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Straight shank arbor vs R-8

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Aukai

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#1
Since I have been looking at drill chucks, there are options for holding the chuck, taper, or straight. I have an R-8 taper for the mill, I also have the ER-40 collets. What are the advantages/disadvantages with each for a drill chuck?
 

Alexander McGilton

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#2
You want to reduce the number of fittings from the spindle to the tool when ever possible. Those straight shank arbors are often places in the turret of a turret lathe or cnc lathe, in a ground hole with set screw. For your situation, you should use a direct adapter from R8 to Jacobs tapper then the chuck if not a dedicated R8 chuck.
 

Aukai

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#3
That is inline with my thinking, thank you.
 

mikey

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#4
To my way of thinking, a drill chuck is not a precision tool holding device and a drill is not a precision cutting tool. Therefore, run out is not a major concern as long as it isn't ridiculous. This question really boils down to head room and speed of installation, which favors a straight shank vs having an integral shank. It is a major pain to have to undo the drawbar all the way to remove an integral shank chuck and it takes more space to get the thing out and replace it with the next thing. A straight shank just needs the drawbar to be loosened and given a simple tap to loosen the collet and the chuck is out.

Integral chucks are fine. Their advantage is accuracy because the shank and chuck body are machined in the same operation. When used in a precision high speed spindle, this matters. When put into the spindle of a hobby machine and standard jobber drills are used, I'm not convinced it makes a whole lot of difference.

For myself, I prefer a chuck that allows me to install an arbor of my choosing. For my mill, that will be a Tormach TTS straight shank arbor for the speed of removal and installation. It is also pretty accurate for what that's worth.
 

Aukai

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#5
Very good points,I have my worries of a straight shank having the potential to spin. I do not know how likely that would be, I just do not have the experience to know. One of my theories is that while the better brands are touted to be accurate, and this is negated in a hobby machine, their holding quality is also on a better level. Again only my theory....
 

mksj

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#6
Depends on your setup, I prefer an integrated R-8 arbor on most of my chucks, with a power drawbar it is quick to change chucks/tooling. The downside is the head needs to have more clearance height to remove the arbor. I often use my chuck to hold an end mill, so maybe a bit lazy, but it makes quick work when frequently changing bits, drills etc.. My chucks (both keyless CNC and CNC keyed) all have a TIR of under 0.001", maybe it also is that I am not a big fan of R-8 collets when trying to get endmills in and out with a power drawbar. They are wickedly sharp and even a small twist and they can do damage to your fingers. One reason why when using R-8 collets for end mills I always hold them in a towel when clamping up on it with the power drawbar. I have also had them kick out with the collet and fall on the table. The CNC keyed chuck is very rigid and quick to change cutters/drills. A TTS system is very nice but expensive. Matter of preference.

ER-40 for drills, really do not see the need or hassle, a standard chuck works just fine an is much quicker. Run-out is less of an issue relative to the drill bit. I would use an ER system for end mills, but not for drills. Also something to consider, ER collets come in increments, their range is more limited then what they claim, toward the limits of their range they become quite inaccurate, in particular using a metric set for imperial size tooling. They are also slow and somewhat awkward to be continually switching out collets for different size drills.
 
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mikey

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#7
I suppose a straight shank can spin. I've never had it happen but then again, I don't drill with huge drills. For me, I haven't had any issues with a straight shank.

Some folks like ball bearing keyed chucks. I have a US-made Jacobs Super Chuck 14N and its a really nice chuck but I hardly use it because I dislike keys. Its pretty accurate on my drill press, which has an accurate spindle, but since I only use it for larger drills the accuracy thing is not a major concern for me.

I mostly use Albrechts on my machines. Thing about Albrechts is the way they grab the drill. There is a spindle inside that moves up to touch the bottom of the drill. The jaws are keyed and physically fit inside the spindle body; as the spindle moves up, the jaws close on the drill shank and when the chuck locks, the drill is essentially a solid part of the chuck. Albrecht chucks are spec'd to have about 0.002-3" TIR and are spin-balanced to run at 10K rpm. On an accurate spindle, a spinning drill looks like its sitting still. For a drill chuck, Albrechts are more than accurate enough for me.
 

Aukai

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#8
Thank you very much. I do some work in the 5/8-11/16 reduced shank area, and MS plate, so looking at the best option. Then there are the annular cutters too, which I have a few..
 

MrWhoopee

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#9
I like a straight shank myself, and I cut them down to about 1-1/2 in. long. I hate cranking the knee up & down. I never hold anything larger than the chuck's rated size, S&D drills are held in a collet. Reduces damage to both the drill and the chuck.
 

mmcmdl

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#10
Very good points,I have my worries of a straight shank having the potential to spin. I do not know how likely that would be, I just do not have the experience to know. One of my theories is that while the better brands are touted to be accurate, and this is negated in a hobby machine, their holding quality is also on a better level. Again only my theory....
Mike , highly un-likely you would ever spin a straight shank in a collet . I've never had one spin in my shop time and I've done some pretty crazy things . I think it was mikey that said with your straight shank , you just have to loosen your draw bar a hair and tap it and that chuck comes right out . True . Fast and easy . That R-8 shank has to fully loosened and removed . Takes some time to do . I guess it's a matter of what you want , what you need . A drill chuck is not considered a precise tool . It's meant for drilling , not milling , so minor runout doesn't mean a hill of beans . Now if your drill chuck looks like a fly cutter while turning ………………………, well , make a fly cutter out of it ! ;) Plus , whatever you have in that chuck would spin long before the chuck itself would . Dave
 
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ttabbal

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#12
I had the same question a while back when I got a mill. I decided to go with straight shank as I don't expect accuracy from a drill. TIR is still under half a thou holding a ground rod in the drill chuck. I figure the drill bit is likely less accurate than that anyway and it means I can hold it in R8 or ER40 collets, whatever I'm working with at the time. I usually leave the ER40 chuck in there as I have more collets for that style, but it's nice not to have to switch just to drill.

I've never had one spin, but I'm careful about tightening the collet properly.
 

ddickey

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#13
And when you eject your straight shank 9 times out of ten you're going to change out the collet anyway.
 

Aukai

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#14
Thank you everyone for my continuing education.:eagerness:
I did see a vendor stating made in USA for a Jacobs chuck that had a simple USA , but no Hartford anywhere to be seen.
 

bhigdog

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#15
I have both R-8 and straight shank. If I'm going to mill then drill I try to use an end mill with the same shank size as my straight chuck. Never saw a difference in the use of either. Never spun the chuck. That said, when I'm drilling in my BP I'm quite aware of chip load and often sneak up to final size................Bob
 

mikey

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#16
I meant to mention that I've taken to using Blair rotabroaches for larger holes in steel plate. Much better than a S-D bit in my opinion. Plus, the rotabroach arbor fits in my 1/2" drill chuck.

All sorts of ways to spend money, eh?
 

Aukai

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#17
I have the slugger kit, and other sizes of annular cutters also, I do like them. Whew....:)
 
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