Morse Taper Removal

[Jim GreetheadParticipant @jimgreethead]

Sorry, I should have said that the collet chuck came loose. It came out of the spindle because the drawbar had unscrewed.

 

It was a bit odd because it came out, the cutter gouged the job and then it bounced back and tightened up on the drawbar. So when I stopped the machine and checked, the drawbar was tight.

 

Thinking there was something mysterious going on, I started work again. When it happened the second time, I twigged. And tightened the drawbar with a spanner. That fixed it.

 

It is possible that the inertia of the handwheel causes it to loosen when the spindle accelerates. That happened when I used a steel handwheel. So I swapped it for an aluminium one having less inertia. It seemed to be ok but maybe several starts caused it to loosen.

 

Next step is to try a handwheel with less inertia but more hand holds – like the tap handle shape.

 

I am reluctant to give up altogether because it is just so much more convenient than the spanner and hammer method.

 

Jim

 

[Peter G. ShawParticipant @peterg-shaw75338]

Jim,

 

On the Warco MiniMill and other Sieg X2 type milling machines, the complete head moves up and down the rack. What this means is that the actual spindle is rigidly located vertically (and horizontally) by the bearings inside the head hence any bashing on a drawbar transmits the shock onto the spindle, then via the bearings onto the head itself before reaching the rack which is part of the column.

 

Another way of looking at is to compare it to the lathe spindle. OK the lathe spindle is horizontal and doesn’t move, but just the same, any bashing on a drawbar inserted from the rear of the lathe spindle must eventually end up being transmitted via the lathe headstock bearings.

 

Actually, I can’t see how in your description the shock load does not go through the bearings as unless the rack is cut into the rotating spindle, then the bearings must be brought into play. I have a, ok cheap, vertical drill which has a rack cut into an outer sleeve which moves up and down inside the fixed head. Within this outer sleeve, there is the spindle, supported by two bearings, top & bottom. The spindle itself also slides up and down inside a square spline which is directly connected to the pulley drive system. The result is that if the rack is locked, any vertical shock loading on the spindle will pass from the spindle to the outer sleeve, and hence the rack via the bearings.

 

Regards,

 

Peter G. Shaw

[David LittlewoodParticipant @davidlittlewood51847]

I would question whether shock waves only travel in straight lines, as is assumed by some posters above. Personally, I avoid giving anything other than very light taps on tapers, usually to remove drilling chucks with no drawbar.

 

David

[Gordon WParticipant @gordonw]

One must assume that the designers of machine tools allow for the extraction forces when specifying the bearings ? BTW one short, sharp crack with a hammer usually causes less trouble than many “gentle” taps.

[S.D.L.Participant @s-d-l]

At technical college many (35) years ago it was always a good sharp tap with a lead hammer.

 

Most workshops I have seen a similar or a big copper mallet.

 

Was always told 1 big tap with a decent soft faced hammer was better that lots of little taps.

 

Steve Larner

[DustyParticipant @dusty]

Gentlemen remember the old adage ‘never force anything, always use the correct size hammer’

[Jim GreetheadParticipant @jimgreethead]

Peter, of course you are right. I have just checked the drawings for my mill (why didn’t I do that before making an idiot of myself) and the bearings do, indeed, take the shock load. Pardon me while I take my foot out of my mouth and bash my head against the wall

 

Gordon: That sounds sensible. They don’t provide any alternative so perhaps they have allowed for it.

 

Steve: I did a course at the local Tech recently and this was still the method of removing chucks. One thing I did notice was that, as you say, it was usually a lead or copper mallet rather then the steel lump hammer I have been using. Are the soft hammers more gentle on the machine?

 

Dusty: Good advice. And following Gordon’s admonition to use one big whack rather than a lot of little ones, I guess the correct size hammer is the biggest one at hand.

 

And lastly, thank you all for your contributions and for keeping me on the straight and narrow. I appreciate it all.

 

Jim

 

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Jim, the main reason for using soft faced hammers is for the hammer to be the sacrificial element in the operation, that is that whenever you use a hammer for hitting things deformation occurs somewhere. If you continually hit a rivet for example, it will deform into the required shape to do its job, whereas the hammer being much harder will not deform by any significant amount, and this is an ideal situation. When hitting the head of a drawbar on the other hand, you do not want the hexicon head to deform so that eventually you can’t get your spanner on, therefor the soft face hammer deforms and becomes sacrificial. The resultant energy transmitted into the the job in hand will be about the same. (Hammer weights, swing force and area of hit taken into consideration)

 

With regards hitting the drawbar to remove chucks etc., I don’t think you’ll do much damage to the bearings in normal use, providing you are not using a sledge hammer to crack a monkey nut. As has been said one short sharp blow rather than lots of little ones.

