I find that in finishing a raised spot (is it called a dimple?) appears in the sanding process. I am wondering how to deal with this?
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Raised spot (dimple)
- Thread starter Peter Wells
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Hi Peter, welcome to the forum. Do you mean on the bottom of a bowl? The center is spinning at a slower foot-per-minute rate than farther out so that could be what's happening. If this is the case be sure to do some sanding (with the grain) with the lathe stopped. You may also be sanding a bit more than needed. Really only trying to take out tool marks, or scratches from the lower grit.
Doug
Doug
I do something a bit different than most: I rarely sand the bottom of a bowl or platter except with very fine paper. Instead, I use curved cabinet-type scrapers. I found nothing quicker to take out dimples, bumps, ridges, ripples, and other irregularities. I use these inside and out on almost all face work and some spindle work. Dead flat? Perfect curves? No problem.
I usually scrape with the grain but not always. Follow up with 400 or finer sandpaper, depending mostly on the wood.
JKJ
John, you will be happy to hear that I just tried scrapers for the first time on a bowl. I had some tear out on the top end-grain of a natural edge cedar bowl, plus some CA stain. Scraping definitely helped, with some light sanding to blend. It's a great addition to the arsenal.
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A dimple would be a small depression. A raised spot could be called by various names like bump or pimple or raised spot.
I moved the thread to the Main forum. The "How To's, Tips, and Techniques" sub-forum is for the purpose of posting a tutorial or an instructional video.
As a reminder to everybody, I would like to reiterate that for the purpose of searchability, it is best to create a separate thread for each How To, Tip, Technique, or, video that you would like to share. Otherwise, combining things in a single thread is an almost certain way of assuring that it will never be seen. Make the thread title descriptive. A title like "Bill Boehme's Fantastic Tips" is of no practical use to someone perusing through that sub-forum and it's also not useful information to a search engine.
Here's a spoiler for the new forum: There will be a special media location where we will be able to share videos. From what I have seen so far, the new forum gallery is nicer that the old PhotoPost gallery.
I moved the thread to the Main forum. The "How To's, Tips, and Techniques" sub-forum is for the purpose of posting a tutorial or an instructional video.
As a reminder to everybody, I would like to reiterate that for the purpose of searchability, it is best to create a separate thread for each How To, Tip, Technique, or, video that you would like to share. Otherwise, combining things in a single thread is an almost certain way of assuring that it will never be seen. Make the thread title descriptive. A title like "Bill Boehme's Fantastic Tips" is of no practical use to someone perusing through that sub-forum and it's also not useful information to a search engine.
Here's a spoiler for the new forum: There will be a special media location where we will be able to share videos. From what I have seen so far, the new forum gallery is nicer that the old PhotoPost gallery.
Yay! It was tearout on a cedar bowl that got me started with the scrapers years ago. Today I'd hate to be without them, at least on face work.
JKJ
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Sand the inside bottom with the lathe turned OFF and either hand sanding or power sanding. Concentrate on getting a smooth curve across the interior from rim to rim. Can you post a picture of the situation that you are dealing with?
If it is a pimple or bump, as Bill describes, in the bottom of a bowl for instance, one suggestion made here that has helped me is to use a round-nose scraper and come up from beneath it, gently, and it pretty much comes right off. Still, I think following up with a hand-scraper as John describes might get the last vestiges off. That little zero-mph area seems to be a toughie sometimes. Does seem odd you get them from sanding, though.
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If you are talking about the center of a bowl.
I sand the center areas with the lathe not running using the edge of the disc moving with the grain direction.
If it needs a bit extra I flip the bowl 180 degrees and sand again.
When turning it is better to have a proud spot in the center than a hole.
The proud spot can be sanded off quickly a hole require sanding the whole bowl the depth of the hole.
What I try to do at the center is take several light cuts with the gouge and catch the last little round shaving in the gouge flute.
The last little shaving is like a miniature coolie hat.
In the last finish cuts, I watch it form and cut it free slowly. I can see the rim lift off the wood and the cutting edge of the tool work toward the pointy peak so that it will drop into the flute when cut free.
Even if I don't catch the shaving I will have made a clean cut to the center of the bowl.
