Index model 40 drill chuck

[Vince D]

Hello,
I have an Index model 40 vertical mill. I know there are some people on here with the same mill. My question is how are you guys mounting a drill chuck on your mill. I have the b&s #9 taper spindle and I have collets from 1/16"-3/4". I have a Jacobs drill chuck that has a 1/2" straight shank but the when I draw it up in my 1/2" collet it doesn't run anywhere near true enough to drill with. I've been drilling with the drill bits in collets but would like to have a drill chuck to mount that would run true. Any hints or pictures of setups will be appreciated.
Vince

[Finegrain]

I'd just get a MT4 to JT-whatever arbor and turn the Morse end down to B&S #9.

Regards.

Finegrain

[Vince D]

Are most of the Morse taper drill chuck arbors soft enough to turn down?

[Finegrain]

Sure. Even the "hard" ones will cut no problem with carbide.

Regards.

Finegrain

[Vince D]

Ok, it looks like I'll be turning a MT4 drill arbor this weekend. I looked in my junk box and found a surplus one. I was just wondering how other people were mounting a drill chuck with a b&s #9 taper chuck. I've never seen a drill arbor with this taper.
Vince

[JND]

Sorry,I have been offline and busy for awhile,didn't see the post. I have a number 9 adaptor that turns into a male taper that the chuck slides onto.I'll try to get a picture on this weekend.
Nick.

[Robert Campbell Jr.]

Vince, the majority of chucking that I do in my 40H Index, is in a B&S #9 taper, Universal Eng. "Z" collet chuck. All run true, including the Jacobs 14N drill chuck with 1/2" shank. For the 40H, double taper Univ. Eng. collets, ("Y" to .56", "Z" to .81", "ZZ" to 1.1" and "XZ" to 1.6") have adequate gripping power.

In addition to my "Z", I've seen used B & S #9 taper collet chucks in "Y" and "ZZ", priced at a good value.

In a quick check, the first collets I found are 6 of the large "XZ" that appear to be in good condition, at BIN $24.99 or $4.17 each.
http://cgi.ebay.com/6-DOUBLE-TAPER-C...3A2%7C294%3A50

I really prefer wrench's at the spindle nose, swapping only small collets, to having a bunch of full B&S #9 taper tooling that must be changed by loosening, beating on and then unscrewing the draw bolt.

Individual collets are much cheaper than full shank taper tooling and I've found the concentricity of collets to generally be better than end mill holders.

Bob

[machmat]

Originally Posted by Vince D

Hello,
I have an Index model 40 vertical mill. I know there are some people on here with the same mill. My question is how are you guys mounting a drill chuck on your mill. I have the b&s #9 taper spindle and I have collets from 1/16"-3/4". I have a Jacobs drill chuck that has a 1/2" straight shank but the when I draw it up in my 1/2" collet it doesn't run anywhere near true enough to drill with. I've been drilling with the drill bits in collets but would like to have a drill chuck to mount that would run true. Any hints or pictures of setups will be appreciated.
Vince

Me too, I purchased a book from Wells/Index for the 40 but it has no wiring information. I could really ue some wiringi information.

I used both, a 3/8" chuck mounted on a 1/2" arbor, held either by a half inch collet or tool holder. And a larger chuck on a #9 arbor. Both work well with little run out.

[Dutchman#2]

The logical solution is to lathe-turn a 9BS arbor for your drill chuck.

The way you do that is to chuck up a 9BS shank in your lathe with the large end by the headstock between centers or supported by the tailstock and mount a dial indicator on the compound slide and run it back and forth until your compound slide is zeroed on the 9BS shank. The proceed to manufacture a couple/few 9BS blank arbors for future use.

You don't need a continuous 9BS taper. You can do an abbreviated shorter "stub" taper as you'll have a drawbar holding it in place. If you have a small lathe that can't do a long 9BS tapered arbor then just do a shorter arbor. Or a tapered surface with an interruption in the middle. If you can't do something one way then try another way.

