Cast iron bed crack - options

[DonInReno]

I picked up a  damaged Juki lu-562 as a project...keep in mind this is a project machine and not a mission critical money maker.

It seems to have been squished under something heavy and the underside of the bed has a crack running the entire width of the bed, but not completely through to the top.  The nose of the bed is bent upward about 1/8", which not surprisingly, has the shafts half bound up.  On the plus side the shafts do not appear to be bent since rotating them by hand produces even resistance.

Its easy to argue the most proper fix is replacing the bed and or entire head from a donor machine.  Are beds and upper portions matched and/or machined as a unit?  Im sure there are some damaged upper heads with intact beds that would be free or nearly so.  Even if they are mated early in the manufacturing process it doesn't seem outrageously complicated to machine off a little to shrink the neck, or cut a shim to raise it.

Along the same lines are all 562's the same?  How about 563's - do they share most parts with the 562 other than the larger hook, or have a number of other bits been upgraded?  

The crack doesn't cross any bearing bosses or other spots that might omit welding or brazing as options.  Proper welding techniques on cast iron are well documented by all the big venders - a lot of preheat, nickel rods, long drawn out post heat slowly bringing the temperature down over many hours.  I've never heard if arc or TIG produces better odds of success?

Brazing options seem to be either lower strength silicone bronze (doable with a dc TIG, which I have), or much stronger aluminum bronze (requires AC TIG similar to what's required for aluminum welding).  I'm not a huge fan of brazing since it has to be built up more than the original iron and will always look like a repair every time the head is tilted back for oiling or cleaning.

 

[Gunnarsson]

1 hour ago, DonInReno said:

Proper welding techniques on cast iron are well documented by all the big venders - a lot of preheat, nickel rods, long drawn out post heat slowly bringing the temperature down over many hours.  I've never heard if arc or TIG produces better odds of success?

Brazing options seem to be either lower strength silicone bronze (doable with a dc TIG, which I have), or much stronger aluminum bronze (requires AC TIG similar to what's required for aluminum welding).  I'm not a huge fan of brazing since it has to be built up more than the original iron and will always look like a repair every time the head is tilted back for oiling or cleaning.

A proper brazed repair should normally have a higher breaking strength than cast iron, so it can be superior in strength to both the original item and a welded repair. And if you use the proper method and grind a groove where the crack was and braze it up nothing prevents you from grinding any protruding material and painting it to make the repair more or less obvious. (All repairs require stop drilling the cracks and grinding a groove, really - both welding and brazing.)

You did not mention the brazing method using an oxygen/acetylene torch, with the proper brazing bronze. Unlike TIG, you can use the torch to preheat the area before brazing. 
Actually, it could be O/A welded too - in some cases it's still the best method. It does not use a nickel filler like when arc welding cast iron, rather you use actual cast iron rods for filler (such as Kastweld 111). The upside is that after the repair you still have a 100% cast iron item, that can be drilled, tapped and machined as before if the proper slow cooldown was used. The downside? The part needs to be stripped down completely. Complicated shape items such as cast iron cylinderheads are welded using this method, but those complicated shaped require ALOT of preheat - we're talking the entire head being bright red. After that the machined surfaces need to be re-machined, but your crack looks like it's in a "better" area requiring way less preheat.

I'd go for brazing, partly because it's the lower temperature option. But the warp in the bed worries me a bit, the repair would probably pull it a bit straighter again but exactly how much is hard to know. And if you try to force it back, even after stop drilling and grooving the crack out, it might be enough to break the bed completely off. On the other hand, then you could bolt the halves together and stop worrying about welding or brazing.

[DonInReno]

I wonder if it's more prudent to cut through the bed completely or just grind until the crack stops and leave the top surface intact?  Hmm...

[Uwe]

You could probably simply ignore the crack, too. If the machine sews fine, just put it in a proper, very strong table top and use it. That tiny crack at the 10" mark on your ruler should not affect functionality. Any hot welding fix attempts may just make matters worse. Properly supporting the machine may be all you need to do. Most tables only support the machine at the corners, but you can machine an edge that supports the machine along the "lip" instead of just the corners.

