# First Major DRO Job



## Susquatch (Sep 15, 2022)

As many will know, I finally finished installing the last part of my DRO - the quill axis. It is set to work together with my knee axis for a combined Z + Quill Readout.

Ever since its completion, I've been futzing around making slow progress on a job that I saved specifically for the DRO. In fact, you could almost say the job was part of the reason I got the DRO in the first place.

A long time ago, I put together a triple front spider for concentricity work. The spider allows you to align a work object totally concentric to the axis of the spindle. But is a beast to use because it had to be held and aligned in a four jaw before a part could be installed and aligned in the spider. A few years after making the spider assembly, I bought a D1-5 back plate for it so it could be directly used without the 4 jaw. The problem was the screws that had to be installed in the hub recess of the backplate without affecting the spindle attachment. To be honest, I had very low confidence in my ability to layout a perfect 6 element bolt circle using the tools I had at the time.

On the other hand, it was a perfect job for the circular array (bolt circle) function of a DRO.

Only 4 of 6 screws installed so far. But good enough for a photo. Two more to go.






Very happy so far. Here is a shot of the DRO in action.






Some challenges were encountered.

The stem of my 1/4-28 taps measures 0.254 - too big to enter a 1/4" hole. But I needed a long screw hole to fit through the cast-iron backplate and have enough thread to maintain a good solid hold on the spider. I suppose with the DRO I could have machined the two parts separately, but again I had no confidence. In time I may charge ahead - but for now it's crawl before you walk before you run.

A bigger socket head cap screw would have been better but that might weaken the backplate casting too much. A 1/4 inch screw is actually plenty strong enough though, so a compromise was made.  I drilled out an extra 1/4 inch of depth to accomodate the tap shaft with a 17/64ths drill. This was plenty but the 17/64 drill bit just wouldn't fit a 1/4" ER32 collet. I had to use a 5/16 collet. That worked but it felt just awful tightening that collet that much. I'm going to see if I can find a 9/32 collet. 32nds ER32 collets are not common and are not listed but who knows - they may exist somewhere. I do enough 1/4" tapping that it's worth trying to find the collet. If not, I may grind a 1/4" Collet out a bit instead.

Most of the drilling and tapping required depth control. The 4th axis of the DRO came in really handy for that. The biggest problem was anticipated - calibrating the Z Axis zero. Basically, I touched off the face of the D1-5 spindle nose recess and set zero there for each increasingly larger tool used. I maintained a chart of depths for each phase - tap drill, screw shaft clearance, tap shaft clearance, and finally socket head countersink depth. All tapping was done manually.

When I'm all done, I'll clean and reinstall the cam-lock studs and try it out.

All-in-all, I'm very happy. So far - so good......    Nice DRO.


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## phaxtris (Sep 15, 2022)

oh i like your dro, does it change the number of holes and the angle of the holes, etc depending on what you enter ? like if you put in 4 hole pattern from 0-180 will the screen display 4 holes on an arc ?

i cant really picture what exactly your doing with the spider, but it sounds intricate, look forward to seeing a completed picture


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## Susquatch (Sep 15, 2022)

phaxtris said:


> oh i like your dro, does it change the number of holes and the angle of the holes, etc depending on what you enter ? like if you put in 4 hole pattern from 0-180 will the screen display 4 holes on an arc ?



Yes. You can create whatever array you want. It has four modes. Angle and diameter, diameter and number of holes, starting hole and angle increment, and..... I forget.... LOL! For this job, I used diameter and number of holes. 

It will also do square arrays, cones, and vectors. 




phaxtris said:


> i cant really picture what exactly your doing with the spider, but it sounds intricate, look forward to seeing a completed picture



I'll post a better picture when the job is done and it's mounted on my lathe.


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## phaxtris (Sep 15, 2022)

Susquatch said:


> Yes. You can create whatever array you want. It has four modes. Angle and diameter, diameter and number of holes, starting hole and angle increment, and..... I forget.... LOL! For this job, I used diameter and number of holes.
> 
> It will also do square arrays, cones, and vectors.
> 
> ...



thats awesome, my disco dro allows you to do that stuff, but you have no way of knowing if you put it all in correctly without actually running to each dimension on the table....i like yours way better, tradezies ? lol

look forward to a picture of this whole contraption your building mounted


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## Susquatch (Sep 15, 2022)

For those who noticed, I have deleted the duplicate thread.