I did this when I got a Criterian DBL202 boring head and needed a 9BS arbor for the Index Model 40. Using a 1903 Von Wyck lathe 15x60 to turn the 9BS arbors. Turned out ok-fine and was used for many years.

My Index came with a 9BS drill chuck arbor and an old Jacobs heavy duty 1/2" sleeve bearing chuck. I eventually put new jaws and split nut in it and cleaned it inside.

I'm also using an ancient Y-collet 9BS arbor with a large nut that tightens the collet into the arbor. I have collets from 1/8" to 1/2" and 9BS collets for 1/2", 5/8" and 3/4". Worked pretty good for 25 years. The Index is now semi-retired as I bought a 1993 Enco 1525 earlier this year.

A solution to drill chuck arbor tapers is to snag a threaded Jacobs chuck. There are 1/2" medium duty chucks with 1/2-20 thread and larger ones with larger thread. Sometimes its easier to go this direction than mess with tapered drill chuck arbors that defy reproduction (easily!).

My Index made it to the big times....... scroll down the page to see my Index Model 40H.
http://www.lathes.co.uk/blankbuxton/



Vince D -- If I had a drill chuck that was that bad in a mill I'd throw it in the street and watch trucks run over it. (or something equally entertaining that didn't involve puncturing tires and irate truckers).

When I first got my Index in Los Angeles circa 1982 I hit whatever used tooling/machinery stores I knew of on a regular basis like Sam's Used Tools in North Hollywood. I found all manner of 9BS milling cutters, 9BS to 2MT reducer, 9BS to 7BS reducer, and a couple of the Y collet arbor chucks. Some of the 9BS end mills had a tang instead of a drawbar thread. I bought them anyway and cut off the tang with a die grinder. Most of that stuff was Pratt & Whitney used during WW2 in the aircraft business around Los Angeles. Once in a while you'll find 9BS arbor stuff on fleabay. I haven't decided what to do with my Index yet, sell it or keep it or trade it away, but I have to keep all the tooling with it for whatever future it has.


Dutch

[machmat]

Nice, older than mine, I think.

I don't know much yet about the machine, but each day I am learning a little more. The bed is worn, not bad but you can tell at the end of the travel it gets tighter.

Mine has a manufacturer date of 1943 s/n 1835-H. I went to Tony's UK site and saw your machine, nice. My serial number has not 40 in the front, but I am assuming that the H means it is the same model?

Here is a before picture, it was stuck away in a back area of a company, not really used for the past six years, but other than a little surface rust and a lot of dirt, not bad. Everything worked.



This unit also has the power downfeed which isn't working, and power crossfeed, which does but needs some work.

The mill came with some tooling, but I have been able to pick up a bunch of stuff via ebay and some locally in B&S #9. Including a set of tool holders and collets new from Jeff Beck http://www.tools4cheap.net/ they also sell on ebay. I have this hate/hate relationship with chinese products, but these were excellent grade and I even went back and purchased a set of Morse 3 collets.

Currently I am making a replacement cover for the downfeed screw.



The original cover was warped, cracked and missing the part that goes around the helical screw.



I saw cut to rough size a piece of 1/8" CRS and then set it up in the mill to trim to finish size.



Then on to the rose bud for a little forging.

I have so much I would like to talk about, questions to ask about this machine.

All of the leadscrew nuts have a lot of backlash and should be replaced. I don't know if I am up to this task.

The literature talks about "permanently lubricated bearings" This machine is now seventy years old...... how long exactly is permanent?

I am running the mill on a VFD, and it is not working right. The motor gets hot at normal 60 cycle speed with no load. There is this switch, which is a marvel of engineering. I have invested hours working out a schematic for this switch. It takes in L1, L2 & L3 and sends it out to a two speed motor, forward and reverse and off. So one wiring into four different wirings plus off, all through a single knob, nine gang, five position switch. I feel like there is something not right but I can not find the problem. The VFD guys say to dump the switch altogether.