The most likely cause of that crack is a bowing table top that only supported the machine at the very left and right edge. Many cheap industrial table tops are simply too weak to support the sewing machine without bowing in the middle. That big hole in the middle weakens the table top considerably. Especially particle board table tops are only straight for short while after you cut a big hole in them and drop 70 lbs of weight on them repeatedly.  

If the machine is supported only at the ends and you let it drop down often enough, a metal fatigue crack will develop in the unsupported middle on the underside. Fixing the crack without fixing the table top will only buy you a little time.

Putting the machine in a proper, very sturdy table top, may keep the crack from getting worse and if the machine sews fine as it is, there may be no need to "fix" the crack. 

I had a machine with a similar crack in the bottom ridge that worked just fine. I built a new, straight, and sturdy  table top for it (two layers of 3/4" plywood glued and screwed together). It's been performing well in a production environment going on two years now.

 

Edited January 24, 2018 by Uwe

[CowboyBob]

I've welded a lot of beds over the years & on this one it would be best to v-grind it for more contact & either braze or heat & I've used nickle rod,brazing is the best,with a torch.

[brmax]

I am a bit curious and would really like to see a few more photos of that area and particularly the bottom generally.  My thoughts honestly are that crack if pulled together, would not result in a flat surface on top. I would discuss more and figure a way to relieve the stress it has, if any more! 

Good day

Floyd

[480volt]

Is this worth repairing? LU 562s and similar are not difficult to find. You could go to the trouble to weld/braze it and the shafts could still bind.

[GPaudler]

I've had good luck using silicon bronze and TIG brazing cast iron but you might consider drilling, tapping and epoxying a steel doubler on the underside, if there's room. It would save disassembly and repainting after burning-off the paint.

[Gregg From Keystone Sewing]

22 hours ago, CowboyBob said:

I've welded a lot of beds over the years & on this one it would be best to v-grind it for more contact & either braze or heat & I've used nickle rod,brazing is the best,with a torch.

This is old school, and how we do it, too!  Lot's of them.  Many of them in this location in the bed as well.  Clear sign of a drop.  The machine will never break on it's own unless it's a stretch and the weld gives out.  Maybe some did break the frame under normal use, but I don't know.  No two machines are the same.  

Edited January 24, 2018 by Gregg From Keystone Sewing

[DonInReno]

I feel much better since you guys have some track records fixing this kind of crack! I did pick up a $10 thrift store  machine to break and practice on. Lol

In a kitchen remodel we removed enough maple butcher block for my three machines - a nice stiff table seems to add something intangible.  Having said that, I'm always amazed at how durable high pressure laminate (like Formica) is on even a sagging table.

 

[DonInReno]

Well I finally had a few hours to play around with the machine and discovered the input shaft was a little bent, but on a happier note the binding in the lower end completely goes away when the bed is clamped halfway to being flat so I'm optimistic that grinding out the crack and brazing it will solve all the lower end problems :-)

Now about the input shaft - if you are squeamish it's better to stop reading now, because what I did to fix it is a little ugly!  I'm guessing whatever happened to crack the bed also put enough pressure on the hand wheel to bend the shaft.  The 562 has a beefy enough hand wheel that it wasn't damaged other than a newish looking scuff on the rim.

Again keep in mind the Juki isn't being sold to anyone and I'm not suggesting the following as a best practice.  I figured if the hand wheel is tough enough to bend the shaft in one direction it will most likely survive a tweak in the other to straighten things out.  It also seemed that it could be done in a way that doesn't put as much pressure on the rear bearing as the original damage did.

I held a dial indicator up to the rim to both accurately tell how much it's out and where the bend is.  Then two screws holding the wheel to the shaft were loosened and it was backed off the rear bearing 1/16" or so. The screws were tightened little more than finger tight so any impact wouldn't get fully transmitted to the bearing or down the shaft.  A block of hard maple was cut to be a firm fit between the hand wheel rim and the head.  Another chunk of hard maple was held to the top and gently tapped with a rather large hammer.  At least for me it's easier to judge a gentle tap with a big one rather than a big hit with a small hammer.  

