A square rotary table

[RReid]

Finally I could do the surfacing with a smaller 4 flute end mill, which would eliminate the thunk thunk thunk of the massive fly cutter.

I find that I prefer using a 4-flute over the flycutter in most cases, even though it may take a little longer. More forgiving of small errors in tram, and much smoother cutting. A very light final skim with the flycutter (so it just goes tick tick tick) may or may not be worth it. I usually don't bother, removing the machining marks by hand with wet/dry paper and a flat surface, but with a larger surface like you have I might.

Good luck with the RT and with the coming storm!

[vtsteam]

Thanks Kim, Ron! 

Well I got storm preparations finished in enough time today to do a small amount of work on the RT's base. The square tube is 2"x2"x5" and the plate is 4"x8"x1/2".  Here it is outside ready to grind the welds out. (....maybe  next time I'll do a neater job of it sticking it together....  ) As you can see the tube is offset to the right quite a ways. That really doesn't provide much support for the rotary table which is centered over the pivot hole.



I have some thin cutting disks and I got the two pieces apart fairly easily, and smoothed them up again with a flap disk. It was important to salvage the tube as an earlier 20 minute search through all storage areas, yielded no more 2"x2". I had all kinds of other sizes, of course.

I decided to move the tube over the pivot bolt hole to a position 1-1/2" back of the left edge in  the photo. To do that, I needed to drill a hole for the pivot bolt and an access hole above to allow a wrench socket through the tube for tightening it.

I measured a 3/4" wrench socket it was 1.020 OD. Oddly enough I happen to have a 1.032" drill bit. Not sure how I acquired that one -- I think it came with my used mill in a "box of stuff" they gave me. Anyway, a quick look at the end of that bit and it was obviously drill sharpening time.

Now I do have a "Drill Doctor" sharpener, but not for drills that big. But I have been practicing my hand sharpening on my bench grinder with an old 3/4" drill, and this was the perfect occasion to put that practice to immediate use. Not a problem, the drill was sharpened and checked against a drill gage, angles were right lips the same length, and it looked good.  I actually enjoyed that.

Then I set up the tube in my milling vise, got an origin and centered over the point I needed to drill. I first hit it with a 7/32" pilot drill, and then started drilling at about 400 rpm. That was going well, until I got some chatter and the big Jacobs chuck stopped turning (huh?) and it turned out that it wasn't a very good fit on its R8 to Jacobs taper. It simply had come off the taper.

I took the R8 spindle out, and tapped the chuck back on with a brass hammer. But I had it come off again twice before I was finished drilling. The chuck and spindle were another "box of stuff" gift with the used mill purchase. I'll have to see what I can do about correcting that.

Anyway I had the satisfaction of getting at least a small amount done today. It was too dark to re-weld the pieces, and besides, snow had begun to fall. But all in all a fairly satisfying bit of time in the shop. 

[vtsteam]

I was able to mill the table with an end mill as Ron suggested, after the above mentioned welding mods. Here's the re-worked table clamping base, now milled and painted, with the square tube moved to a better position.



The square tube was drilled to accommodate a wrench socket for tightening the pivot bolt. If a solid aluminum block had been used, instead, as in the video, it would have had to have been trepanned down to clear the pivot nut and washer in order for the base to sit flat in a vise. But the video constructor, simply offset the block, which is not as rigid an option.

Also, with regard to the video version, I'm not anxious to use grease between the table and the base.  I'm thinking that might be a swarf and dirt trap. Especially since the table and base are both rectangular instead of matching circular shapes (which would cover each other better). With the present shapes, large areas of greased base will be exposed to the milling swarf as I turn the table. I guess the aluminum swarf in the video is more forgiving, but I often mill steel and iron sand castings, which are quite abrasive.

As a possible workaround I'm going to experiment by inserting a shim washer made of high density polyethylene. In fact it's from another bit of scrap......a piece of a slightly used very thin cutting board that my wife tried in her kitchen and didn't like.

It's only .024" thick, so cutting out a  6" disk from the stuff was easily accomplished using a trammel cutter:








Disk made. I hope it works out without reducing rigidity too much. We'll see what the chatter situation is in use. I can always switch to the grease method. But for now I like the idea of this better.

And here are the parts so far, ready to be assembled:



 

[RReid]

I'm not anxious to use grease between the table and the base.  I'm thinking that might be a swarf and dirt trap.

I agree with you on that. That's one reason why my dividing head is stiff to use in RT mode. It has an open case, so I refuse to use any oil/grease on it, including the worm gear. With yours, if the HDPE doesn't work out (it should be slippery at least), I would advocate for oil over grease. Easier to apply just before use, then clean off after use. You won't be turning that thing fast, it has a nice long handle, and you probably want some friction in there anyway.

[vtsteam]

Thanks Ron,  I've still got to make a spacer washer for the inside before first trial. Unfortunately we were hit with another winter storm at 1:00 today, which will last through tomorrow. More plowing, so this RT build is going slower than molasses in January!

There are a few more issues I've had in trying to make this from the video. One I'll pass along to any others who want to do something similar is the rotating table shape. My closest initial estimate after viewing the video a few times was square and about 6" x 6" x 1", with the pivot centered. However there seemed to be a second table in the video, with a rounded end, and that one seemed longer than wide. No mention of the rounded end and longer table in the video, or the reason for the rounding, and its step.

