TRAV-A-DIAL bearing preload

Hello, I purchased a trav a dial 6a on ebay very cheap knowing I was probably throwing my money away. I examined it out of the box and saw the knob and track wheel had some axial and radial play. I figures the bearing is shot so I thought no harm in opening it up to tinker. I removed the factory epoxy from the screw holes and opened the unit. I was very surprised at the internal condition. All the bearings were intact and nice and shiny and looked new. Inside of case has very few chips and swarf. The bevel seats on the track wheel shaft are not worn yet when the 2 halves are together that shaft does not make contact with both bearings and therefore the shaft play is introduced.
The top bearing under the knob is pressed into the casting has no adjustment. However the bottom bearing has 2 spring washers between the outer race and the casting which look like they are there to apply preload and take out any wobble in the shaft. That bottom bearing does not move axially and looks like the bearing housing is epoxied to the case. I removed as much epoxy as I could see and I placed the casting in an arbor press and using a round pin about the same diameter as the bearing housing, I tried to press the bearing loose in the casting so the spring washers would apply pressure to the bearing against the shaft. It doesn't want to budge with moderate pressure. I'm afraid to put too much force and ruin it entirely. I also am concerned about heating it and causing damage. Has anyone successfully freed up the bearing? Any other ideas?

Thanks,

Mike.

It has been decades since I have been inside one, there is a hole in the side of the twin wheels, that you twist the wheels alittle and put a pin in to hold.
That takes up the play with the spring load, then at a point re assembling, the pin is removed. That is how the play is removed.
Been a long time hope that helps.

If the contact wheel is loose, I have seen that once, may not be fixable without new parts, and new parts no longer made.
I use these and have several, I still find them faster to use then a DRO,

Hey donie thanks for the reply,
However what you're mentioning in loading the spring will only remove backlash at the needle. That in no way adds preload to the bearing. I have to be able to reposition the bearing in order to apply preload to the shaft the same way a spindle take up nut would provide preload to a lathe spindle. However this bearing seems to be glued in place with no obvious way of adjustment other than Breaking the glue seal which I'm afraid to do. I could be ruining a perfectly good salvageable trav a dial if I go at it blind

I remember the bearings, I remember them being a bearing like a cup in a bicycle, or angular contact. Perhaps you can take up the slop by using shims to load the bearings, or loading them axially.
I bought one recently on ebay with the complete mount for $325, so they are not cheap, but not the $700 they were in the !980s,
The only problems I have had with used ones is they get contaminated and need cleaning.
Years ago, there were many users of the device, but now it appears to be a few die hards.

yes its angular contact bearing in a cup race.
the only shim that could work if they exist is a hardened cone shaped shim to match the profile of the wheel shaft.
Getting behind the bearing cage will lift the cage off of the cup and wont keep concentric.

MikeMM said:

yes its angular contact bearing in a cup race.
the only shim that could work if they exist is a hardened cone shaped shim to match the profile of the wheel shaft.
Getting behind the bearing cage will lift the cage off of the cup and wont keep concentric.View attachment 312057View attachment 312058

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you have to get behind the CUP, not just the cage or spider obviously. no way a conical shim is the answer. you were on the right track trying to free the cup or outer race. I seriously doubt it would have been epoxied in, I bet its just hardened grease or such. try an overnight/24hr solvent soak, maybe a heat gun to 160F or so after that. tap gently around the edge with a delrin rod. once loosened, gently pry up with a chopstick or other hardwood "prybar". looks really clean otherwise, so its worth a bit of work to get it right. good luck!

cyanidekid said:

you have to get behind the CUP, not just the cage or spider obviously. no way a conical shim is the answer. you were on the right track trying to free the cup or outer race. I seriously doubt it would have been epoxied in, I bet its just hardened grease or such. try an overnight/24hr solvent soak, maybe a heat gun to 160F or so after that. tap gently around the edge with a delrin rod. once loosened, gently pry up with a chopstick or other hardwood "prybar". looks really clean otherwise, so its worth a bit of work to get it right. good luck!

Click to expand...

Got it free. My heat gun broke and I never replaced it so I used my Mapp torch.
I heated the casing around the bearing cup from the back side of the cover moving in circles for a few seconds. Did it several times to where the casing started to get to hot to handle barehanded. Placed it in the arbor press and with a socket approximately the same diameter of the bearing I was able to press out the bearing with just some light pressure.

I cleaned off the bearing and casing and now the bearing moves freely up and down in the bore which allows the spring washer to have the bearing put preload on the shaft.

I assembled just to test it and the wheel has no axial or radial play and turns freely. Going to give it a good cleaning. I freed up the remaining 2 bearings as well. They are all epoxied in place at the factory as well as the 6 screws that hold the unit together. The material used is like a transformer potting compound, I don't know why the bearings are glued over as that removes any preload as parts wear and clearances cant be adjusted by the spring washers. I don't know if I should re epoxy the bearings and screws. Anyone have any insight as why the were glued in place? I cant believe they would sacrifice bearing tension for sealing out dirt.