Mini-toolmakers jaws for small 80 mm three jaw chuck

[Paul Jones]

I made my own mini-toolmakers jaws for my small 80 mm three jaw chuck mounted on my mini lathe. A couple years later, I made a mandrel for holding the 80 mm chuck in a larger 6" chuck for my 12" swing lathe (see http://www.homemadetools.net/forum/c...0262#post72147 ). This expanded the capability for holding the chuck with mini-toolmakers jaws.

The purpose for these small jaws is for machining the short threaded ends of small cap screws in the 4-40 to 8-32 thread range. All my other lathe chucks and collets (ER16 on my Unimat SL and ER32 on my mini lathe) have jaws too deep to allow holding the threads with the cap screw head-end pointing towards the headstock. Some of the screw-end machining involves facing and drilling a small hole for adding a brass pad (protection from set screw marks on sliding parts). An alternative would be to bottle bore some soft jaw ER32 collets but I avoid this class of boring whenever possible.

The parts are based on a posting at MadModder - Index. The jaws are made from 12L14 steel and use 1/8" and 3/16" long stainless steel set screws with a 8-32 thread size. The short-length sets screws can be recessed into the jaws for safer operations. Each of the mini-toolmakers jaws are numbered and registered to each chuck jaw. The righthand-side set screw on each jaw is secured with Loctite 290 (green) while the top and left-hand set screws can be loosened for removing and replacing the small jaws without changing the bore alignment.

The first photo shows the mini toolmakers jaws attached to my 80 mm three jaw chuck (BTW the insert in the lathe tool is a T-15 HSS TPMW-221 from Arthur R. Warner Co. (Arthur Warner Co. | Specialists in High Speed Steel) and fits standard carbide insert tool holders). Adding the toolmakers jaws now allows more use of the original mini lathe 80mm chuck since being replaced with a larger 100mm three jaw chuck.

The last photo shows the lathe jaws with the mini toolmakers jaws still attached resting on an enlarged photo of the source of this idea from MadModder - Index.

I probably should have hardened these parts and then lightly grind the bore surfaces with a dremel tool attached to the the cross slide but that can be a project for another time.

Thanks for looking,

Paul Jones

P.S. I made a mandrel for the 80mm chuck to be held three or four jaw chucks used on my 12" swing geared-head lathe. The mandrel makes this small chuck with the mini-toolmakers jaws very useful and easier to install and remove (see http://www.homemadetools.net/forum/c...0262#post72147 ).

[kbalch]

Thanks Paul! I've added your Mini-Toolmaker's Jaws to our Machining and Workholding categories, as well as to your builder page: Paul Jones' Homemade Tools. Your receipt:

Mini Toolmaker's Jaws by Paul Jones

tags: lathe, chuck, jaw

[Okapi]

Hi Paul,
It's just a very simple thing you can add if the centering is not always repetitive with sufficient precision, two screws without head which push on the milled flat part in place of the sides, then you can adjut by opposite pressure the three jaws, mine is bigger than yours, but it stay under one tenth of a millimeter when I put them on the chuck before adjusting if it's necessary.

[Paul Jones]

Okapi,

Great advice and will come in handy as the parts eventually wear. So far loosening the just left-hand and center top set screws and keeping the right-hand set screw as is with the Locktite in place for removal seems to keep the alignment like new when reinstalled. However, closing the chuck jaws with the three mini jaws installed somewhat snuggly and making sure the milled flats are brought together very tightly (I milled these precisely at 120 degrees for this repeatable purpose), seems to guarantee alignment before finally tightening the left-hand and center set screws.

[Paul Jones]

Lately I have been shortening stainless steel cap head 8-32 screws by holding these with the mini jaws. I included two detailed photos. In the second photo I am using an old Starrett 1" steel rule with it holder to make the measurement. I much prefer using a DRO or dial indicator attached to a carriage clamp/stop to make these measurements but I just wanted to use the old Starrett tool.



Thank you for looking,

Paul Jones

[jjr2001]

I have been looking for a way to make brass or aluminum soft jaws for my chucks. I knew that the chuck jaws were too hard to drill with my equipment. I had seen a few other types but they were large and bulky. Your solution is elegant and now I have the method I will use for some "soft" jaws. Thanks

Cheers, JR

[lazarus]

Thanks a lot Paul Jones. I'm always running into"too small" parts for my jaws. Shims, soda cans, scraps, 10ga house wire, etc to make it work. Now I have another project.

[volodar]

To shorten or modify the threaded ends of hex headed (up to 5/8") small caps crews I use a 5/8" spare drill press chuck with attached cylindrical mandrel. This gets chucked in the three-jaw of my ancient c1900 conehead 14x40 Hendey. The cap screw, with a nut the size of the cap a suitable distance from the head (and in rotational register with the head) is then chucked into the step-down chuck. It has never had accuracy problems in whatever I'm "slapping together".

[Mr.Pete]

Hi Paul, I love these jaw add ons... just like jjr2001 ...I have been looking for a way to make brass or aluminum soft jaws for my unimat sl chucks also... wow I'm going to make afew out of brass ,aluminum and a harden set of tool steel.
Great job!

[Paul Jones]

Thank you Mr. Pete,

I have improved the usefulness of the mini-toolmakers jaws for my small 80 mm three jaw chuck by using the 80 mm chuck chucked into my larger 12" swing lathe http://www.homemadetools.net/forum/c...0262#post72147 . I now use the combination of the 80 mm chuck with mini-toolmakers jaws in a 6" dia. 6-jaw Gator TRU ADJUSTABLE chuck. The combination is repeatable within 0.0005" TIR and a wonderful way to hold small parts.

Paul