I am doing something of a re-refurbishment to an old lathe... it is a Hendey Tie- Bar 12x4 lathe that I just picked up off craigslist.
The cast iron guard that goes around the bull gear was broken at some point in history. Someone has brazed it back together, but didn't get it brazed in the correct position.
20191007_120843.jpg (30.46 KiB) Viewed 1898 times
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20191007_121107.jpg (35.2 KiB) Viewed 1898 times
It needs about 20 degrees more bend, and is slightly twisted...
Would it be possible to 'bend' the brazed area, or would I need to cut it off and attempt a re-braze?
I have silicon bronze tig filler, what is the chances it would stick to what is already there?
Any advice is appreciated... I doubt I would ever find a replacement guard for a lathe that was made in 1919...
Did you do the original brazing job? The brazing material may be bendable but it depends on the alloy. If you have silicon bronze and are comfortable using it, I would probably start over. Heat that piece up until the old brazing material melts away, clean it up, and then braze it up with silicon bronze. Silicon bronze is pretty ductile so you can bend that if you need to.
Hi Bear,,,that original job looks to me like it was O/A brazed. I wouldn't know what that material would do when stress is applied to get the right angle and twist to it. You might lucky and it would break at the original area and you could clean up the goober and start over. I'm not sure if your rod would fuse to the old material braze or not. Where is coldman, he uses some wizardry to braze and would help you with a decision. Keep us posted.
I did not do the original repair... so I have no idea how it was done.
It's no good the way it is, anyway, so I may clamp the short end in a vise and get it hot with the o/a and see if it can be bent... if it breaks, well, I guess I get to try plan B then... I'm just afraid I'm gonna 'fix' it to the point of rendering it unfixable...
Don't forget, Bear....the brazed material will melt or go away before the cast does. Do like I do,,,have your grandson help..mine isn't quite tough enough to break something like that and IF it does break, HE did it.
Hi there, heat it up to the point where you melt the brazing. It'll either fall apart or be able to pulled apart. Then shape the left side over brazing material and re do in the correct position. You can use a little jig to hold it in place if necessary. I've seen people pull the drop outs out of bicycle frames this way.
Coldman wrote:Pics haven't come through to my phone on Tapatalk. I'll have a look on the pc tonight.
I'm interested in hearing your thoughts...
I realized that my pics didn't show the thickness of the casting... it looks like it is about 1/2 inch thick, but is cast with a flange on the front... it is actually between 2 and 3mm, I'm guessing, so it is a fairly thin casting.
OK so I’ve had a look. What we have here is a thin one hundred year old casting that’s been repaired a while back with an oxy brazing process.
I think you need to minimise further heating cycles as much as possible, for this reason I think you should not heat to melt away the existing braze filler. I would consider two repair options:
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1. Use a small burr to remove enough filler to cause separation of the two pieces but also enough to permit clamping into correct alignment while leaving a butter layer on both pieces. A thin piece of sheet aluminium or copper bent to the right angle to hold the pieces in position and clamp with pony clamps. TIG braze together with your silicon bronze, I think it will alloy with the existing filler ok, they’re both copper based right? Keep current down and go fast so as to avoid puddling the parent casting. If you do melt the parent casting, your silicon bronze is going to contaminate to hell and you will cuss.
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2. Use the burr or maybe a “tootsie roll” to remove filler completely and bevel (with the burr) the joint to half the thickness. Clamp together in position as above. TIG weld with EzWeld TIG Wire. Turn over and bevel the other side to half the thickness and run a bead there too. Job done.
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You can try method one first, if it goes to hell you can always clean it up and try method two.
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Completed pics please.
Coldman wrote:OK so I’ve had a look. What we have here is a thin one hundred year old casting that’s been repaired a while back with an oxy brazing process.
I think you need to minimise further heating cycles as much as possible, for this reason I think you should not heat to melt away the existing braze filler. I would consider two repair options:
.
1. Use a small burr to remove enough filler to cause separation of the two pieces but also enough to permit clamping into correct alignment while leaving a butter layer on both pieces. A thin piece of sheet aluminium or copper bent to the right angle to hold the pieces in position and clamp with pony clamps. TIG braze together with your silicon bronze, I think it will alloy with the existing filler ok, they’re both copper based right? Keep current down and go fast so as to avoid puddling the parent casting. If you do melt the parent casting, your silicon bronze is going to contaminate to hell and you will cuss.
.
2. Use the burr or maybe a “tootsie roll” to remove filler completely and bevel (with the burr) the joint to half the thickness. Clamp together in position as above. TIG weld with EzWeld TIG Wire. Turn over and bevel the other side to half the thickness and run a bead there too. Job done.
.
You can try method one first, if it goes to hell you can always clean it up and try method two.
.
Completed pics please.
Ok, method 1, then method 2 if 1 doesn't work... that sounds like a plan...
I'll study on it and try to build my confidence up. I'll post pics whether good or bad...
Put the welding/brazing tip on your oxy fuel rig. Put the part in a vide and heat up the previously deposited braze weld, reposition the piece to your desired location and re apply a little more braze filler.
682bear wrote:Well... I just ran into another snag... the bolt holes where the guard mounts are not a standard size... they are tapped 5/16-20.
I guess I'll have to make some screws before I attempt to repair the guard.
-Bear
Is it possible they're metric? 8mm is .314 and 5/16 is .3125. could be 8mmx1.00. It's not too hard to mix these up. The brand of the machine might be a clue to it's standard.
682bear wrote:Well... I just ran into another snag... the bolt holes where the guard mounts are not a standard size... they are tapped 5/16-20.
I guess I'll have to make some screws before I attempt to repair the guard.
-Bear
Is it possible they're metric? 8mm is .314 and 5/16 is .3125. could be 8mmx1.00. It's not too hard to mix these up. The brand of the machine might be a clue to it's standard.
It's a Hendey lathe... made in 1919... it's not going to be metric, although 8mmx1.25 is awfully close...
Only logical choice of threads used in that era here would be BSF or BSW ( as it's bigger than BA runs to ) & you appear to have neither ! so someone subsequently using what they had at hand for a repair has likely used metric - M8 would be 20.32 TPI so I'd try a metric bolt in them or clean them out with a metric tap - just don't admit to a machinist you used metric on lathe of this age - they get a bit up tight on these things !
Pics of the repaired guard... it turned out pretty good.
Never try to match paint by memory... I knew that I would never get a match from a rattle can, but I think I could have come closer than this if I had taken a painted piece to the store with me...
Basically your plan 1... except I Mig brazed it with silicon bronze wire... I bolted the end piece of the guard to the lathe, then positioned the guard and held it in place while I brazed it with the mig. I then removed the guard and brazed the back.
I had planned to tig braze in but it was in too awkward a position for me to get to.
