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View Full Version : Which ER system for drills?



IdahoJim
12-18-2010, 11:26 AM
MY Rockwell mill has a somewhat limited work envelope in the Z, so I sometimes can't fit a drill bit in under my big drill chuck. I'm thinking of getting an ER system so I can reduce the extension of the big Jacobs chuck by chucking drills directly in the collet. This would be for drills from, say, 1/8" to 1'2" or 5/8". My question is, which ER system do I want?
Many thanks for any advice.
Jim

Alistair Hosie
12-18-2010, 11:29 AM
That sounds like a good solution to your problem.I have a few sets of er collets and would advise er 32's for giving a wide selection of drills a good grip.Alistair

danlb
12-18-2010, 12:05 PM
You can see from the chart at http://www.workholding.com/Pg30_ERCollets.pdf that the ER20 collets will hold a shaft as big as 1/2 inch. The collet itself is only 1.22 inches long, but you are likely to find that you don't get a gripping surface inside the collet the whole length.

Dan

The

Arthur.Marks
12-18-2010, 12:12 PM
If you're only using for drills, ER-20 is a good size. They max at 1/2", as said, so you really should be able to hold all your drills unless you are doing some serious drilling. Anything larger than a 1/2" drill is a Silver & Demming in my shop. Usually an end mill drills a better larger hole on my diminutive machines! :)

BUT, if you want to ever hold an endmill, face mill, boring head (those need plenty of room) you'll probably want a larger series. Then you can handle the 5/8" or if you choose, 3/4" shanks which abound on such tooling. Just a thought.

Ken_Shea
12-18-2010, 12:15 PM
I like the collet solution, still if only a couple size drills are in use, the screw-machine-length drills are the shortest. The shorter length also makes them less susceptible to breakage.

firbikrhd1
12-18-2010, 12:39 PM
I'll reply with a question that may induce some further thought. What is the taper if your spindle? If it's Morse taper or B&S taper, perhaps you can use collets that fit the taper directly thus saving the space that the ER collet holder takes up. Some ER Collet holders are almost as long as drill chucks, I think. Perhaps someone here can enlighten us as to whether the collet systems I mentioned will hold drills as firmly as required for drill bits.

IdahoJim
12-18-2010, 12:51 PM
many thanks, guys. Since I'm trying to save space, and as noted, the max drill shank size I'd use is about 1/2", it looks like the Er-20, or maybe 25 would work. Do any of you know the length of these chucks, measured from the spindle face? I'd like to figure out how much Z headroom I'm saving over the Jacobs 14N chuck. That thing is 3 1/2" long! It may be, as Ken Shea mentioned, I'd be better off buying short drills.
Also as, firbikr mentioned, and it's what I do now when the size works, is just getting many R8 collets, but I'm not even sure if they are available in enough sizes to cover the range of drills I'd be using.
Jim

GadgetBuilder
12-18-2010, 02:56 PM
The nut on an ER-20 is about 3/4" long, which will give you an idea of scale. CTC has MT2 and MT3 chucks for ER-20 as well as various other shanks.
http://www.ctctools.biz/servlet/the-Tool-%26-Work-Holding-cln-ER-Collet-Chucks/searchpath/888/start/37/total/92/Categories

I just bought an ER-20 chuck and collets from them, they seem well made. Should have bought an MT2 chuck too, didn't think about using it in the lathe (I'm making a drill sharpener). Best to get everything in one buy, shipping is high if you need just one item.

John

TexasTurnado
12-18-2010, 02:58 PM
http://i288.photobucket.com/albums/ll168/TexasTurnado/PA200076.jpg

Granted, this is a 3/4 em, but then these are er40 collets. I snugged it up to what I thought was enough, but obviously wasn't. :) I immediately switched to a em holder with setscrews that fit into Weldon notches in the em - no more "suck" :D

Black_Moons
12-18-2010, 03:08 PM
TexasTurnado: Have you read the ER specs for torque?
http://www.techniksusa.com/metal/torque_chart.htm
They don't spec 'Snug' they spec 'Hit it with a hammer, then find a bigger hammer..'
59ft/lbs on ER20, 100ft/lbs on ER32! And they usally give you a wrench thats less then 12" long.

