Center drills

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Yeah! Even when they already have broken packages on the shelf.
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    Hmm ... not from Microsoft I hope? :-)

    [ ... ]

    [ ... ]

    And with the head moved up and down?

    :-)
    Pretty close. What happens to the runout when you shift from light to tight tightening of the chuck?
BTW    Drill shanks are soft, and the chuck's jaws can bite into them     so they won't slip. End mill shanks are hardened and ground     smooth so they work well in collets or end mill holders, and are     *not* best used in a drill chuck. (The same applies to the     center drills, FWIW.)
    The soft shanks on drill bits also means that it is possible for the shank to bend, so the tip will describe a circle even if the chuck is prefect.
    And -- you are unlikely to find a long drill bit which has a shank long enough to allow runout measurements. (Aircraft drills are the exception -- but they may be too long for your machine.)

    O.K. So R8 is not in the game. It is possible that the arbor (MT-3 to whatever Jacobs taper the chuck uses) is bent -- but less likely with that 0.0005" TIR. This then suggests that the jaws in the chuck either have burrs in them, or there is wear in the body of the chuck. Different brands of chucks have different quality levels. The Albrecht keyless chucks are very accurate and can handle a long service before they start showing problems. (But they are larger, so they leave less space between the spindle and the table, so check for that too.)
    What happens if you use collets for the center drill and the plain drills? (Assuming that the plain drill is of a size which matches a collet which you have.)

    They are hardened and ground -- but fairly short usually. The best thing is drill blanks, which are hardened and ground to precise diameters -- but much longer. (And quite expensive, which is why I don't have an index full of the standard sizes. :-) But that length makes it easier to check for the drill chuck holding the drill at an angle, thus causing the circle. Measure runout just below the chuck, and close to the end (but before the diameter starts to fall).
    [ ... ]

    Aha! This is what I was answering somewhere above. You are unlikely to find a drill whose smooth shank is long enough. Usually the extra length is in the flutes.
    [ ... ]

    So -- use magnification -- and a small LED flashlight for illumination.

    And if the axis of the chuck is not parallel to that of the spindle, you will still have the point wandering in a circle. One of the reasons for the sliding offset is so you can push it while spinning slowly until the point stops moving in a circle. That is the center of the spindle axis -- but perhaps not the center of the chuck's own axis.

    But both of those are longer than the center drill, so you will have had to move the head up to get them in the space. And, BTW, it is possible that your column is truly vertical, but the head is slightly off so its axis is at a tiny angle to the column. Another reason for measuring with a machinist's square and a drill blank.
    Yes -- as someone else suggested, hardened steel rods from dead printers (or some older dead disk drives) can be used in place of the drill blanks -- if not badly worn.

    Give in the chuck somewhere -- a jaw with a chip under it, or something similar. Try another chuck. Or check with collets.

    Your No. 1 is not fully deep in the chuck, so you are only holding it with the tip of the jaws -- and they may be flexing in their ways. Try another chuck. Yes, more money for a chuck *does* mean a more accurate one.

