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PM 3520B outboard turning bed extension

B

Bob Comerford

Joined
Dec 7, 2012
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Location
Wakefield, Rhode Island
Have a 3520B and would like to be able to turn outboard but between centers. The stock 18"outboard bed extension is functional but too short for a tailstock for between-centers turning.

Question: Do any of you know of an aftermarket bed extension (or one for another kind of lathe) that will fit the 3520B bed, even with some customization, and that is around 25- to 30-inches long?

Bob
 
Bob Comerford said:
Have a 3520B and would like to be able to turn outboard but between centers. The stock 18"outboard bed extension is functional but too short for a tailstock for between-centers turning.

Question: Do any of you know of an aftermarket bed extension (or one for another kind of lathe) that will fit the 3520B bed, even with some customization, and that is around 25- to 30-inches long?

Bob
Click to expand...

You can add an entire powermatic bed. need something like that for 30"

I'm curious as to why you want two Longbeds in each direction?
 
I think that you are confusing terminology or else I am being confused by your description. Outboard turning means turning without a tailstock since it is ... outboard, meaning outside the bed of the lathe. That is what is making me think that you are looking for bed extensions. Have you considered putting an 18 inch extension on both ends? That will give you three more feet between centers. One of my club members has done that on his Powermatic. On one occasion, he needed to make some architectural columns so he bolted two beds together plus the two extensions. Unless turning a ship's mast, that should handle most needs.

Since you mentioned outboard turning in conjunction with using an extension, I am wondering if you have your extension mounted in the auxiliary holes on the legs for mounting the tool rest base when doing large outboard turnings. Perhaps it would help if you described what you are wanting to turn.
 
Bill Boehme said:
I think that you are confusing terminology or else I am being confused by your description. Outboard turning means turning without a tailstock since it is ... outboard, meaning outside the bed of the lathe. That is what is making me think that you are looking for bed extensions. Have you considered putting an 18 inch extension on both ends? That will give you three more feet between centers. One of my club members has done that on his Powermatic. On one occasion, he needed to make some architectural columns so he bolted two beds together plus the two extensions. Unless turning a ship's mast, that should handle most needs.

Since you mentioned outboard turning in conjunction with using an extension, I am wondering if you have your extension mounted in the auxiliary holes on the legs for mounting the tool rest base when doing large outboard turnings. Perhaps it would help if you described what you are wanting to turn.
Click to expand...

Bill,
I have a bed on my oneway 2436 outboard. I can start a 30" platter between centers.
It will turn 48" but I haven't done anything that big.

I think of outboard as being the left side of the headstock.

Not sure their is a standard definition of out board.

Al
 
I assume he's talking about using the in oars side of the headstock with the headstock slid to the end and the bed extension in the lower position which you can do on the 3520b. You could probably buy a full length bed And mount it low but would probably have to build a support for the loose end
 
John Lucas is correct. I'd like to be able to turn outboard--off the right end of the bed--in the 3520B's lower bed extension position but between centers. The 18" bed extension is not long enough to take a tailstock (with riser if one could be found that fits) and a banjo with a big blank mounted.

I'd like to avoid getting the 50" long bed extension for the 3520B. It's just too long and too expensive for turning the occasional piece greater than 20" around! However I'm sure it'll mount to the lower holes in the right end of the 3520B, just like the 18" bed extension does, and would give me more than enough length for turning thick blanks (I could turn a Volkswagen!!) up to around 36-inches in diameter; more than enough for my needs. But to turn between centers on it, I'd need a riser block to raise the tailstock. There apparently isn't one for the 3520B.

There is one for the 4224B, at least it reads like there's a riser block for the 20-inch 4224B bed extension in PM's literature.

So this boils down to whether the beds on the 3520B and the 4224B are the same size. The 4224b has four holes in the end of the bed whereas the 3520B has three. But the ways may be the same dimensionally on both. Does anyone know about this?

Thanks in advance for any advice you can give me.

Bob
 
'Just answered my own question about 4224B vs. 3520B outboard bed extensions. The 3520B uses three 3/8"-16 x 1-3/4" bolts; 4224B uses four 1/2"-20 x 2" bolts. So that idea's out the window.
 
Bob Comerford said:
John Lucas is correct. I'd like to be able to turn outboard--off the right end of the bed--in the 3520B's lower bed extension position but between centers. The 18" bed extension is not long enough to take a tailstock (with riser if one could be found that fits) and a banjo with a big blank mounted.....
Click to expand...

For a moment I considered that you meant that, but figured that surely wasn't what you meant since you didn't say anything about getting a riser for the tailstock. Basically, what you want is to make your lathe into a gap bed model. The easiest solution is to use a faceplate and forget about starting between centers. I know this is not what you were asking, but I don't think that there is an inexpensive solution for doing what you want to do. For initially balancing the piece, you could make a fixture to get the center of mass on the axis of rotation and then affix the faceplate.
 
When I called about the new 2442 bed extension to see if it would work on the 3520 they said no and that was directly from the factory.
I've never seen a sort of midi bed extension. I suppose it wouldn't be hard to build if you can find someone to machine the top surfaces. You will have to build or buy a tool post extension as well as a riser block for the tailstock. I just bought the metal to build the tool post extension. I haven't looked into using the tailstock yet. I have a 3520A and will have to modify it to be able to lower the bed extension that I already own. It's 18" long so it would allow using the tailstock for bowls that aren't too deep.
 
Thanks to Bill, John and Rob for your thoughts. I've checked out the mustard monster site and there are indeed some great ideas there.

John: PM has an 18" bed extension with tool rest extension (as a kit) for the "B" that attaches to the hole set that's 9-inches below the bed. That's fine for using a chuck, but I don't think there will be enough room to mount the tailstock on the extension along with the extended tool rest. It might work for platters, but not for the huge pieces of maple and white oak in my back yard, half of which are quite deep. I'm seriously considering mounting my tailstock in the vise on my workbench off the end of the lathe (the height is almost perfect), and backing the lathe up to the tailstock with a blank mounted in the chuck above the 18" extension. I could use a rachet strap or my small come-along to keep it tight.

I'll let you know how that works--I'm only marginally optimistic that it'll work.

Bob
 
I think that you will need a more solid arrangement than that -- basically the headstock and tailstock need to be hard mounted to the same rigid body. What you described sounds like there are some opportunities for compliance (deflection under load) between the headstock and tailstock. It would not take much deflection for the wood to slip loose from the live center. While a come-along sounds like a good idea and it is for a lot of things, it is not a position holding device -- it is a force loading device, which is the equivalent of putting a big spring between the headstock and tailstock. If the spring could be made stiff enough, the compliance becomes insignificant, but it is hard to say what would be needed to achieve that level of stiffness short of hard-connection mounting.
 
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