3520b bed extension issues

[Ben Pierce]

Hi everyone,

I've been using the bed extension for about a year and a half now, and I have enough space so I just leave it attached all the time. It allows me to get the tailstock waaay out of the way when I'm not using it without having to remove it from the lathe. The trouble is, the ways on the extension simply don't match those on the lathe. It is extremely difficult to slide the tailstock across the joint between the extension and the lathe bed. Loosening the clamp nut underneath the tail stock helps but only to an extent--if it's loosened too much then the clamp can't be tightened sufficiently, as the handle runs into the lathe bed. I have tried adjusting the alignment of the extension this way and that, waxing everything, oiling everything, even a bit of sanding the bottom side of the ways where the round clamp rides, and it still takes a forceful push to get the tail stock to travel across the joint.

Anyone have any experience with this? It seems like a pretty substantial manufacturing defect.

Ben

[John K Jordan]

Hi everyone,

I've been using the bed extension for about a year and a half now, and I have enough space so I just leave it attached all the time. It allows me to get the tailstock waaay out of the way when I'm not using it without having to remove it from the lathe. The trouble is, the ways on the extension simply don't match those on the lathe. It is extremely difficult to slide the tailstock across the joint between the extension and the lathe bed. Loosening the clamp nut underneath the tail stock helps but only to an extent--if it's loosened too much then the clamp can't be tightened sufficiently, as the handle runs into the lathe bed. I have tried adjusting the alignment of the extension this way and that, waxing everything, oiling everything, even a bit of sanding the bottom side of the ways where the round clamp rides, and it still takes a forceful push to get the tail stock to travel across the joint.

Anyone have any experience with this? It seems like a pretty substantial manufacturing defect.

Ben


I'm curious, what exactly is the misalignment? Not parallel in both axes, twist, vertical or horizontal offset, irregularities? (Check with a steel straightedge?) Does the bottom of the tailstock have sharp edges (my banjo did, making it hard to slide at times) When I installed my bed extension I used a 2x4 to hold it into place, cut a block to align the slots in the bed, then clamped something flat on top to align the surface before tightening the bolts. Tailstock slides easily.

JKJ

[Mark Greenbaum]

On the bed extension my co-worker made for me (wooden structure), I went to slide the tailstock onto it and it would not go, even though the ways were level and same thickness. I discovered that as a double safety measure, Grizzly had the hanging bolt long enough that it need the swung out of the way to clear the bridge in the leg. Check the clamping bolt to make sure it isn't hitting the leg casting as it travels across the joint.

[Jim Underwood]

My question is similar to John's. How is it mis-aligned? ARe the thicknesses different? Is the space between ways different? On my new Stratos, I had todrill the mounting holes oversize to get it anywhere close to flush. The thickness of the ways was about .010" different, as was the space between the ways. I clamped some flat stock to the top of the ways, split the difference on the space between teh ways, and then tightened the bolts. Needless to say, it's not the most smooth transition, but I don't have too much difficulty.

[David Delo]

My procedure was to put the bolts in first but don't tighten them down fully and then slide the tailstock back over the joint so the clamp block was 1/2 on the bed and 1/2 on the extension and then engage the lever and then fully tighten the bolts. Sounds as if you don't have the insides of the ways matched up perfectly.

Takes a little wiggling around if your doing it by yourself. Helpful if you have an extra set of hands.

[Ben Pierce]

Thanks guys. I will have a close look this weekend and maybe take a few photos.

[John K Jordan]

... slide the tailstock back over the joint so the clamp block was 1/2 on the bed and 1/2 on the extension and then engage the lever...

David, your post reminded me of what I used to clamp the extension flush with the bed! I'm getting feeble-minded and forgetful in my old age. I aligned the slot first with the wood block, partially tightened the bolts, slid the tailstock into place to overlap, loosened the bolts and clamped the tailstock, then tightened the bolts. Perfect alignment horizontally and vertically.

JKJ

[David Delo]

Ben,

Here's a couple pics for reference. You'll notice the "insides" align perfectly left to right and top to bottom between the main body and the extension. The extension casting does not line up perfectly to the outside profile of the main body. Don't know how much variation there is in other castings but this is how mine is. Guess I'd be asking to much to have the profiles match but PM not putting the painted black stripe on it does bother me. I parked my extension in the lower position when I first got it 3 years ago but find the upper position much more useful. Rarely do I need to take the tailstock off anymore. Hope you don't have a mis-machined part but once you get this straighten out I think you really like your setup.
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[Mike Goetzke]

Ben,

Guess I'd be asking to much to have the profiles match but PM not putting the painted black stripe on it does bother me.

I had issues with alignment till I used the tail stock to align them as David posted.

David - I too was disappointed to see no black stripes on the extension but also the paint color doesn't match perfectly either.


Mike

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[John K Jordan]

I had issues with alignment till I used the tail stock to align them as David posted.
David - I too was disappointed to see no black stripes on the extension but also the paint color doesn't match perfectly either.


