Home Forums Hunting & Shooting Gunsmithing Lathe question

Much of the time the lathe is used to produce components of a larger assembly:

Custom stainless hinges for a transom door.


Delrin fairlead for a custom stainless hawse pipe.


Base for a custom stainless padeye.

Pal, I love it. I have a boat and am around them a fair bit. 👍

Does everyone here understand the utility and sheer, I dunno, elegance of soft jaws on a lathe chuck, and how to make/cut them? Glad to explain it, took a few pics out there just now as my big lathe still has the soft jaws on it. If you have a chuck with 2-piece jaws, and you ain’t making soft jaws for it, you are missing out on a universe of work holding….

Thanks and thanks.

The beauties of soft jaws on a lathe are several. First and foremost, they are amazing problem-solvers. Parts that are a pain to perform certain operations on with stock jaws- thin discs needing a facing cut comes to mind- are trivially easy and repeatable. Or, parts that will get the finish marred by hardened jaws. Or, parts where you need to absolutely maximize the the number of, and/or and size of surface-area contact points of; I have a big (12 lbs?) out of balance casting I work with where that’s critical. Soft jaws are also incredibly accurate (concentric).

The chuck in the picture is an Adjust-Tru type, meaning the chuck body itself has some limited adjustment range to bring a part to true. But for illustrative purposes let’s imagine a fixed chuck; you put it on the spindle, and it’s fixed in place. What you get is what you get as far as concentricity.

(that’s kind of an abomination; all scroll chucks should be Adjust-Tru type. But I digress. Most are NOT)

If our subject fixed chuck has 2-piece jaws you can take the top jaws right off. You can see on the pics of mine with the aluminum jaws for easy visual contrast how the top jaw fits into the master jaw. It locks very precisely to the master jaw- it’s a very light press fit. Zero wiggle between master jaw and top jaw- that’s important. I make mine from bar stock and when milling that cross piece section I leave it about .0005” over and do the final fit with a few strokes of a fine file. Each jaw is numbered to match the number stamped in the master jaw. You can find the dimensions for master and soft jaws online- it’s a standard. For that matter you can buy them, but I make my own. This is an uncut, mild steel soft jaw, one of a couple sets (of 3)on my shelf, waiting to be needed.

What makes them so accurate is that you cut the gripping surface right on the spinning lathe. You are cutting a pocket for the part, using the machine they’ll be spinning on, right into the jaws, “en situ”. It HAS to be concentric. Hence the elegance.

There’s a key step to this. You’re probably thinking “but the jaws wiggle in the chuck body on the scroll”, and that’s correct. That’s what the back jaws are for. More on that below. First things first, close or open the uncut jaws to where you want them such that they’ll have the most grabbing surface once your pocket is cut. To do that, make a slug the exact (sic) diameter of the parts you intend to grab. Or, as often is the case for me, I’m working a new prototype part through the steps to make it, and I come to a situation where I need to grab a diameter I just machined; you could use THAT instead of a slug. But you need the slug at the desired finished diameter; the slug will be your gauge to test-fit the pocket you are cutting into the jaws. You are cutting that pocket the exact (sic) size of the diameter you’ll be grabbing.

So you’ve got your blank jaws positioned where you want them, no pocket cut yet, but they are loose and floppy. Cannot cut them like that, don’t try. That’s where you need a second slug, and it needs to be the correct diameter (ish) such that the back jaws are grabbing it when the soft jaws are where you want them. That tensions the master jaws against the scroll. A thousand words. See the slug deep in the chuck with the red X I put on it? That’s the purpose of those back jaws!



I reverse those aluminum jaws to grab two different diameters on these parts I’m running. A huge plus I forgot to mention- note the built-in work stop you create via the depth of the pocket! If you made the jaws correctly so that they have that light snap-fit onto the master jaws, you can reverse them with impunity, without even needing to adjust concentricity, once you’ve adjusted for the first side….. (that comment is assuming now that you have a Set-Tru or Adjust-Tru type chuck), because, at least in this case, I cut both sides of those jaws with the chuck body in the same position, adjustment-wise.

On a non-adjust-tru chuck, IE one mounted directly to the spindle, it *should* repeat its basic position on the spindle quite well. So when you put the jaws back on the chuck, they’ll be in the same place on the master jaws- because of your careful snap fit-, and the chuck body will be in the same place on the spindle nose, because of the taper……. And so there your pocket will be, in your soft jaws, running damn near perfectly (sic) true.

