Toolholding: R8 And Drill Chucks...?

EmilioG

EmilioG

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Is it OK to use a 1/2" straight shank JT3 arbor inside an R8 1/2" collet with a Jacobs drill chuck for
drilling holes and tapping? or should attach an r8 JT3 "permanently" to the Jacobs 14n?
 
I have bouth and thay bouth get used. Just depinds what I am doing at the time.
 
One advantage of using a straight shank is you can use a relatively short one in your R8 collet. This allows you to install or remove the chuck without having to lower the knee as much or as often.

Darrell
 
I'm a sucker for more tools. I expect to have R8 tools permanently set up, center drill. comes to mind. The business of changing collets to change tools seems counter-productive. I won't have a mill with an R8 spindle for at least a month, but I've already got a drill chuck and (Criterion type) boring bar holder. Planning on getting any number of holders.
 
T Bredehoft said:
I'm a sucker for more tools. I expect to have R8 tools permanently set up, center drill. comes to mind. The business of changing collets to change tools seems counter-productive. I won't have a mill with an R8 spindle for at least a month, but I've already got a drill chuck and (Criterion type) boring bar holder. Planning on getting any number of holders.
Click to expand...

There are lots of preferences out there. Nothing wrong with your thinking. The logic behind the straight shank, besides height, is that if you maximize the amount of tooling with the same size shanks, you only have to loosen the drawbar, not constantly remove the entire collet. Add a power drawbar and that increases efficency the most.
I just swap center drills, drills and countersinks using the same chuck.

Darrell
 
swap center drills, drills and countersinks using the same chuck.

That's probably what I'll do until I get a enough R8 holders (that I can rationalize.)
 
I checked the height of the 1/2" shank plus 1/2" R8 collet and just using the r8/JT3 and there is not much difference in height.
 
EmilioG said:
I checked the height of the 1/2" shank plus 1/2" R8 collet and just using the r8/JT3 and there is not much difference in height.
Click to expand...

That is why to gain a advantage, you shorten the straight shank. It only needs to be about 1 1/2" long. It might not seem like much but sometimes being just a inch or two shorter is the difference in having to move the knee to change tooling or not. It isn't about the drill chuck being shorter after it is installed If you do not have to remove the collet every time you change tools it saves time over completely unthreading the draw bar and rethreading it in to the new holder.
As always YMMV.

Darrell
 
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