The Shop > Tools
Home-brew 120mm rotary table
arnoldb:
:beer: Cheers BlueRock & Ray
:lol: rleete, yes, they're darn ugly :lol: - in fact FUGLY :lol:
:beer: Peter & Dave, I've only heard Dave's voice... :Doh: Not sure if I'd like to see his face after that :lol: :lol: :lol:
Nah... If I get to "Gauteng" with a couple of hours to spare, I'd happily meet up with Dave :D
01 May 2010
I first faced off the one side of the welded base frame in the mill. I made a couple of quick clamping plates from more of the flat bar I used for the base - just saw off and drill an 11mm hole to allow some pivot clearance for a 10mm bolt , and sawed the heads off a couple of 10mm bolts to make shorter clamping studs than are in my clamping kit. The "new" clamping plates was needed as the clamping plates in my clamping kit is too thick for the slots I milled in the base. (Two years later, and these same ad-hoc clamping plates still hold down the RT in use!) T-nuts and the clamping nuts came straight from the clamping kit. I cleaned the mill table VERY thoroughly before clamping down the piece on a bit of paper to prevent it slipping:
Then I flipped it upside down to do the other side. Same process as above - clean and a new piece of paper. With the slots now higher above the table, I needed thicker spacers for the off-set ends for clamping... I settled on using some of the triangular step blocks from the clamping kit; a small one and larger one combined to provide the height. I couldn't use the flat bar clamp plates as-is on just one triangle block, as it is both a bit soft and too rounded on the ends to ensure a good grip on the step block. I don't recall ever seeing step blocks used in combination like this to , but it worked a treat :headbang: :
It was a public holiday here in Namibia... I forgot about it... Completely... Imagine my surprise when I pitched up at the bolt & nut store to buy some M5 cap screws for mounting the base plate to the frame :palm: Not having those, I could not carry on with the base, so I started on the table.
The lump of cast iron centered near-enough on the 4-jaw. Neither of it's faces was particularly square, so I chose the "best" one to go into the chuck:
As I would be doing some "interrupted" cuts because the workpiece is not entirely round, and having a skew face, I center drilled it first, and added a revolving center. This was purely a precaution to make sure the workpiece stayed in the chuck if something came loose or jammed up. Some thoughts, a prayer and a thumb-suck made me select high back-gear speed on the lathe for cleaning it up on the circumference. This worked quite well, but my first cut was a bit on the shallow side (0.2mm), and quickly revealed a hard spot in the C.I. skin:
So I re-sharpened the toolbit (that hard spot just flattened it), and took a 0.5mm (0.040") cut to try and get under the hard spot. Instead of using the apron wheel for feeding, I locked the carriage nut, and used the lead screw handwheel for feeding; that gives a finer feed than the apron wheel. This cut came out much better:
Next I faced the front down as far as I could - this face was far out of square, and with a 0.01" ( 0.25mm) infeed per cut on the topslide, with the apron locked on the bed it took a couple of passes (8 in total) to get here:
02 May 2010
First up, I finished facing the piece - with tailstock removed. then I drilled a pilot hole through with a 7mm drill bit - pecking all the way to try and keep the hole as true as possible. The 7mm drill was just long enough for the job:
Then I drilled the pilot hole out to 13mm, and re-sharpened the tip of the carbide tipped boring bar that I broke earlier in the build, and bored the hole to 16mm dead. A test with some 16mm silver steel and I got a light push fit; precisely what I wanted. Then I bored the recess for the mounting flange with light face cuts from the inside to the outside with a HSS toolbit that I ground to a good shape for this type of job on a previous occasion. This is part-way done:
