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Duplicating turned legs without a duplicator

#185829 by tdubnik » Fri Mar 20, 2015 7:39 am

If you read my post on the coffee table build http://www.shopsmith.com/ss_forum/viewtopic.php?f=5&t=16122 you know that I had to turn multiple legs and struggled a little to do so. All the while I was thinking how much easier this task would be if only I had the lathe duplicator. Even though Shopsmith put it on sale recently the price is just not in my budget at the moment.

OK, i can't buy one so what are my other options. I started watching YouTube videos on homemade lathe duplicators. It seems that most of the ones I found either used a router or angle grinder to do the cutting. I kept asking myself why do they need a powered cutter when the lathe can provide the power and all I need to do is apply a cutting tip.

I had a couple of Easy Woodtools cutters for lathe tools I made for myself and figured I could use them to do the turning. All I need to do is determine how to mount and present the cutters to the workpiece and let the Shopsmith do the work.

This is what I came up with. This project may be presented over a couple of posts because there several pictures and explanations involved.

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The first thing I did was to fabricate tool holders. Since I had the round and diamond cutters I made holders for them. I used 1/2" square stock and drilled and tapped holes to hold the cutters. I then used my grinder to profile the holders to match the cutter profiles and provided a relief angle under the cutter to clear the workpiece.

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Next I needed to make a follower to follow a template. I cut a piece of hardwood stock 1" wide (arbitrary on my part) and shaped it to match the cutter.

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Now I have a cutter and follower but I have to make a way to hold the tool and present it to the workpiece. I started with a plywood base that seemed to be about the right size. I then cut a piece of white oak I had laying around for the upright. I started by cutting it long because I wasn't sure what the final height should be yet. I routed a 1/2" x 1/2" groove through the top that fit my tool holder exactly. I cut a piece of scrap plywood to cover the top and added a threaded insert and know to hold the cutter in place. I cut a 1" mortice in the bottom of the upright to hold the back end of the follower and keep it centered. I then drilled a hold through the follower and plywood base, added a threaded insert into the plywood base to hold the front of the follower.

By this time I had already build the platform to fit the Shopsmith so I could set the final height and do the final assembly of the cutting head? (don't know exactly what to call it).

edit: I forgot to mention that I made the plywood base extend slightly beyond the cutter tip so the forces would transfer down to the table and not risk tipping. I also added the triangular blocks and attached the handles I had left over from a Porter Cable router base that I wasn't using.

To be continued in part 2.

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Re: Duplicating turned legs without a duplicator

#185832 by claimdude » Fri Mar 20, 2015 8:37 am

Nice work! Keeps us posted on your progress and your trial run.

Jack

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Now I need a platform for my cutting head to ride on. right now I am planning to make some legs for a farm table so I need to be able to handle a 29" spindle. I had some melamine plywood I bought at Rockler a few years ago just waiting for the right project. Just have to figure out how to mount it to the Shopsmith and then how to attach a template.

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I notched some 1 1/2" stock to tightly fit the way tubes and made the notches deep enough so the top would rest slightly above the table carriage. When using this jig the table carriage does not come into play. I drilled a through hole and countersink so I could insert some T-bolts through the rails to be used for the clamp. I cut the clamping bars to match the rails and drilled a through hole for the bolt to stick through. Now a couple of knobs and i have a platform.

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The next thing I did was build a template and a template holder. The holder is nothing more than a strip of wood slightly thicker than the plywood I used to build the cutting head base. It has to be a little thicker so the edge of the cutting head can slip under the template but the follower contacts the template. I drilled a few holes and slipped some template attachment bolts through and then attached it to the platform. I made sure the leading edge of the template holder was directly in line with the centerline of the part to be turned. To me this made the alignment and set-up easier.

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Here you can see that I cut out a template that I designed in Sketch-Up and matches the legs I want to turn. I attached it to the template holder with the center line of the leg lined up with the leading edge of the template holder. This insures that the leg will be the correct size and I don't have to take any offsets into account.

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Now with everything set up its time to put in a blank and check things out. The blank is 3 1/2" square by 29" long. I lined up the end of the template with the end of the blank as this is going to be an exact length turning. I double checked to make sure the cutting edge is on dead center (as that is what Easy Tools specify). You may have noticed that I modified the template by adding a block to the portion of the leg that will remain square. When I made my template I didn't take into account that the diagonal is wider than the square (in other words; If I followed the template I would have rounded over the portion of the leg that needs to remain square).

End of part 2

Part 3 will show initial cuts and surface finish.

