South Bend 9 Compound Condition & "weld up" fixes?

[graham-xrf]

Well - maybe "restoration" is the wrong word!
I have taken it apart with a couple of things in mind. One is to try and repair the broken-off bit of the T-Nut slot. The other is to perhaps do something about the backlash. As mentioned in another recent thread, simply securing the Acme nut with it's grub screw near halves the backlash from 0.022 to about 0.012, and even just this is enough to get it working again well enough to set doing a bigger graduated dial modification for itself, of which there are several YouTube videos that look interesting.

"Warts & All"
We know you like pictures, and on this, I need advice. This is the very same compound casting that I posted about from last October where I got excellent suggestions from @Nutfarmer , @matthewsx , @Superburban , @tq60 , @SLK001 , @Gaffer , and some amazing pics from @Ulma Doctor. After considering the approach of cutting away the broken lip entirely, and replacing with a with a bolt-on, versus attempting to weld it up, I have decided to attempt the weld, even though my weld experience is limited to welding up a trailer frame with a cheap buzz-box, long ago. This time, I have a better welder.

So here we go with a condition evaluation, with the paint stripped, and a minimal clean-up.


The strange brown color is as it was under the paint. Is that a kind of rust? I wire-brushed the break. Here is where we come to the first question(s).
Please forgive if I hesitate on these details. I have never done this before, and these are the things I think. It goes without sayinig that in the end, it gets a new paint job!

1. Before the weld, should I grind or cut on the break surface before welding? Maybe one of the little tools with my Dremel.

2. I learn that things go much better if the whole casting is pre-heated to about 300C-400C, and care taken to cool slowly. If one is grinding the break clean, is that done while it is hot?

3. I have the choice of two kinds of welding rod that would leave a repair that can be machined, or filed. Both are recommended for repairs to "cast iron", although this metal is maybe cast "semi-steel". One is 99% nickel. The other type is called ENiFe-C 55%Ni, which I understand is used for welding to cast iron, and between dissimilar metals onto cast iron. It seems to have a graphite-based coating on the rod. I will go with whatever you folk recommend.

4. How are the welds laid in? Where does one start? Is there a planned strategy? Are they "peened"? Can you overdo things, and end up work-hardening with the slag hammer?

5. For slow cooling, I am thinking a mineral wool lined box with insulated lid, filled with sandbox sand. Does the sand need to also be hot when the job is put into it?

6. Will the whole thing be "distorted" after all this, and need other treatment to the surfaces?

The Compound Condition
There is some evidence of remaining oil retention flaking scrapes. There are places where parts of it stood exposed, and maybe where chips grime got in. One mark looks like a wear ridge at first, but is in fact a mark from the edge of the gib. The surfaces either side the mark still have some flaking.

_

The underside is not pretty, but again, there are suggestions of remaining flaking. That view is being photo-bombed by a good view of the graduated dial. I get along with it OK by using one of those binocular headbands (as us older guys do), but now that I look at the image, it has me decided that it was always just too small, and hard to read.



The Acme Screw Backlash
Even as it is, if I put in the 1/4" UNC 20TPI grub screw, the backlash reduces to a more usable level. Taken apart, I see it clearly needs replacing, maybe with some better made contrivance. I can have it soldier on, while using the lathe to make another, but I have in mind to use a little mold box, and make one out of bronze loaded JB-Weld. I have seen some remarkable videos of things done to squeeze a cut plastic tube onto a Acme thread, all the while blasting away with a butane torch, then turning the remains into a good-looking nut, but here, such a plan runs into the obvious "Catch-22" of needing the lathe to turn it's own nut. I have a little video [Good Lord - the video actually turns out to have sound ] !

View attachment SB9-Compound Acme Nut2.mP4

I think the Acme nut is a bit of a disgrace! I am thinking it would not have looked like that originally. It has had a "brazing operation" on it's lower end, possibly split and "squeezed together" a bit, then brazed, as a kind of "reduce the backlash quick 'n dirty fix". In any event, there is a crack in the brazing. Also, it "rocks a bit" in the round hole in the dovetail piece until the grub screw is tightened.

_

I did attempt to put a number on the actual axial backlash. This picture is just for laughs. By far the better way is to see what it is on the graduated dial when all is assembled. Here it says 0.012".



