Bowed Table on Band Saw - Advice Sought

[Turbo]

The table on my generic 6x4 bandsaw has acquired a bow across its width. This means that any metal you place on the table rocks, ruining any chance of accurate cuts!

What I think has happened is that through time the moving jaw on the vice has been forced upward when tightening the vice & over many years this has bent the table up. The peak of the bend seems to be along the edges of the long slot.

I've tried to pull it down with a clamp & some heavy box section, it didn't move.

I tried it again, this time with a narrower top plate.

It did move a bit this time but sprang back when the clamp was loosened.

I have a very big rosebud oxy/propane torch to heat this up & maybe combined with the clamp it might work. The other way would be to grind or scrape it flat.

Any suggestions of a better way of straightening this?

 

[Farside]

Any suggestions of a better way of straightening this?

Cut a 1/2" thick slotted plate and weld it on?

 

[Turbo]

Cut a 1/2" thick slotted plate and weld it on?

That was going to be plan 'B' if I can't get this straightened! Not be welding it though, table is cast iron!

 

[Agroshield]

Roughly what height is the bow? 1mm, 2mm, etc.? How long forward to back is it? If it is local to the end near the pivot, maybe moving the fixed jaw away from the pivot would work. That would reduce capacity but maybe that is not a big loss for you. If the bow is not too much a 12" coarse file might sort it.

 

[Sergei Slovenija]

Just scrapering it

 

[Brad93]

You'd be there a long time scraping that bearing in mind the average scrape is 0.0002"-0.0004"

Milling or Grinding.

You could try heat and bend it back but it's probably not a high quality casting, localised heat could cause fractures

 

[Erie Fred]

Mine is pretty thin underneath there, I would suggest as above a new plate (maybe just 1/4" thick) but bolt on with flathead screws, and then you can shim it.

 

[Keith 66]

True engineers look away now. Cheapo quick way, I repaired a big Dankaert circular saw that had its table busted in two by a JCB & mounting lugs snapped off. Steel plate with holes, Drill & tap existing table to take machine screws, bed down on P38 (dont have to wait) Same done with mounting lugs.
It gave 15 years of hard service after that.

 

[Screwdriver]

Flatten it with emery. Be easier with a heavy (flat!) steel plate or maybe a stage weight if you've got one.

Might take a while but it's good exercise and it will get the job done.

 

[addjunkie]

Big flat file, and just file it flat. Why over think it.

 

[James1979]

Big flat file, and just file it flat. Why over think it.

+1

 

[tigdlo]

I've seen a guy on youtube "scrape" a cast surface on a lathe apron with an angle grinder to give a flat surface for a magnetic base. Done similar myself on steel, surprisingly accurate once you get the technique, fast light passes, shallow angle, change direction after each pass, check progress frequently, looks like really bad scraping.

 

[Erie Fred]

"Removing material" repairs's.....Is not the machine surface too thin already ?
Why did it warp ?
Removing more material sounds counter intuitive.

I like #8 above with the bedding material.

 

[Brad93]

Use belzona or other ferromagnetic epoxy for best results as bedding compound

 

[Gareth J]

It's already proven itself to be weaker than ideal. Removing more material, isn't going to help that. Especially doing it by hand, that sounds like a punishment!

Flat at plate glued and screwed as mentioned above, or, if the top surface originality is important, bracing and re-enforceing from below, though you'd have to work out some way of pushing it back too.

 

[James1979]

I may be way off the mark here, but it looks like that’s the side that the length of material sits?

It seems the vice has clamped up on the workpiece and the long part sticking out that side has caused a moment which has then lifted / bent the table, rather than the vice movement? Might not of done, it’s your saw and you could see it before you took it apart so you’ve a better idea then me.

If I am going down the right line with it, a Jack stand or roller stand would help a lot

 

[Screwdriver]

While it it true to suggest removing material might tend to make the part weaker it is a tiny amount of material (20-50 thou I hazard a guess). Turbo now knows there is an issue with that area having weakness so he can work around that or mitigate the problem with correct handling etc. It's probably more due to leverage from the part being cut than inherent weakness as James suggests.

Either way I'd want to make the surface flat before I glue anything onto it and once the surface is flat it becomes useable again so in theory you could do both.

It is not entirely impossible that the casting has simply warped over time all by itself. Back in the day, a cast part would be "seasoned" for years before being machined. Dunno if they do that any more but they're unlikely to do it with a machine at this price point...

 

[Farside]

True engineers look away now.

That's proper engineering.

 

[Windy Miller]

Would it be possible to place a heavy ‘non-bendable’ plate/channel/box section underneath and pull it back down flat with some countersunk Allen screws?

 

[striker]

Have you considered making a new bed from a hefty piece of channel and some pillar blocks bearings for the pivot point?