Interapid for barrel work

[V35]

I like the Mitytoyo 513 series because I can reach into a rough drilled hole and indicate the throat in my Benchrest Chambers without such a long stylus.

https://www.grainger.com/product/4C...W2E3fwLZeSrEBTqcvAiEsrrY9UvBUBPhoCd1MQAvD_BwE

I have one of those, works well when I have used it. The only issue is the tiny dial is hard for me to see.

 

[Sniperhandle]

I'm no expert and I know we are only measuring relative movements. These indicators need a 12 degree angle to read correctly, with the vertical you're going to be at 90 degrees give or take.

I own the regular one that runs the dial "backwards" and don't have a problem with it.

Yes, For dialing in a barrel I just think of them as a "Movement Clock" you aren't really measuring anything, Just waiting for the indicator to stop moving and stay in one place, Other than bouncing over the lands.

That's why in my opinion for that application, It wouldn't matter to me if the indicator was a metric indicator, Which at my age I have no use for, But it wouldn't really matter, Because it's just a "Movement Clock"

 

[LVLAaron]

Yes, For dialing in a barrel I just think of them as a "Movement Clock" you aren't really measuring anything, Just waiting for the indicator to stop moving and stay in one place, Other than bouncing over the lands.

That's why in my opinion for that application, It wouldn't matter to me if the indicator was a metric indicator, Which at my age I have no use for, But it wouldn't really matter, Because it's just a "Movement Clock"

Agreed. I haven't seen any information about how "inaccurate" they are if they aren't at 12 degrees so it was just a word of caution.

 

[ELR LVR]

Yes, For dialing in a barrel I just think of them as a "Movement Clock" you aren't really measuring anything, Just waiting for the indicator to stop moving and stay in one place, Other than bouncing over the lands.

That's why in my opinion for that application, It wouldn't matter to me if the indicator was a metric indicator, Which at my age I have no use for, But it wouldn't really matter, Because it's just a "Movement Clock"

I do like to measure the depth of grooves, and ensure they are all the same depth of cut
I have seen one of the lands be different once,
If you got say a 5R, and every single one of the grooves moves .0035" deep, except one moves .0030"
That cannot be your setup is off.
if that barrel didn't shoot good, would be a good reason to send it back

 

[Sniperhandle]

Over on the Hobby Machinists forum, Matt The Muppet was selling some metric indicators last year for a very good price, I almost bought a couple because they looked to be in good shape and for dialing stuff in it just doesn't matter. But then I remembered a couple of used indicators I have bought before and the issues I had with them. It's not worth it, I will buy New old stock. But not used anymore.

I have one Interapid, I would like to have another one someday.

 

[LVLAaron]

I recently got a Mahr. It's equally impressive.

 

[jeffp400]

So Its official Im tired of fighting with the tools I currently have and Im wanting a interapid indicator dedicated for barrel indicating only. What is the model that is best for the task.

Pm sent

 

[CCM]

Agreed. I haven't seen any information about how "inaccurate" they are if they aren't at 12 degrees so it was just a word of caution.

The amount of cosine error depends on the stylus angle. At 60 degrees, the error is 50%. An easy way to figure out the error is to use a calculator. Start with what your dial says, e.g. .0005". Now hit COS followed by the angle.

.0005xCOS(35)=.000409

This cosine error can also be compensated for with a teardrop contact point.

Now, since these DTIs are being used as comparitors and not for raw measurements, none of this really matters.