Oddly, Can't seem to find any hard specs on R8 torque.

IdahoJim
12-18-2010, 03:22 PM
I feel sort of stupid now. There are sets of R8 collets available that will do what I want at minimal cost. They have the plus of maximizing the space saving over the drill chuck, too. I should have done more research before posting my question. These are for drills only....I had a couple of bad experiences trying to hold endmills in R8 collets, and gave that up. I now use EM holders, and am happy with that decision. I'm not doing production work, so speed isn't an essential consideration for me.
I'd like to re-thank everyone for their input....I definitely learned some things from the responses.
Jim

GadgetBuilder
12-18-2010, 03:57 PM
ER collets need considerable torque else they may exhibit runout. The torque spec may be considerably lower for ER-20 collets where the inboard end is countersunk, see:
http://www.rego-fix.com/catalog/pdf/13-techinfo.pdf

I'm surprised that R8 collets are an economical choice for holding drills. I thought that R8 collets each have a small holding range so it would be expensive to cover all sizes to 1/2" compared to ER-20 where a set of 13 collets covers 0.020 to over 1/2".

John

IdahoJim
12-18-2010, 05:47 PM
I'm surprised that R8 collets are an economical choice for holding drills. I thought that R8 collets each have a small holding range so it would be expensive to cover all sizes to 1/2" compared to ER-20 where a set of 13 collets covers 0.020 to over 1/2".

John

Here's a fairly inexpensive set, John, on Ebay.
http://cgi.ebay.com/23-Pc-R8-Round-Collets-Set-1-16-3-4-1-32-Collet-/360327947252?pt=BI_Tool_Work_Holding&hash=item53e53823f4

TexasTurnado
12-18-2010, 06:13 PM
TexasTurnado: Have you read the ER specs for torque?
http://www.techniksusa.com/metal/torque_chart.htm
They don't spec 'Snug' they spec 'Hit it with a hammer, then find a bigger hammer..'
59ft/lbs on ER20, 100ft/lbs on ER32! And they usally give you a wrench thats less then 12" long.

Oddly, Can't seem to find any hard specs on R8 torque.

I used the er40 wrench that came with the set - this is not an off brand, BTW. I have a set from ETM (now Iscar), comprised of the holder, collets, and wrench. And yes, I probably did not torque it to spec, but I laid into it rather hard! In any event, I now do not feel comfortable that the em is not going to "drift" whenever doing a heavy cut, so I use em holders with a setscrew in a groove (if the groove is not there, I make one!) for positive retention and peace of mind. For light cuts, I still use collets, but I try to leave a little margin in case it does move, and finish with a very light cut on anything critical.....

GadgetBuilder
12-18-2010, 08:06 PM
Jim,

My understanding is that single angle collets like 3C, 5C, and R8 have a very small range, something like 15 thou per collet, so you need them by 1/64's to cover the range. While they may work over a larger range it is possible to "spring" a collet by using it on a smaller item than designed. But this may be all wrong since I don't have actual experience, just what I recall from other's comments.

Double angle collets collapse on both ends so they have a larger range per collet. ER collets in particular were designed to handle a large range, 1mm = 40 thou per collet. It is possible to "spring" the smaller ER-20 collets by over torquing, in particular the 1mm collet has a much lower torque spec than the larger ER-20's.

Perhaps we'll both learn more about collets if one of the more experienced machinists jumps in here.

John

Edit: I paid $63.26 for a set of 13 ER-20 collets and a chuck(delivered in USA) from CTC. Just got them last week so I haven't used them yet. Best I can tell they meet their runout spec but need to be tightened firmly to do so.

KEJR
12-18-2010, 08:31 PM
I don't think its worth using R8's. As mentioned you would need them in at least 1/64th sets. I'd go with an ER20 if it didn't stick out of the spindle too far. In theory with an R8 spindle you should be able to get the nut of the ER20 pretty close to the spindle so it shouldn't stick out much (The collet could be partially into the R8 taper inside the holder).

