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View coopersdad's profile

Rough finish off the tool

by coopersdad
posted 09-15-2018 07:16 PM


9 replies so far

View TravisH's profile

TravisH

651 posts in 2234 days


#1 posted 09-15-2018 07:52 PM

Based on your description you aren’t getting a true center of axis during the turn. Several things to check and ways to do it.

Check for play in the bearings in the head stock, check run out on spindle, check the chuck (incorrectly threaded or cross threaded onto spindle) are likely what I would investigate first.

Based on the photo looks like technique can be ruled out (tool overhang and support).

View OSU55's profile

OSU55

2155 posts in 2288 days


#2 posted 09-15-2018 08:26 PM

Actually that doesnt look all that bad. Look up shear scraping, Lyle Jamieson has a good video. Can be done with the wings of a bowl gouge ( ground with long wings of course) or my favorite is a thick wide scraper with an angled edge. The idea is to scrape at ~40-45* angle. Makes very wispy shavings. It takes a very good turner to not have some uneveness in the finish off a gouge, especially bowls. Shear scraping is an excellent method to clean up the finish and do final, fine shaping work.

View LeeMills's profile

LeeMills

651 posts in 1600 days


#3 posted 09-15-2018 08:47 PM

These may or may not be part of the problem.
First, what type chuck and are the jaws installed properly. There should be a shoulder at the top for the jaws to seat against. They are open much too wide. They may be the wrong type jaws (bowl vs spigot) for an item extended that far out.
The roughness appears to be from scraping not cutting. The tool can be razor sharp and still used in a scraping position.
The ridges appear to go all the way around. The first culprit may be moving your arms rather than using your body to make the cut (stance). The second culprit may be your feed rate; you will always get ridges but the goal is to have them so small you can’t see them. This is corrected by lathe speed and tool feed rate.

Stuart Batty has an excellent series videos on fundamentals.
In particular he has three on stance and three on chucks, tenons, and recesses. He also has one on feed rate but I am not sure what the called it. They are all about 10-15 minutes.

https://vimeo.com/woodturning/videos/sort:alphabetical/format:thumbnail

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

View coopersdad's profile

coopersdad

32 posts in 1140 days


#4 posted 09-15-2018 10:05 PM

Thanks for the responses! I didn’t mention that I get this issue turning between centers as well as with the chuck. On this turning, the photo does appear to show the round blank is just stuck in the jaws, but there is a 1/2” long tenon, about 1/4” deep turned on the end of the blank and that shoulder is butted onto the chuck.

The bearings seem to be ok -no roughness or rumbling I can see or hear. I have lined up the point of a drive center with the point of a live center, and they line up OK.

I am pretty sure this is an issue I can’t buy my way out of, and it’s technique. Travis mentioned tool overhang and support. My toolrests don’t seem to have as steep of an angle below the top, where the tool rests, as others I see photos of. I think at times when I’m riding the bevel and lower the handle to enter the cut, the tool shank may begin touching that bevel, raising it off the tool rest area, which would be the same as having the tool rest too far away from the work I’d guess. May have to do some grinding on one to test.

I will definitely check those videos. This is one of those new things for me where I don’t even know what I don’t know yet. Thanks!

View Lazyman's profile

Lazyman

3106 posts in 1686 days


#5 posted 09-16-2018 02:22 AM

A picture of how you are holding the tool on the tool rest against the wood (motor off) might help us see what’s going wrong. To me it looks like you are cutting with the edge of the tool like a scrapper and not riding the bevel. I would not be surprised to see a rough finish with the roughing gouge but you should be able to get a better finish with your spindle gouges. I noticed that you didn’t mention using a skew. You’ll get the best finish with the skew and when done right, you often don’t need to use sandpaper at all. The wood will actually have a sheen when properly done. Look for some videos on using the skew and practice with some scrap wood. The skew can be a little scary at first but once you master cutting using the lower third of the edge, you’ll be amazed how nice a finish you can get right off the tool.

Another thing to try is raising the tool rest especially on a spindle turning that large. This makes it easier to ride the bevel of your spindle gouges with the handle in a more horizontal position. Also, once the roughing to round is complete, you should be running at a fairly high speed. In general, you get a better finish at higher speeds.

BTW, you mentioned turning bowls. Most of the cheaper spindle tools should not be used turning bowls. Any of your tools that are shaped from flat steel and so have a flat tang stuck in the handle are dangerous to use on bowls. Never use a roughing gouge for bowls.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View coopersdad's profile

coopersdad

32 posts in 1140 days


#6 posted 09-16-2018 03:47 AM

I’ll try raising the tool rest and see what that does. I can’t go any faster using the chuck, the directions warn against exceeding 1800 rpm, I’m at 1475 and the next pulley is 2200. I’ll try some faster speed with some between centers work.

I’ve worked with the skew a little and did get some OK finishes with some planing cuts on practice pieces. Turning beads or much of anything else was a disaster, so much more practice is in order there as well.

View Lazyman's profile

Lazyman

3106 posts in 1686 days


#7 posted 09-16-2018 02:00 PM

That should be fast enough. With tailstock support, even faster speeds should be fine as long as it is properly mounted in the chuck but you are the best judge of what feels safe for you.

Just remember that the idea of riding the bevel is to have the edge of the tool almost at a tangent to the surface so you are just sheering the surface. When I first started turning a few years ago, the easiest way for me to achieve that was to actually start high where the back of the bevel was riding but the edge is not in contact and then slowly ease the handle up and slightly back until it starts cutting.

While it is very helpful to watch the videos, Doc Green’s written information was actually the first thing I used. Sometimes in the videos they assume that if you can see what they are doing, you understand what is going on but with just written explanations with a few pictures, I actually got a better understanding of why it works (or doesn’t). You can find Doc Green’s how-tos here. After reading his explanations, what I was seeing in the videos made a lot more sense. Lots of good information on that site.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View LeeMills's profile

LeeMills

651 posts in 1600 days


#8 posted 09-16-2018 02:27 PM

In the pic I see the tenon but the top of the jaws are not contacting the wood at the outer edge of the jaws. It is the outside edge contact which gives the most support to keep the item from rocking (much like a faceplate support is at the outer edge).
The Batty videos give basics not covered by most folks, at least not in detail.
I think it is mainly techniques.
You said “I think at times when I’m riding the bevel and lower the handle to enter the cut,...” you should be raising the handle to make the cut. I agree with Lazyman that you probably need to raise the tool rest.
Here is a video by Steve Havens on the spindle gouge. The camera angle gives a good view of the tool rest height and where the cut is being made. Note that when they show making the cut he uses proper “stance” even though he hardly mentions it.
https://www.youtube.com/watch?v=vztW0uzJDlI

Steve has good videos on most every tool and presents it clearly with the angle imposed in most of them.

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

View OSU55's profile

OSU55

2155 posts in 2288 days


#9 posted 09-17-2018 02:30 PM

I missed “lowering the handle to enter the cut”. Yea, it doesnt work that way. As others said, put the bevel in contact with the wood, above CL, then slowly raise the handle until the bevel starts to cut. Keep the tool on the toolrest. The flute should be turned to ~45*. You may well have just been scraping – thats the only cutting that will occur when lowering the handle to put the tip to the work. Use low rpm until you get a feel for it.

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