Turning an MT2 taper in my lathe

[Brian Rupnow]

I am messing about with the idea of making an adapter to use my 3 jaw lathe chuck on my rotary table. Yes, I know that there are a number of posts covering this, but I am interested in an adapter to center my chuck on the rotary table. My chuck has 3 tapped holes at 120 degrees in the back side to attach it to a flange on the quill in my lathe, and a locating register to center it. My rotary table has 3 T-slots in it at 120 degrees and an MT2 tapered hole in the center. Anyways, while kicking this idea around, I went on line and found that the total angle of taper on an MT2 is 2.8613 degrees. (there are a bunch more decimal places, but I can't work to that accuracy anyways.) The dials on the topslide (compound rest) on my lathe only register in one degree increments. How would I go about either turning a peice with an MT2 taper, or boring a hole with an MT2 taper.---or is it not possible? How could I ever achieve the accuracy to do this, or is that beyond what my lathe is capable of?

 

[mklotz]

It's far easier to buy an MT2 taper in the form of an endmill holder or the end of an MT drill and then attach said taper to whatever mounting plate is needed for your chuck.

However, to answer your question (and provide a bit of instruction for future readers of this thread), here's at least one method to set your compound to a precise angle.

Mount a known cylindrical bar in the 4jaw and use a DI to get it running truly. Fit a DI to your compound taking great care to ensure that the centerline of the DI tip is at the same height as the lathe centerline.

Calculate the sine of the desired angle. Call this value "S". Rotate the compound to the desired angle as best you can using the existing protractor dial. Now, touch the DI to the bar and zero it. Traverse the compound for one inch. If you've set the angle perfectly (highly unlikely), the DI will now read "S". If it doesn't, tweak the compound angle* setting and try again. Repeat until you get the results you desire or your patience expires.

If you need to do this process often, it's arguably faster to set up a fence parallel to the compound slideways and use a sine bar against the bar held in the chuck but I don't have the patience to describe that now because I haven't had my coffee yet.

--------
* Tweaking is best done by snugging one of the compound bolts down to provide drag and then tapping with a soft-faced dead-blow hammer.

 

[GailInNM]

Marv is right that it is easiest to buy or scrounge a taper and then modify it. There are adapters available that have a hardened taper shank and a soft head that are designed to be machined. The imports are moderate cost.

However, I think everyone should turn a taper or two so they know how to do so when a commercial taper is not available. There are several methods of setting the compound and Marv's is a good one and probably the most popular method.

Note that using Marv's method that the angle used for calculation is the angle for one side of the taper and that the angle you mentioned is the included angle. So you have to take the sine of one half of that angle for your setup.

Tapers are not very forgiving of errors, so the dial indicator will need to read to 0.0001 to get the angle close enough to work well.

A MT taper is nice to practice on because the taper is 0.0500 inch per inch, close enough to what we can normally work to any way. This is the included taper, so the dial indicator is will move 0.0250 for a 1 inch travel of the compound.

When you turn the compound lead screw, don't crank it with the handle as you will be taking up the play in the gibs in opposite directions causing the taper to have grooves in it. Be sure to check the gibs setting on the compound. If you notice any bobbles in the DI while feeding the leadscrew, the gibs are probably too loose. Lock the cross slide while cutting the taper.

Gail in NM,USA

 

[GailInNM]

Brian,
Note: I had an error in my previous post and have corrected it.
Marv, I am on my second pot of coffee and am still screwed up. We will both get better as the day wears on.
Gail in NM,USA

 

[Brian Rupnow]

Gail that sounds like me---"A hard shank and a soft head"----No, wait---That sounds like me 40 years ago!!! And where do I go to buy such a thing???

 

[Stan]

Brian: Check out BusyBee pt # B460 and B461. I have used lots of these and they sure beat turning MT on a small lathe without a taper attachment and tool post grinder.

You can adapt them to anything by threading or welding to whatever you need. To be able to eject them from the tailstock, you have to grind the corners of a capscrew to plug the drawbar end.
HTH Stan

edit: These are in the sale flyer frequently.

 

[Cedge]

Hmmmm. Probably not industry approved, but I've cut several short MT2 tapers using the compound. Not knowing any better, I put a known 1/2 rod in my MT2 drill chuck and mounted the rod in my 3 jaw chuck. I then set the angle to match the taper by moving the cross slide against the taper with the cross slide just snug enough to allow friction movement. Note that you might need to use a parallel bar to do this.

I then cut the taper angle with the compound. Dunno about perfection, but after 2 years, I'm still using the ones I've turned without any problems. They grip and eject just fine and are nicely concentric.

Steve
Who still believes a bumblebee can fly

 

[tel]

I've made quite a few of 'em - here's how.

Put a bit of something in the three jaw - face it and drill a centre hole. Put a centre in the tailstock. Capture another centre between the two. Now with an indicator mounted in the toolpost, twiddle the top slide until you are tracking right along the taper with no deflection. Lock down the top slide - proceed with job.

It really is that easy.

 

[mklotz]

Steve
Who still believes a bumblebee can fly

It can!

The original study (done at my alma mater if memory serves) was to prove that, aerodynamically, a bumblebee can't GLIDE. It did and they can't but the jounalism major who picked this up was too dumb to know the difference between powered flight and gliding.

Now you know why I don't read newspapers or watch TV news.

 

[Divided He ad]

Now this one will I have no doubt be read and have heads shaking.... But here goes...


I have made several MT2's for varying things like mt peck drill and my small die holders and I made them all by holding a large cutter with a MT2 shank in my chuck, taper sticking out. Then set my tooling angle to follow the exact edge of that taper.... Admittedly it took a while but like Steve's mine are still working well, and I have not found any reason to replace them with commercial ones.


I await the slapped wrist!!




Ralph.

 

[Brian Rupnow]

If you aren't sure what you need to do then buy a few from Busy Bee. The price is $10 and for that it isn't worth the time to make. They are good to deal with, I buy from them frequently. here is a link to the item.

http://busybeetools.ca/cgi-bin/picture10?&NETID=1316380902082011389&NTITEM=B460

Don't want to say anything about "Idiots" and 'Morons", but I just got back from BusyBee on the other side of town and they swore that they have never heard of such a thing, and that they certainly don't sell such a thing!!! I just phoned them back and gave them the part number---"Oh Yeah, We've got 2 of those---We didn't know what they were." (And the darn things are only $9.60 each!!!!)

 

[tel]

Mount a known cylindrical bar in the 4jaw and use a DI to get it running truly. Fit a DI to your compound taking great care to ensure that the centerline of the DI tip is at the same height as the lathe centerline.

You can get around that rather twiddly operation with something along these lines - I made a variation of it with the tongue about 3/8" wide that just clamps to the topslide with the tool clamp

http://www.frets.com/FRETSPages/Machining/Tooling/IndicatorHolder/indicatorholder.html

 

[Stan]

Brian: I don't care how many boards you copy your post to, but please keep Evan of this board.

 

[Brian Rupnow]

Sorry Stan--I had no awareness of my wrongness--- ;D ;D