    Yes -- flex of the jaws in the body when you don't have a shank contacting the jaws the full length into the chuck is a possibility.
    Again -- try collets.
    Good Luck,         DoN.
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wrote:
<BIG snip>
So, here is the result of 3 hours' work:
1) I found a dowel pin. At least I am pretty sure it is a dowel pin. It is pretty and shiny, 0.5" x 6", it has those black caps either end and on it it says USA made, 1/2". I do not know how I got it.
2) In the chuck, using a different indicator from last time, the TIR <3/8" under the jaws, 2" and 4" respectively was 0.001", 0.003" and 0.006". Re-tightening made no difference.
3) In a collet the figures were <0.001", 0.0015" and 0.002"
4) Repeat test with the same 3/8" drill I used before the TIR under jaws was 0.001"
5) I tried my 3/8" reamer. Under the jaws the TIR was the same but 2-1/4" down the shank 0.0115" !
6) The No. 3 center drill runs out at 0.008"
7) The No. 4 at 0.007"
8) I repeated the center finding tests. the two instruments varied sometimes by as much as 0.02"
9) As the punch mark have definite dimensions I tried just locating crossed lines. This is quite difficult: Just because you can see the lines on the bench does not mean you will see them clearly under the spindle, paint etc. notwithstanding. The results, confirmed with center drilling , were considerably worse than center-finding a punch mark, however small.
10) In view of the discussion re: spotting drills vs. center drills I thought it made more sense to abandon using No.1 and No.2 and I used No. 3 instead to make a small dimple with the pilot only. This should approximate a starter hole produced by a spotting drill. This was a definite improvement and the difference between the center drill hole and subsequent 1/8" twist drill position was only 0.005" on the Y axis only.
It should be noted that I used my machine screw length drills so the actual distance from the chuck jaws to the point was pretty much the same for both the center drill and the twist drill.
11) I cleared the table and returned to the dowel pin in the collet. I used the machinist square and could not see any deviation at all. The two squares I have pretty much agreed with each other. Note I did this along the X axis with the spindle in 4 different positions. The table is too small to do this effectively along the Y axis.
12) Tramming:
a) The machine was out of tram to the tune of 0.008" over the X axis. This was quickly corrected to <0.0005" with the head low. With the head high this increased to 0.0035". b) Moving the table along the Y axis produced no significant change. I interpret this as the table being flat. c) A spindle sweep in an arc from back to front, however, showed a change of 0.005" over the 2" available in the Y axis. I interpret this as the axis of the spindle being off in the Y axis plane.
Conclusions:
1) Do not use digital indicators for this sort of work. 2) Change the center drilling procedure as outlined above. 3) Grind a spotting drill? 4) To locate cross lines on a work piece it seems preferable to use optical punch first and then locate the center on the machine. This probably makes center finder and spotting drill unnecessary and can be done with a twist drill directly. 5) Consider acquiring better center drills. 6) Use collets whenever possible. 7) Ideally one should try to correct the spindle axis. From what I read of others' experience this is very difficult with this machine.
It is what it is. Like they say on South Park "I have learned something today". I should be able to minimize the errors by being aware of the pitfalls.
Thanks again for the help.
Michael Koblic, Campbell River, BC
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On Thu, 11 Nov 2010 18:52:24 -0800, snipped-for-privacy@gmail.com wrote:

=================different problem -- from what you describe in the complete post you are doing better than expected. For ultra precise work you need to go to a jig borer or grinder $$$$$$$. Google on SIP and Moore for examples http://www.weldershop.info/205/moore-jig-borer / for some discussion see http://bbs.homeshopmachinist.net/showthread.php?t 68
for one less expensive solution see http://www.wttool.com/product-exec/product_id/39550?utm_medium=cpc&utm_source=froog
and the one I have and like http://www.skidmoreengineering.com/index_files/Page1171.htm
Key is to use a very light hammer and just a tap to mark the metal, and then enlarge with a more robust punch and hammer. A mighty blast on the punch with the optical center finder will destroy the tip.
For high precision layout invest in a surface plate, a right angle plate, and a space block set and use this with a flat scribe (make from HSS lathe tool) for example http://www.use-enco.com/CGI/INSRIT?PMAKAd0-0100&PMPXNO”7969&PARTPG=INLMK3 http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKAc0-4050&PMPXNO•0511 http://www.use-enco.com/CGI/INPDFF?PMPAGEF1&PMCTLG http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO”8885&PMAKAA8-4525
Bright light at the machine tool will help.
Also consider http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA28-0976&PMPXNO%219105 after you are set up to do precision layout. Problem with smaller machines is quill to table/workpiece distance. cheaper http://compare.ebay.com/like/350387973770?ltyp=AllFixedPriceItemTypes&var=sbar&rvr_id 6965507857&crlp=1_263602_304662&UA=WKF%3F&GUIDéf106e41280a0aad4b75d47ff15ef4a&itemid50387973770&ff4&3602_304662 (Amazon.com product link shortened)
-- Unka George (George McDuffee) .............................. The past is a foreign country; they do things differently there. L. P. Hartley (1895-1972), British author. The Go-Between, Prologue (1953).
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"F. George McDuffee" wrote in message wrote:

