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Another Accuracy Question From Jerry...

6K views 44 replies 16 participants last post by  TwoSkies57 
#1 ·
Since I have a less than good reputation for dealing with accuracy in regard to wood working, (just a joke guys).

I recall several years ago when I first became interested in table saws, I read about the importance of such things as having the arbor on motor turn to very a very tight tolerance. The issue of getting a saw getting so perfectly tuned up just sort of went on and on. Due to these articles I was led to my attempts to get the accurate cuts that laterl on I was so politly informed that such accuracy was not part of wood working and of course in time I learned that for myself.

Now along the way I have heard from time to time the term "an accurate table saw".

This has led to wonder, "what is an accurate table saw", perhaps a better question is "what is an incaccurate table saw".

I have only had experience with one saw, the one that I have now of course, I have atttemped to line the blade with the miter slot using a Woodpecker Dial Indicator, and lwhild I can, after some puttzing around, get the error down to zero, however, I have been able tighten the table down and retain that setting, the best I have been able to get is to about .002" which is, as I understand it, very exceptable.

When I make a rip cut that is say 30" in length in one inch thick stock, the difference in the width of the material being cut from one end to another is usually within about .005". That's seems to be just fine to me.

My question, is this, If I had a high end saw such as a Unisaw or Saw Stop, could I expect more accuracy? Of course this is a ridiculeous question in that nobdy needs accuracy great that what I'm able to get with my cheap $700 Craftwman saw.

Now, the only thing that I can see and I assume that I'm right is that the Unisaw for example is made to operate 24/7 for years without much more that general maintenance.

So, would most knowledgable woodworkers say that my saw is "an accurate tble saw or not"?

If so, and of course I'm sure that everyone will say that the saw is just fine, then why all the writing about turning the arbor and putzzing with the set to a inth of a thousandth of an inch? Just wondering and thinking back about all of "Hdey Jerry, You Can't Accomplish The Accuracy With Wood That you, Jerry, are ltalking about"

Jerry
 
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#2 · (Edited)
I think .005 in 30”s is doing pretty well .
I have a General table saw and it’s arbor is .0002 , and I have the fence set .05-.08 run out on the far end of the fence in order to not get binding .
Works for me , although I can’t remember how accurate the outcome was. I noticed when I ran my woodpecker dial gauge along the Miter slot to fence , that there was a .02 discrepancy in the straightness of the fence .
So I think we’re overthinking this lol
 
#3 ·
I've had a Unisaw for about 20 years and the answer is no. While the accuracy stays within certain limits more so than say mid model saws it still will not dial in to zero. Other factors apply in the equation such as saw blade sharpness, saw blade plate thickness, grind type according to the milling action, bearing free play, feed speed and especially whether a constant feed speed can be maintained which is only possible with a power feeder, and last but not least on my list is grain change in density and direction as you saw.
 
#11 ·
I've had a Unisaw for about 20 years and the answer is no. While the accuracy stays within certain limits more so than say mid model saws it still will not dial in to zero. Other factors apply in the equation such as saw blade sharpness, saw blade plate thickness, grind type according to the milling action, bearing free play, feed speed and especially whether a constant feed speed can be maintained which is only possible with a power feeder, and last but not least on my list is grain change in density and direction as you saw.[/QUOTE


Charles,

Perhaps I did not phrase my question correctly. What I meant, is the accuracy that I can get with my relative cheap saw for hobby use about as accurate as I should expect. I think think that it is, and I know that it is close enough for me.

I just have not been on the forum for some time and wanted to get some new chatter going which I have and do appreciate the posts to my question.
 
#5 ·
My question, is this, If I had a high end saw such as a Unisaw or Saw Stop, could I expect more accuracy? Of course this is a ridiculeous question in that nobdy needs accuracy great that what I'm able to get with my cheap $700 Craftwman saw.
Considering that my saw was bought new for around $75, a lot of years ago, I do not consider a $700 saw 'cheap'. I can probably get accuracy close to what you get, but it does needs tuning to do it, frequently. I always leave a tad for sanding tho, so it doesn't really matter, it's a case of close enough is good enough. What does matter is, it still works, and is still used.
 
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#13 ·
The saw weighs 400 lbs.. stripped, that is before adding the router table, lift, router, two Incra LS systems and a Wixey 700R to it. So fortunately with 3200 square feet of floor space I don't need to ever move the saw, but I sure understand what you are getting at Doug,

By the way, thanks for the items that you sent to me several years ago, you may have forgotten them already, but I have not.

Jerry
 
#8 ·
That's a great question, Jerry. I understand that it's theoretical in nature so using analogies works well.
I can carry a pallet load of bricks in my van, no problem. Would doing it for long runs, on a daily basis be good for the vehicle? I'm guessing not, and I'd live to regret punishing it in that way.
I think if you ran 40 or 50 sheets of 3/4" plywood through your saw, every day, you'd soon notice not nice things happening to it.
It's just not built for extreme use, whereas the built-like-a-tank commercial saw is.
 
