Sand Cores

[doubleboost]

Hi
Lads
I am about ready to cast the cylinder for my mill engine
The cylinder will be cast in bronze
It is a fair size so a central core will be needed to save on metal and make machining easier
The ingredients i use are
4 Parts silver sand
1 Part clean moulding sand
1 Part core binder (wheat flower)
Temperd (dampend) with molasses disolved in hot water

A piece of steel pipe is used for a mould (this is split full length and held closed with a couple of hose clips)

The dry ingredients are mixed together

The liquid is slowly added untill the mix becomes nice and fluffy

This is lightly rammed in to the tube
A 5mm rod is inserted through the centre (this helpes the core to vent)

The hose clips are releaded and the core gently pushed out on to a piece of steel plate

I only need one but i always make a few and select the best
The next part is best done when the wife is out :slaphead::slaphead:
The cores and plate are cooked in the top of the oven at 200 deg C untill they stop smoking These ones took 40 minutes

Once cooled they should be hard and a bit crumbly
If they are hard like stone the mix was too wet and rammed too hard

A better core is obtained if linceed oil is used instead of molasses but this really stinks the house out
John

[Pete.]

My wife would stab me if I did that - I'd probably get away with using the barbeque though.

[Fredbare]

Most interesting, and very well shown, thanks, looking forward to see how they turn out.

John

[saw]

Nice done, thanks for showing 

[Stilldrillin]

Nicely explained, John! 

Not too sure about using Herself's equipment........ She would know what I'd been up to, somehow! 
I couldn't stand the consequences......... 

David D

[NormanV]

You're all cowards. If I want to use any kitchen equipment I just use it. I don't ask for permission.
I never have any problems.


I might just add that I am not married, ha!

[micktoon]

     Alreet John , Them cores look good enough to eat mate   You will be giving the Hairy Bikers a scare at this rate , not to mention landing yourself with cooking duties if your lass finds out you know how to use the cooker 

  They look really good  and well explained too, I am looking forwad to seeing being used in the casting

  Cheers Mick.

[Meldonmech]

Hi John
              The recipe looks interesting I have been using linseed oil in my recipe, and using  the kitchen oven. I have not been banned from the house but have come dangerously close. My experience with core making has shown that the composition proportions are critical to ensure success. What ratio of molasses to hot water do you use?, and how many parts of this mix do you add to the recipe?

             Cheers David
 

[doubleboost]

Hi
David
This should help
http://madmodder.net/index.php/topic,7501.0.html
I have just orderd some sodium silicate to have a bit play with
John

[Pete W.]

Hi there, John,

This might seem a bit off-topic     but do the hexagon heads on your hose clips fit a 3 BA spanner?

Best regards,

Pete W.

[doubleboost]

Hi
They are 6 mill hex
You can get 7 mill as well
John

[PekkaNF]

Some clips seem to have 1/4" hex....standard bit driver socket ie. any bit screw driver woithout bit seems to fit perfect.

Pekka

[Pete W.]

Hi there, John and Pekka,

Thank you both for your replies.

I asked because I occasionally have to take care of one of my wife's toys, the pond pump.  Using a flat-bladed screwdriver on the head of the hose clip while holding the weed-covered, slippery hose or fitting in the other hand is unpleasant, to say the least!  The screwdriver always seems intent on damaging that other hand!  Last time I did better with a 3 BA socket on my 1/4" drive socket set (bought from K.R.Whiston of New Mills many, many years ago!) and I wondered how consistent the screw head sizes are across the various hose-clip manufacturers.

I know that the Jubilee Clip people used to offer a dedicated driver but I haven't seen one listed recently.  (Before everyone rushes off and does a Google search, I acknowledge that I haven't done that myself yet but ought to.)

Thanks again and enjoy the Bank Holiday (UK readers).

Best regards,

Pete W.

[vtsteam]

Did some baked cores today using this method, which is different than the one I used in the past (Gingery method). There are a couple points worth noting here:

1.) The slot in the tube should be at least 1/4 of the diameter wide to allow easy release. So a 1" dia tube needs a 1/4" slot.

I had a lot of problems extruding until I widened the slot. This is particularly important on the smaller diameter cores -- I was making cores today using "half inch" PVC water pipe (5/8" ID actual).

2.) You lose some diameter because of the slot and because of shrinkage -- finished cores were 9/16" O.D.

3.) Very important: your cores will both compress when extruding and shrink in length while baking. I made a batch of cores using a 5" length of pipe packed full -- but the finished cores were 4-1/2" long -- so all were a complete loss when I went to use them. Bummer!

So as a general rule, allow 10% or 1/2" -- whichever is more, in the length of the tube. You could allow a generous excess and plan to cut off the ends, but in my case, I needed a wire in the smaller diameter core to give it enough strength to hold together while extruding. And it would be nearly impossible to reduce the length of a core with wire in it. So you really do need to use a correct length tube.

-- Larger cores are MUCH easier to make than smaller diameters.