=================different problem -- from what you describe in the complete post you are doing better than expected. For ultra precise work you need to go to a jig borer or grinder $$$$$$$. Google on SIP and Moore for examples http://www.weldershop.info/205/moore-jig-borer / for some discussion see http://bbs.homeshopmachinist.net/showthread.php?t 68
for one less expensive solution see http://www.wttool.com/product-exec/product_id/39550?utm_medium=cpc&utm_source=froog
and the one I have and like http://www.skidmoreengineering.com/index_files/Page1171.htm
Key is to use a very light hammer and just a tap to mark the metal, and then enlarge with a more robust punch and hammer. A mighty blast on the punch with the optical center finder will destroy the tip.
For high precision layout invest in a surface plate, a right angle plate, and a space block set and use this with a flat scribe (make from HSS lathe tool) for example http://www.use-enco.com/CGI/INSRIT?PMAKAd0-0100&PMPXNO”7969&PARTPG=INLMK3 http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKAc0-4050&PMPXNO•0511 http://www.use-enco.com/CGI/INPDFF?PMPAGEF1&PMCTLG http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO”8885&PMAKAA8-4525
Bright light at the machine tool will help.
Also consider http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA28-0976&PMPXNO%219105 after you are set up to do precision layout. Problem with smaller machines is quill to table/workpiece distance. cheaper http://compare.ebay.com/like/350387973770?ltyp=AllFixedPriceItemTypes&var=sbar&rvr_id 6965507857&crlp=1_263602_304662&UA=WKF%3F&GUIDéf106e41280a0aad4b75d47ff15ef4a&itemid50387973770&ff4&3602_304662 (Amazon.com product link shortened)
-------------------------------------------------------------------------------- REPLY: (sorry this is WML and *still* will not format properly)
1) I have the optical punch. I think I mentioned it passing in my conclusion. I certainly prefer it, more so now after I tried the hard way :-) 2) I have *two* bright lights at the machine but still could not see the damn lines! I think the surface of the scrap piece of metal had something to do with it. Still, I would not have had a problem with the optical punch... 3) Wow! $40 for the co-axial indicator! I have been eyeing them for a while. And he ships to Canada! Now that dollar is at parity...Duly bookmarked! 4) For the stuff I do I like the cheaper options. However, one has to pick one's spots.
Thanks again,
--
Michael Koblic,
Campbell River, BC
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On Thu, 11 Nov 2010 22:16:59 -0800, "Michael Koblic"
<snip>

<snip>
Are you using layout dye [dykem]? This makes a big difference when trying to see the fine layout lines. Also for precision work you will need a smooth flat machined surface. for some examples see http://www.use-enco.com/CGI/INSRIT?PMAKA‚5-8310&PMPXNO”3768&PARTPG=INLMK3 http://www.use-enco.com/CGI/INSRIT?PMAKAP5-1392&PMPXNO”1830&PARTPG=INLMK3 http://www.use-enco.com/CGI/INSRIT?PMAKAP5-1393&PMPXNO”2507&PARTPG=INLMK3 http://www.use-enco.com/CGI/INPDFF?PMPAGE10&PARTPG=INSRIT
Most shops use blue but red traditionally was supposed to work better on brass. I have used red and blue on aluminum, brass and steel and can't see any difference.
Most any mill supply should stock. The thinner the coat of layout dye and the thinner the layout lines [i.e. the sharper the scriber] the better.
-- Unka George (George McDuffee) .............................. The past is a foreign country; they do things differently there. L. P. Hartley (1895-1972), British author. The Go-Between, Prologue (1953).
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On Fri, 12 Nov 2010 02:35:37 -0600, F. George McDuffee