#16 ·
Sure have to agree with that, the little "relative inexpensive" saw that I bought and and used tor just short of three years was just right for my short time at wood working. I say short time as it appears that my woodworking days are behind me due to my health now, but they sure were fun days of learning and driving a lot of the folks kinda nuts with problem with accuracy. I might get well enough to get back to it someday but for now, it is not looking very good.

My brother from Oregon is coming to visit us this month and he likes to work in the ship, maybe he will clean it up for me and that would be nice as things have been setting for so long. He has offered to buy all of my tools from when the time comes. He is going to get a good deal too, I have about $15,000 in them and I offered to sell them to him for $8,000, if and when I want to or Vesta needs to after I'm gone.

Jerry
 
#9 ·
As accurate as you can get the setup is the starting point. Because of all the variables mentioned, the wood, the moisture content, blade deflection depending on the blade, perfect will never happen. In part you compensate for all those little errors by measuring a planing interior pieces in place and sneak up on the fit with sandpaper or block plane. If you got something that goes together well, then you're accurate enough. Relax Jerry, you have that Woodpecker tool, you're far ahead of the game.

I think the one place you want absolute accuracy is the blade being 45.000 or 90.000, and that's the job of a Wixey. Having that cut angle off will mess your projects up big time. Happily the new Wixey angle gauge now uses aaa batteries and even has an illuminated readout for us vision challenged old farts. Making face frames with pocket screws works badly unless your end cuts are exact 90s. That will also require either a good miter gauge or a precise TS sled (which depends on blade/miter slot alignment).
 
#10 · (Edited)
Your saw is just as accurate as my Unisaw. I am .001 or .002 on blade to slot and about .005 to .007 out on the miter slot to the fence for the full length of the fence. I had to add a piece of European Baltic birch to my fence to get it that close. I was over .015 out without the birch as I had a bow in the middle of the Unisaw fence. I have an old USA made Biesemeyer fence which I need to rearrange to be able to use so I can't tell you have good it is or not. I assume you need to use a full kerf blade to maintain accuracy.

What I notice about my Unisaw over my old contractor saw is how much more power and easily it cuts since the Unisaw has a Blador 3HP motor over my contractor Baldor 1 1/2HP . It is also heavier and has less vibration.

PS
You are lucky as my Delta contractor table saw would not tune this well.
 
#14 ·
Lee,
Yeah, it's that 3 hp motor that appeals to me, I can only imagine how lnice that would be. My saw, like your does work well enough with the material that I use. And yes, I use a full kerf Forrest blade most of the time. I have three thin kerf blades that I bought just to try them out.

I notice that most of the folks keep saying that they set their fence to be a few thous wide at the out feed end. In my ignorance I did set my Incra fence to zero run out a few months ago just to see if I could do it, I doubt if it is still at that setting now even though it has not been used for at least six months. I have always kept the fence close to zero and have not had experienced any binding, maybe I've just been lucky. I do have a MJ splitter have learned about kick back enouth to have pretty well eliminated the chance of having another one, sure hope so anyway.

Jerry
 
#17 ·
I have a Powermatic 66, a Unisaw and a "cheap" old Craftsman from the 1980's. I wouldn't trade the Craftsman for one of today's newer saws. Well maybe I'd trade it but if I was going out to buy a new saw I would chose an old used Craftsman cast iron saw over anything on the market. As far as accuracy the fence isn't that good but other than that I've never had a problem with accuracy. Why anyone would spend hundreds and hundreds on a contractor style saw when you can pick up a used Craftsman for around a hundred bucks is beyond me.
 
#18 ·
I have an old Rockwell 10" that I bought for $100 and I would agree with Art. I switched the original fence for a good aftermarket one and with a good blade it will do most things the Unisaw will. The factors I listed in post #2 are usually more important than the saw is. At least until you get down below about $500.
 
#19 ·
Chuck,

I think that what you pointed out about wood in post #2 is a must to keep in mind. That along with understanding that wood is, as pointed out in an earlier post is mostly empty space, not a solid substance, grain and twisted grain along with all that you listed, when considered, should make us appreciate how fortunate we are that we can do as well as we can with it.

Jerry
 
#20 · (Edited)
I just went out and measured my Unisaw again. I have run several hundred feet just from my kitchen remodel of maple and 3/4 inch old plywood through it. I don't remember how much before the kitchen remodel but it was last year when I last measured my Unisaw.

I am at .002 on the blade to the miter slot using my Woodpecker gauge. My fence was .026 out. It turns out I was able to tighten the screws holding the Baltic birch as they were a little lose. I don't know if it was weather or use. I will need to watch them. I tighten the screws holding the Baltic birch on and my fence and it is now .013 out for the full length of the miter slot.

PS
I just got my fence down .008 out playing with the back fence tensioner. This is the best I have seen. I guess you learn something every day.
 
