Bridgeport milling questions

Hi, I hope you are all well.
I'm relatively new to this so please accept my apologies if I make some errors.
I have previously had some experience, under limited supervision from
a trained engineer, on the Bridgeport. I've now purchased one for my own use which has been supplied with some tooling.
All of the (rather ragged) end mills are screw shank and there is a chuck with various diameter tapped holders (collets?). Also supplied was a box of R8 collets (2mm - 20mm from memory).
I've previously used the screw-shank variants so I'm comfortable with them however I have no experience with the collets.
A few questions if I may:
a) Which method is better?
b) Dependant on a suitable diameter collet, do all "Plain shank" end mills fit in the R8 collets?
c) When I purchase new end-mills, which of the above would you recommend?
Thanks & regards, Mike
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MikeG wrote:

Mike,
Sounds like you have a Clarkson autolock holder, are you familiar with their use?.
a) The Clarkson holder for the screwed shank cutters is better than collets as the cutter can't pull out under heavy cuts like it can with a collet.
b) As far as I know all cutters, be they screwed shank, Weldon (set screw retention), or plain shank are OK in collets. I have threaded shank and a few Weldon types and regularly use them in collets when the guaranteed retention given by the Clarkson holder is not required. Just make sure the cutter is inserted so the collet is holding the plain section.
c) Depends what you're doing. If you're not taking heavy cuts then the threaded shanks for the Clarkson are not required but I buy most of mine as threaded shank in the larger sizes. 16mm being the largest I normally use. Not noticed much difference in the price, I often buy tools when on sale from J&L UK.
Hope that helps.
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On Wed, 10 Dec 2008 11:42:53 +0000, David Billington

Hi David,
Many thanks for your detailed reply. I have noted your comments.
I've used the screw shank cutters and holder before but I didn't know the correct name for them - thanks. Looking on the web, the autolock inserts appear to be threaded but the ones supplied with my machine aren't. They just slip into the holder and are held in place by the retaining collar, tightened by a spanner. Is this still a "Clarkson autolock"?
The engineer who was showing me the ropes recommended that the screwed end of the cutter protrude slightly (maybe 1mm+) from the end of the holder before it was inserted into the sleeve and tightened. Is this correct?
I haven't managed to break anything yet and I'm keen to keep it that way!
Kind regards, Mike
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MikeG wrote:

Mike,
I jumped to the conclusion you had a Clarkson autolock holder when you said threaded shank cutters but was wrong by the sound of it. Have a look here for some different collet types. http://www.arceurotrade.co.uk/Catalogue/Collets . At a guess I might think you have an ER collet holder as they don't have threads in them and are quite common, see http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collets-Collet-Chucks .

Sounds good.

Always a good strategy.
Cheers,
Dave

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On Wed, 10 Dec 2008 12:53:19 +0000, David Billington

<snip> >> Hi David,

Hi Dave
Again, thanks for taking the time to reply.
I may have fed you a bum steer with my description of the collet - I think it is a Clarkson Autolock - this is link to a picture.
http://www.mgarner.co.uk/Collet.jpg
As an aside, please could you confirm that this is a "J" type head?
http://www.mgarner.co.uk/Bridgeport.jpg
Thanks & kind regards, Mike
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MikeG wrote:

Mike,
That's a Clarkson autolock style holder. I have one which is not genuine Clarkson but had found no fault with it.

That's a J head with 2 speed motor by the look of it. Have a look here http://www.lathes.co.uk/bridgeport/ .
Cheers
Dave

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On Fri, 12 Dec 2008 10:48:09 +0000, David Billington
<snip>

Brilliant - thanks for the info, it's much appreciated.
Kind regards, Mike
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On Sat, 13 Dec 2008 16:20:16 +0000, MikeG
Be aware that the method of tightening a Clarkson collet is not in my mind intuitive! The correct way to fit a cutter is as follows Screw the cutter into the collet a few turns. Insert the cutter and collet into the nose piece. Screw the nose piece into the chuck body until the mating flat faces touch. If the position of the cutter stops this then unscrew the cutter until the nose piece can be screwed up to touch. Screw the cutter up until it is solid. Tighten the nose piece with a spanner.
Richard

Richard
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Richard Edwards wrote:

I was taught to leave a slight gap between the body and closer, screw the cutter in till it bottoms, then tighten the closer. This still leaves a slight gap but holds the cutter hard against the centre post.

