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R8 collets

Eric,
There are lots of mini-mill model ‘numbers’ available that capable of precise machining with the proper cutter tooling. The R8 spindle is fairly common for a range of cutters.

Commercial T&D shops have ‘full size’ knee mills (5hp, 9 x 40” tables, etc).
Unfortunately, these ‘full size’ mills are way to heavy for the typical home shop.

How is the supplier network for precious metals these days ?
 
LenVW said:
Eric,
There are lots of mini-mill model ‘numbers’ available that capable of precise machining with the proper cutter tooling. The R8 spindle is fairly common for a range of cutters.

Commercial T&D shops have ‘full size’ knee mills (5hp, 9 x 40” tables, etc).
Unfortunately, these ‘full size’ mills are way to heavy for the typical home shop.

How is the supplier network for precious metals these days ?
Click to expand...
I have another approach to gaining height on the mill but am waiting for stock to come in at LMS.
I only buy white metals form a bullion dealer and with 24K and alloys make my own yellow karat metals.
 
I'm still thinking about pulling the trigger to buy my first mill (likely soon) - so I'm learning about tooling. I realize that starting off with the right collets (for your intended purpose) is quite important. I recently watched what Joe Pieczynski had to say about collets (Joe puts out a lot of good videos). The last 5 minutes of the video give a great visual explanation of the difference between R8 and R8-ER collets -- have a look @eric_brackenbury:

joe pieczynski collets youtube - Search Videos

www.bing.com www.bing.com
"Joe Pieczynski: Collets- Types, Pros, Cons, and general info"

I have a couple of collet questions & would appreciate feedback (I think this is a good place to ask rather than starting a new thread):
- Which grips better - an R8 collet that is properly sized or an R8-ER collet? (I understand that the size range of an R8 is much less than the ER but if sized correctly - which is better?)
- If using a carbide end mill - what is the best collet? or is a different holder needed? (when being used on a benchtop with a max power of 2 Hp)
- Is collet accuracy that important for a hobby guy not intending to make precision parts? (0.0002 vs 0.0006). I've seen accuracy shown as 0.0006 TIR - what is TIR?
- Amazon has a BETOOLL 13 psc R8 set, 1/8 to 7/8 at $128.38 - is this a good deal

13pcs Precision R8 Collets Set 1/8 - 7/8" Mill Chuck Holder for Bridgeport .0006 : Amazon.ca: Industrial & Scientific

13pcs Precision R8 Collets Set 1/8 - 7/8" Mill Chuck Holder for Bridgeport .0006 : Amazon.ca: Industrial & Scientific
www.amazon.ca
the above shows material as 65Mn - what's that?

Thanks
Craig
 
CWret said:
I'm still thinking about pulling the trigger to buy my first mill (likely soon) - so I'm learning about tooling. I realize that starting off with the right collets (for your intended purpose) is quite important. I recently watched what Joe Pieczynski had to say about collets (Joe puts out a lot of good videos). The last 5 minutes of the video give a great visual explanation of the difference between R8 and R8-ER collets -- have a look @eric_brackenbury:

joe pieczynski collets youtube - Search Videos

www.bing.com www.bing.com
"Joe Pieczynski: Collets- Types, Pros, Cons, and general info"

I have a couple of collet questions & would appreciate feedback (I think this is a good place to ask rather than starting a new thread):
- Which grips better - an R8 collet that is properly sized or an R8-ER collet? (I understand that the size range of an R8 is much less than the ER but if sized correctly - which is better?)
- If using a carbide end mill - what is the best collet? or is a different holder needed? (when being used on a benchtop with a max power of 2 Hp)
- Is collet accuracy that important for a hobby guy not intending to make precision parts? (0.0002 vs 0.0006). I've seen accuracy shown as 0.0006 TIR - what is TIR?
- Amazon has a BETOOLL 13 psc R8 set, 1/8 to 7/8 at $128.38 - is this a good deal

13pcs Precision R8 Collets Set 1/8 - 7/8" Mill Chuck Holder for Bridgeport .0006 : Amazon.ca: Industrial & Scientific

13pcs Precision R8 Collets Set 1/8 - 7/8" Mill Chuck Holder for Bridgeport .0006 : Amazon.ca: Industrial & Scientific
www.amazon.ca
the above shows material as 65Mn - what's that?

