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Grind arbor or replace table saw?

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Forum topic by Sark posted 06-27-2019 08:57 PM 635 views 0 times favorited 14 replies Add to Favorites Watch
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Sark

162 posts in 815 days


06-27-2019 08:57 PM

Topic tags/keywords: arbor delta unisaw

The kerf on my table saw cut is running about 1/64” wider than it should be. This is what causes the the cuts to not be clean enough. And also excess vibration. Tracked the problem down to the arbor which wobbles. So I would like grind the arbor in place till it runs true. 1/64 is way too much out of tolerance.

Just wondering if you’ve had success with this process? I tried this on an old and cheap table saw years ago, and I couldn’t really tell if my efforts paid off…or there was something else wrong with the saw. Didn’t really keep it around that long to find out.

My tablesaw is about a 30 year delta Unisaw which I bought used about 5 years ago ($600). I like the saw, But I’m now faced with ‘grind or replace’ kind of decision, since I just noticed how badly out of whack the arbor is. What do you think?


14 replies so far

View LittleShaver's profile

LittleShaver

565 posts in 1074 days


#1 posted 06-27-2019 09:20 PM

I’d try replacing the bearings first. Much more likely to be worn out than shaft.

-- Sawdust Maker

View Sark's profile

Sark

162 posts in 815 days


#2 posted 06-27-2019 10:55 PM

The bearings were new replacements when I bought the saw. So that meant either a bent shaft or bent arbor. Grinding the arbor would work for both conditions. So I just ran a test.

First, in the original state the runout was .024”. No wonder the blade vibrated and the kerf was so wide! Almost 1/32” of wobble.

Next I chucked a die-grinder stone with 1/4” shaft into my router, positioned the fence so that the stone just touched the arbor. Turned on router and saw and let the sparks fly. Made 2 more grinds. First and second grind showed improvement. Runout was .013”. Surprised that the second grind didn’t improve things, I looked at saw that the stone had been worn down, and wasn’t able to to fully face the arbor surface.

For the 3rd grinding, I found another stone that had enough meat to fully surface the arbor. Moved the fence ever so slightly, and ground a few more times till there was no sparks and no rubbing. Then, since it looked so scratched, I used sandpaper to smooth out the arbor, first 120 grit and the 500 grit. That made the arbor shine like new.

And the final result is .006 of runout. Of course I’d like less, but I think I can live with that much. This is woodworking after all.

From a practical sense, I realize that if I use the kerf width as a measurement, the results will be slightly off. Suppose that I just cut a 2” wide piece of wood and want to cut a 1/8” strip. Move the fence 1/4” and the result will be less than the expected 1/8” wide measurement because of the too fat kerf.

So how much runout will you tolerate?

View BobHall's profile

BobHall

65 posts in 1740 days


#3 posted 06-27-2019 11:15 PM

First, I’m glad that you got it fixed, .006 would be good enough for me. I’m no machinist , but i cannot understand how grinding the arbor, however slightly didn’t make the blade fit loose on the arbor and make the situation worse. However, it didn’t and that’s what counts as a Unisaw is a fine machine and worthy of saving. If it had come down to it, a Unisaw arbor can be bought used or probably new without much searching.

-- Bob "jack of all trades, master of none"

View Sark's profile

Sark

162 posts in 815 days


#4 posted 06-27-2019 11:54 PM

BobHall, I think I got the vocabulary wrong. The part that I ground is called the flange which is attached to the arbor. The arbor + flange are sold as a unit and on ereplacement parts, sells for $161. I just looked this up. So I was grinding the flange, with moderate success.

After grinding, it looked pretty rough, so I smoothed out the flange with sand paper 120 grit and then 500 grit with the saw running. Now it looks quite shiny. I can certainly live with .006” runout, and I have a lot of other things to spend money on,

View farmfromkansas's profile

farmfromkansas

101 posts in 69 days


#5 posted 06-27-2019 11:57 PM

Hope your blade fits tight enough on the arbor. Think I would have just replaced the arbor.

View Delete's profile

Delete

439 posts in 827 days


#6 posted 06-28-2019 02:10 AM

I was wondering what the heck you were thinking about grinding the arbor. It makes more sense now that you refer to the blade flange. If you have a press and you obviously have good testing equipment, you could have tried to straighten the arbor shaft. Grinding the blade flange sounds like it has taken out most of your side to side wobble but if the shaft is bent you will still have vertical runout, not a problem for through cuts but will be less accurate for things like dadoes and rabbits and will still contribute to some vibration. A good Unisaw is worth far more than it’s arbor. I would purchase a new arbor and keep the old one as an emergency back-up.

