woodbowlsandthings

November 11, 2017

Video Hollowing

Filed under: Wood Lathe — Tags: , , , , , , , , , , — peteblair @ 4:03 pm

I know that there are lots of turners who are either already hollowing using video of are thinking about trying this technique. This Blog is meant to be a jumping off spot for those who are still contemplating the process. It’s only the way I do it and not by any means a difinitive way to proceed. I do not plan to share the details of the equipment I use because there are so many choices and I purchased so many years ago the items may no longer be available.

As far as I can remember, the use of video in hollowing became known about 5 years ago when a world renown turner began demo’ing and selling his system.

For those of you how have been living in a cave or on another planet for the past 5 years the technique involves positioning a camera above the cutter and then drawing it’s outline on a sheet of mylar which then appears on the video screen when the cutter is actually in the form. I hope I have explained it well enough but please feel free to contact me should I be able to add anything or help you better understand the technique.

So about 5 years ago and being the cheap SOB that I am, I thought I could hack together my own system. I had an old MS laptop laying around and I had WIFI phones and cameras with the ability to connect to it, but, of course that wasn’t enough for me. I soon was scouring Amazon for cameras etc. I found a very cheap, new I was told, Colonoscope camera. I sure hope it was new!! It had it’s own light but the picture was a problem.
Anyway, to cut a long story a little shorter, I found that the Lap top was a pain to set up and take down and by the time I ran the software to get everything working I could have hollowed several vessels using my laser. In addition, the web WIFI cams all had a short ‘lag’ which drove me nuts!!  This led me to stop trying the process and continue my old ways using a laser.

I hadn’t totally given up though as I discovered that several turners were using Back-Up Automobile camera set-ups which included a small monitor and camera. Yep, a few were even shown with the lines to back between which I apparently were pretty easy to ignore when hollowing.
So of course, I had to try those as well and also found a really cheap video surveillance camera without the monitor and bought that too.

When the part arrived I took a quick look and with all the wires etc. it all seemed way too involved. I’d just rather be turning than messing with all those wires!!

It might be my age or ?? but I have a great deal of trouble remembering peoples names and the turner who demonstrated his video techniques at the last meeting of the Vancouver and District Wood Turners Guild has fallen into that category.
It’s too bad because it was his demo that got me thinking a little more about utilizing this technique.

So the next day I hunted around my shop, it took me about 2 hours to remember that I had stashed all the parts in an old sewing box.

The only easy to hook up was the surveillance camera because it came with a 12 volt brick power supply. The back-up-system was designed to wire directly to the 12 volt of a vehicle. Lucky for me I have ‘bricks’ of all voltages and designs in boxes and drawers. I found a 12 volt one, cut the cord and wired it to the back-up system and hooked up the surveillance camera and quickly discovered that the distortion was way too much at close range to be usable.

So with wires going every which way I connected the complete back up system. Dragged it over to my lathe and with a few minor modification had it up and running in no time. It worked great but the back up monitor is only about a 7″ screen. I need something bigger.

I remember that we moved a cable box from a 17″ tv in our kitchen to a room where one of our grandsons ‘hangs’ so he could use it on a large tv that his dad has left for us to store. My wife was quite happy to have it out of the cabinet that it was in now she has more shelf space to display her ‘stuff’.

Ok, so now I am really on to something. I quickly disassembled the foot that the tv stood on and made an aluminum plate from which I could hang it on my exhaust fan box right at the end of my lathe. With a few quick changes it was up and running perfectly.

As you can see from the photos I hold mylar film on the tv with magnets and draw the outline of my tool on it with a sharpie. One cool thing about using the magnets as opposed to tape or ?? is that I can easily reposition it  should I change the angle of the cutter. In addition I can keep all the old sheets to reuse anytime I am using this system and thus don’t need to keep redrawing the cutter. If I like I could actually leave the TV in place but I need to come up with some sort of cover to keep the dust out so for now I stash it on a shelf. The camera and arm it is attached to simply hang on the wall behind my lathe. The camera does have a small lens cover. I’m not totally convinced that the camera is totally suitable and I continue to search for a cheap replacement. What I believe would work even better is what is termed a ‘closed circuit’ camera.