From your images I can not tell if you have the same switch?

I am new at this forum stuff, it is proper to post more than the original thread?

"I haven't decided what to do with my Index yet, sell it or keep it or trade it away, but I have to keep all the tooling with it for whatever future it has. "

I know how you feel, I WANT a J-Head Bridgeport, but the cost and availability is not within my budget. This seems to be a pretty servicable machine and a lot better than what I had before, which is one of those chinese mill/drills. I also will keep all the tooling with the machine, and now I have a pretty good pile of tooling. Including about two hundred pounds of B&S #9 tang shanked endmills which I am attempting to cutoff the tang and thread the ends to use a drawbar. I wouldn't mind a little input on this task?

[Dutchman#2]

I can help with the wiring and motor and switch.

Take them all off and throw them out.

I run mine on a 110v 1/4 hp single speed motor. For 25 years. I guess a half-horse motor would be mo'better but you don't need all that crap on there. It isn't factory stuff anyway.

You have the different shaped knee than mine. Mine was made in 1942 so we know when the one was changed over.

All those wires and things make your mill look like its on life support:-)

My Enco is 3 phase with a rotary converter. The switch you describe sounds like mine. Hi-low in both forward and reverse plus off is 5 position rotary switch. I'd bet its wired the same.......!! Go to the Enco website. On the opening page, left side is a link to their manuals. Get the manual for the 100-1525 mill. 8x36" table. There are a couple manuals. In one of them it has the wiring including the switch.

Lubricate your ways on the saddle and table. There should be oil cups front and back of the table and two oil ports on the saddle over each of the dovetail ways. Lots of oil and then adjust the gibs.

Backlash isn't the end of the word by any means. You learn to take up the slack. After a while it'll just be automatic in how you crank things around.

This is the link to the rotary switch on my Enco. The 4 white wires are the 220v 3 phase input. One is ground.
http://images49.fotki.com/v1494/phot...55/pc05-vi.jpg
Let me know if you can't get the Enco wiring diagram and I'll scan my paper copy. Its not the greatest but it may help you out. My email is swede1894 at gmail.com

The tanged 9BS end mills can be used without a drawbar. I used a 1/4 hp electric die grinder with a thin cutoff wheel to remove the tangs. I used a block of oak under the cutter to give it a smack upward to seat the taper.

A 2nd suggestion is to make a simple jig to position a pre-made threaded doodad (technical term) and weld it to the end of the endmill tang. If you do this I'd suggest a chop saw to remove 1.5 inches (or so) off the end of the 9BS shank to make room for this threaded doodad. Not that much work if you figure out a jig to align the doodad with the endmill for welding. You could also utilize an undersize drawbar so everything fits down the spindle. Make a brass bushing for the top of the splined shaft to center the drawbar and provide a little "bearing" for the drawbar tension. Two hundred pounds of 9BS endmills? Dang! Yeah, I'd figure a way to use them, too.

I've run my mill 25 years without doing squat to the spindle bearings. Once in a while I think about how cool it would be to take the spindle out and clean & lubricate everything. Then I yawn and find something else to do.

Dutch

[machmat]

"I can help with the wiring and motor and switch. Take them all off and throw them out. "

You might be right, I am not ready yet. I am thinking I should be able to figure this out. Spent a decade as a field engineer installing and repairing central office telephone and DC power equipment, so I have lots of experience running my fingers through multicolored wires. I have to admit I find this 3PH stuff is confusing and now with the fancy VFD in the mix I am even more confused. Some of the guys on the forum say that I NEED to eliminate all the switches between the motor and the VFD, and let the VFD do the power control. First because this is the right way to do it and second because using the switch will fry the VFD. I accept that opinion, so for now I just leave the switch in its run, high, forward position and do the control with the VFD.