[...]
Yes to the dye, no to the surface - it was awful.
[...]
Michael Koblic, Campbell River, BC
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On 11/12/2010 12:16 AM, Michael Koblic wrote:

http://www.wttool.com/product-exec/product_id/39550?utm_medium=cpc&utm_source=froog
http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA28-0976&PMPXNO%219105
http://compare.ebay.com/like/350387973770?ltyp=AllFixedPriceItemTypes&var=sbar&rvr_id 6965507857&crlp=1_263602_304662&UA=WKF%3F&GUIDéf106e41280a0aad4b75d47ff15ef4a&itemid50387973770&ff4&3602_304662
--------------------------------------------------------------------------------
I couldn't resist, ordered it. Then I saw the link for the $28 US-made one on Amazon. except it was not the full kit.
George, thanks for the information and the links.
Rex
--
I can see 2012 from my front porch

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...
I use a fine-tipped prick punch (home-made from a broken tap) to make a very small dimple at the line crossing, followed by a center punch ground somewhat sharper than the angle of a drill bit. Usually the drilled hole position is within 0.005".
jsw
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On Fri, 12 Nov 2010 07:44:48 -0800 (PST), Jim Wilkins

I have grown partial to an automatic punch if I can see the marks well enough. That also needs a follow-up punch with something bigger. But for the tricky bits I have found nothing that beats the optical punch.
The punches are a kind of side issue to the original problem, i.e.. the center drill not agreeing with the twist drill. The obvious question was "which one hits the true center". That is when I discovered that defining the true center is not as simple as I thought it would be.
If I define the drilling point by edge-finding and measurement from edges on the mill will the center drill hit that point accurately? Will the twist drill? I know you cannot use the latter to start the hole, but if the center drill is off, the twist drill will be off also.
Michael Koblic, Campbell River, BC
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[snip]

What I do is to use an optical centering scope that mounts in the 3-jaw or collet chuck of the spindle, followed by a large spotting drill.
<http://www.use-enco.com/CGI/INSRIT?PMAKA$0-0404>
I have found that with this scope, it's more accurate to not center-punch the workpiece. I just center on the scribed lines and use the spotting drill to make the initial dimple. A center-punch dimple tends to pull the spotting drill sideways, reducing accuracy.
The other thing the scope is good for is locating zero-reference features on a workpiece, subsequently using the DRO to move to places where holes are desired. This is fast and accurate. I often scribe all the hole centers, to catch errors, but again I don't center punch the hole locations.
The only problem with the scope is that it was a bit expensive.
Joe Gwinn
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On Fri, 12 Nov 2010 18:39:13 -0500, Joseph Gwinn
[...]

You are not kidding about the price, but wow, what a cool toy! I can see that it would solve all sorts of problems.
Then of course you are relying on the center drill being on the mark which is something the OP questions :-)
Another tool that comes to mind and which nobody mentioned is this: http://littlemachineshop.com/products/product_view.php?ProductID&04&category10310429
I have heard conflicting opinions on it.
Michael Koblic, Campbell River, BC
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snipped-for-privacy@gmail.com wrote:

All in all, I don't regret the purchase, despite the whining.

The centering scope followed by a big (at least 3/8" diameter) spotting drill and then by a stub drill is the best way I have found to get the hole at the scribed location. If the location is off, oh well.
What is even more accurate is to use the DRO to locate a collection of holes with respect to one another, but this process usually starts with using the centering scope to set the DRO to a reference point on the workpiece.

I have never used one of these. I didn't buy one because I could not see how one could achieve 0.001" accuracy. Even if the laser beam focus spot is that small on the workpiece, my eyes are not that good to tell if the beam is exactly on the scribe marks. And I bet that the focal spot is dazzlingly bright and scintillates.
The catalog pictures all show a laser-pointer beam, which would be perhaps a millimeter in diameter (0.040" diameter), but the pictures may be artistic versus technical.
My guess that in my hands, accuracy would be more like 0.005" to 0.010". This is certainly good enough for woodworking.
With the centering scope, the limitations of my old eyes have little effect on achievable accuracy, and I easily achieve 0.001", probably less. This scope is how I discovered that the Millrite table gibs were loose, when I saw the table cocking slightly when drive direction reversed.
Joe Gwinn
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    O.K. The drill chuck, or its arbor is not true. Bent arbor, or burred chuck jaw.