A couple of ideas that were shared at our last meeting that are exceptionally helpful are to place a white or black piece under the turning to provide contrast at the edge which helps to see where the cutter is. Another is if a round magnet is placed on the screen over the cutter and extending outward it provides a means to ensure the finished thickness is easily delineated.

 

 

 

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November 10, 2017

Negative Rake Scraper

Just a quick note to let anyone who might be interested, know that I now use a negative rake scraper with my hollowing rig. Up till recently I was using a tear drop shaped scraper sharpened in the standard manner but found that on occasion it was just a little grabby.
I thought why not make it into a neg rake scraper so I ground it to about a 60 degree included angle.
After changing the angle the center of the scraper was no longer on the center line and to make up for that I just added a small brass shim under the scraper. I think it is still slightly below center but it seems to work just fine for me.
Seems to work just fine for me.

 

March 15, 2017

Drying Wood

Like many if not all wood turners I often get lucky and am able to turn green wood. Of course this means that we need to find a way to get it dry after we either rough turn it or turn it to finish. Sometimes I turn hollow forms so thin that they are almost dry when I finish but more often there is still some moisture that needs to be removed without the piece cracking.
Some turners let it dry by gradually allowing exposure to the air by many means such as bagging, boiling, putting in shavings, setting on the floor and gradually moving them higher in the shop. Most of the methods take a while and we really want to hurry the process.
Most turners agree that if the inside of a piece dries faster than the outside the wood tends to sort of compress and limit cracking. Some people wrap with the outside with plastic wrap, some coat with paint or a wax in emulsion. This lead me to my new method.
This winter has been pretty damp with lots of snow and rain and we were often drying boots and runners etc with a relatively cheap ‘Boot Dryer”.

The one I have is adjustable as to time it runs and has the option of using heat or not.
By adding hollow sections of plastic pipe etc to allow the air to get into and circulate inside the bowl or hollow form the drying process is sped up.


I am not a scientist and have a very limited knowledge of it’s principals and as a result I am unable to actually quantify the results of my method. All I know is that pieces treated like this tend to dry in about half the time of pieces left on their own.
I have only been trying this with fairly thin hollow forms and bowls that I will return to the lathe to sand and finish.
I have no experience with twice turned pieces dryed with this method.

By using the weight of the item I now am confident that the pieces I dry this way dry twice as fast as they do if just left to dry on their own.

I now have a little more information. The week before last I used my boot dryer to dry some small fairly thin bowls made from Gravenstein Apple wood and again the wood dried about twice as fast as a piece I left on its own and I had no cracking. At the same time I dried a small cup shape, it can be seen on the other blog (https://woodbowlsandthings.wordpress.com/2017/04/17/gravenstein-apple-wood/ ‎) about Apple it was dyed and then sanded. I sort of messed up as I didn’t manage to get the bottom as thin as the rest and after about 12 hours on the dryer I noticed some small cracks on the inside. I stopped using the boot dryer and the cracks mostly closed up and never made it to the outside. d

February 16, 2016

Pro-forme Hollowing tool

Last week while I was hollowing an 8″ tall cup form I decided it was past time that I tried the Pro-Forme Hollowing tool that I bought about 5 years ago.

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It has been sitting mixed in with the rest of my hollowing tools and every once in a while I would take the plastic cover off of it and then put it back. I had read that it was especially nice in end grain and even better if the wood is green. Today was the day for a trial. I put it in my Kobra Hollower, but before I started to hollow I drilled a hole with one of my modified spade bits to the depth I wanted to go. The Pro-Forme was set at the factory and worked like a charm. With practice I’m certain I could get as good or better finish inside than is possible with a scraper. I did notice that as I got beyond about 6″ the 1/2″ bar I experienced a little vibration but I was able to go the full 8″.
Thinking about how much I liked the way the tool worked and seeing that I had a spare cutter I felt I should do something to help with deeper hollowing. My first thought was to ask a friend of mine if he could make me a 1″ bar with the end modified to fit the Pro-Forme but this of course required me to buy a 1″ polished steel bar and seemed like it might be more work than it was worth.
I realized I already had a 1″ bar for my Kobra and all I needed was a short extension that could be installed in that bar to which I could attach the Proforma.
Luckily I have a few pieces of drill rod hanging around my shop and was able to find a 2 1/2″ long piece of 1/2″.

