Machining A T-Slotted Cross Slide
Here’s another Metal Lathe Accessories project: the S-4382 T-Slotted Cross Slide. I’ve wanted to equip my 9A with one of these since I bought the lathe in ’05, but have only recently got around to it. The t-slotted cross slide, in addition to providing the normal functionality of the stock SB cross slide, extends the working surface completely to the rear end of the slide, providing t-slots and additional tapped holes for securing workpieces. When completed and installed, the S-4382 slide offers some important advantages over the stock South Bend cross slide:
1) The t-slotted cross slide, with its substantial horizontal working surface, makes possible certain boring mill-type operations on the lathe. Accordingly, it facilitates between-centers, or "line boring" operations.
2) It provides for the use of a rear-mounted toolpost.
3) It enhances the usability of a milling attachment, in that the attachment can be mounted at several locations along the cross slide, in addition to the usual compound rest position. If you already own a mill, even a quite large one, there is still no denying the handiness of the milling attachment for machining the ends of long workpieces, as the z-axis clearance of any lathe is essentially unlimited. (Metal Lathe Accessories also offers an auxiliary milling attachment base kit for mounting the attachment at locations other than the compound rest mounting hole.)
4) The S-4382’s dovetail ways extend the full length of the slide, and, provided you machine a new gib of corresponding length, provide an arguably more substantial, and longer-wearing guiding arrangement for the cross slide. Also, due to its larger dimensions (both length and width), this slide offers better protection from swarf contamination of the sliding surfaces. The stock “duckbill” extension of the SB slide is particularly onerous in this regard, as bits of swarf migrate underneath the duckbill. Inaccessible, they remain to become trapped between saddle and cross slide, unless the entire cross slide is removed to clear them out.
5) The semi-circular “wings” which surround the mounting hole for the compound slide are slightly larger on the S-4382, providing ample room for radial index marks at the four polar locations. Having index marks at these additional locations greatly simplifies setting up the compound at various odd angles.
6) The t-slotted surface provides a handy place to set your can of cutting fluid whilst machining operations are underway. (Well, it does.)
7) It’s a fun machining exercise, and the finished slide looks cool.
As with all of the Metal Lathe Accessories kits I have thus far machined, the S-4382 kit proved to be of excellent quality. The machining instructions and drawing are clear and concise, and the casting machines beautifully. Also, while the S-4382 cross slide is intended for the 9”/10k lathes, at least one other forum member has machined an S-4382 for a 10L.
Many of the MLA accessory kits, with a bit of ingenuity, can be machined completely on the lathe itself -- no mill required. Unfortunately, the S-4382 is not one of them. You don’t need a large mill -- the cross slide project fit handily within the work envelope of my SX3 bench mill -- but you need to at least have access to one. If you don’t, you may want to consider having one machined for you. Earl Bower, of Bower Machine, offers the service at a reasonable cost, though I do not endorse his packing methods (see this post).
As always, keep in mind that there are many methods to accomplish the same result, and this account is just one builder’s approach. I welcome any comments on the methods used here, and am more than glad to hear about how others have done it (or would do it.) Also, this report will be presented in multiple, discrete posts as time permits, but feel free to add your own comments in the meanwhile.
Here are some pics of the raw casting. The first is from the top side, after I cleaned off some of the high points with a file. Note that the t-slots are cored to rough undersize dimension, to facilitate their machining:
And here’s the bottom side, showing where the dovetails will be machined:
Machining Top & Bottom Surfaces
For machining the top and bottom surfaces of the casting to rough dimension, I clamped the casting to the mill table, after placing a thin piece of card stock material between table and casting, as a clamping pad. I used an indexable carbide end mill (APT #EM20-R8 “Tri-Dex”), which worked very well, as the “skin” on cast iron can wear conventional HSS end mills fairly rapidly. Here’s a view of the process:
The bottom surface is accomplished in a similar manner. Long before this point, I had devised a cardboard shroud for the mill table, to help contain some of the carbonaceous swarf spewing from the cutter. Here is a video showing the operation, and also giving an overall view of the cardboard shroud, and the general layout of the area:
The top and bottom surfaces should initially be machined to within 15-20 thousandths of finished dimension. It’s a good idea to then let the casting “rest” for a day or so, to allow any residual stresses in the casting to relieve themselves before finish milling to final size. My casting showed no warpage at all, resting flat and even on the surface plate.
