Rd14x40 Bed Twist

[jjtgrinder]

Continued from "Map Errors on Older Lathe".

The RD14X40 has a monster of a stiff bed. Very deep and well bolstered with large cross members.

After some careful comparison with a good precision level (Mitutoyo .0006/12") I have some twist in my
lathe bed. I have not quantified the difference at this point. I am getting a appreciable amount of taper
with the diameter increasing as the distance from the chuck increases (like .005 in 1.5 "). When i put the
level under the chuck(same place each time) and level the lathe across the bed, then move the level to the
tail end, the back side of the bed at the tailstock end is off the scale out of level high. According to good solid
information (and logic) , this can contribute to the tapering problem. After taking the twist out, I will look
at other factors such as spindle alignment (head nod , ect.).

I have "bedded" the lathe to the concrete floor. I am now making some "clamps" to hold the feet in place
when I need to pull down on a lathe foot-pad. The lathe is so stiff that if you shim up on the head-stock
backside feet, the whole back side including the tailstock end will lift. I plan to adjust this very slowly to
achieve level. When I get one completed I will post a photo and report success or failure.

 

[hermetic]

I am watching with interest! Good luck with it! If you need me, shout up.
Phil

 

[Ulma Doctor]

i wish you the best of luck in straightening the twist.

 

[jjtgrinder]

Here's the arrangement to clamp the lathe down. Not a great drawing. Ask questions if you need to.


Sent from my iPhone using Tapatalk

 

[jjtgrinder]

I welded a large 5/8 nut on top of the hole in the "foot". In retrospect, I should have made some "thick washers" and threaded the hole for the 5/8 bolt. I am now having to make some "caps" that the bolt will pass thru to sit over the nut and take the force of the clamp. The head of the nut is not very wide to take any clamping force. The caps are a "slice" off of a 1 1/2" pipe (schd 40) with a washer tack welded to the top. The clamp is a piece of 3/8"X3"x3" angle iron with a notch to slip under the bolt head and press down on the foot of the lathe. This will allow me to "jack up" the lathe foot and lock it down.

See next post - I abandoned this approach.

 

[jjtgrinder]

This is the new arrangement. I decided to cut off the old nuts that were welded on top of the lathe feet. I then made some "jacking Nuts" (JN) with side tabs which are positioned under the lathe feet. The tabs come up beside the feet to prevent the nut from twisting. The feet holes were 5/8' some had to be enlarged slightly. The JN nut is a 1/2" x 2"x 2" mild steel bored
.578 max minor diameter and tapped 5/8 x 18 tpi to yeild a class 2A thread. The "Gold" jacking bolt (5/8" x 18 tpi grade 8) passes through the lathe foot and threads into the JN. ( Always start these by hand with oil on the bolt.) The hold down clamp is a piece of 3" x 3/8" angle iron notched and drilled. The hold down bolt for the clamp is a 5/8' x 11 tpi grade 5 bolt welded to the iron plate. There are washers for spacing. I can shim under the clamp rear foot as needed. I am ready to level the bead head-stock end under the chuck and then make fine adjustments for twist removal at the tail stock end.


Sent from my iPhone using Tapatalk

 

[jjtgrinder]

I am reporting back. This arrangement did enable me to "counter-act" the twist and level the lathe ways near the chuck end and the tailstock end. Get in same plane.
I still have a some taper going on with the "two collar" test-bar test. I suspect there is some "head-nod" or other miss-alignment between the spindle and the ways.
I am going to do some testing and see what shows up.

 

[4GSR]

John,

What measurements are you getting on the two collar test? Are you doing this with the tailstock or without the tailstock engaged with your test bar?

Ken

 

[jjtgrinder]

I mis-placed the numbers, with no tailstock. I will run some new numbers in the near future put them in a spreadsheet and post them. Had a LOT of family activity over the Christmas holidays, no time for serious work.

 

[hermetic]

We are your family now son, get back in yon workshop!!