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Jeff Jilg, & other PM3520A owners

W

W.C. Turner

Joined
May 27, 2004
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Hello,

I assume, that ya'll use the low speed range, on the 3520a, when spinning larger bowl blanks?
 
You may safely assume I turn at a very slow speed at first. The PM has 2 pulley settings and a true variable speed motor. I do a lot of spindle work and small turnings (under 10") so genarally the over all weight of a given object is relatively light compared to the weight and mass of the lathe. So most times my pulley position is in the high speed position. The only time I use the low setting is when torque may be an issue when turning a very heavy piece. Any new piece light or heavy is always started at a low speed. I hope this is of help,

Jim
 
Barry Only in rare circumstances do I turn at anything aproaching high speed. I always start bowls very slow. I see no advantage to getting hurt. When everything is running true with no vibration then I turn the speed up. If I hear anything unusual at all I stop the lathe and investigate.
 
Hi W.C.

That is correct. For bowls and platters, the low range is fine. Since I rarely do spindle work I have never used the 2nd range. For me, 0-1200 is perfectly fine, and it is rare that I even get to 1,000 RPM.

In fact, with all those hours on my lathe I think I may have put it on the 2nd set of sheaves just once. Then I turned it all the way up. Nothing was on the lathe. Satisfied that it didn't blow itself to pieces I then turned it off and put it back on the 0-1200 set of sheaves. :cool2:

If you have sharp tools and you just do bowl work (even 4" bowls), 1200 RPM is probably the most you need. For the big puppies (16"-20") they rarely get turned above 600 RPM. And during the roughout process it is usually 300-400 RPM. Sharp tools will take off plenty of wood without the need for speed. I've got enough excitement in my life already - don't need to get a catch on a big piece to make it more exciting.

And of course, these are just my opinions. Others may feel safer turning at a higher speed. Tonight I roughed out 4 more Box Elder pieces, all about 12" diameter. The maximum speed I hit during those roughouts was probably 600-650 RPM (just past the halfway mark on the dial). Sheesh does that stuff stink or what....Theresa told me to quit going in and out of the garage!

I do wish there was an option for a larger HP motor. The lathe is sufficiently designed to take the higher torque and stress. For big pieces 50-150 pounds, the 1.5 HP motor sometimes is lacking.
 
Pm3520a

I turn columns up to 18" by 10',face plate work to 32" and anything I can get between centers and have no problems. I made my own bed extension to do 10' between centers and an out rigger for the tool rest so I can do 40" faceplate work. When I bought the 3520A I set a budget of $5000 and after a lot of research I settled on the 3520A. Over the last 5 years I have created literly tons of shavings and am extremly happy with the 3520A. If I bought a lathe today it would be the 3520B.
 
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Torque

<"I do wish there was an option for a larger HP motor. The lathe is sufficiently designed to take the higher torque and stress. For big pieces 50-150 pounds, the 1.5 HP motor sometimes is lacking.">

Jeff, My 3520a has a 2HP motor.

My original posting of this thread was kinda followup on my "Between Centers" thread.
I had forgotten, that I had mostly used my lathe in the "High Speed" range, since I got it. And, I was wondering why I had the problem with the drive ctr. spinning in the larger bowl blanks.

Then, I remembered that 3520 was in the high speed range, & thought that was most likely, the primary cause of the problem. I haven't followed up much on this yet, but, what little I did, seems to have helped a great deal.

And, I knew Jeff, had turned larger pieces, many hours on his 3520, & I had hoped he would reply to my between centers thread. When he didn't, I posted this thread with his name in it.

Thanks,

W.C.
 
Sorry I didn't catch the question in the other thread - must've missed it.

My 3520a probably has a 2hp on it as well. 3HP would be a good option.

I use a 2" drive center with 4 spurs that fits in the #2 jaws of a Oneway Stronghold chuck. It's a good drive center, and hard as heck to spin the wood on it! However, I have spun the center inside the #2 jaws a few times. And it really messed up the inner faces of those jaws, as well as the drive center.

As a result when I replace that set of jaws I'll drill a hole for a set screw to keep the drive center insert from spinning. Currently I just crank the jaws real tight now to keep it from spinning. Maybe I should just get a dedicated 2" wide drive center on a #2 morse taper since it seems that I end up turning large pieces all the time.
 
When turning bowls or anything needing 1200 RPM or lower, it is good to use the lower setting. it increases the torque, but it also keeps the motor RPM up and thus the motor fan speed is up and you put less load on the inverter. 🙂
 
I spindle turn occasioinally on my 3520 and I do go to the high speed pulleys then. I like to turn spindles at 1800-2400 rpm. For 90% of my work I saty in the low pulley.
 