Yikes, you guys must have gotten the no-stripe extension perhaps made for the 3520b lathes like the one I have. The color doesn't match but I never look at it.

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JKJ

[Dane Riley]

My tailstock slides OK, but next time I take it off I will drill out one of the mounting holes which will allow a few thousandths better alignment. I don't remove it very often, even though I have an electric hoist. Don't know how I would remove or install it without one. Also makes removing the tailstock easy.

The outside aligns somewhat better than David's, but still far from perfect. The inside of the ways are what matters.

[Bob Bergstrom]

I had issues with alignment till I used the tail stock to align them as David posted.

David - I too was disappointed to see no black stripes on the extension but also the paint color doesn't match perfectly either.


Mike

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If if you take a length of 2 x 4, with the 4" side facing the floor, and slide it into the opening under the ways leaving a couple feet sticking out. Slide the extension onto the 2 x 4 till the two ways meet. Put the bolts in, pull the 2 x 4 out slide the tailstock over the joint and clamp it down. Tighten the bolts. The two by four trick can be helpful in assembly of the lathe, and moving one also. It does provide a good handle for pushing, pulling, or lifting the lathe.

[david privett]

if you can get it PERFECT in alignment I would suggest drilling in two alignment pins to make connection more easily repeatable for bolting the two halves together .

[Josh Bowman]

Ben,
The mounting holes are bigger than the bolts, or should be to allow alignment. I simple got it close, snugged up the bolts and moved the tailstock over the joint and tightened it real tight. That should move the extension into alignment, or at least it did for me. It might take a time or two, but it should line up.

[Thomas Canfield]

I have a bed extension also that I mounted when I got my lathe about 9 years back and had the alignment perfect then. When I moved 5 years back, it took about 30 minutes to align the extension. 6 months back I lowered the extension and then remounted it up and it took over an hour to get the alignment perfect. It was a trial and error with the final alignment and using some straight edges and bumping the snugged bed before tightening in final position. I do plan to lower it again sometime to turn a large (30"??) piece just once. It is worth getting the alignment right.

[Jon Nuckles]

Mine slides across the joint easily, though there is a bit of a "click" when it crosses. I've attached it and taken it off 2 or 3 times in the upper position in the couple of years that I've had the extension. It has never taken more than a couple of minutes using the tailstock overlap method to align it. I wonder if there is some variance in Powermatic's casting and machining that is making some extensions trickier than others.

[Ben Pierce]

I've examined the joint closely several times, and I just can't seem to see what is causing the jam on mine. I have taken great care to align the tables as close to flush as possible, using the slack in the fastener holes for fine tuning. I can shove the tail stock across the joint with some force, and the click that Jon mentioned. I have filed the rabbets in the tail stock, as it appeared as if the leading edge might be catching on the joint. That might have helped a bit but I don't want to do any more filing or I will have play in the tail stock.

This is not a new lathe or setup for me. I've had it set up like this for a couple of years and this issue is wearing on me. As previous posters have mentioned, the paint on the extension doesn't match and the parts are obviously not manufactured a) in the same place, or b) with the proper measurements and tolerances. New buyers beware... I am happy with the machine otherwise but this is a substantial issue.

[John K Jordan]

...I have taken great care to align the tables as close to flush as possible, using the slack in the fastener holes for fine tuning. I can shove the tail stock across the joint with some force, and the click that Jon mentioned. ...

It is not clear from this if you actually used the tailstock itself as a clamp to make the upper surface absolutely flush. Are you saying you did this and still get a click? Your comment about filing a rabbet (you mean bevel?) indicates the alignment is still not perfect.

If you hold a straight edge across the joint with a flashlight behind it you should not be able to see any light between the straight edge and the ways. If you can see an even sliver of light on one side then the alignment is not perfect. If there is light under the straightedge reveals a low or high (as if the extension is tilted up or down and not parallel with the bed) then remove the extension and check for a burr or debris on one of the mating surfaces that prevents alignment.

I looked at mine yesterday and the outside shapes of the lathe and extension, while both curved, are no where near the same. This doesn't affect the function.

JKJ

[Bob Bergstrom]

Could there be something on the underside of the ways catching. With a good light watch from underneath as you slide the tail stock across the joint.

[Brice Rogers]

You have got a lot of good advice. If those suggestions haven't lead you to the problem, then read the following:

This cannot (or should not) be rocket science. Just take a block of wood or steel, etc. - - say 1 x 1 x 6" and run it across the joint (in both directions) at all of the important intersections: (1) top rear way, (2) top front way, (3) inside of way (rear), (4) inside of front way, (5) bottom rear way, and (6) bottom front way. All of these intersections should be in the same plane. If they aren't in the same plane or if you have a burr, you will feel it. If all of these pass, then the only other thing is the "foot" of the tail stock is hitting something. then (7) Remove the foot and try it again.