After doing a lot of freeze frames since, I thought I saw the third rectangular table -- longer on one side. I've since come to realize that the three tables are actually just one. When I thought I saw the original square table, I was actually seeing an end-on view of the rectangular table. Because the center pivot was offset to the near end of the rectangle, the camera lens distortion made it look square with the pivot in the middle.

The rounded second table was just a later modification of the initial rectangular one. The rounded portion, which is stepped, appears likely to me to be a means of locking the table with a toe clamp. There are two tapped holes in the base plate in positions to add clamps for that relief. No clamps shown, however.

None of this is mentioned in the video, and scenes pan and cut so rapidly it's hard to notice these details. It would have been nice to know there was a clamping feature, since there is now no means for me to lock my smaller square table without cutting it down further to add that particular feature. However, I have my own plan for adding a clamp on the spindle, worked out when I didn't see any means of braking in the video. I made the spindle shoulder bolt longer in order to accommodate it.

Anyway, I'm now guessing that the original table was probably 6" x 7" x 1" with the pivot bolt strongly offset to 2" from the handle end, and then rounded opposite with a clamping step. My guess is that the base plate is 4" x 9" x 1/2", in that case, and the base bar is 2" x 2" and possibly 5" long.

[vtsteam]

In case it's useful for someone else, here's my best estimate of the dimensions of the video rotary table top. All radius dimensions are to the pivot center.  The curves can therefore be cut using the assembled rotary table from a 6" x 7" rectangular table top blank (although probably easiest if the corners are sawn off first) :

[vtsteam]

I turned up a spacer for the pivot today and then assembled the rotary table. The pivoting was really smooth with the HDPE washer and resistance was also quite adjustable. I didn't have a lock nut so just used a regular 1/2" x 13 nut and washer. I'll need to get a locknut tomorrow.

I did want to test the rig out today, so I turned a pilot spindle to 0.375" on the lathe from a piece of 0.500" drill rod. This fit well in the the .501" reamed pilot bushing. I didn't have a flat bar of aluminum at hand for a test piece, but I did have some 3/8" thick slotted steel milling clamps made from scrap many years ago. I decided to use one as my test piece and put a radius on it, while using another to clamp it down to the new RT.

This would be a good test, since the pitted salvaged steel wasn't free cutting, by any means, and I did want to give the table more of a workout than just cutting some aluminum. I think the majority of what I'll be using it for is cast iron and steel. The video RT showed only aluminum. I was curious how much back pressure there would be on the handle for straight milling with tougher materials, and how much vibration there would be.

Well, everything went better than expected. Milling was easy and smooth even with tough 3/8" steel. The big  knurled handle and the 15" pipe length felt just right, and I could mill quickly with very little effort. Everything felt solid and easily controlled. The cutter was quiet and cut efficiently. I couldn't have asked for a better result!



Tough steel milled:

[vtsteam]

So, this whole excursion into tool making was the result of the need to clean out the piston interior between the wrist pin bosses for the flash steam engine I was building. ......uh,....am building. Well also it will be handy when making the con rod.

I happen to have an ER40 collet chuck, originally intended for my homemade lathe. I was going to bolt it to the faceplate. But it also seems ideal for mounting on the new RT. I just need to drill and tap 4 bolt holes in each, and I'll be able to rapidly switch between the two. And in fact, it's just what I need for doing the clean out of the piston for my steam engine.

In order to mark out the hole locations for the new chuck on the RT, I first just put a suitably long length of .500" drill rod in the pilot recess:






Then I slipped the ER40 chuck with a 1/2" collet over it. This centered it over the table pivot axis. By rotating the whole chuck, I could use a transfer punch in one hole to scribe lightly over the rotary table's surface, so I could pick the best location for the mounting holes between the existing ones. I'll mark one hole first, drill and tap that one, then fasten the chuck down, before marking drilling and tapping the other three.





There are actually two bolt hole circles on the chuck's flange. One is a 4 hole pattern and the other is a 3. I'm going to use the 4 hole pattern for mounting screws, but may use the 3 hole pattern for a couple of temporary locating dowels. Then centering the chuck will be easy -- especially if it has work already in it.

[RReid]

Looks like a nice finish on that test piece. Glad it all came together!

[Kim]

That looks like a great little tool, Steve! 
I'm sure you'll find many good uses for it over time.
Nicely done!
Kim

[Admiral_dk]

Another Tool that you will be glad you made and enjoy using 

I do like that you also can fit you ER40 collect holder to it 

Per

[vtsteam]

Ron, Kim, Per, thank you all! 

[FKreider]

Thanks Dave and Ron!  I still use it, though my main lathe now is the second I've built, a 9" by 12" of my own design, which takes up the same bench space, but is much much heavier, and has split ways.

The 9"x 12" borrows a lot of design elements and component dimensions from the 12" x 36" Craftsman I also own, but also some constructional features I liked about the Gingery. I thought about it as similar to shortening the 12" x 36" down to a heavy mini bench lathe length, but retaining the original rigidity. The main reason for doing that was to have something that fit in the tiny workshop shed near the house.

I think I speak for everyone when I say that I would like to see a picture of this home made beast!

[vtsteam]

Thank you Frank.  I'll post some pics in a different thread at some point. Sounds funny, but I actually don't have a good pic of the whole finished lathe (yet), because I can't back up very far in my tiny workshop to get it all in! I do have a lot of pics of the construction sequence  back when I built it, but mostly that's casting and machining the individual parts. I'll see what I can do, if there's enough interest.

[RReid]

I'd certainly like to see it.