Four Jaw Chuck Soft Covers

All this four jaw work in the shop has me making all kinds of accessories for the darn thing. One thing that four jaw chucks do really well is hold onto things. Every machinist wants the things they clamp to not move with the least amount of clamping force. One of the reasons the four jaw chuck holds so well is most of them have serious serrated jaws. I can tell you that the chuck I have most certainly has teeth like a white shark. When dialing in the runout its fairly easy to push the part perpendicular to the serrations and actually drag the part surface along these nasty grippers leaving some really unwanted marks. I have formed up jaw covers before and have a decent selection in my box. Of course none of the covers I have fits the crocodile four jaw that I've been using lately. Time to make some covers. Its an easy job but with one or two subtle features.

 In this picture you can see the small serration within the larger that are causing me headaches. For my jaw covers I like to use thin copper sheet. I had some .030 thick sheet around so I cut out some blanks. The size of the blanks can be developed with a piece of paper if you want. I generally just run a tape measure around the jaw to determine the length of the blank. Cut a couple of extra for setup pieces while your at it. Invetiably you may loose one during forming or if you don't you will surely loose one under the machine at some point so an extra is great.

 Here is one jaw cover blank. I have marked a centerline on it to help align it for the initial bends. One good reason for using thin soft copper is you can easily hand form it. I like to use the actual jaw as a male forming die whenever I need to make a set of these.

Here we have the copper jaw cover blank clamped in my universal Kurt vise sheetmetal brake. The centerline was aligned with the center of the chuck jaw and clamped in the vise. The blank is automatically perpendicular to the chuck jaw because its sitting on the bottom of the Kurt vise.

This is the first bend. The thin copper is easy to bend by hand. The blank is now unclamped and rotated to make the second angled bend.

The first bend is indexed on the opposite side of the jaw. The reason for this is just for access to the blank for the bending.

Ok, two bends now and the blank is well indexed with the jaw. Coming up is one of the subtle tricks of making nice jaw covers.

If you examine chuck jaws closely you will notice they are concave so they grab round things well. What I like to do is preform this concave radius into the jaw cover before I make the next bends. You will see why in the next picture.

You see how the blank has poofed out a little from the angled surface from the radius forming. If you didn't add this preforming to the blank the first time you used the covers on something round it would distort the covers and try to make up that material from all the subsequent bends. Since these covers wrap around the jaws it makes for ill fitting covers that are sprung open and are loose.

Here we have the next two bends in nice and snug to the chuck jaw. I have slid the blank to the top of the jaw so I can mark the retention tabs. Notice I have positioned the blank just below the chamfer on the jaw. This will end up as their final position after the retention tab is bent.

I transferred the notch marks directly off the jaw. One cut with a pair of snips and they are ready to form.

Back in the vise for forming. Using the jaw insures the fit will be snug with all the bends indexed properly.

For the small tabs I just used a plastic caulking tool to bent the retention tabs around. These are the second subtle feature of jaw covers. If you don't add these then you will be fishing your jaw covers out of a filthy chip pan forever more. They always seem to fall out at just the right moment to annoy you.

I suppose you could cut off the excess if you wanted. I like the extra material to help guide the cover on the jaw. You can see the serrations made marks in the inner surface of the copper just from some light clamping. Already doing their job.

I cut two extra blanks but bozoed a bend, and snipped the wrong line for a retention tab on another. My tough luck that I don't have any spares now. "Life's tough, Its even tougher if your stupid." (John Wayne)

Thanks for looking.

Skeleton Aloris Holder

Now that I have been using the big four jaw chuck on the lathe I have to indicate everything. Looking through my selection on dial indicators I pulled a few likely looking ones out that I thought might would cover most of the four jaw needs. One thing is apparent right away that you need some range to the indicator. Just eyeballing things you can get within say .020 runout which is a .040 TIR (total indicator reading). The indicator needs a range that can accommodate this level of initial runout. I have a Blake Co-Ax that was rebuilt that I have been wanting to try. It seems to work well but I only have two styluses for it right now. The round shank makes it more of a hassle to mount in a tool holder also unless you use a boring holder with the vee groove. More on the Blake testing later.