(to be continued...)
Last edited by Paula; 11-19-2010 at 06:33 AM.
Reason: Updated video link
Paula just my thought on your cross slide. The cast wings that hold the compound bolts look good but the chuck side one should be trimmed a little as i found it gives a tad more clearance with the chuck. Keep up the good work...Bob
Bob Wright Metal Master Fab
Salem, Ohio Birthplace of the Silver and Deming Drill, all others are copies.
I machined one of those shortly after they were first available. Long enough ago that digital cameras weren't available, darn it.
The bottom line is that it is an excellent and very useful attachment for your SB. The time maching it is time very well spent, and very enjoyable to boot.
Interesting idea, Bob...
I like the cardboard shroud. Just like everything else you do, it looks professional and well made, even with cardboard and tape.
Wondering which carbide inserts you used and DOC per pass in the CI.
Any of your speed and feed experience with your setup would be good to know.
I'm new to milling and have just milled aluminum and steel up to now.
I like your mill and the mods you've made on it. Good work.
Thanks for the comments thus far.
Gary, the Tri-Dex uses TPG322 inserts -- C2 for cast iron, and C5 for steel. Since my mill is a small bench model, modest cuts are the order of the day. For the operation shown in the video, I believe the RPM was around 250, and depth of cut was on the order of .020"
Machining the Sides
To set up the casting for machining the sides, I simply clamped it in the vise. The sides are accurate enough in the as-cast condition to use one as a reference against the vise “floor”, after a light going over with a file. Here again, the Tri-Dex carbide end mill was used:
The casting is flipped over in the vise to do the opposite side. Note: the drawing specifies an overall width of the t-slotted area of 3.375 inches, but I just machined the sides until they cleaned up. This resulted in a finished width of 3.450 inches, which gives just a slightly larger working area, and should not cause any problems.
Machining the T-Slots
To complete this phase of the project, a 5/16” t-slot cutter is required. (I purchased one from Enco for $20.41.) But before using it, the center portion of the slots is cleared out with a conventional end mill:
The width of the slots should be kept as close as possible to .375”, and the centerline spacing of the slots should be 1.625”. Clearing out the center portion of the slots can be completed with multiple passes, but the t-slots themselves have to be done in a single pass. I clamped the slide directly to the table, for added rigidity. I started with the center slot:
And here’s the finished job:
The Compound Slide Hole
The first step is to remove as much material as possible by drilling. My largest drill bit is a 1” size:
The hole can then be finished to size with a boring head. Care should be exercised to get a close fit with the compound slide spigot. As the final size is approached, it’s a good idea to check the fit with the actual slide spigot.
I used a fly cutter to machine a small chamfer on the finished hole:
(to be continued...)
Last edited by Paula; 03-16-2009 at 08:48 PM.
Up to this point, the only thing I did differently was to use a big flycutter to take the final light finish cut on the top and bottom. I ground the cutter with a rather large rounded cutting surface, honed it to a nice crisp edge, and took a very light cut. It had to spin as slow as my mill would go and feed as slow as my power feed would go, probably slower than it was intended to go truth be told, but it did result in a very nice flat surface with no imperfections that could be seen or felt anyplace.
I measured the dovetail slot on the stock cross slide by sliding an adjustable parallel up to snug between a pair of 5/16" or 3/8" (?) (I don't remember which at the moment) drill blanks, tightening the set screws on the parallel, lifting it out and measuring the adjustable parallel with a micrometer. I used the same technique to measure progress when machining the T-slotted cross slide. It worked really well and resulted in a very nice fit.
