Coring on DVR XP

Just bought the Oneway coring system and tried it out by coring a 15 1/2" maple bowl blank, which I admit might be asking too much of the lathe. Got a couple of cores out of it but it took some time and the headstock got quite hot. .. probably too hot.

Cored at a slow speed (275 RPM) and took my time but the headstock got quite hot, ... probably too hot.

Would like the cores but don't want to damage the lathe. Am I missing some techniques, or am I just asking too much from a lathe of this size?
Thanks for your help,
Trevor

Probably better to core at 500 plus rpm. That is pretty slow. Also make sure the bit is sharp. You should not be getting that much heat from your motor. Is your DVR the 110 volt model, or the 220 volt model. I have turned on the 110 volt model, and think it should handle coring without too much trouble. I have been surprised at how much torque that little motor can put out. Maybe to check sharpness, you should see if the shavings are really hot. I don't have any read out on my lathe, never had actually, and would think I core with my McNaughton mostly in the 800 to 1000 rpm range.

For first coring attempts, I suggest some thing smaller, no matter which coring system you use. Just to get the hang of it first.

robo hippy

Thanks Reed,
yes its 110V. I'll try some smaller cylinders and spin them faster before going back to the large blanks.
appreciate your help,
Trevor

I core on a larger lathe but the sharpening will be the same. Depending on the wood, I can get 3 or four cores from the #1 knife. The #2 knife seems to need sharpening every two cores and the #3 knife will dull the blade every core. The sharpening doesn't require much metal removal, merely a fresh edge. Dull blades just won't work and will cause you to beat up the lathe.
faust

I have the NOVA DVR XP and the McNaughton system. I have used this to core cherry, soft maple and walnut so far.

I read a lot about the recommended speed being 800+ rpm.

I have not tried going much over 500 rpm so far.

if you run the lathe < 500 rpm, the Tekantool manual recommends changing the Program setting from "NORMAL" to "HARD". Pg 18 of the manual. This is recommended for heavy and/or out-of-balance work at speeds < 500 rpm.

I would run at a higher speed than 250 rpm if you are comfortable and the vibration is not too much. I recently cored a walnut log which had a mix of sap and heart wood. Despite it looking round, the density differences created a lot of vibration. I think I did not get over 400 rpm.

As the others stated keep the knives sharp. My McNaughton was purchased used. I think the curves on my knives may be flat in spots. I get a lot of rubbing on the side edges of the knives. I have to open up the cutting slot to minimize this.

If you have 220V available, you could change to this voltage. Just needs a plug and switch change. The controller board auto-detects the voltage. Gives an extra 1/4HP. This may help you heat problems a little.

I have the DVR XP. I core at about 450 to 650 and have it set to hard. Haven't had a problem coring 15" blanks. Keeping your knives sharp it key. If you didn't sharpen them when you got it you probably should have. Like Faust said you have to sharpen those knives such as the #3 after 1 or no more than two cores. #2 I can get 3 cores and #1 I can get 4 cores but no more than that for each one.

My friend, who got me hooked into this vortex, turns on a DVR and has cored hundreds of bowls with a Oneway system. He says to keep the tools sharp and frequently clear the shavings from the bowl blank. Let the tool do the work and don't force it. I have never seen him work it hard enough to heat the head it stock. If it starts cutting hard, he removes the tool and blows out the shavings. I have used his lathe and tool to core several blanks. I could force it hard enough to slow and almost stall the lathe. I had no problem after he showed me to not force the tool and to let it do the work.

The trick with the DVR and somthing that Nova will not tell you is if you run your lathe at 600 to 650 RPM it will develope the most HP and has the best cooling. I always do all my coring at that speed and yes the shrper the better.

George

The newer Mark 8 McNaughton blades have a pretty good curve to them. Some of the older ones did not. The blades always drift to the outside as you cut. My reasoning is that the last 1 inch of the tip goes straight rather than following the curve of the blade, so the blade follows the tip and not the curve of the blade. No problem on a shallow/small core, but a bit of a problem on a larger core. I have bent the tips in just a hair on a few, and that straightens up the cut a lot. If you can get one of the plastic circle templates, lay your blades out on them and see how good or bad they are. John Lucas had an article in the last Woodturning Design magazine on different bending jigs. Kel McNaughton does not agree with my reasoning. The last time I talked to Mike Mahoney, he said, "hmm, you might have some thing there". The wood variety depends a lot on how often I sharpen. With Madrone (nearest wood I can think of cutting wise is pear) I can easily get several bowl cores with one sharpening. With Walnut or Oregon Myrtle, I can get one. Same with locust.

robo hippy

Just want to thank everyone for their input. I cored 3 x 15.5 " bowl blanks today and each one was easier than the one before. Amazing what a faster RPM, a fresh edge on the knife, and the proper torque setting will resolve.
Thanks again!
Trevor