Thanks
Craig
Click to expand...
I have the ER32 collet in my Mill and it slightly reduces the available height but I have been given a way to mod the mill to regain that height. I am all about being as accurate as possible from the get go, remember if you start with an inacurate cut then proceed with another process in what you are making that inaccuracy will become worse the more you do. The cost of the ER32 chucks and holder is totaly worth it in the long run in my opinion. Thanks for the link to the video, it explaines it all very in the different chucking tools and I think confirms exactly how I see it :)
 
I’ll answer some of the questions…

TIR—> Total Indicator Reading; it means the total amount the needle of an indicator testing the bore of the collet moves during one rotation. In your case 6 tenths.

65Mn —-> is the steel designation; it is approximately equivalent to SAE 5160. Here is a little write-up on a knife maker website.
knifeuser.com

What is 65Mn Steel? - Carbon Steel Review - Knife User

This complete guide covers all the important aspects of 65Mn steel. Find out if it is good steel for your knife!
knifeuser.com knifeuser.com

Yes, use the best accuracy tooling you can afford. You can’t go wrong.

The clamping range of an ER collet is much wider as compared to a R8 one. They are great for holding drill bits; yes, it takes longer to change out tooling compared to using a keyless chuck, but the drill is held much more securely.
 
CWret said:
Which grips better - an R8 collet that is properly sized or an R8-ER collet? (I understand that the size range of an R8 is much less than the ER but if sized correctly - which is better?)
- If using a carbide end mill - what is the best collet? or is a different holder needed? (when being used on a benchtop with a max power of 2 Hp)
- Is collet accuracy that important for a hobby guy not intending to make precision parts? (0.0002 vs 0.0006).
Click to expand...

You have good answers from others above.

But perhaps I can fill in a few gaps with what I have come to know about your questions. Keep in mind that I've had a lathe for 30 years, but only recently got a mill that was worthy of this discussion. In other words, I'm still on the steep side of the learning curve for milling myself. But we all always learn more about everything as time passes.

Also, your questions are useful to other readers as well, so I am gunna say a whole bunch of things here that you already know. Please forgive me for that. I did try to answer the questions you asked but it might be buried a bit..... ;) I bolded them if you just want to get to the bottom line

As you know, collets can hold two primary types of things - tools and parts. Tools come in standard diameters so collets and holders don't need to be as flexible to hold them. Any 3/8 collet will hold a 3/8 tool perfectly because the entire inside surface of the collet fits the entire outside surface of the tool.

As you already know most bigger ER style collets have 8 slits running front to back and another 8 back to front, (16 in total and smaller ones have a few less) so ER collets do a better job of holding a wider range of sizes than say an R8 Tool Holder which only has 3 slots running only front to back. More slits mean more surfaces to conform better to a non- standard size of cylindrical shaft.

Your addition of a 2HP requirement adds a complexity that is difficult to deal with. HP is a rate of doing work. It isn't a work holding factor in and of itself. Torque is a much more meaningful parameter. Therefore I can only assume that you mean that your mill has a 2HP motor on it and that implies a range of torques that are probably encountered given your gearing and cutting speeds. My own mill has a 2HP motor on it so I can relate that to my own tool holding experiences.

To address your specific question about which is better for the optimum situation, I will have to speculate. I have not seen any testing or even any manufacturers claims. But it seems to me that there are two factors that define better. One is the gripped area which is a function of the diameter, the length, minus the number and width of any slots (slots can't hold anything). And the other is the clamping force imposed by the drawbar or collet nut against a taper. I would think that the R8 collet itself is the strongest but only for the situation where the diameter of the piece is the same as the diameter of the collet. I chose this for three reasons. 1. It's hard to use a collet wrench to get the collet tighter than a drawbar could. 2. Because two layers of holders (an ER held in an R8) adds additional complexity. 3. Because R8s have fewer slots and therefore more surface area. But that's just my guess..... I would also say that there will always be exceptions. To answer your question directly, I have a full set of ER32 collets and an ER32 - R8 holder, but I always reach for the right plain R8 holder to hold a carbide or HSS end mill. I could easily be convinced otherwise with input based on other factors I didn't think of. But that's my opinion for now. I'm also jealous of those guys with big 40 taper machines. But then again not so jealous at the cash register!

