Hollowing tools

[Peter Blair]

Hi all and the very best of the Holiday Season to you all.

I am attempting to make and a couple of hollowing bars (tools) but am not sure what sort of bends I should incorporate.
I am planning to make two bars, one for 'up under the rim' and a slightly straighter one to follow downs the sides.
The shafts are 3/8" drill rod into which I plan to install 1/8" cutters using small grub screws
I can't seem to find any reference to the angles or curves that I should use.
I suppose it might be important to consider what sort of Hollow Forms I will use them on, but if possible I would like to bend them in a manner that would make them more or less universal. That is to say, smaller hollow forms with small openings.
I have a straight and a curved John Jordan which I use both by hand and with my Kobra but I seem to need a rather large opening to get up under the rim with these.
Can anyone point me in the right direction?

[Harry Robinette]

The main thing is that the tip has to be on center with the tool. If the tip is not on center (straight up the shaft to the tip in one straight line)the tool will want to torque and twist in your hand. I usually just eyeball the bend more bend for under the lip less bend for deeper. Look at a picture of some in the books or on line.

[Dennis Ford]

I don't think "universal" is the right way to think about these. Making small opening HFs is a path that will require multiple curved tools with slightly different shapes. It sounds like your John Jordan tools have too long of a curve to do what you are trying to do, so make one with a shorter curve (and keep the tip on center as Harry posted). Plan on making more versions later.

For the small tools like this I use CA glue to secure round HSS bits in the shank as I tend to be ham handed with the tiny taps when threading small holes for set screws.

[charlie knighton]

3/8 anything will not go very wide, say under 4 inches wide, and not very deep, say under 4 inches deep, 3/8 can go thru small hole, you might add an outrigger to help with the torque

[Richard Coers]

Is that a typo? Did you really mean 3/8? That is way undersized, unless you only want to do hollow Christmas ornaments. If you don't round the 1/8" cutter, you will have to drill a 3/16" hole. That's not going to give you much for threads on the grub screws. I have a set of 1/2" form small work, but really only use 3/4" for vessels. What I have done, was find a picture of production tools. Enlarge them on a copier to full size. Now use the enlarged copy as a template to bend your rod. The best tool I used for bending the rods, was to use a floor drill press. Use the column and something either bolted to or clamped to the table. Heat up the bar and use the rig on the drill press to bend them.

[Faust M. Ruggiero]

Hi Guys, Merry Christmas. It's 6:30am and a balmy 16 degrees here in eastern PA. If Santa flew over he must have frozen his tush. Anyway, Peter, some of my best shop hours are spent seeing how small a hole I can work through. I find small pieces of wood just too pretty to throw away and turn them into hollow forms with 1/2" openings. I also own 3/8" curves from JJ but don't find them nearly as useful as my sizable hand full of shop made tools. I don't bend any bars. There is just too much torque even with my arm brace handles. I merely cut 3/8" rod, some drill rod and some cold rolled, drill a hole for the 1/8" cutter at an angle I want, drill and tap for a set screw and try it out. I use cutters that come out at 90 degrees to the bar, 45 degrees and 22 degrees. I grind away any unneeded bar at the tip to allow easier entry into the form. With an entry hole only 1/16" to 1/8" wider then the bar you are using, there is no room for a catch as you enter or exit. With the angled cutters, I vary the length of the cutter to get at places under the shoulder and at the widest diameter. Here are a couple things I found that help. Obviously, the smaller the entry, the smaller the overall form must be. 3/8" drill rod will chatter quickly once you reach 3" or so over the tool rest, so keep your bars short, only as long as you need to reach. For that reason, I don't like curved tools for small openings. Since the entire curve must be past the tool rest to avoid torque, the tool is hanging 3" over the rest from your first cut. My worst catches have been with a 3/8" swan neck tools. The second tip is obvious. Take light cuts as you go deeper. Now, A comment about your desire to make a "two" bars. I was fortunate to take a course with David Ellsworth. As you may know, David makes all his tools. He makes them as I described but he CA glues the cutter into the bars. David doesn't even use an arm brace. He grips a long wooden handle with a hefty diameter to do all his forms. The torque from his style cutter can be controlled by your touch. He also has a large drawer full of tools made from bent screwdrivers, allen wrenches stuck in a handle and other assorted fruits of his imagination made up for some occasion when he had to reach a particular spot inside a hollow form. My point is, make them as you need them from whatever you have laying around. Take 3 one quarter inch allen wrenches, mount them in handles the size of a screwdriver handle, keep the extension from the handle short then cut the short end on one 1/2", one 3/4" and one 1". Sharpen them as you would a HHS cutter. They work great just onside the hole and under the shoulder.
One last thing I've found. If you drill a 3/16" hole in your bar, a 1/8" cutter will fit with a bit of touch up on the corners. However, the larger you make the hole for the bit, the fewer threads your set screw will have. I round the mounting portion of my small cutters, cut only a 1/8" hole allowing me a bit more thread for the set screw. I get less vibration that way.
Sorry for writing a book but, you did ask. By the way, there will be lots of folks who do it differently. This is just my way and it works for me. Merry Christmas.
faust

