soft jaw boring

Here's a great description of the process by Harold Vordos:

-Bill Fill Olympia, WA

Be careful taking Harold's word on things. He's pretty long in the tooth and maybe getting senile.

Seriously, I read the article and would only give Harold grief over one thing, his preference of steel. He did give me a positive response when I suggested 7075 for soft jaws, so maybe there is some hope for the Grampa. To add some emphasis to the sizing of your jaws when boring, *if* you don't get the bore to exact size of your parts, miss the size under, not over. If undersize you will get 6 contact points, the edges of each jaw. If oversize you only get 3, and those are a crappy 3.

michael

I owe you an email, H. Maybe later tonight, still quite busy.

You tell the old hippie (Michael) that he can't weld new tops on his 7075 jaws, so they aren't as good as steel ones, if for no other reason, that one. It's a lot of work to make a set of soft jaws, so why not make them from steel so you can recycle the base pieces by welding on a new top piece when they've been used up? I think I may have mentioned that in my long, dragged out post. Damned hippie. It's a hard enough job being a Grampa without having to constantly correct you!

Just like a flaky old hippie, always running late.

If Michael had my years (oh! so many!) of experience, he'd know that boring soft jaws slightly undersized is not a great idea. When you grip your nicely finished parts with the sharp six corners of the jaws, your finished parts get marred. While they grip better, such as for roughing, I'd personally err on the side of too large, if for no other reason, the jaws don't damage your finished parts when you turn them over to do the second finishing operation. If you miss by only a thou or so, it doesn't really make a great deal of difference. The lesson to learn is to use a spider, discussed in my original post, so you can readjust the jaws slightly and re-bore them, achieving the desired size and not taking off much in the process. The spider is a wonderful tool, be sure to make one.

In truth, you don't want the jaws either too big or too small. When you're doing fine work, boring the jaws to the desired diameter is critical to success. If you go either above or below targeted size, you'll often introduce concentricity problems because the scroll on chucks isn't necessarily dead true. When you hold size, not only on the jaws, but on the parts you intend to chuck, you end up using the same place on the scroll from part to part, which gives you the best chance of holding concentricity.

Good luck with your soft jaws. Best holding device going for lathe work!

Harold

(Looking forward to the email, M, but don't lose sleep, get the work out first!)

I'll stick with Aluminum, you did a bunch more turning than I ever will. You are correct about sizing the bore, I spaced back to the 60s and did not mention the roughing aspect. But I don't understand the comment about marking the parts, I have seen none of those on my parts for so long I have forgotten how they get there. Finish looks the same all around. Dang arm is sore from patting my shoulder. Back to making chips.

BTW, heard the one about the pot and kettle? Hippie indeed.

grampa michael

Hey, hippie, get a hair cut!

The really sneaky trick is to chuck up an slightly undersized innie (a slug), make a ring, drill and tap the jaws, chuck the work again lightly, attach the ring with screws very tightly, knock out the work, reset the pressure, and bore with the pressure, direction, and diameter the same as they'll be for the work. Did I get that right?

For an innie, the ID of the ring clears the unfinished work OD. For an outie, the OD of the ring clears the ID of the work.

Just remember, finish the jaws with the direction and pressure the same as for the work, and finish them to a close fit, maybe even size-to-size, with the surface they will grip. This is just not useful for doing a one-off. There's too much time invested.

Yours,

Doug Goncz (at aol dot com) Replikon Research, Seven Corners, VA

What you stated is correct, but so is your statement correct about the procedure of the ring being too labor intensive to be used for a one-off application. Properly used, soft jaws can economically be used for a one-off, you just have to use better (read that faster) procedures.

There are no benefits using your system aside from boring jaws for holding parts by the interior. Using a spider to set the jaws for external gripping is extremely fast and allows for miniscule adjustments of the jaws so very little of the jaw needs to be machined in order to get them running properly. There is nothing to make, you just grab the spider and adjust it for the job at hand.

Using a ring with tapped holes in the face of jaws doesn't permit fine adjustment. If you over cut the jaws, there is no way you can make a minor adjustment so you can re-bore to proper size. I would not recommend that procedure for anything but internal gripping, and even then you'd likely have to make the ring to fit the job, otherwise you'd have to remove a lot of jaw material as you went from one size bore to another.

