Picture wise, I think I left off showing the saddle partially constructed. Hopefully I'm not duplicating links.

Anyway, installed more bearings on the Z-axis saddle:
http://frederic.midimonkey.com/cnc2/IM001828.JPG

Saddle structure completed:
http://frederic.midimonkey.com/cnc2/IM001829.JPG

Bet that makes a lot more sense now

Installed the leadscrew bearings in the top and bottom plates, and I undersized the holes and bored them larger using the lathe and a HSS cutting tool I ground a little bit. Glad I have a few of these, I'm making some really strange looking cutting tools out of them! Anyway, thank you for that suggestion, made things really easy. Aligning the 4-jaw was a pain, and I really wasn't able to get it right, but what I did was make the assumption the tailstock is reasonably in the right place, so I put in the larger live center, put the aluminum plates over that (with the bearing hole pierced by the live center, then tightened the chuck jaws around that, THEN made minute adjustments. Much easier it seems.
http://frederic.midimonkey.com/cnc2/IM001830.JPG

Turning down the leadscrew's ends so the bearings slip over:
http://frederic.midimonkey.com/cnc2/IM001832.JPG

Z-axis frame, rails, bearings, and easily rotated leadscrew:
http://frederic.midimonkey.com/cnc2/IM001833.JPG

Since I can't measure, I'll have to skim over the back of the saddle, to get myself a little clearance since the threads of the leadscrew lightly scrub on the back of the saddle. Not enough to prevent spinning by hand, but it doesn't allow the leadscrew to freewheel which it does when the saddle isn't installed.

Sucks because I used a punch, and a center drill, and still got the hole slightly off. At least it's consistantly off top and bottom so the leadscrew is parallel to the rails.

 

Are you using a cutoff tool to turn those shafts down?

 

Sure looks like a parting tool to me.

.....=o&o>.....

 

It's a parting tool, I think. It's a little more than 1/8" wide at the top, and a little less at the bottom, and about 5" long or so.

I have wider, thicker cutters, but I haven't mastered getting an edge perpendicular to the side of the BXA holder yet, so I've been using the parting tool because I got lucky when I sharpened it.

I presume from the comments this is not a good thing?

 

Nope... Have you got one of those lathe books with pictures on how to sharpen bits or better yet get a few carbide insert tools. On your lathe you could probably use 5/8" shank cutters. I would use 3/4 or 1" shanks on mine.

Check your tooling capacity and height but something like this is what you need:
Ebay Item number: 7625890739
Item number: 7625891669
These are 5/8" shank tools, two different tip configurations. The seller has a lot of tooling available and he may be able to advise you on the best inserts for what you are doing. I have lost track of the different types available. I have slept to many times since I was doing that. Also carbide insert tooling was fairly new stuff back when I was using it...

 

I have the BXA carbide holder for my tool post, and I use it for most things.

http://frederic.midimonkey.com/yard/...m-DSC00344.JPG It's the fourth holder from the right, and you can just make out the carbide cutting insert.

I didn't use it to turn the leadscrew ends. Well, I did on the first one but because the triangle inserts are rounded at the edge, I don't get a perfectly flat edge against the threads, where I've turned it down. For the bearing to have maximum surface area against the threaded part, I needed to cut that "square", so I used the HSS tooling instead, to try and get that.

With a rounded shoulder, the leadscrews are only supported by the very edge of the inner race of the bearing.

I have wider hss cutting/trimming/shaving tools, but I couldn't get the edge square. And if I angled it slightly so that the cutting edge was to the left, to make a nice shoulder, I couldn't cut the length of the area because it's too wide, and would hit the live center, leaving 1/8" of uncut area.

I did buy a machinist's handbook off ebay, from the mid 50's, which is certainly out of date but it has many diagrams and pictures of lathe operation similar to the lathe I have, so I thought it was a decent purchase. It has a ton of math and related information to calculate threads, threading angles, threading edges, as well as gears of all types, something I'm particularly interested in.

What I need to do is make a fixture for my grinder, so I can get a true right angle for sharpening, then I could easily use one of the other cutters than the parting tool. The parting tool is getting smaller as I keep sharpening it. When it's razor sharp it makes long spirals as it cuts, and as it dulls it starts making chips, then eventually a fine dust, then finally it doesn't cut and only squeeks. I try to sharpen it just as it starts to make dust to get the most use between sharpening, but before it blues which is what happens when it stops making dust.

BTW, thank you (and everyone else) for all the continual advice and suggestions, I'm learning exponentially with your help rather than ruining tooling and learning the hard way. I just wanted to make sure you all know I very much appreciate it!

 

Heck my little Atlas 12 x 36 tool posts all take 1/4" square tool bits.
A friend has a 24 x 60 lathe and small parts ar out of the question.
Ideal would be two lathes, that reminds me TigerDan has a large lathe he picked up last year.