Next I made the needed undercuts on the face. They came out a bit rough on the surface, as I used a threading tool to make them. Fortunately the running faces are nice and smooth - that's where it matters most for this project. Next up, it was the clamping groove. I did that with a parting tool and the lathe at its absolute lowest speed (back gear low speed). This was still slightly too fast, and I ran into problems with chatter. So I added the tailstock back for some additional support; fortunately my revolving center has a couple of different tips, and I could fit a bigger one to use with the 16mm center hole. This didn't help a lot though, so at the risk of chipping off the parting tool bit tip, I increased rate of infeed. Fortunately this worked and I soon got into the "groove" with nice chips coming off the parting tool and no chatter. A couple more passes with the parting tool, and I had the groove done:
I removed the 4-jaw from the lathe with the table-in-making still mounted on it, and set it aside. The 3-jaw went on, and I started on the main shaft. First off, cut a bit off the big bolt from the first photo in this thread:
Then gripped in the outside jaws of the 3-jaw on the non-threaded part of the bit of bolt, I lightly faced off the end and center drilled it for tailstock support. Then I rough-turned it down to get rid of the threads and then down to 26.5mm - this section will later be turned down to 25mm with some other steps and sizes included:
04 May 2010
I flipped the main shaft-in-making in the 3-jaw, and turned the flange section that mounts into the back of the table. The outside of the flange actually becomes a register to keep the shaft concentric with the table, and was turned as accurate as I could for a light push fit into the hole in the table. For some reason I got a poor surface finish; but could not do anything about it. This photo shows the part with the right hand section turned down to "register" size and the end already faced:
Next I used a right-hand left hand knife tool to remove the excess metal and get the flange down to the needed 6mm thickness:
Action photo of drilling a 13mm hole part-way through the shaft - I love it when the swarf comes out in nice consistent curls like the ones lying below on the apron:
Boring the hole out to 16mm - after each pass I had to stop and remove the "rat's nest" that formed:
And done with the boring; the 16mm silver steel rod is a smooth fit in there - it acts like a piston and with the air trapped in the blind hole it pushes itself nearly right out again - I wish some of the pistons and cylinders I made so far was that close:
For the next bit I could have done with a rotary table :Doh: ... I was too lazy to set up the dividing head in the lathe. So I decided to use the 3-jaw chuck as indexing device on the mill table. I clamped two blocks about 60 degrees (relative to the chuck outside diameter) to the mill table, and for the third side, I used a clamp and step block from the clamping kit. To mark index, I used the little square shown and just lined it up with its lower edge parallel to the T-slot, and used one of the chuck jaws sticking out slightly to get the first index position:
I centered the chuck using the table feeds and a bit of that 16mm silver steel in the drill chuck to go into the hole, zeroed the X handwheel and dialled in the 17.5mm offset I needed. Drilled the first hole, loosened the clamp, rotated the chuck against the fixed blocks to maintain position, and indexed with the little square on the same "side" of the next jaw. Clamp down the chuck again, drill & repeat for next hole... QED :headbang: :
Next the holes needed countersinking from the back side... My countersink bit was too big, and waaay to short to reach in there. A broken 8mm drill bit volunteered, and I carefully ground its end to a 90 degree angle with suitable cutting faces. That made countersinking easy, and the holes turned out quite well with no chatter:
The last step, was to punch a witness mark into the flange and the back of the table; these I then "connected" with a scribed line - this will be used to make sure everything can be put back exactly the same at a later stage:
Progress thus far:
:beer: , Arnold
Rob.Wilson:
I will keep stum about your welding Mate :palm: good job its on the inside :poke: :lol: :lol: :lol: :lol: :lol:
I did show J , and she replied well at leased he has 10 engines finished :bang: :bang: :bang: mumble mumble
Rob :)
rleete:
That's one big lump to be turning. I'll bet it weighs nearly as much as my entire lathe.
ksor:
I've seen that before ... oh, it's a little like mine from 2010 :) - but how can a round table be made otherwise :doh:
Even the locking mechanism are nearly the same - now I have to get mine done :scratch: i a hurry !
