Oh boy, I did it again! PRAZI SD400.

[twhite]

This is a friggin disaster....

Heres some music while youre waiting for me to unfuck myself.

If anyone knows what movie the GTO and Gasser scenes were from PLMK.

Two lane blacktop with Dennis Wilson as the Mechanic James Taylor as The Driver. Loved that movie.


Cutting oil is my blood.

 

[RaisedByWolves]

Kinda took a fork in the road here as I had two projects that needed the 4 jaw chuck and figured Id knock them both out while I had the 4 jaw on the lathe.


First one was adding a radial and thrust bearing to the tailstock. If you are watching the other SD400 thread you have probably skip ahead to the oiler modification below as much of this is repetitive.


I wont go into great detail here, so basically I bored a hole .0005 larger than the radial bearing and made it a snug fit.

Then I bored a pocket for the thrust bearing. The blue portion in the back wall of the bearing pocket and you can just make out the step between the two bores if you look close, its kinda blurry.

With that done I test fit everything and found it all to work well. I stacked up the bearings on the quill screw shaft and assembled the whole works and function checked. It was at this point I realized I was not done, there is no provision from the factory to oil the quill screw bearing and no way to get oil to the bearings I just added.

Taking inspiration from the SD300 lathe I decided to install a small set screw to provide an oiling port.


Looking at it from the inside.

And all put back together. That makes for one less step to do. If you look at the tailstock back plate you can just make out the set screw for oiling.












And now for the 2nd job using the 4 jaw, modifying the oilers.

I looked all over to find some small oilers to provide a simple way of oiling the rear bed way on these machines and couldn't find what I wanted, so I bought the next closest thing and modified them.


I needed to fit this .750 tall oiler:







Into this .750 space on the back of the saddle. The red line represents the rear way and there is actually about an inch of room to the top of the cross slide ways, but I wanted to mount the oiler higher so I could angle the hole with a slight downward slope, hence the need to make the oilers as compact as possible. The red dot denotes the approximate location. It looks offset, but it is actually centered on the length of that way.











So into the 4 jaw they went. I had a hard time indicating these as their pressure cast zamak and nothing is round or square to anything I could find on earth.

I tried indicating the outside, but even where the flange for the cap retainer rides was wildly out of round.









So I settled on indicating the bore.









Even that wasn't great, but I was able to get it within .002 radially and axially (I think) and figured that was good enough.



Then I turned off the old spigot and flange.







Took off the peak of one of the hex shape of the body to lend some extra room.







Then turned a new spigot and retaining groove.







Perfect!







I then assembled it all back together. Better than the day it was made and .225 shorter than it was.









With that excursion completed Ill get back to the apron gear train and get closer to final assembly.

 

[Pevehouse]

Kinda took a fork in the road here as I had two projects that needed the 4 jaw chuck and figured Id knock them both out while I had the 4 jaw on the lathe.


First one was adding a radial and thrust bearing to the tailstock. If you are watching the other SD400 thread you have probably skip ahead to the oiler modification below as much of this is repetitive.


I wont go into great detail here, so basically I bored a hole .0005 larger than the radial bearing and made it a snug fit.

Then I bored a pocket for the thrust bearing. The blue portion in the back wall of the bearing pocket and you can just make out the step between the two bores if you look close, its kinda blurry.

With that done I test fit everything and found it all to work well. I stacked up the bearings on the quill screw shaft and assembled the whole works and function checked. It was at this point I realized I was not done, there is no provision from the factory to oil the quill screw bearing and no way to get oil to the bearings I just added.

Taking inspiration from the SD300 lathe I decided to install a small set screw to provide an oiling port.


Looking at it from the inside.

And all put back together. That makes for one less step to do. If you look at the tailstock back plate you can just make out the set screw for oiling.






View attachment 505707





And now for the 2nd job using the 4 jaw, modifying the oilers.

I looked all over to find some small oilers to provide a simple way of oiling the rear bed way on these machines and couldn't find what I wanted, so I bought the next closest thing and modified them.