After a hit the wedge block was removed and the rim checked for movement....after three or four increasingly stiff taps a little movement showed up - maybe only .002", but it moved.  I kept tapping with about the same force, checking the movement each time, until the hand wheel rim was within .005" runout - close enough that it can't be easily felt or noticed.

Spinning the wheel on the shaft it seems none the worse for wear. I also wasn't going to be heartbroken if it didn't survive since a replacement pulley was found in the return/scratch and dent rack at the local Summit Racing wearhouse.  For $30 this aftermarket power steering pulley feels good in my hand, is clear powder coated, and provides about a 60% speed reduction.  I'll press in a steal sleeve, drill it out to shaft diameter and tap holes for two new set screws.

Now the biggest decision is what color and texture to repaint everything.  Hammered Juki green like the original finish?  A high gloss cream or off white color looks good to me....that's a long weekend of sanding and filling the body just to prep it....Idonno.  It looks like some resellers on eBay are mixing Rustoleum hammered silver and a little black - doesn't look bad, but reminds me of a drill press. Lol

Edited January 28, 2018 by DonInReno

[DonInReno]

I’m getting closer to brazing the crack.  

The bed was stripped fairly easily. The only hang up was a single set screw in the stitch length gizmo and holy cats was it tight.  Giving a good-fitting screw driver bit a hammer smack didn’t do anything to loosen it up.  Then the housing the set screw was in was heated to about 200 degrees, but nothing.  Then it was heated till the oil started to smoke and nothing.  Another smack to the screwdriver bit and it finally unscrewed. 

Then the lower and upper were separated, paint on the bed was stripped and the crack is being ground out with a carbide burr.  The closeup shows how the crack shows up as a fairly dark line - you just have to keep grinding and chasing the line until down below the crack.  Luckily it doesn’t go clear through the bed, but about 2/3 to 3/4 the way through.   I still have a bit more grinding, but a good quality carbide burr seems to make this job much easier.

thats all for now...

[CowboyBob]

Here's a before & after,we used electric arc w/a nickle rod.

welded Adler.pdf

[Pintodeluxe]

As far as paint color... Rustoleum Hammered Rosemary is a dead ringer for the factory LU-562 and LU-563 color.  I found it in stock at my local Home Depot, but it can be ordered online as well.

Edited October 24, 2018 by Pintodeluxe

[SARK9]

Alas, the hammered rosemary seems to have been discontinued. There may yet be odd cans on high shelves that have not been sold here and there, but none of the Rust-oleum sites online show this as a current color offering. If there is any retail stock remaining, I certainly can't find it.

-DC

. 

[DonInReno]

 

On 10/24/2018 at 10:46 AM, Pintodeluxe said:

far as paint color... Rustoleum Hammered Rosemary is a dead ringer for the factory LU-562 and LU-563 color.  

I’ll definitely keep my eyes open for that color!

 

On 10/24/2018 at 10:09 AM, CowboyBob said:

Here's a before & after,we used electric arc w/a nickle rod.

welded Adler.pdf

Wow that was quite a break!  Seeing some of the machines you and other sewing outfits have patched back together gave me the somewhat misguided confidence to fix the crack in this one!  By the time I bought the carbide burr, bronze rod, welding blanket, paint stripper, 6 colors of paint, and all the hours reading up and practicing it would have been cheaper just to toss it in the spare parts bin and buy another!  That reminds me to stop by the metal yard and buy some angle to keep it lined up during brazing. Lol

[chrisash]

Probably very nieve but could you not put some baces screwed into the clear sides of the split on either side, if heated before fitted they would shrink and tighten when at room temp

If one end fixed before heating you can measure the expansion prior to fitting to be able to close the crack

Maybe a silly solution but seen it done before on other equipment

Edited October 26, 2018 by chrisash

[DonInReno]

I’m not sure if anyone has an easy crack detection dye or method, but after the visible cracks were gone I was sure the cracks continue but are very fine....

