Using Calipers

[bjbear76]

Has anyone done a tutorial or a Youtube video on using calipers instead of bushings? I know some of my older bushings are getting worn or out of round, and until I get new bushings, I thought I'd try my hand at using calipers to turn down my blanks. The problems I ran into were: 1) getting an accurate measurement on the pen kit (4 different places to measure on a cigar pen) and then 2) when trying to measure the blank, trying to get a reading on the very end of the blank. Since the profile of the blank is slightly curved, I tend to get a high reading which makes my finished blank proud of the kit. I couldn't find anything in the library or on Youtube, does anyone know of one or have any suggestions?

 

[mrcook4570]

Measure with the edge (side) of the jaws and place only enough of the mating surface in the jaws to allow to to close them to get the measurement.

 

[randyrls]

Has anyone done a tutorial or a Youtube video on using calipers instead of bushings?

I still use bushings, but don't trust them. Most of my bushings are TBC style. Here is my method:

With digital calipers, set the caliper on the fitting you want to match. Press the "Zero" button. This will make the reading show how much oversize the barrel is.

Now measure the barrel:
THIS IS DONE WITH THE LATHE STOPPED!
Open the caliper and place the caliper on the bushing with your finger on the barrel. Move the caliper just until it rides up on the barrel, then close the caliper on the barrel. Make sure that the caliper contacts the barrel on both sides and the caliper is perpendicular to the axis of the barrel. You can "rock" the caliper from side to side while pressing it closed. The minimum reading is the true reading.

As far as actual measurements go, I normally turn down the barrel until it is between .005" to .010" or so above the target size. I start sanding at this point with 320 grit paper and continue thru the grits up to 1000. Remove the barrel(s) from the lathe and finish. You will have to determine how thick the CA finish will be finally measure the completed barrel. I shoot for a finished target size of -000" to +.003".

 

[wouldentu2?]

My bushings have gotten sanded down over time now I can turn to less than the original bushing , sand , and then CA up to the desired dimension.

 

[cwolfs69]

the chart in the library has the dimensions very many of the kits out there that we all use. you can use these dimensions for your calipers without measuring the pen parts. works very well. i don't think i have relied on the bushing for my dimension in 2 years, about 2 months after beginning pen turning. now with my metal lathe, the bushings do nothing but hold the bland. i use the same bushings for all of the same size tubes no matter what the pen kit i'm using.
just a thought

 

[bjbear76]

Thanks for all the good input and advice!

 

[CharlesJohnson]

I always measure the pen parts and take notes. I find it varies from kit to kit.