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JT3 confusion

slow-poke

slow-poke

Ultra Member
I use a lot of 3/4" TTS tooling It's just more convenient to simply loosen the drawbar a couple of turns rather than remove the entire R8 arbor.

I have a JT3 drill chuck presently mounted to an R8 arbor. It would be more convenient to replace the R8 arbor with a 3/4" stub type arbor, so I can swap in the drill chuck quickly.

Looking at JT3 to 3/4" arbors, I get images of arbors with this minuscule looking JT3 end, I measured the JT3 taper as is it exits my drill chuck at 0.815", the images look like ~3/8"?

I'm obviously missing something?
JT3.png
 
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I went through this before. I should look before I type. Is it possible they are inferring Jarno Taper as opposed to Jacobs taper?
To confuse matters more I've heard of Japan Taper, but there is no such thing. But Japan does use Jarno a lot
Fun fact: Jarno have the same taper angle regardless of size. Jacobs have different tapers depending on size

1735919264535.png

1735919352908.png
 
I don't trust the pictures either. To most of the people making the listing, they have no idea what the item is, or what it does, it's simply text on a screen, and the find a stock image that looks like the object because they're too effing lazy to take one out of the package and take details photos of the actual object. Sometimes you might actually get an MS Paint picture with text and dimensions on a stock photo, but it's obvious that it's not the correct item or scale. In a debate about refunds, it's the text description that is master anyway.

I also use my TTS tooling in the manual mill a lot too. It's so much quicker, and better for smaller tooling IMO. I'm sure at some point there is a tradeoff of rigidity, but I don't really push things that much at home so I haven't run into that wall yet. Not really noticeable with smaller tooling anyway, and the extra stickout is actually beneficial for clearance to fixtures and sight lines. I use my 1" apkt TTS stick tool quite a bit and it's never been a problem either. My 2" face mill is an r8 arbor though.
 
Jarno taper, that's it.

So JT3 is not actually a standard there are small JT3's and big JT3's who would have expected that?

I'm glad whoever comes up with these "standards" doesn't work on the space shuttle.

I'm going to trust the pictures.

Much appreciated.
 
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