MichaelMouse
Member
Registered: 05/17/05
Posts: 8127
|
|
robo hippy said:
MM, I don't really consider a Reeves drive a 'variable speed' lathe. You can change gears without having to stop the lathe, and change pulleys, but not vary the speed beyond those ranges. I have found that factor incredibly useful in my years of turning.
Does FPM change how the cut goes? Well, for sure, it changes your feed rate for heavy stock removal. I always looked at it as a 'more cuts per inch' thing, which leaves a better cut/surface in my opinion. Mostly, for me it just makes the job easier, as well as faster.
What do you call a Reeves drive, if not variable speed? You can set 500, 501 or 499, right? Maybe even 499 1/2. Not like setting 360/680 on pulleys with a multi-speed lathe.
At 660, the lathe brings the same spot past the tool 11 times in a second. Let's imagine you're removing 1/10 th of an inch of stock with the tool. That's "one Mississippi" as you push your finger one inch along a ruler. If you present the same tool the same way at 1320 can you really push your finger that much faster to make it worthwhile to encounter four times the potential pitch energy it develops?
You don't need to increase FPM to remove more stock. Go wider, not deeper, and you can move more material. Might have to change the tool of choice to permit a broader shaving, but it gives you more control, so it's certainly worth it. Plus, if you're feeding faster when you're rotating faster, you're sacrificing several of the"cuts per inch" you're talking about - right? So maybe it's not much better than rotating and feeding at a more sedate and SAFER rate.
Finally, cuts per inch doesn't produce a smoother cut with a single blade. Even slow feeding your jointer won't produce the surface that a nice #4 at one cut per however many inches the board is long does. That's what you want at the lathe, continuous shavings.
--------------------
Better to follow the leader than the pack. Less to step in.
|
robo hippy
Member
Registered: 03/31/06
Posts: 989
Loc: Eugene, OR
|
|
With the Reeves drive, you change spindle speed, but not motor speed, correct? Not the same thing as dial a speed. I have turned a couple of times with a Reeves drive, and in my opinion, there is no comparison between it and the 3 phase variable speed on my lathe now. I guess if every piece was perfectly balanced, or nearly so, not much of a problem, but a lot of my pieces are never that way.
If you take a wider cut, then you need more torque to push the blade through the wider shaving as more steel is into the wood at one time, than when using a higher shear angle, or are you saying that by going wider rather than deeper you use the same force.
With feed rates, if our feed rates are the same, and if you are turning at 660 rpm, and I am at 2000 rpm, I will have 3 times the cuts per inch that you do. To me, this means a much finer cut/shaving, which in turn means a cleaner cut. This to me would include a high shear angle bevel rubbing cut.
robo hippy
|
MichaelMouse
Member
Registered: 05/17/05
Posts: 8127
|
|
robo hippy said:
With the Reeves drive, you change spindle speed, but not motor speed, correct? Not the same thing as dial a speed. I have turned a couple of times with a Reeves drive, and in my opinion, there is no comparison between it and the 3 phase variable speed on my lathe now. I guess if every piece was perfectly balanced, or nearly so, not much of a problem, but a lot of my pieces are never that way.
If you take a wider cut, then you need more torque to push the blade through the wider shaving as more steel is into the wood at one time, than when using a higher shear angle, or are you saying that by going wider rather than deeper you use the same force.
With feed rates, if our feed rates are the same, and if you are turning at 660 rpm, and I am at 2000 rpm, I will have 3 times the cuts per inch that you do. To me, this means a much finer cut/shaving, which in turn means a cleaner cut. This to me would include a high shear angle bevel rubbing cut.
robo hippy
Stop and think. A motor operating at synchronous speed is developing full torque. A motor working at other than synchronous, even with the most expensive frequency/voltage controller, isn't. Makes the Reeves superior.
Operation at less than full rated torque might be why you feel you can't shave wide at will, or it might be you're not shaving, but shoving. When you do it right, the wood runs down the edge, not into it. The shaving falls or runs down the flute, rather than rises. That's what Frank Pain meant when he said let the wood be your teacher. It will show you how it wishes to be cut.
When you "get" it, you can swing 1/2" shavings with a 1/2" gouge.
What's instructive here is to see that the one side of the shaving is thick and smooth, while the opposite side, where the gouge exits the cut, is feathered thin. Means there's almost no lift or possibility of tearing grain by the roots.
Cuts per inch has nothing to do with a single blade. It is terminology used with multiple circular cutters which actually exit the cut on their own. You want a nice, smooth, long shaving.
