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group pricing for 3520a riser post and plate

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If you are interested in the following please email Bob Hadley or myself directly and I'll coordinate the list of interested folks:
bphadley@pacbell.net
jjilg@sbcglobal.net

Bob Hadley and I are considering the following. We would like to get extension plates and toolpost risers machined so that we can turn pieces larger than 20" on our 3520a's. See the picture of the extension plate that Bob designed on Yahoo:
http://f2.pg.photos.yahoo.com/ph/bphadley@pacbell.net/album?.tok=phOTtXBBUD1es2Q4&.dir=/2a5b&.src=ph

The plate allows the Powermatic bed extension to be lowered. The toolpost riser is an extension to the toolpost to bring it up to the centerline of your turning.

To amortize out the cost we believe the machinist time would be lower because of setup time if they machined 5-10 sets of riser adapters. We are looking for other folks who would be interested in purchasing the machined risers + shipping cost. Bob and I will price them in our areas and re-post the estimated cost back to the list of interested folks.

The riser would be made of a 2-1/2 inch dia, length of 7075 bar stock. It's an easy part to machine. One end is turned to the tool post dia, the other drilled to the tool post dia. A threaded hole to add a handled bolt to lock it down. The riser just has to be long enough to allow some meat between the hold and the post.

We were thinking the extension plates could be cut at the same time - the machinist could probably cut them with a blowtorch and clean off the edges with a grinder.

....Jeff Jilg :cool2:
 
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I'm interested.

This could be an interesting addition to my lathe. I would be interested in knowing the price.
And while you have the interest of all 3520 lathe owners, is there anyone near New Jersey who has a bed extention I could rent or borrow for a couple of weeks?
 
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Tool Post Riser.

Jeff this seems like a great idea. I have been using my 18" extention lowered four inches, along with a tool post banjo from a 4224. My only concern with the tool post riser is the added leverage being exerted on the 3520 banjo. While coring blanks I have felt that I have been close to the breaking point. If the posts dont pose a breakage threat, I would be interested. thanks Gary
 
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Should be no problem at all for a 2-inch diameter riser to handle any load in compression that you'd encounter. The shoulder of the riser sits on the face to the banjo, so the compression loads are transmitted across a pretty large area. What happens with any lever that long is it is going to try to twist the lathe bed -- which, given the mass of the cast iron extension, isn't going to happen to any significant degree (notice I didn't say it would NOT twist -- only that it would not be significant).

The adapter plate would allow you to mount the extension anywhere between 4 to 8 (8+?) inches below the bed. If you plan to outboard turn to the full swing, you'll need a banjo/rest combination that is capable of moving as far off center as 1/2 the swing, plus any additional overhang you require. Not by coincidence, my banjo and 14-inch rest can SAFELY extend to the limit of my lathe's swing (7+7=16).

I compensated for that on a previous lathe by mounting the outboard bed extension off the lathe centerline (biased toward the turner, of course). That is something I’ll probably consider before I cut any adapter plates – to allow enough margin for an offset mounting. And even with that you may still need a longer rest or one hefty banjo depending on how big you plan to turn (than goodness for electronic speed control is all I say).

BH
 
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Bob and Jeff. Did you ever proceed with this project?

Jeff Jilg said:
If you are interested in the following please email Bob Hadley or myself directly and I'll coordinate the list of interested folks:
bphadley@pacbell.net
jjilg@sbcglobal.net

Bob Hadley and I are considering the following. We would like to get extension plates and toolpost risers machined so that we can turn pieces larger than 20" on our 3520a's. See the picture of the extension plate that Bob designed on Yahoo:
http://f2.pg.photos.yahoo.com/ph/bphadley@pacbell.net/album?.tok=phOTtXBBUD1es2Q4&.dir=/2a5b&.src=ph

I might be interested.

Clem
 
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This is interesting to me, too. However, I can't help but think about how I turn large pieces, and how I would miss my tailstock in this scenario. There is a period of time, for me at least, when I'm truing up or roughing out a large blank that requires tailstock support. Even with the meatiest of faceplates, I'm going to be uncomfortable spinning up a 20"+ blank with no tailstock support.