What ever indicator you end up using it needs to mount to the machine quickly. For four jaw work its helpful if the tip lands on the center line in the vertical axis without having to look. If I was independently wealthy I would just dedicate an Aloris holder to the indicator setup and be done with it. At eighty five bucks a pop for a boring and facing holder it will be a some time before there is any excess. Looks like I will be moving tools around for a while. I suppose one could make their own holders if one wanted to. Great idea lets hit the shop. A quick scrounge around the metal rack yields a find of some likely looking cold rolled flat bars.

One thing with a holder that will be dedicated to an indicator setup is that it will never see any serious load or cutting forces. We could make it out of plastic or even a sturdy wood and it would be fine for holding an indicator. Well I'm tired of woodworking this week so its going to be metal today. Like most things around here it all starts with a sketch.

Not much material required to build this skeletonized holder. Two flat bars and a couple of pieces of 1/2 diameter round bar.

 Doesn't look like much right now but it comes together quickly. The pieces have all been milled to length and squared up to make the welding and rod spacing easier.

Getting things lined up and square to one another. The top plate under the c-clamp is special. For this to work properly the rounds have to be spaced accurately so the wedge of the tool post will clamp the holder.

This is the rod spacing fixture. I determined the correct spacing by adjusting the tool post on a standard Aloris holder until I could just barely pull it out of the tool post. I then put the two half inch diameter rods in the dovetails of the tool post and measured over the rods. The little step at the top is so the sides where the rods will lay stays square to the top of the holder when it all gets clamped up for welding.

Here you can see the welding fixture in action. If I measured everything right the rods should be at the correct spacing so the tool post will clamp on properly.

A few tacks and time to test it in the tool post. The tool post can exert huge wedging forces so I just want to gently see it my measurements are close to the desired fit.

Gingerly trying it out in the tool post. Looks like the right dimension.

Some nice hot TIG welds to hold it all together. There was actually some room between the inside of the rods and the tool post that I could have welded the inside also. It was pretty close, so instead of going for it and then cussing up a storm when some weld metal interfered I decided to skip the inside weld. This is the kind of stuff you learn the hard way. I've screwed up enough times to recognize a bear trap when I see it.

Check your set screw inventory before you tap the holes in the holder. Looks like I had 3/8 set screws in stock.

I thought about doing the holes before welding. The problem with that is there isn't much extra material in the holder to start with. For welding its best to weld when you have maximum material to act as a heat sink and provide some strength to resist the inevitable distortion forces from the welding. It was easy enough to do after the welding so it really wasn't a major factor.

Ready to try out. The set screws I had were kind of long so it looks weird right now. I'll get some shorter ones next time I make a McMaster order. This is the indicator I have been liking for four jaw work. Its a Starrett back plunger with .200 range. I may mill a centering groove in the bottom jaw so I can continue the Blake testing with this new skeleton holder.

One thing I decided to skip was the height adjustment screw that comes on the stock Aloris holders. For this holder I wanted to be able to move it up or down without fussing around. I set the center height so when the holder is all the way bottomed out the indicator plunger is on centerline. It feels strange to pick it up. The skeleton holder is so much lighter than the regular Aloris holders.

An interesting exercise that has got me thinking about how I might make my own holders from scratch. In the long run probably not much savings but it might be worth while for a larger run.

Four Jaw Chuck Keys

The new lathe in the shop came with tooling for several work holding options. Three jaw chuck, four jaw chuck, two face plates and a 5C collet closer. After I got it wired up I mounted the three jaw chuck. The chuck had soft jaws on it that I took off and mounted the hard top master jaws. The main jaws in the chuck body seemed a bit wiggly to me but I just ignored it for the time being. Well it turns out the three jaw chuck is pretty whupped. It runs out a fair amount and the jaws cock a some near the front of the chuck which is a major wear signal. It makes sense in hindsight that there were soft jaws installed on the chuck from the previous owner. This would be the only way to do decent work with this particular chuck. Unfortunately for me its not an adjust through type chuck. The backing plate is integral to the chuck and non adjustable.