 

Regards Nick.

[Jim GreetheadParticipant @jimgreethead]

Thanks Nick, that explains it

Jim

 

[GoCreateParticipant @gocreate]

Here is a simple solution by a Sherline owner.

 

It’s cnc machined but can easily be modified for other machines and convensional manufacture. Does require the spindle to have some extension available though so, in this respect, may not be a universal solution.

 

Draw bar loosening tool

 

 

Nigel

Edited By tractionengine42 on 17/12/2011 03:21:26

[BERTOParticipant @berto]

Jim,

I suspect the reason your handwheel came loose is not just inertia but because you have two right hand threads working in unison and not pulling against each other as they were designed to do .

If you screw the threaded rod into the rear of the collet chuck until it bottoms out then loosen 1 1/2 turns, now screw your handwheel down untill it touches the top of the spindle making sure the drawbar does not turn then use a locknut and some loctite to lock the handwheel to the threaded rod .

This way hou have created a drawbar with a large handwheel that will work the same way as a normal drawbar and only using 1 thread to pull the chuck up into the spindle .

You can still use the slide hammer idea as it will sit on top of the handwheel as before all it means is when you turn the handwheel to loosen or tighten the drawbar the drawbar also turns and screws in or out of the chuck .

 

Nigel ,

That was one of the methods i was thinking about for my HM46 as it has a splines on the spindle and to use a backing out nut i would have to disassemble the machine so i can turn a thread on the end of the spindle .

I could make a splined collar easily enough .

The collar idea is now in the lead !

 

IAN

[jomacParticipant @jomac]

Hi ,Peters right. shock loads to the bearing and gears/splines, is a NO NO, also not mentioned is the fact that in a small square columb mill the dovetails also take a hammering, which is why you can have problems in tramming the mill parallel. In some cheap Asian mills that have round columbs, the verticle round tubes can get bent at the bottom where it fit into the base, I know cause I had an adjustable devise that had verticle and horizontal round hollow tubes, the tubes were too thin and the casting were diecast, so both were bent and distorted. So how do I cope, well the draw bar has a Nylock nut and the draw bar has a square top, all I need to do is set the nut to the right depth??? and lock it down to this. And most importantly !!!!!!! I have a heavy piece of hardwood or a heavy but soft piece of metal, that I put under the quill, its only then that I belt the crap out of it, thus no problems with bearings or splines getting damaged. By the way hasnt this subject arisen before, and no one read it.

Merry Xmas and Happy new year.

John Holloway

I

[DerilParticipant @deril]

There is an alternative to blows at the drawbar.

Generally some form of extraction may be arranged at the work end of the taper.

For a collet holder with a closing nut a simple piece of tube round the holder between the nut and the quill will allow easy extraction by tightening the nut after the collet has been removed and the tube fitted.

For tools such as drill chucks and boring heads on morse tapers there is often enough unused length of taper outside the housing that a very short length of screw thread- from a salvaged water fitting- may be super glued on just clear of the housing.

A thin nut from the same salvage again allows easy extraction

 

[Jim GreetheadParticipant @jimgreethead]

You blokes are proposing some really ingenious ideas and I am enjoying the discussion. Maybe the topic has arisen before John, but it is not easy to find it on the Forum.

 

Ian: I am not sure I understand what you are saying here because the handwheel is locked to the drawbar with locknuts on each side. I will, however, check that it is not bottoming in the collet chuck. Thanks for the suggestion.

 

Nigel: I keep thinking about that extraction tool. With a collar on the spindle, the world is the molusc of your choice; it opens a range of possibilities. If the extraction tool was modified so it could turn the drawbar, you could do away with the extraction bolt, unscrew the spindle until the extraction tool contacted the bottom of the collar and keep turning to press the drawbar out. It would require a lever on the extraction tool but then the tool could be used to tighten the drawbar as well.

 

Does anyone know how those automatic drawbar insertion and release mechanisms work? They sound like those air hammers used to tighten wheel nuts.