There seem to be two topis

A. Which speed range. Using the lower speed range gives you more torque but also finer adjustment of speed. That is a a small turn on the speed knob changes the speed less than the same small turn on faster pulley setting. Turn at the speed you are comfortable with and one that gives minimum vibration. When roughing an out of balance piece you will have some vibration. Sometimes a slight increase in spoeed will reduce vibration.

B. How to use the spur drive. I start turning just about every piece between centers using a 1" spur center. A spur drive will not spin in the wood if i remember to follow a few simple steps.

1. drive the spur into solid wood using a wooden mallet. When mounting the spur on the bark side I drill a spot with a 1 1/4 forstner or make a flat with a square chisel.

2. Orient the spurs at 45 degrees to the grain. This lets the spurs drive in evenly. This is a small detail but it will improve your results. If you have two spurs running witht he grain those will drive in and the two running cross grain will resist driving in.

3. Be sure you have solid wood for the tails stock center.

4. Keep tightening the tailstock center. On the Powermatic you do not have to lock the tailstock it will not open. As you are roughing take a few cuts and tighten the tailstock. Keep tightening every few cuts. As you are roughing the spur drive and live center work their way deeper into the wood.
You must keep tightening the tailstock or the spur can loosen and spin.

5. Use proper turning techniques. A severe catch may cause the spur to sin. This is a safety feature. In a severe catch something has to give: the wood, the tool rest, the tool, the motor stops.


I have had a couple hundred students turn bowls between centers and about 1 in 15 will get the spur spinning because they forget to tighten the tailstock.

happy turning
Al
 
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Kurt - I got the 4 flute center (insert for oneway chuck) from bestwoodtools.com. There are a few vendors out there and that is the one I happened to choose. Get the 4 flute model. It's the same price as the 2 flute model. And if you end up not liking the other 2 flutes, just grind them off.

It's a good insert. But as I've stated in this thread or another one, I do aggressive turning between centers. As a result I spun the insert in the jaws during a catch. That really messes up the ridges on the ribbed jaws, and the ridges on the insert. Since it is already messed up it doesn't matter at this point.

But if I was getting a new one I would do the following:
  • tighten the insert into the jaws
  • drill and tap a hole through one jaw into the insert
  • put in a setscrew during usage

This will prevent the insert from spinning if you get a catch, and that will protect the ridges in the ribbed jaws. The big advantage of this insert is that I don't have to drive it out of the morse taper - I can just unscrew the chuck.
 
Bestwood tools also makes a large spur drive that screws onto the headstock. I have had one for a few years and it works outstanding. Then again, it is a large center, probably 1.5" across.
 
Brian Hahn said:
OK, I'll bite. Why not just use a jumbo-sized Morse taper drive center?
Click to expand...


Reason No 1: They're about as easy to find as hen's teeth.

Reason No 2: If you found one and used it, you might have a fair amount of trouble getting it back out of your spindle because the added force acress wide wings could shove the taper too far into the female taper.

I use a MT taper for small stuff, but have a big'un (4-blade) that spins onto the spindle and removes with a wrench. It's similar to the bestwoodtools' spin-ons but heavier yet. Stubby made a few as prototypes, but they were too expensive to market. I got mine at cost when I bought my lathe. With that big a cross section, it was hard to get it set in the wood until I carefully reground the wings with a slight slant towards the middle. Now, when more pressure is applied, more of each wing engages the wood. Doesn't slip at all.

Don't think I'd want one of those chuck-hold inserts. I'd be concerned about bending a chuck jaw. I'd rather pull the chuck and spin on the big one.
 
Brian - it's reason #2 that Mark listed. If you use a lot of force between centers it drives the item into the morse taper with a lot of force. As a result it's hard to get it back out.
 
Brian Hahn said:
OK, I'll bite. Why not just use a jumbo-sized Morse taper drive center?
Click to expand...
Bite, I get it 😉

It's larger, won't slip in the taper and you can apply greater pressure on it because it spreads the pressure over a larger area, thus less stress on the headstock's bearings.
 
Same as what Steve said. If I use a 1" drive spur I might as well use a drill bit instead because it will just drill into the wood anyhow. The 2" wide flutes on the drive spur I use, work great because they hardly ever spin. Any catches that could occur would just stop the piece, or tear off a small chunk from the wood.

....not that any actual catches would occur in my shop.... :cool2:
 
Ah yes, the old frozen drive center trick.

I can do it perfectly even with a mini-drive center. Two easy steps:
1) Run the lathe for a while to warm up the head stock, then
2) Slap a cold drive center into the warm taper.
=> The drive center expands as it warms up, freezing it solidly in the taper.
 
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