duncanh
Established Member
I tend not to do WIP photos as I find that stopping to take photos disturbs my turning progress too much. For this project, however, I thought I would as it's a little unusual and stopping for photos was a good way to take a break and make sure that I was concentrating properly (which as you'll see was very important!)
Please note - this is a fairly advanced project that involves potentially unbalanced pieces of wood spinning off centre with the possibility of catching fingers (or any other stray body part). If you don't manage to balance things correctly your lathe bearings may suffer. It's probably best if your lathe has variable speed.
I've done off-centre pieces before using lead to counterbalance but this was the first time I've used a base and mount combination. The idea is taken from an article by Terry Scott in a recent Woodturning magazine.
Step 1 - I forgot to photo this one, but it was basically making sure that the wood was square, flat and had a fairly good sanded surface on both sides. Sanding the flat part of the front surface is possible at the end but there's the risk of rounding over edges.
Step 2 - Prepare a flat piece of wood on a faceplate (I'll call it the base). I've used this one for a donut chuck in the past so it has holes round the outside (which you can ignore for this project).
Step 3 - Prepare a mounting piece to hold the work (I'll call it the mount). This will be fastened to the base (off-centre) and have the work mounted on it.
The grey numbered pieces at the corners are short lengths of metal covered in gaffer tape (to prevent them marking the wood) which will go over the corners of the wood and hold it down. The other bolts are fitted fairly tightly against the edges of the wood to stop ant movement. It doesn't matter if the threads mark the sides as any marks will be covered by pyrography. For future work I may add protection.
The bolt holes have screw inserts.
On the 2-4 diagonal you can see that I've marked the centres for the 2 bowls that I'll cut.
Step 3 - Screw the mount onto the base so that the first of the centre marks on the mount is on the centre of the base. The easiest way to line it up is to hold the mount in place with the tailstock against the centre mark. Screw the mount to the base using long, wide screws
Step 4 - Place the wood in the mount and secure in place. The mount and wood are now considerably off-centre and need to be balanced so that you can turn at a reasonable speed. To acheive this fasten pieces of lead to the back of the base. I do this using strong screws. Finding how much weight to add and exactly where to put it takes a while as you need to fix it in place and check for balance each time.
Step 5 - Make sure that nothing is in the way of the wood by rotating by hand. Set the lathe on it's lowest speed, switch on and slowly turn up the revs. If you've done a good job of balancing weights you should be able to get to a reasonable speed for turning. I reached somewhere between 400 and 500. Turn as you usally would but be extremely careful, keeping everything behind the rest. I pencilled in the turning area just to ensure that I didn't go too wide.
If you're inthe habit of stopping the lathe and stopping the piece by hand then I suggest that in this case you don't!
Here's the first part turned
Step 6 - Take the wood off the mount, take the mount off the base and re attach it so that the second centre mark for the piece is over the lathe centre. Now reattach the wood to the mount and fix it in place as before. This time everything is more off centre so more lead will be needed.
Step 7 - Mark the bowl edge as before. I discovered that my outboard rest system wouldn't extend under the off-centre piece so I had to use my long tool rest supported with one of my hollowing bars to stop it flexing.
Step 8 - Once the turning is done tidy up any marks on the surfaces of the piece, mark out the pattern and head inside to get stuck in to some marathon pyrography sessions
Step 9 - Use a drill mounted bristle brush to remove excess charing so that it doesn't contaminate the wood pores. Apply severeal coats of finishing oil (Chestnut for me). Wait for it to dry then use the bristle brush again.
I hope this provides some ideas
Duncan
Please note - this is a fairly advanced project that involves potentially unbalanced pieces of wood spinning off centre with the possibility of catching fingers (or any other stray body part). If you don't manage to balance things correctly your lathe bearings may suffer. It's probably best if your lathe has variable speed.
I've done off-centre pieces before using lead to counterbalance but this was the first time I've used a base and mount combination. The idea is taken from an article by Terry Scott in a recent Woodturning magazine.
Step 1 - I forgot to photo this one, but it was basically making sure that the wood was square, flat and had a fairly good sanded surface on both sides. Sanding the flat part of the front surface is possible at the end but there's the risk of rounding over edges.
Step 2 - Prepare a flat piece of wood on a faceplate (I'll call it the base). I've used this one for a donut chuck in the past so it has holes round the outside (which you can ignore for this project).
Step 3 - Prepare a mounting piece to hold the work (I'll call it the mount). This will be fastened to the base (off-centre) and have the work mounted on it.
The grey numbered pieces at the corners are short lengths of metal covered in gaffer tape (to prevent them marking the wood) which will go over the corners of the wood and hold it down. The other bolts are fitted fairly tightly against the edges of the wood to stop ant movement. It doesn't matter if the threads mark the sides as any marks will be covered by pyrography. For future work I may add protection.
The bolt holes have screw inserts.
On the 2-4 diagonal you can see that I've marked the centres for the 2 bowls that I'll cut.
Step 3 - Screw the mount onto the base so that the first of the centre marks on the mount is on the centre of the base. The easiest way to line it up is to hold the mount in place with the tailstock against the centre mark. Screw the mount to the base using long, wide screws
Step 4 - Place the wood in the mount and secure in place. The mount and wood are now considerably off-centre and need to be balanced so that you can turn at a reasonable speed. To acheive this fasten pieces of lead to the back of the base. I do this using strong screws. Finding how much weight to add and exactly where to put it takes a while as you need to fix it in place and check for balance each time.
Step 5 - Make sure that nothing is in the way of the wood by rotating by hand. Set the lathe on it's lowest speed, switch on and slowly turn up the revs. If you've done a good job of balancing weights you should be able to get to a reasonable speed for turning. I reached somewhere between 400 and 500. Turn as you usally would but be extremely careful, keeping everything behind the rest. I pencilled in the turning area just to ensure that I didn't go too wide.
If you're inthe habit of stopping the lathe and stopping the piece by hand then I suggest that in this case you don't!
Here's the first part turned
Step 6 - Take the wood off the mount, take the mount off the base and re attach it so that the second centre mark for the piece is over the lathe centre. Now reattach the wood to the mount and fix it in place as before. This time everything is more off centre so more lead will be needed.
Step 7 - Mark the bowl edge as before. I discovered that my outboard rest system wouldn't extend under the off-centre piece so I had to use my long tool rest supported with one of my hollowing bars to stop it flexing.
Step 8 - Once the turning is done tidy up any marks on the surfaces of the piece, mark out the pattern and head inside to get stuck in to some marathon pyrography sessions
Step 9 - Use a drill mounted bristle brush to remove excess charing so that it doesn't contaminate the wood pores. Apply severeal coats of finishing oil (Chestnut for me). Wait for it to dry then use the bristle brush again.
I hope this provides some ideas
Duncan
=D> 