View MrUnix's profile

MrUnix

7451 posts in 2654 days


#7 posted 06-28-2019 02:41 AM

Don’t forget to address the blade washer as well… see this post by Mattias for his method:

Fixing the wobble in a table saw arbor

(by Matthias Wandel over at Woodgears.ca)

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View BobHall's profile

BobHall

65 posts in 1740 days


#8 posted 06-28-2019 01:08 PM

OK, now that makes perfect sense. Thanks for clarifying!

-- Bob "jack of all trades, master of none"

View Stevedore's profile

Stevedore

89 posts in 2480 days


#9 posted 06-28-2019 01:26 PM

I put up with a bit of blade wobble on my Delta contractor saw for a while, & finally decided to do something about it several years ago.

I screwed my router onto a small board that I could hold against my tenoning jig on the table saw. I used a small cylindrical stone in the router, which I could gradually advance against the arbor flange by using the fine adjuster on the tenoning jig. With the belt removed from the motor & arbor, I rotated the arbor slowly by hand as I gradually moved the router towards the flange. Worked very well; the wobble was very noticeable as the stone began to contact the flange & remove material. When I reached the point where the stone was barely touching the flange uniformly around its circumference, I was done.

I don’t recall exact numbers, but blade tip runout was then insignificant, & my cuts were much nicer.

A couple of pics may show my setup better than my description above:

-- Steve, in Morris County, NJ

View CaptainKlutz's profile

CaptainKlutz

1646 posts in 1949 days


#10 posted 06-28-2019 02:40 PM

Glad you got that fixed.
Read somewhere that Delta used to grind arbor flanges on machine during assembly?

My used Unisaw purchase had little too much run out for my liking after bearing replacement, and I ground the flange also.
My method was like WoodGears above, but done by hand with flange vertical?
With blade off, turned on saw; and gently touched the stone to flange. Had a couple strips of tape on edge to avoid damage to arbor, which helped keep it square to face. I could see the wobble when it spun, and with 8” long stone it was not hard to keep it square and parallel to opening. Material was removed fairly slow, no sparks when I did it. Flange was hardened, had to slide stone back and forth as it tried to cut a groove in stone.

Cheers!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View Turns4wood's profile

Turns4wood

51 posts in 237 days


#11 posted 06-28-2019 02:42 PM

no one has addressed the trunions if one of them is loose or you are not 100% square to the fence you will get a wider cut might check that out as well

-- Nothing better than sawdust on the floor

View MrRon's profile (online now)

MrRon

5631 posts in 3698 days


#12 posted 06-28-2019 05:50 PM

It doesn’t seem likely to me that only the flange would have excessive runout, and the arbor itself would be straight. You could get .006 runout on the flange, but that doesn’t mean the arbor is straight. Just because the bearings were replaced when you bought the saw doesn’t mean they are good. Bearings can range from a few dollars to a lot of dollars, depending on the class of bearing. The previous owner may have used the least expensive bearing available. If it were my saw, I would replace the bearings with high quality bearings and replace the arbor.

View Sark's profile

Sark

162 posts in 815 days


#13 posted 06-28-2019 11:23 PM

Mr. Unix, thanks for the link. I wasn’t happy with my first set of results, so I tried the system in the link. This is with moving the arbor fully up and tilted 45 degrees. This makes it easy to grind with a stone that is clamped to a block of wood. Results: .002-.003 runout ! Exactly what I wanted. This is within the tolerance of the sawblade, which is a brand new Forrest blade.

Stevedore, your method is close to what I first tried. Except both the router and the TS were running, and I didn’t have the use of a tenoning jig for precise measurement. Just pushed by hand.

Turns4wood, I hadn’t thought about loose or misaligned trunnions. So next on the list is the whole adjustment routine and lining up fence with T-slots and sawblade. Meanwhile, the cut is very accurate and smooth, which suggests that the other parts are properly tightened down.

Thanks to all.

View SSotolongo's profile

SSotolongo

59 posts in 152 days


#14 posted 06-30-2019 11:57 PM

Since you paid $600 for it, I would try and fix it first. I’m cheap as hell though. Like others have said check the bearings. They may need replacing and perhaps grinding the arbor if its not the bearings.

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