The gang switch:



You can see the straps that connect one gang to another, this makes sense, and these exist all the way around the gang. But what you can't see is there are connection that pass through the gang from one side to the other that you can't see. This really is a marvel, some engineer made his bones on this design. Then add a few jumpers because I guess the designer couldn't figure a way to make some connections work internally. This switch, I am thinking, is the key to how the motor works, is wired. It looks original, which is hopeful. You switch does the same job, who knows, I will see if I can locate a wiring diagram, thanks.

So you have a Enco with two speed three phase motor?

I understand that the VFD can do the speed change job, but I wonder if you have better power using the low speed windings at 60 cycles, than you do using the high speed windings at 30 cycles? My low speed does not work the way the VFD is wired to the machine. It starts but there is no power, slow to pick up speed and I can stop the spindle with my hand. It is like I am only getting power to two of the three legs. Just Confusing.



So you have an Enco mill also? Keep them both just because you have the space?

[machmat]

"The tanged 9BS end mills can be used without a drawbar. I used a 1/4 hp electric die grinder with a thin cutoff wheel to remove the tangs. I used a block of oak under the cutter to give it a smack upward to seat the taper.
"

Oh yes, I got the deal of the century on some B&S tooling. Fellow had purchased a bunch of stuff from I believe an aircraft manufacturer and I guess the real money was in the machines not the piles of old tooling. A few months earlier there was another fleabay seller that also had a pile.

Here is a shot of about half the total:



I have two milk crates layered with end mills and cardboard all sprayed down with CRC full, I am guessing each weighs about a hundred pounds.

They all have tang ends. I tried to seat them but it was of no use. They would run for a while and then drop out. I never liked the whole tang method. Have these on the drill press. They seem to work ok in a drill press where the pressure is straight up the axis of the bit. But with an endmill the stresses are all over the place.

My plan.... we'll see if this works or not, is to cut off the tang. Then mount the cutting end of the mill in a sacrificial plastic collet that I can hold in a three jaw chuck on the lathe. The tang end supported by a steady rest and then drill and tap the end 1/2"x13tpi just like the other B&S tooling. I have already cut a couple using the bandsaw just to see if they would cut. Was an easy task, so the tang end must not hardened.

I would think that if I can get this concentric within a couple of thousandths it will work just fine. THOUGHTS?

I am having some fun with this whole forum thing, so I will try to document.

Then a little while ago I was able to pick up a couple of boring heads. I already have a chinese boring head, straight shank, and while it is functional, the quality of the tool is not good. I can get good cuts with it if I am really careful and tighten all the gib screws before making a cut.



"Backlash isn't the end of the world by any means. You learn to take up the slack."

I agree, but it is challenging to have an endmill make contract and then grab the work piece and pull the table .060". While working to one side of the lead screw with an old lathe has become second nature. Trying to get out the backlash in an X, Y direction is proving to be troublesome. Also there is no clock spring on the spindle, so Z axis slop is making me crazy. You plunge into some stock, and then the spindle will drop. I removed the spindle lock screw and replaced it with a bolt so that I can use a long handle wrench to get more tension control. This has helped, I can micro adjust the pressure so that the spindle movement is still pretty easy but it stays put, gravity is not enough to drop it into a work piece.

Reminds me when I was a kid, my first car was a Willies station-wagon. The steering wheel would turn about thirty degrees with nothing happening. Which made driving at on the road a bit of a challenge. You would have thought that would have prepared me for an old well worn mill.

[Dutchman#2]

I would think that if I can get this concentric within a couple of thousandths it will work just fine. THOUGHTS?

Mo'better to have drawbar support so I'd say yes, give it a try. Some slight mis-alignment could be dealt with by having a slightly undersized drawbar for the length of the shaft for allowance.

I agree, but it is challenging to have an endmill make contract and then grab the work piece and pull the table .060".