So I went ahead and spent some time cleaning up the nice Rohm four jaw chuck that came with the machine. Like most four jaw chucks it looks like it has not seen much use. Most everybody prefers the self centering three and six jaw chucks for speed. I generally agree with this myself. For a large part of the typical lathe work centering within five grand is fine. If you need it closer than that you make a minor adjustment with the adjust through feature and then your dead on.

Like I said I generally prefer three and six jaw self centering chucks. Too bad I don't have one right now. So I sucked it up and mounted up the big four jaw and started doing some jobs with the machine. In the pile of  tooling I got with the machine there was a vacancy where the four jaw chuck key should have been. I figure oh well its easy to get another one, I'll just buy one. So I start looking around to see what is out there. I measure the screw on the chuck and discover its a funny size. Like metric funny size. Still it shouldn't be that big of a deal right?

This particular chuck has male square screws instead of the much more common female type. They are metric to boot. Finding a chuck key was starting to look like a real challenge. The Rohm website even shows the typical female socket adjuster screws. Where the heck did this alien chuck come from?

Twenty years ago on one of my tool buying sprees I bought a set of eight point sockets for a single job. I could have just bought the one socket I needed but no, I bought the whole set. Well funny thing is I have used the heck out of this set over the years. They fit all kinds of things you run into so the expense wasn't wasted this time. One thing I use them for is driving taps where you need a long extension to reach a hole down a hole. Good thing I had them now. Its the only thing I had to drive the square drive screws on the four jaw chuck.

This socket setup is a sub optimal tool for adjusting a four jaw chuck. Its an inch size so it doesn't fit the square very well. So faced with the non availability of a chuck socket I decided to do the next best thing which is make some. If your going to the trouble to make a square socket wrench you might as well make two. There is a good reason for having two which I will tell you about later.

I poked around the metal rack and came up with some heavy wall steel tubing that fit the recess in the chuck. To make the 10mm square I machined a .400 wide slot through the end of the tube and then created two opposing shoulders that were .400 apart. I then inserted two "keys" into the shoulders and welded them in.

This is a great job for a dividing head or a collet block where you can easily flip the part 180. I faced the end of the tube by rotating the dividing head. In case your wondering why I didn't use a 5C collet block the reason is I don't have a 7/8 collet which is what this tube OD was.

The first .400 wide slot is milled slightly past center of the tube. When you rotate the part 180 you get to see how good of a job you did picking up the center line of the tube. Whatever error there is is doubled when you rotate it 180.

The key step milled in one side. I had a small mismatch between the two sides. Not enough for me to get excited about on a weldment.

Here the keys have been welded into their key slots. Its starting to look like something. The weld prep was important here since I am machining off most of the weld reinforcement. I beveled the edges of the key slot so there is some weld filler metal still there after machining.

One really nice thing about four jaw chucks is everything gets indicated. You actually do better work when you use a four jaw chuck. This is a perfect example of why its important. When I machine the keys off I don't want to go below the original tube surface since the weld prep is minimal. If the part runs out a little there will be a witness step when all the key and surface weld is removed. Your only choice is to go deeper which in this case I really want to avoid. You are fighting runout against the removal of all the key and weld. This all goes away when you indicate and zero the tube accurately.

Turning the OD of the keys to the same diameter as the main tube.

Okay so now we have two chuck keys with square sockets in the end. On the shorter one the square closed up a little from the welding. I compensated on the longer one for the weld shrinkage but I still have to fix the shorty. The only really effective way to do this is to broach the ID of the square. No 10 mm square broaches in the tool room so I will have to improvise. The amount to remove was small. Only .005 per side to get the fit the way I intended. For this job I had to pull out my vertical broach. I don't use this tool very often but when you need it you really need it. I couldn't file the ID very well because the square is blind. Filing into a blind corner is pretty tough to do and a sure recipe for a bozo job.

