2 ?? on Sanding.

[Guest]

I've read a few turners recommend "turn fast,sand slow"
Fast is however much nerve I have when changing pully speeds.
1.How slow do you sand if you intend to put the finish on the blank before removing from the mandrel?

I can see where a reversing lathe is a nice feature when sanding,
2.Does anyone reverse their blanks while sandingso teh rotation in one dirction doesn't "crush" the fibers rather than "shear" them?

Just a couple of things I've been wondering about since I've started turning.

 

[Fred in NC]

Eagle:

1. My sanding speed is such that I won't easily burn the blank or finish. About 800 RPM or so. More important than the speed, in my opinion, is to keep the sandpaper moving. That is why I use long narrow strips of sandpaper, about 5/8" by 4-1/2". That way I can move the sandpaper up and down, and sideways over the barrel.

2. The variable speed DC motor in my lathe does not reverse. Good sandpaper should not crush the fibers anyway. I think fibers tend to get crushed with too much pressure from the sandpaper. A ligth touch is better.

I built a stand for my Jet Mini so I could install a variable speed DC motor and controller under the lathe. Speed range is about 60-4000 RMP. I seldom go above 2000 RPM, but the slow speed comes in handy for applying finishes, sanding with the grain, and removing sanding dust from the blanks. Photos in my album.

The above works for me. Your mileage could vary.

Fred

 

[tipusnr]

I sand at the same speed that I turn. As I don't put any finishes directly from the container onto the blank, it hasn't been a problem for me. Actually, haven't really even thought about it so I will probably get a lot from this discussion.

 

[Fred in NC]

I am no expert on this or any other subject... so please take my observations with a grain of salt, or a whole pound, if you wish!

Lathe speed or RPM is of course related to <b>surface speed</b>. However, it is the surface speed that affects the end result. For that reason RPM recommendations cannot be the same for bowl turning and pen turning. Pen turning is <b>spindle turning</b> and of small diameter at that.

A 6" diameter bowl turning at 1000 RMP has a surface speed of about 18,800 inches per minute. A pen 3/8" in diameter turning at the same speed has a surface speed of 1,180 inches per minute.

That is the reason we can go faster when turning pens than bowls. That is also the reason that large lathes usually have a lower minimum speed. Some large lathes go down to 60 RPM which is still fast in terms of surface speed if you are turning a very large diameter piece.

The speed limit for sanding pens, in my opinion, is the speed that we feel comfortable at, and minimizes the risk of burning the barrel.

Again, just my 2.35 cents... your mileage might vary.

 

[C_Ludwigsen]

I turn fast, sand slow. My experience has been that I get a cleaner cut somewhere in the 2800 RPM range (pens only - I don't rough bowls there []).

For sanding, here is why I sand slow... The possibility of burning is definitely an issue. And you are more prone to laying fibers down instead of cutting at a fast speed. In addition, if you sand fast with the lower grits, you certainly run the risk of removing too much material. A pen is not like a bowl where you can take too much away and correct it by shaping. If you take too much material away from a pen, you either have variances at the metal/wood joints or you can lose the whole tube.

Sand paper should cut, not polish.

Eagle, regarding the belt changes... I have the Jet 1236 at home so don't normally have to deal with it. But I did an all day demo at our club's Turning Fest this past Saturday on a Delta Midi. I had to deal with the belt changing issue. The belt was in the middle speed for the first pen. I felt the cutting was too slow and the sanding was too fast.

For the 2nd - 4th pen, I went back to my pattern of slow barrel trim / fast cut / slow sand / fast polish. I was much happier. It was 3 belt changes for each pen but it gave a great break for questions. By the end of the demo, I was changing speeds fairly quickly.

I needed to get used to that anyway as I'm saving to buy a Vic VL100 from a friend.

Hope this helps. Chuck.

 

[jrc]

I turn and sand at the same speed 2600 rpm or so. Just learn how to sand at that speed.

 

[William Young]

Fred in NC you said

*I built a stand for my Jet Mini so I could install a variable speed DC motor and controller under the lathe. Speed range is about 60-4000 RMP.*

Does this mean that a speed controller can be added to manual speed change lathe as in a Jet Mini Lathe ? If so, please suply particulars like price and availability of the controller etc..

As for the turn fast, sand slow question.,
I use second or third speed from the top for all applications of pen making. It was only when I started making bowls and goblets and platters etc. that it seemed like a varaible speed system would be nice.
W.Y.

 

[Fred in NC]

Drew: I agree ! Quote from my previous post:

"The speed limit for sanding pens, in my opinion, is the speed that we feel comfortable at, and minimizes the risk of burning the barrel."

I can sand faster when using narrow strips of sandpaper, since I can keep it moving from side to side, and up and down. There is less risk of getting it too hot that way. My strips are about 3/4" by 4-1/2, cut from quarter sheets.

In penturning, as in other fields, it is the final result that counts. If it works for you, and is safe, then that is the best way.