Kondia FV-1 Head disassembly

[PixMan]

That should work, it's a fairly high tensile strength though I did find this Australian one:

http://www.ssm.co.nz/sitefiles/4140.pdf

Probably uber expensive stuff there, if you could even find it.

[Mayhem]

What it the best approach?

1. large enough ø to mill a decent hex and turn the rest down to ø13mm

2. buy the smallest ø that I can find to thread and then either pin and/or weld a larger ø piece from which the hex can be milled?

Option 1 seems wasteful but I have heard of people having issues with pinned drawbars. I know 1018 welds fine but I'm not sure about 4140

[DaveH]

This is how I did mine.

Pressed the bar into the hex bar (the nut). 
Drill a hole thro' the hex nut and the bar c/s the hole both sides.
Press a suitable pin thro' the hole then bash the crap out of it to fill the c/s.
File it finish with some emery cloth. (All 6 faces)
Place it in the lathe to true up the hex ends and a nice chamfer on the hex nut.
 
DaveH

[DaveH]

Some drill and tap the Hex nut and screw the bar in. Some use Loctite on the thread and pin it.
 
DaveH

[Roadracer_Al]

You could also braze the hex on the bar.

[f350ca]

4140 welds fine with a low hydrogen rod such as 70018 or mig.

[Highpower]

700,000 PSI electrodes? Where do you get those from Greg?   

 

[f350ca]

OOPS

[Highpower]

Just don't call me Steve.... 

[Mayhem]

Just read the data sheet that Ken linked to above and obviously missed this the first time around:

Quote:Welding:
Parts should be welded in the hardened and tempered condition. Strength properties of the joint will not be the same as the base metal.
Preheat 300-400ºC. Temper after welding to about 35-50ºC below the recommended tempering temperature.
Filler metal: - FOX CM2-KB electrodes or CM2-IGwire.
For advice in connection with difficult welding, please consult our engineers.

Just called them and got some prices:

1/2" Round (ground) = $7.50 per meter
13mm Round = $6.50 per meter
19mm Hex = $25.00 per meter

I'm thinking of using 1/2" ground for all 3 drawbars and then turning down the diameter for a M12 thread.  The tolerance on the ground bar should be good for the 1/2-12 and 1/2-13 drawbars.  I would then use the hex bar for the wrench end.

They have a minimum $50.00 order, so I may pick up some 25mm round stock as well.  Given that I am going to probably have more use for round stock than hex, having some 25mm stock might be a better choice.  The also have off cuts...