.....=o&o>.....

 

That Machinist Handbook is fine for most purposes. They haven't changed much- I collect old ones. Another gizmo you might find handy, if you can find one to fit your lathe, would be a faceplate. It's just a flat plate that takes the place of a chuck, and it has various slots to dog down irregular shaped parts. It's great when you have a part that's not round, and you want to put a round feature on it. Just make sure whatever is clamped on there is tight, that the clamps won't interfere with cutting, and keep the RPM down. I once saw a 2 ton lathe dance across the floor when an operator accidently put it in high range with a 15 pound casting mounted off center.
A few other questions- are you using any kind of coolant or cutting oil? It will greatly extend the life of high speed tools. And do you know how to calculate the correct speed, depending on the RPM of the tool or workpiece? Look up 'Surface Feet per Minute" in your book. It'll be in there somewhere. PM me for further info if you can't find it. The rest of us are having fun watching your progress!

 

The carbide insets come with various corner radii. There are various tricks to turning a part and leaving a shoulder etc.

I can't really tell from the picture, does that tip with the carbide insert rotate to point in different directions? I have never seen one quite like it.

Cutting tools have various "hands" that you can read about in your lathe book. To cut a shoulder on the lead screw you would need a tool with a 1/32" radius like the Ebay auction #7625890739 above set up to cut right to left. The tool can undercut at the end of the cut to allow a square corner part to be supported on the shoulder and minor diameter. However standard bearings have a radius on the races to clear a radius in the corner. There are longer "nose" cutting tools with diamond shaped inserts also. Hitting the center should not be a problem with the proper tooling and setup. If you hit situations like that have one of your machinist buddies take a look. It takes time and experience to set up a lathe.

 

And money!
Tooling is killing me, the Bridgeport was cheap compared to collets and end mills. Without butting into Fred's thread, what would be the best set up for a cutter to surface heads on FE's as well aluminum motorcycle heads?

.....=o&o>.....

 

Frederic, you work very well. Can't wait to see the finished product.

Madmike33

 

some more progress on the z-axis. After a few attempts, I managed to make things work whereas when the leadscrew is rotated, the saddle moves up and down fairly freely. There is some minor play in the sliding, which can be adjusted by shaving the bushings ever so slightly. Probably easier to make new ones than to try and chuck a .155" wide bushing in a 12"x24" lathe

Since the back of the saddle grazed the leadscrew every so slightly, that leaves me zero clearance for a leadscrew nut, so i had to mill out a 3/16" strip down the back of it:
http://frederic.midimonkey.com/cnc2/IM001834.JPG

Clearance!
http://frederic.midimonkey.com/cnc2/IM001835.JPG

Back of the saddle, riding the leadscrew:
http://frederic.midimonkey.com/cnc2/IM001836.JPG

Inside of saddle, viewing the threaded bushing and the rod from the leadscrew nut that fits reasonably tight inside the bushing.
http://frederic.midimonkey.com/cnc2/IM001837.JPG

 

A flycutter, basically a steel disk with a carbide cutter mounted in it.

Frederic, -looking good!

 

I worked in a shop that decked blocks and heads. They had a special, one-purpose milling machine for it. It had a big (8") facemill that used 6 carbide inserts. You pretty much have to have a wide enough cutter to span the width of the head and then some. And if the spindle isn't absolutely square with the table, you will generate a hollow cut- not good for heads. I have made homemade flycutters out of a heavy bar of stock mounted to a spindle, with a slot and some set screws out at the end, which used a single carbide lathe bit. It's real hard to get a good finish; they like to chatter.

 

I'm burnt, so I'm done for the day.

The width of the machine (span) is unfortunately too wide for the weight of the Z-axis to ride upon, without minor bowing. Since I added a the angle iron backbone earlier, I decided a pair of patio wheels (ball bearing) riding on the edge of the backbone is a good (enough) solution. HOpefully this will solve the problem and allow me to avoid engineering the whole machine over. Whomever pointed that out several pages ago, next time I ignore you, poke me in the eye please.

http://frederic.midimonkey.com/cnc2/IM001838.JPG

Another view of the z-axis saddle, the leadscrew, and the nut-prong thing I made. Nothing too fancy, but since it's apart I figured I'd take a better picture than what's above.

http://frederic.midimonkey.com/cnc2/IM001839.JPG

Z-axis reassembled, leadscrew and saddle reinstalled, and the patio wheels ride nicely on the angle iron backbone. Looks like I'll have to do the same for the Y axis just below this as well.

http://frederic.midimonkey.com/cnc2/IM001840.JPG

And if you want to watch a 2.8MB poor quality avi file of the thing sliding around by hand, click here:
http://frederic.midimonkey.com/cnc2/IM001841.AVI