 

Jim

 

[Jim GreetheadParticipant @jimgreethead]

I just found this site: http://www.cnccookbook.com/CCMillDrawbar.html

 

The plot thickens

 

Jim

[JonParticipant @jon]

Just get yourself an air powered butterfly ratchet and socket 3/8 will do.

 

You are quite right Jim every mill around the quill passes through the bearings like it or not.

Had similar happen time and time again i do tighten the drawbar up as much as i can. Some times with boring head have found its dropped and for it to do that must have loosened off. Bear in mind it was grollied up tight! Not wimpy hand tight asking for trouble.

For those that infer stressing V’s etc by hammering the head i would suggest you have a close look at the forces involved when actually doing something, think you will be surprised how minimal knocking the drawbar loose is comparitively.

What i have found is a short sharp tap with 1/2Lb hammer does the trick 9 times out of 10 left in coolant tray. 17mm spanners left permanently in the T slot trough collection, new collet, drill chuck or tool replaced within 30 to 45 secs and do such things 12 times daily.

 

First thing i did on a new mill was make a spindle lock going in to the protruding splines.

 

Very easy to make up draw bars i have to replace twice a year on every day machine plus old one with three different threads. Locktite no chance not even silver solder or brazing will hold, V out and weld.

Its also common practice in engineering to use a whacking instrument be it spanner or hammer.

[BERTOParticipant @berto]

Just had a look at my mill and the collar idea went out the window as the spline dissapears down inside the head when at full spindle depth and to keep it above would mean the loss of 60% of the travel.

While i was playing and fiddling around changeing tools i noticed a screw in cover for the bottom bearing on the spindle and as it was loose i took it off.

I had a look up in there with a torch and found that the bearing was a taper type similar to what’s used on hub bearings on a car and to my relief covered in moly grease !

I began to think of how a wheel bearing would suffer axial and radial shock loading because of potholes and corrogations in the road and maybe the designers had used this type bearing in a Mill as it can take some punishment or at least more than a ball type bearing .

Thoughts ?

 

Jim,

On the video it looked like the rod and hand wheel were not locked together and if they were inerteia and leverage or lack of it are your culprits .

What about making a new hammer that has one face of copper, brass or lead and the other end of the head a socket to undo the drawbar and the handle is used like a ” tee” bar – 2 tools in one !

 

Ian

 

 

 

 

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Does anyone know how those automatic drawbar insertion and release mechanisms work? They sound like those air hammers used to tighten wheel nuts.

 

Alan , Jim look in my photo album for ‘ Powered drawbar ‘.

 

The system shown is the one normally fitted on production machinery and especially automatic toolchangers on CNC milling machines .

 

There is another much simpler type which just uses an air motor to spin a captive nut .

[Jim GreetheadParticipant @jimgreethead]

Hi Ian,

 

Your “spanner/hammer” might be the go, at least until I get sufficiently enthusiastic and build one based on an air hammer.

 

Pity about the little handwheel though. One side effect was that running the drawbar up and down was done with a flick of the handwheel instead of that tedious thumb & forefinger work (lazy? Too right I am). There wasn’t much flywheel but it seems that the bit that worked here was the bit that loosened the drawbar.

 

I am still puzzled about the drawbar coming loose. As someone pointed out, the cutter load will tend to tighten the drawbar. The only thing I can think of is that I was using a profiling cutter which makes heavier interrupted cuts than an end mill. I think that the start of each cut slowed the motor just a bit (and tightened the drawbar) but then the motor accelerates again which tends to loosen the drawbar. I think the loosening effect is greater than the tightening effect.

 

Michael: Thanks for the photo. I think the air hammer one is the one I was thinking about.

 

And I am still thinking.

 

Merry Xmas to all of you and thanks again for the stimulating discussion.

 

Jim

 

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

In case it is not obvious the claw grip power drawbar is operated by a big air or hydraulic cylinder sitting above it .

 

As regards drawbar coming loose and then tightening again make sure by a test that this was not just a case of quill bounce and that the drawbar was actually ok .

 

Quill bounce is a really serious problem on cheaper milling machines .

 

 

 

 

[JonParticipant @jon]

The cutter vertical load is imparting more pressure than force tightened and in turn reduce the grab on the spindle, in effect loosening.

