Myford ML4 headstock repair

[cheb]

How best to do this? My thoughts are to mill away the top part level with the machined clamp face at the front back to the dimple seen on the second photo and replace it with a suitably machined piece of steel drilled and tapped into the casting. It's been brazed, unsuccessfully, already. Possibly mill it into a mortice shape, the new piece having outside prongs or a U shape fitting over the corresponding milled casting.

Whether it's worth the effort is moot, but I'll learn something while I'm doing it.

 

[Pete.]

I would turn a piece of ally to fit the bore and have another go at brazing it. The ally will expand and make the bore over-sized so you should allow for that. Needs to be hotter and more thouroughly heated IMO than the first attempt. If you have the facility you could line bore it concentric with the rear bush holder then make a bronze bush for the spindle that does not need pinching up so tight that the casting breaks.

I just silver soldered a hardened teel blade carrier by clamping it up, pre-heating with a torch, tack-welding the ends with TIG and then soldering inside a small box lined with ceramic blanket. Worked a treat and didn't lose too much temper either.

 

[cheb]

Be prepared for questions and more questions, some might not be dumb.

I've a Rothernberger blow torch, MAPP gas style. Will it be big enough to braze this? Is a reasonble test trying to melt the old braze off? I've access to oxy-acetylene if not.

There's no rush, I mostly started this to get an idea of what the lathe needs and to be able to tuck it away off the workbench. Other threads will follow.

 

[Pete.]

Brazing needs more heat than silver solder but you might be able to do it if you can keep the heat in. I struggled to even silver solder effectively with my rothenberger until I started using the ceramic blanket. Now, what used to take an age to just about get to soldering temps goes flying past it and stays there.

 

[cheb]

I think it'll wait a bit then. I've a mill that I want to get going before I start on the non working forge....

 

[Porkypine]

I'd do the 1st option, cut the busted bit off level and make up a "cap" a nicer mechanical solution IMHO, I've never been a fan of those pinch type bearings Tbh

 

[RichardM]

I use old gas fire radiants to keep the heat in for brazing, but haven't tried anything as big as that casing as I've only got MAP.
I think @Brad93 has done castings before.
The one thing I would say is check the spindle to make sure it's worth going to the effort - it may need re-grinding. When you have done that and made new bearings use some shim stock on the front bolt to set the clearance and allow it to clamp on the shim stock.
If you haven't done so yet also check the condition of the crossslide and top slide nut threads - on my old ML2 they were tapped directly into the casting and I had to replace them.

 

[Brad93]

Three methods of doing that:

Flame spray.
Brazing.
Oxy-acetylene welding with Cast Iron rods.

With all methods you'd need to preheat the whole part and keep heating the part whilst brazing. The only difference is the preheat needed.
A gas barbecue a good quick method of holding part at 200° odd.

 

[Brad93]

Be prepared for questions and more questions, some might not be dumb.

I've a Rothernberger blow torch, MAPP gas style. Will it be big enough to braze this? Is a reasonble test trying to melt the old braze off? I've access to oxy-acetylene if not.

There's no rush, I mostly started this to get an idea of what the lathe needs and to be able to tuck it away off the workbench. Other threads will follow.

No chance with mapp gas.

You also need to burn the carbon off first, which can't be done without an oxidising flame.

 

[cheb]

Reading this I reckon to have a go at brazing with a mate's OA kit and it that fails then I can machine it.

 

[brightspark]

Reading this I reckon to have a go at brazing with a mate's OA kit and it that fails then I can machine it.

when you do it pack round with fire bricks or grey breeze blocks to retain the heat .and heat the whole lot up with a propane torch while your using the oxyacet torch and it will work well

 

[Porkypine]

I'd love to see some pics of the brazing process if you do it.. The last time I did any brazing was assembling some steel furniture prototypes in the '80s

 

[brightspark]

heres a job i did