Hi all
I am the proud owner of a used Jet 1236 lathe which has a pair of cracks in the cast iron bed, just ahead of the head. The cracks start underneath the bed and extend vertically around an inch. I imagine that someone must have stacked something heavy on the lathe?
Anyway, I’m wondering about the best method of repair. Take the bed to a machine shop to be welded? brazed? Other method?
Thanks in advance for the advice.
davidb
Replies
Before opting for an expensive repair why not try something simple like JB Weld. I used it to repair a cracked cast iron radiator and it has held up marvelously for the last 4 years.
Hmm, I guess I wouldn't have much to lose. I wonder if it would hold up under vibration, etc...davidb
I wonder if it would hold up under vibration, etc...
It should -- it's been used to repair cracks in engine blocks and manifolds. Beyond that, you can sand it after it cures to achieve a smooth surface.
"It should -- it's been used to repair cracks in engine blocks and manifolds. Beyond that, you can sand it after it cures to achieve a smooth surface."I'm wondering whether you get the JB inside the crack or if it is applied like a patch to the outside of the crack?Thanks,
davidb
I'm wondering whether you get the JB inside the crack or if it is applied like a patch to the outside of the crack?
If you heat it first, before it cures (you've only got about 10 minutes till that happens) it will become a thick, viscous liquid that should flow into the crack. I know this because the radiator I patched with it was hot the first time I tried it :-) You may have to apply several smaller amounts depending on how deep and wide the crack is.
"Hmm, I guess I wouldn't have much to lose."
One thing to consider: Once you've contaminated the crack with epoxy, it will be all but impossible to do a later subsequent weld repair if the epoxy doesn't work out. I'd at least show it to someone who has welding capability first.
-Steve
Yeah Steve, I believe I'll call today to get a quote on the weld. If it is outrageous, I may still try the JB Weld route.
David,
JB Weld wouldn't last a second in that type of stressful application. That bed would need to be professionally welded and precision surface ground. JB Weld is nothing more than a tube of glue. I have even seen good welds break.
No worries. I took it to an experienced welder this morning. I should have it back tomorrow all repaired. He said that there are no guarantees of course, but it looked like it would be a pretty easy fix.
Speaking of cast iron, the welder has a cast iron grid table which must be at least 8' x 15', around 3" thick. No idea how much it must weigh. My lathe bed just took up a tiny corner of it.
davidb
Excellent. That should take care of it, the JB Weld would have failed 100%.
Put some pics... before and after, would have been informative to the rookies. There's at least half a dozen ways to weld, braze or silver braze cast. See if you can get a detailed explanation of his process, type of welder and his filler metal. There's a lot of misconceptions on welding cast iron. Newer filler metals do not require the preheating of yesterday. You can get several welders toghether and all most will have a workable method albeit different from each other.
How much is he charging?
JB Weld is useless on a crack. There's several options we typically use. We've stick welded cast iron with stainless rod or special cast iron rod. You have to grind out a fillet to fill with the weld. Many say you need to preheat the iron and such. Not true. At least not true in many cases. You have to learn the rules before you can break them.
Brazing is another option. Again a fillet is ground for the filler metal. Lower heat so less likely to warp. Looks like a repair with the brass colored filler metal.
Silver brazing is another option. Very fluid and can flow between the cracks. The perfect method for repairing cracks on planes. Yields a pretty invisible repair. Most welding shops don't do this kind of work. Common technique for jewelers and specialized Metalsmiths.
Have several places give quotes and ask to see some cast repairs. Good chance of heat distortion if not done properly but it's doable. Shouldn't cost too much.
Not really a question for the woodworking forums as it's not a topic generally known by most woodworkers. A targeted search on google would give much better results.
Interesting how questions about semirelated topics and how people search for answers. If one droped a table saw on ones foot how many folks would go to a woodworking forum or a medical forum for advice. A doctor would be the correct answer.
Edited 6/30/2008 10:18 am ET by RickL
"Not really a question for the woodworking forums as it's not a topic generally known by most woodworkers. A targeted search on google would give much better results."But that's part of the reason to ask on this forum Rick. We can read the responses and learn more about our tools and how to care for them. I'm sure I'm not the first guy to wonder about how to fix a crack in a cast iron machine. BTW, thanks for the advice about the cast iron repair. We do have a machine shop just around the corner from work. I will try them tis morning.Thanks,
davidb
"But that's part of the reason to ask on this forum Rick. We can read the responses and learn more about our tools and how to care for them. I'm sure I'm not the first guy to wonder about how to fix a crack in a cast iron machine."
I have mixed feelings on this one. Most folks can't tell the bad advice from the good advice. When I first started on the web years ago I asked a few questions. The answers were so bad I learned how to find the answers without having to ask anyone. There's really no new questions ,only new people asking the same old questions.
I would try several sources including a couple of welding and machine shops and see who's answers match. Not always a guarantee.
I
I am with Rick on the suggestion of getting it welded, but then if you want to do more, you could epoxy something which bridges the crack on the underside after that. I would bet the the previous owner probably turned some pretty bad out of balance bowl blanks that was more than that lathe was meant to turn. Those legs just are not designed to handle the torsion involved there.