I've used the same technique (and the "other" set of drill blanks) in more recent times when machining tool holders for my Aloris clone tool posts.
I made a jig to hold the removable gib piece for machining. It's since gotten lost.
"Long enough ago that digital cameras weren't available, darn it. "
Some of my early projects were documented by a helper standing by
and sketching the setup with a stone tablet and a chisel. Ah
the steady march of technology.
"Some of my early projects were documented by a helper standing by
and sketching the setup with a stone tablet and a chisel."
Jim did not say why I quit helping him. I drop a tablet on my foot and he just laughed! So I got mad and got on my dinosaur and rode off into the sun set. Gary P. Hansen
Compound Spigot Clamp Holes
These are the two holes for the plugs and setscrews which lock the compound slide. They impinge on the “dovetailed” compound spigot from the rear at an angle of around 50°, pulling the slide tightly against the cross slide top surface, and locking it against rotation.
For this operation, I clamped the cross slide to an angle plate on the mill table. I made up a little bushing to simplify the setup process:
It had a twofold purpose:
1) To function as a “washer” for bolting the slide thru the 1.375” spigot hole, and
2) To provide a simple means for lining up the mill’s spindle with the center of the spigot hole, by means of a .500” dia. extended neck.
Thus, once the slide was fixed to the angle plate, I used a center finder to locate the center of the .500” dia. neck of the bushing, and locked the x-axis. This allowed me to rotate the slide around slightly to get the entry point of the hole centered on the flat. To me, the exact angle of the hole with respect to the slide was not as important as the setscrew hole being visually centered on the flat.
With the slide locked in place (bolting thru the spigot hole, plus a step clamp in the bottom corner), a light facing cut can be taken to true up the surface of the flat. The hole can then be drilled, reamed, and tapped, per the drawing:
You might want to check the actual diameter of your plugs -- I wound up reaming the through-hole with a .001” oversize reamer. A precise fit isn’t absolutely necessary, but you certainly don’t want the plugs binding in the holes, as it will make removal of the compound difficult.
With one side completed, I loosened up the clamps, and rotated the slide around for the other side. No need to change the x-axis setting:
Boring the Hole for the Cross Slide Nut Spigot
This is the hole for the spigot which holds the cross slide nut. This operation could have, and probably should have, been completed when the slide was still clamped in the vise to bore the compound spigot hole, but for some reason I waited until after I had the compound spigot clamp holes completed. Just a bit more setup time the way I did it.
The nominal diameter for the hole is 11/16”, but you want to use care to get it sized properly. Ideally, the spigot should be a “push fit” in its hole. That is, a very slight interference fit, though the spigot can still be inserted by hand pressure alone.
As with the compound spigot hole, I used drills to get the hole roughly to size, then finished with a boring head:
As the final size was approached, I offered up the actual nut to the hole for checking the fit. Don’t get in a hurry here.
(to be continued...)
Last edited by Paula; 03-23-2009 at 11:04 AM.
Reason: Added a "the"
Nice work Paula!
What are your plans when it comes to the dove-tail? A 60* cutter will get you close, but a scraped fit will probably be required for full engagement. Otherwise, you may have a "line" contact between the slide and the machine. Also keep in mind that the left dove-tail flat of the machine will probably have more wear than the right because of chip intrusion (at least that's what I noticed on my heavy ten). This could put the working surface of the slide off-parallel to the machine spindle axis. I'd bet the machine this is going on is in good condition, so you probably don't have to worry.
How did you determine where to bore the hole for the cross slide nut? It seems like it's location would reference the dove-tail you have not cut yet?
Nice work Paula,
I would suggest you try something different and machine a dovetail for a tapered gib setup.