    Better, but not perfect. How are your collets mounted? Since you don't use R8, presumably you have a Morse taper shank socket and a Morse taper holder for something like ER collets. (Or perhaps you are using Morse taper collets?) I can't remember the details of your machine at a distance like this. :-)
    Anyway -- since there is runout with the collet, and still a lack of parallelism to the spindle, check for burrs in the Morse taper socket in the spindle. (Try spotting blue (Prussian blue) in a very thin film on the Morse taper shank of the tool, then put it into the socket lightly, twist a few degrees, and pull it back out. Check the bluing for where it is rubbed off. If widely spread on one side, and in a narrow location on the other side, then there is likely a burr in the socket (which will need application of a Morse taper finishing reamer to clean off). Or -- there *could* be a burr on the Morse taper arbor instead -- patterns of blue built up around a clean spot could indicate that, and require a little stoning to remove the burr. There could be burrs on both the collet's arbor (assuming ER style collets) or the individual collet (assuming a Morse taper collet).

    Reamers (assuming a chucking reamer instead of one with a square tap wrench drive on the end) have a soft shank which can bend, so you can't trust that for indicating runout away from the chuck.

    Weird.
    Again weird. This is in the chuck, or in the collet?

    Still using the chuck -- or the collet?

    One of the little pocket sized gooseneck LED illuminators is nice for dealing with this. It has a magnetic base so you can stick it nearby and bend the neck so it illuminates the cross scribe.

    O.K. but note that you will have a chisel point on the tip of the center drill (like on the normal jobber's length drill bits), while the spotting drill comes to a sharp point.

    O.K. The machine screw length drills may have split points, so they can start more accurately even without a dimple or a spotting drill.

    O.K. The axis is pretty perpendicular to the table, then. Did you have a light behind the square and pin?

    Yes. And this can cause a drift in Y-axis position with different length drills or mills.

    You had been using a digital one? I don't remember you saying this. *Some* digital ones are more accurate than some mechanical ones. The Starrett "Last Word" mechanical if the bias spring is not applying bias throughout the range. (A bump on the side of the point can cause it to skip in the spiral, so there is a major deadband in the range.)

    How about *buy* at least one, so you know what it needs to look like? I recently got (from a sale flyer from MSC) a couple of 1/4" x 60 degree spotting/centering drills (MSC #FJ71332167). If the sale from that flyer is over, the "FJ" won't do any good, and the price will be back up to whatever it was.)

    Probably -- especially with a drill with split points. For larger standard bits, the chisel point may be wider than the dimple left with the optical punch, in which case the drill is likely to walk away from the punched center point.

    Consider acquiring at least one or two proper spotting drills, so you can compare them with what else you have and what you make later.

    Yes!
    It is certainly a source of error.
    Good Luck,         DoN.
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By taking the MT arbor out of the spindle and rotating it 180 degrees (required for arbors with tangs, obviously), one could take comparison measurements. Differences may reveal where the inaccuracies are.
I would be switching arbors and substituting a different chuck, too. After switching tooling, and another set of measurements, it should become clear where all of the runout is coming from.
One of those MT arbor blanks with just a 1" (or other size) head/stub on them, could be very helpful in checking out the MT socket relative to the spindle's center axis. I'd make a durable mark on the spindle and start checking runout on the stub, which would be located cloe to the end of the spindle at this time. The arbor stub OD might not be perfectly concentric with the centerline of the MT taper, but it should be very close if the arbor was finish ground between centers.
If the stub doesn't have a center hole, then it probably wasn't finish ground between centers, so a little touchup may be required. I'd then make a durable mark on the arbor in line with the previous mark on the spindle, and touch the stub with a die grinder stone (held by a rigid fixture mounted to the machine table) to make a small zone/pathway that's concentric to the spindle's centerline.
Measurment of the newly ground path should show nearly perfect concentricity. If the error is excessive, I'd probably suspect a very poor grade of bearings.
I suppose this procedure could also be used on a drill chuck arbor, since the grinding zone only needs to be small, and could be outside of the taper where the chuck body seats.
The previous steps would verify if the bore of the MT spindle socket is good, but won't help with the head/spindle-to-base perpendicularity issue.
--
WB
.........


