Learning Curve help

[Kirk Amidon]

I've now got about 10 bowls under my belt, some are just roughed and drying, others were turned to final thickness and are drying. The main wood has been maple and cherry from my yard, green. Thought it was high time to see if I can make more progress. I've searched and read many of the threads here on the topics where I've wanted help, as well as watched many you tube videos by various turners (Stuart Batty, Robohippy, Brian Havens, Wyoming Woodturner, etc.) I've been able to learn and make progress emulating some of their approaches.

There are two main questions I have, and they may be related to one another so I'll put them both here.

One involves the set up of my lathe, and stalling, the other is a bouncing tool.

Bear with me through some background.

My lathe is a Rockwell Delta 12" gap bed lathe, circa 1972, Power is a 3ph .75 hp motor with a Teco 510 VFD. The lathe has a reeves drive - the cable version. Speeds go from about 350 to 3000 or so through the Reeves, and with the VFD, can go down to nothing. Upon receiving the lathe, I dismantled it, replaced bearing in head stock, tail stock, and I think the reeves drive as well.

I'm finding that I can stall the lathe pretty easily when first roughing a bowl blank. Mounting the wood so that the ends at the tailstock and headstock are side grain. As I make my first cuts across the blank, from tailstock to headstock, it seems to stall occasionally. FWIW, much more frequently on the headstock end. When this happens, I can see the wheel on the left side of the headstock is stopped, telling me the slippage is underneath, with the belts. Might this be caused by insufficient belt tension? When I got the machine, I don't know the belts were correct for it.

Second related question, when roughing across the blank, as well as when evening out the face grain on the tailstock end, I'm constantly fighting the bounce/chatter. Just can't seem to get a smooth flow. It feels like I'm fighting the cut, and I'm definitely using more pressure than is described in the various videos, where they are able to easily and smoothly make this cut. I've tried a number of ways of rotating the tool, as well as the angle of the handle, trying to follow the bevel. This bouncing occurs with both push cuts and scraping cuts. At this point, I've got past it my using the tip more and taking much smaller bites. The only obvious difference is that I'm using a 3/8" bowl gouge, while most seem to want a half inch - measured across the flutes, not the shaft diameter. I'm not adverse to buying more tools, but at same time, figure that if I can't make the cut with the gouge I have, just getting a bigger chisel means I can't make the cut with it either.

Obviously seeing something in person would be ideal, but given circumstances, that will have to wait.

Thanks

 

[hockenbery]

I use an Ellsworth grind on my gouges. Roughing is hard to learn on your own so you are progressing quite well realizing a problem.
i prefer the 1/2” gouge (5/8 diameter bar) a 3/8 gouge (1/2” dia bar) will work fine just takes smaller cuts.

1. Cut toward the headstock. Take off the corner first to establish a smooth spot then cut from smooth to rough so that the bevel has a place to float over. Before getting into the interupted cut.

Below is a video of a technique I learned from Christian Burchard. It is an A FRAME CUT. Forward arm is straight. End of the handle is at the top of the thigh. With this grip the tool, forward arm, and torso form a rigid triangle. Slow rotate the body to move the tip of the tool in an arc - the rigid triangle keep the tip from moving forward when cutting air allowing the cut to ride the bevel smoothly through the interrupted cut.

This method anchors the tool on the tool test and keeps the tool from bouncing. It is really effective and I get a really smooth cut on the interrupted surface. When I just cut one or two spots on the corner of a blank they are smooth and no bounce.

This is a video clip from a demo showing that cut.
Cove Ruffing cut

View: https://www.youtube.com/watch?v=EIHADKjfL2c

This is the demo of rough turning the whole bowl.
Roughing green bowl -

View: https://www.youtube.com/watch?v=Lo0bGSafZq4

 

[hockenbery]

One involves the set up of my lathe, and stalling, the other is a bouncing tool.

This is tough without seeing what you are doing since these are symptoms caused by many different things.

stalling the lathe is either too big of a cut or slight catch.

bounging takes all the fun out of turning. Practice good technique and bouncing will disappear.