The material of the tool, either carbide, HSS, or otherwise has no bearing on that choice.

Generally speaking, lathes spin parts and mills spin tools. Therefore collets used on a lathe are usually used to hold parts, and collets used on the spindle of a mill is usually used to hold tools. Of course, innovative machinists know no boundaries and are often found doing things different to the norm like spinning tools in a lathe and parts in a mill.

The C5 collet is widely used to hold parts in a lathe chuck and in rotary holders on the table of a mill.

R8 collets do not consume any vertical height on a mill and are widely used to hold tools (end mills, fly cutters, etc.). As above, since these tools are almost always standard diameters, you don't need a huge array of R8 Collets. I have only 1/16, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 6mm, 12mm. I'll probably add more only as the need arises.

ER Collets can hold tools or parts. Individual collets also hold a wider range of diameters better than say an R8 or a C5.

C5 and ER collets do not require a drawbar themselves. Thus means that they can used with longer parts that extend through them. However, ER collets are often held in another holder that does require a drawbar which in turn limits the length of the stock that can be used.

Precision parts means different things to different machinists.
Machining parameters are usually described as a target dimension and a tolerance. For example 1.2500 inches +/- 0.0005. In other words the goal is to make a part with a diameter between 1.2495 and 1.2505. Sometimes the plus tolerance is different than the minus tolerance. But again, precision is a relative term. Even 1 whole thou is difficult to achieve in many operations. It often depends on the material, the tools, and machine. But the biggest variable is the machinist and their skill set.

For 90 percent of what most of us do, we just make parts that work. Precision is a word we use to describe setting the bar up a few notches. That might mean +/- 0.001 to some or 0.0005 to others or even less on occasion.

I think it's also important to remember that temperature and other external factors become more and more important as the precision requirement increases.

And last but not least, how good is your measuring equipment and how well calibrated is it. What you think is 5 tenths, might well be 15 tenths or more just because of measurement errors or a hot part.

Now to answer your specific question about collet runout and making non-precision parts. Again, I will offer an opinion. Better is better - period. But not necessarily for the reasons we might think. I believe that a slight collet runout won't affect the result in the part at all unless the cutting width is based on the diameter of the cutter. Collet runout only increases the cutting path by the runout. A slow feed will ensure that the part is cut smoothly. Most parts require several passes and a wider cut than the tool width. And for that matter, precision slots are seldom cut in one pass anyway. So a little run out is not really a big deal. You just compensate as you work.

Where the run out matters is usually vibration on the cutting surface caused by only one or two flutes doing most of the work. This can cause things like wavy looking surfaces. A little faster or slower feed for a given rpm will often correct this.

Does it really matter? My advice is to buy what you can afford. I don't think a little runout on a collet will give you any real heartburn. You can always sell a beginner set or even give them away if and when you actually need something better. On the other hand, if you can afford it, get good ones now - it's hard to imagine regretting that decision.

Sorry for the extensive response. It was mostly meant to help others looking for answers because your questions are actually quite common but few others with those questions have your broader understanding. Hopefully I answered your questions along the way.
 
Collet run-out (or more precisely, the lack of it) becomes more of a factor the smaller the cutter you intend to use. A 6 tenths TIR may be fine for a 3/8 or 1/4” end mill; but not so much for a 1/16” (or smaller) one. Generally, the smaller the cutter, the tighter the run-out tolerance needs to be.
 
RobinHood said:
Collet run-out (or more precisely, the lack of it) becomes more of a factor the smaller the cutter you intend to use. A 6 tenths TIR may be fine for a 3/8 or 1/4” end mill; but not so much for a 1/16” (or smaller) one. Generally, the smaller the cutter, the tighter the run-out tolerance needs to be.
Click to expand...

Good catch @RobinHood .

I'd only add that I would not let this push me into a very expensive collet set. I'd only buy one or two better small dimension collets if and when I hit the need for them. That's way less expensive than buying a whole set of really good ones.

Also keep in mind that the advertised TIR is usually worst case. Most of the collets in the set will probably be much better than that. With some luck, that will be the small ones - unless you you have Murphy genetics.
 
