Tolerance


Saw-Loco

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I have been playing with this for a while and I am looking for some feedback.

When I first got into woodworking, I was told to get close tolerance for marking to use a sharp blade.  But working with walnut and other darker hardwoods I find I have a hard time finding the scratch when it comes time to cut.  So now I use a .5mm pencil, and is easier to see, but the tolerance is not as good.

Since my tape measure is mostly 1/16" I figure the pencil is as close as I am going to get.

What do the accurate ones out there do?

Thanks

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Stop blocks.

If i have any distance that needs to be repeated more than once i set up a stop block. The problem arises when I don't plan things out and needing to remake a cut. This is still easy by putting the piece you need to match on the saw and then set the stop block again.

I've started cutting all the pieces i need in a preliminary fashion 1/2" long so i can make sure i have all the parts i need. Then i go back and batch cut them to length. It makes things a bit more manageable planning wise. Being able to plan is pretty key. Figureing out where you need 100% accuracy and where you can fudge 1/128th makes a difference as well. Like on a 6 ft rail for a table if they aren't exactly the same size the length is enough that 1/128th or even 1/64th isn't noticeable.

For hand tool work there is the blue tape trick.*

This doesn't have to be used JUST for dovetails i can be used for a multitude of things. On walnut it's probably the best option out there accuracy wise.

*The above link goes directly to a specific post. There are more on the forum searching may be fruitful but we love our blue tape here and it gets mentioned a lot.

 

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+1 on white pencils for dark wood.  I get them at a local art supply store, but I would imagine they can be found a lot of places.

Another vote for stop blocks, if I need many parts that are the 'same'.  At some point, the absolute size doesn't matter (think "relative dimensioning").

 

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If you are using a tape measure, marking with a knife is pointless. As you pointed out, the resolution is too low for accuracy.

I usually reserve knife marks for hand-cut joinery, that is gauged from an existing part, not measured with a rule of any kind. For machine-cut parts, stop blocks are awesome. I use a steel machinist's rule that has scribed markings down to 1/128" to set the block, then the block sets all subsequent cuts.

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8 hours ago, wtnhighlander said:

I usually reserve knife marks for hand-cut joinery, that is gauged from an existing part, not measured with a rule of any kind.

That is very different to my own approach. I use a knife mark for most things to do with hand-cut joinery no matter how I determine the cut position. For example, the cut line for a tenon shoulder is usually something I typically measure with a rule (if I don't already have another rail to match) and I always mark it with a knife. I find I get a cleaner and more accurate cut that way.

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17 hours ago, Jfitz said:

+1 on white pencils for dark wood.  I get them at a local art supply store, but I would imagine they can be found a lot of places.

Another vote for stop blocks, if I need many parts that are the 'same'.  At some point, the absolute size doesn't matter (think "relative dimensioning").

 

 

15 hours ago, Barron said:

You can also rub chalk into the line left by the marking knife/gauge. 

Sounds like a good application for those chalk pencils.  I like this

14 hours ago, wtnhighlander said:

If you are using a tape measure, marking with a knife is pointless. As you pointed out, the resolution is too low for accuracy.

I usually reserve knife marks for hand-cut joinery, that is gauged from an existing part, not measured with a rule of any kind. For machine-cut parts, stop blocks are awesome. I use a steel machinist's rule that has scribed markings down to 1/128" to set the block, then the block sets all subsequent cuts.

I obviously don't have all the finer hand tools.  Where do you source out these gauges and scales?  I assume it is not Amazon. 

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4 minutes ago, Mark J said:

Just going to mention that marking with a knife or cutter also cuts through some wood fibers which can help reduce tear out.  

I have heard that, but I try to use sharp blades and have not noticed a difference.  Is the point then to cut on the line, or on an edge so that one side of the cut takes advantage or the precut fibers?

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1 hour ago, Saw-Loco said:

I appreciate all the suggestions, but it raises another question.  When I hear stop block, I picture a screwed or clamped piece on my saw or router table.  Is this what you mean or is there a different application that you can describe?

Here are a couple of my stop blocks one fance one crude. But yeah a block clamped to your workbench table saw sled miter gauge how ever it gets accomlished. More often than not my stop blocks are a piece of scrap and a clamp.

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10 hours ago, Saw-Loco said:

 

Sounds like a good application for those chalk pencils.  I like this

I obviously don't have all the finer hand tools.  Where do you source out these gauges and scales?  I assume it is not Amazon. 

Lots of the stuff comes thru Amazon, you just have to know where to look.

Harry Epstein is a good place to find quality tools at a good price.

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Harry Epstein is a good source that I have used for years.

Conventional wood bodied White pencils and colored pencils are bad about being hard to keep sharpened to a fine point. I found a set of colored pencils at the dollar store for those adult coloring books. Plastic body mechanical pencils with fairly thick leads in multiple colors and a little sharpener on each top. Very low price and surprisingly good results. They even had sets of spare leads included plus more for sale separately. I use them to color knife cuts for visibility. I also use a magnifying headset like jeweler's use for accuracy with aging vision, especially late in the day.

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21 minutes ago, K Cooper said:

Where do you find those? 

I'll send you a couple of mine Coop, i already colored in the easy parts:)

 

12 hours ago, Saw-Loco said:

Sounds like a good application for those chalk pencils.

I use  Pica pencil that i picked up at Woodcraft, they have all different colors of lead and a built in sharpener but as @wdwerker has said most times it is soft and doesn't hold a fine tip without constant sharpening. the regular Pica lead is strong for marking on light woods and i use the white for rough marking and to color in the lines from my marking knife.

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On 10/13/2018 at 2:04 AM, Saw-Loco said:

I have been playing with this for a while and I am looking for some feedback.

When I first got into woodworking, I was told to get close tolerance for marking to use a sharp blade.  But working with walnut and other darker hardwoods I find I have a hard time finding the scratch when it comes time to cut.  So now I use a .5mm pencil, and is easier to see, but the tolerance is not as good.

Since my tape measure is mostly 1/16" I figure the pencil is as close as I am going to get.

What do the accurate ones out there do?

Thanks

It is not only blue tape that is helpful when working to close tolerances, but the use of marking gauges to transfer measurements, rather than re-measuring and marking each time. Keep a few marking gauges, such as wheel gauges, set up with the frequent sizes you need. It is common that I use about 5 at one time.

Regards from Perth

Derek

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