KEJR

Toolguy
12-18-2010, 08:52 PM
The 5C and R8 and any other collet that are split from one end only have a range of about + or - .002 max. Exactly on size is better. The ER collets have many slots coming in alternately from both ends, therefore they can collapse in a parallel manner instead of an angular manner like the others. ER20 would be an excellent choice for drills. ER collets can usually cover the entire range of sizes with one set.

lazlo
12-18-2010, 08:53 PM
John, how are you cutting that Z-tapered slot? :D


I used the er40 wrench that came with the set - this is not an off brand, BTW. I have a set from ETM (now Iscar), comprised of the holder, collets, and wrench. And yes, I probably did not torque it to spec, but I laid into it rather hard!

I have the same set (in fact, I think John prodded me to get it :) ), and the ETM wrench is a BFW. The ER-40 collet spec is 140 ft/lbs. I've never measured it with a torque wrench (I don't think I have one that goes that high!), but like John, I give it a grunt. With a wrench that size, I'd imagine it's pretty close.

I haven't had an ER slip on me (yet), but for >= 3/4" endmills I use an EM holder. R8 gets sketchy > 3/4" too...

IdahoJim
12-18-2010, 08:56 PM
Jim,

My understanding is that single angle collets like 3C, 5C, and R8 have a very small range, something like 15 thou per collet, so you need them by 1/64's to cover the range. While they may work over a larger range it is possible to "spring" a collet by using it on a smaller item than designed. But this may be all wrong since I don't have actual experience, just what I recall from other's comments.

Double angle collets collapse on both ends so they have a larger range per collet. ER collets in particular were designed to handle a large range, 1mm = 40 thou per collet. It is possible to "spring" the smaller ER-20 collets by over torquing, in particular the 1mm collet has a much lower torque spec than the larger ER-20's.

Perhaps we'll both learn more about collets if one of the more experienced machinists jumps in here.

John

Edit: I paid $63.26 for a set of 13 ER-20 collets and a chuck(delivered in USA) from CTC. Just got them last week so I haven't used them yet. Best I can tell they meet their runout spec but need to be tightened firmly to do so.

Yup...that's my understanding, too. But a set of R8's in 1/32 increments doesn't miss that .015" range by more than 1/2 a thou, and would probably work OK for drills. In emergencies I've sprung an R8 farther than that without ill effects, though I wouldn't want to do it as a regular practice. I just finished a piece yesterday where I put an 'I' drill in a 1/4" R8 collet. It ran true enough for what I was doing, and I had no other method to get that hole where i needed it. Frankly, in most cases I'd rather just use the drill chuck, but now and then.....LOL
That's a good price for the ER-20 set.:D
Edit: After further checking I see how the set of R8's in 32's misses the range, assuming they'll only tolerate .008+/-. It looks like the ER20, or 25 is probably the way to go.
Jim

Rich Carlstedt
12-18-2010, 09:05 PM
two comments.

First, It may be cheaper to just buy a set of "Screw Machine Drills"
They are about 1/3 the length of jobber drills .
I use them a lot, particularly in the larger sizes, and the are more rigid than jobber drills.

Second, when ever !!!!! putting an endmill in a collet on a critical job ( a "Z" axis dimension makes it critical ) you brush the base of the endmill after it is clamped, with red nail polish . catch both the collet and the cutter .

now, if it starts to pull, you will see a very clear line develop between the collet and the mill cutter. The nail polish is very hard and cracks when moved. you can actually see .003" or less

Rich
PS ,Buy the cheapest stuff you can find

lazlo
12-18-2010, 09:09 PM
Second, when ever !!!!! putting an endmill in a collet on a critical job ( a "Z" axis dimension makes it critical ) you brush the base of the endmill after it is clamped, with red nail polish . catch both the collet and the cutter .

now, if it starts to pull, you will see a very clear line develop between the collet and the mill cutter. The nail polish is very hard and cracks when moved. you can actually see .003" or less

That's a very cool tip Rich! That should go in the sticky :)

TexasTurnado
12-18-2010, 09:20 PM
John, how are you cutting that Z-tapered slot? :D


It took a lot of careful planning and an accurately calibrated torque wrench - not to mention carefully adjusting the feed rate.....:D