I have no magic bullet for internal gripping. I've done it, but have used a ring of proper diameter to load the jaws. Sadly, I haven't come up with a device of sorts to replace the ring.

Harold

Hey Harold,

I thought I just might ask from someone that knows, and that sounds like you. I've asked my buddies in the tool & die, and they have never seen/heard of one. A couple of years back, I E-bid on a circular thingy that the seller had no knowledge of it (a la Babin?). Turns out I didn't either! I thought I might make a quick centering device mounted to the outboard end of the lathe spindle, for holding longish stuff through the spindle. Anyway, for 10 bucks plus shipping (I was the only bidder) I got something bigger than I expected, and too big for THAT job.

It is a ring with three scroll driven spoke "jaws". I don't have it to hand, but it may be about 1" or so thick, has an OD of about 10", an ID of about 8" or less, and the "ID" ends of the jaws have a knurled boss (1/2" Diameter??) perpendicular to jaw motion. It's got a nicely chemically blackened "gun barrel" finish, and made by "ROYAL" in Italy.

So, I tossed it under the bench for a future-as-yet-to-be-determined project. Then later I saw something that made me realize it might be for either truing chuck jaws, or lo and behold, the "bosses" mentioned are a perfect fit for the mounting holes in the soft jaws of the chuck on my 15" Colchester. So maybe it is that "spider" you and Doug mention.

An now (finally) my question. No way I want this thing turning at normal turning speeds. The only way of applying pressure to tighten it in place is the hand operated scroll, ie no "chuck key". It would make shrapnel look like kleenex if it came loose. But I would think that turning it at less than the turning speed for the eventual workpiece wouldn't be right either. Can you enlighten me as to it's exact use? I have maybe 10 sets of soft-jaws available, but I've never used any of them.

Take care. Always enjoy your posts.

Brian Laws>

BIGGISH SNIP

big snip----

Hey Brian,

If I'm following your description (good chance I'm not, so send me a pic on the side if you'd like, which would make it easier for me to suggest if I'm right), the adjustment that is made by hand would be strictly for adjusting the position of the restraint, which would be the fine tuning of the spider I mentioned. That function permits the location of jaws for optimum machining, i.e., locating the jaws for minimum stock removal. The pressure of holding the device in place would than be applied by the chuck wrench, via the chuck, as the jaws are tightened against the spider. At this point, one would run the chuck at the proper speed for machining. The spider is unlikely to move easily, and it is not receiving any cutting forces.

What you have may be this device!

The advantage of your device over the one I use is that yours will work for chucking in either direction, inside holding or outside holding. If it's what I think it is, I'd give my interest in hell for one like it for my Graziano. Turning chuck jaws for internal holding is much more difficult (labor intensive) without a device such as yours.

If you haven't used soft jaws yet, I think you're going to be pleasantly surprised when you first do. They are truly the magic bullet for holding most anything in chucks. There's no way I could get by without them, even for one-off's. Regardless of the time it takes to prepare a chuck to hold a specific item, soft jaws still are usually the best choice. The very idea that you machine them to the same diameter permits tighter chucking without distortion, and the smooth jaws don't mark your part(s). So many advantages with soft jaws, so few with hardened jaws.

Thanks, Brian. I've enjoyed sharing what little I know. I was given special attention when I struggled, by one person that saved my job when my probationary period was not successful. I feel I owe a debt for this wonderful person's gift, and I try to repay it by helping others. Funny thing is, some of them don't much like hearing it! Ah well! Others do, and they make it all worth while.

It's always a pleasure to read your posts, too, Brian. Love your upbeat, friendly ways.

Harold

I think you should just give up on the outlock and just send it to me. I think it would go real nice with my 16" Pratt & Whitney lathe. By the way I have run outlocks at 2500 RPM and I have had no trouble at all with them. J&L calls them "True Jaws for power chucks". Look in the number 73 catalog on page 1088. Item number QDR-75230J. We have always called them outlocks.

Richard W.