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Peter,
If you are talking about the bottom as we think you are then when sanding always sand across the bottom. If sanding in forward then start your power sander, hand sanding or etc. in the 1:00 to 2:00 position and sand across the bottom and keep going up the side. Never start at the bottom or finish right on the bottom or hesitate on the bottom. If sanding in reverse start in the 10:00 to 11:00 position.
If you are talking about the bottom as we think you are then when sanding always sand across the bottom. If sanding in forward then start your power sander, hand sanding or etc. in the 1:00 to 2:00 position and sand across the bottom and keep going up the side. Never start at the bottom or finish right on the bottom or hesitate on the bottom. If sanding in reverse start in the 10:00 to 11:00 position.
John, do you use the scrapers with the lathe running?
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I'm sure that he doesn't! Don't even think about trying to do that.
Hal, Yes, often. Most of my scraping is with the lathe off, especially in the inside or outside bottom of a bowl or platter near the center. But for the inside walls of a bowl or outside of nearly anything the scrapers work well with the work rotating slowly.
I With the lathe turning I almost always use the small scrapers, most often the oval-shaped ones, and always held by hand away from the tool rest. Sometimes I turn the lathe in reverse and hold it on the outside of a bowl or vessel at the top. Like sanding, reversing the direction sometimes helps give a better surface. For problem areas like irregular grain or tearout I often stop the lathe to clean up then perhaps continue with it spinning. I don't have one procedure but do whatever works for that situation.
Since I improved somewhat on my tool technique the scrapers take the place of power sanding. I haven't used my angle drill with sanding disks for years now. If I want to power sand I went to a Grex random orbital sander as recommended by Rudy Lopez at the TAW symposium - tiny, light weight, can run very slow with good control using fine grits.
The cabinet scrapers on rotating work is perfectly safe UNLESS you do as one guy reported on a turning forum years ago: he put his hand inside a closed form and held a fairly large scraper against the inside. It got away from him, jammed up inside, and turned his lathe into a food processor. Don't do that. I can't imagine a way to get hurt with the small scrapers, kind of like holding a piece of sandpaper against the rotating work except no scratches.
If you drop a small scraper inside it goes to the wall and stays there harmlessly.
I don't think using these scrapers are for everyone but they work for me, eliminate clouds of dust, and seem to be faster than sanding. For me they make it easier to get a flawless surface, especially near the center and on the surface of square platters, 3-corner bowls, and other things where it is difficult to make a perfect final cut. Note that you do have to sharpen them properly and often, since the cutting edge is fragile and the steel is usually not that great. When nice and sharp I often get extremely fine shavings.
JKJ
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I'm sure that I could do it and get away with it. Seems like there was a recent thread about getting away with doing something. I don't know if my luck is good enough to say for certain that I could do it with impunity. Cabinet scrapers can be wickedly sharp and slice through meat a lot easier than through wood. The wood can grab a cabinet scraper and if it slips in your grip, your reaction time isn't fast enough to let go ... and letting go is no assurance that you won't get a nasty cut. I have a Kevlar carver's glove that I use with carving chisels. Not sure that I would recommend using a glove around rotating machinery either. The speed on Oneway and Robust lathes can be dialed down to a really slow speed. Most lathes can't be dialed down to run that slow.
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If you are not skilled with a cabinet scraper don't use it on rotation wood. Too much down side.
A cabinet scraper can produce wicked lacerations and severely damage hands.
you need to learn how to use it properly or you can cut yourself on stationary wood or damage the surface you want to improve.
In general few woodturner use cabinet scrapers because techniques like shear scraping produce equivalent results with a much shorter learning curve.
Also maintaining the cabinet scraper's burr is no walk in the park.
I think it is one of those areas where a person skilled at using a cabinet scraper can use it safely on slowly rotation wood.
A person not skilled with the cabinet scraper is likely to get seriously injured.
Al
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Obviously, there is more than one way to eliminate the dimple, and get a perfectly flat interior of a bowl. I usually don't even try to eliminate the little dimple with tools......and leave a little bit on purpose. Using the Merit power lock sanding method, I've learned a technique to do this. Basically, it's keeping the backing pad almost perfectly flat, while sanding from the outside towards the center with a gradually reduced pressure.....until there is no pressure at all when you reach the very center. You have to watch your "wake" as you get close to the center, and gradually reduce the pressure. My normal lathe spindle speed for sanding is around 300 rpm. It's best to use the regular stiff discs for this, and not the flex-edge. It is an acquired technique, and you have to practice a little to "get it". 