I'm still looking for a good resource that shows some empirical clamping pressures of R8's. If anyone has stumbled on some useful info, please forward a link.
What I mean is this. R8-style are slit from the bottom only, cantilevered tangs if you will. The tangs can only bend inward as they are drawn up into the tapered seat. So if the collet bore is very close in size to the shank, there should be lets call it acceptable clamping area to a shank once torqued. But if the shank is undersize to the collet bore, say to the limit of 1/32" incremental set, I cant see any other outcome other than the collet pinches near nose area but less (or no?) contact deeper into the collet. Which cannot be great for holding bigger EM's or higher loads. I know lots of people who swear by R8 collets for end milling, but when I look at EM holders with a low tolerance bore & a big bejesus set screw to key the EM flat, it makes me wonder.

ER-style are slit from both ends so as they are collapsed, they reduce radially inward, which is what you want. I use an ER collet style for milling, moreso to span wider diameter variation & including metric/imperial. Its small so I never tax it, but its worked well so far.
 
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Wow guys - that is some really great info. As a recent member to this forum (actually the only forum I’ve joined) I continue to be impressed with the quality of conversations and willingness of members to help each other.
I’ve been outside all day in this heat. Just came in to get ready to go to a street party. I only had time to quickly skip through your comments. I’ll have to digest this info and comment back tomorrow.

Thanks again
Craig
 
PeterT said:
I'm still looking for a good resource that shows some empirical clamping pressures of R8's. If anyone has stumbled on some useful info, please forward a link.
What I mean is this. R8-style are slit from the bottom only, cantilevered tangs if you will. The tangs can only bend inward as they are drawn up into the tapered seat. So if the collet bore is very close in size to the shank, there should be lets call it acceptable clamping area to a shank once torqued. But if the shank is undersize to the collet bore, say to the limit of 1/32" incremental set, I cant see any other outcome other than the collet pinches near nose area but less (or no?) contact deeper into the collet. Which cannot be great for holding bigger EM's or higher loads. I know lots of people who swear by R8 collets for end milling, but when I look at EM holders with a low tolerance bore & a big bejesus set screw to key the EM flat, it makes me wonder.

ER-style are slit from both ends so as they are collapsed, they reduce radially inward, which is what you want. I use an ER collet style for milling, moreso to span wider diameter variation & including metric/imperial. Its small so I never tax it, but its worked well so far.
Click to expand...

I pondered this identical question back when I got my mill/drill about 10 years ago.

I don't have any empirical data. However, I can add a few observations.

My collets all have an internal shoulder back about 40% of the way to the end of the slits. As a result, the collet only holds the end mill with 60% of its length.

20220807_165842.jpg


20220807_165900.jpg


The 60% mostly coincides (overlaps) with the R8 taper of the spindle itself. As a result, I believe I can say with confidence that any pinching starts at the rear of the end mill and progresses forward as the taper is tightened. The taper in the spindle is a fixed shape that cannot deform significantly because it has no slits. So in fact, your concern is mooted by the function and action of the R8 taper at the end of the collet.

Lastly, I don't think I know of anyone who would advocate using an r8 collet to hold anything but an endmill with a standard OD shaft. (1/16, 1/8, 1/4, 5/16, 3/8, 1/2, 5/8, 3/4, 6mm & 12mm etc. They can be used with standard size drill bits too. Basically, the R8 collet should only be used with tools that have the same diameter as the rating for the R8 collet.

They should not really be used with non-standard drill bits (eg 15/32 in a 1/2" collet) - although I confess that I have done that a time or two. It's certainly not ideal.

If you follow these guidelines, there won't be any cantilevering like you describe.

I previously forgot to mention R8 end mill holders. These are R8 holders that have no slits at all. The hole is dimensioned to fit the intended end mill size perfectly and then clamped in place with a grub screw on a flat on the end mill - see photo above.

In summary, I have never had a problem with an R8 collet spinning on an end mill when they are properly matched.

However, I do have one 1/2 R8 Collet that has been spun and badly damaged by its previous owner. I would guess it was not properly tightened or a slightly smaller endmill was used than it was designed for.

Edit - added photos.

Edit 2 - Peter - most of the comments above are aimed at other readers. I know you know most of this already. But I didn't want to leave open comments with no substantiation for other readers.
 
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