Tail Stock Ram Alignment

[DavesWimshurst]

Robert,
By testing on drill bit did you mean drill rod? Anyway you should first try testing on the outside of the tailstock barrel. With the barrel fully extended and both the tailstock locked and the barrel locked I get much less than a thou error in the full exposed length of the barrel. The usual allowed error is very slightly high at the nose end of the barrel (the actual test is done on a precision test bar inserted in the Morse taper but I don't have one). Have you checked for embedded chips under the tailstock and between surfaces that allow set over for tapers? Your problem may be just a chuck mounted on a crooked or bent arbor, does the error direction change if you reinsert the chuck rotated about it"s axis by 180 degrees? Perhaps a picture of your test set up would help us.
Dave

 

[Foozer]

Robert,
By testing on drill bit did you mean drill rod? Anyway you should first try testing on the outside of the tailstock barrel. With the barrel fully extended and both the tailstock locked and the barrel locked I get much less than a thou error in the full exposed length of the barrel. The usual allowed error is very slightly high at the nose end of the barrel (the actual test is done on a precision test bar inserted in the Morse taper but I don't have one). Have you checked for embedded chips under the tailstock and between surfaces that allow set over for tapers? Your problem may be just a chuck mounted on a crooked or bent arbor, does the error direction change if you reinsert the chuck rotated about it"s axis by 180 degrees? Perhaps a picture of your test set up would help us.
Dave

You beat me to it. Ran the procedure again as you described. Removed chuck, pulled the ram, and cleaned the hole, pulled all the shims. Restarted at ground zero, inserted a piece of drill rod in place or ram. Now I get virtually no discernible deflection on the indicator. (at least over the three inch range its sticking out from the tail stock) Walked this three inches at a time up the bed till I reached the head stock. Only change occurred at the last 3 inch test and it was a 0.001 thou rise.

So its the ram itself and or the chuck. The drill rod stock fits a lot better than the ram does so making a new ram shouldn't be that hard to do. I dont really like the way the chuck mounts anyway. Just a threaded bit on end of ram, no register, reliance upon the threads to hold concentrically just doesn't sound right.

Process of elimination and I'll find the culprit. Never really was an issue until I started this little rocker engine. When deviation exceeds the size of the part time to get off the pot and fix it.

I'll post what I find as I go along
Thanks

Robert

 

[bearcar1]

Fooz, it certainly sounds to me as if the threaded mandrel or stub that the chuck screws onto and is rammed in the tail stock is the culprit here. As you said, relying strictly on a threaded part with out any register is questionable at best. Have a go at machining something that would be repeatable in setup. Not sure exactly what that might be but it will keep the mind occupied for a bit. ;D

BC1
Jim

 

[Foozer]

nailed it down to the chuck and how its mounted. It just threads onto the end of the ram till it bottoms out inside the chuck. Apparently not the best way.

As the hunk of drill rod used to simulate the ram gave good results, i then checked the ram itself. It gave a little bubble near its center around 2 thou but settled with same reading on each end. Found the arbor I use to hold a chuck in a chuck, drill press chuck is 3/4 for mount a smaller chuck when I need to use smaller drills. Arbor is same dia as tail stock ram plus it has a shoulder for the chuck to seat against.

Checking this time with a piece of rod in this chuck assembly gave much better results. Still have a climb from tail stock to head stock of 0.006 over 4 inches but thats in the chuck itself. Tighten jaws a tad more and the number changes, for good and bad.

Solution, live with it (for now)

Get a better quality chuck. Existing is a Jacobs 30B, have to look around andf see what available. Maybe even a new one of the same type, don't know how old it is.

So making a new tail stock ram similar to the pic is in order, chuck has to set square against something.

Robert

 

[Foozer]

Fooz, it certainly sounds to me as if the threaded mandrel or stub that the chuck screws onto and is rammed in the tail stock is the culprit here. As you said, relying strictly on a threaded part with out any register is questionable at best. Have a go at machining something that would be repeatable in setup. Not sure exactly what that might be but it will keep the mind occupied for a bit. ;D

BC1
Jim

beat me to the punch again, You got it, nailed the culprit down. Good to know my thoughts wernt too far off in left field as they usually are

Thanks

Robert

 

[Foozer]

Hit myself in the head here for not asking earlier.

If I make a tailstock ram, ah what material. piece is about 1/2 dia, perhaps 6 inch long. Adding a shoulder so a 1 x 6 but of what type of steel is suitable?

Thanks

 

[GailInNM]

Robert,
I would suggest that accuracy and not durability is going to be the main criteria. Therefore, I would use the easiest to cut material so it will be easier to make the ram accurately. 12L14 is probably the easiest to use.

I made two adapters for two different chucks to go from NMTB30 spindle to 3/8-24 thread chuck mount out of 12L14 about 20 years ago and they are still accurate and in use very often. I had intended them to be temporary, but as long as they still work well I never found need to replace them. I started with 2 inch diameter 12L14.

Keep in mind that all cold rolled steel, including 12L14 will have internal stresses, mostly near the skin, and will warp some as they are cut. Therefore, rough the entire blank to approximate size to get rid of most of the stresses before finishing to size.

Another steel to consider is 1144, commonly known as Stress Proof (TM). It has the least internal stresses of the cold rolled steels, is a little tougher than 12L14, and is not a lot more difficult to machine.

You might want to look at the Jacobs site for the recommended mount dimensions. The threaded mount dimensions are on page two of this document.
http://www.jacobschuck.com/pdf/Technical-Information.pdf

Gail in NM,USA

 

[kvom]

Why not get a chuck with a taper mount instead of threaded?

 

[Foozer]

Robert,
I would suggest that accuracy and not durability is going to be the main criteria. Therefore, I would use the easiest to cut material so it will be easier to make the ram accurately. 12L14 is probably the easiest to use.