I needed to fit this .750 tall oiler:



View attachment 505709



Into this .750 space on the back of the saddle. The red line represents the rear way and there is actually about an inch of room to the top of the cross slide ways, but I wanted to mount the oiler higher so I could angle the hole with a slight downward slope, hence the need to make the oilers as compact as possible. The red dot denotes the approximate location. It looks offset, but it is actually centered on the length of that way.





View attachment 505721





So into the 4 jaw they went. I had a hard time indicating these as their pressure cast zamak and nothing is round or square to anything I could find on earth.

I tried indicating the outside, but even where the flange for the cap retainer rides was wildly out of round.


View attachment 505710






So I settled on indicating the bore.




View attachment 505716




Even that wasn't great, but I was able to get it within .002 radially and axially (I think) and figured that was good enough.



Then I turned off the old spigot and flange.



View attachment 505711



Took off the peak of one of the hex shape of the body to lend some extra room.



View attachment 505712



Then turned a new spigot and retaining groove.



View attachment 505714



Perfect!




View attachment 505713


I then assembled it all back together. Better than the day it was made and .225 shorter than it was.




View attachment 505715




With that excursion completed Ill get back to the apron gear train and get closer to final assembly.

I love to watch the way you work. Your an amazing machinist sir

 

[RaisedByWolves]

I love to watch the way you work. Your an amazing machinist sir

Thanks, glad you're enjoying the ride.

Hopefully walking through the steps, and the thought process involved with the problem solving with help others in some way.



I have a bit of catching up to do so this may take several posts.

After making the new shaft I needed to figure out a way to fix the large gear to the shaft its self for positioning it without resorting to the near impossible task of realigning and reaming the out of center tapered pin hole. I had already bought the reamer and pins, but as I mentioned earlier this just seems to remove too much metal from the shaft from a strength and rigidity aspect.

So I came up with the idea of using dog point set screws. Here is the shaft with the spot faced recepticals for the set screws.







With this done I test fit everything and took some more measurements.


The new rack gear next to the original with the big gear mounted to the shaft and in position..







And the new gear mounted to the shaft temporarily to get some measurements. Not shown is a .020 shim I made behind the large gear to set it out from the casting so it wouldn't rub.


New gear is a thick boi!







What I neglected to get a pic of was the new gear turned down with all of the excess removed, but you will see that in another pic.

I needed to come up with a way to fix the two gears together as I didn't like the idea of just 4 set screws transmitting power for this application. Under normal use it should have been fine, but any extra curricular activities may have compromised this arraignment. So I decided to key them together.


I was in a quandary at this point as I didn't have a simple way at home to hold the 1.5" large gear to mill it. What I decided on was to use the new rotary table for this job, not as a rotary table per se, but more of a milling stage for ease of clamping and positioning.

This of course meant I had to up my rotary table clamping abilities. First up was a simple bridge clamp for the foot end.







The rotary table has a MT3 taper in the center and a depression surrounding that, so I had to make up a hardened and ground disk to fill this so I could clamp the work. You will see why in a bit.







Then I needed some T nuts and found just the thing left over from an old machine I had. Never understood why these came with that machine, but they fit (kinda), and were free, so I modified them to fit. I had to shorten the height of these and also one end and chamfer it so they would snug up closer to the center of the table. You can see the threaded rod gets right in there now.









Then it was a simple matter of using my custom made mill clamps in conjunction with the T nuts to hold the gear in place. I had centered the rotab earlier and was able to easily center the gear with a 5/16" dowel pin and clamp it down.






Then I milled a .060 deep .250 wide slot in this gear. For a slot like this you want to use the next size smaller end mill and do the math(Gasp!) to figure out how much to offset the machine to give you a perfectly sized slot.

I matched it out and came up with .0625 total, so roughly .031 per side, and cleaned it up to size from there.

 

[RaisedByWolves]

Then I set up the smaller gear with its now reduced shank, again using the dowel pin, clamped that down and in preparation of milling the sides to leave a key centered on the bore.