Pitting!
The adjuster handle. It was always like that since I got it, but I was not going to sniff at it, because the whole lathe with drawers, 4-jaw chuck(s), and tooling had only taken $147 bucks. If I don't shine it up a bit, then in the face of a paint job, it will definitely lower the tone of appreciations among compound aficionados. I am just not sure how best to go about it. I don't know how to turn on spheres, it's a distraction, and this whole work was to try and get something going to make the part for XRF sensor anyway!

OK then - warts & all I said, so here it is! It is not going to stay that way! I have to wonder why it looks so much worse than most other bits on the lathe, which seem to be in better condition, and mostly lived drenched in oil.



So there we have it. Somewhat picture-heavy, a bit off-putting - I admit, but hopefully here I reap the benefits of what to do to fix it up. Regarding the compound nut, that must surely only be allowed to live long enough to turn up it's own replacement!

 

[Ulma Doctor]

the patina looking brown color is iron oxide- iron will rust in minutes unprotected

Q1: i would definitely grind out the weld area, paying special attention to the outer edges, 45° edge chamfer works best especially for joining 2 pieces.

Q2: grind while the cast iron is cold, then preheat
400°F is sufficient, but you can heat up to better than 500°C if you felt it necessary
(i usually only pre-heat to around 400°F)

Q3, personally i would braze the weldment with low fuming bronze or silicon bronze.
but, if you are gonna stick weld, i would go to the 55% Nickle rod as it will be easier to clean up post weld
the 99% rods are nice, but they are expensive and very difficult to deal with post weld- you are pretty much stuck with grinding for post op's with 99% rod

Q4: Wood ash, sand, earth, vermiculite, all would be acceptable to slow cool- a welders blanket could also be employed
the insulating material, whatever is used, doesn't need to be hot- just make sure it is not frozen

Q5: anytime we mess with heating and cooling things we get a huge chance for warpage.
the slower things are heated and cooled, the more they tend to stay straighter
when i repaired the compound on my SB11, i scraped it in afterwards
you may or may not have problems in this regard, if you stay to the lower end of the pre-heat temperature range

as far as the compound nut, i would not attempt repair when making a new one is very simple-
you'll spend a bunch of time on making repairs to a worn out nut that may be marginal with the best of repair.
i can make a nut for you if you don't have the inclination.
they can also be purchased for ebay too
on a side note, delrin can be bored and tapped slightly undersize to grasp a worn acme screw tighter
this doesn't eliminate backlash, but the felt backlash effect is lessened

if you were to find or make a rock polisher, you could easily make the handle look good as new
add some sand, glass, and/or silicon carbide and water. add a couple drops of dish soap.
let the rock polisher do the work for a day or 2


let me know, if you need a nut made
i'd be happy to make one for you

 

[graham-xrf]

if you were to find or make a rock polisher, you could easily make the handle look good as new
add some sand, glass, and/or silicon carbide and water. add a couple drops of dish soap.
let the rock polisher do the work for a day or 2


Let me know, if you need a nut made
i'd be happy to make one for you

I thank you kindly, and I would take you up on the offer, if or when my own attempts get totally screwed up!

That is a good suggestion about a tumbler polisher. If they can shiny up rocks, they can do metal.
I saw a video of a re-purposed car polisher. I mean the kind that vibrate sideways instead of a rotate buffing. They are not so good as car polishers, but if bolted to a container which is suspended over a bucket using bungee elastic cords, you can shake up stuff with various media. I think the example was to clean up a carburetter.

Are the parts of these handles held together with screw threads?

 

[benmychree]

The trick regarding welding cast iron is ending up with a machinable weld, which is far from guarenteed. If the weld is hard, unmachinable, you are screwed; I believe that the best course of repair would be the idea of machining the broken part away and securing a new steel part with screws, I have seen this done several times, and it works well.

 

[graham-xrf]

The trick regarding welding cast iron is ending up with a machinable weld, which is far from guarenteed. If the weld is hard, unmachinable, you are screwed; I believe that the best course of repair would be the idea of machining the broken part away and securing a new steel part with screws, I have seen this done several times, and it works well.