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On Fri, 12 Nov 2010 18:20:28 -0500, "Wild_Bill"

I was thinking along those lines today and tried to remove the chuck from its JT33 arbor to do the checking. It seems to be glued on.

This is where I get confused: What is an "excessive" error? Looking at the Jacobs web-page their keyed chucks are guaranteed at best 0.003" TIR, some considerably worse. I seem to be within this figure.

True. I suspect at some stage I shall have to accept that one cannot make a silk purse out of a sow's ear :-)
However, going through this process has been helpful. At least I understand better where the sources of error are and even managed to reduce some of them with relatively simple adjustments.
Michael Koblic, Campbell River, BC
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The MT pocket in the spindle is supposed to be accurately centered and aligned to the spindle's centerline. The wide end of the MT taper can be checked for concentricity with a dial indicator, with an offset point or with a dial test indicator which allows the point to be positioned for a reliable indication. If the arbor MT socket isn't concentric with the spindle's centerline, this would be the first point of inaccuracy. As suggested earlier, the spindle bearings may contribute to runout errors.
In the exercise where an arbor is placed in the spindle, the machined surfaces of the arbor should (ideally) also be centered and concentric. If the arbor JT chuck taper isn't concentric with the spindle's centerline, this would be the second point of inaccuracy.. chuck (in)accuracy isn't involved yet. Substituting an arbor is much easier than trying to regrind a JT taper, so that's what I'd try if a particular arbor is introducing error, of say.. .002", because additional error can be expected from the chuck when it's installed. The earlier suggestion of making a light grind on the JT taper portion of the arbor, should prove to be very concentric to the spindle centerline, at least as accurate as the initial MT pocket runout test.
If the arbor has a tang, the arbor can be inserted in only 2 rotational positions (approximately 180 degrees apart). Placing a permanent mark on the spindle may be helpful in putting an arbor back in the more accurate orientation.
When the chuck is installed, it will most likey involve some additional inaccuracy.. a third point of inaccuracy.
Comments in a recent thread address chuck installation to an arbor. "How Long Would You Leave It In The Freezer" 11-4
When the arbor is out of a machine with the chuck seated on the JT taper, I generally place a drift in the chuck (end of drift in contact with the internal end of the arbor, chuck only tightened loosely), and with the chuck/drift pointing down, briskly wham/tamp/slam it on a very solid surface. The inertia breaks the taper's grip, and the arbor pops out of the chuck taper. So far, I haven't needed to resort to the heat or dry ice methods.
The same force seats a chuck on an arbor very effectively, when the arbor is removed from the machine (no drift required). I generally tamp the arbor tang on a scrap of aluminum or brass, placed on a very solid surface to seat the chuck JT taper.
--
WB
.........


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wrote:
My WML hates you. It swallowed your post again. OTOH it is not prejudiced, it swallowed my last reply, too.
[...]

I did some repeats after the tramming today. The collets are Chinese ER look-alikes on a MT3 shank.
Today the dowel pin run perfectly parallel at 0.0015" in a collet.
I put the No. 3 and 4 center drills in their respective collets and they run at 0.001" both.
I put the chuck back in. The dowel pin run 0.002 at "zero" and 4"! But then I repositioned it slightly and re tightened and the wobble appeared - 0.004" at 4".
I tried the center drills: No.3 was better initially at 0.003", but re tightening I could make it 0.005".
No. 4 was 0.007"
For the sake of comparison I put the dowel pin in my drill press: 0.0035" and 0.007" at "zero" and 4".

I tried this with the chuck arbor MT3 taper. I got somewhat inconsistent result but no large areas. Nothing I would want to attack with abrasives remembering that I could screw things up rather than help.
I thought it would be helpful to check the run-out of the JT33 arbor and tried to remove the chuck. I made a wooden jig to support it but it seems that the helpful Chinese glued the thing in so I desisted before things got out of hand.

A lesson learned...

See above. I am beginning to think that the main problem is how this chuck grips things in the jaws. I think it likes longer shanks. The area between the flutes on the center drill is quite short. In a collet it does not matter.

Chuck. I forgot to do the collet test today.
[...]

