How Precise are you?

[dusty]

This is just an exercise for fun and your own edification.

Cut a piece of wood (preferably 1/4" thick or greater) and at least 16" long. Make that cut 3 1/32" wide. Again, 3 1/32" (3.0325") wide.

Once you have it cut, clean your glasses and put them on. This eliminates all possible excuses.

Now measure the width (3 1/32") of that board in at least six different locations. I would suggest each end and in the middle then flip the board over and do it again. Record your readings as you do them.

If the readings seem unusual, maybe even unbelievable), do more readings at different locations just to convince yourself that you don't need new glasses.

Are the results identical? (You don't have to answer.) How much do they deviate? (Again, you don't have to answer.) Are you curious as to why the results are what they are? I certainly was.

Now, if you have a Mark V (any version), raise the table to clear the blade, remove the table insert and replace it with the piece of wood you just cut.

Does that piece fit snugly into the table cutout. No wiggle room.

[pieceseeker]

I haven't experienced much of this yet (beginner), but reading how clamping, miter sleds and feather boards will give you much more consistant results. It does make sense. Clamping in a sled for crosscuts or feather boards for ripping will result in even pressure against the fence all the way through the cut. Obviously, if the saw isn't set up as precise as possible, all bets are off. Pushing the wood through against the fence freehand just won't "cut it".

[dusty]

I haven't experienced much of this yet (beginner), but reading how clamping, miter sleds and feather boards will give you much more consistant results. It does make sense. Clamping in a sled for crosscuts or feather boards for ripping will result in even pressure against the fence all the way through the cut. Obviously, if the saw isn't set up as precise as possible, all bets are off. Pushing the wood through against the fence freehand just won't "cut it".

Absolutely!! However, not all cuts demand precision and the trick is to determine when you MUST clamp and/or use feather boards to get safe and suitably accurate results.

I use a sled a lot but I hardly ever clamp in the sled. That is one of the main advantages of the sled. The work piece is less likely to shift position. However, again it is dependent on the situation. Long pieces are difficult to control even on a sled. In that case, clamps are an appropriate solution.

AND - Just how precise do you need to be.

A good sled, once aligned, will hardly ever get out of alignment but it pays to check every now and then.

[robinson46176]

I use a measuring stick a lot that is 8' long and marked off in 1 foot increments with a Magic Marker... Does that tell you anything about the level of accuracy I demand?


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[robinson46176]

OK, kidding aside, I generally only use that stick checking for fit when re-arranging the shop. Something I do almost daily.
If I was making that cut, first off I would not measure it with any kind of rule. I would use dividers set to the width of the opening and set the fence by that. I adhere as firmly as I can to the rule "never measure when you can superimpose". I was taught that many many years ago.
When cutting multiples I cut one and mark it as "pattern" and use it for all of the next cuts.
I also like the concept of "story sticks".


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[dusty]

OK, kidding aside, I generally only use that stick checking for fit when re-arranging the shop. Something I do almost daily.
If I was making that cut, first off I would not measure it with any kind of rule. I would use dividers set to the width of the opening and set the fence by that. I adhere as firmly as I can to the rule "never measure when you can superimpose". I was taught that many many years ago.
When cutting multiples I cut one and mark it as "pattern" and use it for all of the next cuts.
I also like the concept of "story sticks".


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I understand and to a lesser extent do the same as you do. I disagree, however, when you say that you do not measure. You may not use a ruler or tape measure but, IMO, you do measure. Your ruler is annotated differently than mine but your story board or story stick is your ruler.

When I spread my hand as far as I can, the distance from the tip of my pinky to the tip of my thumb is 8 1/4". If I spread my hand in that manner to position a cut, 8 1/2" from the end of a board, have I measured. I say yes. No ruler but I measured.

[nuhobby]

I am working on another machinist-chest restoration lately. Many times I will see the original back panel has warped or cracked, since the grain orientation wasn't well-thought-out decades ago at the factory assembly. During the rebuild I'll replace a large back-piece with some lapped, adjacent strips that can breathe slightly during humidity changes.

Anyway -- it's too much of a hassle to power-cut to a very precise length when it's an exposed butted-joint for instance. I deliberately do this:
- Cut a piece too long
- Join / dowel / glue it to the back of the chest
- Take off the excess with a crosscut handsaw
- Trim the end-grain with a block plane. This is where you can trim by 0.001" increments without cussing . However the plane has to be really sharp, and a thick-bladed plane will beat a thin-bladed plane. It's really fun in a situation like this to "take the tool to the work" rather than "take the work to the tool."

[fjimp]

Remember you asked. I would be afraid to measure anything today. I am planted in my recliner with arm in a sling and consuming my share of pain meds. Nuff said. Jim

[saminmn]

Remember you asked. I would be afraid to measure anything today. I am planted in my recliner with arm in a sling and consuming my share of pain meds. Nuff said. Jim

Good luck to you!! Hope everything was total success.

[robinson46176]

[quote="nuhobby"]I am working on another machinist-chest restoration lately. Many times I will see the original back panel has warped or cracked, since the grain orientation wasn't well-thought-out decades ago at the factory assembly. During the rebuild I'll replace a large back-piece with some lapped, adjacent strips that can breathe slightly during humidity changes.

Anyway -- it's too much of a hassle to power-cut to a very precise length when it's an exposed butted-joint for instance. I deliberately do this:
- Cut a piece too long
- Join / dowel / glue it to the back of the chest
- Take off the excess with a crosscut handsaw
- Trim the end-grain with a block plane. This is where you can trim by 0.001" increments without cussing ]



A number of years ago we were headed to a daughter's home near Knoxville TN (She now lives in MT.) and we wanted to first go to Crossville TN. We cut off of I-75 near the south edge of KY and zig-zagged westward down into TN mostly just wandering and looking and on a lot of back roads. We soon started seeing building after building, mostly sheds and small barns with the boards all sticking out uneven on one end. These were rough-sawn lumber sheds with the boards running horizontal. It was obvious that they put the boards even at one end (usually the left end and when they got to the other corner post they just let it stick past. On the next wall around the corner the board ends were butted against the sticking out pieces at the corner post and the other end stuck out all uneven at the next corner post. I first assumed that they had planned to trim the other end off when they got done but many of these structures were pretty old and the boards were still sticking out all jagged. We began to wonder if they even owned a saw. It was fairly evident that most didn't own a level.


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