Is this a crack / gouge on my table saw top and will grinding address?

[Brad Ridgway]

This is a 1999 PM66 i bought last year used... This has been there since i bought it. I'd been considering taking this up to Chris at Quality Grinding in the next month, but is that fruitless if this is indeed a crack... Or even if its not, will grinding remove enough of the surface to "fix". This isn't the driving reason i want it ground. I'd like to get the table slightly flatter and the left wing a lot flatter and just want that mirror finish.

the line runs almost front to back fo the table. Mostly straight but a little jagged at places. Sometimes barely visible, some lengths are more pronouced...

I tried to get good pictures, but struggled. Its the thin line that is barely visible in shot #2 between the right hand miter and right had extension wing


thx in advance
-brad

[Michael Wildt]

Could be a casting flaw. I doubt it has any impact on the performance of the saw unless it flex at that spot. I'd guess one could fill it with a welding bead then regrind if really needed.

[Bruce Wrenn]

It's a little hard for me to tell, but if line on right side of picture is "the crack", it looks like a screw was protruding though a sled of some kind. Each time sled was pushed across the table, it cut a little deeper. Cracks won't be straight. If it bothers you, fill it with some "JB Weld." I wouldn't try to stick weld it, as most likely the stress will warp the table.

[keith ouellette]

Could be a casting flaw. I doubt it has any impact on the performance of the saw unless it flex at that spot. I'd guess one could fill it with a welding bead then regrind if really needed.

My experience with welding has taught me that the heat can contort and warm metal. It is usually not enough to be noticed in almost all applications but in something like a table saw top it could cause a slight twist in the top. Especially if it is a long crack.

Most cracks that are welded reappear anyway. It would actually require drilling a hole at each end of the crack, all the way through the table, in order to stop the fisher. Then weld. It is the same way you would mend a cracked block.
I would only recommend it as a last resort.

Unless it is causing a problem I would leave it. Monitor its size. If it keeps growing then consider an operation.

[Scott T Smith]

It almost looks like a cold joint from the casting process.

If you choose to have it welded, I would suggest that you seek out a TIG expert that welds a lot of cast iron. Usually the process for repairing something like this would be to drill the ends, use a die grinder to cut a about a 1/4" to 5/16" groove into the crack, pre-heat the casting, and then TIG weld it about 1" at a time using a nickle rod, stopping to stress relieve the weld via peening as you go. The final step would be to machine the top of the weld flat where needed.

If you choose to leave it, one option would be to drill the ends of the crack - maybe 1/8" - 1/4" holes, and leave it. If you are concerned regarding the strength and dont' want to have it welded, you can have the bottom side of the table machined flat and a patch bolted in place.

[Paul Ryan]

Or you could just have Chris make you a new top. Who knows how much that would run? Looks like a crack to me though.

[george wilson]

You will be in deep trouble if you try to weld that top. Plus,the weld will not be the same "color" as the rest of the top,most likely. The best thing to do is just to fill it with J.B.Weld. It will come out less obvious than a weld,and you won't ruin your top by warping it.

I haven't seen a crack like that before,or such a straight "cold shut",where the metal flowed together,but did not bond. It is probably a stress crack from the casting cooling too quick. Maybe it was dropped during manufacture,or dropped after casting while still pretty hot-and weak.

Nickle rod will look a much different color from cast iron. I think the maker should replace it,but good luck on that score.

[Bruce Page]

I agree with Bruce, cracks don’t run perfectly straight & parallel like that. It’s a gouge from a sled screw. I’d just leave it and not worry about it.

[Ben Cadotte]

If it is a crack, do not try and have it welded. You will introduce more stress to the area. Take the strongest magnifying glass you have and have a close look. Also look at same spot from underneath using a strong light. If it is indeed a crack. Take a small drill bit like 5/32 or 3/16 and drill a hole centered at the end of each crack. That will keep the crack from progressing. The holes will not affect anything! If the crack does not expand beyond the stop drills, no worries.

If it really worries you. Take the top off and inspect from the bottom really well. If you can't find it from the bottom. It may be from scrapes from previous user (could be they used a knife to cut something and it went into the cast iron). If it's really a crack it will show from bottom as well (most likely eaiser to see since the bottom is not polished from years of use / cleaning of the top).

Aircraft inspector, if people only knew that there are cracks on airliners (that are allowable!!), alot of people would not be flying

[Steve Rozmiarek]

If it's a crack, you should be able to make it open up a bit by applying force in strategic places on the table. If it won't open, no crack, or at least insignificant. You could also get in magnafluxed. I think you can do it yourself, but that is a test for finding cracks in engine components.

[Ben Cadotte]

The only way to really know is to look at the bottom. A dye penetrant inspection from the top will only show whats already visible. The dye will fill the scratch, void, what ever it is on top and show what you can already see. So that would be no use.

The best way to put this to rest is to inspect it from the bottom side. If there is not enough access to do it. Then take the top off. Being a cabnet saw, not that big of a deal, and would have to come off if you were to try a repair / replacement. If you can see it from the bottom then you know for sure. If you don't see it but still not sure. Then do the dye penetrant on the bottom surface (Spot Check by Magniflux is the main brand that can be done DIY with spray cans).

If your still unsure. You can find a place that does Magnetic Particle inspection (again Magnaflux). But gonna cost you, unless you have a buddy with late night access.

Other options are ultrasonic and eddy-current testing. But expensive units and I know its not something I can borrow from the company for the night.

Again best bet is to check the bottom side. That will be the biggest / easiest way to determine if its anything to worry about.

[Ed Beers]

I suggest beer. Drink one and check to see if it still bothers you. Repeat as needed.

It doesn't appear to be causing any problems. Any "fix", aside from maybe filling with JB weld, might destroy your saw.

[Brad Ridgway]

Thanks All...

I went out an took another look but one thing i should have noted: this "line/crack" runs pretty much the entire front to back of the table. It is deeper/pronounced mostly around 5"-13" from the front of the table (gets to be hairline right around a line perpendicular to the front of the risen blade). The first 5 inches at the front is mostly not as deep, but there is an inch long section there that's just as pronounced as the 5-13 length.

That along with the crack/casting defect replies seem to indicate such defects shoud have a start and stop likely backs up the protruding screw theories somewhat as it's likely if this were a cross cutting sled, a screw in the front attaching the fence would have usually stopped at the blade. Then again, I can't explain the hairline which would have required such a sled to travel to the entire back of the table (unless a screw on the back fence protruded just ever so slightly and was exactly parallel to the front (doubtful). There's just a enough jaggedness to it at some places (i.e. it's not perfectly straight, but roughly 1-3/16" from the miter slot). The other thing that doesn't fit well with that thinking is that the gentlemen gave me almost all of his jigs / etc and a sled wasn't one of them...


I'm hoping Chris might chime in with whether he can remove enough to make it go away And ya i think Powermatic would likely decline to replace (claiming the protruding screw theory as well) and a new one from Chris i suspect would be far more than what he'll charge to grind this one.

-brad

p.s unfortunately it runs over the cabinet so access to view from the bottom until i remove is rather difficult... If i do take it to get it ground, i can definitely look then...

[Mike Parzych]

Since you bought it used, Powermatic isn't gping to do anything about it, and rightfully so on a 12 year old saw. It would seem the original owner would have gone back to them if it looked that way out of the box.

I suggest the beer remedy also. Ain't no big thing anyway.

[keith ouellette]

A crack could run the entire length of the table. If it is growing in length it will eventually reach the end.

Can you see the crack from the under side of the table?