How do you align tailstock when drilling?

[jriechel]

I've found several threads discussing finding the center of a blank and getting the bit to start there, but my problem is slightly different.

Even if the bit starts dead-center, if the axis of the tailstock is not parallel with the axis of rotation of the blank while it spins in the chuck, then the bit exits off center, and wobbles while doing it.

How do you determine if the two axes are parallel with each other? My tailstock has quite a bit of side-to-side play that makes alignment a real puzzle for me. Any machinists out there? How about just somebody that has more of a clue than I do?

Thanks for thinking this one over for me.

Jeff

 

[frank123]

You really shouldn't have any noticeable side to side play in the tail stock.

If the play is in the fit of the tail stock to the ways, this is difficult to correct but if it is just in the shaft part of it it may be less of a problem.

If the tail stock is not parallel with the ways you will end up with the hole being larger at the entrance than at the exit, but there are several other causes of this ranging from poorly ground or bent drill bits to the way you start the hole that can cause the same problem. (watch closely as you start drilling and determine if there is any deflection of the drill bit as it starts -there should be none- that would indicate something in your drilling technique that is easily corrected)

How are you mounting your tooling into the head stock and the tail stock? A dirty or poorly fitting taper can cause a misalignment like this.

I should add, put a center in both the head stock and the tail stock and move them together while fully retracted. They should touch exactly point to point. Then back the tail stock off a bit and extend the tail stock ad far as it is meant to extend then do it again. if it is not still touching point to point there is a good possibility that the tail stock axis is not parallel to the ways.

My experience is mostly with metal lathes, but in this aspect there is not much difference between a wood and metal lathe.

 

[Rich L]

How do you determine if the two axes are parallel with each other? My tailstock has quite a bit of side-to-side play that makes alignment a real puzzle for me.

Jeff

What lathe have you got?

First of all if your tailstock has side to side play you need to fix that - it shouldn't and it indicates that something is not clamping down properly or you have a loose gib in there.

Frank's idea is great and I do that from time to time. I ground down a couple of broken carbide 1/8" end mills to to about a 15º sharp point put one in the headstock (with a collet chuck) and one in the tail stock and brought them together. You'll see the alignment, or not. Your tailstock should (maybe) have at least an alignment for side-to-side adjustment. Vertical is different and sometimes depending on the lathe, impossible without grinding.

With this method you'll get an idea of concentricity along a short path. To check parallelism along the whole path you'll need a good standard to chuck between centers and a good dial indicator.

@Frank - where are you in Colorado?

 

[jriechel]

I have a Harbor Freight 10x18 bench-top lathe (#65345 ). I think I was vague in my original description. I was referring to side-to-side play in the tailstock before I clamp it down. After I do that, it's solid. The trouble that I'm having is knowing when it's aligned with the axis of the blank when I clamp it down. Even if I center the bit on the end of the blank, the tailstock furthest from the blank could be skewed to either side (from an overhead perspective) and I wouldn't know. When this happens, the hole starts off okay, but gets more eccentric as it drills deeper. The bit wobbles in an increasing diameter as the hole deepens.

I'm using the PSI pen blank chuck with a Jacobs chuck in the tailstock. Both are MT2 and I just jam them it with a little twist. I didn't receive any instructions on this, so I just went with what seemed right. I'm also using the PSI brad-point bit that was supplied with my original pen kits. I'm starting to think that maybe this bit design isn't helping things.

Jeff

 

[ossaguy]

My Delta 46-460 has this same slight side-to-side slop.I found after getting the 2 centers exactly lined up that if the casting of the tailstock is flush with the edge of the rail,it will be aligned.So before I clamp it down,I feel the edge to get the flush-fit,then clamp it down.This works for mine,but I wish it would have a tighter,exactly positioned fit there.

Steve

 

[Timbo]

If you can't fix side to side play try this work-around. With the blank in the headstock and your drill bit in the tailstock, bring the bit up to the blank until it almost touches. Turn the lathe on. I'm usually on the slowest speed. Pull the bottom of the tailstock toward the headstock very slowly, but firmly. As the bit engages the blank keep forward pressure on the tailstock. You'll notice the bit wobbles around a little, then centers itself on the spinning blank. Once it centers, lock the tailstock. Basically, the bit takes the path of least resistance, which is in the center of the spinning blank where it does not have to move. This only works using a stiff bit (1/4" or larger), and only with hard woods. Thin drill bits will flex and drift off center, soft woods allow the bit to sink in before centering. Good luck.

 

[Rich L]

Don't know anything about your lathe but here goes anyway.

1) Your tailstock has to have at least two surfaces to bear on: one generally is horizontal and another that is either vertical or a "V" way. Your tailstock has to have matching ground or scraped surfaces to make alignment worth a crap. If you don't have that or can't verify that, try this...

Put a piece of drill rod in your chuck with about 4-5 inches stickout. Put a piece of the same in your tailstock chuck. Move your tailstock with drill rod up to the piece in the headstock and lay a straightedge against the two. If you see daylight (more than a couple thou) try to "adjust" your tailstock to line them up. If you can do this then you'll have a method to line things up at most close-in positions of the tailstock.

If you're still getting excessive wobble get rid of the brad point drill and look into using shorter "screw length" drills at least to get a hole started at your final diameter and then the longer drill will slip right through. Anything to improve rigidity will help.

Timbo is writing as I am - try what he says, too.

There's another thread ( http://www.penturners.org/forum/f14/center-drill-prior-larger-drill-94844/ that discusses drilling )

Is that part faced off nicely before you drill? What diameter are you drilling? On second thought perhaps your entire problem is with that brad point but others might chime in on that opinion.

Cheers,
Rich

 

[jriechel]

I just inspected my lathe for the surfaces that the tailstock bears on. The top is the flat milled side of the bed that everyone sees. Your comment about a v-way makes a lot of sense for the clamp under the bed, as that would center everything. I have no idea if this is how other companies do it, but the supplier to Harbor Freight isn't one of them.

I've got a rough-cast surface under the bed that looks parallel the the top side surface. The clamp is a single washer with the top half "rabbeted" in to give a shoulder that fits between the bed rails, and the bottom, larger-diameter half that extends a little beyond the rail gap to provide the clamping pressure. There is only one of these. Again, being ignorant about most things lathe-related, it seems to me that having one of these toward the front of the tailstock and another at the rear would have reduced the skewing problem. The best design would seem to be a milled V and a matching piece as the clamp. But then, the lathe wouldn't have been as inexpensive, would it?

If only I had know what to look for a few months ago. Oh well, I'll have to struggle on making this one work. I will try putting a large diameter rod into the chuck and checking against another one in the tailstock chuck. I can understand the idea there.

I'll report back...

Jeff

 

[plano_harry]

Jeff, seems like there is a better way. If the tail stock is not aligned, you aren't going to be able to turn a pen in the first place. Assuming it is somewhat close, don't chuck the blank - instead, put a Jacob's check with your drill in the headstock and a live center in the tail stock. Center punch or pilot drill the centers of both ends of the blank. Mount the blank between the drill and the live center. Hold the blank with a clamp, turn on the lathe and advance the tailstock to drill the blank. You can't miss. Works every time. This works with straight blanks, warped blanks, antlers, etc and you don't need the expense of blank chuck, or drill press.