• Scam Alert. Members are reminded to NOT send money to buy anything. Don't buy things remote and have it shipped - go get it yourself, pay in person, and take your equipment with you. Scammers have burned people on this forum. Urgency, secrecy, excuses, selling for friend, newish members, FUD, are RED FLAGS. A video conference call is not adequate assurance. Face to face interactions are required. Please report suspicions to the forum admins. Stay Safe - anyone can get scammed.

Ben lathe bed

T

Tjscharp

Member
I have a 1960 Storebro Bruks lathe 16x60.
I have only 4 leveling feet and there appears to a bend or an arc in the middle of the bed where no jack screws are present. I have a coolant tray which blocks access to the floor and am struggling to figure out the best way to raise the bed at the precise location of the bend.
 
I guess I can't post pictures for now my apologies.
I have a dial mounted on my carriage, extended towards the chuck. About 2 feet out from the chuck the bed angles upward .020" of an inch over those two feet. At the tailstock end of the machine it is perfectly flat (within .001" anyways)
 
IMG_20200226_184710.jpg
 
I’m just going to throw this out there, but I wonder if it’s not due to wear in front of the chuck as opposed to actual sag in the bed itself. That’s not an overly long lathe.

I know guys that run an old Southbend in their shop that I swear hasn’t seen oil in 35 years. There’s nearly an eighth of an inch worn off right in the sweet spot about 8” in front of the chuck. It’s really amazing.

-frank
 
Wear is ... a worn low spot next to the chuck. In extreme cases the saddle rides on the top of the V.

How are you exactly indicating this? Usually either you check against known surface - I have a space between surfaces that see wear and I can indicate that or via a precision bar in chuck (bar will also have a drop). Is the non wear surface about 1/2" wide thing I see indicator touching?

If you move towards the chuck indicator will show a rise. My lathe if I remember correctly is 0.012

For 1" part that wear over a longer distance from the chuck will cause a bit more then 0.0002 error. But for 1/2" it doubles and for 1/4" its 0.0008 multiply by 2x for your lathe. This is for turning. Over 2ft.
 
If the bed is worn by something like 0.020", the only feasible solution is to disassemble the lathe and have the bed ground flat. Ideally, it should then be scraped to take it to the next level. The bottom of the saddle will probably need to be ground, as well.

Grinding, however, can then create problems with the alignment of the saddle with the feed screw(s). Applying Turcite (sp?) to the saddle may help to compensate for the ground-off material. This work is complicated as the cross-feed needs to be very precisely at 90 degrees to the spindle axis.

All-in-all, an expensive and time-consuming process. On YouTube, Keith Rucker's Vintage Machinery channel had a long video series on his rebuilding of a Monarch lathe. From here, it sounds like your machine needs much of the same treatment to bring it back to factory spec (or better). Only you can judge how much you want to invest in the machine.

Craig
 
One has to point out that the loss of accuracy is over 2ft long turned piece of metal and the loss is minimal. The actual loss is far less then the loss created by say not level lathe. Also alignment of lathe components is of far greater importance then say bed wear.

To bring that lathe up to spec of a factory machine would cost few times more then the lathe is currently worth or will be worth after the fix. One has to remember that if the ways are so worn then other parts of the lathe may also show a lot of wear.

To feel better you can read about work done on a clunker lathe that probably has far more wear then your lathe. As long as the wear is gradual i.e. there are no up and down hills you can account for it if you wish and produce same quality parts as if you had brand new lathe.

From pictures your lathe looks 10x better then my big clunker.
 
There is a gantry grinder in Alberta that does this. For a 60" bed, already disassembled and ready to go, it is about 2800$, so the lathe has to be worth redeeming.

However, it is perfectly fine to use a lathe with a worn bed by mapping the low spots and compensating. I did that with the lathe in high school, and the shop teacher couldn't figure out why my turning was far better than the average. He even used one of my projects to loudly proclaim that the bed was straight! ( I never told him - he was a rite b****rd).

[update] sorry Tom, for the duplication. we answered at the same time!
 
I had the same question about how you are measuring this. Do you mean both the front & rear ways are parallel but rising together 0.020" near the head stock end vs the tail stock? For example are you placing an accurate level along the bed ways starting at the TS end in increments towards HS end & both side are showing the same progressive tilt?

As as opposed to lathe bed 'twist' where an indicator placed on the front rail might see a different reading on the rear rail. This would be better evaluated with accurate level laying across the ways & same deal, working from on end to the other. This wold be the typical leveling pad screw jacking adjustment. (You might have wear or other issues but just trying to begin at the beginning).
 
I can't say the .020" is truly an accurate number, as I was indicating off of the carriage onto a coolant land which in theory receives no wear. Obviously the carriage would also ride up some of the incline and would The dial would not fully capture the true incline of the bed. The problem is shown somewhat in this picture. I cut a center a brought the tailstock up to it. I don't know exactly how much higher the head stock is, but it exceeds the .030" limit of a floating reamer holder that I have. Bear in mind that when manufactured, the tailstock was bored out using a fixture held in the spindle in the machine.
IMG_20200201_141859.jpg

PeterT said:
I had the same question about how you are measuring this. Do you mean both the front & rear ways are parallel but rising together 0.020" near the head stock end vs the tail stock? For example are you placing an accurate level along the bed ways starting at the TS end in increments towards HS end & both side are showing the same progressive tilt?

