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Weight for the PM 3520B

Eldon DeHaan

Eldon DeHaan

Joined
Dec 11, 2009
Messages
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Location
Salt Lake City, Utah
Has anyone found it necessary to add weight to the lower shelf brackets of the 3520? I'm just setting up my new PM and wanted some direction on weither I should place a 1"x17"x48.5" steel plate on the bottom brackets? That's about 230+ lbs. I don't know if that is an issue with the brackets holding that amount of weight? I have read that some use 2"x6"s and ply with sand as the weight, but that is only about 125 lbs. Any opinions on this idea? Thanks for any help.....Eldon D
 
Weight add on PM 3520

Eldon DeHaan said:
Has anyone found it necessary to add weight to the lower shelf brackets of the 3520? I'm just setting up my new PM and wanted some direction on weither I should place a 1"x17"x48.5" steel plate on the bottom brackets? That's about 230+ lbs. I don't know if that is an issue with the brackets holding that amount of weight? I have read that some use 2"x6"s and ply with sand as the weight, but that is only about 125 lbs. Any opinions on this idea? Thanks for any help.....Eldon D
Click to expand...

I have about 400 lbs of sand on mine and it really helps when ruffing green big blocks. The shelf of ply seems to have held up nicely for 10 years. Phil
 
The stand has a good broad footprint, and the lathe will turn at low speed. If you have a bandsaw or a good drawknife, you should be able to use that shelf for other things, like a bag for shavings, rather than a bag of sand.

If, however, you throw heavy, untrimmed and unbalanced pieces on it and turn at high rates of speed, you might need to "weeble" it. You'll might also be replacing the bearings (and perhaps your teeth) soon.
 
I used a 2x10 to add a shelf to the feet. I put 300 lbs of pea gravel in plastic bags on the shelf. I turn a fair amount of offcenter work and when roughing I like to use the fastest safe speed that I can. The extra weight definitely helps. I've had my lathe for about 6 years now with no problems.
When I have time and money (at the same time) I'm going to build a box to hold the gravel and then add some drawers up above to store tool rests, faceplates, etc.
 
Eldon DeHaan said:
Has anyone found it necessary to add weight to the lower shelf brackets of the 3520? I'm just setting up my new PM and wanted some direction on weither I should place a 1"x17"x48.5" steel plate on the bottom brackets? That's about 230+ lbs. I don't know if that is an issue with the brackets holding that amount of weight? I have read that some use 2"x6"s and ply with sand as the weight, but that is only about 125 lbs. Any opinions on this idea? Thanks for any help.....Eldon D
Click to expand...

The only limit on the weight of sand is the amount of space between the shelf and bed. Sand is cheap and steel is not. Sand provides much better damping than steel. I know a number of turners who have the Powermatic 3520 lathe and none of them add any weight to the lower shelf other than using it to store stuff like chucks and turning tools.
 
I have had my PM 3520A since 2003 and have never seen the need to add weight to the stand. Most fo everything is wet and off balance and with the variable speed I can get the piece to run with out chaseing the lathe all over the shop.

When I say off balance I mean I will split a log and put it between centers and balance it the best I can and turn away. I never use a face plate when I rough out bowls.
 
Robert Manning said:
It depends. If you are adding two hundred pounds of gold just below the ways, to a stock machine, then you are lowering the C of G. If you are taking weight from the bottom shelf and moving it up, then you are raising it.
Click to expand...

Or feathers, for that matter. The issue really gets dicey (CG), when there is a large mass attached to the headstock and spinning. You would want to see the CG as low as possible.
 
Steve Worcester said:
Or feathers, for that matter. The issue really gets dicey (CG), when there is a large mass attached to the headstock and spinning. You would want to see the CG as low as possible.
Click to expand...

Well, you want your counterweight on a nice long arm to multiply its effect, that's for sure. Weight on the back legs, which want to rise when the load is moving CCW is most effective.
 
lathes are designed to add weight differently.

The Nichols has a huge box to fill with sand. It must hold a yard
the big Oneways have a hollow tube under the ways to fill with sand bags.

Before you add weight get the leveling feet a near perfect as you can.

I start with a level on the bed and get the bed level. I then put an out of balance piece on, crank up the speed until it vibrates, and tweak the levelers until the vibration is minimized.

It seems like the best design is the Nichols since you are essentially weighting the head stock. Weight the ways and you have some vibration where the headstock connects to the ways. Weight the legs and there is some vibration where the head stock connects tot he ways ans some where the ways connect to the legs. As long as the bolts and other connecting mechanisms are tight this vibration is probably insignificant.

A wide footprint of the feet does a lot too.
a simple A frame bolted to the head stock end of light lathe does wonders.


happy turning
Al
 
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H 2 O

Water. Cheap. Self-tuning. Easy to add, and easy to remove (siphon if necessary). Fill no more than about 2/3 tank or bucket height for slosh allowance. Add a transparent cover, to protect against chips and to observe ripples. YMMV.

Happy Holidays to all.
 
Makes a lot of difference

I added a shelf and about 200lbs of sand to mine and took the cheap leveling feet off and made white oak spanners that go front to back on mine. A couple of shims to maintain as much surface area touching the concrete floor and I can put an 80lb semi-balanced blank on and start roughing at 250-400 depending on how balanced. Before I did that I could barely go 150rpm and the lathe would want to wander. So for me it made a world of difference.

Jeff
 
I have 400 lbs of sand on mine. I've been thinking about redoing my shelf and raising the lathe to allow me to build a cabinet for under-lathe storage. I do like turning very out of balance natural edge pieces, and at decent, not high speeds. Its impossible to get a good finish cut on an uneven edged piece when you're turning slow. Even with the weight, turning out of round pieces will definitely make the machine move. Maybe I'm impatient or asking too much of the machine, but I'd like it to weigh about 1500lbs. My next lathe will be a "Serious".
 
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