For this step I blued the gear and took a ghost cut,(just enough to remove the bluing) in order to check my math and it came out looking good, so I proceeded.






Then I milled the sides of the shaft to form the key. I purposedly left an extra .002 per side to account for the small mill flexing figuring I could easily clean it up if need be.








As it turned out that was a good call as after deburring the freshly cut gear and mounting the two gears onto the shaft everything came out perfect.









You cant see the shaft in that pic, but I was so stoked with how well this critical step turned out I wasn't really focused on capturing the whole scene.

It went together so well and precisely I let out an audible "No ****"!

I still have to bring the small gear to length and add a retaining screw to the end of the shaft to hold it all together, but so far Im really happy with how well this turned out.

 

[RaisedByWolves]

I decided on keying the two gears together as this lets one gear transmit power to the other without relying on the shaft, and more critically the set screws alone. The shaft only revolves in the bore and had no torque imparted on it this way.

Here’s the gears together on the shaft with the shaft at the correct length. I’ll often make the part with plenty of excess and trim it down and finalize the sizes as things progress.






And here is the new rack gear, old large gear and shaft next to the old rack gear. You can see there is plenty of extra gear left if I need to make and final adjustments, but I think it’s good where it’s at. I had to stop turning it at this length as I needed enough meat in the collet to support it well enough.









In the first pic you can see the shaft and gear are the same length. I needed to shorten the shaft to allow for a retainer and retainer pocket to be formed on the end of the gear. I turned .100 off of the end of the shaft, drilled and chamfered it for tapping.










I carefully tapped it by hand turning the chuck and stopped when I felt resistance.








Now I didn’t want to just bore an overly deep hole as this would weaken the shaft, so I only drilled about 1/2” in.

With the tap bottoming in the hole I was only able to get the screw about 2/3 of the way in.

To get more thread depth I modified the tap by grinding the tip back about a 1/4”.








Then I went back and tapped the hole deeper with my tiny little watchmakers tap handle. This thing is only a little over 2” long and gives excellent feedback to the cutting action. For tiny screws where breaking the tap at the last stage of machining would scrap the entire part, tools like this are a must.







This type of tap pushes the chips ahead of its self and packs them into the bottom of the hole.

I custom make special chip hooks by heating the tip of a scriber and tapping it into the head of a 10-32 socket head screw, which forms it into a nice curlycue. Then I dress the formed hook on the belt sander to the profile I want.







A small magnet attached to the shaft of the pick gets the last little bits of material out of the hole.








With that done I get better than full depth on the screw. I say better than full depth as in the chamfer pic you can see the chamfer is very deep. This is due to the screw heads taper measuring .125-.135 and the retainer I’ll make will only be .100 .










This very deep chamfer on the threads allows a portion of the base of the screw head taper to enter the shaft without bottoming out preventing proper tightening.

 

[RaisedByWolves]

Next up was making a pocket in the end of the gear to accept the retainer button. The shaft is .3125, so I simply used a 3/8” endmill and made the pocket with that.









Modified gear mated to the shortened shaft.











Now it was time to make the retainer button. An easy enough part to make, but things don’t always go as planned.

I turned a piece of 5/8”
O-1 down to .380 to closely match the oversize hole the endmill cut.



Short video taking .080 cut with this machine. I had just resharpened the tool bit and with the fresh edge I have no doubt a .100 or even a .125 cut is possible, but I didn’t want to push it and have to again touch up the tool bit just to experiment.


No idea how this wound up sideways, or a short, so I’ll try to correct that if possible. Sound didn’t come through either.

https://youtube.com/shorts/GXvYPwSFfic?si=SYfGOSDDT5z-rLBD

Look at that finish! And did you notice there was barely any spring back when I retracted the bit?








Now it was just a matter of drilling the clearance hole and chamfering the button to accept the entire head of the bolt, then parting it off. Again, I needed to sink this in fully as I’m close on my tolerances.










Parting off.












