Hollowing small tea cups

[chuck van dyck]

Hi all

Long time lurker, first time poster.

I decided to finally take on a project I've been wanting to tackle ever since I saw some cool little turned tea cups in Japan on my honeymoon last year. It's a pretty simple little thing, but I'm having a hard time cleaning up the inside bottom of the cup.

I'm using a 1" forstner bit on a jacob's chuck to bore out about 2 1/2", then I've found my spindle/detail gouge to be most effective at removing material from the sides. Once I reach the bottom it gets a little hectic. I've found a cut coming from the bottom then almost prying up to be the most consistent angle of approach, but it's A LOT of work. It's less of a cut than a slow scrape.

Unfortunately I have limited tools. I'm working with a spindle roughing gouge, detail gouge, and bowl gouge. It seems a round nose scraper would be nice here but it's just not on my list of owned tools yet...

Things I'm considering:
Regrinding my bowl gouge to a have more swept back wings and a more exposed tip to get in there.
Buying a round nose scraper, although there are no funds for this ATM.

I know with enough persistence I'll get it, but I'd love to make this a cleaner process. Any advice would be greatly appreciated. Thanks for taking a look.

I don't have a photo of the exact area I'm having issues, but I will attach a couple photos of my first attempt. Unfortunately I didn't measure twice before parting....
cup.jpg
cupblowout.jpg

[John K Jordan]

Hi Chuck! I'm sure you will quickly get the hang of things.

I use several methods to smooth the bottom of such a turning. I'm not so sure regrinding the bowl gouge would be that helpful on the bottom, but could be good for shear scraping the side. You might have to be careful not to disrupt the shape of the gouge as to make it harder to use as a bowl gouge. Some people do grind a gouge asymmetrically which could work but I think it would be better to start with a different gouge, even a cheap one.

A round-nose or mostly round nose scraper is a good choice. If the hollow is deep it can be tricky to control - sometimes you can put a tool rest part way into the hollow for support. Several companies make special "box rests" that fit far into the hollow to make this easier, but that's another cost. I use one from Best Wood Tools and another larger one from Robust. If the scraper is ground with a bit more side grind than round that edge can be tilted down a little while sweeping and smoothing the curve.
If the bottom is mostly flat I often use a box scraper with a flat tip, again, supported on a box rest.

I grind some scrapers with a negative rake, rounded on one side and a bit straight across (or almost straight across) on the ends. These are excellent for smoothing bottoms, transitions, and sides, but the curve has to be small enough to fit in the curve of the piece.

Depending on the depth and shape, I often use one of several Hunter tools to clean up the bottom and sweep from the bottom all the way up to the rim (probably my favorite way to shape and smooth the inside of something) but that's another tool or two to buy and they are not inexpensive.

One of my favorite tools for the inside of something like a goblet or cup is the small Sorby teardrop scraper. I mount one on either a long or short Sorby multitool handle, turn it until the profile will fit the piece, rotate a little counter clockwise, then sweep across the bottom and up the side. However, this is another cost. Could possibly make one if handy with working metal. I made another one from a small oval-shaped hand scraper and mounted it on one of the same Sorby handles. I sometimes use the teardrop scraper with the lathe turned off. This is the scraper bit: https://www.robert-sorby.co.uk/rs222...gh-speed-steel

You might look around, perhaps ask turning club members, and find some old tools that you can regrind into scrapers. An old skew is perfect to make a scraper.
I accumulate free and cheap tools like this and keep a box of them just for grinding into special tools or giving to students. You don't indicate where you live but if you happen to live in my little part of the country I'd be glad to give you one.

BTW, if the hollow on the piece is not too deep I also do a lot of smoothing by hand off the lathe. I keep a variety of curved and flat scrapers and can often find one perfect for the insides, some with handles and some held in the hand.

You might not be able to see the photos unless you upgrade to Contributor status on this forum (only costs $6 per year! - see the Donate button above) but if you do, here are a few I've smoothed mostly by hand after shaping and getting the insides relatively smooth with other tools:

blackwood_box_IMG_8158.jpg cocobolo_boxes.jpg knob_IMG_7164.jpg threaded_ebony_box_IMG_6757.jpg

Even these tiny pieces are hollowed and smoothed with scrapers - for the smallest I grind a round-nosed scraper from a round steel rod - grind the end round as needed then grind a flat on the top to give me a good cutting edge.

tiny_thngs_IMG_7970.jpg

JKJ

[Mike Nathal]

I also think scrapers are the way to go. A brand new scraper can be found for under $40. Another option would be an Oland tool, which is also a type of scraper with a replaceable tip. You can buy them for about $50 as they are also known as straight boring bars. I made my own for about $15. I use mine all the time.

