Resurfacing a Unisaw Top

[Rob Osborn]

Hello Everyone. I'm newly registered to the forums, although i've been reading here for several months. I have a questions and i hope that y'all might have some wisdom for me.

I was recently the proud recipient of an old unisaw from the 50's, given to me by my family as a birthday gift. It's currently the pride of my small woodshop. However, i've always been slightly bothered that the wings don't line up real well with the top. Both are even at the corners of the table, but seem to sag in the middle. I don't have a good straight edge, but either the wings are bowed, or the top is crowned.

I've been reading about the possibility of having the top and wings blanchard ground to true it up. A local shop quoted me about $100 to have it done, and i was wondering if you thought it would be worthwhile. If the wings were in good alignment with the top i probably wouldn't worry about it...but occasionally a wood chip or something will get caught and jam up the fence as i'm trying to slide it back and forth. Not a big deal, but a slight hassle.

Do you think the cost is justifiable for a machine like this, and do you think that flatening the whole surface would offer any improvement to the performance of the machine?

Thanks!

[John Thompson]

Sag in the middle of the wings won't affect the cut and I personally wouldn't bother nor spend $100 to have it ground. As far as a chip getting under the fence.. get a semi-soft brush and hang it on the side of the saw.. shelf near.. etc. Just brush off the table occasionaly as I really see no major issues outside or what I call normal in what you have described.

You might also add a couple of tabs of slick tape on the bottom of the rear of the fence to lift it up to some degree. That would give you some clearance and make the fence slide smoother also.

Good luck and enjoy...

Sarge..

[David Christopher]

flattening the top does make a difference in the quality of work you can do........I would definitely spend the 100 dollars........saw works better......saw looks better.....you will be a happy man.....

[Joe Jensen]

If you grind the top, you will need to have the miter slots ground too, or the miter guide will not fit right. Make sure to get a quote for that too.

I was able to level the wings on a old saw by using a bottle jack to push from underneath until it leveled out. I then drilled a hole and drove a precision pin in the hole to hold the alignment.

If the wing has a crown, align one side, pin it, align the middle, pin it, and then align the last end with a clamp or the jack and pin it.

IMHO, .020" or so of warp in a table top is nothing to worry about. Also, I use my saw a ton, and I never worry about the way the top looks.

[Ron Bontz]

Well IMHO I think it is a question of pride and ownership. Some people take old cars and get them functional again and drive them around with old paint and dents. Others restore them completely like new and take good care of them. Nothing like an old classic either way. Best of luck. Post a pic.

[Tom Henderson2]

Hi Rob.

The first step is to determine if it is the top or the wings that are out-of-flat.

If you don't own and can't mooch a good straight edge, what about a long level? most of those are pretty straight. Also, the "factory" edge ona piece of plywood or MDF is usually pretty flat.

If the top is flat but the wings are dished, you really don't have anything to worry about. If the top is dished... it is more complicated. Getting the top milled can lead to issues with the slots as was mentioned.

-TH

[Jamie Buxton]

Cast iron is a little flexible. If the out-of-alignment issue is something like a thirtysecond, you can fix it with the bolts that hold the wing on. IRRC, there are three or four bolts holding the wing. Loosen all of them except one at the end, where you say the alignment is good. Tweak the wing so that it lines up at the next bolt, and tighten it down. Repeat the procedure for all the remaining bolts.

[Chris Rosenberger]

Cast iron is a little flexible. If the out-of-alignment issue is something like a thirtysecond, you can fix it with the bolts that hold the wing on. IRRC, there are three or four bolts holding the wing. Loosen all of them except one at the end, where you say the alignment is good. Tweak the wing so that it lines up at the next bolt, and tighten it down. Repeat the procedure for all the remaining bolts.

This process will work. There is no need to get the top reground.

[John Thompson]

Morning Rob... I originally stated that sag in the wings would not affect the cut. You stated that the outer perimeter of the wings are flush with the actual top. I will stand by that statement. But... I will agree with Tom H 2 that the first step is to determine if you have a crown in the table or is it indeed just a sag in the wing which won't affect a thing really.

Until you determine if that top is relatively flat all the advice we give you here is just speculation of what you think and not what you know. A standard level should determine that. The actual cast iron top is not that wide and shouldn't be that hard to determine. Don't lay the level flat.. tilt it on edge and croutch down and look for light under it. Determining crown as you possibly suspected will not be that hard. You probably don't have a jointer but if you do.. even a jointed edge of a piece of stock will work to make the determination.