Marginal Techniques that lead to bouncing:
- not riding the bevel causes to tool to continually want to dig deeper pulling the tool with it.
- tool rest too low - tool tip should be above center
- feed rate fast on an interrupted cut so that the heel of the bevel get hit by the wood after the air gap,instead of being cut by the cutting edge which has move too far.
- Pushing too hard on the bevel the bevel should float over the cut surface.
- Tool tip at the wrong angle keep the flute at 45 degrees or less from level
- not cross cutting the wood - cut from foot to rim on the outside.

 

[Kirk Amidon]

Thanks, hockenbery, I should have mentioned your name in the video's I've watched section of my post.

The A frame has been very helpful - amazed at how much stability putting the butt of the gouge on the hip adds.

Learning new skills is always fun, this process takes me back to learning to ski, and the first few times I felt the ski do the work in the turn, you feel the magic and know what it is supposed to feel like, but you don't have the ability to repeat at will.

Appreciate the thoughts.

 

[hockenbery]

The A frame has been very helpful - amazed at how much stability putting the butt of the gouge on the hip adds.

Be sure to keep the forward arm straight with the elbow locked.
Students have a lot of trouble with keeping the arm straight.

it feels uncomfortable at first and it puts the cutting edge so much further away that other cuts.

let the tools do the work just like skiing

 

[Gary Beasley]

Be sure of your sharpening as well, you will get a lot of bounce out of a dull tool too. As far as stalling run your reeves down slow and variable speed as high as possible for max torque. Aim for the fastest speed that doesnt vibrate.

 

[robo hippy]

A hands on play date would work best... As for stalling, when I was first starting, my lathe had 1/2 hp. I upgraded to a 1 hp motor and that helped a lot. As much as anything else, learning how much your lathe can take off in one pass is important. Sharp tools!

The bounce can happen some what from uneven wood till you get it rounded out. After that, if you have noticed, the firmer your grip is on your tools, the more bounce you get. From an old Hollywood movie, "Hold the sword as you would a bird. Too tight and you kill it. Too loose and it flies away." If you have that white knuckle grip, you not only wear yourself out more quickly, you get a lot more bounce. If you have very sensitive hands, you can also feel a bounce from the wood grain. You cut through end grain 2 times for every revolution of the blank. I tend to hold my tools more level rather than the dropped handle method. When turning the outside of the bowl on a long bed lathe, the dropped handle is more common. When turning the inside of a bowl, a more level tool is more common, in part because the lathe bet gets in the way.

I do have a bunch of bowl turning videos up on You Tube as well. Mostly on bowl turning. Most of what I do is done with the sliding headtstock. Can't remember if I have done one on the differences between a long bed lathe and a short bed lathe, which would be the pivoted or sliding headstocks, or some of the dedicated bowl lathes.

robo hippy

 

[Kevin Jenness]

I found that bolting down my lathe allows me to rough out at higher rpm's - within reason-, making for a smoother cut. You have to use your judgment as to how much stress an out of balance piece is putting on the lathe once bolted down, but it helped me, as did the technique suggested by hockenberry.

3/4 hp is not much and that is a relatively light lathe so you have some inherent limits. Try adjusting the belt tension, but the Reeves drive may just take up the slack.

 

[Kirk Amidon]

Thanks for all the help.

Sharp is always better for sure, but definitely do see this fresh of the grinder, and I tend to run the lathe at full power through VFD and control speed with Reeves to keep the torque.

I'll keep the grip in mind, no sense making an issue worse.

For the belt tension, I'd have to replace one of the belts with a shorter one, as I've got it as tight as possible now. I'm leaning towards one issue possibly being turning too slowly when roughing. Generally, I try to get the speed going to the point where the lathe just starts to move, then back off a hair.

I have successfully made cuts of approx 1/4 inch of material, some of those have been the smoothest cuts reference above, where it is nearly effortless. That gives me some data point.

 

[Gary Beasley]

If you have an issue with the belt slipping and you know the belt is in good shape some old fashioned belt dressing may be in order. I’ve even hit a belt with a quick shot of spray glue to get better grip.

 

[Bill Boehme]

Thanks for all the help.

Sharp is always better for sure, but definitely do see this fresh of the grinder, and I tend to run the lathe at full power through VFD and control speed with Reeves to keep the torque.

I'll keep the grip in mind, no sense making an issue worse.

For the belt tension, I'd have to replace one of the belts with a shorter one, as I've got it as tight as possible now. I'm leaning towards one issue possibly being turning too slowly when roughing. Generally, I try to get the speed going to the point where the lathe just starts to move, then back off a hair.

