Machining A Replacement Cross Slide For A Logan 11" (as Promised)

[Rex Walters]

You can always shim down. But you can't shim up (you can't buy negative thickness shim stock).

Joke #1: "If you cut a rope to0 short, you can always splice some more on, but if you cut it too long there's nothing you can do about it."

(Of course there is a "negative shim stock" equivalent. It's called an "end mill." ;-)

... be sure that there is adequate clearance for the nut to run off of the screw threads before it runs into the top of the dovetail area. The gap between the dovetails sure seems to start a long way back. And also be sure that the nut runs off of the end of the feed screw before the cross slide runs off of the dovetails or into something.

Joke #2:

"Ask me what the secret is to telling a great joke."

"What's the secre—"

"Timing!"

I'll post some photos shortly that explain what I mean here. I'm pretty sure I've got a way out, but I'll post some photos shortly that explain what I mean.

 

[Silverbullet]

I also have a 11 inch Logan lathe. I love that little old girl I think mine would like the same thing . Adding room for tooling on the back is nice to have. I always wanted to add a taper attachment to her too. So maybe I'll do both if I can ever get the time . Too many projects .

 

[Rex Walters]

Today's lesson is: don't try to do too much in one session! (You'd think I'd have learned this lesson by now.)

I was delayed getting into the shop today due to so some money chores taking far longer than seemed reasonable.

So I was both feeling rushed and in a foul mood at the same time when I started work on the slide today. The results were predictable. I only wish I'd read Robert's last note before getting started (though now that I think about it, I doubt it would have made a difference).

Before I quit yesterday, I bored and tapped 10-32 holes on the gib side for the gib screws and lock-screws. Andy's drawing called for nine evenly spaced holes, but since he didn't include either lock screws nor a pin, and since my slide is precisely 11" long, I thought I'd make my life easy on the DRO and tap ten holes spaced exactly 1" apart (at inches 1 through 10 from the right hand side:



Then I used my adjustable parallels yet again to hold the gib in place as I drilled a hole for the pin, and marked the locations for the detents with a transfer punch. I'm using 1/8" dowel pin to pin the gib, so I first drilled a 7/64" hole all the way through the side of the slide and through the gib. The pin hole was exactly 7.500" from the left end as seen in the photograph below. I then used a transfer punch to mark the locations of the previously tapped 10-32 holes into the gib.



Next I removed the gib and enlarged the marked locations with a prick punch. I later enlarged these detents on the drill press with a random large drill. Probably overkill to have both a pin and depressions for the gib screws, but overkill is my middle name. After drilling the depressions, I lapped the gib with sandpaper on my surface plate to remove any surrounding areas of metal that were pushed up by the process.




Next I broke out my "under/over" reamer set, and reamed the hole in the slide one thou undersized (0.124"). The hole in the gib needed to be oversized for a slip fit, but I couldn't use the slide itself again to hold the gib in place (using my trusty adjustable parallels) because I needed a press fit in the slide itself.

(Here, right here, is where I should have called it a day, cleaned the shop, had a beer and a good meal with the family, then had a good night's sleep. Sigh.)

Here's the first questionable decision of the day (fortunately it ended without incident): Unsurprisingly I didn't feel up to milling a fixture just to ream one hole larger in the gib, so I decided to free-hand it. I chucked a 0.126" reamer in the mill, broke out a pair of heavy leather gloves, and manually held the gib roughly in proper 60 degree orientation (figuring a reamer is reasonably self guiding as long as I hold it close, and I only need +/- 0.005" or so anyway). I'm not sure which would be more likely to grab, a twist drill or a reamer, but using a reamer with a moderate speed on the mill and the leather gloves I managed to enlarge the hole without so much as a scratch, much less a trip to the E.R. Whew!

By now I was in full-on, damn-the-torpedoes-full-speed-ahead mode, so I decided it was time to press in the gib pin. I don't actually own a press, but hammers, punches, and vises I have in spades, so here we go!

My dowel pins were considerably shorter than the depth of the hole, but I figured after driving in the pin as far as it would go with a vise, I could use a pin-punch to drive it the rest of the way. Wrong! Hardened against hardened is always a bad idea. I had exactly zero success driving the pin any further with a punch, but I did manage to make a beautiful couple of dings on the side of the slide.

A short walk later (there may have been some cursing involved) I realized that I should have just pressed the pin in from the other side (of course!).