This very point is, I understand, what motivates the use of EniFe-C electrodes, also known as "55s", and also using 99%Ni. A ferro weld would pretty much guarantee to be non-machinable highly stressed variable hard zones, if you could get a fusion adhesion at all. Also, on cooling, even if slow, the part ends up stressed, and can develop cracks because cast iron has very little strength in tension.

We start with the stuff the lathes were made of, called cast semi-steel, which had less carbon and silicon. This stuff is tough, and impact resistant, though there are limits, hence the breakage, but we know there is some strength in tension. The other choice of using 99% nickel weld is the "safe" one in the sense that nickel is non-ferrous, and cannot make a phase with carbon. There is more ductility, though there are, I think, other stress issues related to expansion coefficients, but this aspect I don't know.

You could be right, and I hear you well, and also you be John, who definitely knows stuff. Part of the motivation to first give the weld a try is because my ability to get my mill out of it's crate and powered is pretty much blocked for the present because of building operations.

If this scheme messes up, and the casting remains in enough of one piece, then cutting away the T-Slot top, and making a bolt-on can perhaps be the backstop. If that transpires, there is no question that I will remember that "John told me so"!

 

[SLK001]

As for the weld, are you planning on building up the missing material with a rod? If so, do you have a gas grill (outside)? You're going to want to get the part to about 500ºF before you start. Build the weld up slowly (one layer at a time) and then close the grill and give the part about 10 minutes to stabilize, then add another layer. Repeat until you have built up enough metal to cover the missing area. Close the grill cover and let the part soak for about 30 minutes. Lower the temp about 50ºF every 30 minutes down to 200ºF, then turn off the grill and let the part cool.

 

[graham-xrf]

As for the weld, are you planning on building up the missing material with a rod? If so, do you have a gas grill (outside)? You're going to want to get the part to about 500ºF before you start. Build the weld up slowly (one layer at a time) and then close the grill and give the part about 10 minutes to stabilize, then add another layer. Repeat until you have built up enough metal to cover the missing area. Close the grill cover and let the part soak for about 30 minutes. Lower the temp about 50ºF every 30 minutes down to 200ºF, then turn off the grill and let the part cool.

A little detail.. Is this stuff done by welding on it while it is over a gas grill?

I had thought to keep it heated between weld passes using a propane torch, and then transfer it into the box of wood ash, or even put it into the woodburner, covered in wood ash, and let it take all night to cool down. I would have a thermocouple on it to keep an eye on temperature, just because I do have one, but I have heard things called "temple sticks" can be convenient. You "draw" a line with them. If the line happens because the tip melted, you know the temperature range. I have never used them yet - still looking them up!

[Edit: I might have guessed that "temple sticks" is a utterly useless search term unless you want every kind of Krishna-neo-hippy incense]!
[You have to spell it right. "Tempil Sticks". Tempilstik brand]

 

[gonzo]

would just find one on ebay and buy it. Probably not a lot of $$$

 

[682bear]

They are not expensive on ebay, but what would it cost to have it shipped to Great Britain?

IDK... I would probably attempt to repair it first, anyway, just because it might 'further my education'...

-Bear

 

[graham-xrf]

would just find one on ebay and buy it. Probably not a lot of $$$

They are available from eBay.co.uk from local sellers.
It varies a lot. £4.50 ($6.25) for one 177C (350F) in UK with free postage.

Same thing, choose a temperature from a choice of three, but you get only one stick..
Wow! £12.50 =$17.37 plus £3.50 = $4.86. That's $23.24 for one!
eBay is definitely a place you have to shop around, and read the words carefully.

On another deal, 4 x 50C sticks (that's low temperature) for $34.75 including postage..
.. which works out at $8.60 each.

Call me "HM tightwad", but I will likely just measure the temperature. Even my (eBay) digital multimeter came with a K-type thermocouple probe, and a Tempilstik or two adds up to a reasonable fraction of the whole instrument with free postage!

I know the temptation of a bolt-on repair is strong, but I think getting to grips with a heat assisted weld, and getting it back in a de-stressed condition after a controlled cool-down is an adventure I would rate as something that I would be proud of, and give me a big buzz if I get it right. Even if things go wrong, I can hardly regret trying!