I am talking about high spots on both the bottom and inside the bowl or platter. I am thinking I might be sanding at too high a speed
Just to clarify that which was unspoken, when we say "bottom of the bowl" we're referencing the inside. At least that's the way I'm reading it. It's the most common place to have a persistent bump.
The dreaded dead center spot in the bottom of the bowl.... When getting down to that last little bit, I do tend to leave a raised bump in the dead center. Mostly because it is spinning so slow, the wood tends to tear or break out rather than cut, which is mostly because we are pushing too hard (oh, just had a flash back to old song by the Seeds..... May have to use it some time...). Any way, back to the story. Most bowl turners will take out the dead center when roughing with a plunge cut, either with a scraper or a gouge in a scraping cut. It is easier to go down through the fiber rather than across it where you end up head butting the end grain twice for each rotation. To remove that last little bit, first is one of my bottom tools, like the fluteless gouge from Doug for the really high shear angles possible. Next, I generally use a shear scrape where I can start, very slowly, a pull cut dead center. Next choice is a negative rake scraper. Last choice is to sand it out. I always have the angle drill at slow speed, and a firm pad on the drill. Soft ones just don't cut it. I don't like to use scrapers flat on the tool rest for a finish cut. It always leaves a line where I stop, and if I get up into the transition, then it tears. I never go any where near the rim with a final thickness pass as in "my bowl made this funny screeching and howling sound and then it blew up". Just too much risk. I am liking negative rake scrapers a lot more now days... It is still a scraping cut, but for reasons I don't understand, it doesn't act or cut like a scraper. It still leaves a tiny bit of tear out, but most will come out with 220 or 180.
robo hippy
robo hippy
The way I use these small curved scrapers is perfectly safe. The scraper slipping in the grip is not an issue. In 15 years, not one slip, not one slice or even scratch. I think luck and reaction time or getting away with something has nothing to do with it. Technique is important.
There was a contentious thread about this very subject in another forum some years ago. Some people said handheld scrapers on turning wood worked great and others warned of dire consequences. I remember a similar thread on using a glove while turning. Another thread on advising high speeds for spindle turning. And there was a particularly contentious thread about using the left hand to steady the work while turning. If I remember correctly, some of those with the gravest warnings had no personal experience but based their comments mostly on their imagination or something they read on the internet. Hmm...
Like anything else, if one is has doubts or is not comfortable with any tool, the best advice is either learn to use it properly or don't use it at all.
An open invitation is extended to anyone to come spend an hour in JKJ's "Using Little Scrapers on Spinning and Stationary Wood" class and dispel any mystery. Tuition is free and refreshments will be provided. Using scrapers like this is as safe as using sandpaper by hand on spinning work. In fact, I think it is even less a threat to the turner's body since the fine dust in the air is minimized.
JKJ
So John, you have a transporter handy??? Worst thing about being on the west coast is the difficulty of getting to play dates with my eastern friends... Oh, just about every thing is east of here...
robo hippy
robo hippy
Hiya John.......Yes, this is the same for just about any online forum on any subject. "Experienced" commentary is always more productive than that which is based on opinion alone. Sometimes it's hard to tell just how much validity any given piece of information is, but seeing the results that person gets says a lot.......There are those who avoid showing you what kind of results they are getting. One example, once or twice a year isn't a good basis for making that judgement.
BTW: Your work is exceptional. I hope you become a frequent poster to this forum. Once the member galleries are established, you should consider having your own. If not, a link to your current work will help with establishing your credibility.
The art of creating finely cut shavings is that which eliminates the necessity for excessive sanding. These days, it's common for me to start sanding at 300gt, or higher......but, not always. Depends on the individual piece of wood I'm working on at the moment, and the species. You are correct about the threat to our lungs that sanding poses......and, anything that accomplishes a need for less sanding is a good thing. I've never used cabinet scrapers on the interior bottom of bowls.....in fact, I don't even own any cabinet scrapers! I'd like to try it, and I have some extra wide 2" scrapers that I don't use, never did......can I use that steel to make my own scrapers? How are you sharpening your cabinet scrapers? Are you raising a burr on them?
ko
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John I have several scrapers for flat work and one is about 3 inch diameter with protrusions for coves. Where do you get these "Little" scrapers?