Thank you.


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## RobinHood (Sep 15, 2022)

Nice work!

I would just get a 7mm ER32 collet. Very common. 17/64th —> ~ 6.75 mm; it will never fit a 1/4” collet as that would have to “stretch” - which ERs don’t. 

Just get a whole metric set and be done with it… (it’s so easy to spend someone else’s $$s, lol).


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## Susquatch (Sep 15, 2022)

RobinHood said:


> Nice work!
> 
> I would just get a 7mm ER32 collet. Very common. 17/64th —> ~ 6.75 mm; it will never fit a 1/4” collet as that would have to “stretch” - which ERs don’t.
> 
> Just get a whole metric set and be done with it… (it’s so easy to spend someone else’s $$s, lol).



I'm gunna gave to look at this a bit closer @RobinHood. I had thought of doing exactly that. But the charts I looked at list the same part numbers for both metric and Imperial - just different size overlaps. So something weird is going on there. Either that or I'm gunna have to stop shopping at the affordable places! LOL!


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## 140mower (Sep 15, 2022)

Susquatch said:


> For those who noticed, I have deleted the duplicate thread.
> 
> Thank you.


......damn, thought I'd started drinking again for a minute there....


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## Susquatch (Sep 15, 2022)

140mower said:


> ......damn, thought I'd started drinking again for a minute there....


It's somewhat interesting how that all happened. In fact, I'm not even sure how it happened.... 

I posted the original, then went off looking at other threads, then came back and noticed that the photos were links not pictures so I edited the post to delete the links and properly post the photos. Then replied to a few new comments. Then you and @YYCHM commented about the duplicated thread. 

When I read your notes, I didn't see the duplicate so I assumed that editing the photos caused a browser refresh problem on your end and replied to you both to that effect. 

After doing that, I reviewed the Latest Posts section and saw the duplicate threads! Then I had to figure out which one to delete!  

After that, I needed the drink you thought you had! 

I'm thinking that editing my original post like that without refreshing caused the system to make a second copy. Might never know. 

Anyway, it's fixed now.


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## 140mower (Sep 15, 2022)

Susquatch said:


> It's somewhat interesting how that all happened. In fact, I'm not even sure how it happened....
> 
> I posted the original, then went off looking at other threads, then came back and noticed that the photos were links not pictures so I edited the post to delete the links and properly post the photos. Then replied to a few new comments. Then you and @YYCHM commented about the duplicated thread.
> 
> ...


.....and my sobriety lives another day...


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## Susquatch (Sep 15, 2022)

140mower said:


> .....and my sobriety lives another day...



I like your sense of humour!


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## David_R8 (Sep 15, 2022)

Love that LCD display!


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## Susquatch (Sep 16, 2022)

David_R8 said:


> Love that LCD display!



The photo does not do it justice. It looks 10x better in real life. My camera does not pick up the contrast and does pick up some kind of raster that my eye cannot see. Raster may not be the right term but it's what comes to mind. I'll have to see if I can find a way to take a better photo.


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## Susquatch (Sep 16, 2022)

David_R8 said:


> Love that LCD display!



I fiddled with my phone camera settings and was able to take a better photo. Still not nearly as nice as what my eyes see, but better than other photos I have taken. 






And then I discovered this nice surprise..... Since the RPM doesn't work yet anyway, I turned it off. Guess what happened? The axis info got bigger to take up more of the screen!


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## Hacker (Sep 16, 2022)

I have the same DRO and I agree the screen is great. Also the modes of the hole pattern allows you options on how you come at a project.


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## Susquatch (Sep 16, 2022)

Here is another photo showing the bolt circle function in action. For this particular circular array method, you:

1. Find center (as you would in any other process requiring a center). Lots of ways to do this with a DRO.
2. Zero the DRO X & Y Axis
3. Go to circular array via the function set
4. Select the desired mode
5. Set diameter
6. Set number of holes
7. Press Start

The display will look like this:






Note that I've already moved the X axis half way there. As you crank, the red spot moves. In this screen, I just need to move the x over 0.6056 to the right and the Y back a tenth. (a tenth eh .... Ya right!) Funny as that may be, this thing will display hundredths!