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Re: Duplicating turned legs without a duplicator

#185840 by drl » Fri Mar 20, 2015 11:28 am

I'm really interested in this "tool". Looking very nice and well designed. Looking forward to your next post.
Regards,
Dwight

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Re: Duplicating turned legs without a duplicator

#185850 by rcplaneguy » Fri Mar 20, 2015 1:29 pm

Good job! Look forward to seeing how well it works. I guess the SS version has the template on top to avoid all the chips.

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Re: Duplicating turned legs without a duplicator

#185854 by beeg » Fri Mar 20, 2015 2:58 pm

Here's another idea, from Chuck.

viewtopic.php?f=5&t=5819&hilit=lathe+dancers

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SS 500(09/1980), DC3300, jointer, bandsaw, belt sander, Strip Sander, drum sanders,molder, dado, biscuit joiner, universal lathe tool rest, Oneway talon chuck, router bits & chucks and a De Walt 735 planer,a #5,#6, block planes. ALL in a 100 square foot shop.
.
.

Bob

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Re: Duplicating turned legs without a duplicator

#185865 by charlese » Fri Mar 20, 2015 8:00 pm

Thanks, Bob! Now I don't have to post the old thread.

I think td's solution is a great way to repeat turnings. Reminds me of the one made by mbcabinetmaker(sp).

---

Octogenarian's have an earned right to be a curmudgeon.
Chuck in Lancaster, CA

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OK, everything is now fabricated, aligned, and set up. The blank is mounted so I guess its time to take a test drive.

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I started the roughing using the round cutter and despite my apprehension things went well. The chips started flying. The cutter was cutting with no chatter and it was very easy to control. No grabbing or pushing of the cutter head. I could have easily have controlled it with one hand.

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Now I am starting to form the leg profile still using the round cutter for initial shaping. Lots of chips so I have to stop occasionally and break out the DC3300.

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The leg continues to develop and I am following the template to shape the leg.

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Time to switch to the diamond detail cutter to clean up all of those tight places that the round cutter doesn't fit.

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The finish is rougher than I would have liked but the duplicator seemed to work fine. When making the final pass I did have to stop and clean up the chips so the follower could follow the template.

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The final product after some sanding turned out very nice. I had to cut the transition from square to round with a skew chisel as the carbide cutters had too much chip out on the corners to be acceptable. I also cleaned up the small flats with a parting tool to get the sharp corners but everything else was done with the cutters. Overall I am very pleased with how this project turned out and how well it worked.

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In the end I am pleased with the results of this project. I accomplished what I set out to do and the end results are more than acceptable. I haven't a clue how this compares with the Shopsmith duplicator but I managed to put the whole thing together with no out of pocket expense which is important to me right now.

I know there are some obvious shortcomings with my design. The first thing is that the template is attached to the platform which limits the size of the turning to the size of the platform and the quill extension of the Shopsmith. To make a shorter turning I will have to build a shorter platform.

The next thing is that chips can get piled up between the template and the follower. For the rough cuts it doesn't matter too much but for the final cuts I had to clean off the platform to insure the follower could actually touch the template. This is actually not all bad as it let me take very small bites on the final passes and helped to get the best finish possible.

In my design it will also be difficult to copy an existing turning as I didn't provide a way to change the height of the follower or mount an existing spindle.

I'm sure I could re-design some parts and figure a way to mount the template not dependent on the platform. If I did that I could build a smaller platform that slides back and forth or mounts to the Shopsmith carriage.

Oh well .... That may be a project for another day. :)

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Re: Duplicating turned legs without a duplicator

#185884 by algale » Sat Mar 21, 2015 7:19 am

Before I bought my lathe duplicator, I thought about making my own and sketched one out (based on a design I saw on the web) which is very similar to yours. But I didn't already have the carbide cutters and abandoned the idea when a used one came up near me at a price I just couldn't refuse.

Personally, I think yours appears to work about as well as the Shopsmith version for flat templates. But if you continue to be dissatisfied with the finish quality off the blade, you might experiment with trying to vary the cutter height. A tip from the Shopsmith lathe duplicator manual suggests if the turning is coming off rough or with tear out, the cutter may be a fraction too high relative to the center line of the turning. So think about whether you can make adjustments to the height of your cutter or the table it rides on. Another tip in the manual was to keep the cutter tip a 32nd to a 64th back from the follower tip to allow the sanding process to take you to your final dimension.

Congrats on a job well done.

---

Gale's Law: The bigger the woodworking project, the less the mistakes show in any photo taken far enough away to show the entire project!

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