[John K Jordan]

I also think scrapers are the way to go. A brand new scraper can be found for under $40. Another option would be an Oland tool, which is also a type of scraper with a replaceable tip. You can buy them for about $50 as they are also known as straight boring bars. I made my own for about $15. I use mine all the time.

The Sorby teardrop tip works very much like the Oland except rotating the shape givesflexibility to fit more variety of inside shape. Also, a small handle makes them more maneuverable for smaller work.

BTW, there is interest in a complete set of genuine Oland tools let me know and I'll advertise them on the Classifieds forum here. Years ago I bought a set directly from the now late Lissi Oland before she moved back to Denmark. These were made by Knud Oland. The tools are still in the unopened box. I planed on keeping them as a part of history but I think I have too much stuff...

JKJ

[Thomas Wilson80]

I bought a HSS bar off amazon or eBay for around $7 and ground it into a rounded scraper on one side and a negative rake scraper on the other end. I intended to make a handle, but find I don’t need one as I only use it for very light scraping but it works great on shallow boxes.
Tom

[chuck van dyck]

Thanks for the thorough responses!

Oof, there are a lot of scrapers out there. John, I think I'll take your advice and keep an eye out for some old tools. I live in Brooklyn, NY where there aren't a whole lot of turners it seems, but you can find just about anything on our craigslist. Especially if I take a drive Upstate. Looks like you're in TN.. I grew up in Paris, TN. Don't think I'll be able to get a tool off ya unfortunately. I'll also try your tip of smoothing off the lathe.

Thomas, I also like the idea of buying some HSS stock and grinding my own as I do like a long handle, so being able to customize in that way would be nice. Fitting round stock into a handle is easy enough, but for a scraper I assume you'd need flat stock. Would you split the blank, slot for the steel, glue it back up and turn the handle, or is there a better way to fit flat stock in a handle?

Also, can anyone describe the benefits of a negative rake scraper over the standard grind?

[Thomas Wilson80]

Also, can anyone describe the benefits of a negative rake scraper over the standard grind?

i really like Brian Havens videos and he has a great one on neg. rake scrapers that is better than any explanation I could give:

https://www.google.com/url?sa=t&rct=...SRn0VfRoioaA75

[John K Jordan]

...I also like the idea of buying some HSS stock and grinding my own as I do like a long handle, so being able to customize in that way would be nice. Fitting round stock into a handle is easy enough, but for a scraper I assume you'd need flat stock. Would you split the blank, slot for the steel, glue it back up and turn the handle, or is there a better way to fit flat stock in a handle?

Also, can anyone describe the benefits of a negative rake scraper over the standard grind?

I like stock from Doug Thompson (Thompson Tools). He uses a 10V HSS which holds an edge better than some other types of HSS. I grind scrapers from his scraper tools, from skew chisels, and from various bar stock he sells. Most of my scrapers and all my NRS are from Thompson steel.

As for handles, you do need a handle when using a conventional scraper in the rotating piece but I tend to use handles maybe 14" or so. To permanently mount a scraper with a tang into a handle some people simply drill a hole and force the steel into the hole with some epoxy. Some do split and glue. I prefer to make inserts from aluminum or steel that have round holes with the flat of tool held with set screws. This way I can use many tools with few handles.

For negative rake scrapers I never use them with handles. This is perfectly safe since there is no force on the tool and catches are almost impossible. Some of my NRS. The first three are what I use the most on bowls and platters, bevels ground similar to a skew chisel with a 60" included angle. It's not necessary, but I like to make the top and bottom bevel the same so I can burnish a burr on either side to make either a left hand or right hand scraper from the same tool. As you can see, I grind a smaller NRS on the other end of the tool. (usually with a short piece of heavy plastic tubing to protect the edge.)

_scrapers_IMG_7777.jpg NRS_IMG_7907.jpg

Some smaller NRS, the middle one ground from a shallow detail spindle gouge:

scrapers_small_thompson.jpg

Unlike conventional scrapers, negative rake scrapers are held horizontal instead of tilted down (with handle up), and held flat on the rest. The do not remove a lot of material but when sharpened properly they will take off "whisper" shavings and quickly remove tool marks from the gouge.

This one is in use on the "wings" of a piece and on a curved section. I've been told you can't use scrapers when "turning air" but it works fine for me. You can see some of the fine shavings. Again, I'm using this without a handle.