8. Just crank the x & y till they both read zero
9. Do your machining Op.
10. Press right or left arrow
11. DRO will go to the next or the previous hole.
12. Repeat

The DRO will retain these settings so you can crank off to the side to change tools, and then return to the work in progress.


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## phaxtris (Sep 16, 2022)

Oh man I need an upgrade, does it plug into the regular glass scales with the old style serial plug (db9 or something, the one that use to be a mouse)


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## gerritv (Sep 16, 2022)

yes, I can't imagine going back to no DRO. No layout, no spot drilling, just drill or mill.


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## David_R8 (Sep 16, 2022)

The DRO on my mill is very similar and it's the bee's knees to be sure!


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## Susquatch (Sep 16, 2022)

phaxtris said:


> Oh man I need an upgrade, does it plug into the regular glass scales with the old style serial plug (db9 or something, the one that use to be a mouse)



I don't know. I have wondered the same thing. It would be nice to know how that might work.

This one is setup with 1 micron magnetic scales. I know for sure that you can select lower or higher resolutions. But I don't know if the magnetic/glass signals are compatible.  It would be good to know that detail. 

Yes, the connections are DB-9. Even the RPM is DB-9.



gerritv said:


> yes, I can't imagine going back to no DRO. No layout, no spot drilling, just drill or mill.



No spot drilling??? Don't you worry about tip wander?


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## gerritv (Sep 16, 2022)

Susquatch said:


> No spot drilling??? Don't you worry about tip wander?


stub drills, 135dg, most are split point. All adds up to little or no wander on a flat surface. I just lightly touch first to make a tiny spot, then go in.


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## jcdammeyer (Sep 16, 2022)

Mine does things like bolt circles but I have to pull out the manual each time to figure out how to use it.
Connects to the cheap (likely no longer available) Chinese scales.  Also works with a probe (and probe diameter) to find the center of a hole.



I downloaded that Android DRO app onto my Samsung Tablet.  Nice.  If one can find a used tablet for $50 or so then this might be an inexpensive way to go.








						DIY DRO Project
					

Blog dedicated to DIY digital readout TouchDRO and other hobby machining and engineering subjects.




					www.yuriystoys.com
				




For fun I've ordered a couple of these BlueTooth Modules.








						2.71C$ 8% OFF|New Version Hc-06 Hc 06 Rf Wireless Bluetooth Transceiver Slave Module Rs232 / Ttl To Uart Converter And Adapter - Integrated Circuits - AliExpress
					

Smarter Shopping, Better Living!  Aliexpress.com




					www.aliexpress.com


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## Susquatch (Sep 16, 2022)

phaxtris said:


> look forward to a picture of this whole contraption your building mounted



All done! 






I have another job on the lathe right now so mounting it will have to wait!


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## Susquatch (Sep 18, 2022)

RobinHood said:


> I would just get a 7mm ER32 collet. Very common. 17/64th —> ~ 6.75 mm; it will never fit a 1/4” collet as that would have to “stretch” - which ERs don’t.



Ive tried in vain to make sense of this @RobinHood .

I can find references to both metric and Imperial ER Collets, but when I dig into the details I either find that they are actually the same or I find nothing definitive.

Here is a sample chart from Little Machine Shop.






Here is a link if you want more detail.









						ER Collet Sizes
					

This page shows the size and clamping range of the various size ER collets that we carry.




					littlemachineshop.com
				




Notice that a 3/16 collet is also listed as a 4 to 5 mm collet. This is true through the full range.

Other web sites don't necessarily list them this way. Most list a set of separate metric collets or an imperial set. I cannot find such as set that provides actual dimensional information to prove that they are really either metric or imperial.

This leaves a rather difficult set of alternatives. Either both are actually the same just different labels, or they are physically different with different dimensions.

Rego (the inventor of RE Collets) sells both Metric and Imperial collets, but they don't have a 7mm.  Just 6 & 8.  They don't provide detailed dimensions. It would be interesting to check to see if a 1/4" drill or end mill will fit into their 6mm collet. That might tell us if the markings were truly metric or just a marketing plot to sell more collets.

I happen to have an imperial set. I don't really want to buy a metric set and then discover that they are really the same.

Do you (or anyone else) have a metric set that they can actually measure?

