Main Table Alignment Fun

[jm51]

Geez! It is bad enough to adjust to the variability of the carriage, headstock, table tubes, trunion, quill bore. . .

Adding the creation of a jig that replicates all those aberrations? I do not think so!

So the headstock/quill is out of true and the end user has to mess about to compensate for that?

I'd have thought that any machine with a quill should have that quill spot on (relative to the way tubes in the case of the SS) before moving to other alignments or is that not possible with a Shopsmith?

As most work is done with a non tilted table, could a spare table be aligned and then welded up so that it never goes out again and it's just the table for mitres that will need adjusting from time to time?

[algale]

Algale, yes you need to use your eyes and ears when making test cuts after aligning the saw, but preventing kick back is not the only benefit or purpose of alignment. And, aligning the blade and fence to the miter slots is not the end of the alignment process. Test cuts tell you if you got the set up right, otherwise you learn when cutting wood for a project.

If the back of the blade is closer to the fence than the front, you risk kickback or burning the sawn edge. If it's the other way round, the wood pulls away from the fence and you won't get a straight cut. If you force the wood against the fence, you get burning.

How far out of line you must be to risk a kick back is not a fixed amount. It depends on the width of the carbide tip and the thickness of the plate or body of the saw.

If the blade is not perpendicular to the miter gauge, you indeed get a wide kerf, but you also get increased chip out and a ragged cut and scoring along the cut line. Part of the set up also is to ensure the blade is perpendicular to the saw table. Simply flipping the board over and putting the sawn edges together shows the accuracy of this part of your alignment. If the blade is not perpendicular to the miter gauge, you get an angled cut. Flipping the board over and putting the sawn edges together demonstrates if you got this alignment right.

Test cuts point out the accuracy or flaws in your set up.

Hey Art,

Yup. I oversimplified things about the out-of-alignment only causing either kickback or a wider kerf. Burning and ragged edges are also a risk, as you say.

But I not sure I agree that the blade not being perpendicular to the miter slot causes angled cuts. If the stock is is held perpendicular to the direction of its motion along the miter slot, both the front and back teeth will cut perpendicular kerf lines through the stock. Think about a wobble dado. Talk about a blade that does not run perpendicular to the miter slot! Yet it cuts straight dados.

Al

[robinson46176]

Hey Art,

Yup. I oversimplified things about the out-of-alignment only causing either kickback or a wider kerf. Burning and ragged edges are also a risk, as you say.

But I not sure I agree that the blade not being perpendicular to the miter slot causes angled cuts. If the stock is is held perpendicular to the direction of its motion along the miter slot, both the front and back teeth will cut perpendicular kerf lines through the stock. Think about a wobble dado. Talk about a blade that does not run perpendicular to the miter slot! Yet it cuts straight dados.

Al

A wobble dado is all together different... While it wobbles, its arbor and quill when properly set, is at 90 degrees to the miter slot. In a miss-aligned table situation the miter slot is no longer at 90 degrees to the arbor/quill... The wobble dado reaches over and cuts but then moves away. In a miss aligned table situation the saw blade stays at that wrong angle to the path all of the time.


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[dusty]

I wish that this forum required every post to have a title.

I think we might have sorta lost track of what this thread is all about.

Aligning the table to the plane of the blade is the key thought. How each of us does that is obviously not the same as all the others.

It is, however, a safety factor. Please develop for yourself a way to do this with reasonable accuracy.

Ask more questions if need be but get it right. Avoid be the cause of a kick back.

[algale]

A wobble dado is all together different... While it wobbles, its arbor and quill when properly set, is at 90 degrees to the miter slot. In a miss-aligned table situation the miter slot is no longer at 90 degrees to the arbor/quill... The wobble dado reaches over and cuts but then moves away. In a miss aligned table situation the blade stays at that wrong angle to the path all of the time.

Not sure that a wobble dado can be aligned but I no longer have one to test that out.

But another way to think about why the table's alginment has nothing to do with straight cuts is to think about how you cut cove molding on a table saw. You put a temporary fence at a severe angle to the blade. That's like a very badly misaligned rip fence. As long as a square edge of a board is kept against this angled fence the edges of the cove (which are just non-through blade kerf cuts) will be parallel to the edge of the board and the temporary fence, i.e. athe blade has cut kerfs that are square to the edge/fence.

Now we usually do this along the long edge of a board because we want a long piece of cove molding. But the principle is no different if instead of a temporary fence you had a miter slot at an angle to the blade. In fact imagine if you could mount a miter track on top of your cove molding temporary fence and put your miter gauge (set to 0) in the slot. Put a long board against the miter gauge and push it throught the blade like doing cove molding. You will have a cross cut cove with its edges (kerfs) at 90 to the long edge of the board.