So.. I will back up here on what I originally stated or actually didn't state. If the top is excessively crowned or dipped (especially in the area around the blade opening) you have a problem to deal with. If the extensions are just dipped in the center and not on the outer perimeter as you mentioned.. I will most definitely stand by statement of it won't affect the cut and use the cash for a new blade... belts.. etc.

Good luck and sorry I did not mention what Tom H 2 did that you must find out if it is actual top or just dipped wings... others have mentioned methods to correct a dip in an extension if you want to go to the trouble which I would personally not as already stated.

Sarge..

[Alan Schwabacher]

Pay attention to Sarge. I would comment that one reason to adjust the way the wings are installed (once you confirm the table is flat) is that a tablesaw top can be a useful reference surface for various tasks.

[Chip Lindley]

Be apprised of the fact that blanchard grinding, in itself, may induce warp into your CI top or wings. Overheating by *hurrying* the grinding operation may cause you more problems than you have presently! Ask the machine shop owner about this before you commit yourself to a *shiny new TS top*!

I doubt seriously if your TS top is arched. Usually just the opposite is encountered with older TS tops, as gravity and weight of CI have the opposite effect.

Unless your TS top and wings are so scarred or pitted that you just cannot live with them, I would first suggest judicious shimming and adjustment to see if the top and wings cannot be brought into alignment. Using Grade 8 hardened bolts and nuts can help you torque the wings down to the top so that they *stay* in that position. Give this a try before you commit to blanchard grinding!

[Rob Osborn]

Thanks everyone for all your considerations. Following the advice that several of you gave, i spent some time attemping to line up the wings. Finally, after enlarging the bolt holes, i was able to get them pretty close...not perfect, but close enough for my skill level. The top has never pitted and isn't marked up, so i think i'm going to pass on having it ground for now. I'm still using the original fence, and decided that a fence upgrade would probably be more important anyway, so i think i'll save my pennies for that, or as someone mentioned, a better blade.

Thanks again for taking the time to answer my questions. I'm glad i asked before i made a decision!

[george wilson]

The older saws were Blanchard ground to begin with,but no doubt with special purpose built jigs to hold them while being ground. Blanchard grinding was the cheapest,and least accurate grinding method,and still is. The newer grinding techniques are very much better and look nicer,too. Today,they use a very big wheel as wide as the whole surface,automatically diamond dress it,and take the surfaces between the miter gauge slots at one pass. Then,the surfaces outside the slots are also ground. Jointer tables are done in 1 pass,with the wheel being as wide as the whole table. This is why you see a continuous,straight "grained" surface,instead of the old swirly surfaces of years ago,that were only .002" or .003" in flatness over the whole surface.

[John Thompson]

The older saws were Blanchard ground to begin with,but no doubt with special purpose built jigs to hold them while being ground. Blanchard grinding was the cheapest,and least accurate grinding method,and still is. The newer grinding techniques are very much better and look nicer,too. Today,they use a very big wheel as wide as the whole surface,automatically diamond dress it,and take the surfaces between the miter gauge slots at one pass. Then,the surfaces outside the slots are also ground. Jointer tables are done in 1 pass,with the wheel being as wide as the whole table. This is why you see a continuous,straight "grained" surface,instead of the old swirly surfaces of years ago,that were only .002" or .003" in flatness over the whole surface.

Thanks for your in-sight on the process, George. I have most definitely seen the variance of the swirl and the straight lines in my own machines and wondered why a different method was used. And I agree there is a big difference in the two even though I won't mention brand names on which I see them on.

Regards...

Sarge..

[Joe Jensen]

Thanks everyone for all your considerations. Following the advice that several of you gave, i spent some time attemping to line up the wings. Finally, after enlarging the bolt holes, i was able to get them pretty close...not perfect, but close enough for my skill level. The top has never pitted and isn't marked up, so i think i'm going to pass on having it ground for now. I'm still using the original fence, and decided that a fence upgrade would probably be more important anyway, so i think i'll save my pennies for that, or as someone mentioned, a better blade.

Thanks again for taking the time to answer my questions. I'm glad i asked before i made a decision!

Great decision. A good fence is much more important that the last .010" of flatness IMHO...joe