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. :rolleyes:

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?

[Bob Aquino]

I don't see a crack in the pix. Cracks are not usually straight lines. If you have the top ground then you will also have to have some machining done on the miter slots otherwise they will be too shallow. It won't affect the quality of the work the saw can produce, its a cosmetic defect only.

[Tony Bilello]

If you just want that mirror finish, go for it. I personally would not even concern myself with that line which does not look like a crack. As others have said before, it is too straight and parallel to be a crack.
Trying to implement any kind of a 'fix' for that line may introduce serious problems which I dont believe you have now.

[Ed Beers]

There is no doubt that you can grind until the scratch is gone. However, I wouldn't remove even an extra thou just to get rid of it. The more you remove, the more likely the table is to warp after grinding.

If all you want is a mirror finish, you can get it by wet sanding.

Ed

[Myk Rian]

Call the fellow you bought it from and ask about it.

[David G Baker]

If it is a crack and it has not caused any problems, the cost and potential issues that could be caused by the repair may far outweigh the benefits. I would keep an eye on it and if it gets larger or causes any problems then I would do something about it.

[Chip Lindley]

I concur with the *sled screw* theory! No way is it a crack! If your table is flat and your PM66 performs to your expectations, just leave it As-Is! Further welding or grinding will probably screw up the table!

It is a *Battle Scar* from previous use! Used equipment is always *buyer beware*! IF you did not notice the flaw in your *adrenaline rush* of being in the presence of a real PM66, remember to take cold, calculating pause to inspect next time!

I hope your got a GLOAT on your PM66 when you purchased it!! One *helluva* saw! ENJOY!

[Gary Click]

Brad,

Where are you located, you mentioned taking the table to Quality? Are you close to Birmingham, AL. If so I can "loan" you material to check the "crack". We can look at it wih Dye Penetant, Yoke Magnaflux or Ultrasonics.

Lacking that you can do a poor man's dye check with kerosene and lime or plaster of paris. Wipe the surface down with the liberal oat of kerosene or WD-40 in a pinch. Wait 3 or 4 minutes. With a clean cloth completely remove the oil and dry the surface as completely as you can.

Lightly dust the lime over the area and watch, you want a light dusting that doesn't cover the surface. The lime will wick the oil out of the "crack" if its there no mattter how well the surface was wiped off. The "crack" or more correctly Linear Discontinuity will appear as an slightly darker line on the white background.

If it is a scratch it may still bleed but the indication will be fainter and more of a background haze since the scratch won't hold very much oil.

[Jude Tuliszewski]

Ditto what Gary Click said. The nature of dye penetrant is to seep into cracks. The residual to be washed/wiped from the surface, the part gets dried, lightly dusted with powder then heated and then looked at. In a lot of aviation applications the dye is designed to be used with a UV light. Like Gary said you can get away with WD 40 or any penetrating oil. More or less poor it along the area in question let it sit for about 10 or 15 minutes then wipe it clean (after the excess is wiped do a very light wipe down with mineral spirits). Let dry, lightly powder (should be able to use baby powder as well) and wait a few minutes. If you want to get fancy get a blow drier or heat gun and heat it up a little before you dust it with powder. If it is a crack it will show.

[Mark Bolton]

An alternate to the sled screw theory that could answer the slight jagged factor would be something as simple as a past owner ripping a board/piece of ply that had a screw/nail/staple in the underside. I am not sure if this has been stated.

We have many times ripped pieces that have something we missed which will scratch the table.

Mark

[Brad Ridgway]

Thank again folks...

Gary, (i'm actually in Central Florida) but i tried WD-40 and a little DE (diatomaceous earth) as it was the only powder i could find... It absordbed nothing at all.

I did try to find any sign under the table as well and nada from what i can see (but agin it's right up near the cabinet so hard to tell 100%.

Third i was able to contact the seller (ebay feedback tracking has multiple purposes) and he was pretty sure it wasn't a crack and said he had all kinds of stuff on there and thought that his handling was more likely the likely culprit...


Anyway, pretty sure i'm good... Spend several hours sanding the top.. I still have a tough time getting a lot of the stains out, but it looks a lot better than it did. I think i'll keep it for now. Maybe someday later i'll grind...

[Chris W Brown]

Brad I will give you my two cents for what its worth. We have machined thousands of tables and ext wings over the years and have never seen a table with a crack. What I have seen are pits in the surface of a table, very small pin holes what we call porosity. When you start to grind the pits get larger the more material you remove. This don't sound like a crack but I have been wrong before.

Do not try and weld the table your asking for major trouble. We have welded cast iron before and it's just not the same. The heat will put a lot of stress back into the table and it will not be flat.

I don't think the scratch will effect the saw in anyway. The main reason to have it ground is to make sure its flat and parallel. The flatter the surface, better the cut.

Chris