At this point I had a (short) pin pressed in such that it was just proud of the side of the slide (with a couple of gorgeous "newbie tattoos" surrounding it) and nothing extending into the dovetail. After a head scratch, I realized that pressing in another pin from the other side would push the first one out sufficiently to grab onto it and remove it, so I put my steel jaws back on my vise (I normally keep my homemade copper jaws on the vise), grabbed a nut, and had a go:



Worked just fine for the first sixteenth of an inch or so. After removing it from the vise to inspect progress, and then re-setting to push it the rest of the way in I had some trouble. The first sixteenth moved without severe pressure, but now it wasn't moving. I took it off again to inspect and the inner pin seemed to be going in straight. Nothing seemed amiss so, or course, I just assumed it needed more pressure (of course!).

Remember that little extra depth I had in the dovetail slot? (Last photo in comment #8.) In re-inserting the part into the vise, I managed to put it in deep enough that the vise jaw was catching on that step. So by cranking harder all I was managing to do was bugger up the outside (and bottom) of the slide with a nut-shaped outline — this came back to haunt me later.

Eventually I realized what was going on, and lifted the part a littler higher in the jaws. Then it was smooth sailing: I got the inner pin pressed in as far as I could get it with the vise jaws, and the outer pin was pushed out enough that I could grab it with the vise and remove it by taking a dead blow hammer to the part itself.

I could only push in the inner vise pin so far from this direction, and it had mushroomed slightly from the pressing, so I broke out a dremel tool and diamond bit to have at it. After about ten minutes of "fettling" the gib seemed to fit quite well, with no discernible slop. Joy!

I took the slide with the gib in place over to the lathe and tried it on the saddle. It slide on nicely until it got to the pin, then it bound slightly. Not enough to prevent it from sliding, but clearly it was binding and something was amiss. I thought maybe the pin was just slightly misshapen and keeping the gib from settling into the dovetail properly, so I broke out the dremel again as well as my optivisor with the extra loupe in front to really see what I was doing (no pictures of this — I look too ridiculous).

Back to the lathe. No joy. Still binding.

Eventually I copped to the fact that the "nut impression" on the side of the slide had actually created a couple of burrs or raised areas on the bottom of the slide (the bearing surface). After giving the slide a quick once-over by lapping again with sandpaper, I was extremely relieved to find it now slid freely with no binding. The burrs were raising the slide just enough to cause it to bind in the dovetails — it wasn't a side-to-side fitting problem, it was an up-and-down problem.

At this point I had to break out an indicator and see how I was doing. I was absolutely astonished to discover that by pushing and pulling on opposite corners with the slide fully retracted (completely covering the saddle) I only saw about 0.0025" total indicator movement. All the tramming effort appears to have paid off, smooth sliding with only a couple thou of play (before I insert any gib screws) is far better than I'd hoped for.

Woo hoo! Success. Time to clean the shop and call it a day.

Nope. "I just need one more hole in the slide to attach the cross-feed nut — that can't take too long!"

To cut to the punchline, I now have the nut in place, and the slide is working fantastically well with the cross-feed screw engaged and feeding smoothly, and with no discernible lateral play once I adjusted the gib screws.

Getting to that point will be another comment in this thread though. You know you've gone a step too far when you're not even willing to document the process in the same comment!

Onward!
--
Rex

 

[Rex Walters]

Oh: Forgot to mention that I plan to use positions 2 and 9 of the ten holes for gib lock levers (that I need to make on the lathe). The remaining eight holes are for gib screws.

Also, it's important to put the gib pin someplace other than the exact center. It helps with "bi-lateral ambiguity" — between the dimples and the pin it's brain-dead simple to figure out the orientation for the gib whenever you're reassembling the slide.

 

[Rex Walters]

I think mine would like the same thing.

While I can't claim victory quite yet, I'm increasingly convinced this is going to be a fantastically useful upgrade to my lathe. All I can say is "go for it!"

Andy's castings are very, very nice. Assuming my build is ultimately successful, I'll post measured drawings at the end of this thread. As should be obvious, I'm not working to precise drawings currently. Instead, this is effectively a prototype using measurements from the (far different) original part as well as (occasionally) dimensions from Andy's drawings. I don't want to post any drawings yet as I'm still making changes (AKA "mistakes").

I love my lathe too — it's absolutely my prize possession. I'm a user, not a collector though, so I have no qualms about replacing parts and modifying the original machine.

Andy also sells a casting to use as a taper attachment. It should be as simple as tapping a couple of holes in the back of the cross-slide to attach the taper attachment. I've tried to keep the design consistent enough that you can still use Andy's other castings without changes.

Regards,
--
Rex

 

[4GSR]

Nice write up! Thanks for sharing.

Now all you have to do is scrape and fit the slide to the saddle.....

 

[Rex Walters]

Now all you have to do is scrape and fit the slide to the saddle.....