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Richard Edwards wrote:

Richard,
It seems I was taught incorrectly how to use a Clarkson autolock holder and you above post is the correct technique. A quick google turned up the following which I shall try the next time I use it.
http://www.denfordata.com/bb/viewtopic.php?p528&sidnc8c81a5905b2c935181bd3b1810519
Cheers
Dave

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    Thanks. I had not known that. If I ever get a set of mills to match my holders, I'll have to remember that.
    Enjoy,         DoN.
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    [ ... ]

    [ ... ]

    That certainly is -- or a clone if such are made. You will probably find "CLARKSON" engraved in the edge of the nose-piece.

    I think that is a J-1 tyle -- the side covers say that it has step pulleys. Look at the text stamped in the left-hand of the two nameplates side by side. If it starts with a 'J', then you do have a J-head. The '1' would be a 1 HP motor. Or maybe the serial number is under the gray paint lower on the head.
    Mine is a J-2 head made for a CNC machine (BOSS-3) so the feed hardware is replaced with a ball screw surrounding the quill, and the motor is hung from the underside of the casting instead of the upper side, as well as mine having a variable speed crank in place of your step pulleys.
    If it has an R8 spindle, I don't think that it can be an M-head. I think that they used Morse taper collets instead.
    Enjoy,         DoN.
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Thanks for providing a picture of your disassembled Clarkson Autolock collet parts, Mike. I haven't seen them before, and I wouldn't have known what they were, if I did see them.
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WB
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    What is not shown by the photos is that there is a thread on the shank end of the end mill (just the last 3/16" or so) and a matching thread on the bottom of the collet.
    The center hole in the shank end of the edn mill engages the center pin in the bottom of the holder's pocket, and when the nosepiece is screwed in the taper inside the nose piece closes the outer end of the collet to firmly center the end mill.
    There is no way that a right-hand end mill can come out of the holder with cutting forces. (Hmm ... I wonder whether there are left-hand cutting end mills for the Clarkson system, and if so, whether they have correspondingly threaded collets?) Anyone out there ever seen left-hand end mills and collets for the Clarkson system?
BTW    When I first started searching on eBay for Clarkson holders and     end mills I was driven nuts by constant hits on "American Idol"     DVDs. I had no idea why, never having wasted my time watching     that show, until I saw that they were featuring a "Kelly     Clarkson" as a singer. :-)
    Enjoy,         DoN.
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Thanks for the additional details, DoN. As I looked at the parts I wondered if this tooling could be used to drive a tap for tapping, or if the threaded parts would just separate if the spindle was reversed.
But then, I don't know if it's even practical to tap threads with a Bridgeport mill.
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    How would you deal with the needed feed per revolution? This is mostly a CNC type job with a rigid tap holder. (After all, it takes a lot of force to pull the spindle down with the tap threads, so it is more likely to break the tap or strip out the starting threads.

