Likes: 0
Needs Pictures: 0
Picture(s) thanks: 0
Results 1 to 13 of 13
Thread: Cast alluminium surface finish
-
28th Dec 2020, 06:33 PM #1Most Valued Member
- Join Date
- Jul 2006
- Location
- Athelstone, SA 5076
- Posts
- 4,258
Cast alluminium surface finish
Is it easily possible to get a smooth surface finish when casting aluminium?
Is it as simple as using fine sand. I need to make sinker mould and want the finish of the lead to be reasonable smooth.
-
28th Dec 2020, 08:08 PM #2Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
- Posts
- 6,562
It's basically the sand. For a fine finish you may even have to got to plaster (but well dried). Another alternative might be a split Al mould, similar to that used for blackpowder shot/ bullets.
Michael
-
28th Dec 2020, 09:48 PM #3Most Valued Member
- Join Date
- Jul 2006
- Location
- Athelstone, SA 5076
- Posts
- 4,258
-
29th Dec 2020, 12:03 AM #4Golden Member
- Join Date
- Jan 2016
- Location
- Wodonga Vic
- Age
- 38
- Posts
- 633
When they cleaned out the water jet cutter tank at work I took some of the fine, used garnet home and dried it out, I haven't cast anything with it yet but you can imagine how fine it is after going through the water jet, I'm not sure if the % of metallic particles will have any affect on the casting, they may impregnate the outer layer but I doubt that will matter for me. got any shops with a water jet near you?
-
29th Dec 2020, 01:17 AM #5China
- Join Date
- Dec 2005
- Location
- South Australia
- Posts
- 1,658
A couple of years ago I was in QLD and my mate's mate was using some form of silicone to cast lead sinkers
-
29th Dec 2020, 01:38 AM #6China
- Join Date
- Dec 2005
- Location
- South Australia
- Posts
- 1,658
How smooth do sinkers need to be If you want high finish like bullet moulds they are machined in Aluminium on a mill, sand finish would be Petrabond for a really fine finish you could use Delft Clay but that is pricey ( and hard to get at the moment). Mt mate uses a Douglass type setter I don't know ho he makes his moulds I can ask him after the 11th when he comes back to civilisation.
-
29th Dec 2020, 06:50 AM #7Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
- Posts
- 6,562
The plaster needs to be well dried so that there is no water to flash to steam. Probably some time in the kitchen oven would do it.
What shape are the sinkers? It may be just as easy to machine a cavity directly into the Al block. I'm off until the 11th, so could help if needed.
Michael
-
29th Dec 2020, 09:46 AM #8Most Valued Member
- Join Date
- Jul 2006
- Location
- Athelstone, SA 5076
- Posts
- 4,258
sinker shape is akin to a bullet eg 20mm round with a flat bottom then about 1/2 along tapers to a point...or small length round bar with a solid cone on one end
20201229_114201[1].jpg
20201229_115545[1].jpg
the round solids fit into the mould to adjust weight. My intention is to make the moulds so that spaces are not needed.
-
29th Dec 2020, 12:28 PM #9Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
- Posts
- 6,562
I have a 60 degree included angle countersink that is 19.5mm in diameter. I think you would want to pour into the base of the sinker rather than the top (potential to freeze off too quickly), so an open top mould would probably do it. Have a think, let me know...
Michael
-
29th Dec 2020, 04:40 PM #10Most Valued Member
- Join Date
- Jul 2006
- Location
- Athelstone, SA 5076
- Posts
- 4,258
-
29th Dec 2020, 04:46 PM #11Most Valued Member
- Join Date
- Jul 2006
- Location
- Athelstone, SA 5076
- Posts
- 4,258
-
29th Dec 2020, 07:36 PM #12Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
- Posts
- 6,562
I was thinking something like this -
Sinker.jpg
The countersink would not mill the material out as such. I'd drill most of it out and use the countersink just to clean up. The wire would go in when the mould halves were fastened together. There might be a little bit of leakage around the wire but if the mould was resting on a sand tray, it would not be much. For wire, I'd just use a bit of stainless welding wire twisted up (I have 0.9 or 1.6 if the fish are really big...). The sketch is a bit dodgy - there should be less distance between the bottom of the mould and the bottom of the cavity.
It could be moulded the other way up but the mould gets more complicated with how to get the metal in and the part out. This way you can make the body a little longer and clean up the base in the lathe if needed.
Michael
-
31st Dec 2020, 10:13 AM #13Most Valued Member
- Join Date
- Jul 2006
- Location
- Athelstone, SA 5076
- Posts
- 4,258
if you look closely at one of the pics I posted you will see a metal thread (spot welded to wire) which allows for a plastic tip to be screwed onto the base of sinker....this of course must be cetrally located.
this pic should explain
20201223_170539[1].jpg
Similar Threads
-
Brass Casting, Poor Surface Finish
By NedsHead in forum THE FOUNDRYReplies: 1Last Post: 30th Jul 2018, 12:40 PM -
War Finish cast iron surface table
By zbm in forum METALWORK GENERALReplies: 1Last Post: 6th Jul 2018, 03:27 PM -
surface finish
By TED C in forum METALWORK GENERALReplies: 9Last Post: 7th Aug 2015, 07:48 AM -
Surface Finish Problems?
By Iggsy in forum THE HERCUS AREAReplies: 22Last Post: 15th Jan 2012, 01:59 PM -
Resonant frequencies and surface finish ?
By morrisman in forum METALWORK GENERALReplies: 26Last Post: 9th Oct 2011, 06:08 PM