Machining the Dovetails
I began this phase of the project by taking some careful measurements of the existing slide, most particularly the distance from the 11/16” dia. nut hole to the non-gib dovetail. One good way to measure the functional surfaces of the dovetails is to place dowel pins against the dovetail surfaces, and take measurements from the pin’s surface. I made the drawing below from the measurements taken of my original cross slide:
The 11/16 dia. pin was turned from a short piece of 3/4 CRS, and makes a handy gage for checking the dovetail fit. Like the nut spigot, it should be an accurate (“push”) fit in the cross slide nut hole. Though the instructions suggest 3/8 dia. pins for measuring, I had to use 3/16 pins because of the quite narrow flat machined area adjacent to the angle surface. It doesn’t really matter, because the measurements are relative, rather than absolute. In other words, it is only important that they be the same for both the original and new slides.
It should also be noted that, while the above measurements reference the horizontal flat areas where the pins rest, this is not a functional surface. It can only be used as an accurate reference surface if the dimension from the bottom of the slide to that surface is exactly the same on both slides. On my slide the dimension was exactly .375”, so I was very careful to machine the new dovetails to the exact same depth.
The most critical dimension is the .378” dimension in the drawing above (from the nut hole to the non-gib dovetail), since it determines how well the cross slide nut will align with the screw when the new slide is installed. So measure carefully. The gib side is much less critical due to the designed-in clearance between the gib and dovetails. (While I used a caliper for taking measurements against the pins, you might want to consider Fitch’s idea of using an adjustable parallel.)
With the critical dimensions established, the casting can be bolted down to the mill table. Since you probably want to be able to use the sides of the cross slide as a reference for lining up work to be clamped on the slide, it’s important that they be aligned with the x-axis of the mill. I used a dial indicator:
The bulk of the material should be removed with a plain end mill. To save wear on the expensive dovetail cutter, it should only be used for cutting the 60° angled surfaces. I used a .500” dia. solid carbide end mill, working toward the 1.732” dimension obtained from the original slide, and keeping the final depth just a few thousandths under the target dimension (.375” in my case):
The 11/16” gage pin can be periodically inserted in the nut hole for taking progress measurements. DON’T FORGET TO REMOVE THE GAGE PIN BEFORE TAKING THE NEXT MACHINING PASS (I had a couple of close calls here -- attention needs to be paid.)
With that done, proceed to the dovetail cutter. I used a 1.375 dia. cutter. I set the depth of cut to .374” initially, dropping it to .375” for the final pass. As the target dimension is approached, take very light cuts and check frequently, especially on the non-gib side. Here’s a view of the dovetail milling operation underway:
With the dovetails machined (and dimensions double-checked), the slide can be unclamped from the mill. I used a whetstone to carefully remove sharp edges from the dovetail edges, leaving a slight radius.
My lathe had almost no wear on it when purchased several years ago, so I wasn't too concerned. You are right that if the cross slide in question is significantly worn, the saddle surfaces should be reworked. But this should be considered anyway, even if one is not replacing the cross slide. This kind of work is outside my experience, so I'm glad that I didn't have to contend with it.
Originally Posted by Belding
I wanted the cross slide nut referenced to the center of the cross slide, as I had already determined that the cross feed screw was perfectly centered on the saddle ways. The cross slide dovetails were then referenced to the cross slide nut hole. Different strokes, I suppose. Either way, one needs to consider beforehand where the outer dimensions of the slide will wind up.
How did you determine where to bore the hole for the cross slide nut? It seems like it's location would reference the dove-tail you have not cut yet?
(to be continued...)
For a low-mileage machine, doing it the way you did works
just great - that is, by measuring the *existing* slide
dimentions and then simply replicating them in the new one.
But "simply" I mean, with a lot of cross checking and
head-scratching. Dovetails like that can be tricky things,
I found this out when fabricating some hardinge QC toolpost
However for a high mileage machine, fitting a new top
slide is an opportunity to partly correct for the wear
that develops as the sliding surfaces "go away" over time.
In most cases the left slide surfaces are without gib,
and the gib is tightened to compensate for wear.
So the on an older machine, the nut bore moves to the
right over time, in relation to the bore of the feed
screw bushing. On really high mile machines this effect
can be seen with the naked eye, much less a dial gage.
Also the nut bore tends to get 'low' in relation to the
screw axis, to a lesser degree.
