Help with hollow form interior tool marks

[Travis Tatomir]

Hello everyone, i'm in need of some advice as to how to remove the tool marks on the interior of void-filled hollow forms. This is a piece of western red cedar I believe that I was told got cut off the tree 25 years ago and left in the shade. As a result of this, it had a rather large amount of rot present within as well as significant insect damage.

I understand that cut planning and a well controlled finishing cut is always the best way to limit tool marks and sanding and employ that constantly but this wood was just too rotten and still green for a finishing cut at this thickness. I hollow freehand with a large simon hope hollowing tool and touching this with that at this stage will produce tool marks no matter how I try to approach it.

In retrospect, I just didn't really have the appropriate gear to take on a 20" x 8" hollow form with voids and rot when I began this project and only got to this stage through stubbornness. However, i'd still like to complete the piece and get it to the gallery for a show which means these toolmarks have to go. Thankfully the voids offer pretty good access to all of the interior surface, however hand sanding these out is going to be an extremely long and tedious process.

Any tips and tricks?, Ingenious ideas? Perhaps just the hard truth of the 6+hour hand sanding job ahead of me? Haha. I have a rubber ball on a stick with sandpaper glued onto it but it isn't safe to sand this interior with the lathe running, it would risk the piece and perhaps personal injury.

 

[Richard Coers]

Wet cedar is hard to turn without some tear out on any turning. Sanding with the lathe spinning is going to be extremely difficult as whatever holds the abrasive will want to bounce in and out of the voids. I would have used a tear drop scraper blade, with a negative rake bevel on it with my hollowing tool before taking off the lathe. The only option I see now, is to use a 2"pad on an extension bar and sand off the lathe. I have used that arrangement on the drill press so I can hold the vessel with both hands.

 

[John K Jordan]

While turning I use small curved scrapers held in stout tools such as the large gooseneck Sorby tools made for this. Mine came with a teardrop and a round scraper (as well as hollowing bits). I also cut out and grind my own scrapers from cabinet scrapers, more flexible than the Sorby scrapers, sometimes useful. Between the gooseneck and straight shaft versions, i’ve been able to reach almost anywhere I needed. There are also small versions of these tools. I could take some photos when I get time.

Some Sorby tools with teardrop and shop-made scraper tips:

For hand smoothing through the voids I’ve used sandpaper fastened around or fastened over some foam on the end dowel rods. Also, I sometimes use a Grex pneumatic sander with long extensions holding a 1” sanding disk. (running at very slow speed)

I also have a reciprocating pneumatic file that is sometimes useful and can save a lot of time. Might reach through some of the voids. However the files that came with it are not very long.

Those little sanding “sticks” sold at carving shops are nice too. Those I have use very narrow sanding belts stretched around a plastic “stick”, made so the belt can be rotated to expose fresh sandpaper as one section gets worn.

You can sometimes use a strip of flexible sandpaper, perhaps torn from a sanding belt, threaded through hard-to-reach places to sand the inside by alternating pulling on one end then the other.

Is it something you can sand blast? Sand blasting can result in a very interesting surface, accentuating the grain. Works better on some types of wood than others.

JKJ

 

[hockenbery]

I would have use a teardrop scraper to smooth the surface. I do not sand the inside of hollow forms.

One thing that I have done on forms with lots of voids is to bleach the inside. This brightens the inside to emphasize the voids. The bleaching also raises the grain a bit making the surface look smoother. Cedar may be a too light in color to bleach.

I you have experience with torching surfaces. This might be an alternative to sanding also iit would give a contrast in color for the inside. It’s not a first torching project.

If you have card scrapers and can get your hand inside the form you might be able to use them on much of the surface.

If you have a flexible shaft tool like a foredom you may be able to use it inside the form to sand with the 3M bristle discs.

 

[Gerald Lawrence]

i have used Black Gesso inside hollow forms if the surface just does not want to even out. It is so dark that you cannot see contours without a bright light.

 

[Wyatt Holm]

I would use a teardrop scraper like the Sorby hook tool has. Freshly sharpen the scraper do you have a good burr, hold it downhill from your tool rest and take a light cut. Good luck. If you want a good video on the subject, I recommend this one

View: https://youtu.be/TpKnwUO0TYY

 

[Jaramiah Severns]

I use a 1” sanding disc on a rotary tool w/ an extension shaft. If you use a soft pad under the disc, the centrifugal force of the rotary tool will make the disc spin in a conical shape, which allows you to sand at nearly a 90 degree angle. Works like a charm.

Some tight spots may still need a touch of hand sanding, but the 1” disc can get into most places.

 

[DON FRANK]

As open as this is I'd lean to the sandblasting idea JKJ mentioned. Contrasts of smooth and textures always work sculpturally . If the wood would bleach well, sandblasting and bleaching the inside would give one more contrast. It could all be done in the time it would take to adequately sand tear out.

 

[john lucas]

Use the tools John K. Showed with extremely light cuts. My friend who turned a lot of hollow vessels with voids said if you imagine dragging your fingernail across the back of your hand and barely feeling it. That's how light it needs to be.

 

[hockenbery]

I’d caution against sandblasting unless you are sure you won’t change the character of the piece in ways you won’t like.

When I was learning not to blow dust off thin hollow forms, i blew a hole in one with just air pressure.

I suspect you could easily blast holes in the soft spots and certainly blast away the edges of the voids. A different look you may or may not like.

Also getting a consistent looking blast surface will be difficult since getting the blast gun at the same distance and angle will be impossible. You would likely not be able to see what the blasting is doing and Shooting at oblique angles is marginally effective.

 

[Kent Reisdorph]

I use a 1” sanding disc on a rotary tool w/ an extension shaft. If you use a soft pad under the disc, the centrifugal force of the rotary tool will make the disc spin in a conical shape, which allows you to sand at nearly a 90 degree angle. Works like a charm.

Some tight spots may still need a touch of hand sanding, but the 1” disc can get into most places.

I bought a set of 3" 2" and 1" mandrels and pads for my sanding. I looked at the 1" and thought, "Pretty useless." Now I know better!

 

[Jaramiah Severns]

I bought a set of 3" 2" and 1" mandrels and pads for my sanding. I looked at the 1" and thought, "Pretty useless." Now I know better!

When a piece gets thin and starts to flex a bit as it spins, even tear drop scrappers can be risky and still don’t leave a perfectly smooth finish (although I suspect practice and patience would mitigate that over time). I find that using the small sanding pads with the flex extension gives me the most precision and control, while eliminating the chance of a catch. That’s the technique I’ve used on the last few void forms I’ve posted in the gallery.