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Knowledge You Can Build On — Est. 1998

question and back door gloat

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question and back door gloat

#1

question and back door gloat

jared

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Hello: I have had a Delta midi lathe for 3 years, bought a supernova chuck for it and turned, due to the size limitations of the lathe, a lot of 6-8 in dia bowls. The capacity of the chuck was never an issue. Now, like a kid in a candy shop, I want to turn as big of a bowl as I can, since I got my new PM 3520 lathe up and running. I have the standard 50mm jaw set and use it in the expanding dovetail mode, since that is the way I always did it on the midi. According to the literature with the chuck, 12 inch diameter is the maximum capacity for those jaws. Is that a practical limit? It looks like I need the 100 mm jaws to turn a bigger bowl or is there some way to safely turn a larger diameter with the 50 mm jaws?

By the way, I ordered the PM3520 from Osolnik Machinery and it was a very smooth transaction. It was to be shipped on Jan 3, and it was. It arrived on the 6th as promised, in good shape with no damage just like I was told it would. It works good. I have turned 4 bowls on it and it runs smooth, has a lot of power and does not vibrate at all. I didnt ever realize when using the delta midi how much it would be vibrating, even though I had it bolted down to a heavy bench.

Now I need a bigger chain saw, riser block for the band saw, etc, etc, etc.

Thanks in advance Jared

Re: question and back door gloat

#2

Re: question and back door gloat

Mike Schwing from Md.

>12" is about the practical limit for those jaws. Any larger and I move to the 4" jaws on my supernova.

I believe you said that you use the expanding dovetail method? My experience is that a stronger hold can be achieved in the compression tenon method, and if I was going to stretch the limits of my chuck I definitely would not do it with an expanding dovetail.

You don't need a chuck to turn a big(ger) piece. Some alternatives to consider:

Turn it all in one mounting using a faceplate. Screw the faceplate into what will be the bottom and turn it all in that same orientation. Or, turn as normal - bottom first pointing towards tailstock and leave enough room for a faceplace and screws. If you center the faceplate carefully you will wind up with a very effective mounting for turning the interior. Mark the centerpoint while on the lathe, then use a compass to draw a circle the same size as your faceplate. Easy way to center the faceplate (or buy/make a faceplate center marker).

Next up - turn a tenon on the bottom, and then mount a waste block to a faceplate. Turn a recess in the block to fit the tenon, and then glue it in using a good epoxy. It will be centered, and very strong.

I'm sure there are plenty more ways to do this.

Re: question and back door gloat

#3

Re: question and back door gloat

JamieDonaldson

>Jared- I strongly suggest that you use the chuck in the compression mode by turning a tenon for the jaws to grip. Expanding a dovetail in the base is a risky process due to splitting the base, and as the size of your pieces increase so does the risk of creating projectiles! You can safely turn 12" pieces with the #2 jaws( by compression mounting), but anything larger would require the #4 jaws. Reversing the piece on a jam chuck to finish turning the base then allows any size foot you wish.

Re: question and back door gloat

#4

Re: question and back door gloat

Pete Kekel - Kentucky

>At the last symposium we had here, I watched both Mike Mahoney and Mike Lee turn "normal" sized bowls (12-14") and they both used the #4 jaws for their Oneway Stronghold chucks. After trying them out myself, I use the larger jaws for just about anything I turn, even smaller bowls if there is enough wood to make a tenon. All of the vibration and chatter are significantly lessened with the larger gripping area. The only adjustment was working on the outside shape while leaving enough wood to grip, and then being able to finish it off after it dried with the same shape I started with.

I, too, recommend the compression mode on the bowls.