I modified an existing lathe carriage locking mechanism to ensure there would be enough clearance for installing a future DRO magnetic scale (a digital read-out system made by DRO PROS) on the lathe cross slide. Unfortunately, there is very little room in between the existing carriage clamping nut and where I plan to install a DRO magnetic scale on the cross slide. There would be no room to lock the nut with a box wrench even though the future magnetic scale will be only 10 mm thick. Moving the carriage clamping assembly farther away from the cross slide is not an easy option and I did not want to mount the magnetic scale on the other side of the cross slide nearest to the chuck.
My solution was to fabricate a new locking clamp with an internally threaded hole positioned at an offset from the clamp’s central axis and providing the required clearance to the cross slide. The new design also includes a handle for locking the carriage and eliminates the need for a separate wrench. In practice the carriage can be locked with less than 30 degree angular movement of the handle and there is an internal O-ring providing enough resistance to keep the handle from moving when unlocked. Now the gap between the new locking clamp edge and the cross slide measures 12 mm and will easily accommodate the future 10 mm thick DRO magnetic scale and ensures no interference.
The photos show various stages of machining the new lathe carriage clamping nut. The body of the clamp is 0.875” dia. 12L14 steel rod with M10x1.5 internal thread and the clamp handle is 0.25” dia. 303 stainless steel rod and has M6x1 threaded end. It was necessary to add an O-ring (see photo) for preventing the existing carriage locking bolt from slipping down and into the lathe carriage mechanism when adjusting the new carriage lock. Adjustments were made by removing a few thousandths of material from the bottom of the carriage clamp in order to position the clamping lever parallel to the lathe ways. An added benefit of the O-ring is providing turning resistance while the lever is in the unlocked position so it remains out of the way as the tailstock is moved toward the headstock.
Last edited by Paul Jones; 09-07-2015 at 11:41 AM.
Paul Jones (04-20-2015)
I made a minor improvement to this lathe carriage locking clamp by adding a stop pin. Now I don't have to worry about the tailstock crashing into the end of the lathe carriage locking handle.
I added a vertical limit pin to prevent the carriage locking lever from getting in the way whenever the tailstock is moved forward into the lathe saddle area. The pin is 0.25 dia. T-303 stainless steel, extends 1.125" above the lathe carriage saddle, and threaded 10-32 x 0.25. I drilled the lathe carriage free-hand and bottom taped 10-32 x 0.313 deep (shallow enough to avoid the saddle lubrication channels above the ways).
Last edited by Paul Jones; 01-12-2016 at 08:22 PM.
I have a similar carriage lock arrangement on my lathe and, as you did, added a handled nut when I tired of using a wrench. Of course there's nothing wrong with your method, Paul, but future readers may appreciate hearing about an alternate approach.
Over the years I've come up with a scheme for locating the handle in the preferred position when locked. This scheme doesn't require trimming the nut repeatedly. I either make the nut from hex stock or from round stock with two small wrench flats. The nut is installed and tightened with a wrench then the proper location of the handle is marked on the nut. Nut is then removed and drilled and tapped for the handle. The nut is reinstalled without the handle and the handle is then threaded into place with a drop of the blue, removable Loctite to hold it in place.
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Paul Jones (01-12-2016)
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