And…… that didn’t go well at all. I didn’t get a pic but the blade wandered a bit, probably needs a better angle, so the button came out cone shaped on the back.




Sooo, it goes back in the 3 jaw to correct this. This is sometimes a PITA especially on a small part like this with not having much to grip and not wanting it to come out all wavy and out of spec.


So I pulled out a tool you need to make if you don’t already have one. A bearing bump tool.

I simply chucked the tiny part up firm as I dared as to not deform it, and ran the bump tool into it until it was running true and I had minimal stickout.









Then I took a cut to clean up the back. I was lucky the blade wandered in the direction it did which left me with a thicker part rather than a too thin one. .015 cleaned it up nicely.


Here it is on the end of the gear next to the pocket where it will live.








And the whole works assembled for the time being. I need to grind the dog points down on the set screws and trim the socket side a bit, but for now this part is pretty much done.










I still need to harden the shaft, but that will have to wait until I do the final fitting.



.

 

[Dabbler]

@RaisedByWolves you are doing great work! Nice save on that lathe!

 

[RaisedByWolves]

@RaisedByWolves you are doing great work! Nice save on that lathe!

Thank you. Save for a little minor wear this machine will be better than the day it was made when I’m done.


I got a new phone with a better camera so hopefully I’ll figure out how to use it and take better pics.

One thing that bothers me about these machines is the lack of oiling buttons or cups from the factory. Brushing oil on with an acid brush is what’s recommended, and it works but it’s tedious and time consuming.


So about that shortened oil cup….



I set the saddle in the B-port and after taking careful measurements found a location near the center of the rear way that would not intersect with a nearby gib attachment screw hole, and drilled it for a 6mm-1 thread for the oil cup.


The Allen key denotes the depth of the existing screw hole I’m trying to avoid and the location of that hole….tight!







I had less than 5/16” of depth in this hole so again I shortened a tap.








With the hole tapped I test fit the oil cup and while really close to the top of the ways, it fit without any interference.








That’s just a parallel on top of the ways, but I’m pretty sure there is more room under the slide than this.









Then I needed to cross drill the oil gallery to get the oil to the ways.



I set it up on a random angle that would let me get deep enough to reach the center of the back way and drilled it to the proper depth.

Checking depth and setting the quill stop.











Once I had that set up I had to spot face the bottom of the hole as it was angled from the drill bit tip. I went in with an 1/8” 3 flute endmil to make the spot face.









I was able to use the fancy new camera on the phone to inspect the operation as I worked which was great as I didn’t have to move the machine it break setup to check progress.
I just hovered the phone between the part and the drill chuck and viola, x ray vision.










Then I center-drilled and checked that.








After that cross hole was drilled I set up and located the position for, and drilled the rest of the oil gallery through to the face of the way.

 

[RaisedByWolves]

Ran out of space for pictars.

I drilled the oil gallery hole nearly perfectly at the end of the cross hole, very happy with that. If you look closely you can just make out the crescent where the cross hole and the 2nd hole intersect.










Then I set the saddle up on the mill and using an 1/8” ball mill made the oil groove.


The scratches look much worse than they are, about .001 when checked with an indicator.










With that done my attention turned to the oiling of the front V way on the saddle. This way gets oil through a slit in the saddle centered on the inverted V way, and while this works OK, I figured while I was here I would give the oil a lil help.


I angled the saddle slightly in the mill and using the same ball mill made a sloped oil groove leading to the oil slit.










The cross slide lead screw lives in this u shaped slot and comes in from the left hand side, so winding the cross slide fully forward allows you to oil the screw and add oil to the slot sidewall which will eventually get to the way. My addition of the oil slot just makes this a more positive action with less oil used to get it to where it’s needed.


Top view.









And a pic of the other lathes saddle and the area I spoke about above. The arrow points to that slit and you can see there’s not much room to get at it, hence the need to just put a few drops of oil in there and let gravity do the rest.










I’ll need to add oil groves to the face of the V way later with a carbide burr in a hand grinder, which I’ll probably do tonight.