Accuracy question

[RFGuy]

When contemplating using the 5 ecut method, one must consider the purpose(determining the amount of correction to obtain square cuts with a fence on a cut off sled. Other scenarios are not likely relevant.

I cannot conceive using 5 cuts to align a rip fence.

For checking a miter gauge squareness, a straight edged workpiece against the miter gauge fence, then a single cut, then stand the two ends just created with the straight edges parallel with each other. Observe the amount the straight edges misalign as the distance from the cut increases.(0 = square)

JPG,

Thanks. All good points and I agree with you. I was hesitant to bring up the 5 cut method, but it was mentioned above so I referenced it. My understanding of it is just that it shows that systematic errors tend to be additive (but not always ). The 5 cut method is talked about A LOT on YT and typically with regard to checking the squareness of a new crosscut sled. I prefer using the best quality square or other measurement tool that I can afford. IF I understand what the OP describes, it seems like an offcut is being measured with a caliper and an assessment of squareness derived from it. What we don't know is how square the object was before being cut so there is error due to this. Also, don't know if the final "kept/saved" piece that was cut is actually square or not after the cuts. IMHO, a good quality square (even if it needs to be a large one to reference the full edge due to size of laminate being cut) should be the first tool to assess accuracy of cut afterwards, not a caliper used on the offcut. Am I missing something? Not trying to be critical of the OP or any of the discussion here, but rather trying to understand why an offcut is being measured to assess "accuracy"?

IF I am getting this wrong, a picture would really help me to understand what is being described by the OP. Thanks.

[dusty]

When contemplating using the 5 ecut method, one must consider the purpose(determining the amount of correction to obtain square cuts with a fence on a cut off sled. Other scenarios are not likely relevant.

I cannot conceive using 5 cuts to align a rip fence.

For checking a miter gauge squareness, a straight edged workpiece against the miter gauge fence, then a single cut, then stand the two ends just created with the straight edges parallel with each other. Observe the amount the straight edges misalign as the distance from the cut increases.(0 = square)

JPG,

Thanks. All good points and I agree with you. I was hesitant to bring up the 5 cut method, but it was mentioned above so I referenced it. My understanding of it is just that it shows that systematic errors tend to be additive (but not always ). The 5 cut method is talked about A LOT on YT and typically with regard to checking the squareness of a new crosscut sled. I prefer using the best quality square or other measurement tool that I can afford. IF I understand what the OP describes, it seems like an offcut is being measured with a caliper and an assessment of squareness derived from it. What we don't know is how square the object was before being cut so there is error due to this. Also, don't know if the final "kept/saved" piece that was cut is actually square or not after the cuts. IMHO, a good quality square (even if it needs to be a large one to reference the full edge due to size of laminate being cut) should be the first tool to assess accuracy of cut afterwards, not a caliper used on the offcut. Am I missing something? Not trying to be critical of the OP or any of the discussion here, but rather trying to understand why an offcut is being measured to assess "accuracy"?

IF I am getting this wrong, a picture would really help me to understand what is being described by the OP. Thanks.

Well, if I wanted to make certain that I had cut off 3" would it not be reasonable to measure the cutoff to ascertain that.

Oh, you want to know if the work piece is 3" shorter than it was before you cut it. I guess thast would work too.

Whatever you measure - don't disregard the thickness of the kerf. My curoffs have been 3/32" off 3/32"far too many times.

[RFGuy]

Well, if I wanted to make certain that I had cut off 3" would it not be reasonable to measure the cutoff to ascertain that.

Oh, you want to know if the work piece is 3" shorter than it was before you cut it. I guess thast would work too.

Whatever you measure - don't disregard the thickness of the kerf. My curoffs have been 3/32" off 3/32"far too many times.

Dusty,

Yeah, but the OP was specifically asking about ascertaining accuracy AFTER they had performed an alignment on their 520, or at least that is how I understood their post. So, given this, does it make sense to measure the offcut? That is why I was confused because I believe the topic was accuracy after alignment.

[JPG]

OK! Why 5(five) cuts?

Well it eliminates the concern re original squareness of the test piece.

Cut one establishes a reference edge. cuts 2,3,4 create a potentially square rectangle.

All 4 corners should share the same angle.

Now the fifth cut creates a cutoff strip that if the 4 corners are not exactly 90° will not have parallel edges.

The effect of the corner angle is increased 4 fold.

By measuring the run out of those non parallel edges and using math to calculate the amount of movement needed to adjust the sled fence to produce square cuts is possible. Somewhat cumbersome but effective and uses a micrometer/caliper instead of a precision square.

Question remains how accurate is the adjustment made.

[RFGuy]

OK! Why 5(five) cuts?

Well it eliminates the concern re original squareness of the test piece.

Cut one establishes a reference edge. cuts 2,3,4 create a potentially square rectangle.

All 4 corners should share the same angle.

Now the fifth cut creates a cutoff strip that if the 4 corners are not exactly 90° will not have parallel edges.

The effect of the corner angle is increased 4 fold.

By measuring the run out of those non parallel edges and using math to calculate the amount of movement needed to adjust the sled fence to produce square cuts is possible. Somewhat cumbersome but effective and uses a micrometer/caliper instead of a precision square.

Question remains how accurate is the adjustment made.

JPG,

I agree with everything you are saying here, but the 5 cut method wasn't mentioned in the original post that started this thread. From the original post, my understanding is 2 cuts were performed and then the offcut was measured. All of my comments on this thread have been related to this fact. The 5 cut method wasn't brought up until later in the thread. I still stand by my point of why make 1 or 2 cuts on a workpiece AND measure the offcut thickness down its length with a caliper? To assess accuracy of the alignment (and cut that was made), I still believe a precision square is best for this case. JMO.

After aligning my Mk V 520, I felt good about the results. However, last night I needed to use the table saw to cut exactly 1/8" off of both sides of a workpiece, such that the piece was 1/4" shorter but my laminations still centered.

...

Question - What is the standard for being square? Is this difference worth looking into or should I be happy with it?

[tfrayne]

I performed the alignment as per the Owner's Manual, and a few YT videos. I did not check it with any verifying cuts as of yet.

In building my crosscut sled, I needed to make two 1/8" cuts off of my fence (laminated walnut & maple) to get the proper height and to keep the laminations centered. I was slightly off on my measurement of 1/8'. Had it been correct, there would be no offcut.

I can see that the offcut I did have, is irrelevant. What counts is the workpiece.

While I am pretty sure the Mk V is aligned properly at this point, I will indeed re-check before I commit to locking in the crosscut sled.