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John,
I think the issue of safety is related to skill with the scrappers. I saw clay Foster use them over 20 years ago on hollow forms.
I used them for a while on slowly moving wood and felt safe doing it. The issue is advocating scrapers to everyone who can read the forum and not being there to show them how to do it safely. I would only advise those who are already skilled with scraper to try them in moving wood.
I have just worked with way too many student who missed a key point and engaged in very poor turning practices due to their misinterpretation.
The glove is a simple issue. If I touch my bare hand to the edge of a jaw on a spinning Chuck I might get a scratch or a bruise. If the edge of the jaw catches a glove it is not letting go until the glove tears which is likely well after some of the hand, wrist, forearm connected to the elbow..... Have been damaged.
People used to turn with ties on. Not many of them strangled.
It's a trade off. Touching moving wood or metal accidentally may be low risk. A risk worth taking to have perceived comfort.
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I feel a sense of responsibility of not making a blanket statement that something is perfectly safe if it requires reaching a certain skill level in order to be done safely. I had a hand injury about twelve years ago when a piece of sanding screen caught and twisted my hand in a full circle before it tore loose from my hand. My third finger of my right hand was dislocated and pointing backwards. Hand injuries are the slowest to heal of all muscle and joint injuries and the recovery frequently leaves permanent residual effects.
As I mentioned, I could probably safely use a hand scraper on the lathe. I have a pretty good assortment of scrapers that I use in flat woodworking. A scraper with a proper bur using a burnishing tool has a razor sharp edge and I have managed over the years to get a few minor cuts from just the normal use on flat boards. I would be interested in learning your bullet-proof way to use the scraper on the lathe. I can't make it to your shop, but you are welcome to come to mine and I'll even feed you and give you a load of mesquite. I will even round up a bunch of other turners in my club.
There is nothing about woodturning that is "perfectly safe".....common sense applies. I suppose Bill's comments are legitimate, but his imagination about what John is talking about may not be......until that time it's understood how JKJ is applying his words. This is another common thing that's almost universal about internet forums.......If the words can be interpreted differently than the person using them meant.....they will be! 
(Can we make that a new twist on "Murphy's Law"?)
Here's another couple questions for JKJ:
My inexperience with cabinet scrapers leads me to the thought that you're using a very slight arc profile with your cabinet scrapers to do the very center of the interior bowl surface. As I mentioned, I have these very wide lathe scrapers that I've never used......and, I'm wondering if I put a very slight arc at the leading edge, I might be able to do the same thing you're doing with hand held cabinet scrapers......? There might be a safety advantage to doing it this way, because this would maintain the original lathe tool handle......? Is there more control over the results by not using a tool rest, or would hand-held produce better results......?
ko
(Can we make that a new twist on "Murphy's Law"?)
Here's another couple questions for JKJ:
My inexperience with cabinet scrapers leads me to the thought that you're using a very slight arc profile with your cabinet scrapers to do the very center of the interior bowl surface. As I mentioned, I have these very wide lathe scrapers that I've never used......and, I'm wondering if I put a very slight arc at the leading edge, I might be able to do the same thing you're doing with hand held cabinet scrapers......? There might be a safety advantage to doing it this way, because this would maintain the original lathe tool handle......? Is there more control over the results by not using a tool rest, or would hand-held produce better results......?
ko
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How much of an arc is the question since some center bottoms might be almost flat while another thing might have a significant curve. One of my square end scrapers actually is very slightly bowed on the nose and it works well if the center of the turning doesn't catch the corners of the scraper ... Well, even that isn't too bad if you use a very light touch.
I prefer the earlier suggestion of scraping across the center with the lathe turned off. That is basically what I do when sanding the inside bottom. When the lathe running I find it difficult to clean up the center... it seems like sometimes it just creates more ripples especially if it is a platter with an almost flat bottom.
Murphy's Law Corollary #137: When reading anything that can only be interpreted one way, the reader will invent a new way to interpret it.
I prefer the earlier suggestion of scraping across the center with the lathe turned off. That is basically what I do when sanding the inside bottom. When the lathe running I find it difficult to clean up the center... it seems like sometimes it just creates more ripples especially if it is a platter with an almost flat bottom.
Murphy's Law Corollary #137: When reading anything that can only be interpreted one way, the reader will invent a new way to interpret it.