#21 ·
I think when most people refer to the accuracy of a saw, what they are really talking about is the accuracy of the fence. My first saw came with one of those fences where you measure to the front of the blade, then measure to the back of the blade to avoid pinching. There was no hope of using the measurements on the rail at all. With my current setup, I can line up the hairline cursor on the rail, make a cut, and be confident that the actual width of the board measured with calipers will be within .005 inch of the intended width. I could never have achieved that sort of accuracy with my old setup.

My old saw itself was inaccurate. I could set the blade parallel to the miter slots within .002 inch alright. But as soon as I tilted the blade and went back to 90 degrees, all bets were off. There was so much slop in the tilt sectors that it might wind up no where close to its original setting.

I think most of the older saws themselves were fairly accurate, even if they had inaccurate fences on them. Some of the stuff coming across the water to us now looks heavy and well-made at first, but has sloppily cast parts where it needs machined parts.

But don't worry, you'll know when your machine isn't accurate enough for the work you're trying to do with it.
 
#25 ·
then why all the writing about turning the arbor and putzzing with the set to a inth of a thousandth of an inch?
Jerry
Applying acceptable tolerances to setup, and realizing the limitations of ones equipment provides the end user with a realistic expectations. The process measuring/metering identifies the need for eliminating or compensating for the variables associated with any piece of equipment.
Doesn't matter if its a 700 dollar Craftsman or a 14000 dollar Powermatic, most of the variables are constant within the line. Expectations for the Powermatic are far greater than those of the Craftsman and with good reason. Knowing what to expect and applying that to whatcha got lets ya know just what you have.
Tolerances and accuracy often fall prey to convenience and acceptance..
 
#28 ·
Forgive me for bring up my old camparison again, but what Bill is saying is so true and it really is evident in regard to firearms. A hunting rifle that is considered to be accuracy for hunting is a piece of junk for precision shooting. It all has to do with tolerances. A mass produced product has to be built within specified tolerances, the fact that these tolerances even exist is what makes the rifle a piece of junk for precision shooting. A custom benchrest rifle is accurate because the tolerances are for the most part "eliminated" and the results show the difference.

The boy with his trusty thutty thutty that puts venison in the freezer year after year has a rifle that works just fine for his need. The benchrest shooter needs a rifle that can put five shoots into a circle the diameter of thutty thutty bullet at 200 yards is another matter. Tolerances along with the need for the job at hand is what Bill is saying.

Jerry
 
#31 ·
That's what I hear Jerry. I paid about $2400 20 years ago and it may be still worth close to that used. Any that go for $400 need lots of work and often are missing the fence
 
#38 ·
I suspect those who rattle on about adjusting for unnecessary degrees of accuracy are the same folk whose shops are picture perfect and completely free of dust, i.e. they never do anything much, other than attend to the housekeeping and admire their array of perfectly displayed tools and materials.
 
#39 ·
Keith,
Do I detect a slight note of sarcasm???????

I would suggest that perhaps when you see a post of mine that you should not read it if it is bothering you. Fact is, you probably did not mean what you said the way it sounds to me, right?

Also, unfortuanately, my shop sits in the middoe of several hundred acres of farm land, not all ours but when the wind blows things get really bad. My shop is so bad that cutting MDF nover creates enough dust and debri to even notice compared to the other dirt and stuff.

So Keith, in this case your assumption is, unfortunely for me, way off. I wish that I keep in all neat and clean.

Jerry
 
#40 ·
The .222 was big in the early 60s to 70s. The gunsmith I worked for ( I was in high school and this was my dream job then) told me the .222 was dead because the military chose .223 so I sold my .222 in 1972.

Yes I shoot a 308 Remington 700 5R bull barrel with a Nightforce variable to 42x power. I don't remember the low power.
The benchrest shooters have moved to 30 cal over the 6mm because it makes a bigger hole. That little bit of bullet difference may cross the line for the next higher score. They are all wilcats of 30 cal with low power charges to reduce recoil.

I have a friend with a high end benchrest rifle. At 100 yards you put the cross hairs on the X and it will shoot a bullseye every time. It may not be an X score but it is always a 10.

I use to shoot pistols. I shot 2700 completion. My eyes are so bad now I can't score very high any more plus they allow red dots which my target pistols are all setup with irons sites like old school. I also shot on the University of Texas pistol team in the old days. I had to carry my pistol to school at least 3 times a week or I got yelled at by the Gunney. Carrying a pistol to school now days would not go over so well.
 
#43 ·
Marco has hit the nail on the head. I've made and given away as presents a huge number of projects and to the best of my knowledge no one has taken instruments to check on the accuracy.
 
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#44 ·
Whilst it has been mentioned casually, it is most important to have the out-feed end of the fence a whisker wider than the in-feed to prevent jamming and sending the wood flying across the shop. Also always stand at the side of the saw table just in case!
 
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