I put a piece of white paper behind.

[...]
I did the first time. It was a part of an existing set-up. They are nice for some things, axis movement, measurements over 0.1", but for this analog is better IMHO.

Probably right. Getting the point exactly co-axial is probably something I could not do with a Dremel.

In that case I would probably be drilling a smaller pilot hole anyway.

[...]
One has to consider at what point the error generated this way exceeds that introduced by the operator.
Michael Koblic, Campbell River, BC
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    :-)
    It knows that I do not trust Windows and reciprocates. :-)
    [ ... ]

    O.K. So chips on the surface of the MT3 shank or in the socket can introduce errors.
    However -- you might test the runout inside the cone of the adaptor which supports the collets.
    Of course -- chips in the ER taper can introduce errors too, as can chips in the collets themselves.

    Great!
    Also great!

    Since you are using ER style collets -- you should be able to cover the whole range that the chuck can hold (assuming a full set of collets), so why not *use* the collets?

    How much could you move the stationary spindle by pushing sideways on the chuck in various directions? Usually, the fit of the quill to the headstock in a drillpress -- especially an import one -- can be pretty bad.

    O.K.
    The normal method for removing a chuck from an arbor is to use a set of Jacobs chuck-removal wedges.
    Check MSC part number 08592941 to see an example. (These are for the #3 Jacobs taper. There are four different sizes depending on the size of the Jacobs taper being removed -- and for some of them you need two different sets to make a removal set for a particular size. These are tapered in thickness (narrowest at the tips of the tines) and are placed between the chuck and the shoulder of the Morse taper adaptor from opposite directions, and are squeezed together with a vise. If the Morse taper big end is smaller than the Jaobs taper in the chuck, you may not have a shoulder to work against, and will have to destroy the arbor by drilling a cross hole for a pin for the wedges to work against.
    The MSC catalog page may list what combinations are needed for what Jacobs tapers -- or it may be that I saw it on the Jacobs web pages.
    [ ... ]

    Jacobs style chucks are made to grip all the way down to the end of the shank -- and if your tool won't seat fully back for whatever reason, it will not be as good a grip, and the jaws may move in their guides.
    You might look at MSC item # 08592545 -- which is a rebuild kit for some particular sizes of standard Jacobs chucks. (Replacement jaws and replacement split threaded ring which feeds the jaws.) Since MSC's web page has just gone offline, I can't tell more about it at the moment. The best thing is to visit Jacobs' web site and read up on rebuilding their chucks, then make the tools needed to press the chucks apart and actually *see* how they work.
    [ ... ]

    :-) A good analog one can read to a tenth of a thousandth.

    Exactly co-axial with the spindle -- *sure* until you remove it from the chuck. :-) But generating the flutes down to the point is a major trick.

    O.K.
    Enjoy,         DoN.
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wrote:

This one it let through. The Forte Agent formats better. OTOH it has other issues.

How do you drill a e.g. 7/64" hole with a collet? I guess start the hole with a spotting drill in a collet and then switch the arbors...OTOH if one has a proper spotting drill with a long enough shank the procedure might not be necessary (see below). It certainly seems the way to go if starting the hole with the center drills. Which I won't 'cos I know better now.

A fair bit.
[...]

OK, what is wrong with my method?
1) Prop the chuck upside down on two blocks of wood by its shoulders (where the wedges would go, too) 2) Open up the chuck to its widest. 3) Use an *aluminum* cylinder of a diameter just slightly less than the diameter of the JT33 arbor through the open chuck jaws. 4) Hit with a BFH

There is less than 3/4" of intact shank between the ends of the No. 4 center drill. The flutes start either side of it. This is enough for the collet but clearly not enough for the chuck. It gets worse as the center drill gets smaller. I think I mentioned that with the No. 1 it is ridiculous. Never again No. 1 in a chuck! .

Would they then work any differently on the center drills?

What? You mean my $9 ones won't?

Probably not worth the effort spending the time producing inferior result. Fastenal show some US made ones. I shall see if the local branch will sell me one (rather than a packet of 100).
Michael Koblic, Campbell River, BC
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