Tailstock on Jet 1236 rocks

[Alex Ku]

My tailstock has a "sliding problem" when clamped
I was inspecting it today and found that when it's not clamped tailstock slightly rocks on bed ways. It means that tailstock bottom is not flat.
This is definetly a factor contributing to sliding.
I am planning to grind tailstock bottom flat on my surface grinder.

Is "rocking tailstock" a common problem on cheaper lathes?

 

[MichaelMouse]

Sounds like someone may have dropped it for you and dented it. Look at the portions that meet the ways for any bulge which might indicate a drop. If so, back where it came from.

If you can't get a replacement under warranty I would try lapping rather than grinding. Stickyback sandpaper on the ways and drag back and forth to seat. Possible that it's just a green casting gone wrong. Seen it on the green-painted stuff.

 

[Joe Greiner]

If it rocks, and rocks about the same, at all locations along the ways, lapping might be successful. If not, the ways may be warped, and lapping won't do much good, until the ways are made flat. But also, how much does it rock? And how much does that throw the center off axis? How perfect do you need? "Perfect enough" is sometimes acceptable; all moving objects need running clearance.

Within a very large margin, you usually get what you pay for, but sometimes you get very lucky.

Joe

 

[john lucas]

Rocking is not good. I would put some chalk on the bed and rub the tailstock back and forth to find the high spot and then remove that. I would be leary of surface grinding unless you only remove the high spots. You don't want to make the tailstock any lower. I would definitely make sure the bed is flat before I do anything to the tailstock.
Most of the time when a tailstock slips it's because the tailstock bottom is not flat or the tailstock locking plate is too small. I have corrected a few tailstock bottoms with very careful use of about 180 grit sandpaper. If the chalk method doesn't work try a magic marker to color the bottom and then rub it on the bed to find the high spots. Be very careful if you glue some sandpaper to the bed. It's too easy to rock the tailstock and create a crowned surface.
Once you get the tailstock so it doesn't rock make yourself a larger locking plate. That has done more to secure tailstocks than anything else I've done.

 

[hockenbery]

center alignment

center alignment is important too!
If you turn long stemmed goblets or pens on a mandrel, close alignment is essential.
For chair legs it really doesn't matter much

Any removal of metal from the tail stock base or resurfacing the ways will change this alignment.
John's suggestion is to remove the least metal possible and you have the least change in alignment.

You can check alignment at your working location make a flat smooth surface on a scrap wood held in a chuck or mounted on a faceplate. put a non rotating center in the tailstock with a point (dead center, safe center, spur drive ect.), clamp the tailstock witht he point close to the wood, turn on the lathe, advance the point slowly into the wood.

ideally this will make a tiny point with misalignment you get a circle.
lock the headstock and look to see where the point hits the circle.
left/ right/up/down

consider what machining will do to you center alignment

center alignment can be adjusted by shimming the tail stock with paper.
you.

happy Turning,
Al

 

[john lucas]

If it rocks because one corner is low or a side is low you can center punch several small dimples. These are like little craters with raised rims. This raises the metal very slightly and then you can sand or file it back down. I've done this to tilt a tailstock where the quill wasn't parallel to the bed.

 

[Ken Grunke]

I don't think it's something you'd expect from Jet, I've seen enough online testimonials of how they back up their products. Although they aren't top-of-the-line machines, I think their quality standards are high enough to avoid this. But if it is a factory defect I'm sure they would replace it if it's still under warranty.

 

[rjones]

Is this a new lathe or one you have had for a time or used you bought.
If it is new talk to jet , they should exchange it. If not try what has been talked about. You might also loosen the bolts on the stand and reset them. I have seen were the bed has tweeked a little from this. I know that sounds far out there but it was what was wrong with a high end brand lathe it has been years ago, when we loosen the bolts and settled the bed on the legs (stand) things lined up and tail stock set flat.

 

[Alex Ku]

Thank you guys for all the advises.

I've bought my Jet lathe used.