If not, I will try to buy *ONE* metric collet and see what happens.


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## gerritv (Sep 18, 2022)

I have several metric collets (5C, ER16, ER20) In ER16/ER20 I have a 'full' set of 1mm increments. I also have imperial sizes for shanks that I use often, specifically 1/8, 1/4 and 5/16.
A 1/4" bit will/should not fit in a 6mm collet. If you force it in, you ruin the collet, it is now sprung. 6mm is 0.236" Collets grip best at their nominal size. So while a 6-5mm collet can ostensibly be used at 5mm, it takes a lot of force to close, and the likelyhood of runout is higher.

My advice is to buy a set, and then for the other style (as in imperial or metric) buy nominal sizes for the shanks you use.

A pin of nominal size slides smoothly into a properly sized collet. So my 1/8" shop made engraving bits fit great in the 1/8 collet. It won't fit in a 3mm collet, but will in a 3-4 but lots of closing down, with runout as a result.
When it matters, as in I want minimal runout, I buy specific sizes, with no clamping range. An example (I haven't bought from them but is shows what is available) https://www.aliexpress.com/item/1005001516713169.html . And when I am flush with money, I go for the AA grade. The smaller the cutter, the more runout matters, es. with carbide. Since I am heading into the sub mm world over the next while I am starting to pay attention to these details  
Gerrit


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## gerritv (Sep 18, 2022)

For clarification, By full set I mean of course the sets marked with ranges such as 3-4mm.


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## PeterT (Sep 18, 2022)

IMP & MET collets are not the same. I think this is a case where LMS is trying to be helpful by converting, unfortunately is causing potential confusion as it pertains to physical sizing. They do that elsewhere on the site, maybe its hole/thread sizing I cant recall. Anyways you don't want to stretch collets above nominal even if it appears dimensionally close. And collets do have a recommended squeeze range (diameter reduction) but that varies by collet type. The ramifications are worth considering. Distorting (ruining) a collet is one thing. Having it come lose when you thought it was tight can pooch up some milling work you may have invested time & cost.


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## DPittman (Sep 18, 2022)

PeterT said:


> And collets do have a recommended squeeze range (diameter reduction) but that varies by collet type.


I agree and it makes sense that a collet should not be stretched at all.  I have OZ25 collets and I have never been able to find the recommended squeeze range for them but I use 1/64" as that is what I saw for other er collets I believe.


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## Susquatch (Sep 18, 2022)

@gerritv @PeterT - I am aware that the collets can't be expanded - only tightened, and that they can accomodate a range. But I appreciate your input anyway. You don't know what I know or what I don't know - so better safe than sorry.

I want to believe that you are right that metric collets really are metric, and that Imperial Collets really are Imperial. But the more I look the more I find evidence to the contrary. It makes me nervous.

For example, I looked a little closer at the little machine shop collets. Contrary to my first assumption, it turns out that they are actually metric with Imperial markings. Not imperial with metric. Go figure!

Believe it or not, I actually think getting a true metric collet is more likely on Ali just because they are much more likely to make the mistake (if it is a mistake. Wierd trying to think like them. LOL)

My take away from this little exercise is:  If you are buying ER Collets, make sure you are really getting what you think you are getting, or at least make sure that you will be happy either way - which is of course entirely possible.

I'm actually finished the job that I needed a metric 7mm collet for. Since it was in range and since it just felt bad but was really ok, I just ignored my concerns and cranked the collet down. So there is no rush anymore at all.

Right now, my plan is to buy a few selected metric collets (only as required) from someplace like Amazon or my local jobber so they can be returned if they are not really the true metric ones I want.


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## DPittman (Sep 18, 2022)

Susquatch said:


> @gerritv @PeterT - I am aware that the collets can't be expanded - only tightened, and that they can accomodate a range. But I appreciate your input anyway. You don't know what I know or what I don't know - so better safe than sorry.
> 
> I want to believe that you are right that metric collets really are metric, and that Imperial Collets really are Imperial. But the more I look the more I find evidence to the contrary. It makes me nervous.
> 
> ...