. . .

You might want to look at the Jacobs site for the recommended mount dimensions. The threaded mount dimensions are on page two of this document.
http://www.jacobschuck.com/pdf/Technical-Information.pdf

Gail in NM,USA

Thanks, didn't think it would be anything special, the ease and durability factors you mention suit me just fine. I'll have to get some of each type you mentioned to see which agrees with my old fumble fingers.

Accuracy, yes, the better the fit the less room for error. Notice that great pains are often spent concerning the head stock chuck alignment but the tailstock is like the forgotten step child.

kvom: Why not get a chuck with a taper mount instead of threaded?

HMM thats a possible, I'll look up the chucks and see whats the doings for the 0 - 3/8 range

Thanks

 

[rklopp]

I am presently making a Monarch 10EE tailstock quill out of ETD-150. This is another LaSalle Steel product. Like Stress-Proof (1144), it's supposed to be stress relieved so it doesn't warp under asymmetric metal removal. ETD-150 is supposed to be Rockwell C (HRC) 32 hardness. IIRC, Stress-Proof has HRC in the low 20s. ETD-150 is definitely tougher to machine than Stress-Proof, but it's still quite nice to work with, and gives a gorgeous surface finish. McMaster-Carr sells ETD-150 in small quantities.

 

[Foozer]

I am presently making a Monarch 10EE tailstock quill out of ETD-150. This is another LaSalle Steel product. Like Stress-Proof (1144), it's supposed to be stress relieved so it doesn't warp under asymmetric metal removal. ETD-150 is supposed to be Rockwell C (HRC) 32 hardness. IIRC, Stress-Proof has HRC in the low 20s. ETD-150 is definitely tougher to machine than Stress-Proof, but it's still quite nice to work with, and gives a gorgeous surface finish. McMaster-Carr sells ETD-150 in small quantities.

somewhere between "I" and "quantities" my brain exploded

12L14, 1144, and ETD-150, ah choices from easy to less easy

Think I'll finish the little rocker and with it in hand, plus a big ol grin, a visit to the local shop with the "by the way you got any pieces of this kind of stuff in the scrap bin?" Box of donuts doesnt hurt either


Thanks

 

[steamer]

Foozer,

You said the lathe is old, you know when a lathe gets to the "vintage" stage, often times the tailstock base wears and you end up with the tailstock low compared to the headstock. Are you sure this is not the case?......just a thought.

By the way, shimming is considered acceptable for this situation....as well as making an eccentric tailstock spindle....but I digress.

Dave

 

[Foozer]

Foozer,

You said the lathe is old, you know when a lathe gets to the "vintage" stage, often times the tailstock base wears and you end up with the tailstock low compared to the headstock. Are you sure this is not the case?......just a thought.

By the way, shimming is considered acceptable for this situation....as well as making an eccentric tailstock spindle....but I digress.

Dave

Sleeve bearing AA109, ya its old, but didn't look really, "old worn out" like me in the morning. No real dings other than scratched paint. Rechecked with a piece of drill rod in the tailstock, all shims out, magnetic holder for DTI on cross slide and running that along the top of the drill rod right to left no discernible deviation. Perty sure the chuck and how it mounts is the problem. As to tail stock to head stock alignment a point to point with dead centers comes out OK.

Some shimming is acceptable, but when I hit the 30 thousands stack up it was time to rethink it. I can work around it till I make a new ram better suited to mount a chuck upon.

Thanks for the heads up

Robert

 

[Deanofid]

Hi Robert;

The tail stock ram should be 1/2" dia. You got good suggestions for materials, but I would also consider 1/2" drill rod. You can make a register disc for the external threaded end of the ram and save considerable turning time.

If you are using a threaded chuck, there should be a register surface on the very back surface of it. Make a disc that matches the diameter of the register on the chuck, about 1/4" to 3/8" thick, (suit yourself). Thread it for the same thread of the new ram.

Cut the threads for the ram in the lathe to about 2/3 their proper depth, and an additional length to suit the register disc, then complete the threads with a die. Screw on the register disc and either solder it on, or use permanent Locktite. Then put the whole affair in the four jaw, dial it in, and take a facing cut across the surface of the disc where it will meet the drill chuck. You might need to cut down the last two threads that meet the register disc so the drill chuck will screw down tight. You can also put a center point on the threaded end if you want to use the ram as an integral dead center.

After facing the register on the ram, your drill chuck should thread on tight and true against it. Mill the slot for the tail stock stud screw and tap the internal threads on the small end and it should be good to go.

That's one way to do it, anyway.

 

[steamer]

OK I'm confused.

Is the part you want to make the tailstock quil or a drill chuck arbor....? ???

Dave

 

[Foozer]

OK I'm confused.

Is the part you want to make the tailstock quil or a drill chuck arbor....? ???

Dave

I do have that effect on people.

Two in one? Both

The "quill" is but 1/2 inch dia with a 0MT in it,not very robust. Threading the end of it for a chuck has been done by others. Even bought one, but no register exist for the chuck. Only the threads are used to center the chuck. Something in that design is lacking. If I make the assumption that the rear face of the Jacobs chuck is perpendicular to its? terminology escapes me, anyway a new ram with a shoulder should square up the chuck, at least better than the current method. The optional taper chuck mount is properly more accurate, Sure I can manage it taking some time and care.

The 1144 steel seems to be in the mid range of suggested stock, only way tyo solve it is to give it a go and see what happens.

Robert

 

[steamer]

1144 is a good choice. It's a bit tougher to machine than say 12L14, but it very strong and will give a good long wearing surface.....Thanks for the clarification and good luck with it! ;D

Dave