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One of the most important parts of safe techniques is paying close attention to what you are doing. When I get deeply immersed in what I'm doing I do things that I wouldn't necessarily advise others to do. When you reach the necessary skill level then I think that you intuitively know how far you can nudge the bounds of your personal skills envelope and get away with it ... but there is a fine line between that and ignoring that little voice in your head telling you to think things over.
John, well, all this talk about card scrapers got me thinking, and I touched up my curved and straight card scrapers on the CBN wheels.... Better than the file, and the burr is really nice. Used the 600 grit wheel on the straight one, but that one was packed away for shipping to Atlanta, so I used the 180 grit wheel on the curved one. Good burr again.... Well more experimenting to do... Oh, set the platform to 90 degrees...
robo hippy
robo hippy
Gerald,
The very first one I used was simply the tip of one of those curved scrapers that sometimes come in the set of three cabinet scrapers. I cut it off with a metal cutoff disk on a Dremel, ground the cut edge flat, and rounded the corners. It was great since it had some curves and a flat section. (Unfortunately I must have dropped it one day in my tub of shavings and threw it out. Fortunately, I can easily make another one.)
Then I found a set of small scrapers at Highland Hardware in Atlanta (now Highland Woodworking)
A few years ago I found a set at Woodcraft, Lynx Mini Scraper set:
http://www.woodcraft.com/Product/15...Set-4pc.aspx?gclid=CO-9rIyj_swCFZI9gQodkhYDBQ
These two sets of little scrapers are good but they are very thin. This makes them more flexible which I'm not convinced is necessary. They don't hold the edge for as long. However, I still use them a lot.
I also have cut up high quality (i.e. expensive) cabinet scrapers and shaped a profile on the grinder. I like these better than the mini sets since the steel is thicker and seems to be better quality, holds an edge longer.
I sharpen them much like I sharpen full-sized cabinet scrapers. It only takes a few seconds with a carbide rod to refresh the cutting edge. I'll turn down a new edge several times before I go back to the grinder or file the edge flat. I have been grinding the edge with a 600 grit CBN wheel.
JKJ
And here I thought we weren't to put a non-HSS tool to a CBN wheel. Are the scrapers OK because it only takes 1.5 seconds to sharpen one?
Just to be clear, I don't use a hand scraper on the center of a bowl or platter while the lathe is spinning. To me, that would be hard to control. I do the best I can with the bowl gouge then turn the lathe off and if necessary use a slightly curved (or flat scraper with rounded corners on flat platters) to remove any little bump or ripples from my poor technique. I HATE circular ripples in the center of a piece!!
Scraping with the grain always gives me a very good surface very quickly and requires almost no sanding. I'm sure I posted this before but it might show the kind of surface I get with these scrapers. This little lidded bowl is made with end grain on the bottom which is sometimes difficult sand. With a hand scraper on the bottom (with lathe off) I took out imperfections and got a perfect curved surface that still looked good with a glossy finish! (with only fine sandpaper) BTW, this one went with me to Italy a few weeks ago to give to a friend.
The inside walls and part of the outside of this small bowl I smoothed with the hand scrapers where needed, with the work turning slowly. The tight coves were more of a challenge since even my little scrapers were too big. In this case, I used a gouge turned upside down as a shear scraper (on the tool rest).
I don't know about a very wide handled scraper. I suspect it would be OK if ground with a negative rake but otherwise the bigger the scraper the bigger the catch! I have in fact tried conventional handled scrapers in the air (unsupported by the tool rest) with the lathe running. I held these at a very sharp angle to the work (impossible to catch since the tool just gets pushed away) but for me the little hand-held scrapers were easier to control and did a better job.
I say "little" scrapers, but for larger curved bowls, platters, and especially for the wings of a squarish platter/bowl where "cutting air" almost always leaves ripples, I like the full sized scrapers with a gentle radius. For pieces like this, I sometimes leave the work in the chuck but remove the chuck from the lathe and hold it while sitting down. For me, this is easier use the larger scrapers AND easier to see when the surface is perfect than when bending over the lathe and looking at it sideways!
I've posted this before but this is the kind of squarish bowl/platter I'm referring to. (I rarely do two of anything but I liked this design so much I've made seven so far!)
