# wanting a 3 jaw chuck



## rambin (Nov 21, 2018)

so I ve got a 700 series 10" logan/wards had it a bit over a year  and always wanted a 3 jaw for it just to make life that much easier. I know i'll still need the 4 jaw occasionly but its not a big deal to change.  anyhow its a 1 1/2 8 arbor if  rmbr right. I see shars has 20 percent off for black Friday.    Im hoping I can buy something that's plug and play?? not really sure my skills are ready for modding a back plate as of yet.
thinking a 6 inch is what I want?
looking at the shars site I only see 2 options and they both seem cheaper then expected?  are they any good or should I be looking elsewhere?
https://www.shars.com/catalogsearch...ter=6&mounting=1-1/2+-+8&no_of_jaws=3&q=chuck

im still very new to all this machining stuff so any wisdom/advice is appreciated
I also see some models where the 1 1/2 - 8  Back plat?e is sold separate which would add some other chucks to the line up.   ?


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## BaronJ (Nov 21, 2018)

Hi Rambin,

If you don't feel upto machining a backplate then you need a chuck that has a threaded back or comes with a threaded, already machined backplate.

You will find that threaded back chucks are quite a bit more expensive !

Having said all that, machining a backplate is not at all any more difficult that a simple turning job. If you can turn to within a thou and drill and tap a hole, you have it cracked.


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## Wolfram Malukker (Nov 21, 2018)

Even a pre-machined backplate will need to be machined to fit the spindle nose properly. It is VERY easy to do correctly if you already have a 4-jaw!

Here's the way I go about it:

Buy your 3-jaw chuck. Get one with removable top jaws, so you can flip them by unbolting them. This also allows you to use soft jaws later...very nice feature and worth the extra few bucks.

Buy your backing plate to suit the chuck you choose-you want one that is either undersized on the threads (for most lathes) or one that is tapped to the standard 1.5x8TPI (for the Logan, with it's slightly oversized spindle thread)

Get them home, clean the grease off, check the chuck for basic function and no binding. Clean the backing plate up and mount the backing plate in your 4 jaw chuck on the lathe, back side of the plate facing the tailstock.

Dial in the plate, hopefully there is a little register left where the thread is not all the way through-this register is what you'll machine AFTER you have fitted the threads, but it's handy to use this to dial in the threaded bore. If there is no register, do your best to dial in the threaded bore, by trusting that the bore and the OD of the plate are concentric and dialing in the OD of the plate. If you get an unthreaded backing plate, this is the time to bore and thread the plate slightly undersize to fit the spindle of your lathe.

Now that the plate is dialed in on the 4-jaw chuck, UNSCREW the 4-jaw chuck. DO NOT remove the new backing plate from the 4-jaw. It will stay in the 4-jaw chuck for now. Flip the whole assembly over, and test fit the backing plate threads on the spindle. Hopefully, they thread on most of the way, then get tight and don't want to thread on fully. If they thread on fully, hopefully they stop before they thread up onto the register of the spindle. If it threads right up to the spindle and over the register, well, it's not the end of the world-you can bore the backing plate 1/8" deep and 1/8" bigger ID and press fit a steel ring, that can then be bored to the proper fit.

So the plate starts on, and threads on a turn or three, but won't thread on the whole way? Great. This is the ideal situation. Unscrew the backing plate, flip the assembly, and thread the 4-jaw chuck back on. Next, you'll need to pick up the thread, and carefully cut it slightly deeper with an internal threading tool. Here's how you do that:

To set up the compound slide, start with the slide set 90* to the lathe axis (aligned with the cross slide). Next, move the handle end of the cross slide to the right, towards the tailstock, 29.5 degrees. You're gonna do most of the cutting with this slide, not the cross slide.

Get out your internal threading tool. This can be a high speed steel tool you've ground to a proper 60* point and relieved for use as a boring bar, or it can be an indexable boring bar with a threading insert fitted. Either will work. Check to make sure it's big enough to cut the root of that chunky 8TPI thread. Set it up in the toolholder, and get it aligned to the axis of the lathe, so your thread profile is cut nice and square to the bore.

Next post we'll finish picking up the thread and continue on.


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## Wolfram Malukker (Nov 21, 2018)

Now that the internal threading tool is set up and the compound slide is set to the 29.5 degrees we want, it's time to pick up that 8TPI thread. It sounds scary to some people, but it's very easy to do and is a good skill to have.

Configure your change gears, or your quick-change gearbox, to cut an 8 TPI thread. Get the threading dial engaging the leadscrew and working.

