Depth measurement

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Druid

Druid

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Dec 17, 2008
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I'm curious what folks use to accurately measure depth for "kitless" pens.
1. Do you use a depth gauge, metric ruler, other tool?
2. Who is the vendor (URL would be great) and what standard of accuracy is "acceptable"?



Look forward to seeing the info generated from this thread :smile:



Jim
 
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most of us use digital calipers. I have Mitutoyo
images


My standards of accuracy are more than most. I want things under .0015
 
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I use a digital caliper that I got from HF about 5 yrs ago. They have quite a few of them. I use the 68304. About 25 bucks. Its worth a look.
Paul
 
I've got a Mitutoyo and an HF, both 6" digital calipers. Some of us have also put DRO's (basically a digital caliper) on our tailstocks for measuring while drilling.

Mike
 
I use calipers mainly for measuring the diameter when creating a tenon size. For drilling holes I'll use the caliper just to draw a black line on the drill bit. Most of the depths you drill aren't very critical. The main one to worry about is usually dealing with the section because there is such a small area where the threads exist so you need to not drill too far from the front or the back. Drill bits are tapered so there really no accurate way to say exactly where the hole ends. I try to measure close to where the taper ends and the drill bit becomes flat but I'd be fooling myself if I claimed I could do that to 2 thousandths accuracy. If you drilled with an end mill bit maybe its a lot easier to determine the depth.
 
If you are boring/drill a hole mark the depth off on the bore/drill and put a stop collar on the drill at the required depth. This is easy and repeatable. Measure twice - cut once.
 
Your tailstock may be marked for approximate drilling depth, and the tpi of the tailstock lead screw will give you a very precice advance by counting the revolutions as you drill (i.e. 20 tpi will advance .050 per revolution -20 revolutions per inch- of the hand wheel and you can easily guestimate accurately to 1/10 revolution for .005 or better depth control.)

Assuming you're drilling on the lathe.

You can also make a simple depth gauge from small round stock like 1/8 metal rod and a sliding piece to go on it drilled for tight fit (or with a set screw) that will let you measure actual depth with a caliper if your caliper doesn't lend itself to direct use in the hole.
 
My tailstock is graduated in mm, with each full turn 1mm, so it's pretty easy to gauge to 1/4 mm (about .010) with just the tailstock. I also use a depth gauge and digital caliper when necessary. I just added a DRO to my compound slide which enables me to finish a drilled hole with precision to .001 or less (with a small boring bar). This is all in a metal lathe, of course. In my wood lathe I would probably just use the simple depth gauge.
Roger
 
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