Grizzly 4015 taper cut

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jeff408
Posts: 3
Joined: Mon Jan 11, 2010 4:39 am
Location: Wash state

Grizzly 4015 taper cut

Post by jeff408 »

Hi all I'm new here and just got a Grizzly 4015 3 in 1. Anyway when I turn a piece of metal or plastic it has a taper on the piece. It seems to be about .003 in about 3". The end away from the chuck is the larger end of the taper. I dont have the best platform for the lathe. It sits on a piece of 1" plywood bench which is not all that level. I have sense added a piece of 1/2 or so steel plate on top of the 1" plywood for the lathe to sit on. How much taper is acceptable? Could the lathe not being perfectly level be the cause? Any thoughts will be greatly appreciated.
Thanks, Jeff
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Harold_V
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Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Grizzly 4015 taper cut

Post by Harold_V »

jeff408 wrote: How much taper is acceptable?
Only you can answer that question. Industry standard is typically .001"/1", which is what you have, but I don't find that acceptable any more than you appear to.
Could the lathe not being perfectly level be the cause?
Not generally, but not set up in a common plane can be. You haven't said much about the size, not of the bed length, or the material. You also didn't mention if you're turning with the aid of a tailstock center. There's a lot of variables that can lead to taper, so you're going to have to provide more information in order to get a meaningful reply.
Any thoughts will be greatly appreciated.
Great! Lest start with a few things you need to know.
When you turn objects that exceed 3 times their diameter in length, taper is a given. Tool pressure pushes the material away, and it gets worse and worse as the length/diameter ratio increases. That is to be expected. To offset the problem, you can shorten the piece being machined, so little extends from the chuck or collet. If that isn't an option, you must use a center, for support.

So you'll have a little better understanding about the idea of leveling a lathe, level isn't nearly as critical as the lathe being in a common plane. If it isn't, that means the bed is likely twisted, which leads to taper.

Harold
jeff408
Posts: 3
Joined: Mon Jan 11, 2010 4:39 am
Location: Wash state

Post by jeff408 »

Hi Harold I live just down the road in Randle. I'm not sure what you mean by common plain. Swing over bed: 16-1/2 19in bed length. The last material I was turning and measuring was white plastic water pipe. I was thinking the lathe being set on the piece of 3/8in plate would help with any twist.
Jeff
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Harold_V
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Post by Harold_V »

jeff408 wrote:Hi Harold I live just down the road in Randle.
You can get to my place easily, by either highway 12, or 508, assuming they've opened it after the slide. Feel free to stop by. Send me an email or PM and I'll give you driving instructions. I'm on Burnt Ridge.
I'm not sure what you mean by common plain.
Plane, not plain. What I mean is if the lathe is sitting without twist, if it runs uphill or downhill, makes little difference. Level is used to make it possible to determine if a lathe has twist in the bed. Otherwise, it makes little difference (lubrication should be considered).
wing over bed: 16-1/2 19in bed length.
Is that a typo? 16½" swing with a 19" bed length doesn't make much sense, but the chance that you'd have twist in the bed would be quite small, assuming that was the size of the machine.

I'm going to assume you're talking about a 6½" swing, with 19" centers. A machine that small might easily have twist, reflected by the base. If you have it mounted rigidly to a strong surface, the surface will twist the bed when you bolt it down.
The last material I was turning and measuring was white plastic water pipe. I was thinking the lathe being set on the piece of 3/8in plate would help with any twist.
We'd need to know a lot more before a valid answer could be provided. The surface you choose can work both for and against you. If it's dead flat, and the mounting surfaces are as well, it's the best of all worlds.

If, by contrast, the surface you provide isn't flat, and it's rigid enough, it can influence the bed of the machine. You can get around that by shimming the proper mounting points. Might be a good idea to post a picture, so we can see what you're up against.

Harold
jeff408
Posts: 3
Joined: Mon Jan 11, 2010 4:39 am
Location: Wash state

Post by jeff408 »

I'll have to take you up and stop by sometime. Here is a link to my machine with the specs. http://www.grizzly.com/products/g4015z. Also its not mounted its just sitting on the steel plate. I'll try to get some pics coming.
Jeff
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Harold_V
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Post by Harold_V »

Ok, managed to see the machine, although the link isn't good. They've changed their web site.

I now understand the swing/center distance relationship.

Considering you have the machine sitting without restraint, it's unlikely that it is anything but flat (parallel). However, depending on how the machine was handled when it was machined, it's entirely possible that it could have a slight twist in the bed, which always manifests itself as taper in the cut. Should that be the case, you may be able to eliminate the twist by bolting the machine to a rigid surface, then shimming in the appropriate place.

Taper is common when you are turning material that is not supported on the opposite end. Also, if you are using the tailstock, taper may be caused by the tailstock being offset. That's a feature that allows you to turn intentional tapers. Before you jump to any conclusions, it would be wise to provide more information on the taper of which you spoke.

Harold
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