Seashells cast in dyed Epoxy on TM Sigma's
I shall try to explain the difficulties in turning these pens after you seen the photo's
1st off, I didn't really want to make these but a good customer requested one, so he bought 2 ..
The shells are incredibly hard and will blunt an HSS tool after 1 pass, maybe 2. So Carbide is the way to go.
Cutting these on the bandsaw presented no issues except that the week before I had put a new blade on, and will probably have to replace a lot sooner than expected.
Drilling is an issue, last time I made some if these is was for a Sirroco and a Zeta, I used my colt drill bits but the next time I tried to use them on wood blanks I realised the shells had blunted them considerably. I'm sure there are decent bits out there that could cope but you really do not want any "wandering". I still have the correct size Colts that I had replaced recently, so I though i would use the old ones, they worked a treat. Knew I kept them for a reason.
All the blanks had to be painted on the inside, Acrylic spray paint is the quickest and easiest to use. Once dried I use a quality 2 part epoxy. I've tried the stuff that comes in a double tube and got fed up with one side coming out faster than the other, the nozzles getting in a mess and never being able to finish them off.
Squaring them off was easy too on the disc sander.
So to the turning. TBC started slow to get them round and then about 2800 with a round carbide cutter, very light cuts. The cutting is pretty rough as the epoxy cuts easier than the shells, in fact I reckon the shells were more scraped than cut. As you turn these you realise they are full of voids, not from the epoxy not reaching the gaps, but from the natural voids in the shells, and I mean there are lots and lots. I figured I would wait till later to worry about these.
On the 3 pens, 6 blanks I only had 1 what I would call a "blow out", just a small one but with all the voids I knew it would be an easy fix.
So now I've got the shape I want and am starting to get close to finished size. At this point I mix some more epoxy and add mica powder to match the colour. Blow the blank free of dust and plaster the epoxy all over pressing it into the voids with a wooden coffee stirrer. I let this cure for 15 minutes (it's 5 minute epoxy) then take it off the lathe and leave it to set. The bottle says fully cure after an hour. So I got more blanks to do and crack on with them. I finish all 6 this way and call it a night.
Next day I put them back on the lather, first thing is to get rid of all the excess epoxy and get back down to the blank. Now this is where the lather police will be upset, out come the 80 grit, slow speed, extraction on and I start sanding. After all this work I do not want to run the risk of blowing it at at the bushes and we are only talking the last 1 or 2mm.
Once I'm down to finished size, I blow out all the voids that have appeared, at this point I work my round the blank with Medium CA, I let it dry without activator, once it is I use the carbide, lightly cut off the excess and start the sanding process again but starting with 240 abranet with the lathe spinning, then It's laterally with 240, 320, 400 and finally 600. Check it for any scratches and get rid of them.
Be careful with epoxy blanks and too much heat when sanding can make them move as they get soft.
I tried polishing them up but wasn't happy with the finish.
So 4 coats of thin ca and 6 of medium. then wet sand with micromesh pads, then finally some auto polish.
A lot of work, probably 2.5 days with cutting, drilling, painting, drying, turning etc etc.
But worth it, customer was very happy and paid me lots of money.
Hope this helps someone who's thinking of trying these. Def not for novice or anyone who wants to rush.
Good Luck
Brad
I shall try to explain the difficulties in turning these pens after you seen the photo's
1st off, I didn't really want to make these but a good customer requested one, so he bought 2 ..
The shells are incredibly hard and will blunt an HSS tool after 1 pass, maybe 2. So Carbide is the way to go.
Cutting these on the bandsaw presented no issues except that the week before I had put a new blade on, and will probably have to replace a lot sooner than expected.
Drilling is an issue, last time I made some if these is was for a Sirroco and a Zeta, I used my colt drill bits but the next time I tried to use them on wood blanks I realised the shells had blunted them considerably. I'm sure there are decent bits out there that could cope but you really do not want any "wandering". I still have the correct size Colts that I had replaced recently, so I though i would use the old ones, they worked a treat. Knew I kept them for a reason.
All the blanks had to be painted on the inside, Acrylic spray paint is the quickest and easiest to use. Once dried I use a quality 2 part epoxy. I've tried the stuff that comes in a double tube and got fed up with one side coming out faster than the other, the nozzles getting in a mess and never being able to finish them off.
Squaring them off was easy too on the disc sander.
So to the turning. TBC started slow to get them round and then about 2800 with a round carbide cutter, very light cuts. The cutting is pretty rough as the epoxy cuts easier than the shells, in fact I reckon the shells were more scraped than cut. As you turn these you realise they are full of voids, not from the epoxy not reaching the gaps, but from the natural voids in the shells, and I mean there are lots and lots. I figured I would wait till later to worry about these.
On the 3 pens, 6 blanks I only had 1 what I would call a "blow out", just a small one but with all the voids I knew it would be an easy fix.
So now I've got the shape I want and am starting to get close to finished size. At this point I mix some more epoxy and add mica powder to match the colour. Blow the blank free of dust and plaster the epoxy all over pressing it into the voids with a wooden coffee stirrer. I let this cure for 15 minutes (it's 5 minute epoxy) then take it off the lathe and leave it to set. The bottle says fully cure after an hour. So I got more blanks to do and crack on with them. I finish all 6 this way and call it a night.
Next day I put them back on the lather, first thing is to get rid of all the excess epoxy and get back down to the blank. Now this is where the lather police will be upset, out come the 80 grit, slow speed, extraction on and I start sanding. After all this work I do not want to run the risk of blowing it at at the bushes and we are only talking the last 1 or 2mm.
Once I'm down to finished size, I blow out all the voids that have appeared, at this point I work my round the blank with Medium CA, I let it dry without activator, once it is I use the carbide, lightly cut off the excess and start the sanding process again but starting with 240 abranet with the lathe spinning, then It's laterally with 240, 320, 400 and finally 600. Check it for any scratches and get rid of them.
Be careful with epoxy blanks and too much heat when sanding can make them move as they get soft.
I tried polishing them up but wasn't happy with the finish.
So 4 coats of thin ca and 6 of medium. then wet sand with micromesh pads, then finally some auto polish.
A lot of work, probably 2.5 days with cutting, drilling, painting, drying, turning etc etc.
But worth it, customer was very happy and paid me lots of money.
Hope this helps someone who's thinking of trying these. Def not for novice or anyone who wants to rush.
Good Luck
Brad
