simple taper attachment

[jcs0001]

Hello:

I plan to build a simple, detachable taper attachment for my lathe (King 10 x 22 - the same as the Grizzly 0602).  The lathe has a MT4 spindle and it isn't easy to obtain machinable tapered blanks for that size.  I have just ordered an MT4 to MT2 adapter and a machinable MT2 taper however would like to avoid this in future if possible.  This combination is limited because it does not allow for a draw bar from the back of the spindle.   

The taper attachment will not be used in a production environment but I do wish to make an attachment that works well and is a worthy addition to my other equipment.  Due to a lack of room behind the lathe I need to keep it compact and likely remove it when not in use.  I anticipate taking the backsplash tin off when using the attachment.

One style of taper attachment I have seen is the one on GadgetBuilder's site (http://www.gadgetbuilder.com/Taper.html). 

It also appears that Logan made a simple one as shown below.



I am considering building something along these lines using a piece of 1/2 inch drill rod (or 5/8 in. depending upon what I can locate easily) for the sine bar, along with a matching linear bearing.  The bearing would slide along the sine bar and attach to the piece that guides the cross slide.  A quick search of ebay reveals lots of different linear bearings at a reasonable cost so I don't anticipate a problem obtaining a suitable candidate.

The other options are to bore an accurate hole in a steel block that will slide along the sine bar and or install a matching bronze bushing (or make one) that would ride on the sine bar.

I have seen the beautiful work done building a full fledged taper attachment (Rob.Wilson's) however I don't have the equipment (welder, big mill) or the ability to do something this complex.  Perhaps a few years!!

Any feedback on the above ideas or any better ideas would be appreciated.

Thanks,

John.

[Lew_Merrick_PE]

John,

A standard "hard" MT4 center is easily turned into a "machinable" one with the application of heat.  A charcoal barbecue will work so long as you have a blower for it (and a handheld hair dryer can be made to work as a blower).  Heat it up until a magnet won't stick to it, cover it in ashes, and let the whole thing cool down to room temperature.  A quick wash in acid (vinegar and salt works well -- it just takes longer), a vigorous wire brushing, and voila -- a machinable MT insert!

I would argue for a rectangular cross-section (or base) for you taper bar.  Making a rectangular u-shaped bushing is not that hard and your stiffness is proportional to the cube of the dimension parallel to your bed.  Tool steel blanks are fairly nicely ground and, with care, should last a lifetime or two.  Regular bronze or brass should work nicely for the rectangular u-shaped bushing, but I would recommend an aluminum-bronze for the pivot bushing between that support and your cross-slide.  It will take much more load, wear longer, and give good results using a hardened dowel pin as the pivot.

Does that help?

[John Hill]

John

I am sure your taper attachment will be a very satisfying project and addition to your shop.  Meanwhile, I will tell you how I cut Morse tapers on my lathe.

The first thing I do is find a dead centre which has a central divot on the small end of the taper.  Then I put a piece of scrap in the chuck and centre drill it to take a centre.  Next I put another dead centre in the tailstock and mount the first centre between the tail stock and the divot in the piece in the chuck. 

The object of doing this is to set the compound exactly to the required taper angle and we do that by setting the side of the compound exactly parallel to the taper of the mounted centre.  A DTI is the best way to do this if you have one.

Once the compound is locked at that angle it is a piece of cake to turn a taper with considerable accuracy.

John

[fluxcored]

John

The first thing I do is find a dead centre which has a central divot on the small end of the taper.  Then I put a piece of scrap in the chuck and centre drill it to take a centre.  Next I put another dead centre in the tailstock and mount the first centre between the tail stock and the divot in the piece in the chuck. 

Cool! I can do that! Been wanting to cut MT2 tapers for some time but feared my accuracy is not up to scratch. Good reason for me to get a DTI.

Thx.

[jcs0001]

Gentlemen:

Thanks for the replies.

Lew - I have hardened and tempered small cutters made from drill rod but had not given consideration to annealing a big chunk of steel such as a hardened MT4.  Will keep that in mind.

The rectangular cross section for the sine bar makes sense - the Logan appears to use this.  As you say, making a U shaped bushing would not be too difficult.  I had not considered what to use for the pivot and bushing so thanks for the suggestion.

John - Your description of setting up the compound for cutting a taper makes sense - do you have any tricks or ideas as to continuing such a cut when the compound travel is too short.  In most cases a shortened taper would likely work for me but it would be nice to have a way to fairly easily cut a full length taper for an MT4 for example.  On another lathe I had mounted a dremel as a small tool post grinder - I could do that again and use it for a final touch up to a taper I suppose.

