# Lathe Taper Attachment - Hercus AR 9"



## Hawkeye (Apr 26, 2012)

This project starts with an old magazine article to be found at: http://www.kinzers.com/don/MachineTools/lathe_projects/taper_attachment/taper4.jpg and other places. It was already posted by Scrapmetal in the General section. Since it was designed for an SB9, it is a perfect fit for the Hercus. Most of the details are as shown in the plans, with a few revisions, which will be pointed out.

I started out by buying a cast iron counter weight at the scrappers to use for the two slides. When I cut off a piece to make my surface gauge, I dulled the 10' blade on my big bandsaw. Always go with your slowest speed on unknown cast. Now I'm afraid to try the new blade on it. The alternative was to choose a different material for the slides. I settled on High Molecular Weight Polyethylene (HMWPE).




The bottom bracket is bolted to a heavy plate attached to the back of the carriage. I milled a notch into both to allow the cross-slide to be removed when necessary without removing the taper attachment or the X-axis DRO.



I used 3/8" plate for the cross-slide connector rather than the suggested 1/8" or 1/4" stock because I wanted it to be as stiff as possible. Any flexing would allow the upper slider to rock, changing the distance from the taper bar. A bit of undercutting at the shoulders allows the cross-slide to move all the way forward when the attachment is not in use.





A bit of milling was necessary to make the underside of the cross-slide parallel to the Y-axis of the carriage.



The V-way clamp was milled from a piece of 1"x2"x4" HRS and angled down toward the position of the lower track.



The plans call for curved slots in both the carrier and the table. I opted for three tapped holes in the table to allow the same range of movement.



The 'complete' attachment - still needs some cosmetic work, plus the degree and taper-per-foot markings.




I haven't tried turning any tapers yet. Watching the DRO displays while moving the carriage shows that it takes about an inch of movement to take up the slack before the Y-axis display starts to advance. I may have to rethink the HMWPE sliders. It's relatively easy to replace parts once the whole attachment is done.


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## Tom Griffin (Apr 26, 2012)

Looking good Mike and thanks for posting the build. 

Maybe bronze instead of the poly would work out better. You are probably getting some compression of the plastic, causing the lag.

Tom


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## Tony Wells (Apr 26, 2012)

Just about every taper attachment I have used, including brand new ones, had some slack that caused lag like that. Usually in the crossfeed screw thrust setup. I just got used to it. Yours may be partly caused by the plastic, as Tom said....so that would be as good as any place to start investigating.


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## Hawkeye (Apr 28, 2012)

*Re: Lathe Taper Attachment - Hercus AR 9" - First Taper*

In between phone calls today, I managed to throw a chunk of scrap aluminum in the chuck and try out the attachment. I was aiming for an MT2 just to have an actual goal. That standard has a taper of 0.59941"/ft, so I fiddled with it until I got 0.150 on the Y-axis DRO for an X-axis reading of 6.000. That's after hitting the Zero buttons on both just after the Y started to advance (slack taken up).

I used a carbide insert cutter because that happened to be in the holder, so the finish isn't quite what it could be. I figured that the taper attachment should be pulling against the cutter, so I set up to cut from the chuck outward. That gives some added insights to the process. After you start the cut, the X-axis DRO reads around 0.89" when the Y starts to advance, so the first 7/8" out from the chuck is actually parallel, then it starts to taper.



After I got the small end down to around 0.572" (MT2 standard), I did a facing cut to check the cutter height. No nub, so it was right on.



The 'finished' taper. If you look close and use your imagination, you can see where the parallel ends and the taper begins. I couldn't extend the tailstock spindle far enough to test the taper, so I locked the tailstock quill and slid the tail off the bed. My turned-down section on the test piece wasn't long enough to allow the taper to go all the way into the tailstock. I'll have to turn the shoulder back another 1/4" to test it. That means removing and re-chucking the piece, so repeatability will be an issue.




It just seems worth testing before I re-make the sliders, just to compare HMWPE to bronze, aluminum or whatever. If the take-up distance stays the same, it will show that plastic can be a viable substitute. If not, we'll know how much flex it allows.


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## 12bolts (Apr 28, 2012)

Mike,
Nice job on the build there.
I will be keeping an eye on this and interested to hear how you go with final tweaking.

Cheers Phil


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## Hawkeye (Apr 28, 2012)

I turned down the shoulder and test-fitted the taper into the tailstock. I can feel a tiny bit of movement toward the small end. If I give it a smart snap into the tailstock, it tightens right up and needs to have the quill retracted to release it. It is aluminum, after all. It's close enough that a bit of careful emery use (go ahead and cringe) at the thick end would make it usable, if it were made from steel at the same setting.

One advantage of this test was to demonstrate that the use of DROs to set the taper attachment is valid. It does, however, take a bit of fiddling to get it right. Having the scales on the ends of the top carrier will give a quicker starting point. The addition of adjustment screws (to rotate the carrier - similar to tailstock offset screws) might make it easier as well.


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