    With a manual machine -- yes with the proper accessories.
    Look at the various tapping heads (excluding the rigid ones). A good example (and what I use in two sizes to tap even on a drill press) are the ones made by TapMatic. It is a cylinder mounted between however you drive it (I use a MT-2 shank in my drill press, or would use a collet or a specially machined R8 or NTMB 30 or 40 shank on my mills) and the special tap collet chuck which has Jacobs Rubberflex collet (typically two sizes to cover the range for a given tap chuck) to hold the tap concentric, and a pair of steel plates which clamp down on two flats of the square at the back of the tap for driving it.
    There is an arm protruding radially from the bottom of the cylinder, which needs to contact some part of the machine to prevent the whole outside of the cylinder from rotating.
    The collet spindle has quite a bit of end play, and three effective positions.
1)    When the tap chuck is fully withdrawn, the chuck rotates at     the same speed as the drill press or milling machine spindle,     and allows a certain amount of motion to allow the tap to     self-feed a certain amount. Normally, you feed by hand at about     the speed that the tap feeds into the workpiece. (Use a gun     tap, of course, not a hand tap which needs frequent reversal.)
2)    In the middle of the range, it disengages a dog clutch in the     housing, and allows the tap to stop while the spindle continues     to rotate. Normally, you set the depth stop on the machine to     stop it before you reach the end of the threads on the tap, or     before you reach the bottom of the hole on a blind hole.
3)    When you start to withdraw the spindle, you engage a set of     planetary gears in the housing which starts the tap rotating     backwards at a somewhat higher speed than the spindle's forwards     direction.
    With your other hand, you squirt a good tapping fluid on the tap     just before it enters the hole.
    As I said above, I have two sizes of these TapMatic heads.
A)    The smaller one goes from an 0-80 to a #10 or #12 -- and can     handle 1/4" in some materials. This one has an adjustable     torque limit clutch. You adjust it so it just barely does not     slip with a *new* tap and in the workpiece material which you     are using. When it starts to slip, it is time to replace the     tap, because it is getting too dull to trust in your workpiece.
B)    The larger one will go up to 1/2" taps, and instead of the     torque limit, it has an adjustment of the free feed before the     dog clutch disengages. This is better when you are tapping near     the bottom of blind holes. Otherwise, you leave it with lots of     travel (1/8" or more, IIRC) when tapping through holes.
    I believe that you can get both styles in both sizes, but when getting things from eBay auctions and swap meets, you take what you can get.
    Some of them have a Jacobs taper in the back to accept your choice of Morse taper arbor or whatever fits your machine.
    Both of mine have a threaded hole instead, and I had to thread No. 2 Morse Taper blanks to fit -- each has a different size of threaded hole -- and the first one I got (the smaller one) had an adaptor with it to fit a Turret drill press -- which is probably why I got it for such a good price from eBay. :-)
    There are other brands which are well thought of, but I can't remember the names at the moment, since I don't have any examples. :-)
    Enjoy,         DoN.
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The only tapping under power that I've done has been on lathes, DoN. I thought it might not be practical to tap on a Bridgeport with the tap secured by a collet.
Most of the time, I tap by hand with a tap handle, or using a drill press like a tapping fixture hith a hand crank (without using the motor) with the taps held in the chuck. No, not the slippy method, I've ground 3 flats on the shanks of a handfull of taps for holding them in chucks. A hub for the hand crank is permanently installed at the top of the DP spindle and the crank fits in place by sticking the 2 protruding pins in the crank handle into 2 holes in the hub (no screws or other fasteners involved). I can loosen the belt, disengage the quill return spring, and attach the crank in about a minute.
If one were to use one of those shop-made telescoping tap holders for a lathe tailstock, I suppose that the tap self-feeding itself wouldn't be an issue whether it was used on a mill or drill press.. correct?
I've seen tapping heads like the TapMatic in catalogs and more recently in videos, and have read numerous RCM posts about how slick they are. I've read a lot here in RCM, and when contributors like yourself, and at least several others, take the time to write detailed commentaries about metalworking topics, I always take the time to read them.
As I've stated before, anyone that spends any significant time "on RCM" would be doing themselves a great disservice if they aren't reading all the really good comments concerning all the widely varied metalworking topics.
Some folks like to read a morning paper.. I read RCM instead, nearly every day, maybe missing a couple per month.
Fortunately, most of the contributors of the metal related content are talented at describing their thoughts well in text. Perhaps most fortunately, those frequent contributors have been willing to stick around to continue sharing their experience(s) and helping others, despite all the non-metal noise that takes place regularly.
The anniversary of the loss of one of the great RCM contributors will be remembered/observed soon.. RIP Tnut
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    Not just secured by a collet -- but you might be able to use a releasing tap holder (made to be used in late turrets and in automatic screw machines) as long as you carefully set the depth stop based on where the dog clutch releases so you don't drive down into the bottom of the hole and break the tap off in the workpiece. :-)

    O.K. You know that there is a keyless chuck by Albrecht which has diamond dust impregnated jaws, so it *can* grip a tap or a mill without slipping. And -- there are versions of the Albrecht chucks which are designed to lock as well. Both features are only found on quite expensive Albrechts -- usually with R8 shanks instead of a female Jacobs taper to allow interchangeable arbors.