Reading up on crack detection the systems that use strong magnets and fine iron powder got me to thinking and a magnetic base off a dial indicator base seemed to work really well clamped on the other side of the bed from where the grinding was taking place.  With the two poles on either side of the crack the crack became the divide and iron fines highlighted    It seemed to highlight cracks another 1/16” into the iron from what could be seen without the magnet. I’m more confident I’ve ground down far enough - looking forward to patching it up tomorrow.

[DonInReno]

7 hours ago, chrisash said:

Probably very nieve but could you not put some baces screwed into the clear sides of the split on either side, if heated before fitted they would shrink and tighten when at room temp

If one end fixed before heating you can measure the expansion prior to fitting to be able to close the crack

Maybe a silly solution but seen it done before on other equipment

 I’m sure the machine could have had a brace of one kind or another and worked fine, although it would have always bugged me.   I’ve been enjoying welding and machinist videos lately, especially the cast iron stuff, and for the most part I’m hoping to get somewhat proficient at cast iron repairs since it pops up again and again in old equipment of all kinds.  Eventually I’d like to weld some cast iron with nickel rod, but for now I’m focused on tig and gas brazing.

[carlcarl]

Hello there,

 I’m a newbie in sewing machine world but I’m not in welding world.

i don’t know what you have as far as welding equipment but there is a GMAW wire

you should seriously consider

Crown Alloys 44-30 mig wire

It’s not cheap at 70-80 per 2lbs spool, but it’s going to be a more forgiving than any GTAW approach where pre and post heat are critical, and you get a weld that is rather difficult to grind or clean up once your done.

 I’d still preheat (I bought a used gas bbq just to use as a preheater!) 44-30 can be filed or ground if you want to clean it post weld.

I’m also a fan of brazing cast iron, but I haven’t done any of that since I bought a spool of the 44-30.  

Best of luck

Carl

 

[jimi]

Hi Don, I have been doing NDT or as you call it crack detection work for the past few years and to detect a little better the cracks you normally use a white contrast paint before applying the black particles mixed with kerosene , this way they are free to move around to the crack. you normally do it without contrast paint when it is hot, then you use what they call a pear to sprinkle the powder on and this is red to contrast with the dark metal background (the particles are very fine). Before they used liquid penetrants like you see today, they would apply oil, let it penetrate a while then clean the top surface only lightly to get rid of the oil on the surface and then apply chalk powder. if any dark areas appeared that would be a sign of the chalk absorbing the oil from a crack. If you are going to be doing this often i would look for a can of dye penetrant, 1 of cleaner and 1 of developer this way you will find very fine cracks as long as you execute it properly. If one day you do it, let me know. If you keep doing your magnet method, move them around as the cracks could be orientated at a different angle to the magnetic field you are applying (normally 90º to the first position). Hope this helps, Regards jimi.

[DonInReno]

On 10/26/2018 at 2:13 PM, chrisash said:

Probably very nieve but could you not put some baces screwed into the clear sides of the split on either side...

I ran into something unexpected that relates back to your question.  After grinding out most of the crack and clamping it to some thick pieces of 4” angle as the slight bend straightened the original crack in the web on either side closed up before the bed straightened completely - it was only about half way to straight.  About .040” had to be removed - the webs were stretched a little before they gave out.  

 

On 10/27/2018 at 3:18 AM, jimi said:

Hi Don, I have been doing NDT or as you call it crack detection work for the past few years and to detect a little better the cracks you normally use a white contrast paint before applying the black particles mixed with kerosene , this way they are free to move around to the crack. you normally do it without contrast paint when it is hot, then you use what they call a pear to sprinkle the powder on and this is red to contrast with the dark metal background (the particles are very fine). Before they used liquid penetrants like you see today, they would apply oil, let it penetrate a while then clean the top surface only lightly to get rid of the oil on the surface and then apply chalk powder. if any dark areas appeared that would be a sign of the chalk absorbing the oil from a crack. If you are going to be doing this often i would look for a can of dye penetrant, 1 of cleaner and 1 of developer this way you will find very fine cracks as long as you execute it properly. If one day you do it, let me know. If you keep doing your magnet method, move them around as the cracks could be orientated at a different angle to the magnetic field you are applying (normally 90º to the first position). Hope this helps, Regards jimi.