[JPG]

Mis-alignment of the miter slots to the blade.

As regards the squareness of a miter gauge held workpiece cut with either a warped blade, a wobble blade or a mis-aligned table. End result will be as square as the miter gauge. The path of the cut will determined by the motion of the miter gauge as it feeds the workpiece into(and away from the back of) the blade. The differences introduced by the three conditions above are wider kerf, wider wide kerf, and a wide kerf respectively. The extra wideness is caused by the blade rotation not being parallel to the motion of the workpiece in all three instances.

Rip Fence alignment.

We have a catch 22 in that we can mount the fence on either side of the blade, so intentional skewing the fence(to preclude narrower rear space) will only work on one side(causes the narrowness when on the other side). This assumes the fence aligns to the table parallel to the slots and blade.

Table front deviations.

Since the rip fence references the table front, the alignment of the fence may vary if the front is not straight. I have 'discovered' that the extrusion on the front of a M5(later Goldie) or MV 500 can be 'warped/bent'(not straight). It is secured to the table front with three screws/lockwashers. Although there is a ledge the extrusion can 'self' align to, any local deviation from straight can(and will) cause the fence alignment to the slots to vary. FWIW it may be possible to bias the fence in opposite directions on opposite sides(I have not done so, but have biased one side to 'match' the other).

Conjecture: Shimming(very slightly) a 510 or 520 front rail may also be possible to allow slight extra blade clearance on both sides of the blade. Those twins from the north woods of Wisconsin recommend 0.02 at the rear!!!

Ripped edge squareness.

The ripped edge squareness is determined by the trunion stop/setting, and is independent from the blade slot alignment.

Spot on positioning of everything else.

Ain't no such thing. Just different degrees of missing. Anything that is movable has inherent slop. All those things I mentioned above are movable and then 'lockable'. If not locked any alignment adjustments will be altered when later locked. Therefore all those locks must be secure. Now with them all locked, the resulting position of things will be somewhat deviant from 'perfect'.

Other consideration(s).

Need I say that locking everything includes legs firmly on the floor. Repositioning to another area MAY alter alignment, but IMHO the legs are slightly compliant so as to minimize that, but they are limited in range.

An SPT may alter the setting of the legs on the floor(heavy jointer especially).

Realize this equipment is not rigidly secured to the Hoover Dam and will be variant.

All this is why I think a deviant jig is impractical.

Accuracy is determined by the power of one's magnifying glass!

Good enough is a matter of practically.

Not to be overlooked is the tie bar clamp.

[algale]

Mis-alignment of the miter slots to the blade.

As regards the squareness of a miter gauge held workpiece cut with either a warped blade, a wobble blade or a mis-aligned table. End result will be as square as the miter gauge. The path of the cut will determined by the motion of the miter gauge as it feeds the workpiece into(and away from the back of) the blade.

Yep, that's what I thought.

[algale]

Post Script: Anyone reading this far into the thread who is having difficulty aligning the main table is advised to check their rear trunnion mounting holes to see whether they are undersized.

After wrestling with mine to get it into alignment, I stumbled on this thread http://shopsmith.net/forums/showthread. ... nion+drill which discusses a trunnion manufacturing error where the holes in the rear trunnion were drilled undersized, which gives less play when trying to align the table by pivoting it around the right rear trunnion bolt because the left rear trunnion bolt has very little clearance.

I had found the rear of the table hard to move but hadn't thought much of it. I had managed to wrestle the table into alignment but was finding that even a slight tightening of my trunnion bolts was causing the table to jump back out of alignment (which is why it took me 4 hours to do it).

So I suspected my Mark V 520 (purchased by the previous owner 1/10/01), might have the trunnion hole defect. I couldn't decide whether it was worth taking the trunnions off to have a look because it was in alignment. But I feared that I'd forget about this issue the next time my table needed alignment so I decided to have a look.

Sure enough, my trunnion was drilled defectively. Luckily post # 53 of the trunnion thread shows how to easily set up your Mark V to fix itself by drilling out the rear trunnion in horizontal boring mode using the auxiliary table for support. (Do use clamps, however.)

I am happy to report that after drilling the rear trunnion to the proper clearance, I remounted the table and I was able to bring it into alignment quite easily with a dial indicator and while the table still wanted to move as I tightened the trunnion bolts, the movement was very slight. The final measurements showed alignment within 2-3 thousandths, about as good as before, but done far quicker with far much less aggravation.

Lesson is that if you have a defectively drilled rear trunnion it may not make it impossible to get good alignment on your Mark V but it may make it a heck of a lot more difficult.

Al

[reible]

I too got one of the defective parts.

My solution is posted here,

http://shopsmith.net/forums/showthread.htm?t=4458

Just another option you might want to check out.

Ed