goin’ round and round over squares
How neurotic do I have to be?
1) I want to tune up a new contractor saw. Do I need to bother to buy a dial indicator to check for arbor runout unless I detect a problem that might be attributed to a blade wobbling a few thousandths of an inch?
2) How good a try square do I really need? I’ve been using a cheesy plastic handled job I bought at a local tru-value. And I haven’t complained yet. But I’m thinking I should probably upgrade as I make boxes from smaller and smaller parts. How much should I have to spend to get something reliable enough for woodwork? I’ve seen some machinists squares in the catalogs, but I wonder if that’s overkill, even for machine setups and tuneups.
Also, I’ve noticed some try squares are true on both inside and outside edges. That would seem useful for checking the square of blades to tabletop. Or maybe you get a basic, square-on-the-inside-only wood-handled try square AND a machinist square for the outside square stuff, or…..
3)How square can a combination square really be? If it’s not as precise as a try square, then what is its purpose really? And if it can be really square, why do I need a try square, especially one without numbers enscribed on it, which is what I find truly useful about the combination square.
Does it pay to have a Starrett combo square for say $80 when others sell facsimiles for a fraction of that cost? Have I been working in blissful ignorance with my truvalu junk? Will all these quality squares make a difference or make the job easier?
help
gaf
Edited 9/5/2002 10:12:05 PM ET by gaf
Replies
Gaf,
Read the thread in this section, "setting angles on table saw accurately ".
You can set the saw to a degree of accuracy better than you can get with a high quality machinist's square, without using one.
Rich
Gaf,
The price of a square means absolutely nothing. All that really matters is whether or not it's accurate. It can be wood, plastic, steel, steel with rosewood and brass, or even cardboard. If the angles are correct, they're correct, period.
The one exception is the machinist's square which is unique because of its moving parts which require a high degree of precision. I've tried the cheap ones (Sears) and the less expensive ones (Grizzly) and threw them both in the garbage. Every time you moved the square's head you'd get a different angle. Stick with a Brown and Sharpe (sp?) or a Starretts. I'm afraid you won't find one for $80, but watch E Bay - they usually have both new and used for sale.
Jeff
> ...How neurotic do I have to be?
Well, you're not a alone, gaf.
When in the process of assembling my new saw (Delta Unisaw) I started having trouble aligning the extenstion wings with the table, I started examining things and found the table was a bit warped. Everything I had in the shop seemed to give me different indications of how much so I started increasing the level of accuracy of my measurement instruments. Feeler gauges, dial indicator, dedicated try square .... By the time I was done I knew about as much about the saw setup as the guy in final assembly at the factory it seemed (grin)
In my view, these things were tools I'll have at hand to check *all* my machines, over time, not just for initial tuning. So it was money well spent.
With respect to setting up the day-to-day angles for rips and/or crosscuts, Rich's explanation involving ripping a coupla boards to check for square, etc., is something I do regardless whether or not I had the most expensive try square on the market or my kids' plastic drawing triangle. My eye's seem to be less reliable than they could be when judging how close the blade is to being parallel with the toungue of a square anyway so the two board/two rip system provides a foolproof check b4 whacking away at some expensive piece of wood.
I am finding, however, with these newly acquired measurement tools, many of my machines, drill press, jointer, etc., have not been as close to perfect as they could be. With some judicial tweaking here and there, the level of quality of my work is slowly improving. I don't consider it an indication of neurosis to be concerned with how accurately one seeks to get one's machines adjusted correctly nor to pay close attention to things like blade wobble, arbor runout, and so forth.
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This is a little long and I appolgizes up front:
What you really need is one square that you use as a master square to check your other squares. Keep your standard in a separate box or protected place. Take it with you when you go to purchase any new square. You can find lots of measuring tools that are surprisingly accurate if you match them against your known accurate master square.
So, what to use as your master square? You can spend a $100 or more for a Starett or Brown & Sharp machinist square which goes out of square the first time you drop it or you can go to an art or drafting supply store and get a $10-12 plastic 30-60-90 drafting square. To prove it's exactly 90°, take two to a glass counter, put the shorter legs on the counter and face the longer legs at each other and butt them together (like a teepee). If the legs exactly butt, you have two perfect 90° angles. Buy one of the triangles and that becomes your standard or master. Now you can check your other working squares--or any you want to purchase--and determine if they are accurate. Keep your plastic master square some place where it doesn't get banged up and you will always have a perfect reference. Use inexpensive squares as your working squares. Check them from time to time. It they get banged up and out of tolerance, cheaper to replace the inexpensive ones than the high priced machinest square.
Here is the low tech, low cost way to align a tablesaw that I learned maybe forty years ago and teach to my students now.
Make 3/4 x 3/4 x 12" hardwood stick. Drill a hole somewhat centered in one end and insert a brass #8 x 1" round head wood screw about half way. Raise the blade completely up. Clamp this board in your miter gauge (if you determine that there is some slop in your slot to miter gauge, use a playing card to take up the slop) so the screw head just about touches the blade at the front. Now rotate the blade by hand (BTW, unplug the saw) and determine which tooth is the closest. Adjust the screw in or out until it just touches this tooth. Mark this tooth. Rotate the blade so the tooth is now at the back of the table and move the miter gauge/stick assembly to the back and see if it touches the marked tooth to the same extent. If it doesn't, adjust the trunnion (if a contractor saw) or the tabletop (if a cabinet saw) until it does. The blade does not move directly around the center so you will need to repeatedly go back to the front of the blade, readjust the screw, and then again measure the back. Be sure to check after tightening the trunnion as the trunnion frequently moves when being tightened.
The same adjustment gauge can be used to set the fence parallel to the miter slot. Slide the miter gauge to the front of the table and move the fence over to the screw head and insert a playing card between the screw head and the fence just so you can move the card as it touches both the fence and the screw head. Now move the miter gauge to the back of the table and see if you have the same feel when you insert the card. I like my fence absolutely parallel--if you want to have a slight opening to the fence, you can easily estimate the opening by adding a thickness of paper to the card.
I always show my students with a dial gauge that their adjustments are within .001 - .002.
You can also use the same gauge to measure blade runout by using a $5.00 feeler gauge.
Finally, after you are satisfied with the above adjustments, check the position of the splitter to make sure it is exactly in line with the blade.
Bottom line, there is no need to spend more than the $0.05 for the brass screw.
I couldn't help but add my two cents worth, since I seem to spend a third of my shop time testing and resting my squares, resetting my blades, etc.
First, make accurate cuts (square, in this case) and your work will fit together much better when you're ready for glue up. I'm sure you know the importance of this.
As someone said above, the price is not what's necessarily important. You can test any square (as described by someone above), and once you find (or create) one, it should stay square and trustworthy.
Find a standard square and keep it in a safe place. I have two such standards that I tested thoroughly and now never question (since I never drop them).
About the table saw blade, the manufacturer of one of my blades suggests de-tuning the blade to .005" out of parallel with the rip fence to avoid scarring the wood as it leaves the blade and fence. I use a dial indicator to set my blades. It's the only way to achieve this accuracy. I think it matters.
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