Because high mileage machines tend to get slopply crossfeed
screws over time (in a variaty of aspects) and most work
is done with the slide near the center of the travel,
there's not that much binding.
Some manufacturers like hardinge will sell replacement
crossfeed screws and nuts, with the nuts untapped.
They supply a rental tap and fixture, so the nut may be
drilled, and tapped, when the nut attached to the slide
and installed on the machine. That way the aligment
is achieved within a thousanth or so.
I'm makeing these comments because many of the SB machines
out there *are* high mileage and fitting a new slide
like this, along with getting a new nut and crossfeed
screw, is one of the quickest way to improve the
quality of the machine.
Even if one does not take the trouble to scrape the
hourglass wear out of the male dovetail, every bit helps
on this stuff.
I used a piece of 1/8 x 1/2” flat ground stock for making the gib. As I was casting about to come up with a suitable way of fixturing the gib for machining the edges, as well as drilling the locator holes for the gib screws, I received an email from SB forum member ‘gunsmither’. He had noticed an earlier post where I mentioned that I was machining a t-slot cross slide, and offered to send me a set of gib spreader clamps that he made for machining his own gib. These are basically used to fix the gib securely in the dovetail slot for accurately machining its top and bottom edges to the required angle:
When milling the first edge of the gib, the lower edge can rest against the bottom of the dovetail slot, but when milling the second edge, the gib needs to be raised up slightly to clear the cross slide and clamps. I used (at Gunsmither’s suggestion) some 3/32” dia. drill rod as a spacer:
The spreader clamps also came in very handy for drilling the gib screw holes. The original gib screws had a 12-28 thread. This size is difficult to find these days, so the drawing calls for a 10-32 thread. Unfortunately, the kit does not include gib screws, so I needed to purchase some 10-32 x 3/4” setscrews. I was unable to find this length in small quantities, so I wound up purchasing oval-point set screws, which are available from McMaster-Carr in quantities of (25) pieces, thus avoiding the need to purchase a hundred frigging set screws when I only needed nine.
In hindsight, this was perhaps a happy deviation from my original plan, as the oval-point screws probably do a better job. I turned the points down to .140” (well below the pilot drill size for a 10-32 thread) so they would fit nicely in the holes drilled into the gib:
After carefully determining the depth required for drilling into the gib with the 10-32 pilot drill, I set the depth stop on the mill (you definitely want to avoid drilling through the gib!) Here’s a look at the gib screw drilling operation.
Once the pilot holes are drilled to the correct depth, the spreader clamps can be removed, and the holes chamfered and tapped through. As for the gib itself, it’s a good idea to generously round all the sharp edges, to avoid any interference in the tight corners.
With the gib completed, I figured it was time for a preliminary test fit of the new cross slide. I first assembled the slide and gib to the saddle without the nut, so that I could evaluate the fit of the dovetails and adjust the gib screws with a better “feel”. The cross slide moved very smoothly, with no tendency whatsoever to bind up anywhere along its travel, even with the gib adjusted for a snug, no-shake fit.
Then I installed the nut to find out how well it aligned with the screw. Happily, the care exercised in aligning the nut hole to the dovetail ways paid off, and the screw and nut functioned perfectly.
A couple of footnotes to this phase of the project:
Gunsmither gave me his gib spreader clamps with only one proviso: that I offer them to anyone else who needs them for machining a t-slot cross slide. Fair enough... so anyone who can use them for their own project, just let me know, and they are yours.
Also, since I had to purchase twenty-five of the oval point set screws, I have enough left over for another set. Contact me if interested.
(to be continued...)
At this point, the slide is basically complete. All that remains is to drill and tap some 5/16-18 holes on the top surface, the 1/4-20 threading stop hole in the front, grinding the top surface, and painting.
I recommend the purchase of a 5/16-18 bottoming tap for the holes in the top surface. These should not be thru holes, and there is not a lot of depth to work with, so a bottoming tap makes sense for getting the maximum usable thread engagement. I think I only paid just over $5.00 for my bottoming tap, and it will no doubt come in handy for other projects.