I have successfully made cuts of approx 1/4 inch of material, some of those have been the smoothest cuts reference above, where it is nearly effortless. That gives me some data point.

I'm glad that you know for maximum horsepower output that it is necessary to have the VFD output at 60 Hz and to control the speed with the Reeves drive. I'm not familiar with the Reeves drive on your older Delta lathe, but I'm sure that it is much better than the Reeves drive on my Delta lathe that I bought in 2004. On my lathe's Reeves drive there is a spring on the motor pulley that takes up the belt slack by closing the pulley halves. This means that there isn't any way to adjust belt tension ... it is what it is. And, using a shorter belt would only make the drive ratio change such that the spindle would run faster.

Generally speaking, variable sheave belts don't look like your typical A-section belt. Instead they are wider and less height and they are also usually Kevlar wrapped belts as opposed to the raw edges of the typical A-section belt. However, on my Delta lathe it didn't take long for the wrapping to be worn to shreds ... and then the rubber would start wearing.

Some of your problems might be caused by the Reeves drive. On my lathe the spindle speed was affected some by load torque. So, instead of running smoothly the speed sort of fluttered around a nominal value, but this fluttering speed induced quite a bit of vibration into the piece being turned. That lathe is now a dust collector, but not in a good way.

My guess about bouncing and smoothness of cut while maybe partially due to the Reeves drive, is likely a combination of technique and tool sharpness. Your earlier comment about fighting the cut and applying excessive pressure. It's unfortunate that you won't be able to get together with a mentor, but in the meanwhile just keep practicing. Make sure that your tools are surgically sharp and that's not much of an exaggeration. Make sure that you're not scraping the wood (no bevel contact). It sounds like you are having dig-ins that are stopping the spindle which is likely the result of the tool not being presented to the wood correctly to have a bevel riding cut.

 

[Doug Freeman]

You might enjoy David Ellsworth demo’ing how to use the Ellsworth grind turning a bowl

View: https://youtu.be/wGupR8Lt9E0

 

[robo hippy]

I am wondering how old this video is... I would guess pretty old. One reason, no CBN grinding wheels. Another, and I don't know if this is related to his 'peeling' cut on the inside of the bowl or not, but he doesn't grind the heel off of the bevel on his gouge. I never liked that cut because as he points out, if you come off of the bevel even a tiny bit, you dig in really hard and have to start another bowl. I haven't used a swept back gouge in 10 or so years. I wore my first one down to a nub, and got a second one that also wore down to a nub, and I had to grind a flat on it so it would fit into the jig. About that time, I learned the 40/40 grind, and how to platform sharpen. With the 40/40 grind and a bottom feeder, I have no need for a swept back gouge. If I want to shear scrape I use a scraper with a burnished burr.

robo hippy

 

[Kirk Amidon]

Thanks again. I watched a couple of videos with David Ellsworth last night, and learned a lot. Also Stuart Batty has some videos on Vimeo which I found very helpful - particularly the ones on defects and left handed turning.

I'm going to modify one of my bowl gouges to an Ellsworth grind later today and give it a whirl. Along with some other things picked up.

In regards to the Reeves Drive. My lathe is the version with the cable control. Belt tension is done via motor positioning, and currently it is a low as it goes, making the belts as tight as they can be. I'm not 100% sure they are right size, as they were not on lathe when I bought it. It does get full motion at both High and low, based on where on the pulley the belts end up.

This is quite an adventure - so many details to keep track of and styles to choose from. That just makes it all the more fun

 

[Doug Freeman]

Yes there are many ways to skin the cat of bowl turning. Learn the different approaches - quite a bit of difference in tools and methods between Stuart Batty and David Ellsworth. One thing they have in common - using the body to control tool movement. I think it’s good for folks to learn different tools/grinds/methods and over time pick what they like, or develop different methods for different situations.

 

[Kirk Amidon]

Quick update - turned another bowl last night, and definitely made progress. What was different? Sharpening. Originally my gouge was more of a traditional profile at 60 degrees. Sharpened the wings back significantly more. Tried a lighter approach, particularly with the left hand. However, this gouge is a Benjaman's Best, and the handle is much shorter than my other Sorby gouge. This made it tougher to make that firm A frame triangle. Additionally, I added more speed which also helped. I figured that while experimenting, I should take it out on the cheaper gouge and reserve the Sorby for when I've got the profile that works for me.

