My bandsaw table is cracked.

[Ken Pywell]

Cleaned up the table awhile back and noticed a few cracks across the surface. I'm not the original owner, so other than taking a tumble, any thoughts on what else, if any, might cause this? The edge of the table does not show any signs of trauma. This is a Delta 14" saw, #28-203.

[Ken Pywell]

Sorry about the pics. It's hard to see the cracks in a couple of them.
Ken

[Cliff Rohrabacher]

A fall could have done it so also could internal stresses.

Here is what I'd do:

Drill a 1/4 or 3/8 inch dia hole the end of the crack to relieve the stress and stop crack propogation.

I'd use a very strong magnifying lense to find the end if the crack or find a friend with a magnaflux. The drill that puppy.

If the idea of a hole in the table offends your sence of order you can drill and tap it for a 3/8 - 16 thread and countersink it to receive a bolt to sit fluch with the table. You can epoxy it in place and epocxy in the drive hole (slot or Allen hex) as well. The bolt in the hole won't interfere with the ability of the hole to stop a crack. Just don't tighten it too much or you will risk adding stress. Let the epoxy do the work of keeping it in place. Before you epoxy be sure it sits flush in the C-sink.

[Steve Clardy]

Musta been what they call a green casting. Didn't sit long enough after being casted before it was machined.

[Jeff Singleton]

I am familar with cast iron tables. As a patternmaker I have made my share of surface plates and table patterns. They are by far the easiest patterns to make. As for your cracked table a couple of things come to mind. If the trunions were knocked around it could crack the table as well as any sharp wack or if the iron meet concrete as in falling. The way tables are made is after the casting cools it should season for a year but we all know that Delta doesn't have time for that. During machining the table is held down on a Blanchard type grinder by way of being magnetized. Those are some strong magnet that can crack a table. Who knows that table could have been cracked from the factory and just now started showing up. Check and see if the crack is in line with the trunions. Could be anyone quess but you can be asured there are a lot of used 14" Delta tables floating in space and you should have no trouble finding one.

Jeff Singleton:o

[Richard Wolf]

Just something to think about, are you sure they are cracks and not deep scraches? You would not be the first person to assume a table was cracked when it really wasn't.

Richard

[Dave Fifield]

Ken,

Looks like a darned good reason why you should be allowed to go buy a nice new bandsaw......

Dave F.

[Dev Emch]

Yup, that looks like a crack.

First of all, the crack is running parallel to the mitre gage. Hmmmm. Maybe the table was tilted and forced during a tilt. Maybe during shipping from the factory?

Does the crack run through any of the underside webing or is it inline with the webing? Often the webing is egg crated to help with problems like this. Secondly you need to carefully examine all your trunions and trunion support brackets for addtional cracks. If this crack is stress related then your trunions will be O.K. If its an idiot crack, then you may have more unknown damage lurking in the bowels.

Years ago, it was once said that that you cannot weld cast iron. Well, a buddy of mine has found a couple of solutions that are incredible! First of all, there is the lock and stich method which is used to repair castings without the use of any heat. A series of holes is drilled along the crack and tapped. Special bolts are inserted and torqued down. Upon reaching a predefined torque level, these simply snap off. Then you drill and tap more holes inbetween the first holes which are now plugged with the stich bolt. Again, you fill these holes with bolts and torque them down still they snap off. Keep going until you have interlaced the bolt and hole patterns between the original iron and the lock and stich bolts. Then grind the surface smooth. This method is excellent and can be used to fix things like water jackets on large truck diesel engines. Even with high temperature, extreme cold and vibration, the repair holds up. Water tight as a drum.

The second method is called stitch welding. Here you grind a V groove up the centerline of the crack. Then, using a special rod, you weld the groove up. You weld about 1/2 inch and then stop. Allow the weld to cool down. Go to the other end of the crack and weld another 1/2 inch and stop. Let it cool back to room temperature. Then return to the first end of the crack and skip about 1/2 inch and weld another 1/2 inch bead. Let it cool. Then go to the other end and once again, skip a 1/2 inch section and then weld a second 1/2 inch bead. Allow to cool. Your weld will then be semi done when you have a dotted line of bead segments covering your excavated V-Grooved weld. Repeat the process but this time begin filling in the dotted line. Eventually you will have a weld that spans the entire crack. Now you can grind the table down. Here you need to take the table to a machine shop and have them regrind the table. This weld process is awsome. I have seen it done on an older worthington francis turbine housing about 6 feet in diameter holding back a massive amount of white water. This was a 690 HP hydroelectric system. Child's play for the hoover damn I know but nonetheless, impressive.

The welder used was a standard arc welder. Oh yes, this is extremely important! Using a ball peen hammer, peen the weld for about 30 seconds right immediately after you lift your stick from the puddle. This helps to remove resisdual stress in the part. Also the rod used is nothing like you guys have ever seen. These welding rods cost $25 dollars per pound and are worth every freakin penny! They are cronatron rods and here is the website...


http://webapp1.cronatronwelding.com/cronatron/homePage

Of course it pays to really clean the joint after grinding the intial V groove and to make sure your V groove moves a bit outside the tip of the crack on both ends. Also, its a good idea to predrill a stress relief hole at the face front of the crack even though it will be filled in later with cronatron rod material.

Hope this helps....

P.S. Stitch welding is also Skip Welding. Secondly, the two best cronacast rods are the cast iron rods called Cronacast 222 and Cronacast 235. The 235 works better in older, rusty areas like water jackets. But in your case, your going to remachine the table so you need an excellent color match and excellent machineability. Thus your most likely looking for the Cronacast 222 rod.

[Keith Outten]

They don't look like cracks to me, cracks are rarely straight. It's kind of tough to say for sure based on a photograph but from what I can see it looks like a machine or scribe mark.

A magnetic particle test may not be the prefered test if the casting has thick to thin sections in the area of interest. The change in thickness will affect the flux density. A dye penetrant test is probably the best choice and is less expensive since a Magnaflux machine or Parker Probe isn't required. The amount of bleedback from a dye penetrant test will also be a good indication of the depth of the indication.

Cracked or not I would not do any repairs, you would most likely do more damage than good. If the table is still stable make yourself an auxilliary table which will help spread the load and hopefully allow you to use the table for many more years.

[Rob Wilson]

How old is the bandsaw? You might call Delta and see if they will send you a replacement.

I just bought a used 14" delta and the belt guard did not fit. Called and they are sending me the correct replacement at no charge.

Go to their website and get the part number (you have to register, but no cost to you)

http://www.dewaltservicenet.com/ServiceNet/logon.asp

then call Customer Service (be prepared for a long wait till they answer :o)

(800) 223-7278

Good luck!

[Paul Downes]

If you are worried about the crack spreading, and I would pick up a die penetrant from the local auto or machine shop supply, then I would drill and tap a hole at the ends of the crack. (1/4 or 3/8) You can screw a bolt with permanent thread locker (loctite red) into the hole and saw it off. a careful grind and then a flat file will get the bolt down to the table surface. As a diemaker we plug holes using this method more often than I like.

[David Rose]

Cast iron *can* be brazed, if it is a crack and there is a need.

David

[Ken Pywell]

Thanks for the replies. I don't plan on doing a whole lot with it unless it becomes a problem. The saw is about about 10-15 years old and gets light use right now, anyway. I was more curious than anything else. I hadn't noticed them before so it was a little surprising. Of course they could have been there for years and I just hadn't seen them. Oh well! If it gets worse I'll have to revisit some of your suggestions. Thanks again.
Ken