As as opposed to lathe bed 'twist' where an indicator placed on the front rail might see a different reading on the rear rail. This would be better evaluated with accurate level laying across the ways & same deal, working from on end to the other. This wold be the typical leveling pad screw jacking adjustment. (You might have wear or other issues but just trying to begin at the beginning).
Click to expand...


Firstly thank you for taking the time to respond everyone.
The bed of the machine is 60" long. I have mounted a dial indicator on the carriage of the machine, starting from the furthest point towards the tailstock end of the lathe. As I go towards the headstock, I get about 16" from the chuck, and the bed begins to rise, not fall away as you would expect with a worn out bed scenario. For the large majority of the bed, the indication is within .001" until I hit that last 16" mark.

I'm in a garage, where the floor naturally slopes towards the door, I have only leveled to remove bed twist, not levelled length wise, so I can't really use my precision level to help diagnose at the moment.
 
Hmmm..the plot thicknens. Any chance the head stock was ever removed from the bed and maybe not set back on the same way? ie. a scenario where the beds could be perfectly fine but you are trying to make sense of it relative to HS spindle center? It looks like such a solid machine, one would thing the bed would stay pretty rigid under its own weight even if it was slung & lifted in a 'non-typical' manner. Can you somehow position a precision level to align to the spindle axis? ie. is it pointing up or down relative to bed axis?

Pardon my crude sketch for the next bit. Blue rails are theoretical flat. Green arrow is direction of distortion. Black bar is level positions.

Bottom sketch. So by bed twist I mean place an accurate level laterally across the ways at various positions from TS to HS to map any angle change of one rail relative to the other. If that has been done and checks out, then the next thing you could do is...

Upper sketch. If both rails are essentially parallel but bending up near the HS, you should be able to pick this up with increasing angular displacement of the level as you compare readings from TS to HS. Even if your bed is on a slope (from HS to TS) the level should say the same thing. If your precision level is out of range because of slope (alone), maybe you could rig up a small piece of feeler gauge or something just so you can read the bubble or dial. We aren't looking for the number so much as the relative reading along the bed.
 

Attachments

  • SNAG-2-27-2020 0001.jpg
    SNAG-2-27-2020 0001.jpg
    23 KB · Views: 0
  • SNAG-2-27-2020 0002.jpg
    SNAG-2-27-2020 0002.jpg
    22.3 KB · Views: 0
Can you take a picture of the front of the lathe that shows the whole machine so we could see the levelling arrangement (or lack thereof). If the lathe is sitting on top of a cabinet style base, the 4 levelling feet are only there to level the base and not the lathe bed itself. There may be mounting bolts to the cabinet that can be adjusted to take out any twist / bends. My SM 1340 is set-up that way.

How about removing the tail stock and then move the carriage all the way to the foot of the lathe. Remount the TS between the carriage and the chuck. Attach an indicator to the TS (somewhere solid) and then slide the TS along the bed. Take measurements to see if you get the same behaviour as when the indicator was mounted to the carriage. If your numbers now are reasonable (+/- 0.001 say), then your carriage ways are worn. If the readings match what you have before, the lathe bed is most likely bent. The reason for using the TS: its ways are likely not worn out.
 
Using the carriage or tailstock to measure for wear on the bed is possibly confusing the issue(s). If the wear is localized, both the carriage and tailstocks could be 'pitching forward' when they enter the worn section. Etc.

Why not use a straight edge to directly check the straightness of the bed [1]? Given the big misalignment between the centers, I would guess that deviations should be easy to see.

BTW, do you know anything about the history of the machine? If it was used in a production environment doing the same operation repeatedly, virtually all the wear could be localized to a pretty small section of the bed.

I think wear just seems to be a more likely answer rather than the bed being bent. The link Tom Kitta supplied suggests that the ways were made of hardened steel. It is hard to imagine them sagging--especially to the magnitude shown. Unless, of course, some previous user was slamming down 1,000 pound loads directly onto the bed?!?

Craig

[1] Lee Valley has an inexpensive line of straightedges that would be accurate enough for this job:

https://www.leevalley.com/en-ca/sho...d-measuring/56676-veritas-steel-straightedges
 
Something confuses me,

The lathe bed rises about 0.020" as you get closer to the head stock but your last picture shows a tail stock about 0.050" low?

I would be tempted to pull off the head stock and other items and put a straight edge across the whole bed and check with feeler gauges to see what the dipitty do da* really is. Maybe the head stock is shimmed up for some reason? Not sitting on the ways properly? Maybe there are leveling screws that are out of adjustment? Is the head stock parallel to the bed (as in it is pointing straight and not off into space?

*Note: Dipitty do da is a highly technical term that can also be used in singing children's songs by substituting a letter Z for the leading D
 
You can move the saddle all the way to the tail-stock as far as it goes. Then place your indicator directly on the ways. indicate the original non wear oil slide-way. See how much it changes access whole length of the bed.

The huge difference between tail-stock and the head-stock does not steam just from 0.02 wear. There can be shimming issue as well somewhere or something else.
 
You must log in or register to reply here.
Back
Top