Additionally - hollowing the interior of a huge blank also requires tailstock for a good portion of it, retruing and then initial hollowing - it is SO easy to blow a big blank out of a tenon chuck.

Aren't you guys concerned about this?
 
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Bob and I dropped this idea after we found out that the metal costs would be too high. And I tend to agree with Mike that big pieces need to be supported by the tailstock for initial roughout. Anyhow, we are not pursuing this idea anymore.
 
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Thanks for the update.

How about spacers under the headstock, tailstock and banjo to increase size?

Is this doable or are the mechanics too much for the lathe?

Clem
 
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Clem - I think that is a good potential idea. However when I researched this whole situation, one of the problems is the potential to warp the ways (bed). If one puts too much leverage on the ways they will not take the stress.

Probably the easiest solution is to get a larger lathe or a lathe like a Stubby. Since this topic originally came up, I haven't run into any massive pieces of wood I wanted to render into a single turned piece. But I have rendered some 20" hexagonal pieces into 19" bowls and platters. A 19" bowl is pretty big.

Here are 2 biguns.
1st is a 110 pound oak log....which became a giant mushroom
2nd is a 19" hickory roughout
 

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This is in response to Clem's note.
I purchased (used) a General 260 lathe about 10+ years ago and it had riser blocks (which General made) added so the lathe was capable of turning 20" over the bed of the lathe. This was before General made a 20" lathe. The riser blocks fit under the headstock and the tail stock. It worked well with no problems for me.
Hugh
 
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Jeff and Hugh...

Jeff, I think that I will be very satisfied with a 20 inch lathe for quite a while. Those 100 plus pound pieces should keep me on my toes and I won't have to be thinking bigger. Is that your daughter with the roughout? Also, is that the stock tool rest or one that you made?

Hugh, It's interesting that General would provide those spacers to "enlarge" their lathe. Thanks for sharing.
Clem
 
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Clem,

You just earned some major extra brownie points. No, that's not my daughter, that's Theresa...significant other. She really enjoyed that compliment from you!

Those are custom toolrests that I made. There was some discussion about them under some of the pics I posted:
here

Note there are several photos in my gallery about the toolrests. I'll show 'em to you next week during your visit. My welding may not be pretty, but none of those rests have bent or cracked....and believe me, I've tried :cool2:
 
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Toolrests

Jeff,

I have a daughter named Theresa, spelled the same way! They look about the same age :)

What type of metal did you use? It looks like stainless. I need to use all of the metal working equipment that I have collected and put them to good use fabricating turning accesssories.

I'm really looking forward to getting together with you for an orientation on the 3520 and also to get a close-up look at your neat rests. I'll e-mail you early in the week as soon as my schedule firms up.


Clem
 
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I described the creation of the toolrests in this
thread

We can discuss it more next weekend. The metal is standard 1040 steel. After extended use, they have dulled a bit, but a couple of the rests which are less frequently used are still pretty shiny. I wirebuffed all of 'em.
 
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Tool Rests

Jeff,

After I posted the question I went back to the thread you listed and read your explanation. My second reading made things clearer.

A picture IS worth a lot of words :)

Clem
 
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Thanks Clem. I just spent some time and reformatted all the info and it will appear as a tip in the "How-To's and Tips" subforum. This question has come up a few times.
 
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Low profile banjo for 3520

Jeff,

I am new to all this, and to my 3520, and can't vouch for the applicability of the following to your issue, but I ran across this source for a redesigned low profile banjo that purportedly adds 2" to the maximum possible turning and would still allow use of the tail stock. It also has an interesting design for a fixed outboard turning rest.

http://www.customwooddesign.com/woodturningaccessories-2.html

Regards,

Jerry Hall
 
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Hi Jerry. The low profile banjo unfortunately does not allow for wider pieces to be turned. The main limitation of most lathes is the distance from the spindle to the ways (the bed). On the PM3520 it is about 10", which results in a 20" maximum diameter.

I've turned some 20" hexagonal shaped stock down to about 19". A 19" bowl/platter is pretty big! There have been a few pieces which could have been bigger, but one can't have everything! Thanks for the potential tip.
 
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