Tool for sanding inside hollow-forms

[Robert Marshall]

I would like to buy or fabricate a tool which would allow me to sand the inside of hollow-form vases, particularly the inside walls. My purpose would be to eliminate the "shaggy" condition of the inside walls, which sometimes happens when hollowing green wood pieces.

My imagination visualizes something mounted to a drill extension, the head of which is small enough to fit through the openings of a vase (with strip-sandpaper flaps wrapped around the head). The vase openings typically would be in the 1 to 2 inch diameter range. Once inside and spinning, 2 to 3 inch strip-sandpaper flaps would extend out due to centrifugal force, and would rub against the inside walls of the vase as the drill spins. The design needs to provide for regular replacement of the flaps, with some means to secure them when replaced.

I have seen "flap sanders" offered on the market, but these tend to be densely-packed circles which don't have the capacity to expand out. Most of them are too big for a vase with a small opening. They seem to be meant for working on outside surfaces of a curved or irregular form, not for inside a vase.

Any ideas for purchasing or fabricating such a thing would be appreciated. Thanks!

Robert Marshall

[Richard Coers]

A tear drop scraper cutter or carbide insert negative rake scraper will reduce sanding dramatically. But trying to get a sanding head in through a 1" hole seems impossible to me.

[Peter Blair]

I made just such a tool. But there is a commercial maker I can't remember who, that also makes them. I use soft foam with velcro glued to them. I have a few sizes but they, depending on the opening size, will not get up under the collar at the top. I also occasionally put in a bunch of auto glass chips and marbles, seal the top and spin quite slowly for a few days, sort of like a reverse rock polisher. Works great. I had to make up a gizmo to rotate the pieces quite slowly so the glass and marbles would actually tumble. I could send photos of both if you like.

[Kevin Jenness]

I use a negative rake teardrop scraper after the initial hollowing followed by sandpaper held in forceps. If the opening is large enough I use an inertia sander or a drill and extension drive with a hook&loop sanding pad. With small openings I don't fuss much with cleanup farther than a finger can reach. As with any turning the cleaner the initial cuts the less subsequent work is needed.

[John K Jordan]

I don't much sand something I can't feel or see. However, I use a small teardrop type scraper on the insides. With that there is very little sanding required. When needed what I use depends. For small holes where I want to peer at a smooth bottom through the hole, I sometimes tape a folded piece of sandpaper to the end of a dowel rod and sand with the lathe both on and off.

For larger holes, I find a 1" sanding disk on a shaft extension on a pneumatic ROS Grex sander just about perfect for the bottom. I use a VERY low speed on the sander.

I didn't take a picture of a 1" disk in use or the shaft extension but here is the Grex.

grex_ROS.jpg

JKJ

[Neil Strong]

As others have said, use negative rake scraper tips to get the surface as near to finished as you can before sanding. The best tool I have found for inside forms is the Woodcut Pro-Forme Scraper Head (not the Irons). It is the only one that I know of that allows for shear scraping on any of internal surfaces, including up under the shoulder. You don't have to get the bent Pro-Forme bars from Woodcut if you can make up your own bent bars.

For me the most important area inside a closed form is the area that can be reached with the fingers. I use an old leather glove with velcro attached to longest middle finger and small abrasive disks to finish that surface area that can be felt but not seen.

For closed forms with very small openings I put a saw cut (or two) in the end of a dowel rod and insert strips of abrasive into the cuts and clamp in place with a slip ring on the tapered end of the dowel. Secure strips at mid point to keep in balance, but only one side of the strip will sand in either direction. So, reverse drill direction with the lathe running slowly to make use of the abrasive on the other end of the strip.

This won't do the very inside bottom. For that I use small disks on long extension rods.

[Peter Blair]

Further to my earlier note, here is a link to a video that shows the Vermec Sander. https://www.youtube.com/watch?v=R8t67TDffx0. He is using a large one but I made up two that are much smaller. I just use it on a simple bar with a handle. I made mine so I can interchange different sizes. Typically I use it for vase shapes not so much for hollow forms.IMG_2574.jpg

[Kevin Jenness]

One point to note is that when turning green wood any scraping or sanding that depends on spinning the vessel for power pretty much has to be done in stages - hollow, scrape and sand in an inch or two, and repeat until done. Hollowing out the entire form and trying to go back and sand nearer the opening is almost bound to fail as the piece dries and distorts dynamically. If you can get in with a power tool after hollowing with a split mandrel as Neil describes or a disc on an extension shaft to sand the bottom it's a different story, but generally it's best to clean up as you go and move right along so you can smooth out the areas that need it before the piece starts moving or checking.