You need some time to learn about climb milling and conventional milling.
http://images.google.com/images?hl=e...&aq=f&oq=&aqi=

Also there is no clock spring on the spindle, so Z axis slop is making me crazy. You plunge into some stock, and then the spindle will drop. I removed the spindle lock screw and replaced it with a bolt so that I can use a long handle wrench to get more tension control.

The only broken part I've seen on an Index Model 40 is the squeeze part that locks the quill.

You see that scribed line up and down? Somebody else put that there a gazillion years ago. That's the spot where the tension locks the quill. I'd bet yours has excessive wear so the quill lock doesn't tighten enough. Mine has a sockethead cap screw and I keep a 3/8" allen wrench right there to tighten and loosen it. I don't torque it down. I respect that scribed line.



I have a suggestion but its risky. You'll have to pull the whole quill out of the housing so you can widen the slot that pulls together to lock the quill. That is if that's why the quill don't stay put.

Also, you don't leave the quill lock loose when milling. You tighten it. To put your mill deeper into the work you raise the table. The knee on my 1942 Index can hold .001" all day every day and has since 1942.

You do need to adjust your table and saddle gibs.

In college in 1970 I took a year of tool-machine engineering at Los Angeles Pierce College. The instructor was a US Navy machinist mate in the Pacific during WW2. Italian guy from New Jersey (where else?). Best dang teacher you could ever have. That man knew how to do things because in the middle of the Pacific you didn't have the luxury of saying "I don't know how to do that" or "I can't do that". Padilla was his name. Had that Italian east coast shuffle. Great guy.

He'd deal with the slack on the Bridgeport table by shoving the slack out of the table and then climb mill keeping the slack behind the cutter.

For over 30 years I was running a 1903 Von Wyck lathe 15x60. Dealing with slack is like your mother-in-law. You find ways to make sure it stays away. Did the same with a Clausing 6300 that had a little too much slack in the leadscrew/feedrod. You just drag your hand on the carriage wheel and keep the slack behind you.

Your mill may not be as worn as you think. Every machine has a soul. Every old machine has an old soul. It doesn't have to get used to you. You have to get used to it. Its like it was female. Treat it that way and you'll learn faster with less frustration.

It occured to me that the quill screw you were talking about might be the one at the bottom below the quill downfeed screw. Mine has had some expedient mods done as it has no power downfeed parts anymore. So I installed the 3/8" sockethead and jam nut. I think I had to turn a 60 degree point on it to mate into the screw but it was a long time ago.




Dutch

[Dutchman#2]

You asked about this and I almost forgot:

I am running the mill on a VFD, and it is not working right. The motor gets hot at normal 60 cycle speed with no load. There is this switch, which is a marvel of engineering. I have invested hours working out a schematic for this switch. It takes in L1, L2 & L3 and sends it out to a two speed motor, forward and reverse and off. So one wiring into four different wirings plus off, all through a single knob, nine gang, five position switch. I feel like there is something not right but I can not find the problem. The VFD guys say to dump the switch altogether.

My Enco is 1.5 hp 500 watts and 1,000 watts. The high-low switch and the subsequent speeds work flawlessly. 100 rpm to 3500 rpm. At the higher speeds that sucker sings! The wind up draws down the rotary converter for a few seconds and then it takes off like a jet fighter in afterburner. Its impressive, really.

You can't use your high-low switch with the VFD. I recall that tidbit when I was trying to decide for mine. I can't say I know about 3 phase, but I know more than I did before. I put more faith in the rotary converter than the "electronics" of the VFD. I had a clean free 220v 20 amp 1 ph. circuit right in the corner of the shop. I'm not sorry. I wanted the 10 speeds of the 3 phase motor. The Grizzly version of my mill is 1 ph and 5 speeds starting at about 230-240 rpm. That's not low enough. Even the Index runs darn slow in the bottom speed. You need that slow speed when drilling steel with larger drill bits.

Bypass your rotary gang switch altogether and you'll find your VFD works fine.