Engage the half-nut, and rotate the chuck and workpiece by hand, making sure that you're cutting the proper direction. The tool should advance toward the headstock, and the spindle should rotate in the "Forward" direction.

Now use the cross slide, and run the tool in so that you can get into the bore without touching the existing threads. Disengage the half-nut and rotate the chuck until the "1" mark is lined up on the threading dial-then engage the half-nut. Use the cross slide to bring your threading tool back as close as you can get to engaging the thread, but not actually touching. Use the compound slide to adjust headstock-to-tailstock position, and juggle the two slides until you can rotate the chuck by hand, in the correct direction, and the tool bit follows the existing thread with no crashing. DO NOT disengage the half-nut while you do this, it will only cause problems if you're not very familiar with single-point threading. There are easier methods-but this method works with ANY thread, so it's the one I've described here.

Now that you've got your cutting tool aligned AND timed to the existing thread, make a threading pass. Don't use the cross slide for your feed advance-use the compound slide. That way, each division of the compound slide is almost exactly HALF the actual marked value, effectively doubling the resolution of the dial. This is an 8TPI thread so the carriage slide moves FAST! You may want to turn the lathe by hand if you are not confident in your ability to disengage the half-nut on time. 

Take a small cut-just enough to hear the tool scraping-and then retract the tool, disengage the half-nut and run the carriage down the ways, shut the lathe off and do another test fit, by unscrewing the 4-jaw and flipping the assembly over again. See if it threads on all the way up to the register-if it does, and the register is undersized still-perfect. If not, get it to thread up to the register.  Remember to use the "1" on the threading dial every time you engage the half-nuts. As long as you do not take the backing plate out of the 4-jaw, you do not disengage the leadscrew with the tumbler or by changing the quick-change box, and you don't remove the threading tool, you will be aligned properly to make another threading pass if you use the "1" mark on the dial.

If the register cut in the backing plate is too big, press in that 1/8x1/8" ring I mentioned earlier, and then you'll bore the register-if it's too small, and won't thread on fully because the register hits, it's time to bore that register until it's a very light drag when you thread on the backing plate. Just like doing the threading, unthread the 4-jaw, flip it, and test-fit that backing plate until it goes on correctly.

You should feel the register bore just slightly increase the amount of force needed to thread the new backing plate fully onto the spindle-it should not require two hands to thread on, but you should feel a little difference right there for that last half-turn or so. That's the ideal fit. If it's too big and you never feel that little drag, it will still work but it will not be repeatable if you unthread the chuck, and it can aggravate chatter problems and removing/intstalling the chuck sometimes. Basically, you're building a tool, build it to the best level of quality and fit you can possibly do. Then, you'll never have to worry about it being inaccurate or wobbly later.

So now, you've got the backing plate fitted to your spindle, and threaded on all the way up, the register bore has that tiny bit of drag when you thread it on, and it fits solidly with no wiggle-wobble. You know the fit, the one that makes you grin and remember why you like turning on the lathe. Now, your job is half done!

Remove the 4-jaw chuck. Give up the safety net, it's time to admit you've done a good job and you're ready to move to the next step. get out your new 3-jaw, and clean the register recess out, making sure there are no chips, and no nicks or gouges.

Set up for OD turning, and dial up your favorite facing and turning tool. Face off the new backing plate, just a skim cut, and turn the OD true. If it already has a register cut into the face, check it against your new chuck-hopefully it's just too tight to go on there, and doesn't fit yet. If not, and the new chuck just slaps up on the backing plate-face off that register. It's not registering anything and isn't helpful.

Now, carefully cut a new register to fit, or trim down the existing register to fit your new chuck-you want it to be a "line" fit. Basically, you want the register diameter of your backing plate to be exactly the same size as the register cut in the back of your new chuck. They will NOT fit together without a firm mallet tap, but it should take no more force than that!

Now, bolt your new chuck up to the backing plate, and let the bolts pull the chuck up onto the register evenly. Use a stamp or a punch and mark the chuck body, and the backing plate, with a punchmark to let you know if you ever have to remove the chuck from the  backing plate, how it goes back on. 

Congratulations! You've just fitted a new chuck to your lathe, and every time you spin it on and off the spindle, it will run true-with the minimum possible amount of runout.