(Or, if you are an Adjust-Tru geek like me, put the soft jaws on then use your slug, or a part, to set everything running true at that gripping diameter. I won’t own a scroll chuck without this feature. A chuck that is out by even just a few thou as far as concentricity is useless to me. It just creates downstream headaches…)

It’s the same idea as 5c “emergency collets”, which are another thing, if you aren’t using them, you should! Obviously just buy those. They are CHEAP.

Nice work

Wish I was better set-up and about 20 years younger. There's an auction of an engine speed shop nearby with a Clausing Colchester 13" x 36" engine lathe, and a Gorton 10" x 42" Mastermill that I'd have loved to have, and just a few blocks from a couple of the machinery movers that I've worked at over the years.

Link: Auction










Phil

Stout looking little mill!

Yeah……….. I could become a machine collector. My wife reads me the riot act every time I move a new one in, haha. It’s a project… I usually have to rent an all terrain forklift, although, with the Feeler I was able to very slowly move it from the big box van I rented onto my slab, on rollers, with pinch bars. It was sketchy AF. I had a strap on it in case it got away. Took a couple hours to move that last 4-5 feet down the loading ramp.

I’d like to have a Hardinge “chucker” and a precision surface grinder…. and and and…. but those two, I could make $$ with I think.

I lost a big customer this year, they put together their own machine shop, so I’ll be chasing new business when I get back from my big backpacking trip in a couple months. I’m going to try to find more small, very precise, ongoing work for the Feeler. Maybe medical stuff… hydraulic parts… who knows. I’ve machined literally thousands of fairly large heavy castings in the last 6-7 years and just handling them, in a production scenario, wears on my body. Got some forearm tendinitis I battle, etc.

Check out some of the tooling at the auction... I don't know if it is a bankruptcy, a retirement, or a death but these types of auctions make me sick seeing someone's life's work being pieced off at little to nothing.

Riser Block on the head of that mill is worth as much as the mill...

Phil

We see lots of estate sales in my rural area. I agree, they mess with my head too. That’s at the heart of the riot act my wife reads me- she doesn’t our kids to have to deal with huge old iron I’ve accumulated.

Any of you ever roller burnish chambers? Makes them slick as snot and accurate as hell. Noticed a box of tooling in this auction had a few of them in it.

Phil

When I lived in Prescott I went to a local shop that had a bunch of gear hobbling machines. He had a Graziano and an HVLH for sale. Either one for $3000. I thought the headstock on the graz way too long. The HVLH not big enough. I bought a Nardini. I wish I had that Hardinge

I will always owe you for giving me the nudge to buy the Webb when I was wavering! 👍 To quote you, “why not?” I had no good answer… so I bought it! 10-hr drive each way to go get it. That wasn’t fun.

A really clean Webb turned up 5-6 years ago a bit south of here… I think the guy wanted $8k for it. I had the money, but I was like, why have TWO? Regretted that ever since. They are around $30k now new.

The only bummer about most HLV-H is they don’t do metric threads…. one reason I jumped on this Feeler was that it’s English/Metric. I have two customers who need metric threads on small work- it’s amazing for that. The Webb does metric (with a gear swap) but since it’s an English leadscrew, you have to leave the half-nut clamped and gear chain engaged the whole time. So to back up to take the next threading pass, you have to reverse the whole machine. Not SO bad with a VFD, but kind of a pain. Effortless on the Feeler/HLVH E/M.

Lathe pick-up porn. That forklift had janky hydraulics.

I did some metric threads on my Nardini last year. Quite a pain changing all the back gears and learning to thread with half- locked in and backing up the machine

That will make a good watch repair machine😁

Chapuis does making the Manurhin MR73 since 98……Manurhin has since 73 when they were making them.
I want to do the throats in cylinders with them.
Maybe chambers. But I don’t have much problem there……..the brass always drops out if the brass is good

What's the consensus on Precision Matthews lathe? I'm looking at their China-made 1130V. I like the 1 1/2" spindle bore, short head stock, VFD, and 120 V power.

My purpose for this machine would be muzzle threading, general turning and boring of small parts.

https://www.precisionmatthews.com/shop/pm-1130v-lathe/