[Paul Heely]

As Faust mentioned, instead of drilling and tapping for a set screw you might consider using super glue to hold the tip in. All the tips in my shop made hollowing tools are held in with medium CA and I haven't had any problems with them coming loose. To change a glued in tip, use a torch to heat up the end of the tool and the tip will come right out. I was at Ellsworth's a couple of weekends ago and he does have a great collection of hollowing tools bent into all kinds of shapes from all different materials.

[Dennis Ford]

This makes great cutting tips, and is much easier than rounding a square bit.
http://www.mcmaster.com/#8813a28/=pymz2s

[Peter Blair]

Christmas greetings again all!!
Thanks you so much for your input.
I will TRY to answer your questions and say thanks.
Harry - yep, I'm well aware of the need for a hand held cutter to be centred on the shaft, thanks. I may or may not use these with my Kobra or an interchangeable handle.
Dennis - You are probably right about the 'universal' aspect I was looking for. A lot of you are suggesting ca as the best method to hold the cutter - this is something I will try, I have also already ordered some round cutters but am quite familiar with sharpening the square ones . . . i will for sure try them. Do you think ca will work as well on a square tool in a round hole?
Charlie - I use my Kobra for just about all my larger forms so, yes, these are intended 'mostly' for smaller hollow forms. I do have the Dway hollower with an outrigger but I was trying to stay away from it for these smaller tools.
Richard - Nope, no typo. I like to use 1/4" cutters on my Kobra but they mostly require a larger bar that I was hoping to make. Thanks for the tip about the photocopier and getting full side drawings. I just my try this approach. The drill press is a cool suggestion for bending. I do have a small bender that I was hoping to try as soon as I decided on shapes.
Faust - Great note!!! Thanks for all the information. Any chance you could post a photo or two of your bars? When you drill at angles to your main bar does this not produce the side torque that you don't like with bent bars? The Kobra system really consists of what you indicate is your preference but I would guess that there would be lots of side torque if used in a handle. I have just started using all wrenches and will give your suggestion a try. Can you sharpen them more than a few times? I do have lots of old screwdriver etc and will sure give that some thought as well. Do you completely round your small cutters so they fit in a 1/8" hole like the Jordans?
Paul - As mentioned earlier the CA idea seems like the way to go.
Dennis - Thanks for the link. I ordered a couple of sizes. Exactly how do you sharpen them? Do you flatten one side and then hold in a handle to sharpen? I really like to sharpen square cutters when removed from the handles using my Robo Rest.
Once again it is sure gratifying to have all you experienced mentors so easy to approach and so willing to share!!
Sure hope I covered all your questions and suggestions!

[Jamie Donaldson]

A 1/8" cutting tip is very agressive, a reason that most experienced hollowers has standardized on the 3/16" square cutters. Since most of the cutting with these tools is done with a sweeping motion, the extra size in the 3/16" tip has less tendancy to bore straight into the walls, creating a vase rather than a hollow vessel!:eek:

[Peter Blair]

Thanks jamie. I do indeed understand that this may be an issue. However to hollow through a small hole it seems to me imperative that I use smaller bars thus smaller cutters, Vases aren't that bad are they?