Dutch

[John in CA]

Originally Posted by machmat

I have so much I would like to talk about, questions to ask about this machine.

All of the leadscrew nuts have a lot of backlash and should be replaced. I don't know if I am up to this task.

I think you could do it. Here's what I did:

First, undo the X-axis leadscrew retention screws, that fasten the leadscrew flange to the table. Unscrew the leadscrew and remove. Loosen the gib adjustment screws and slide the gib out. The table will now lift right off the saddle. You can do it by hand, if you're careful. The X-axis leadscrew nut will be visible on the saddle, held down by two (if I remember) 5/16 - 18 screws. If you're lucky like I was, there will be a layer of 70-year old gunk forming a "pocket" around the nut that the new one will seat right back into when you're ready. Replace the nut, and then place the table on the saddle. Slide the gib in and adjust until you can push the table back and forth by hand, but so that there's a light drag. run the leadscrew in until it engages the nut, and screw in until you can refasten the flange. Then run the table throught it's range of travel to make sure it doesn't bind anywhere.

Gotta get back to work now, a little later I'll go over what I did for the Y-axis on my "little beast". I didn't replace the nut as I thought a new one would be prohibitively expensive from Wells-Index, so I contrived a backlash adjustment mechanism. I'm in the process of producing some SolidWorks models of what I did, and would be happy to email them to you if you'd like, when I'm done.

Hope this helps,

John

[machmat]

To Dutchman 2 " You need some time to learn about climb milling and conventional milling.
http://images.google.com/images?hl=e...&aq=f&oq=&aqi="

Thanks for the link. Climb milling in nearly impossible with a sloppy lead screw, or am I wrong here? So conventional is the way to go where you have the table loaded in one direction, taking up all the slack. Still this really is no way to live. I have tensioned the lock on the X and Y a little tighter than I would normally and it helps some.

" The only broken part I've seen on an Index Model 40 is the squeeze part that locks the quill. You see that scribed line up and down? Somebody else put that there a gazillion years ago. That's the spot where the tension locks the quill. I have a suggestion but its risky. You'll have to pull the whole quill out of the housing so you can widen the slot that pulls together to lock the quill. "

The bat handle knob that tightens the quill was loose, I removed it and found a socket head allen screw with a handle attached with a set screw. I am not sure this is original or not. I am thinking not because the handle actually has a tapered socket, and the socket head screw was turned down, but not tapered. So it wasn't a good fit. I took this out and replaced it with a hex head 1/2" x 13 tpi bolt. Now I have more control with a ten inch long wrench than I did with a two inch long ill fitting set screw handle. I was thinking the same thing about removing the spindle and recutting the slot. But think about it for a minute. Where is the wear point or change, the spindle got smaller over the years? Or the metal in the support column stretched? Or the spindle going up and down wore away metal? So even though this slot does look very very thin, I am thinking it is original in its dimensions. Sure enough with the bolt and a wrench I have no problem setting tension, and locking the spindle if desired.

"He'd deal with the slack on the Bridgeport table by shoving the slack out of the table and then climb mill keeping the slack behind the cutter. "

I don't understand, if I am "climb milling" then the cutter is trying to pull in the direction that the table is going, so that when it gets a bite it will pull to the point of using up all the backlash. In reality, or at least in my reality the end mill grabs, get way to meat and like anyone taking too big a mouth full chokes, in the case of the milling machine we get really poor finish, a lot of jumping around. I get the feeling from your statement that I am missing something here?

" It occurred to me that the quill screw you were talking about might be the one at the bottom below the quill downfeed screw. Mine has had some expedient mods done as it has no power downfeed parts anymore. So I installed the 3/8" socket-head and jam nut. I think I had to turn a 60 degree point on it to mate into the screw but it was a long time ago. "

I have the same, but the original bottom screw that takes up any slack in the movement of the acme screw. If I loosen up the spindle I can move it up and down about sixty thousandths, just a guess not measured, and all the movement is happening in the bronze nut that the acme screw is running in. The helical gear to acme screw seems to be tight, and the movement of the acme screw in the housing is tight.