John.

[No1_sonuk]

John - Your description of setting up the compound for cutting a taper makes sense - do you have any tricks or ideas as to continuing such a cut when the compound travel is too short.  In most cases a shortened taper would likely work for me but it would be nice to have a way to fairly easily cut a full length taper for an MT4 for example.  On another lathe I had mounted a dremel as a small tool post grinder - I could do that again and use it for a final touch up to a taper I suppose.

I'll be needing to do this soon (cut a taper longer than my compound travel).

My plan it so go as far as the compound can, move the tool away, withdraw the compound to 0, then move the carriage and cross slide so that the tool just dosen't touch the end of where I'd got to.  Take a few light cuts while adjusting the carriage/cross slide until the cuts match, then continue the rest of the taper.  In my case, my taper will have grooves cut around it, and it's not a fit-in part, so any minor diameter difference doesn't matter.  You'd just need to be more careful to line it up right.

Also, look at where your machine holds the taper.  There might be enough sticking out that you can put the "join" where it doesn't matter.

[andyf]

John - Your description of setting up the compound for cutting a taper makes sense - do you have any tricks or ideas as to continuing such a cut when the compound travel is too short.  In most cases a shortened taper would likely work for me but it would be nice to have a way to fairly easily cut a full length taper for an MT4 for example.

You might be able to stretch the compound slide travel a bit with a trick like this http://mikesworkshop.weebly.com/extended-top-slide-range.html
but a 4MT is about 4" long and such an extension might still not give enough travel.

Andy

[John Hill]

John - Your description of setting up the compound for cutting a taper makes sense - do you have any tricks or ideas as to continuing such a cut when the compound travel is too short.  In most cases a shortened taper would likely work for me but it would be nice to have a way to fairly easily cut a full length taper for an MT4 for example.  On another lathe I had mounted a dremel as a small tool post grinder - I could do that again and use it for a final touch up to a taper I suppose.

John.

John, I just make the taper as long as I can so they turn out a bit short but that hardly matters.  On my lathe a MT3 is a bit short but there is still plenty of area for the tapers to lock,  I make them full length on the small end so that the taper ejector in the tail stock works.  If the taper is to be used in the lathe spindle I drill and tap for a draw bar.

[Bogstandard]

This might give you a bit of an insight into what you are trying to achieve.

http://madmodder.net/index.php?topic=1993.0

Bogs

[John Hill]

Bogs,  I re read you page and of course learned a bit more along the way!

Also,  I have just had a brain wave!  I am going to make a double ended MT3 taper.  Then in the future it will be easy to put one end in the spindle and re-set the compound angle against the end that will be sticking out!

I suppose I could put the double ended taper in the tail stock and set the compound for cutting a female taler.   (cant imagine that being accurate enough though) 

[Bogstandard]

John,

You are making life too difficult for yourself.
After you have finished the external cut, without touching the compound angle, lift off the saddle and mount it with all the handwheels on the other side of the lathe, swing around the tool in it's holder, put the machine into reverse and then cut your internal taper.

But joking aside, it would be much easier to roughly set up the taper on your compound, then when about ²/₃'s the way thru cutting the internal taper, fine tune the compund angle to match an original taper to your bored taper using engineers blue to show you what is going on. It takes very little time doing it that way.


John

[jcs0001]

Thanks for the replies everyone.  I may still take on a taper attachment as a project but have lots to do in the meantime.  Will try to find a big enough piece of rusty steel at our local metal salvage yard for a taper or two and try the compound method.

John.

[John Hill]

But joking aside, it would be much easier to roughly set up the taper on your compound, then when about ²/₃'s the way thru cutting the internal taper, fine tune the compund angle to match an original taper to your bored taper using engineers blue to show you what is going on. It takes very little time doing it that way.


John

Thanks John,  for some odd reason I do not seem to have grasped the engineer blue technique.

 I have been wiping the non-drying type blue over my taper then putting a sleeve on, wringing it a little, then checking for rub marks.  It does work of course but it seems no better than my other method which is turn about a quarter of the length then slipping the sleeve on and  wiggling it to decide which is the biggest end and adjusting accordingly,  by the time I have got a non wiggle fit the taper is approaching the required length.

[Bogstandard]

John, mine is the tried and trusted normal method of doing it, if you get the same results, who is to say you are doing it wrong.