[Faust M. Ruggiero]

As Faust mentioned, instead of drilling and tapping for a set screw you might consider using super glue to hold the tip in.
Paul, Interestingly enough, the CBN wheel has caused me to remove bits from the bar to sharpen them. If you remember when you were at David's, he sharpens bits by using the corner of his grinding wheel. I can't do that with the CBN because it has square corners and no grit on the sides.
Peter, I will take a couple photos and send them to you. There is no rocket science involved.
By the way, Jamie's comment about 1/8" cutters is very true. The only reason I use them is they allow me to drill a hole in the bar small enough to leave some meat on the bar. They require a deft touch or you will quickly find the bit buried and a really nasty catch. Taking more than 1/16" bite effectively allows the tip to be cutting on both sides. OOPS!!!!

[Peter Blair]

It's me again!
For Christmas I received a gift certificate to my favourite Toy Store so I thought that maybe it would be better just to bite the bullet and purchase a small set of hollowing tools. After reading your comments and reading just about everything I could find on the internet I decided to try the mini set of hollowers by Kelton.
Wow! Was I in for a surprise. These are about the worst example of a fabricated tool that I have come across. Don't know if they are being made off shore or what but they are horrible. The grinding that was done on the top must have been with about a 40 grit and the sharpened ends!!!! Well let me tell you, my 10 year old grandson could have done a better job. The cutting ends were not round and had sharp spots and corners and are just terrible. In addition, to all of you who had indicated that it is important to have the cutting edge align with the centre of the shaft . . . take a look at the sketch I have attached! Sorry the sketch is not that easy to see but if you click on it I think you will get the idea. So back I go to return these as soon as I get the chance and I'm now back to the drawing board as far as making my own.
278165

[Faust M. Ruggiero]

Peter,
Actually, Kelton hollowers are very good tools. They are made differently and sharpen differently than you might expect. First of all, do not grind them. That seemingly poorly ground top is actually a separate piece of metal affixed to the shaft. You sharpen them by hand. Merely take a small diamond hone and stroke the portion you want sharpened from the bottom up to refresh the burr. They take a bit of practice but work well but not aggressively. I also remember they do not want you to create a burr on the inside of the hook. Google "how to sharpen them" and you will find lots of info. I use mine for finishing cuts not roughing.
I took a picture of several tools for you. Now I have to figure out how to get the pix off my phone and onto the desktop. I may have to wait until I am in front of my own computer so I can down load them to Lightroom then uploaded to the Creek.
faust

[Robert Henrickson]

I've been very happy with my Kelton hollowers, one of the relatively small sizes. They are my go-to tool when I am hollowing small things. Sharpening is as Faust describes.

[Peter Blair]

Thanks again everyone who had a comment to make. Faust especially with the book he included!
After reading all the comments a couple more times I was still unsatisfied with the finish and grind of these tools and returned them to the Toy Store. I took a closer look at them after your second comment Faust but the edge shape was ground soooo bad I just couldn't bring myself to even try them. Of course I would have had to smooth all the jagged cutting edges and then I doubt if I could have returned them.
So, I am back to the drawing board as far as making my own. I have bent the 3/8" rods and drilled them with a 3/16" hole and am waiting for the 3/16" round cutters from McMaster Carr to arrive. Still not sure exactly how to grind them but I suppose I will either split the cutting end or just grind half of it away.
While I am waiting for those to arrive, I will make a jig for my grinder that should allow me to grind the ends of the 3/16" square cutters round like those used in the John Jordan set of tools so at least I can get started. My plan is to take a round section of aluminum, drill it large enough to take a cutter with a set screw to hold it in place, then with my wood lathe turn a 3/8" stub so I can use a drill to spin it against the wheel of my grinder. Sound ok?
As soon as I am set up I'll post a few photos.

[Peter Blair]

Spent a little time in the shop this am while waiting for Seattle Seahawks game and here is what I came up with.
These are 3/8" drill rod (probably didn't need drill rod but it is what I had) with 3/16" cutters inserted into 3/16" holes. I made a little jig and ground the shank of the cutters round to fit into the holes. I used set screws to hold the cutters cause I have a nice jig to sharpen these bits and need to remove them to sharpen them. Not too sure about the final shapes but the cutters at least line up with the centre of the shaft. I used a torch to heat the 3/8" drill rod to bend and think I could do again if the shapes need a little adjustment.
278264
If anyone is interested I'll add to this thread as soon as I have a chance to try them out.
Thanks for looking and all the help!
Sorry I tried to delete the smaller photo but can't figure out how . . .