Much like the impact wrench mentioned and same as using MT drills with tangs ie cannot revolve but can drop out the spindle if chattering – same thing.

Now try this, just tension up the drawbar finger tight and take a menial cut with a cutter in on something, if cutter dont drop you can hear the drawbar working loose.

For the MT to tighten it would have to revolve in the spindle MT and the drawbar to remain unmoved.

 

The cure is to tighten the drawbar past the point where upward forces are not exceeded, problem solved.

 

Must get round to fitting the butterfly air impact wrench some day, got all the stuff needed inc regulator, tubing etc.

[Jim GreetheadParticipant @jimgreethead]

Jon: I am pleased to know that I am not the only one with small piles of all the necessary bits for things just waiting for me to decide that they are the next project. They usually wait until the current project has disheartened me or everything else looks too hard. Sometimes the piles get raided for things needed elsewhere of course.

 

Michael: What is “quill bounce”? When I googled it, I got a video of several children jumping on a trampoline plus a number of other suggestions that didn’t look too much like a milling machine problem.

 

I am now back home after the usual Ho Ho Ho run to see family in Sydney so I can give some thought to Ian’s “spanner/hammer”.

 

Thanks to all for the continued interest

 

Jim

 

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Jim ,

 

Quill bounce or quill drop as some peole call it is an effect well known to machine designers and some machine users .

 

In milling machines with a quill type spindle operated by a rack and pinion and pulled up by a return spring there is always some element of freedom for the quill to move up and down in an uncontrolled manner when apparently set to some specified position . This freedom comes mostly from the clearance between rack and pinion teeth and between teeth of worm and wheel if fine feed is in use . In quality machines there is not much problem but in worn out machines and poorly built machines this movement can be up to a couple of millimeters .

 

Under light cutting conditions nothing usually happens but under heavier cuts especially when doing things like milling on the side edges of a spiral flute milling cutter the quill and cutter can be snatched down to the extent of all clearances in the system . This effect may be stable and the cutter stays down (more common) or the whole thing can go into a state of flutter (less common) and that is why the effect is called quill bounce .

 

I have seen very marked examples of this happening but usually it happens to a more subtle degree – a small amount of drop or flutter not that obvious to sight shows up as poor dimensional control of cut and poor and uneven surface finish .

 

Locking the quill vertically obviously improves matters but don’t be deluded that it stops the problems altogether . Once again few problems on good machines and many more problems on tat .

 

Just for interest there are other things going on in quill type milling machines – orbital precession being the best known and worst – see if you can work out or guess what this is for a bit of mental exercise .

 

MW

 

[Jim GreetheadParticipant @jimgreethead]

Thanks for the explanation of “quill bounce” Michael, I have not previously heard it called that (or anything really) but I always lock every axis that I am not cutting along. Interested to learn that locking the quill does not cure the problem.

 

I guess these small things add up to make the difference between the surface finish I get on the HM45 and the one I got on the HAAS CNC machine in the course I did at Tech this year.

 

Now “orbital precession”: could it be the axis of rotation of the quill wobbling like the axis of rotation of a spinning top? And if so, what order of magnitude of error does this cause?

 

Thanks for the continued interest and for exercising both remaining neurones.

 

Jim

 

[JonParticipant @jon]

Quite right Michael, the bearing is in the quill and heads, any minute play even if Timken would induce vertical and lateral movement even though quill locked up. Minimal though.

Far greater movement is often experienced with poor build machines, you can visually see a Wabeco mill bounce and deflect on the upright column yet alone the head.

 

Right Jim pretty much same machine as mine, the geared head is very heavy hanging off a dovetail. Lock it up, put a cut on and you will see vibration/deflection originating from this joint, i grolly mine up and still see it. No visual or felt vibration or movement on upright dovetal column.

Another area due to the build is the quill in the casting fit, it will wear quick.

Precession then would cut oversize right angles to the torque.

 

Another for Michael and Jim is when tension is on the quill winding upwards, zero DRO and take a cut.

Now try winding down to zero with tension on, it will be something else.

If no play should come out the same. I dont get this off the spare RF25.

New decent quality bearings if anything too tight.

 

Found coolant pump today Jim, had it 7 years.

The CNC was probably better built and running a lot faster, the downside of the ZX40/45 series.

I am after the transfer box bolted to upright column between the elevation motor if you convert it.

 

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