First mini lathe project, oscillating steam engine.

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Ross:
Today a little brass rod I ordered arrived,

It was for the trunion bolt, (I might get some hex for that) and the crank pin.

I started on the crank pin and I would've got it finished, but the god old tap and die set let me down once again. Before I threw it all half way across the UK I stopped, and put the small useless tools in the bin where they belong! I had some success with using the bigger sizes of that set, M8 and M6 etc.. But the smaller ones are not machined properly, if at all.

Anyway... Onto the crank pin.

I started by facing the brass then turning the diameter to 3.5 mm. From there I worked my Down with small cuts until the hole in the Conrod of the piston was a good fit, not sloppy but enough play so it just "dangles"

Facing:

Testing with the piston:

I then proceeded to take part of the pin down to 3mm so it can be threaded with the die.

I got the die out and it wouldn't start on the pin. The exact problem I was hiving with the taps, I applied a bit more pressure while turning. And then the die just slipped off the end leaving a nice trail of marks behind it.

Being the perfectionist that I am, tided up the end and extended the 3mm diameter a little bit. I'll get a 3mm die from a good tool shop next to my college and thread it on Thursday.

DaveH:
Hi Ross,

Coming along nicely :thumbup: :clap:

Sometimes it helps to put a small chamfer on the part you are going to die.

Also many dies have a "right side" to start the thread

Looking good Ross
:beer:
DaveH

andyf:
Looking good, Ross :thumbup:

Like DaveH says, a chamfer can help the die to get started. And the side of the die which should be facing the work is usually the side with the size etc etched on.

If it's a split die, open it up a bit with the conical middle screw in your die stock or die holder before you do up the screws on either side.

Another way to get it going is to put a bit of M3 rod in your tailstock drill chuck, run the die on to it, butt the M3 rod up against your embryo screw, and run the die across the join with a diestock until it has cut a turn or two with the M3 thread pushing it forward. If you have no tailstock die holder just carry on with the die stock, but if you have a tailstock die holder change over to it, because it will be better at keeping the die aligned.

Andy

Andy

saw:
Remember Ross the diameter must be 2.94 mm for a 3mm die :coffee:

Ross:
I had a go at threading the brass pin last night but I failed, so I gave up. I re made the pin tonight in bras again and it just wouldn't work for me, the threads just seemed to be crushed. I turned the diameter to 3.00mm and by the time the die had done its work it was a mess and down to 2.60mm.

I decided that maybe the brass was too soft for this size of die, so I tired aluminium instead.
I remade the pin once again, and it threaded beautifully.

I parted the pin from the Ali rod and faced up to length its now attached to the crank:

I had to make adjustments the piston as it did not have enough clearance for a full turn of the crank so a few mm was taken off.

I want to try and Sort the base out this weekend. Do you guys think it would good chamfered or a few steps added to it for decoration?

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