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.
My WML hates you. It swallowed your post again. OTOH it is not prejudiced, it swallowed my last reply, too.
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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.
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I put a piece of white paper behind.
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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.
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One has to consider at what point the error generated this way exceeds that introduced by the operator.
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.
It knows that I do not trust Windows and reciprocates. :-)
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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.
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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.
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:-) 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.
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.
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.
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.
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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).
I wonder whether the WML is trying to do some spam blocking, and interpreted something which I either posted or quoted as spam? I know that the longer the incoming e-mail the greater the chance that my Bayesian filtering will decide that it is spam -- and if it is also in HTML, it is almost a certainty. (Since I don't read HTML with my e-mail client (and am glad of that), I consider it unnecessary, and a source of serious bloating in the messages. :-)
You said that they were ER style collets. ER stands for "Extended Range" and most of the collets cover a 1mm range (e.g. 7-8mm, and also marked with a range of fractional sizes).
These are unlike 5C collets, R8 collets and Morse taper collets (which all have a very limited gripping size range), so your set should have a collet which will include 7/64" in its range. Let's see -- 7/64" is 0.1094", which is 2.7781 mm -- so look for a collet marked 2-3mm. Some of my ER-25 collets at the small end switch to 0.5mm ranges, so you may have to look for a 2.5-3.0 mm one depending on your set.
One of the advantages of spotting drills over center drills in chucks is that they are not double-ended, so they bottom nicely in the chuck.
Thus your measurements are limited by that.
Your method assumes that the chuck has a through hole to the arbor socket. Most do not. Only the ones which are threaded onto reversible electric drill motors are likely to have a through hole, because they use a left-handed screw into the end of the spindle to keep the drill chuck from unscrewing in reverse.
Now -- you *could* open the jaws fully, mount a drill bit vertically in the mill vise (assuming that your vise has V grooves to hold it firmly and vertically), center the chuck over that (using the jaws to feel for the flutes and then retracting the jaws fully), and then drill through the web.
But sometimes the way to remove a stuck arbor of the wrong size from a chuck is to saw off the arbor, drill through *it* and tap for zerk style grease fittings, and use a grease gun to fill the cavity with grease and use the hydraulic pressure to pop the stub of the arbor out. This would (obviously) not work with a through hole in the chuck body. :-)
While the spotting drills, since they are single ended, can use the full length of the jaws for contact.
Well -- I was not advising you to *purchase* the repair parts set. Just look at the Jacobs web site to see how to take a chuck apart, and then do so to show yourself how the chuck works. Then you can see how a tool held only in the tips of the jaws will likely cause deflection inside the chuck.
Since your chuck is of Chinese manufacture, the odds are they they would not fit your chuck anyway -- metric dimensions instead of inch dimensions are likely -- unless they are a total clone of Jacobs chucks. (Note that some chucks from out of the country also have a socket which is not a Jacobs taper -- but something similar with different nomenclature, different dimensions, and perhaps even a (slightly) different taper.)
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What are the divisions on the scales? The ones which I am talking about have divisions to 0.0001".
The small ones with the lever style contact point lose accuracy unless the lever is at a specific angle. I think that is 30 degrees for most, and at least one brand (no -- I don't remember which brand), is accurate with the lever parallel to the work surface. To check what the proper angle is for what you have, try different angles, and slide some shim stock under the point to see if it moves the proper distance.
It may be worth the trouble as a learning exercise, at least. But as long as they are inexpensive enough, buying new is easier. :-)
Fastenal seems to have them -- and here is the part number of a
1/4" shank 1-1/2" long one: 7000098
And you are in luck -- it says "Package Quantity 1 (EA)" -- at least on the web page. :-) They are saying "Wholesale Price: $6.63" which is more than MSCs sales flyer price -- but if you can order it within Canada, you don't have the brokerage problem which things shipped from the US to Canada by UPS have.
The news part of WML is completely different from the e-mail part and behaves differently. There is no consistency. It has blocked two of your posts and allowed two through. The same with my own!
I have yet to discover a spam filter on the e-mail side if only to disable it. Permanently. I do not need it. I am still capable of deciding what I do or do not want to read. Look what happens if you allow the stupid machine to decide for you!
1/8, 3/16, 1/4, 5/16, 3/8, 1/2, 9/16, 3/4 (inches). I guess for 7/64 you would use 1/8"?
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I could swear I can see the bottom of the JT33 arbor through the chuck (hence picking an aluminum bar with a smaller diameter). However, now you have introduced doubt...
0.0005" is the best I can hope for.
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Fastenal say many things on their web-site which do not necessarily reflect reality up here. I shall give them a call.
Well ... based on the e-mail headers, I have sent myself spam. :-)
They even forged the IP address of one of my mail servers as a machine name (though the *real* IP address is captured by my e-mail server anyway.)
Indeed -- and not letting you select for yourself is even more offensive.
Yes -- from a quick calculation, that is only 0.396mm larger, so it should be within the range needed.
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Remember that the cavity is drilled (a shallow cone left by the tip of the drill)-- along with three other holes at an appropriate angle to hold the jaws.
If you are actually seeing the end of the arbor, it should be flat with a center drill hole in the end, since the taper was ground between centers.
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O.K.
O.K.
Good luck with the purchase.
I would actually get two (I did actually get two from MSC) so there is a spare if one gets the rather pointy tip broken.
At least the Forte Agent looks like it might do the job. Like anything it needed a bit of tweaking but at least it does not miss posts and it formats the replies properly. Probably worth $29.
That is what I *thought* I saw...
Over the years I have made it a policy to have two of everything if possible so yes, it will apply here too.
I was quite nervous when we sold our second car...
I have heard good reports about it -- but I can't use it, because I don't run Windows.
What I am using for usenet news is slrn. For e-mail mutt.
It may be -- someone else may have drilled it out beforehand if it is a second-hand chuck and arbor. Or -- the Chinese may do things differently anyway. :-) I'll have to remember to check the inside of my
5/8" Jacobs "style" chuck which came with my drill press back in the late 1970s.
[ ... spotting drills .... ]
Good!
I can imagine. When working on a car, it is always nice to have a back-up car. :-)
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