Cat skinning comes to mind.


John

[John Stevenson]

I have a taper turning attachment built into the lathe but I much prefer this method, it's quicker, faster, fits all lathes and allows for a steeper taper than allowed by a TTA.



To use you make a small piece with 1/2" shank ? that fits the boring head, it just needs a centre drilled hole in it. Shown fitted to the boring head.

Then you make another, any diameter just centre it AND LEAVE IN THE CHUCK. This ensures that even with a crappy 3 jaw you are dead nuts on centre. Then take your pre-centred blank and with a dob of grease fit a suitable ball bearing to each end and place between your new centres.

Drive is from the chuck via some sort of drive dog.

The idea of the balls is that there is no side loading on the centres caused be being off axis. the photo clearly shows that this job is next to impossible with a TTA because of the steep taper and the amount of thrust placed on conventional centres.

Another plus factor is that this method allows allow the boring head to be used as a boring head or even a radius turning attachment, 3 tools for the price of one.

Now the purists / flat earth society will say what about the slop in the tailstock keyway causing it to drop off centre and alter the angle.

WELL FIX THE DAMN SLOP FIRST AND STOP WHINGING.

John S.

[kwackers]

Nice one John. I'd heard about that method but never seen it so it'd dropped into the dark recesses of my brain. Now I've got visual reference I'll better remember it for next time!

Just a quick point though, you say leave the centre in the chuck once it's machined. Thinking about this, does it matter? Surely if it wasn't centre the taper would still be correct all that would be different is the hole would be off centre?

[jcs0001]

Having had a good amount of suggestions and ideas about making tapers I figured I'd show the results.

I made it to our metal salvage yard a couple of days ago and found some rusty (but good) steel round bar stock.  Not sure what it is but it isn't easy to get a really good finish on it even after removing all the rust.  The OD was just over 1.4 in. so great for my MT4 project.  The compound on my lathe will give almost 3 in. of travel if light cuts are made.

An MT4 centre was held between the chuck (point into a divot on a piece of stock held there) and a live centre in the tailstock and a DTI was used to adjust the angle of the  compound (as per earlier threads).  Once the compound was set, the bar stock was placed in the 3 jaw chuck and turned down to about 1.24 in. Diameter (the diameter of the female MT4 spindle at the large end).  Once this was done the compound was used with a carbide insert to turn it down close to the finished size.  A sharp HSS tool was used for the final cuts.

Leaving the new taper in the chuck, the chuck was removed and the fit tried using some blue artist oil paint (my only MT4 female fitting is the lathe spindle).  It seemed to be a tiny bit bigger on the large end but there was some transfer at the tail end and it locked nicely in place so I decided to leave it.  It was gone over gently with a lathe file and left.  The tail end was drilled and tapped 3/8 - 16 as that is the thread used on some other similar pieces I have.

The final test was to remove it from the chuck and install it in the spindle to clean up the portion ahead of the taper and give it a final facing.  It held nicely for some moderate cuts even without a drawbar - I didn't have one made at the time.  I realize there is some risk of having it turn in the spindle however it was nicely locked in place with just a gentle tap of the hand.  It will not come loose without being tapped firmly from the back.

A photo of a commercial MT4 dead centre along with the newly minted MT4 taper:



Photo of a newly made rest for wood turning (smaller items) along with the MT4 taper.  The front end of the taper will be drilled out for a pen turning mandrel - I'm not comfortable using a chuck to hold the mandrel as it brings my left arm quite close to the chuck jaws:



Another view of the rest showing the adjustment bolt with brass insert (to prevent galling of the inner post).  The collar at the top of the post was pressed in place (the hammer method) with a bit of locktight for extra insurance - it won't come off.  My brother was kind enough to weld the post to the plate - too bad he doesn't live closer as he has some great welding toys:



I realize that references to turning wood on my lathe will make some of you shudder however I just do not have room in my shop for other tools (although I might just find a corner for a shaper if I ever came across one).  Once suitable paint is located the rest will be covered.

Thanks again to everyone for the help regarding taper turning.

John.

[Powder Keg]

Looks good!!! Cant wait to see the pens

[Bernd]

John,

Nice job on both pieces of equipment.

Like Powder Keg said, can't wait to see some pens turned out.

Bernd

[picclock]

Hi John

Good job. Used the same method when I turned some MT2 tapers for custom tooling. HSS is a must, but lard or bacon fat lube would have improved the finish quality for me.
(Only tried it after making the tapers  ).

picclock