My OZ25 collets are easy and cheap to find in metric, not so much in imperial but I do have a set of 10 ranging from  1/8" to 1"


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## gerritv (Sep 18, 2022)

@Susquatch you are over thinking this. 
A more reputable source of info, Haimer. They list metric and imperial collets. If you do the conversion, a 2-3mm collet has a max opening of 3mm or 0.118" , a 1/8" collet has a max opening of .125". A 3-4mm collet would have a max opening of .157" so a 3mm shank would fit but again, not optimal. Within the ranges as presented on LMS their reco works, but not best practice for holding power. Advice found elsewhere "Choosing a collet that exactly matches the cutting tool diameter improves grip force, accuracy, and rigidity, resulting in extended tool life and better surface finishes."
If/when you buy the LMS ones, you will be buying from Asia so personally I just go there in the first place and save my $. I have had 0, nada issues with quality of er11/16/20/32 collets. When I order an AA precision one, that is what I get. (and yes, I can measure to 5 microns) My first ER11 set was very inexpensive, and it still has acceptable runout. Proper tightening helps with that as well.

gerrit


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## PeterT (Sep 18, 2022)

_I looked a little closer at the little machine shop collets. Contrary to my first assumption, it turns out that they are actually metric with Imperial markings. Not imperial with metric. Go figure!_

Hmmm... that sounds a bit cheesy IMO. Every tooling catalog I've ever seen makes a clear distinction between Imperial & Metric. Again, not sure if LMS is trying to be helpful, but I think it adds to confusion. I mean lets go all in & call a metric drill set 'fractional', a 3mm is actually 7.56/64"!


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## gerritv (Sep 18, 2022)

Its worse in the catalog photos, the markings are imperial. And then in the text they claim equivalent metric sizes. Which is not possible at nominal. The AliExpress store(s) I bought/buy mine from do not make that mistake. If I order imperial 1/8" that is what I get, and marked as such.

Gerrit


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## PeterT (Sep 18, 2022)

_I actually think getting a true metric collet is more likely on Ali just because they are much more likely to make the mistake (if it is a mistake. Wierd trying to think like them_

I think the likelihood of  metric is more likely because Ali (and large part of manufacturing world) is predominantly metric when it comes to tooling at least, unless they think there is a market for imperial. They do the same thing btw, list things as IMP. I assume to be helpful. But for every Imperial tap or end mill on Ali, you'll see 1000 metric


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## gerritv (Sep 18, 2022)

@PeterT As my just prior post says, I order imp, I get imp from AliExpress and similarly with metric. They actually know the difference. I have bought both so have experience with it..


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## DPittman (Sep 18, 2022)

I have bought the majority of my metric collets from Aliexpress and only the odd imperial one as they're hard to find in my style.  There has been a difference in quality of the collets however, some were just not as nicely finished of (burrs on inside slits mainly) but I did have one metric one that was such a hard and poor fit into the chuck nut I threw the dang thing away. Unfortunately I have no idea which supplier was the bad one as I ordered here and there, waited for months for them to arrive and then by the time I went to use it, I had no recollection of whom I purchased it from.


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## jcdammeyer (Sep 18, 2022)

I bought a set of ER32 Metric AA collets from China.  Wasn't cheap but they appear to be good quality.  As a test just now I took a 1/4" drill bit (6.35mm) and mounted the 7-6 collet into the square collet block.  The numbering seems consistent in that the largest opening is 7mm and it can compress down to 6mm.  In this case it went down to 6.35 smoothly.  The next smaller collet is 6-5 so it push came to shove and I had an exact 6mm diameter shaft I'd use the 6-5.  The 6.35 drill bit does not fit in the 6-5.  (I suppose it could be forced but why?)

Then after I tightened it I used some narrow feeler gauges to see if the collet slots were angled at all.  In the area below the drill bit the gap in each of the slots was about 0.001" to 0.002" smaller.  However from the top for the length of the drill bit shank the spacing was consistent all the way around.  It didn't get any smaller so the compression appeared to be fairly even.

As best as I could measure.


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## Susquatch (Sep 19, 2022)

PeterT said:


> _I actually think getting a true metric collet is more likely on Ali just because they are much more likely to make the mistake (if it is a mistake. Wierd trying to think like them_
> 
> I think the likelihood of  metric is more likely because Ali (and large part of manufacturing world) is predominantly metric when it comes to tooling at least, unless they think there is a market for imperial. They do the same thing btw, list things as IMP. I assume to be helpful. But for every Imperial tap or end mill on Ali, you'll see 1000 metric



Yes, that was my point. Being in China, metric is the goto standard. Hence stuff like M1/4  LOL!