    Nice. I think that the quill return spring on mine would be the slowest to disengage and reset later.

    The telescoping ones which I have seen have been designed to slide on a rod held by the tailstock, and to be prevented from turning by gripping either a knurled surface or a short T-handle. When the tap reaches the proper depth, you release the handle and let it spin.
    But the releasing tap holders (commercial product for older turret lathes and for automatic screw machines) could be used in a mill. You stop feeding and the threads draw the tap down just a little more to disengage the dog clutch. Then you stop the spindle, reverse it, and pull up (many are designed with a directional dog clutch, so it will hold in reverse even though it has released in forward.
    I'm familiar with these because I have a bed turret (replaces the tailstock) for my 12x24" Clausing, and I use it form time to time with turret tooling acquired from eBay auctions.

    Generally, if I have more than two or three holes to tap (and I'm not on the lathe) I'll use the tapping head. Particularly nice when I had to tap about 30 1/4-20 holes in 3/16" thick steel to make a new apron for the 24" DiAcro shear which I got last year. Any manual method of tapping that many holes that large in steel gets old fast. :-)

    [ ... ]

    Most of us like sharing what we have learned -- to save others the time which we spent the hard way. :-)

    Well ... as an example, my killfile zapped about 2/3 of the articles. It was worse prior to the election - 3/4 was being zapped at a time. :-)
    If you chase down a version of slrn for your system (I believe that it is available for Windows as well as unix/linux systems and Macs), and drop me an e-mail, I can send you my current killfile to give you a quick start. (I'll strip out the parts which apply to other newsgroups.) Among other things, I have a lot of blocking by IP range to keep the Chinese shoe knockoff vendors out of my newsreader, and the various Indian scams.

    (Hmm ... were you posting under a different name back then?)
    Indeed so.     He is still missed.         DoN.
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I was thinking that I had seen some of the telescoping shop-made tap guide/holders for lathe tailstocks that had a key or pin to keep the tap from turning, but allow the tap to self-feed into the rotating part. Stopping the spindle would then be the method to stop the feeding.
I suppose if I happened to stumble upon a tapping setup with the dog clutch, I'd be inclined to buy it because they sound versatile.
Oh, the other tapping with power that I've done has been #6-8-10 taps in steel panels for mounting relays and controls.. works a treat for lots of thru-holes. I wouldn't wanna try it with a non-reversing drill motor though.
I was aware the diamond dust filled jaw chucks existed, but don't think I've ever paid much attention to the pricing. I just got a nice, used, 3-piece set of TRW USA tap handles with the opposed handles, and a moving jaw that closes on the square section of taps, but like you said, hand tapping a lot of holes gets old fast.
When I was lurking and just observing RCM interactions/frictions, Tnut, Fitch, Albrecht and numerous others were regulars. When I started posting in RCM I was probably with the ISP tcis or usachoice, then Goog, and Teranews briefly, using the moniker kwag98 initially, then others similar to the present one, as WB was my sig for a number of years of posting in sci.electronics.repair.
The non-metalworking posts don't cause much aggravation for me, as I can just ignore them, since most of them generally, and the participants' opinions on those topics, aren't of any more interest to me than the spam sales messages.
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On Mon, 15 Dec 2008 11:56:48 -0500, "Wild_Bill"

Hey WB,
Most of those tailstock tap accessories have two slots opposite one another in the carrier of a size to allow a T-tap handle to slide into it. In operation, the "depth of threading" is set by advancing or retracting the tailstock and barrel to set a point of release for the T-handle, which allows the T-handle to just spin when it reaches the preset depth by moving/being pulled out of the slots so it is no longer held by the tailstock carrier.
Take care.
Brian Lawson, Bothwell, Ontario..
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