop the bowl gouge handle really low and let the bevel just barely make contact with the wood. Having a very sharp edge is critical or else you will find yourself pushing the tool against the wood. The orientation of the square also makes a difference. If two sides are parallel to the grain direction and two sides are across the grain, there will be a more pronounced difference than orienting the square so that the sides are all on a 45° diagonal with the grain. Finally, I see one other thing -- the exterior slope of the bowl is rather steep because of the large diameter of the foot. If you reduce the size of the foot to a much smaller diameter ... say roughly a third or half the present diameter then the cut will be more like a rift cut that ought to cut more cleanly where you are now getting tearout because it is currently more like a cross grain cut.

You are absolutely right Bill. The sides of the bowl turned out way too steep (see pic). I'm going to try again today. I will definitely make the bottom smaller and I will try reorienting the grain. I'll also try the shear cut with light pressure. I'm still really unsure of myself when it comes to using a bowl gouge but that's what practice pieces are for!
What about speed? It seemed like the faster I went the smoother the cut. Is 1000rpm too fast if I'm using the worm screw and I've got the tailstock supporting the piece? Can I go faster safely?
Thanks again to everyone for all your input...it's invaluable.
Mark

 

[robo hippy]

Ian's link to the Jimmy Clewes video is an excellent one. I have seen some who glue wast blocks around the square, then cut them off when done with the round turning, but that is too much work for me. The higher shear angle, meaning the cutting edge is square to the rotation like a scraper flat on the tool rest, but as high on its edge as you can make it. So with a swept back gouge, you drop the handle as much as possible, and hold the gouge at an angle of 60 plus degrees off plumb. The steep angle makes for a high shear angle and the cuts lift off more than scrape off. Better to start a project like this one with some cheap wood. I also like how Jimmy cuts backwards as on the outside, rather than cutting from the base to the rim, you cut from the rim back, and take very gentle cuts.

robo hippy

 

[Bill Boehme]

Mark,

I watched the entire video and have to agree that it is excellent. One of the things that Jimmy shows is cutting in stages. He sort of glossed over it, but that a very important tip when cutting something thin and especially something like a winged bowl whether it is square, triangular, or natural edged. By working in stages, it provides more support to the thin wing tips and minimizes flutter. Something that I don't believe that he mentioned is once the outer portion has been properly shaped and you move on to refining the next stage, do not go back to the first stage and try to do any further refining. Instead, it would be better to take care of any final tweaking by sanding with the lathe turned off. A turner like Jimmy is able to get away with breaking that rule because of his skill, but you and I wouldn't be so fortunate.

 

[MarkAndrews]

Square Turning Part 2

Thanks to everyone who advised me on how I should handle the challenges I ran up against the first time I tried to turn the square bowl. To classify my first attempt as a failure would be an understatement, but the challenge is half the fun and that's why we try new things right?
The Jimmy Clews video was fantastic. I honestly watched the first 10 minutes of the video at least 20 times. I also took to heart everything that was stated about using the bowl gouge instead of the Easy Wood scrapers. 95% of the second bowl was done with the bowl gouge. I only used the scrapers to get into tight curves that I just couldn't get into with the gouge.
I cut the blank as Bill suggested with the end grain oriented toward the wings. Basically I took an 8" blank and drew a diamond pattern in the center of it. I cut the sides of the diamond off with a chop saw at 45 degrees. I ended up with about a 6" blank. It worked out really well, I had very little tear out on the end grain and almost no chip out.
The other thing I did differently was turn the speed of the lathe up. I did most of the work at 1500 rpm. Initially I was a little intimidated, but the results were so good that I began to relax and enjoy it. This was another topic that Jimmy Clewes spoke of briefly during the video. For a new turner, we hear all of the cautions about not having the piece fly off and it's scary. But if you support the work with the tail stock and have it chucked up properly it works very well. Doing a push cut into air was scary as hell but it worked. Pull cuts on the top were a breeze when using Jimmy's technique. It was the first time I felt like I was in complete control of the ultimate shape of a piece I was turning.
I'm attaching pics of the end result. This is still a practice piece, turned in Poplar and not finished. I've sanded it to 320. I'd appreciate any feedback or suggestions.
My thoughts are that I don't think I got the ogee correct on the wings. i would have liked to have had a more bird wing appearance. The knob is too big but that should be easy enough to correct. I also didn't account for the depth of the bowl when I was laying it out. It came out OK, but I was a little concerned when I started forming the bowl. I have to finish the foot, I was lazy and didn't want to hook up my vacuum chuck, but I will definitely do that.

 

[Ian Robertson]

Pretty good effort for only your second one.

 

[hockenbery]

Mark,

Success! !

Now do a few more. Each one will be easier. Your confidence will grow.
Look at each one with your own critical eye.

Think about the form and where you might make a subtle changes, a different top, a different curve, a thinner here or thicker there.....

For instance you could use a thin finial for the top. Then it becomes non functional. Just things to consider.


Al

 

[Bill Boehme]

Congratulations, Mark. Getting over the fear factor is the biggest hurdle in learning to turn. When you're hanging on for dear life, it's hard to be creative. When you feel like you are in control then the white knuckles disappear and the tool does what you would like it to do. It's a great feeling.

With each turning that you make you will see where things can be refined. Be sure to keep your early pieces. They will serve as a gauge to show you how you have progressed over time. I don't think that any of us reach the point where there is nothing new to learn so continue to share and take every opportunity to expand you horizons.

 

[janetfdoss]

Really informative

One of the best videos I have seen on the subject: https://www.youtube.com/watch?v=Vmz5BKXBGLA

It is really informative and helpful video links. Thanks for sharing