Shars 3 jaw chuck

[Max Phillips]

I just wanted to post here about my recent experience with the 2" 3 jaw lathe chuck sold by Shars. I had been in pretty bad need of a jaw chuck for my little 8mm lathe, and got the Shars one for Christmas. They only sell them with either MT1 or MT2 shanks, but they can be removed and the chucks themselves have threaded backs. Mine had M14 threads. I removed the MT1 shank from mine, and made my own shank to fit my spindle. I turned the shank between centers on my larger bench lathe, and single pointed the threads at either end to get a really nice fit to both the drawbar and the chuck. By trial, I achieved a better fit to the spindle taper than most of the other collets and shanks I have purchased in the past. I trued up the mounting face for the chuck, and the chuck register, on the 8mm lathe itself, to ensure the greatest result possible. I knew I could make an accurate shank adapter, but it was completely unknown to me what sort of error the body and jaws of the chuck itself would introduce. These are all made in China so I wasn't getting my hopes up. I thought that, if I was lucky, the body of the chuck would be acceptably made but perhaps the jaws would need truing up. I chucked a test bar (a length of 1/8" ground round HSS) with a little over 2" sticking out from the chuck. I used a 0.0001" Starett Last Word test indicator to check the runout up close to the chuck, and then 2" away from the chuck. The runout was identical in both places, and was less than 0.0005". I was pretty blown away by that. Of course, I doubt that would be repeatable at different diameters - this is a self centering chuck after all. I'm pretty pleased with this chuck. Note that I disassembled, deburred, cleaned, and oiled the chuck prior to fitting it to my lathe.

These chucks cost $74 (U.S.), and if mine is at all representative then that's a real bargain. One thing I cannot attest to is the accuracy of the MT1 adapter it came with. I don't have anything with an MT1 spindle.

 

[Max Phillips]

I still can't get over this. I've repeated the test several times, with exactly the same results. I said less than 0.0005".... specifically, it's just a hair under 0.0003" every single time. I had to take a video: http://www.youtube.com/watch?v=SVYpq_fDcBI&feature=youtu.be

 

[D Magner]

Hi Max,
your indicator reads in thousands. your total indicated runout is just under .003", not .0003".
David

 

[wrobbie]

Hi Max,

Thanks for that -- I'm looking for a 3-jaw too.. Is that Shars chuck the same as this one?

http://www.ebay.com/itm/3-Jaw-Self-...9?pt=BI_Tool_Work_Holding&hash=item19cb5f4f11

- Rob (in Singapore, without Shars)

 

[Max Phillips]

Thanks for that David, HUGE oversight on my part!

 

[Max Phillips]

Hi Max,

Thanks for that -- I'm looking for a 3-jaw too.. Is that Shars chuck the same as this one?

http://www.ebay.com/itm/3-Jaw-Self-...9?pt=BI_Tool_Work_Holding&hash=item19cb5f4f11

- Rob (in Singapore, without Shars)

It appears to be the same from the picture, but who knows. That one is quite a bit more expensive than the one Shars sells, though. If you order from shars.com, or the seller "discount_machine", it is $74.

 

[doc_fields]

Max;
Congrats on your new tool! I'm sure you'll find it quite useful in your machining endeavors.
Couple of notes for you: Starret has a small rubber boot that goes over the end of your indicator to keep dirt out of the guts of it. I can pm the phone number and part number later this a.m. if you like. Also, on the previous tool you made for your friend to do watch hands in, an old trick was to place some paper inside so it would burn the oxygen out of the container and prevent oxidation and also scaling I think. Might help in his endeavors. Appreciate your work and your blog, keep up the good work!.....................doc

 

[Max Phillips]

Thanks Doc, I very much appreciate that! I didn't know there was a little boot available for these, that would be great to have the info for it. This indicator is on long term loan to me, its real owner doesn't have much of a use for it. I was planning on cleaning and oiling it for him in exchange for the use, but it would also be great to return it to him with the protective boot.

Regarding the accuracy of this chuck, the jaws don't seem to be fully hard so I'm going to true them up a little bit and then repeat this test. If there's any interest in seeing how I true the jaws, I can post pics of that process as well, but it's pretty easy to google and find info on it. There will always be a little bit of variance in runout with different diameter stock, depending on how much error there is in the scroll mechanism, but I've seen some nicely made old chucks with abused jaws get trued up to consistently chuck various diameters within a thousandth.