But I started this part of the thread back when I first encountered the confusion on the Rego website. Since Rego is the inventor of the ER Collet, I gave their information the highest credibility.  I see now that this was a mistake. Their marketing guys must have been hard at work making a mess of things.




gerritv said:


> @Susquatch you are over thinking this.
> A more reputable source of info, Haimer. They list metric and imperial collets. If you do the conversion, a 2-3mm collet has a max opening of 3mm or 0.118" , a 1/8" collet has a max opening of .125". A 3-4mm collet would have a max opening of .157" so a 3mm shank would fit but again, not optimal. Within the ranges as presented on LMS their reco works, but not best practice for holding power.



I freely confess that I usually overthink things. That is just how I am wired. Whenever I encounter things that don't make sense, I usually assume somebody made an honest mistake. But I also consider the possibility that I might not know something. So, I dig a bit deeper. (overthink) I usually start that process by getting more info from the most credible source of info I can find - in this case Rego.

Now that the dust has settled, I know that there really are both true metric and true imperial ER Collets. Frankly, other than for improved nominal fit, I don't really see the point of this. Since collets are designed to fit a range of sizes anyway, metric only would have been just fine - especially since 1mm (0.0394) is a finer increment than 1/16 (0.0625)

I also dove a bit deeper into the LMS chart and I believe you are correct. They are just trying to be helpful. Basically, they are saying that you can use a 6-7mm collet to hold a nominal 1/4" shaft. If they had put metric first in their chart and then titled the imperial column as "Also fits Imperial" and moved that column further right without the bolding, it would have been ok. Especially since that is almost exactly what I was trying to accomplish in the first place! I was trying to find a better fitting collet for a 17/64 drill. As you all know, collets don't expand. So a 17/64 drill requires a 5/16 collet and won't fit a 1/4" collet. But, tightening a 5/16 collet down to 17/64 hurt my sensibilities - WAY TOO MUCH tightening. A 7mm collet would have been better. Hence my over thought journey.

Anyway, my previous closing advice still stands. When shopping for ER collets, be careful. There is some misleading info out there and it would be disappointing to get the wrong collet.


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## gerritv (Sep 19, 2022)

The Rego info is quite clear to me  Is it becasue I am born in EU? Not sure. 
This screen shot shows the entry for an 8.5mm ER16 collet. Normal size is 8.5mm/0.33" and it has a range, metric and imp. But the nominal size is 8.5mm regarldess of what else you can fit in it. The best grip will be on that nominal size, anything else will be less. That is the whole point of using nominal sizes, just like with 5C collets (which have almost no gripping range outside the nominal). The same info for a 7/32" collet shows it is nominal 7/32, with a metric equivalent shown.


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## Susquatch (Sep 19, 2022)

DPittman said:


> There has been a difference in quality of the collets however, some were just not as nicely finished of (burrs on inside slits mainly)



I've had a few like this too. I bought a very cheap ER11 set for my Spindle Motor Based Tool Post Grinder. They work well enough for that but they were crammed with burrs.


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## Susquatch (Sep 19, 2022)

gerritv said:


> The Rego info is quite clear to me  Is it becasue I am born in EU? Not sure.



I didn't land on an individual product page. I landed on a generic info page for the entire collet set in a chart that was sort of like the LMS info. I can't seem to find it now.


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## Susquatch (Sep 19, 2022)

jcdammeyer said:


> The 6.35 drill bit does not fit in the 6-5. (I suppose it could be forced but why?)



I believe doing so will damage the collet. 

But I confess to trying to make a 17/64 drill fit in a 1/4 collet. It's sooooo close! However, I couldn't get it to go in with reasonable effort and I didn't try to force it, so it didn't happen!


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## Susquatch (Sep 19, 2022)

I should have added that the 5/16 collet did hold the 17/64 drill just fine. It was within the specified range that the collet was designed for. It didn't slip and it did the job. It was just painful and felt wrong to have to crank on the nut that much.


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## Susquatch (Oct 8, 2022)

phaxtris said:


> look forward to a picture of this whole contraption your building mounted



As promised, I finished the job I had on my lathe and so I mounted my triple spider and took a photo.