Though not absolutely necessary, I elected to have the top of my slide surface ground. Fortunately for me, our machine shop at work is equipped with a very nice surface grinder, and the guys in the shop always seem willing to do favors for me. I would have gotten a picture of the grinding process, but since this was a “government” job, I wanted to keep things as low key as possible. And frankly, they had it completed before I could even think about getting my camera out. Anyway, it turned out beautifully. (By the way, they refer to this process as “dusting off” the top surface.)
I debated about painting the sides of the cross slide area where the t-slots are, but finally decided not to. So, the only painting required was for the small, unmachined area around the front half of the slide. I did only a minor amount of cleaning up and smoothing the cast surface before applying three coats of Tractor Supply Company enamel (leftover from the original lathe paint job). Here are front and back views after grinding and painting:
Compound Index Marks
One additional little feature yet to be completed is engraving the index marks for the degree graduations on the compound base. My original slide had an index mark only at the twelve o’clock position, but I have come to realize over the years that it would be very handy to have index marks at additional locations. Therefore, I decided to engrave marks at the three, six, and nine o’clock positions as well.
My first step was to align the compound slide with the longitudinal axis of the lathe. To do this, I chucked a half-inch ground rod in a collet, and set up an indicator on the compound to traverse the tangent surface of the rod:
Eliminate the effect of any slight bowing of the rod by rotating it around to find the extremes, and set these at 90 degrees to where the indicator traverses. With the compound lock screws just snugged, feed the compound back and forth thru the limit of it’s travel, noting the indicator reading. Tap on the compound to make slight adjustments to its radial position, until the indicator shows no movement when traversing the rod. This will get the compound lined up parallel with the spindle axis with about as much accuracy as you will ever need, and perhaps way more. Tighten the compound locking screws. I used a scribe to carefully scratch small witness marks on the cross slide surface at the four 90-degree positions.
There are a number of suitable ways to produce satisfactory index marks (including the scribing method just mentioned), depending on how ambitious you are. The one I chose to use in this case was to engrave the marks with a carbide engraving bit. This gives a neat appearance, and very good visibility. The engraving bit I used is a Micro 100 #RTC-125-2, which I purchased from Travers Tool Co. It’s a double-ended cutter, just a tiny little thing, only 1/8” diameter:
Now, my mill has a top speed of only 1800 RPM, and these engraving bits are designed to run a lot faster. I’ve been meaning to make one of those auxiliary high-speed spindles for my mill, but for this job, 1800 RPM would have to do. I clamped the slide to the mill table, aligning it longitudinally just as I did prior to cutting the dovetails, with the compound hole precisely centered under the spindle.
With the center of the hole designated as zero, I arrived at dimensions of 1.660” for the start of the mark, and 1.820” for the end of the mark (.160” length). Note that the original slide had an engraved (or stamped) “0” denoting the position of the index mark, but I elected to dispense with it for my slide (“Zeroes? We don’t need no steenking zeroes”) though if I were engraving with a CNC, I would probably engrave the zeroes as well. Here’s the engraving operation in progress:
It turned out that the “theoretical” locations of the index marks, as determined by the position of the slide on the mill’s table, were very close to the witness marks that I scribed with the slide on the lathe -- so close, that I only had to “tweak” the position of the spindle a few thousandths here and there to get the engraving bit to coincide with the witness marks -- a testament to the accuracy of the degree graduations on the compound slide base.
I began the process by carefully zeroing the z-axis with the tip of the cutter just touching the surface of the slide, with the cutter in position over the first mark. With the spindle running at maximum RPM, the cutter was fed down into the surface .001”, the table traversed .160” length of the mark. The cutter was then brought down another half a thousandth, traversed the length of the mark, et cetera, until a total depth of around .007” was achieved. This seemed to give about the right line width to match up with the graduation lines on the compound base. Once I got into the process, it went very quickly, and not nearly so tedious as this report seems to suggest. Here’s the finished engraving job:
(to be continued...)
