[How-To] Making a cable hub

[DavidR8]

There are several(usually) gears between the spindle and the lead screw. As long as they run in the same plane, they are only idlers. The only control they offer is changing direction based on an even/odd number. A stepped gear is where two gears are keyed together, say a 60 and a 40. Driving the 60 into the 40 would reduce the output by a small precentage. My mind says 33%, but, like I said, I'm slow tonight. Basically, the same as a drill press, where the smaller the driveing(power) pulley and larger the driven(load) pulley, the slower the spindle runs.
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Right, that makes total sense.
I have a fairly tight range of TPI options in the coarse range:
4
4.5
5
5.5
5.75
6
6.5
One of those has to get me in the ballpark

 

[Bi11Hudson]

The "span" is between 5.0 TPI and 5.5 TPI. All you need is somewhere between those two.
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[extropic]

The pitch of the grooves in the sheave has to be at least equal to the cable diameter. If the groove pitch is less than the cable diameter the cable won't lay in the grooves. 5.5TPI is .1818 pitch, which is smaller than the cable (.1875) you specified. 5.5 TPI won't work. 5 TPI (.200 pitch) is OK.

I'm not familiar with using the described system to drive a table. Is it in common industrial application? What sort of "coating" will the cable have?

 

[extropic]

WHY would you need to change the design of the table drive?

What is the width and thickness of the existing steel tape?

 

[Cooter Brown]

Most importantly, WHY would you need to change the design of the table drive?

The Rack and Pinion needs to be cleaned out all the time.... If to much dirt get in the rack it makes the table jump and causes small steps in the surface finish..... The cable drive is very smooth and can be adjusted easily with a turnbuckle.....

 

[DavidR8]

The pitch of the grooves in the sheave has to be at least equal to the cable diameter. If the groove pitch is less than the cable diameter the cable won't lay in the grooves. 5.5TPI is .1818 pitch, which is smaller than the cable (.1875) you specified. 5.5 TPI won't work. 5 TPI (.200 pitch) is OK.

I'm not familiar with using the described system to drive a table. Is it in common industrial application? What sort of "coating" will the cable have?

Thanks I'm leaning toward 5 TPI
Some Harig grinders use a cable to move the table.
The photo in the opening post is a screen capture of a Sharp SG-618 grinder.

I have an email into Parker Majestic to see if they still supply the steel tapes.
If they don't then I have to find a different way to drive the table. The tape is only .001 thick. The thinnest steel tape I can find is .018.
I might also try a tape measure tape.

Edit: The tape broke right at the attachment to the hub. I've lost about an inch of length. I may have that much adjustment room on the adjusting nut. It will be very close.

 

[extropic]

It's not even Friday the 13th.

Starrett sells shim stock (feeler gage stock) (about .5" wide) by 25' long in .001, .0015, .002., and so on.

Redesigning the table drive and expecting to come out with a better result than the OEM is a steep hill.

Feeler Gage example

 

[DavidR8]

It's not even Friday the 13th.

Starrett sells shim stock (about .5" wide) by 25' long in .001, .0015, .002., and so on.

Redesigning the table drive and expecting to come out with a better result than the OEM is a steep hill.

I have been putting Google through the paces tonight and I could not find that!!!
THANK YOU!!!

 

[Bi11Hudson]

The pitch of the grooves in the sheave has to be at least equal to the cable diameter. If the groove pitch is less than the cable diameter the cable won't lay in the grooves. 5.5TPI is .1818 pitch, which is smaller than the cable (.1875) you specified. 5.5 TPI won't work. 5 TPI (.200 pitch) is OK.

The whole point is to get the cable to lay flat and close together. Calling for a "theoretical" pitch of 5.25 TPI when using the lathe in threading mode. If there is space between the wraps in a single layer, the cable will tend toward falling between the wraps. This will not be consistant, causing slack to come and go in the cable. As with all machine tools, inconsistant feed leaves tool marks.

BTW, the flat band system is known in the computer field as a "taut band". It is known there to maintain tolerances in microns, depending on the size of the drums. I cannot speculate why it was used on such a large machine. Nor the conversion that David is considering.

Starrett sells shim stock (about .5" wide) by 25' long in .001, .0015, .002., and so on.
Redesigning the table drive and expecting to come out with a better result than the OEM is a steep hill.

Shim stock would need tempering, at a minimum. A spring steel such as banding strap would be more suitable. But I've never encountered strap so thin as what he needs.
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[DavidR8]

The whole point is to get the cable to lay flat and close together. Calling for a "theoretical" pitch of 5.25 TPI when using the lathe in threading mode. If there is space between the wraps in a single layer, the cable will tend toward falling between the wraps. This will not be consistant, causing slack to come and go in the cable. As with all machine tools, inconsistant feed leaves tool marks.

BTW, the flat band system is known in the computer field as a "taut band". It is known there to maintain tolerances in microns, depending on the size of the drums. I cannot speculate why it was used on such a large machine. Nor the conversion that David is considering.


Shim stock would need tempering, at a minimum. A spring steel such as banding strap would be more suitable. But I've never encountered strap so thin as what he needs.
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As far as my research has shown, there are a number of grinders that use a continuous cable to move the table. Harigs are one that I know of.
I'm only considering converting to cable if I exhaust all options to return it to original. It's a 1963 grinder and I'm not confident that I can get new bands for it.