Actually, there was a whole lot more to do before scraping and fitting. Several adventures along the way that I'll start writing up shortly, but after a furious few days of working on it for 4 to 8 hours a day, I've successfully finished the cross-slide and gib! The compound slide fits beautifully and the cross-slide functions as well as I could have hoped. Now I'm ready for scraping and fitting:



Woo hoo!
--
Rex

 

[Rex Walters]

Okay, now that I've given away the punchline, here's the rest of the story (apologies to Paul Harvey).

Before reading the following, please remember that this is the continuation of the day I worked too long and made all sorts of mistakes. Still, the great thing about metal is that there is almost always a way out after mistakes (even if you have to braze on some more material).

I knew that all I needed to do was attach the acme nut and the slide would be basically functional as a boring table (i.e. without the compound slide). I just had to give it a shot.

The first thing to figure out was how far forward I wanted to put the hole to attach the cross-feed nut. I wanted to get as much travel as conceivably possible (hopefully reclaiming a little travel I lost with my home-made cross feed dials). I slid the nut onto the cross-feed acme screw and measured the distance from the dials:



I measured multiple times and thought through it carefully before boring the hole, but 4.250" from the dial end of the casting seemed to be the optimal distance (with about 1/16" to spare).

I knew the new part was considerably thicker (about 0.100") than the original, though, so I had to get the hole in the nut positioned correctly vertically. So I measured the distance on the original part:



The distance on the new part was quite a bit thicker, but as I wise-cracked earlier I just needed to mill a pocket in the underside to the correct depth:



WRONG! Wrong! Wrong!

Of course, as anyone taking their time would have realized, the dimension that matters is from the bearing surface to the mounting surface of the cross-feed nut:



So now I got to use both a negative and a positive shim. ;-)



Finally, with the shim in place and the nut attached, the cross slide was actually feeding as I turned the crank. Success! Let's call it a day!

Whoops. Oh darn! (I may have used other words in the shop). When I screwed the slide all the way closest to me, it started binding about a quarter inch before hitting the dial:



(Note the gap between the edge of the fixed part of the dial and the casting.)

Had I mis-calculated? Measured wrong? Do I need to move the hole?!! Argh!!

A few deep breaths and a walkabout later, I finally realized that the acme nut itself was hitting the curved part of the slot in the saddle. That was easy to fix with that most precision of tools, the bastard file:



Now with the nut attached I could retract the slide all the way to the dial. Whew!



As I think I already mentioned, even without the gib screws in place to tighten things up, I only had 0.002" to 0.003" of play even with my full weight pushing and pulling on opposite corners. With the gib screws in and adjusted, turning the crank was as smooth and silky as I could have hoped for. Now I could (and did) finally call it a day.

One further note: it was quite obvious that even with the gib screws adjusted, it was quite a bit tighter at the far side of travel than with the front of the slide closer too me. Close observation showed that the flat horizontal area of the fixed ways (on the saddle — not the dovetail sides, but the horizontal bearing surfaces) closest to me were visibly worn more than the areas further away.

This makes sense on such an old lathe since most of the time you are turning with the compound toward the front of the lathe. Since the farther side was less worn, it was effectively lifting the slide and tightening it on the dovetails. I'd felt the same thing since I owned the lathe, even with the original slide, and I thought for sure that I just hadn't done a very good job adjusting the gib screws. Now I know exactly why scraping and flattening the ways is such a big deal!

I tried to photograph the wear, but it was too hard to see with available light and the camera on my phone. Believe me, there was no way at this point in the day I was going to break out the SLR and a couple light stands!

Anyway, as long as the day had been, and as many screw-ups as I managed, I still ended with a functional boring table at the end of the day. Yay!

Note that I've re-used the beat up old screw to attach the cross-feed nut from the original part. Someday I may replace it with a new screw, but I'm more interested in utility than beauty most of the time, so we'll see if that day ever comes.

I've also marked the rough location where the compound will go. Unfortunately, the slot for the compound looks like it will interfere with some of the 5/16-18 tapped holes that Andy calls for in his drawing for other parts he sells (like ball turning attachments, etc.). I'll figure out alternate ways to attach things as I add accessories.

[By the way: Dykem Brite-mark paint sticks are awesome. The marks last much better even around oil and many solvents. My sweaty hands can erase the marks from a sharpie pen, but those paint-stick marks don't come off unless I make an effort to remove them.]

Onward!

 

[Rex Walters]

Okay, today was the final day of machining. The first thing I decided to do was cut off the ears! Since I wanted to mount my compound further back on the casting, the ears looked funny. I figured that straight and square is probably more useful most of the time for workholding or whatever anyway.



Next I needed to bore the 3/8" hole that holds the half-inch pin (hardened and press-fit) that the compound swings on. I used my 0.374" reamer to make it one thou undersized for a press fit.