Great stuff. Had to laugh about the "keeping the G-job low key" comment.
One of my first G-jobs at work was having a pair of BMW motorbike jugs honed out
on their Sunnen hone. One of the shop managers did aircraft stuff so he kept that
sunnen there for special jobs.
He said he would be glad to do it, but it would have to happen on the quiet. "Don't
come down and watch, I want it to be low key." Of course I could not resist just
walking by the back door to the shop ever day after that, at lunchtime. Couple
of days later I was rewarded with the sight of Earl running the Sunnen hone, with
about five of his employees clustered around him, giving him instructions on how
he should be doing the job! They all couldn't resist helping out on it.
Low key. Right.
Optional Feature: Way Wipers
As long as I was making a new slide for my 9A, I figured this would be an excellent opportunity to add some optional features. The first of these is a set of way wipers at each end of the slide. They are not difficult to make, though a bit of a “fussy” job, due to their small size.
I started by machining a 3/16 x 3/8” notch at the front and rear of the slide. (You may have already noticed these notches in the pictures posted earlier.) The 3/16” dimension is to accommodate a 1/8” felt wiper, and a 1/16” thick brass keeper. A 6-32 button head cap screw is used to secure the keepers:
You want to size the felt to be a snug fit in the notch, so that only modest pressure from the screw is required to keep the edges of the wiper in close contact with the slide ways. Here is a view of the front-end wipers (the ones on the back are identical):
Optional Feature: Nut Lube “Well”
Another optional feature I decided to add, while I was at it, is a “well” for storing lubricant for the cross feed nut, accessed thru a “trap door” on top of the slide. The reasoning behind this is that, unless you have an indicator or digital readout on your cross slide, the accuracy of the cross slide is dependent on these items not being excessively worn. Therefore, lubrication of the nut is important. I have always accomplished this by cranking the slide to the extreme outward position and squirting some oil on the screw, but it is a tedious procedure, and needs to be done at rather frequent intervals. My thought was, why not use the volume within the cross slide nut’s spigot to contain a reservoir of lubricant, which could be dispensed to the wear point in a more gradual fashion?
This is exactly what I managed to do. The first step was to remove the two-part, right-angle set screw arrangement, and drill the inner hole a bit deeper -- just deep enough that the point of the drill broke into the outer periphery of the threaded hole. By placing a 3/16” slug of wiper felt in the bottom of this hole, oil could be gradually fed directly to the threads from the reservoir above:
The spigot would now be retained in its hole by a set screw acting through a brass push rod from the side (enabled by the geometry of the t-slot cross slide). Additionally, the lube well is protected from swarf by a “trap door”, or plug, consisting of a thin disk of cast iron closely fitted to a recess above the spigot. As a side benefit, this plug eliminates the uneven surface inherent in the original design -- a factor to be considered, now that the cross slide’s top surface can be used to mount work for machining.
To get the oil well plug exactly flush with the surface of the slide, I decided that it would be neat to have it ground at the same time that the slide was surface ground. Thus, the plug was originally made with a small, temporary shank, tapped with a 6-32 hole. Here is a shot of the plug being sawed from a bar of cast iron, after initial machining operations:
The shank was used to hold the plug in place during surface grinding, and subsequently machined off to provide additional capacity in the “well”. Since the plug is a close fit in the hole, and there is nothing to grab hold of to remove it, a small magnet works fine for the task:
And with the plug back in place, the hole is all-but-invisible, providing a smooth, even working surface, and impervious to the entrance of chips and contaminants:
I have to say that this has been a thoroughly enjoyable project. I’m looking forward to the enhanced usability afforded by the t-slot cross slide, and encourage others to consider machining one for their lathe, if they are so inclined. The casting provided with the kit is an absolute joy to machine, and gives a quite good surface finish with conventional tools. I will be glad to answer any questions from prospective builders, regarding the machining methods used for this project.
Last edited by Paula; 03-23-2009 at 08:08 AM.
Reason: Left out a sentence