Collet tool holding question-10mm vs 3/8"

[rwm]

I am considering getting a 3D taster for the mill. The age old metric vs imperial issue rears its ugly head! The Haimer taster uses a 10mm shank. They also make 3/4". Tschorn makes a 1/2" shank. I would likely be using a 3/8" end mill for most operations. It would be very convenient not to have to change the collet out. Could I use a 10mm R8 collet to hold a 3/8" end mill? Or could I use a 3/8" R8 collet to hold a 10 mm shank? I could accept a few thou of error on most projects. Any other good ideas? (Don't say power drawbar because I don't have compressed air!) I suppose I could buy new 10 mm endmills?

Robert

 

[ttabbal]

R8 collets don't really move much. They are designed for one dimension. I've seen a couple of sources say +/-0.002. So you can't put 10mm in 3/8.

Changing collets is pretty easy on R8, but if you really don't want to.. How about a collapsing bushing? Should work well enough for a probe.

 

[akjeff]

10mm and 3/8" are nowhere close enough together for an R8 collet to cope with. If all you have are inch R8 collets, I'd get the 3/4" shank and just switch collets. JMHO. Another option are ER series collets via ER to R8 adaptor. They give a lot more leeway on tool size variance.

 

[rwm]

Thanks for chiming in guys. That's what I figured. I think I will buy the metric shank taster (either 10 or 12mm) and then buy a couple of appropriate end mills to avoid collet changes. That makes the most sense. Can you tell I'm lazy?

Robert

 

[akjeff]

Don't know if such a thing exists, but maybe there's a 3/8"( and other sized ) end mill with a 3/4" shank? Then, you could get the inch model taster, and not have to change collets?

 

[RJSakowski]

Thanks for chiming in guys. That's what I figured. I think I will buy the metric shank taster (either 10 or 12mm) and then buy a couple of appropriate end mills to avoid collet changes. That makes the most sense. Can you tell I'm lazy?

Robert

The taster will have to be zeroed to operate properly. If there is any runout in the spindle or collet, you will want to install the taster in exactly the same orientation each time. My preference would be to use a 10mm end mill holder and permanently mount the taster. That way, the key in the R8 socket will insure that the taster goes in the same orientation each time.

Unfortunately, 10 mm R8 end mill holders appear to be more scarce than hen's teeth. second choice would be an inch shank and end mill holder. Since the taster would be permanently mounted in the end mill holder, it really doesn't matter what diameter you use.

 

[rwm]

RJ- That makes this sound a lot more complicated. I had no idea the orientation would be critical. What accuracy are you talking about here? I can live with being off 2 thou. I assumed that R8 collets were at least that accurate regardless of orientation? I am wrong on that?
R8 10mm are not rare on Amazon?
Robert

 

[NC Rick]

I have been starting to collect metric collets in R8 for my mill. I find I need them anyways. Owning a 10mm collet would not be a bad thing. It doesn't need to be a hardinge brand.

 

[rwm]

How in the world would you zero a Haimer anyway, since they are purported more accurate than other devices? You would not have a standard to compare it to? It would not make sense to compare it to a mechanical edge finder. I guess you could approach a gauge block from both sides and compare to the DRO or something like that?
Robert

Edit: Here's how you calibrate it! I don't really like the term "calibrate" for this. Really, you are just aligning the tip of the probe to be concentric with your spindle axis. To me "calibrate" means you adjust the internal accuracy of the device. I would call this "alignment".

Robert