Caliper question

[eliasbboy]

I'm so sorry for all the questions but it seems as if the more I learn the more questions I have.

I would like to use my calipers to get a better fit and eventually turn between the centers, but besides the digital calipers I'm not 100% clear on their usage.

I have a pair of double ended calipers as well as digital. Should I just use the digital? As far as the double ended ones, they're tapered so even if the size is close they'll still slide past the piece with a tug.

When sizing them, should they slide over the piece will little resistance, or NO resistance?

 

[Randy Simmons]

If you are turning on a mandrel, I would just advise using bushings. They are precision made for the specific kit you are using.

For turning between centers, again, there are bushings for that. But if you are REALLY into using calipers, here's the breakdown:

Digital calipers are probably going to be the most accurate. But, they will loose battery over time and, as with all electronics, the only guarantee is that they will screw up.

Mechanical calipers are also very, very accurate nowadays. The only problem is that they rely on the user to be that accurate, and when it comes down to it, you're just eyeballing.

Just IMO. Cheers,

Randy

 

[Lenny]

When I hear or speak of digital calipers for pen turning this is what I think of ...
Turners Select Fractional Display Caliper | Shop Supplies | Craft Supplies USA

Is that what you are talking about?
I use them to measure parts and double check the bushings. Turn close to the bushings then remove the bushings and continue turning checking with the calipers till the desired size. They are also great for checking tube length before and especially after using a barrel trimmer (or whatever alternative method you use).

 

[Jim Burr]

That's what I use Lenny. Also have a dial caliper, but I find it easier to read the digital.

When I hear or speak of digital calipers for pen turning this is what I think of ...
Turners Select Fractional Display Caliper | Shop Supplies | Craft Supplies USA

Is that what you are talking about?
I use them to measure parts and double check the bushings. Turn close to the bushings then remove the bushings and continue turning checking with the calipers till the desired size. They are also great for checking tube length before and especially after using a barrel trimmer (or whatever alternative method you use).

 

[eliasbboy]

When I hear or speak of digital calipers for pen turning this is what I think of ...
Turners Select Fractional Display Caliper | Shop Supplies | Craft Supplies USA

Is that what you are talking about?
I use them to measure parts and double check the bushings. Turn close to the bushings then remove the bushings and continue turning checking with the calipers till the desired size. They are also great for checking tube length before and especially after using a barrel trimmer (or whatever alternative method you use).

That's exactly what I have. Glad to know I'm using the right tool at least.:biggrin: Thanks!

 

[mredburn]

I have both the digital and manual dial calipers. I give my dad the dial one when he needs one to keep him away from my digital set.:biggrin: One advantage of the digital is I can switch from metric to imperial (inches) at the push of a button. That is a great advantage on its own for me.

 

[azamiryou]

I like the dial set better, I'm an analog kinda guy I guess - I prefer analog watches and clocks, too. My dial has two needles, one for imperial and one for metric.

Is the double-ended set one that's all curvy and kinda like scissors? I think those are for checking wall thickness of bowls and hollow forms.

For final sizing, I avoid sliding on the piece at all so the metal calipers don't scratch it. I just close on the barrel to get a reading, then open again to come off the barrel.

If I don't have a bushing for getting close, I'll add 20 thou or so to the target size, set my caliper, and go for clearance... tight or loose doesn't matter, I'm just aiming for that range from the target size to the caliper size to let me know I'm close (but not too far). Once I've gotten it down within that 20 thou range, I switch to taking measurements as above.

 

[Joe Burns]

I use the same calipers Lenny posted. The process I use is:

1. Measure the pen components first before you start to find the actual size you need.
2. I measure next to the bushings as I turn so I get an idea of where Im at.
3. When close to the bushings I put the tools down and sand to my finish size, checking as I go with the calipers.
4. Be sure to allow for the finish you are going to be using

I use the same process whether I turn on a mandrel or between bushings.


Joe

 

[its_virgil]

With all due respect, I have not found this to be true...not from any supplier. I have had bushings with the hole and outside circumference not concentric, bushings where the shoulder that fits into the tube to be too large or too small, larger diameters not round, larger diameters not close to what they should be, and probably other problems I've forgotten about. Most bushings are within tolerances, what ever that is. But many are way too far off to use as the final sizing authority.

I consider bushing to be a "get me close" gauge and a "hold the tube and blank on the mandrel" tool. I measure the parts of every kit with calipers and try my best to match the blank's diameters to those measurements.

Do a good turn daily!
Don

If you are turning on a mandrel, I would just advise using bushings. They are precision made for the specific kit you are using.
Randy

 

[eliasbboy]

As always I appreciate and will use all the answers and advice given.

I hope someday I'll be on the GIVING end of advice.

 

[randyrls]

I tend to agree with Don.
One trick with digital calipers is to set the calipers on the fitting and press the "zero" button. Now when you apply them to the barrel, the reading shows how much more you need to take off. Don't depend on the fitting size being identical from pen to pen. Plating thickness can vary depending on the plating and even with identical platings.

 

[plano_harry]

I like Randy's idea but I use mine differently, of course. When I get close to the bushings, I measure my part and lock the slide on the digital, then turn off the display. I can usually drop the jaws over the bushing next to the barrel. When I can slip it from the bushing just onto the barrel, I am done. Seems to allow enough for my finish thickness as well.

 

[Joe Burns]

Im going to have to try that. It sounds so simple and effective.

Joe

 

[azamiryou]

I usually work on both ends of the barrel at the same time, so zero-setting or locking to a setting doesn't work for me. Even if it's a pen style where both ends of the barrel are nominally the same, the actual measured components usually aren't. (I suppose it would work to set it for the larger diameter, then after that's reached switch it to the smaller and just work on that one end.)