 

[Jerry Kieffer]

While runout is of course important with lathe chucks, there are other items of equal importance for consideration especially if for Horological use.

If the chuck is for a single specific specified application, selection is simple in that it will either work or not work.
In this case, lower cost can be a consideration if the product meets specifications.

However, If the chuck is to be used for General purpose especially Horological, then other considerations will come into play if it is to be useful.

(1) Are the jaws large and clunky for the size of the Chuck. If so, smaller delicate items can be very difficult to safely mount.

(2) Is the chuck Scroll course and crude making controlled tension on the jaws almost impossible. Under these conditions, larger work pieces under heavier loads can come loose while smaller delicate pieces can be damaged when tightening.

(3) Are the jaws and scroll cast from the same material causing them to "gall" each other affecting accuracy and operation with extended use. All of the inexpensive Asian/India chucks that I have inspected have been of this type construction.
Better quality chucks will have a machined scroll of different material than the engaging jaws.

(4) Are soft machinable jaws available for accurate and securely mounting valuable parts that cannot be damaged.

(5) What is the smallest part that can be mounted in the chuck. Down to about .030" in a small chuck is desirable.

(6) What is the jaw travel in relation to the size of the chuck. This can be checked by requesting Min./Max. work piece mounting before purchase. Many of the inexpensive chucks especially Asian and India have very short jaw travel greatly limiting mounting options.

(7) If used on a watchmakers Lathe with cone bearings, the chuck thickness will be an important consideration. The further the work piece is mounted in front of the spindle nose, the greater the load on the spindle bearings. This is one reason chucks supplied by the Horological manufacturers are very thin allowing work to be mounted close to the spindle nose. Extended loads can easily damage oil film cone bearings if not properly sized for this application as is the case with many watchmaker Lathes.

Unfortunately, various chucks of various qualities need to be compared side by side for these considerations to be understood.

Jerry Kieffer

 

[Max Phillips]

Definitely points to consider, Jerry thanks for contributing to the thread!

For my particular purposes, I just needed something a little more convenient for those times I wanted to turn slightly larger work than my collets allow, or when I want to turn some stock that is not a correct fit in my current selection of collets (which of course could be remedied by expanding my selection of collets). I have larger machines, and I have collets, so the 3 jaw is really a convenience (but one that I have wished for on multiple occasions). The thickness of the chuck was certainly a point of consideration for me as well though, not only for the issues you mentioned but also because there's only so much room along the bed of one of these tiny lathes.

For your specific points, I'll add my so far limited experience with the Shars chuck:
(1) Probably an issue, the jaws could be more delicate but they didn't stand out to me as being overly large. Don't plan on doing delicate work with this chuck.

(2) While not very well finished, the scroll and the jaw threads have an acceptable (to me, anyway) feel and are quite controllable. The movement is a little bit stiff, but during disassembly and reassembly I determined that this was due to the pressure of the spring washer underneath the circlip. The mating parts do not offer much resistance themselves. The grip feels confident when tightening the jaws onto the work.

(3) As you say, I'm sure the jaws and scroll are of the same material.

(4) With any of these import chucks of nebulous origin, I wouldn't bother assuming any parts or support are available (though I could be wrong). I shall enjoy the challenge of making a set of soft jaws someday, should the need arise... but I don't foresee it.

(5) The manufacturer claims a minimum clamping diameter of 1mm, but I have not verified this myself.

(6) According to the manufacturer, jaw travel is 7mm.

(7) I don't have much to go on for comparison here, but I get the impression that most of the older chucks meant for use on these little lathes are a fair bit thinner and lighter. I will say that I certainly wouldn't want one any thicker than this one, and one reason for my choosing this one was that it was the thinnest of all the el cheapo import chucks I could find. Some of them, especially that crude looking one sold by Grizzly, appear to be quite long and would probably be unusable on a machine like this.

 

[Jerry Kieffer]

Definitely points to consider, Jerry thanks for contributing to the thread!

For my particular purposes, I just needed something a little more convenient for those times I wanted to turn slightly larger work than my collets allow, or when I want to turn some stock that is not a correct fit in my current selection of collets (which of course could be remedied by expanding my selection of collets). I have larger machines, and I have collets, so the 3 jaw is really a convenience (but one that I have wished for on multiple occasions). The thickness of the chuck was certainly a point of consideration for me as well though, not only for the issues you mentioned but also because there's only so much room along the bed of one of these tiny lathes.