These are what industry calls slotting tools. Bridgeport used to make a slotting attachment that went on the back of the ram for vertical slotting. Nobody does it anymore with the availability of cheap broaches and the easy availability of EDM work. The tool on the right is an actual Bridgeport brand slotting tool. The one on the left is my improvement. The eccentric shank locates the thrust of the tool more on the center line of the spindle. The body is just steel with a high speed tool bit silver brazed into a mating slot. There are side relief angles ground into the edges for back clearance.

First step is to get the part clamped up in a sturdy setup and straight with the machine axes. There is a parallel under the part to take to thrust of the quill.

Next is to mount the tool in the spindle in low gear. The cutting edge is aligned with the machine axes also. It looks like I didn't get any pictures of the actual broaching. Its a simple enough process. I took a couple thousandths DOC per pass, stepping over half the width of the tool much like a planer would. I took equal amounts off each of the offending faces until I got the measurement I was looking for. In total I scraped off  about .004 per side.

One bad thing about big chucks is they don't close down on small diameters very well. I didn't have a 3/8 diameter 5C collet on hand either or I might have used the collet block. As it was I found a better way to do it anyway. Using a V-block in the four jaw allowed me to only need to use one of the jaws to put a new part it the chuck. Once the rod and v-block were centered it was in and out in a flash like a collet closer or three jaw.

These are the cross hole rods for the chuck sockets that are being radiused on their ends. Material is 3/8 diameter cold rolled.

Ready for welding. I radiused the top side because this is where the hand comes into contact with the tool.

I thought this worked out well to weld the rod into the body of the socket through the end hole. No weld cleanup and it really cant pull the rod out of position from the weld shrinkage.

Finished and ready for lots of four jaw work. The two sockets allow you to work the jaws against one another and dial in the indicator. Here is a link to a great to the point video of the concept of two chuck keys.

Conical Washer Forming

All this wood work going on around the shop lately motivated me to install a set of double doors between the art studio and the metal working shop. We found some interesting solid semi Moroccan style doors on Craigslist a few months ago that we set aside for the project. Meanwhile I squirreled away all the lumber and fittings we would need when the moment of truth came to hang the doors. These were bare doors without a jamb. I have installed a few doors with pre-made jambs which is pretty easy. This is the first set of double doors sans jamb that I have done. To complicate things slightly the folks that built the wall added some extra thickness to the wall for shear strength which forced me to make a custom jamb set for the doors.

One of my construction buddies gave me a good tip for hanging heavy solid doors. He mentioned that the hinge screws should go all the way through the door jam and into the trimmer stud if possible. It makes perfect sense when you lift the dead heavy doors even once. Each one weighs maybe sixty or eighty pounds all of which is screwed to some flimsy jam lumber with #10 screws. I took his advice and used long screws where I could.

My problem was the countersink in the mortise hinge. The screws I used have a spline drive on them to make it less likely to cam out when installing them to high torque levels driving them deep into the trimmer stud. Unfortunately the heads were a whisker too small and just passed through the stock holes in the hinges. What to do. I could get new hinges or new screws all of which require a trip to the store on a holiday.

What was needed were some custom conical washers. At least that's how I decided to fix my current dilemma.

You can see in this picture the head just passes through the hinge countersink. These screws are 3.5 long with a spline drive.

A quick forming die made from some steel flat bar. This was just drilled clearance for the screw and countersunk 82 degrees to match the screw head. The countersink top diameter is the before forming washer OD.

I did have some nice #10 stainless AN washers in stock. They just sit on the top edge of the countersink helping to center them.

The screw is the punch used to form the washer. I pulled down from underneath the vise so the screw and washer didn't move when I smacked it.

A few love taps with a small hammer and now I have some special washers.

The screw fully seated with the formed washer.

You can even see the imprint in the washers of the small splines and text from under the head of the screw.

I deepened the hinge countersink to accept the screw with the new washer. It acts like a small spherical washer and allows the screw to center itself in the hole. It saved me a trip to the store and allowed me to use the heavy duty screws driven into the stud.

A simple job but worth sharing here. It keeps you all guessing as to what will come next around the shop.

Thanks for looking.