One little story: John Lucas stopped in one day and I showed him one of these I was so disgusted with I was ready to throw it in the scrap barrel. I was planning to give it as a wedding present in just a couple of days. After it was finished and buffed I could see in the overhead light that I had left ripples in near the center. Ack! John said no one would probably notice but I'm sure he was just being kind! I suddenly realized that the scrapers might save the day so I cut through the finish and fixed the surface then refinished. (It is one made from cherry on the right in the picture above, turned over to show the shape of the foot - it did make it to the church on time!)
JKJ
Thank you for the kind words! I love turning but although retired, I don't get much time at the lathe this time of the year - with about 50 animals here at the farm time is limited! I spent three days shearing llamas this week:
I do have some pictures of turnings on a facebook album if you are interested, although not frequently updated, mostly small things:
https://www.facebook.com/media/set/?set=a.101238256567388.2825.100000436434935&type=1&l=7913a23da6
But I can always find time for doing demos and teaching, especially kids! And we are in the process of training teachers who will teach kids at a children's ranch/home. Fortunately I have five lathes and room to set them all up in my shop for classes (although it's a bit of a squeeze).
You can easily cut or regrind existing cabinet scrapers to a different profile. I sharpen just like sharpening a conventional cabinet scraper. (Lots of instruction on the net, youtube and otherwise.) I grind if needed with a 600 grit CBN wheel in my Tormek, although I used to use an aluminum oxide grinding wheel. Then put the scraper in a small vise and use a fine file or diamond hone to put a smooth 90-deg flat on the edge. Then form the cutting edge(s).
I don't rely on a burr from grinding, but roll a burnished edge with a round carbide rod just like sharpening a standard cabinet scraper. (BTW, I do this with my handled lathe scrapers too - the edge formed like this lasts longer than a burr from grinding, at least for me.) Before I got a good carbide burnisher I used the side of a round HSS gouge. I usually refresh the edge several times before I go back to the grinder or file.
JKJ
That issue is never-ending with internet forums. Nearly anything written in a forum (from turning to tablesaws, carving, sawmills, chainsaws, welding, horses, electrical wiring, tractors, firearms, climbing, skiing, boating...) cannot possibly be taught completely in a message and may be misinterpreted or misapplied by some reader. I see no practical way for everyone who posts to protect every potential reader from every possible way to get hurt.
Put safety warnings on just the "most" hazardous concepts? Who can define the threshold?
I have never had the pleasure of hanging out with Clay but I'm scheduled to this summer. Perhaps we can compare notes on scrapers!
JKJ
Interesting discussion you have raised Peter!
I gave the scraper a try yesterday. It worked pretty darned well. I found if I skewed the curved scraper on the inside edge it left a very nice finish. Still did some sanding though. Cherry plate drying - two shots of lacquer. (This is the extent of my photo studio...)
Incidentally, I found the best way to make a small plate is to start with a very dry bowl blank you turned too thin the first time.
I gave the scraper a try yesterday. It worked pretty darned well. I found if I skewed the curved scraper on the inside edge it left a very nice finish. Still did some sanding though. Cherry plate drying - two shots of lacquer. (This is the extent of my photo studio...)
Incidentally, I found the best way to make a small plate is to start with a very dry bowl blank you turned too thin the first time.
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Ok, that's funny!
The plate looks great. Almost ready for a fresh batch of cookies.
JKJ
Jamie,
'Hardened' steel is fine on CBN wheels, which means that bench chisels, card scrapers, and hand saw blades are generally fine. I have made a scraper or three out of an old hand saw. The garden shovel or a lawn mower blade are not. The metal under the tantung on a Big Ugly tool is a bit soft. I have found that the Trend lapping fluid works better at getting build up off your wheels than a heavy duty scraper.
robo hippy
'Hardened' steel is fine on CBN wheels, which means that bench chisels, card scrapers, and hand saw blades are generally fine. I have made a scraper or three out of an old hand saw. The garden shovel or a lawn mower blade are not. The metal under the tantung on a Big Ugly tool is a bit soft. I have found that the Trend lapping fluid works better at getting build up off your wheels than a heavy duty scraper.
robo hippy
OK, I misinterpreted what you were saying, John.......I thought you were using the cabinet scraper while the lathe was running....my bad! I wanted to know how you were doing that.
ko
hand scraping, bowl centers and thin shafts
I'm sure I wasn't clear. To (try to!) avoid misunderstanding, I do use the cabinet scrapers when the lathe is running, but only on the outsides, rims, and inside walls and curves of platters, bowls, and boxes and wings. However, to remove dimples, bumps, and ridges at or near the center I always scrape with the lathe turned off.
