P.M. Research #5 Steam Engine

[GreenTwin]

Nice perseverence.
Sometimes one has to get a bit creative to make things happen.
Makes me think that a pre-machining annealing session may be a good idea for some kit gray iron castings.
Looking good so far; nice work !
P.S. - Nice lighting on the photos; I always seem to get dark shadows and such in my shop photos.
.

 

[Sarah]

What are you using to drive your small taps? Joe Pie has several videos where he uses a tiny, shop-made driver--it is just a knurled disk of aluminum about 1 inch in diameter. There is just a set screw to retain the tap. He has different different drivers for different size taps.

They are safer to use than most drivers as the small diameter makes it difficult to put too much torque on the tap.

FWIW.

Craig

Hi Craig,

Thank you for your suggestion and I will look at his videos. The tap driver I use is the one in the photograph below. I use the knurled section at the bottom most of the time and the T section when it gets harder. I can be a bit clumsy sometimes and I think with that, the tap being in the blunt side and the harder material proved too much for the poor tap! One of the skills I need to work on

 

[Sarah]

Nice perseverence.
Sometimes one has to get a bit creative to make things happen.
Makes me think that a pre-machining annealing session may be a good idea for some kit gray iron castings.
Looking good so far; nice work !
P.S. - Nice lighting on the photos; I always seem to get dark shadows and such in my shop photos.
.

Thank you for your comments . I have my eye on another P.M. Research casting kit so I'll have to do some research on annealing. I have a couple of led panel lights over my bench which makes it a nice working area. I do need to put some good lighting over my machines, especially the milling machine.

 

[GreenTwin]

I have seen some use a torch to heat a gray iron casting, to anneal it, and a buddy of mine uses an electric kiln to do the same.
I will check with my buddy to see what temperature he uses to anneal his gray iron.
If I were going to anneal gray iron, I think I would use a kiln for a more even and consistent temperature control.
.

 

[Jasonb]

If you have an open fire of wood burner put it in there for the evening and then leave to cool SLOWLY over night in the ashes. Failing that a bucket(metal) or large metal tin with a few holes for air punched in the bottom will do. Us ecoal or a good sack of wood putting the castings into the fire once a good hot bed has built up and continue feeding the fire then leave covered to cool overnight. A torch can work for small areas or small section projecting parts of a casting but doing the lot is easier.

You need to get it to red hot which is in the region of 870-900 deg C.

Another option when using small taps is to put the tap wrench onto the round part of the shank, if things get tight the wrench will slip before the tap breaks.

 

[GreenTwin]

I leave my gray iron castings in the sand overnight, and let them cool as slow as possible (as Jason mentions about slow cooling of iron).
Using the correct amount of ferrosilicon during the casting process is also important to avoid the chill spots.
Chilled iron has the same characteristics as tool steel, but luckily it can be avoided if you pay attention when castings parts.

I know of one foundry person who uses the correct amount of ferrosilicon, but still uses a post-casting annealing process, just to be sure there are no chilled spots.
The type of scrap iron that is melted can also affect the casting machinability.
I have heard that using ductile iron scrap may cause hard spots in the castings, but I suspect it is more of a section of the casting cooling too fast, and not allowing the graphite to be distributed in the casting.
.

 

[Steamchick]

I use 4-jaw pin chucks to hold sub-1/8in diameter taps. The body of the pin chuck is then twiddle between first finger and thumb and you can be very delicate when tapping, with a lot of feel. It doesn't need brute torque for small taps, but a lot of control so you DO NOT BEND the tap, which will snap at the first hint of bending. T-type taps are very hard to control without bending the tap.
K2

 

[Sarah]

Thank you gents for your comments regarding annealing the castings. I have a friend with a wood burning stove which I can use. When I do the next castings I'll have to volunteer to clear the ashes out next morning Out of interest how would I be able to measure the temperature the stove gets to? Would it just be the castings getting red hot?