For anyone interested I called Powermatic the other day and found you can use the 3520A bed extension on the B's but, the ways are a little thicker but, it should not matter that much. I have found the A extentions are cheaper to buy at Southern Tools.
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3520B bed extension
- Thread starter windsors
- Start date
john lucas
AAW Forum Expert
I'm going to figure out how to drill the holes in my 3520A and lower the bed. Then I have to figure out how to build a riser block for my tailstock. I need to turn a 36" spindle that is 22" in diameter at the bottom. I thought I would mount the bed extension lower and then build a riser block so I could hang the large end of the spindle over the bed extension. I'll have to build a riser for the tool post as well.
john lucas said:
John, using the existing pre-drilled holes for the extension couldn't you attach a plate(3/8 or 1/2 in) and mount the bed extention to the plate? Some sort of spacers w/adjusters between the legs and the plate would allow you to keep the bed ex. in plane with main bed. Just a thought.
john lucas
AAW Forum Expert
Jake That is one option I'm looking at. The 3520A doesn't have exactly the same legs as the B. At first glance it looks like I would have to do some grinding in the legs to get the extension to sit parallel to the bed. It probably wouldn't take much and I can do that with an angle grinder.
If I go with the plate I think I would have to somehow anchor the plate to the legs anyway to make it really solid. I don't think just screwing the plate to the 3 holes near the top would stop enough vibration.
Either way I still have the problem of really accurately drilling the holes. I've been thinking about using the magnets I got with my Moffet lights. I'll make a drill guide that attaches to those. This will keep the drill square. Then the only problem becomes aligning the thing accurately.
If I go with the plate I think I would have to somehow anchor the plate to the legs anyway to make it really solid. I don't think just screwing the plate to the 3 holes near the top would stop enough vibration.
Either way I still have the problem of really accurately drilling the holes. I've been thinking about using the magnets I got with my Moffet lights. I'll make a drill guide that attaches to those. This will keep the drill square. Then the only problem becomes aligning the thing accurately.
John, how about putting a solid plate spacer between the end of the bed and the mounting plate. That would eliminate the grinding on the legs. If you then tack weld the spacer plate and the main plate together and clamp it to the lathe you could use transfer punches to mark the holes that need drilling. By getting the transfer punch marks properly aligned these would then give you a register to mark the holes for the extension. All the drilling could then be done on the drill press including the holes for the bolts for the legs. If you stand the plate off the legs enough you could then use long bolts and bushing spacers or lock nuts to make adjustments to bring it into plane. Or you could borrow some time on a friends Stubby and drilling be d@**&d. 
Good luck either way.
Good luck either way.
john lucas
AAW Forum Expert
Jake If I could get enough commission out of the piece I have to turn I would simply buy a Stubby or Robust and not have to mess with this but then I realize that apparently this is part of what I enjoy about this hobby, being able to modify and play with the tools.
john lucas said:
Truly, I hear that!
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John,
For a 1 time setup you could make riser blocks for both the headstock and tailstock. This should be really easy since nothing has to adjust once you have the head and tailstock lined up. The tailstock side can double as a riser and an extension
2x6 hard maple with some bolts should work.
You can also use some tubular steel or possibly an I-beam on its side.
Lot easier to work with the hard maple.
For the tool rest. I would suggest you make a rest with a long shaft post.
You can make a riser by essentially mounting a 2" think maple washer on
the tool rest locking bolt you would need a coupler nut to lengthen the bolt.
This takse away clearance under the turning.
good luck,
Al
For a 1 time setup you could make riser blocks for both the headstock and tailstock. This should be really easy since nothing has to adjust once you have the head and tailstock lined up. The tailstock side can double as a riser and an extension
2x6 hard maple with some bolts should work.
You can also use some tubular steel or possibly an I-beam on its side.
Lot easier to work with the hard maple.
For the tool rest. I would suggest you make a rest with a long shaft post.
You can make a riser by essentially mounting a 2" think maple washer on
the tool rest locking bolt you would need a coupler nut to lengthen the bolt.
This takse away clearance under the turning.
good luck,
Al
Last edited:
john lucas
AAW Forum Expert
Al I have some MDF on hand just in case I need to go the riser block thing. since I have a metal lathe I'll just make an extension similar to the one Powermatic sells except mine will be solid steel instead of cast.
I'll send you a picture of my set up. 3520A. 18" extension mounted 8" lower off end with 3/4" steel plate. 8" Tool rest riser made from 2" steel round stock . Works very well. Now if I can only get it back from my buddy that I lent it to 3 months ago...........