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## rambin (Nov 21, 2018)

I appreciate you typing all that info in and I know your saying how easy it is but again im not a machinist only threads ive made so far are with a die nut ;p and I really dont wanna mess up a big expensive chunk like that.  this is why im hoping I can just buy something that's ready to spin on to the lathe? as I said shars doesn't have much to pick from there were only 2? and they looked kinda to cheap?  maybe someday i'll be up for a project like that wolfram  but i'll have to watch a hell of a lot more of mrpete first ;p  hopefully he can keep making videos for a lot more years


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## Wolfram Malukker (Nov 21, 2018)

Watching won't teach, or give you the confidence to do.

Backing plates are cheap, it's the chuck that bolts to them that is expensive.

Get a 6" square piece of plate 1" thick, and make your own plate-it's not hard, just write out the list of operations, and follow your list. Type it up here and tell us what you see yourself needing to do, to take a 1" thick square plate, and turn it into a 5" diameter backing plate for a chuck. Work through it, and it'll be in your hands in a few hours.

What tools do you have to work with? Can you give a list?


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## rambin (Nov 22, 2018)

well b4 I even think of attempting that I need to find me the right chuck was hoping i'd get some more people chiming in on my options, I only rushed into this post as I seen shars was having somewhat of a sale,  kinda leary about buying something unknown of ebay or amaz. I don't really know the name brands or what is or isn't good quality, the 4 jaw I have now is labelled south bend not sure how it ended up on my logan!  worse case scenario if I did have to machine the backplate id find someone to watch over my shoulder i guess


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## Al 1 (Nov 22, 2018)

Rambin,   It is good to get pushed once in a while.  I remember a time before  I had my home remodeling business.  I was doing some work while I was on vacation from my full time job.  I was doing home repairs and painting. We got started talking about doing additions on houses.
It seamed like something I would never do.  Well, I have been in business for over 40 years and I would venture to say anything is possible if you
put your mind to it. Try it on a piece of scrap like Wolfram said. Worst you can do is screw it up.  And then try it again. ---- Al


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## BROCKWOOD (Nov 22, 2018)

Getting a 6" wide x 1" thick plate locally means 20' long - but they will cut it to the lengths needed. However, there are online sites, such as onlinemetals.com that will gladly ship short lengths to your heart's desire at reasonable prices. I have leftover 5/8" x 6" that comes in handy from that shipped to my door source. I also have a lot of 1/2" x 6" from a 20' locally sourced piece that will get used too! Just weigh your price & availability, then dive in & let the chips fly!


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## BaronJ (Nov 22, 2018)

Hi Rambin,

Pre threaded backplates are cheap and readily available !  I've bought one from ARC for my Myford quite recently, it just spins on and seats on the register with minimal fuss.  It will take more effort to fit the chuck than it took to buy it !


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## Chuck K (Nov 22, 2018)

You don't really want to make a backplate out of steel. It tends to gall the spindle threads.  Blank cast plates are affordable if you want to finish one yourself, but it doesn't sound like that's what you want.  Just buy a 6" threaded backplate and fit it to the chuck of your choice.  You wanted to know if the cheap imports are any good. That depends on your expectations. They will hold a workpiece. They'll have some run out.  You have a 4 jaw so that shouldn't be a problem. The two piece jaws are definitely the way to go.


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## rambin (Nov 22, 2018)

I am willing to try it at some point for now Id just like to get some wisdom on what 3 jaw I should be looking at, I do like that 2 piece jaw idea as using soft jaws would come in handy sometimes... setting up the 4 jaw gets old fast!


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## rambin (Nov 22, 2018)

so from what i'm seeing it looks like id want a cast chuck ???  The forged seem to be a lot more? its an 80 yr old lathe after all how exact can it get or be...?  and after I find the chuck I like i have to buy an additional backing plate to match my lathe  1 and 1 half -8 https://www.shars.com/products/work...f+Centering+Scroll+Chucks&material=cast+steel


then add this?

https://www.shars.com/ap6-b-6-1-4-x...aded-back-plate-for-cs-fs-series-lathe-chucks

anything else i'm missing?  anyone own one of these brand chucks?


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## Chuck K (Nov 22, 2018)

You need a plain back chuck and a cast iron backplate like the one you linked. You would probably be pleased with shars chuck.  I have a small 5c 3jaw chuck that I bought from shars years ago that runs just about dead nuts.  I don't use it often,  but it's a handy little chuck.


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## Wolfram Malukker (Nov 22, 2018)

Yes, the shars chuck is OK for what you want-most 3 jaw chucks hold within 0.005" and will repeat within 0.005", so it's good enough for most 3 jaw work.

