PDA

View Full Version : Need guidance; use of Tail Stock!!



hwingo
11-03-2013, 12:25 PM
Good Morning All,

Below is an image of a Tail Stock that I purchased in conjunction with a Super Spacer. I’ve had it for at least 10 years and have never had a need to use it until recently. I’m having considerable problems getting this thing set-up, therefore, I am in need of guidance.

Those of you having a similar accessory know that during adjustment, this device “rises” or “falls” to align center height. Additionally, it angles upward or downward (can tilt in two directions) so essentially such movements makes this tail stock fully articulated with exception of lateral movements.

I am attempting to spiral flute a rifle bolt. The rifle bolt is secured by my 4th axis (4-jaw chuck) and the other end of the bolt is being supported by the tail stock.

Getting this thing aligned is troublesome. Just about the time I have it in-line (by visual inspection) with the center hole, it begins to “cant” as I tighten the clamping nuts AND it has a tendency to angle upward as I tighten the clamping nuts. It’s been a real pain in the butt. Adding “insult to injury”, though able to rotate the bolt 360 degrees, part way through the rotation the 4th axis wants to “bind” or a better phrase is “get stiff”. If I loosen the dead-center, stiffness all but goes away and the 4th axis then rotates freely.

Apparently I am not doing setup correctly. How I set up this job is as follows:

1. With one end secured in the chuck I dial in the bolt (near the free end) until I am within .001”. I call that good.
2. I fabricated a piece that having a small tang (.063”) which fits into the firing pin hole and a flat face rides against the face of the bolt. At the opposite end of the piece is a center hole (drilled with a center drill using my lather). The small tang helps to keep the piece positioned and a light force is placed against the face of the bolt via pressure applied from the dead center in the tail stock. This part is visible in the image.
3. Naturally, I try my best to align the tail stock with the center hole and I do try to keep the tail stock parallel.
4. When I feel the 4th axis getting stiff, and as a test, I loosen the dead center and the work piece visibly drops leaving me to surmise that something is out of “whack”. With the dead center away from the center hole I use the indicator to check the work piece. It’s holding true. With the center in place, the indicator shows true until it begins to get stiff and then it goes out by at least .015” and sometimes more depending on how tight I have the dead center articulated with the part.

So what am I doing wrong?
Why am I experiencing stiffness or binding during rotation?
What must I do to prevent binding but still provide adequate support for a clean cut?

I must support the free end or otherwise deflection will occur when the cutter engages the work piece and one end of the cut will be deeper than the other end

Harold.


http://i234.photobucket.com/albums/ee38/hwingo_2007/TailStock_zps59d39034.jpg (http://s234.photobucket.com/user/hwingo_2007/media/TailStock_zps59d39034.jpg.html)

Toolguy
11-03-2013, 12:47 PM
The way I align a tailstock like that is to extend it out, clamp the pointed end in the chuck or collet of the indexing fixture and clamp the height and angle bolts tight. Then remove from the indexing fixture and you're set.

In your case, the point is offset towards the top of the ram. For that situation I would clamp the bolt adapter centered in the 4 jaw chuck and put the dead center point in that as it is in the picture. That gives you the height. Then adjust the ram for parallel to the mill table and tighten bolts. If the dead center is not indicated dead level, it will change height as it goes in or out.

doctor demo
11-03-2013, 01:00 PM
Harold, I'll take a stab at a suggestion. I've used tail stocks on mills on at least a few occasions . Different than Yours but similar. What You need to do is set up the indexer and tailstock without the part , think of it as building and checking the components of a lathe head and tail stock. Use a known straight test bar and an indicator. Set up and align the (headstock) and then set up and align the (tailstock ) to the (headstock).
The first time setting the pair of them up together can be a time consuming and frustrating exercise , but making sure the (headstock) spindle is aligned in the proper orientation required to the table before adding the (tailstock) into the equation and making sure they are in sync before introducing the part, otherwise it would be like using a lathe with the head and tail stocks looking in different directions and elevations and trying to make a part.

Steve

winchman
11-03-2013, 01:46 PM
+1 to what Steve suggested, and I'd recommend making a keyed washer to go behind the lower adjustment knob on the TS. The surfaces on either side of the curved slot might not be flat/even, and that's causing the movement as the knob is tightened.

hwingo
11-03-2013, 02:07 PM
Well, I'm gonna spend the day working at this. Hopefully I can resolve some of the issues I am having. I will keep you informed and I will certainly "return to the well" when I hit the proverbial wall ....... again. Thanks Guys.

Harold

Barrington
11-03-2013, 04:00 PM
Two separate problems - difficulty in adjustment of the tailstock aside, it would seem to me that the 'centre hole' may not actually be centred relative to the surface you have dialled in ??

Cheers

.

hwingo
11-03-2013, 07:59 PM
Two separate problems - difficulty in adjustment of the tailstock aside, it would seem to me that the 'centre hole' may not actually be centred relative to the surface you have dialled in ??

Cheers

.

And you Sir, may be right. It's not at all uncommon to see firing pin holes a wee bit off center. Too, there is a substantial likelihood that the bolt was quickly fabricated thus lacking precision. During that period allies were attempting to facilitate the War effort so I would say that some fast production runs escaped the watchful eye of the inspector. A friend and I discussed that very subject this morning.

But I think I discovered the greatest problem. The 4th axis table was very loose and easily deflected in excess of 0,150" without effort. I've tightened that up and I cannot see deflection as before. I'm certain it will flex but that will need to be measured with an indicator (which is the next step) in discovering mechanical issues.

Harold