The Home Machinist!

Does anyone have a method to remove residual investment from a hallow brass casting. I'm casting condensers for sight feed lubricators. The attached photo shows a condenser casting sectioned to check wall thickness and to proof machining dimensions. The amount of residual investment is obvious. The sphere portion of the condenser is 1" diameter and the walls .060". I've tried the usual hot casting agitated in hot water. I tried a hooked wire. But the end holes are too small to reach very far off center. Is there a chemical method or any other trick. A long time in process or in solution is not an problem.

Thanks, Dave

Sand-blast it out... thin pipe sealed on the end, but with a slot in the side near the end. Blow mild abrasive through it while you rotate the ball and raise and lower it. Keep the large opening of the product aimed down so the casting material can fall/blow out. just don't overdo it and wear a hole in the ball.

Charles T. McCullough wrote: ↑Mon May 01, 2023 7:34 pm Sand-blast it out... thin pipe sealed on the end, but with a slot in the side near the end. Blow mild abrasive through it while you rotate the ball and raise and lower it. Keep the large opening of the product aimed down so the casting material can fall/blow out. just don't overdo it and wear a hole in the ball.

Thanks, Good idea!

Dave

The Rail Braces in the photo below were sandblasted in a Sandblasting Cabinet.

Cabinets are available in cheap to expensive, my cabinet is a slight bit smaller than I would like, but it was given to me for free.

It was not needed by the company anymore, so the boss told my brother, "get rid of that!", which he did.

Charles T. McCullough wrote: ↑Mon May 01, 2023 7:34 pm Sand-blast it out... thin pipe sealed on the end, but with a slot in the side near the end. Blow mild abrasive through it while you rotate the ball and raise and lower it. Keep the large opening of the product aimed down so the casting material can fall/blow out. just don't overdo it and wear a hole in the ball.

kinda reminds me of things urologists do these days...

An older thread, but I'll respond anyway. I've had luck removing investment with a pressure washer. The investment I've been cleaning was on the outside of parts, but if a piece of tubing was fitted onto the wand you might be able do the interior - at least that's what some have used for cleaning scale from small boilers. The pressure washer is effective but messy. There are also certain hazards with the pressure washer, but they are manageable.

ultrasonic cleaner works well

At the investment casting foundry, sodium hydroxide (Draino) heated was used. Now, potassium hydroxide heated to 400 degs F is used. All in all, I would try to avoid the chemical processes, kind of nasty.

Jim B

I haven't had any luck with ultrasonic, including if I add a bit of citric acid and detergent. However, It may be that my ultrasonic cleaner is on the wimpy side.