NRS_IMG_7515.jpg NRS_curved.jpg

I think I mentioned earlier that after using the NRS I use hand scrapers with the piece off the lathe which leaves the surface so smooth it requires very little sanding. Almost all of my sanding is by hand with the piece off the lathe. I leave the piece in the chuck and mount it on an adjustable carving and finishing stand from Best Wood Tools:

carving_stand_IMG_7422.jpg carving_stand_B.jpg scraper-shavings-IMG_7864.jpg


JKJ

[Reed Gray]

Especially, if you are turning end grain, the NRS is the tool to go with. They don't work quite as well in side/bowl grain orientation. Dave Ellsworth, in one of his videos about hollow forms showed an exercise for cleaning up the dead center. He had a hollowing bit on, but it involves a sweeping action, sideways and up and down through the dead center. Note, be very careful about swinging through the center to the up side rotation. If you are taking a big cut, your tool can come back to the down side very fast, and violently... This is a very gentle clean up cut.

robo hippy

[Ricc Havens]

Lyle Jamieson will be doing a live remote demo on thin wall goblets. NOTE: it will be about using his style of spindle turning and also his type of hollowing system. If you don't have his system it might not be of benefit. But, for $12.99 it will give you a different perspective on technique should you ever want to go that route. PIt's an interactive so you will be able to ask questions.

https://lylejamieson.com/product/11-...n-wall-goblet/

[chuck van dyck]

Wow, that's better. I can see the photos now Beautiful work!

Lots to absorb here, but I think it's sinkin' in. That video by Brian Havens explains it very well.

Am I right in assuming a NRS grind is basically that of a skew, with a quick secondary bevel on one side to create the burr?

A member here was kind enough to send along a care package with a nice RNS and a couple tools for experiments in grinding. Not to mention a nice variety of wood ("as much as would fit in the box"). So I am vey grateful for that. I will be sure to pay it forward when the opportunity arrises.

Will update with a photo when I get a chance to hop back over to the lathe.

[John K Jordan]

Am I right in assuming a NRS grind is basically that of a skew, with a quick secondary bevel on one side to create the burr?

A negative rake scraper can be ground like a skew with equal bevels, or with one bevel longer than the other. The only requirement is the total included angle be less than 90-degrees. I have made some just slightly less than 90-deg but most with 60 to 70 degree included angles. A narrower included angle such as used with an actual skew chisel will work fine but the edge might not hold up as long.

There is no secondary bevel ground to get the burr. To use the grinder burr simply grind the bottom bevel last. But as mentioned, a grinder burr works great but won't last long. I burnish the burr (after grinding and honing) with carbide burnishers. These are the first two I made with carbide rods I bought, the larger one about 15 years ago - the smaller diameter takes less force for the same burr so I mostly quit using the large diameter one.

carbide_burnisher.jpg burnisher_IMG_6767.jpg

More recently I bought an Arno burnisher to try. https://www.amazon.com/Arno-Carbcut-.../dp/B07J17DMKS
I like it a lot! It has a round rod on one side and a triangle with a smooth edge on the other side - functionally like a very small radius rod with the triangle providing strength. The handle and angles are nice too. Not exactly cheap but I think worth it.

You can also use a round hardened lathe tool (such as a spindle gouge) as a burnisher.

JKJ

[chuck van dyck]

Ah! I see. Thanks for clearing that up. I know how to burnish my card scrapers, but not sure I fully get it on a turning tool yet. I keep my grinder about 3 ft away though so I don't mind a little touch up for now at least.

[John K Jordan]

Ah! I see. Thanks for clearing that up. I know how to burnish my card scrapers, but not sure I fully get it on a turning tool yet. I keep my grinder about 3 ft away though so I don't mind a little touch up for now at least.

For turning tools I don't use the double burnishing method often used for card scrapers.

I first sharpen the tool, remove the grinding burr (with a leather honing wheel on a Tormek or an extra fine diamond hone or a bit of polishing/honing compound rubbed on a piece of wood or MDF). Then hold the tool in the left hand and make a single pass with firm pressure from the burnisher held at a slight angle to the bottom bevel. I feel that bevel with my finger and if deemed necessary, repeat the burnishing with another stroke or two and/or more pressure. I then test the scraper on the work. Experience eventually directs the pressure and the angle.

When the effectiveness of the burr decreases I remove it with the extra fine diamond hone then burnish again. I do this a few times before I take it back to the grinder.

BTW, after trying several types, I've found the blue Eze Lap paddle hone is the best for me. For me it's easiest to control on curved turning tools of all types. I hold the handle in my palm with my forefinger pressing just behind the honing edge.

hones.gif

JKJ