Still not able to fully hog off material like I've seen others do, but the cuts were definitely smoother, and stalled the lathe less often. Need to focus more on tightening the tailstock early as well. Some of the stalls are due to inadequate tension, but still had a few where the headstock stopped too.

On inside of bowl, I was able to make a full cut from rim to center multiple times. The gouge I usally use, is a sorby with a 40 degree bevel, so using this gouge with the 60 meant it had to be further away from my body at the rim. Once I got the hang of that difference, the only real issue I seemed to have was about halfway through the arc between rim and center, where the cut got really bouncy many times. What was strange, is that it then smoothed out as I went across the last 3 inches of the bowl bottom (10" bowl).

Thanks for all the advice here, I've found it really helpful, and after the rain passes, I'll go back out and spin some more. Might make a new handle for that Benjaman's best gouge to make it closer to the length of the Sorby. Since I have an abundance of Maple right now, that is what it will be.

 

[hockenbery]

the only real issue I seemed to have was about halfway through the arc between rim and center, where the cut got really bouncy many times. What was strange, is that it then smoothed out as I went across the last 3 inches of the bowl bottom (10" bowl).

Depending on the inside curve - It may be tighter in this area than on the bottom or near the rim.
What may be happening is the heel of the bevel pushing into the wood as you cut.
I grind the heel off to shorten the bevel.

 

[Dean Center]

Unless you're turning an extremely shallow bowl, you cannot make a continuous cut from rim to bottom center with a 40 degree bevel. The rim gets in the way. If you're going to turn the rim to transition zone with the 40 degree gouge, you'll need to switch to your 60 degree gouge for the rest of the way down.

BTW, if you want a swept back grind, pick your gouge with a parabolic or elliptical shaped flute. (English made tools generally have them)

 

[hockenbery]

Below is a link to an article by Joe Larese that provides an overview of gouges.

The photo shows his explanation of hollowing with different bevels. With long bevels (40 deg) the tool hits the rim in a hemispherical bowl. With the Ellsworth Grind (60 deg) the tool is not close to the rim.
It is the combination of a steeper bevel and shorter bevel that make the hollowing successful.
Grinding the heel off the bevel shortens it more.

a shorter bevel goes around the curve easier and it reduces bevel drag due to less contact area.
On the turn to the bottom the tool is furthest over the tool rest. This requires light bevel riding becasuse the bevel drag will want to pull the tool tip downward.

http://www.mendocinowoodturnersguild.org/wp-content/uploads/GuideToGouges.pdf

 

[Kirk Amidon]

Thanks again for all the help. Definitely seeing improvements every time I turn.

the stalling issue is minimized as I swapped out belts for a shorter one.

This is the bowl I turned yesterday from a backyard maple round. The crab pattern is a bonus. Still have a lot to learn about fine tuning the finish cuts to avoid tool marks but overall happy with this one.

 

[robo hippy]

That crab pattern is really great. Nice piece of Ambrosia Maple.

robo hippy

 

[Ashley Bell]

That looks stunning buddy!!!

 

[Aaron Harris]

Wow, this thread is like gold for bowl-turning tips for a rank newbie like me. I've only turned a few so far (a couple of which I blew up), mostly in English/Claro Walnut and Maple. I just green-turned a super-hard and dense Red-Tip blank with lots of figure that my arborist son brought home. Like Kirk, I was getting a lot of tool chatter even after I thought I had it balanced. The farther up the outside wall I got, the worse it got. It didn't help that it had a huge, uneven bark edge that I thought I was going to leave on, but gave up and cut it off because I couldn't get it balanced. Anyway, I put it away in a paper bag with sawdust at about 19% mc; hopefully, I will have conquered some of my technique issues before I try to finish it.

And that was with super-sharp tools fresh off a 180 CBN wheel, plus a few passes on the insides of the flutes with the Alan Lacer diamond 500-grit slipstone that I just got (it really seems to give me smoother cuts). I think my issue might be more beginner technique issues like tool angle and holding technique. Though I've learned to lock the tool down against the rest and move the tool with my body, I may be white-knuckling things a bit as RoboHippy warns against. I definitely plan to try that A-Frame rigid triangle technique on my next bowl!