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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:
--- Quote from: John Hill on September 16, 2010, 02:27:20 AM ---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.
--- End quote ---
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.
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