Toolholding: R8 And Drill Chucks...?

My primary chucks for use on my mill are a 1/2" keyless chuck & a 14N, both with R8 arbors. The longer R8 arbors do not bother me. I do have a secondary 14N that I use for the mill with a 5/8" straight shank arbor (full length).

Some people like to shorten the straight shank arbor making it quicker/easier to change as mentioned. If you look inside a 1/2" collet there's only about 1.25" of contact area depending on the brand of collet. A genuine Jacobs 1/2" straight shank arbor can be cut in the middle relief area leaving about 1" contact area so the rest of the straight shank arbor is pretty much useless unless you use it to hang out from the spindle/collet nose. With R8 collets, the smaller the arbor is from true nominal size, the more the R8 collet will grip only towards the nose of the collet.

Another thing to consider & keep caution of. Jacobs Super Ball Bearing chucks are much heftier than other chucks in the same size range, mainly 14N chucks & larger. With a straight shank arbor on a 14N or larger, you should always take caution when loosening the drawbar on the mill. These chucks have some good weight to them, if your R8 collet did not lock in the taper, if you go to loosen the drawbar without holding the chuck in the other hand, the chuck can drop out of the collet causing damage to your vise, table, workpiece etc. I experienced this once, it wasn't on my own mill but I still felt terrible about it even though it was on a beat up BP, & learned my lesson. With a R8 arbor, this can not happen.
 
You are correct Will. I tested the grip force and my R8 1/2" collet holds the 1/2" arbor very tightly, even before
putting it in the mill collet holder. I'm going with the R8 jt3 though. But first I'm drilling and tapping for a set screw or bolt
to make it easier to remove in case there are no wedges around. Thank you all. Will you've been a great source of information.
Thank you for all of your kind and patient replies. And what a difference on the 14n with new jaws, it can grip really small drill bits.
and no light coming through the closed jaws.

Can you accurately check the TIR on an arbor or collet before installing a drill chuck?
 
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EmilioG said:
You are correct Will. I tested the grip force and my R8 1/2" collet holds the 1/2" arbor very tightly, even before
putting it in the mill collet holder. I'm going with the R8 jt3 though. But first I'm drilling and tapping for a set screw or bolt
to make it easier to remove in case there are no wedges around. Thank you all. Will you've been a great source of information.
Thank you for all of your kind and patient replies. And what a difference on the 14n with new jaws, it can grip really small drill bits.
and no light coming through the closed jaws.

Can you accurately check the TIR on an arbor or collet before installing a drill chuck?
Click to expand...

If you have a drill chuck with a strait shank you could put that on a vee block and hand rotate it whilst using a test indicator on a test bar held by the chuck.

Stuart
 
I have used both. Make sure to clean the inside of the spindle with a rag so both run true.
 
stupoty said:
If you have a drill chuck with a strait shank you could put that on a vee block and hand rotate it whilst using a test indicator on a test bar held by the chuck.

Stuart
Click to expand...

Will this method give an accurate reading? Isn't it better to have it in a spindle to read off the DTI?
I just want to check the arbor by itself first before pressing it on the chuck.
 
EmilioG said:
Will this method give an accurate reading? Isn't it better to have it in a spindle to read off the DTI?
I just want to check the arbor by itself first before pressing it on the chuck.
Click to expand...

The method Bill stated will give you a pretty accurate reading as long as the v-block being used is fairly accurate. Using a V-block will tell you how accurate just the arbor is without the error of a spindle & collet in the equation. But a mill's spindle should be pretty accurate so that should be good enough. Drill chucks aren't guaranteed to have an accuracy better than .002". Not that it's not possible, it just isn't common.
 
Jacobs_JT3_57 (1).JPG


is this a real Jacobs r8? I've never seen a Jacobs arbor with printing on the business end like in the photo. Seller says it's Jacobs but I think it's a copy with a Jacobs box. All the arbors I've seen from Jacobs have the printing in the middle part. Is it real?
 
EmilioG said:
is this a real Jacobs r8? I've never seen a Jacobs arbor with printing on the business end like in the photo. Seller says it's Jacobs but I think it's a copy with a Jacobs box. All the arbors I've seen from Jacobs have the printing in the middle part. Is it real?
Click to expand...

I'm not sure. I never purchased a Jacobs R8 arbor cause they're like $100! As for the Jacobs straight arbors & morse taper arbors, it's easy to tell the difference as they always have a relief in the center section of the arbor that black oxide & is where their markings are. The older made in USA arbors have the marking stanped in that area. The later ones made in England are etched instead of stamped. And the current ones made in Asia are also etched but don't have a COO on them.

I personally have never seen a Jacobs R8 arbor but it does seem odd & inconsistent that it's marked on the ground surface. I'm not saying that it your's not genuine but a genuine Asian made Jacobs arbor doesn't mean anything to me. I personally prefer & use the Pro Series R8 arbors from ABS Import Tools. They're very nicely made & have an nice electroless nickel plated finish. They're priced very well! The only time I will pay high dollar for an R8 arbor is for the Criterion arbors.

Img_0492.jpg

Img_1027.jpg
 
That R8 on Ebay, I would never purchase. I'm ordering the Pro Series from ABS.
I had a real R8 JT4 on a Jacobs USA 18n that I sold recently. The new Jacobs R8
say Made In England and are $90.00! Sears has them.
Llambrich looks like they make nice arbors and old EMT's are good if you can find one.
I'll stick with the $15 arbor for my needs. Thanks Will.
I show that Ebay R8 to say, beware of sheep in Jacobs clothing. :)
 
Just spoke with Apex Tools, maker of Jacobs chucks and arbors, and they told me that the arbors
are now made in Italy. They are not Chinese. So I think it's not so bad if you have the money to
use one of their arbors.
 
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