--------------------
Better to follow the leader than the pack. Less to step in.
|
robo hippy
Member
Registered: 03/31/06
Posts: 989
Loc: Eugene, OR
|
|
So you have never turned with a 3 phase converted lathe??? I have no trouble pulling an 1 1/4 inch wide shaving with a 1 1/4 inch scraper. I stalled the reeves drive with a 1/2 inch gouge. The converter and 3 phase motors allow torque to remain much more constant over a huge range of speeds.
robo hippy
|
MichaelMouse
Member
Registered: 05/17/05
Posts: 8127
|
|
If memory serves, all the lathes at the college were 3ph motors. Except, I think for a big squarish Delta, all were Reeves for varying rpm.
Anyway, for those who might wonder why EVS lathes have larger amperage (HP) than their mechanical counterparts, it's because they need it low end. Seems if you're giving 45 pushes per second you have more "glide" time than if you're giving 60. Plain facts. Sorry.
In the air, we used 400 Hz. Them was some motors!
--------------------
Better to follow the leader than the pack. Less to step in.
|
robo hippy
Member
Registered: 03/31/06
Posts: 989
Loc: Eugene, OR
|
|
MM,
The following is a list of some of the lathes I have turned on. They are ranked in order from least to best, in my opinion.
12 inch Jet with a Reeves drive.
12 inch old green PM with Reeves drive, it was not well tuned up
12 inch Atlas with a 1 hp motor and 4 speeds
12 inch Jet mini lathe vs
16 inch Nova like yours, 1 hp, and a bunch of pulleys
16 inch Nova with a 1 hp DC motor, bunch of pulleys
16 inch Jet with a 1 1/2 hp, 110 volt motor
Nova DVR 1 1/2 hp 110 volt
PM3520A 2 hp, 220 volt
Robust Liberty 2 hp 220 volt vector drive converter
Robust American Beauty 3 hp 220 volt.
Those in a group show no huge performance differences. The spaces indicate a step up. The Nova DVR is kind of in a class of its own, a nice lathe but I don't like the speed changing mechanism. The rest are a big step up. You most likely never have turned on my top 4. Things have changed a lot.
Try them out some time if you get the chance, you might like them. Some times new and improved is a good thing.
Have you ever tried cutting at higher speeds?
robo hippy
|
MichaelMouse
Member
Registered: 05/17/05
Posts: 8127
|
|
robo hippy said:
Have you ever tried cutting at higher speeds?
Certainly. But once I learned how the wood wishes to be cut I didn't have to. Slower is safer, and when there's a slicker outcome, no sense changing. Haven't had a lathe over ~1500 in the last thirty years.
--------------------
Better to follow the leader than the pack. Less to step in.
|
Larry528
Dances with Lathes
Registered: 10/25/00
Posts: 7260
Loc: Mesquite TX USA
|
|
As a slow speed junkie, I sense that turning at higher speeds dictates that what you turn or rather the wood you turn had better be void free, no hints of splits or hairline cracks. At 450 rough cut, then finishing at 650 or so, I can turn mesquite that has many cracks filled with minerals, punky spots in maple and hairline breaks in pecan. Its not the cutting that would bother me but the flying off of the possible sudden low orbit satelite that does. At 1100 rpm the distance and impact would be still held to basic laws of physics.
--------------------
I thought I had dyslexia, but found out I am just spastic
|
hairy
Honored Veteran who Shoe horned a win
Registered: 01/08/11
Posts: 282
Loc: The Nati
|
|
I'm with you on the slow speed. I use it as much as high speed. Great for sanding. I'm talking less than 100 rpm.
For me, it's the way to learn how a tool cuts. I can see it all better and safer at low speed.
Back in the day when those guys were using treadle lathes they did some very good work. I wonder how many rpm they got up to. Sure, I know about pulley to pulley ratio and all that, but if they wanted to speed up they worked up a sweat.
|
robo hippy
Member
Registered: 03/31/06
Posts: 989
Loc: Eugene, OR
|
|
When I turn at high speeds, it is ALWAYS good solid wood. I almost never turn anything that has cracks or voids in it. In part because it takes too much time to repair all the cracks, and most of what I turn is utilitarian, and intended for daily use. I could not guarantee a piece that has knots or repaired cracks.
I also agree with slow sanding speeds as I can see the wood and what needs to be sanded out that I would not be able to see at higher speeds, which would require many more times of turning the lathe off and on. Most of the time, I sand at 20 rpm or so, even if the bowl is not warped. Slow drill speeds as well, 600 or less rpm.
I have never understood 'cut the wood as it wants to be cut'. Heck, with roughing, I get the waste out of the way. Tear out is not as important as getting the shape. Getting rid of tear out is what finish cuts are for, and is done after the shape is achived.
robo hippy
|
|
Previous
Index
Next
Threaded
Re: What makes a good lathe?
[Re: 
Edit
Reply
Quote