That’s all useful information!  In fact this morning just as I was about to start preheating the bed prior to brazing I noticed a faint line that wasn’t there the night before - apparently it was oil that had migrated down into the crack and some dust had collected on it overnight and in daylight it really stood out.  I ground down another 1/16” to 1/8” to remove what was obviously more cracked material.  

The old advice to go slightly past the point where the crack stops and drill a hole to prevent further cracking makes sense to me now - the crack extends further into the material than can be seen by naked eye.  I’ll almost bet the bed on my machine has micro cracks clear through it - if not from the original damage, from me clamping it straight while cold.

On 10/27/2018 at 12:06 AM, carlcarl said:

 I’d still preheat (I bought a used gas bbq just to use as a preheater!) 44-30 can be filed or ground if you want to clean it post weld.

I’m also a fan of brazing cast iron, but I haven’t done any of that since I bought a spool of the 44-30.  

Best of luck

Carl

 

After brazing this bed I’m definitely going to look into welding the next one.  I have a cheap inverter dc tig setup and will probably upgrade to another TIG.  It’s funny how the cost of nickel TIG wire is definitely less than the amount of gas I used today.

I was out of propane for preheat and the #4 gas tip really took a long time and probably wasn’t large enough for the deep grove on the three sided inside corner (the pic showed the spot when I first started grinding, but the grove ended up being almost the entire thickeness of the bed and undercut the leg quite a bit.  I was about to grind it out and TIG braze it while everything was still hot but the batteries in my auto dark helmet were weak enough to flash me so I said screw it, wrapped everything up and came inside. Lol

For preheat I’ve always used a propane weed burner and have a couple of fiberglass welding blankets to wrap and conserve heat for post heat but a dedicated gas bbq would be nice especially to burn off oil and paint - I’ll keep an eye out for one! 

 

[brmax]

It looks and from the conversation, the project is moving right along. Good work!

In some other future task like that, especially cleaned up as that is. I found great use from a typical oven. They have seriously helped me in cast welding items that fit. 

Many have a clean cycle, it gets a nice hi temp good for preheat. Along with another application for after weld stabilizing with a slow cool down.

These are also great welding rod, keep dry/ heaters also. Just as you mentioned the bbq pits for pre heat, great point!

 

Good day

Floyd

[LederMaschinist]

 

On 10/26/2018 at 11:38 AM, DonInReno said:

That reminds me to stop by the metal yard and buy some angle to keep it lined up during brazing. Lol

It sure looks like you know what you're doing, but make sure the angle is dead straight before you use it to align the bed.  The tolerances the mills use for straightness are nowhere near straight enough for this project.  That doesn't mean they aren't straight, it just means they might not be straight enough.

[DonInReno]

On 10/28/2018 at 9:07 PM, brmax said:

In some other future task like that, especially cleaned up as that is. I found great use from a typical oven. They have seriously helped me in cast welding items that fit. 

Thanks Floyd.  I’ve been interested in an oven for powder coating, but more uses keep popping up.

 

18 minutes ago, LederMaschinist said:

...make sure the angle is dead straight before you use it to align the bed.  The tolerances the mills use for straightness are nowhere near straight enough for this project. 

Exactly - that’s a very good point.  I ended up with a few pieces that were pretty straight and the bed clamped down quite flat, which was encouraging.  However it was a rookie mistake on my part to clamp it dead flat and not allowing for shrinkage of the bronze under the bed.  This morning a quick look with a straight edge showed a few unexpected irregularities in the top of the bed.  The most obvious was due to shrinkage of the bronze - I’m thinking that can be corrected when I go back for round two to fix a few things.   The second surprise was a slight bowing of the bed essentially from the front feet of the bed on back to the area of the crack - originally I had hoped it would be nearly flat other than where the crack was.  If the bed were steel it would be easy to straighten with a torch, but I’m guessing that’s not an option with cast iron.  This second go around I’ll try to get the joint at the crack a bit flatter then lap the entire bed flat so it looks decent.