The steel plate backing plate wouldn't be for normal use-galling is a problem if proper steel isn't selected. But it is cheap and will give proper experiance in machining a backing plate.

Off-the-shelf backing plates are not going to give the best alignment or repeatability, some especially atrocious...when you machine them to fit properly you eliminate this issue.


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## Chuck K (Nov 22, 2018)

I'm curious...what would be the proper inexpensive steel to use for a backplate?


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## Wolfram Malukker (Nov 22, 2018)

Personally I'd use a pre-hardened 4140 or a grade 40 cast iron. To prevent galling you'd need to make sure that the two steels have a hardness split of 5RC or so-meaning if your spindle is hardened to 30RC, you want a 25RC or a 35RC hardness for the backing plate.


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## Chuck K (Nov 23, 2018)

I wouldn't use the steel regardless....but I'm thinking I could probably buy cast iron cheaper than 4140.


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## Wolfram Malukker (Nov 23, 2018)

Up to about 4", yes, you can. Over 4" the 4140 is cheaper.


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## wa5cab (Nov 23, 2018)

Rambin,

If you are going to go Chinese in order to save money, Shars is probably about as good as it gets.  And if you go with a plain back chuck and back plate, then the chuck body material doesn't matter.  Either the chuck or the back plate (or both) should come with instructions on how to fit the back plate to both your spindle and the chuck.  

Before you start with the chuck, I would suggest checking the runout of your spindle register (the unthreaded area between the threads and the flange, and the flat surface of the flange that contacts the rear of the back plate).  The bearings are, as you wrote, 80 years old.


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## rambin (Nov 23, 2018)

im thinking I will keep researching on this and hold off 20% sale at the moment but that's will come again im sure... im guessing to check the spindle properly I would need a last word ind.  I only have regular ones at this time...


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## Chuck K (Nov 23, 2018)

You might want to research indicators before you purchase a last resort.


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## WCraig (Nov 23, 2018)

Rambin, your thread triggered me to look at the 4-jaw chucks at Shars for my 70 yo Atlas 618.  I just clicked "Place order" a few minutes ago!

...  So, I'll blame you if the chuck isn't good!!  

Craig


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## Winegrower (Nov 23, 2018)

I suggest not getting the 3 jaw.   Just get two chuck keys, and make an indicator holder for the tool post.   You can center to any level of accuracy  you want, and pretty quickly.    Put the money into something that increases your capabilities.


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## BaronJ (Nov 23, 2018)

Hi Guys,

I mentioned earlier that I had just bought a backplate for my Myford, well here are the pictures of it.  I'll be fitting a 5 inch three jaw Bison chuck.
It came with a leaflet showing exactly what needed machining and full dimensions.




This one is cast Iron.  It does have a couple of rust stains, but they are of no consequence.


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## Wolfram Malukker (Nov 23, 2018)

That is a nice looking backplate-the rear spigot looks a bit long for both of my lathes but the threads look nice and the casting shows no voids-where did you get that one?


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## BaronJ (Nov 24, 2018)

Hi Wolfram,

It came from ARC Euro here in the UK !  Its Chinese of course, but the quality is very good as is the fit.
I know they do backplates for other machines, but you will have to check with them if they do one to fit your lathe.

 arceurotrade.co.uk


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## rambin (Nov 24, 2018)

WCraig said:


> Rambin, your thread triggered me to look at the 4-jaw chucks at Shars for my 70 yo Atlas 618.  I just clicked "Place order" a few minutes ago!
> 
> ...  So, I'll blame you if the chuck isn't good!!
> 
> Craig


well let me know how you make out, did you get the threaded backplate?  How bad was the shipping?


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## WCraig (Nov 24, 2018)

rambin said:


> well let me know how you make out, did you get the threaded backplate?  How bad was the shipping?


I've ordered the 4-jaw, backplate and 0XA QCTP set.  Shipping was $18 via UPS Ground.  Supposed to be delivered by next Friday although the Status is still "Processing" right now (Saturday).

Craig
Note:  I'm in Canada but I use a cross-border shopping service.  I get the stuff delivered to Lewistown, NY and then drive down and pick it up.  I think it is a $10 charge for a package this size.  Also have to pay $4 for the toll bridge.  Almost certainly have to pay tax at the border given the dollar value (although I have been waved through before).  Still faster and less expensive than having it shipped across the border directly to my home.


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## rambin (Nov 24, 2018)

that aint bad for shipping for something that heavy... every time I looked at there shipping for dif tools ive deleted my order


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