I clamped it in a vise and proceeded to notch it out with a zip cut blade my cordless grinder.

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After some grinding, polishing and filing I completed the adaptor and hopefully can now go up to about 14″ deep.

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January 1, 2014

Small Hollowing Tools

Recently I decided I needed some small hollowing tools because I really like to hollow through small holes.

I started to make my own but Christmas came and I was given a  gift certificate to my favourite Toy Store “Lee Valley Tools”. So I decided it might be best to purchase a small set of tools.

I had done a lot of research on the subject and pretty much knew the size I wanted. I was looking for 3/8″ diameter and would like to hollow through a 1/2″ or 5/8″ hole. I bought the Kelton mini hollowing set which has one straight and two progressivly bent cutters. The store didn’t have any on the shelf but had a set on display complete with wax/plastic cutter protectors and I decided buy them.

I was pretty excited, lots of good reviews so I could hardly wait to give them a try. My excitement abated pretty quickly after I got home and when I pulled off the protectors. The ends were very jagged and would need a good grinding to get them smooth and round. They looked very much like a lot of things I see which are made offshore, although I am unsure if this is the case.

After a little soul searching I decided that I didn’t want to grind them round and then find out that they didn’t work well as I would then no be able to return them. Incidentally, every one with whom I discussed these tools rated them very high BUT to a turner they all said the only way to sharpen them was to lightly stroke the bevel upwards with a diamond hone. As well, I was cautioned not to grind them and to never touch the top of the tool as this is where the very thin hardened cutter was and it could be damaged or removed very easily!

So back to Lee Valley to return.

I already have a 1/2″ set of John Jordan hollowing tools and like them vey much especially when used in my Kobra Hollowing Rig, so I decided to order his 3/8″ set. Still waiting for it to arrive.

Now, as I said I had originally planned to make my own and while I was waiting the 3/8″ cutters that I had ordered from JJ arrived at my shop I decided that I might as well make a couple of tools cause I now had all the parts.

First I used my wood lathe to drill 3/8″ holes in the ends of two pieces of 3/8″ drill rod.

Then using the John Jordan bent tool as an example I proceeded to heat and bend the both bars, one with a slightly less bend than the other. I do find that with the JJ tools I have trouble getting back up near the opening and hoped by creating one tool with a little more bend it might help me.

As you can see from the photo, I installed a small set screw to hold the cutters and if you look close you will see the the tip of the cutter lines up with the centre of the shaft. I would have like the bends a little closer to the end of the bar but because I had already drilled the holes for the cutters I couldn’t bend past the end of my hole.

Bent tools
The problem I was dealing with was how big a hole to drill in the 3/8″ rod to hold the cutters.

As you can imagine the larger the whole the less material is left to support the cutter and to thread for a set screw.

I had been told the easiest way to attach the cutters is with CA glue but I have made a little jig to sharpen the cutters and need them to be removable in order to use my jig.
Looks a little like this but can be modified to change the sharpening angle.
JJ Sharpening jig
JJ tools come with square cutters that have the end that is inserted into the bar turned round to enable it to fit in a 3/16″ hole.

I quickly found a short section of 1/2″ aluminum round stock. Drilled a hole in the end to hold 3/16 square. Drilled and tapped a hole for a screw to hold the cutter in place and found it pretty easy to mount in a drill and run against my grinder to round the end.

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Now all I have to do is try them . . . .

If you have any questions please feel free to post here or email me.

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