Look here: http://kelds.weebly.com/rundbord-140mm.html
arnoldb:
:beer: Cheers Rob. :lol: :lol: - So J's lost count; good for you though, as it's something like 16 or 17 engines now :lol:
Cheers Rleete :beer: - not too big a lump though, as it is within my lathe's capability. It only weighed about 3 times as much as the 4-jaw chuck :thumbup:
:thumbup: Nice start Keld :beer: - Finish it; you won't regret it. I like the ball bearings for the table to run on!
05 May 2010
First I turned up a close-fitting transfer punch for the holes from some silver steel (drill rod):
That was heated up to bright cherry / cooked carrots colour (For me its orange-red ) - hot enough to heat-treat, and dunked in some old motor oil I have for this purpose to harden it.
Then I used the punch to mark the table for the screw locations; simple; keep the alignment mark I made aligned; the punch is a close fit in the holes and stands upright by itself in each hole; and a good whack with a hammer on it and each center is marked:
I carefully centered and drilled each hole 4.2mm and 7mm deep on the mill with the chuck clamped to the table. After each hole, I used the drill chuck as a guide to run in the first tap from my M5 tap set. It only left a couple of threads on each hole before bottoming out, but enough to start the 2nd tap outside of the mill on the workbench. Each hole was run down with the second tap till it bottomed. Then the holes were run through with my modified version of an M5 plug tap - it had a pointed tip that I ground down while building "Fred" to really thread some holes to the bottom:
I'd purchased some Allen drive M5 countersink machine screws earlier the day. :bang: - when I measured everything initially, I only had some slotted head ones available, and the new ones' heads were bigger. I turned the excess off using the collet chuck in the lathe, but now the screws stood slightly too high. I didn't want to face them off, as the hex sockets in them are not all that deep, so I'll make the countersinks on the flange a bit deeper later on if the heads interfere with the bearing. I wanted to use these screws, as they are high-tensile steel compared to the soft galvanized slot-heads I had. Final bits at the end of the day - screws in place and a "quicky" transfer punch:
06 May 2010
I mounted the 4 jaw with the table/shaft assembly back on the lathe. I know my 3-jaw grips eccentric by about 2 thou - but dead parallel from the chuck to about 100mm away from it - on a 26mm workpiece, and when I tested the shaft on the whole lot as mounted now with a dial indicator, that's what I got. About 0.05mm eccentricity along the shaft's entire length, but it was parallel. The outside of the table part as mounted was still spot-on center. So I carefully turned down the shaft part to the needed 25mm for the bearing inner race; it was at 26.5mm so for a first cut I just took off an infeed of 20 thou (that takes _just) over 1mm - off the total diameter). Then I measured the piece to be sure - it was down 25.48mm. I honed the cutting bit in-place on the lathe; just a couple of light touch with the oilstone - then went down to just over size at 25.1mm. A last cut part-way for the last 0.1mm, and I stopped for a test with the bearing and it lightly pressed over - so I finished the cut:
Not super-smooth, but I'm happy with it.
And a final test; the bearing goes on all the way with a light push - just "some" pressure required :) :
Next I turned the shaft down to 24mm up to a point 15mm away from the base of the table; the bearing is 17mm thick, and with the slight indentation in the table and the offset lip in the bearing mount hole in the base, that leaves me room for threading and run-out to the bottom of the bearing inner race. The 24mm section will be single-point threaded at 1mm pitch for the bearing pre-tensioner nut. I stopped short of the threading; that will take a while, and had better wait for the weekend.
Looking for something more to do, I decided on doing the holes to bolt the base top to the frame. I forgot to mark out the circle the table would run on on the base top plate, and being hit by a sudden sense of aesthetics, I needed to "see" a ring on the base top plate where the table would run. I pressed the bearing in the plate, and fit the whole lot over the shaft and used a permanent marker to mark the outline of the table on the plate:
With the mentioned aesthetics in mind :coffee: , I marked out and punched for the centers for the hold-down cap screws:
I stopped there, as while punching the holes, I found my concentration wandering to what I'd have for dinner, and also distracted by the swarfmagnets (dogs) bashing around their stainless food bowls (must have had the same thoughts :lol: )
:beer: , Arnold
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