Then it was time (deep breath) to start milling the circular tee-slot. The first step was to use a 5/16" end-mill to mill a circular slot (the slot is 3/8" — the smaller cutter allowed me to clean up the chatter on the sides). Plunge cuts are a lot easier on the machine, so I adjusted the stop and just plunged all the way around before following up with a clean-up pass to get rid of the ridges:



Then I took the part off the rotary-table, flipped it upside down, and bored a 3/4" access hole to insert the square-headed bolts that hold the compound. I also need the hole to get the tee-slot cutter up into position. (Unfortunately, I forgot to take a picture of boring this hole, but it was a pretty simple operation.)

The tee-slot cutter has a neck that is narrow enough to fit in the 3/8" slot I milled, but the 1/2" shank wouldn't fit so I had to use my grinding wheel to grind flats on either side of the cutter until it would fit:



I was a little worried that with so much of the shank removed, the R8 collet in my mill wouldn't be able to hold onto it very well, but that ended up not being a problem at all.

I was finally ready to start milling the tee-slot. The most puzzling part of the entire process (that had me mystified until I posted the question to the smart folks on this site). Okay, gibs locked in X, Y, and Z. Deep breath, look for anything stupid before I start removing metal — I've too much invested by this point to want to start over with a new casting.

This is only about the third time I've used my rotary table for anything. I'm not exactly the world's most experienced machinist — I bought my lathe a couple years ago and have only owned a mill for a couple months. I've tried to swallow my pride and publish all my mistakes as well as my successes so that others can avoid some of my more foolish errors.

Here's my initial setup when I started milling the slot:



Now, notice that long bolt protruding from the table clamp on the right? See how far it is from the cutter? I've got tons of room, I thought. I'm milling a circle so there's no way it will interfere with movement, right? Wrong. The center of rotation is precisely 1.260" to the right of the cutter, so as I started rotating that thing clockwise I eventually ran into a problem. Unfortunately because I was removing a ton of metal in one swell foop with the tee-slot cutter (unavoidable) I had quite a bit of tool pressure and didn't notice the problem until well after that bolt hit the spindle and shifted the work significantly.

In my defense, with the captured cutter, there was no easy way to do a complete 360 with the quill fully lowered so I was completely dependent on my faulty thinking — there was no easy way to do a n0n-cutting pass with everything in position. Sigh.

Anyway, I had to reset and re-center everything with better work-holding (after hack-sawing the bolts shorter):



That worked a treat (but notice the marred quill).

I had successfully milled a circular tee-slot with a captured cutter! That was pretty cool.

I've been wanting to make an aluminum sub-table for the rotary table to make this sort of workholding easier, but, of course, I wasn't willing to put this job on hold for that one.

Another shot of this the tee-slot milling:



Next I had to put the old cross-slide back on my lathe to make the center pin for the compound. This was a pretty simple bit of turning (that I forgot to photograph). It was just some 0.500" drill rod, with a 3/8" stub for a short length for a press-fit into the cross-slide.

Only a complete idiot would overshoot to 0.373" instead of 0.376" as planned. Loctite to the rescue (laugh)!

I also hardened the pin with a torch. Just heated to cherry red and dropped it in a can of water. Chucked it back up in the lathe and cleaned off the blueing with scotch-brite. Pretty! (And hard.)



Here's the underside (with the gib in place):



And with the gib removed:



Here's a terribly blurry photo of the gib pin:



And finally, here's the assembled cross-slide with compound on the lathe itself:



I left the milling marks from the 3/4" end-mill on top because I think it looks kinda cool. Originally I'd planned to fly-cut and maybe lap or scrape the top surface (maybe I will someday, but I'll have to remove the compound pin with heat first).

Obviously, the first job for my new cross slide is to turn down the gib screws a bit so they don't stick out (as well as making lock screws) but overall, I couldn't be happier.

I do plan to scrape and fit the dovetails and ways, but since I've never tried my hand at scraping before I want to get some practice with a simpler project first (the transfer block casting I bought seems like the perfect thing). I also plan to create measured drawings of my final design (or at least the design I'd use if I did it over again) in case anyone else has a similar-sized Logan and wants to attempt the same.

This was far and away the most complex part I've made in my short time machining. Couldn't have done it without sites like this and some truly superb YouTube publishers (Mr. Pete, Tom Lipton, Tom's Techniques, the Keiths — Fenner and Rucker, the Tool and Die guy, Dan Gelbart, and many others).

Very happy with the result!
--
Rex

 

[wa5cab]

Rex,

That's great looking work. And better than I could do I'm sure. But I have to ask one question as devil's advocate. In the first photograph in your previous post (showing a top view of the saddle with the cross-feed nut all the way toward the dial), are there still cross feed screw threads in the nut or did it just run off the threads?