JB Weld is great stuff. I've used it for patching a hole punched in a garden tractor engine block (threw a rod) and patching worn boiler spreader stoker feeders. But I would be worried about using it for structural strength. From what I've read JB is only about 15% the tensile strength of gray cast. Brazing or welding is a tricky business on cast but it can be done with good success by a good experienced welder. Preheating and controlled cool down is necessary.
Work Safe, Count to 10 when your done for the day !!
Bruce S.
You might want to check on the cost of a replacement part from Jet. You will have a reference point to determine if the welding or other method is a cost effective way to repair it.
They want $250 for a new bed from Jet. Even if I have to go that way, it will still be cheaper than if I'd bought the lathe new, although it does start to get close. I will pursue the cheaper options first, for sure.
davidb
One of the tricks for a crack in glass or anything that is stressed is to drill a small hole at the end of the current crack to stop it from continuing to spread. I would think that this would apply to cast iron as well. The drilled hole is very small, 1/16" would do, and doesn't allow the crack to continue. If the crack is only an inch long I would think that a reinforcing 1/4" plate could be added to the back with machine screws drilled and tapped into the bed across the cracks. JB Weld could be put into the warmed crack as others have suggested also. Masking tape across the applied JB Weld will keep it in position until it hardens. Clean the crack with acetone or something similar to remove any oil before using the JB Weld. I hope these suggestions help.
Good Luck!
Bruce
Thanks guys. I did call a few welding shops today. Two of them didn't want to touch it. One guy said that he could do it but the bed may end up misaligned. I'm going to try to bring the bed to him tomorrow to get a quote.
If he is doubtful, I was thinking about using some sort of mechanical fastener, such as a draw bolt anchored on either side of the crack.
Thanks for the replies and ideas.
davidb
About 45 years ago I dropped my hand plane and the toe broke off at the throat. I took it to my machine shop class at the high school and brazed the toe back on to the plane body. I put the plane in a tool room shaper and began to remove metal to true up the plane sole. The area where I heated the cast iron changed in temper and became hard which made machining difficult. There was also warping of the surfaces during cooling. I still use this plane today and the brass braze has not cracked.
After high school graduation, I began an apprenticeship at the Warner & Swasey Co. They made turret lathes along with other machine tools. Getting the tail stock to align with the head stock at any point along the ways was a big concern. You need good alignment if you drill holes from the tail stock or support long work with your tail stock. Heat warpage and alignment can be a big concern if the cracks are large. An experienced welder who knows what he/she is doing is important and might be worth paying a little extra to get the repair done to avoid alignment problems.
The preferred way to repairs planes and such is silver brazing which is virtually an invisible repair. It's a method more known to jewery makers, Metalsmiths and tooling makers. It the same technique used to put carbide tips on sawblades and router bits. When I wored as a Metalsmith we used silver brazing to make architectural and furniture hardware.
Thanks for the information.
RickL wrote:
"I have mixed feelings on this one. Most folks can't tell the bad advice from the good advice. When I first started on the web years ago I asked a few questions. The answers were so bad I learned how to find the answers without having to ask anyone. There's really no new questions ,only new people asking the same old questions.
I would try several sources including a couple of welding and machine shops and see who's answers match. Not always a guarantee."
Good advice!
You have to remember that on this forum you're asking questions of people who, by and large, don't have any more idea than you do about what to do.That doesn't stop them from answering, however.
Part of getting the right answer is knowing where to ask, as well as who to ask.
A better approach would be to find people who have actually repaired cracks in cast iron. I would suggest the Old Woodworking Machines Forum- http://www.owwm.org. Do a search for "cast iron repair" and you'll find lots of info, based on what people have actually done. Then you can make your decision on what to do.
I think you're on the right track by asking around at the welding and machine shops.
Good luck with it, and let us know what you decide.
Rick W
Will do!
I have access to a pretty complete welding and metal fab shop at work, and several very good certified welders who I am friends with. Personally I wouldn't have thought of welding it. It is very difficult to weld cast iron, and not have a lot of residual stress left in the casting that just becomes a weak point for it to crack at next time. You probably have it welded now, but the alternative would have been to install a plate on the bottom of the bed with screws, super glue.
The casting broke because the tension load at the bottom of the casting exceeded the tensile strength of the casting at the very bottom of the casting.
To close the crack and stabilize it, while increasing the tensile strength at the bottom of bed, I would have:
Clamped the bed upside down, to the top of my table saw, to use the saw as a known flat surface;
smoothed up the bottom of the casting with a belt sander, or my straight line air sander to get a good surface to glue to;
cut a piece of 1/8-inch steel to fit, and clamped it into place;
drilled eight holes, sized for clearance holes for a tap, through the plate and into the bottom of the bed.
unclamped the plate, and drilled the holes out for bolt clearance, and counter sunk them for flathead screws;
tapped the holes in the bed;
checked to make sure everything will bolt together;
blown off everything with brake cleaner to make sure the super glue has clean surfaces to adhere to;
applied low viscosity super glue to the crack and the bottom of the bed where the patch will go, and bolted the whole thing together.
The repaired bed would then be stronger than the original casting.
Alright guys,
The welder dropped the bed off (he was in the neighborhood, so brought it by my work). He was very happy with the repair and didn't feel that there was any significant warping. He concurred that the crack was probably caused by the bed's feet not sitting flush on the legs. He added some extra material on the inside of the bed I'll try to post a photo ASAP.
The repair cost $80 which seems pretty fair.
davidb
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