The tailstock misalignment(measured with dead centers in tailstock and spindle) is little less than 1/8"
Hopefully it'll go away after rocking is gone.
Surprisingly spindle runout on my lathe is just 0.002"

As for quality of Jet products it seems that it's pretty low.
I've just got a new Jet 12" tool rest. Top was crooked and middle part of the top was almost 1/4" lower than ends.
Nothing that 2 hours on sandpaper taped to a granite slab can't fix though. 🙂

 

[Alex Ku]

Using some markers I found high/low points on tailstock base. Seems than no one ever dropped my tailstock it was just Jet low quality product. Tailstock base was not flat at all. It was finished very roughly and has numerous high spots. After some lapping on bed ways the tailstock is not rocking anymore.

Now my tailstock vertical aligment is dead on but since there is still some horizontal movement of the tailstock on bed ways I can only alight centers when I bring tailstock close to the head.
How do I align my tailstock when it far from the head?
The space between bed ways is not consistent so I don't have a good reference point how much to move tailstock side to side to align it.

Thanks,
Alex

 

[GeorgeH]

Howdy, Alex. Good to hear from another NooB here.
I am shocked 😱 with your description of the problems. I've known of some who have experienced minor problems with their JET lathes but the company has always done a good job of handling complaints/replacements - my Jet was perfect when delivered and all of the accessories I've purchased for it have been excellent quality.
I'm sure you've already done the straight edge tests to identify the area of your used lathe that are either damaged or production errors so I won't go into that. There's a lot of good advice above this post for you to correct that. I would recommend you return the tool rest ASAP and complain loudly about the lack of quality control for that part. Manufacturers often farm out that kind of work to sub-contractors and they need to know how well the products with their name on them are affecting their reputation.

 

[Bill Boehme]

If you are using a scroll chuck at the headstock end, the alignment of the tailstock is important, but you can easily see this by backing off the tailstock live center a bit and see if it is inscribing a small circle rather than being at the exact center of rotation. If you are turning between centers, then exact alignment is not a big issue because you essentially have a universal joint at each end of the turning and the true axis of rotation will be through the points at each end. The farther away that the tailstock is from the headstock, the less significant the alignment issue becomes. If you are turning pens the mandrill presents essentially the same situation as using a scroll chuck since there is a rigid connection at the headstock end which mandates good tailstock alignment. I have found that most lathes have enough lateral play in the tailstock to make adjustments to get it to line up properly. If the lathe has vertical misalignment then you might need to use a "sandpaper milling machine" (sandpaper glued to the ways) to adjust either the headstock or tailstock, whichever is higher.

 

[Joe Greiner]

Thanks for the clear assessment, Billy (boehme), especially with regard to turning between centers. The only time when misalignment would be significant, AFAICT, would be using the bed for eyeball reference on a straight, constant-diameter, piece; a straightedge, taped to the bed at slightly different offsets at each end, would solve that problem. For other shapes, a parallax jig, such as shown here: http://www.delorie.com/wood/tips/parallax-jig.html , could also be offset by different amounts at each end. Both strategies will combine horizontal and vertical deviations into a resultant offset; sort of - the viewing angle also gets into the act. If you need more precision than those provide, a metal lathe might be the better tool.

Joe

 

[Frank Drew]

The tailstock misalignment(measured with dead centers in tailstock and spindle) is little less than 1/8"

That seems like a lot, Alex. Are the centers off vertically, and if so, is the tailstock center higher or lower than the headstock center? If they're misaligned horizontally, does there seem to be a lot of slop in the tailstock's fit between the ways?

 

[Jake Debski]

Alex, please forgive my curiosity here, I have two questions. One where did you purchase the new tool rest that was so poorly cast? I would have been back at the store, or if bought on-line, demanding a replacement. Secondly did you know the person from whom you purchased this machine? This machine may have been terribly abused by the previous owner. No one will hold up the Jet 1236 as a top of the line machine but for the money it is very popular and a lot of fine work has been created on it. The problems you describe seem excessive, to say the least, and a phone call to Jet by the previous owner probably would have gotten most of them resolved. I realize this won't help your present situation, but it does point out the problems one can encounter when purchasing used equipment. Maybe if you belong to a local chapter someone in the membership would be willing to help work out some soloutions with you.