The purpose of the spider is to be able to align a part axially in perfect alignment with the axis of the spindle. Not just centered, but centered in two locations so that the entire part is axially aligned.

Two sets of jack screws are used to dial in the part.

My spider has three sets of jack screws so that it can be used with short or long parts. You just choose which two of the three sets to use and back off on the third set.

The part mounted in the spider in the photo just happens to be the dumbbell I used to test my Spindle alignment. I am using the front two sets of Jack's screws here.


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## jcdammeyer (Oct 8, 2022)

Susquatch said:


> As promised, I finished the job I had on my lathe and so I mounted my triple spider and took a photo.
> 
> The purpose of the spider is to be able to align a part axially in perfect alignment with the axis of the spindle. Not just centered, but centered in two locations so that the entire part is axially aligned.
> 
> ...


I'm still puzzled as to why this is any better than a 4 jaw chuck?


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## Susquatch (Oct 8, 2022)

jcdammeyer said:


> I'm still puzzled as to why this is any better than a 4 jaw chuck?


A four Jaw can only align the part at one place along its length. It cannot align the entire axis.

Yes, it can do it for a part that has the outside diameter concentric with the ID, but only if the outside is already concentric and only if the OD is parallel and only if the jaws are also parallel.

The spider allows you to "perfectly" align the part regardless of its outside OD concentricity, and regardless of how parallel the Jaws and OD of the part are.


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## Susquatch (Oct 8, 2022)

jcdammeyer said:


> I'm still puzzled as to why this is any better than a 4 jaw chuck?



It might help to understand if you consider mounting a bar in the 4jaw. Usually, the bar can be centered, but the far end will wobble. The spider allows you to eliminate the wobble. 

Alternatively, you could machine the bar to be concentric as this is the intrinsic purpose of a lathe. 

But, if you don't want to turn the part and just want it dialed in as is, you need a double spider.


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## jcdammeyer (Oct 8, 2022)

Susquatch said:


> It might help to understand if you consider mounting a bar in the 4jaw. Usually, the bar can be centered, but the far end will wobble. The spider allows you to eliminate the wobble.
> 
> Alternatively, you could machine the bar to be concentric as this is the intrinsic purpose of a lathe.
> 
> But, if you don't want to turn the part and just want it dialed in as is, you need a double spider.


So I did follow that idea but implementation has me puzzled.
1. You grab a piece of CRS say 3/8" diameter and put it into the 4 jaw with 4" extended.
2. Dial indicator on the part right by the jaws, 0.2" from the jaws, allows you to adjust until the dial indicator reads true.
3. Dial indicator on the end at the 3.9" point shows 0.025" wobble.

OK.  The traditional way of course is to first drill a center hole with the part protruding 0.25" and the dial indicator at the 0.2" spot.  Turned true and then center drilled.
Now extend out and again true at the 0.2" from the jaws and then set the center into the end which keeps the 4" end from wobbling.  But clearly it would be stressed then since the opposite end sticking out the back end of the spindle might not be centered. Right?

So we start again with step 1 but into the spider.  
Which screws do you adjust first?  Inner or outer?  And where is the dial indicator put first?  The outer end?


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## Susquatch (Oct 8, 2022)

jcdammeyer said:


> Turned true and then center drilled.





jcdammeyer said:


> Now extend out and again true at the 0.2" from the jaws and then set the center into the end which keeps the 4" end from wobbling. But clearly it would be stressed then since the opposite end sticking out the back end of the spindle might not be centered. Right?



All that assumes you can machine the outside to true the part.

In this case, that isn't allowed. For argument sake, just assume it's a polished part that is already at final diameter. That may or may not be the case but it suffices to explain the process. 

Although it isn't strictly required, I always start at the end nearest the chuck. I adjust the closest set of jack screws until the indicator reads zero runout. Then I move the indicator to the far end and adjust the far left jack screws until the indicator reads zero runout. Then I repeat the process again nearest the fixture, then furthest, then nearest...... Until both locations read zero runout. Now I know the part is running concentric to the lathe axis and I can proceed to do whatever work was required. 

If the part is long enough, the triple spider is not required. You can use a four jaw with gimbals and a rear spider at the other end of the spindle to do the same thing.


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