I don't know of any perfect way to turn the exact center where the rotation goes to zero then reverses! A handled scraper moved vertically pivoted on the rest can get most of it but for me, it's never perfect. Even power sanding in the center with the lathe running is a problem sometimes trying to keep the bottom curve or flat perfect. Power sanding (or better, random orbital sanding) with the lathe off can fix the problem at the expense of introducing sanding scratches or causing undulations in wood with hard and soft areas. The hand scrapers always do the best job for me, regardless of the shape of the bottom.
This has been a long but interesting thread!
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Oh, last night I remembered one other place I use small hand scrapers with the lathe running. I'm preparing for an upcoming demo on turning long, thin spindles (like magic wands, conductor's batons, etc.) and was reminded of this. On a fairly thin shaft (perhaps 3/16" tapering to 1/8" over 12" or so) sometimes vibration is a problem, made worse by flexibility of soft wood or the irregular grain of harder woods. (Sometimes the shaft is so flexible I can deflect it 1/8" with the slightest touch.) If my usual cut with a sharp skew doesn't "cut it", I try one of several tricks with the skew. If I still can't get a clean cut I give up on the skew and grab a small scraper!
I use a small flat scraper edge (usually a rectangular scraper about 1"x1.5") and hold it at a small angle to the shaft (maybe 10-20 degrees from the long axis). Sometime I reverse the lathe. Move the tool rest out of the way (for safety) and run the scraper down the shaft supporting the shaft with the left hand - works every time! Usually I have the lathe speed high.
JKJ
I'm sure I wasn't clear. To (try to!) avoid misunderstanding, I do use the cabinet scrapers when the lathe is running, but only on the outsides, rims, and inside walls and curves of platters, bowls, and boxes and wings. However, to remove dimples, bumps, and ridges at or near the center I always scrape with the lathe turned off.
I don't know of any perfect way to turn the exact center where the rotation goes to zero then reverses! A handled scraper moved vertically pivoted on the rest can get most of it but for me, it's never perfect. Even power sanding in the center with the lathe running is a problem sometimes trying to keep the bottom curve or flat perfect. Power sanding (or better, random orbital sanding) with the lathe off can fix the problem at the expense of introducing sanding scratches or causing undulations in wood with hard and soft areas. The hand scrapers always do the best job for me, regardless of the shape of the bottom.
This has been a long but interesting thread!
--------------
Oh, last night I remembered one other place I use small hand scrapers with the lathe running. I'm preparing for an upcoming demo on turning long, thin spindles (like magic wands, conductor's batons, etc.) and was reminded of this. On a fairly thin shaft (perhaps 3/16" tapering to 1/8" over 12" or so) sometimes vibration is a problem, made worse by flexibility of soft wood or the irregular grain of harder woods. (Sometimes the shaft is so flexible I can deflect it 1/8" with the slightest touch.) If my usual cut with a sharp skew doesn't "cut it", I try one of several tricks with the skew. If I still can't get a clean cut I give up on the skew and grab a small scraper!
I use a small flat scraper edge (usually a rectangular scraper about 1"x1.5") and hold it at a small angle to the shaft (maybe 10-20 degrees from the long axis). Sometime I reverse the lathe. Move the tool rest out of the way (for safety) and run the scraper down the shaft supporting the shaft with the left hand - works every time! Usually I have the lathe speed high.
JKJ
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I was thinking the same thing that Odie thought that you were saying since the original question was about getting rid of the bump in the center. Having a scraper straddle the center with the lathe running seemed pretty risky. I'm convinced that was the cause of my sanding accident that I described earlier.
BTW, I also put a bur on my scraper the same way that you do by using a burnishing rod. My opinion is that a grinding wheel can't put a suitable bur on a scraper. I don't have a CBN grinding wheel so I can't say with absolute certainty, but I know that neither my bench grinder with AlO wheels nor my Tormek can create a satisfactory bur.
BTW, I also put a bur on my scraper the same way that you do by using a burnishing rod. My opinion is that a grinding wheel can't put a suitable bur on a scraper. I don't have a CBN grinding wheel so I can't say with absolute certainty, but I know that neither my bench grinder with AlO wheels nor my Tormek can create a satisfactory bur.