For your specific points, I'll add my so far limited experience with the Shars chuck:
(1) Probably an issue, the jaws could be more delicate but they didn't stand out to me as being overly large. Don't plan on doing delicate work with this chuck.

(2) While not very well finished, the scroll and the jaw threads have an acceptable (to me, anyway) feel and are quite controllable. The movement is a little bit stiff, but during disassembly and reassembly I determined that this was due to the pressure of the spring washer underneath the circlip. The mating parts do not offer much resistance themselves. The grip feels confident when tightening the jaws onto the work.

(3) As you say, I'm sure the jaws and scroll are of the same material.

(4) With any of these import chucks of nebulous origin, I wouldn't bother assuming any parts or support are available (though I could be wrong). I shall enjoy the challenge of making a set of soft jaws someday, should the need arise... but I don't foresee it.

(5) The manufacturer claims a minimum clamping diameter of 1mm, but I have not verified this myself.

(6) According to the manufacturer, jaw travel is 7mm.

(7) I don't have much to go on for comparison here, but I get the impression that most of the older chucks meant for use on these little lathes are a fair bit thinner and lighter. I will say that I certainly wouldn't want one any thicker than this one, and one reason for my choosing this one was that it was the thinnest of all the el cheapo import chucks I could find. Some of them, especially that crude looking one sold by Grizzly, appear to be quite long and would probably be unusable on a machine like this.

Max
For those who may not be familiar with watchmakers Lathe self centering chucks.

The thin three jaw, four jaw and six jaw chucks supplied by watchmaker Lathe manufacturers typically have jaws designed to hold thin flat objects like bezels and movement plates. In many cases they are simply referred to as "Bezel chucks" and are/were often supplied with various sets of different shape jaws.
At any rate, they were intended to be used with very light graver/drilling/polishing and other delicate loads close to the spindle nose protecting the oil film cone bearings. In addition, the light power transmission of a typical manufacturer recommended setup will also protect the bearings.

However the typical inexpensive small import chucks are designed for general machine lathe use that requires far greater power transmission and larger/higher load bearings than normally found in a watchmakers lathe.
Over the years I have acquired a few ugly looking watchmakers lathes at give away prices with mounted oversized improper chucks and accessories. All had damaged bearings to one degree or another. While I did not know the history behind these purchases, base on what I paid, " El-cheap-O" became "El-expense-O" for the one making the modifications.

While we all do things we should not when no one is watching, common sense and a full understanding of what is happening will pay great dividends.

Jerry Kieffer

 

[davestanda]

What i don't understand is that why would anyone with a larger lathe , like a sherline ,harbor freight style or anything larger than a watchmakers lathe use a three jaw chuck on one? Like jerry said the loads are different and there are better tools for holding some objects like bezels on a WW lathe...

 

[glenhead]

A four-jaw chuck won't hold a piece of hexagonal stock centered. A three-jaw chuck won't hold a piece of square stock centered. Either one will hold round stock, but a three-jaw is easier to true. A self-centering four-jaw chuck won't hold a piece of rectangular stock centered, but a four-jaw independent will. If you're making tools or other bigger stuff, all three are really kinda needed.

Glen

 

[davestanda]

right i knew that...The question is why even use a three jaw chuck on a WW lathe ,if you have a larger lathe with one...

 

[Max Phillips]

right i knew that...The question is why even use a three jaw chuck on a WW lathe ,if you have a larger lathe with one...

I much prefer doing smaller work on a smaller machine. Some larger machines were well made with smaller work in mind, but sadly my chicom 3-in-1 wasn't one of them. For small work, everything is in the way of everything else. I do have an instrument lathe with about a 7" or 8" swing (very nicely made, and good for doing small work) but it will be a while until I have it up and running. I enjoy the convenience of a self centering chuck on any machine, really.

By way of update on the Shars chuck, I recently modified it a bit by removing 1/2" from the rear (at the same time deepening the register bore, so that I still had it afterward). Having that much less spindle overhang really makes it look more like it belongs there, and it feels more rigid when turning (I can take heavier cuts without chatter). Reinstalling after the modification shows the same runout, which is great. Truing up the jaws will make me a pretty happy camper.