[Brice Rogers]

I watched a demo by Mike Jakofsky, a San Diego professional hollow form turner. He gave a good tip that I still use today.

Get a really study locking hemostat (ebay or the Harbor Fright 10-1/2 or 12" - - they call them locking clamp pliers). Take some sand paper and wrap it around a small piece of foam mat and lock the hemostat on it. the semi-rigid foam will make the sanding piece a little stiffer than bare sand paper and will even out the pressure. As you sand, if you have the wrap correct, it'll bend over a bit. Then, sand away.

I rough sand most of the interior and then shift to finer paper but only for the areas that I can reach with my finger or fingers or can see with my eyes. In the past I haven't bothered to go much finer than 150 grit.

[John K Jordan]

That’s a good tip. Where the opening was too small for my 1” ROS disks with long extension I did something similar to what you said but by taping sandpaper and some foam backing to the end of a dowel, sanding mostly by hand. (I also mount a tiny curved scraper on the end of a shaft - by starting with good scraping very little sanding is needed) Rounding the end of the dowel helped too.

Seems like a hemostat would be quicker, especially for fairly shallow forms. For a deeper form, the upper part of the standard hemostats might be a little too wide to fit through the hole. Note there are special hemostats that are double-jointed to allow access into much tighter spaces. I have no idea where to buy them.

I found some in a huge box of medical instruments at a metals recycling place for scrap prices - mostly stainless steel and and titanium. There were scissors and clamps with working ends so tiny they looked like they were for eye surgery as well as a bunch of other clamps, long, tiny, massive, hammers in the shape of rods, long thin scalpels, and far more, many I didn’t understand. Some were gold plated. I bought the whole box. I gave a bunch to some veterinarian friends and kept a bunch for around the shop. What a find! I’ve forever finding new uses.

Edit to add photos: These are not "hollow forms" as often defined but they are lidded boxes, but for anyone interested this is the type of inside surface I like to get:

elm_box_inside_IMG_5352.jpg blackwood_box_IMG_8158.jpg BOC_E_IMG_7171.jpg
pod_box_comp.jpg threaded_ebony_box_IMG_6757.jpg

All these were smoothed with curved scrapers then sanded by hand. Same principle on deeper forms but hard to photograph!

JKJ

I watched a demo by Mike Jakofsky, a San Diego professional hollow form turner. He gave a good tip that I still use today.

Get a really study locking hemostat (ebay or the Harbor Fright 10-1/2 or 12" - - they call them locking clamp pliers). Take some sand paper and wrap it around a small piece of foam mat and lock the hemostat on it. the semi-rigid foam will make the sanding piece a little stiffer than bare sand paper and will even out the pressure. As you sand, if you have the wrap correct, it'll bend over a bit. Then, sand away.

I rough sand most of the interior and then shift to finer paper but only for the areas that I can reach with my finger or fingers or can see with my eyes. In the past I haven't bothered to go much finer than 150 grit.

[Randy Heinemann]

I watched a demo by Mike Jakofsky, a San Diego professional hollow form turner. He gave a good tip that I still use today.

Get a really study locking hemostat (ebay or the Harbor Fright 10-1/2 or 12" - - they call them locking clamp pliers). Take some sand paper and wrap it around a small piece of foam mat and lock the hemostat on it. the semi-rigid foam will make the sanding piece a little stiffer than bare sand paper and will even out the pressure. As you sand, if you have the wrap correct, it'll bend over a bit. Then, sand away.

I rough sand most of the interior and then shift to finer paper but only for the areas that I can reach with my finger or fingers or can see with my eyes. In the past I haven't bothered to go much finer than 150 grit.

What makes the "wrap" correct so that it does what you indicate?

[Brice Rogers]

I used a piece of rubber mat used for standing on (Harbor Fright). I cut a "chunk" of it about 1/2" in diameter and maybe an inch long. Maybe it was a little smaller in dia. like 7/16 or 3/8. Then I fairly tightly wrapped about a turn and a half of sand paper around it. The paper and mat were fairly stiff but when pressure was applied, they bent over. That seemed perfect. So, if you used soft foam or put 3, 4 or 5 turns around it, it wouldn't be optimal. But it is actually pretty forgiving.

IIRC, I typically sand in one direction and then reverse to sand in a reverse direction. Maybe it doesn't matter, except that it'll cut off the fibers that are laying down in one direction.

The Harbor Fright hemostats are pretty beefy and are curved so they can go into a small opening (like 3/4 inch) and reach around the "corner" or opening a bit.