These are all wear items, they are suppose to wear and over the course of three score and six years, wear they have. Has anyone gone through the process of replacing these lead screw nuts?

[machmat]

To Dutchman #2 "You can't use your high-low switch with the VFD. Bypass your rotary gang switch altogether and you'll find your VFD works fine. "

I too am not comfortable with my understanding of the VFD, and have been told if I do use the switch I will smoke the VFD. Maybe a rotary converter would have been a better option........ don't know. In fact there is three phase close, for the price of the converter I could have pulled into the shop. I am not ready to give up yet on the VFD, I still would like to have that ability to adjust speeds on the fly, which does work and it really nice.

[machmat]

Originally Posted by John in CA

I think you could do it. Here's what I did:

Hope this helps, John

It does, we are going to have to chat some more. Bottom line is that I would like to have this mill working as good as I can make it. I was told when I ordered a manual that Wells-Index will still supply parts for the model 40, which is pretty exciting. I now have a parts list so I am going to inquire, maybe new lead nuts aren't prohibitive.

I have never tried to cut an inside acme thread, that too is an option.

Also I read an article about a guy who cast a nut right on his old screw using a babbit bearing method. The material is softer than brass or bronze but for the kind of use I would be putting the machine through it might work just fine. I have some fancy plastic material that might work way better than brass and is self lubricating, which means no oil. No oil no grit, less wear. Al things to think about.

[John in CA]

Originally Posted by machmat

It does, we are going to have to chat some more. Bottom line is that I would like to have this mill working as good as I can make it. I was told when I ordered a manual that Wells-Index will still supply parts for the model 40, which is pretty exciting. I now have a parts list so I am going to inquire, maybe new lead nuts aren't prohibitive.

I have never tried to cut an inside acme thread, that too is an option.

Also I read an article about a guy who cast a nut right on his old screw using a babbit bearing method. The material is softer than brass or bronze but for the kind of use I would be putting the machine through it might work just fine. I have some fancy plastic material that might work way better than brass and is self lubricating, which means no oil. No oil no grit, less wear. Al things to think about.

I'd be very interested to hear what prices they give for the nuts. When I went about fixing mine, I happened to have a 2" dia. / 5/16" thick drop of 932 bearing bronze in my toolbox. I also had never cut inside acme threads, and relished the prospect of a new challenge. Turns out it's not all that hard either, even given that for the Y-axis they're LH threads.

I've heard of the trick of casting a nut right on the screw. I myself lack the expertise to do it, but it sounds cool.

What I did was to cut a secondary nut to jack outwards, with setscrews, against the face of the old nut. To do this, I needed to find a way to pin the new nut to the old one. Thing about that is, these nuts have absolutely no real estate on them to run pins through. So I made a block to mate to the underside of the nut, that would use the same screws used to bolt the nut to the saddle. In this block I reamed a hole for a .25" ejector pin, that would run through the new nut and into the block, and "capture" it to the assembly.
The hole in the secondary nut was reamed for a light sliding fit, and I put setscrews on either side of the threaded hole, that bear against the face of the old nut and jack the new nut outwards away from it. The opposing faces of the female threads are brought to bear against the male threads of the screw, taking up the slop.

This arrangement, while probably a little convoluted, allowed me to adjust the backlash in the Y axis from about .100" to about .003 in the middle of the screw, the most worn section, and for all practical purposes <zero> out on the ends.

I hope my explanation isn't too muddled; I sometimes trip over my own words when talking shop, especially over the computer. There are a few details I omitted for brevity (ha!), and because I wanted to wait for a few of the wiser heads here to chime in. One of them probably has a better, simpler idea than mine. But I'll be happy to share all the pertinent info if you like. And I'm making progress on those solid models. I'll probably have drawings by this weekend.

Regards,

John