The Shop > Tools
Home-brew 120mm rotary table
ksor:
Really nice work :bugeye:
sdezego:
Very nice work and write up this far :beer:
arnoldb:
Keld, sdezego - Thanks Gents :beer:
25 May 2010
I made the hand wheel and adjustable scale; quite a bit of shop time, but came out OK, and the only interruption I had was a friend pitching with some meat to stock the freezer - that was most welcome!
Started off with a hunk of aluminium:
That I then turned down into the handwheel shape, with a boss on the front where the scale would locate on. Here it's all done and ready to part off:
Soon after starting the parting cut, I ran into chatter problems, but only on one section - the next photo shows the bit with chattering, while the rest of the groove is nice and smooth. I noticed while turning that there was a section in the aluminium rod that was harder or softer than the rest, and this is in that section:
To overcome the problem, I slowed the lathe down to the next lower speed, and also started a "double parting" cut; this particular parting cut would be pretty deep - from about 50mm diameter down to 6mm and a double parting makes things a lot easier, even if wasting some material:
I didn't want the finish on the part ruined when it dropped off on breaking through on the parting cut, so I shoved a slightly smaller rod mounted in the tailstock chuck into the hole when things were getting close:
After parting; not very neat on the cut side:
I cleaned up the untidy face by lightly gripping the part in the chuck with some soda can "protectors" and lightly facing off the offending bit. Then I mounted it on the RT for some final measurements. The face closest to the camera was the "bad" one above:
Next I started on the graduation wheel. Some 40mm aluminium rod with the end counter bored for a light push fit with the boss on the handwheel, and then just slightly cleaned up on the diameter, and with the parting tool a light groove turned to about 39mm diameter, so that I could knurl the projecting bit:
( :palm: I REALLY need to make a cleaner-looking and less sloppy knurling tool! )
After that, I parted the graduation wheel on length from the parent stock. Then I mounted the handwheel and graduation wheel together with a cap screw, and mounted the lot in the 3-jaw, protecting the handwheel bit with some more soda can strip. My 3-jaw's outside teeth are still pretty accurate (less than 1/2 thou run-out on most diameters) - so good enough for here without resorting to the 4-jaw and centering. Next I turned the excess off the diameter and most of the face of the graduation wheel:
The dividing head was still set up in the mill, so I transferred chuck and all to that. A quick check, and I needed the dividing plate with the 45 hole circle. Mounted that, and then set to marking the graduations. The one and 1/2 degree marks were easy; my DH has a 60 tooth worm, so for the "one's" its "start at zero; graduate, 12 full turns, graduate; repeat". To get the halves, just crank six turns and repeat as for the tens. For the 0.1 degree marks, it was a bit more work; 1 1/5 turns per mark - but a LOT quicker than the 10s and 5s on the main table :D - Here I took a break from counting and marking the 0.1s to take a photo - My mind was starting to wander so some timeout to restore focus after a careful note of current settings:
The handwheel still needed drilling and threading for a grub screw to mount it on the shaft. Here I'm using the old trick of using a flat plate (old feeler gauge plate) to find the center on the circumference to drill:
This method can be pretty accurate, but there are caveats...
In many descriptions of this method, a rule is used to do this. I don't like using a rule, as the engraved markings on a rule can have a negative effect. (anyway, good rules costs money :coffee: )
One needs to check with the drill bit rotated to a couple of different angles and judge the "average" level.
A new spot on the plate should be selected for every test.
Don't move the workpiece while the drill press is under pressure; lift away the drill bit, move the workpiece or rotate the chuck and retry.
The smaller the diameter of the workpiece, the more accurate this method becomes (if you choose new bits on the plate for pressing down on, and don't use a rule where the engraved markings can cause a problem, and check with the chuck rotated a couple of times).
Gravity does have an influence if you're working with light pressures; try and have the plate balanced on the workpiece before starting.
Getting ready to knurl the handwheel - simply fit to the collet chuck with a cap screw from the back, and a nut pulling the wheel up to the chuck face. My biggest knurling job to date on a VERY "iffy" setup... This is at the extreme capacity of my rough knurling tool, and to boot, a knurling job wider than the knurling wheels... There's a LOT of sideways slop in that tool :palm: :
LOTS of coolant/lubrication from the synthetic soluble cutting oil squirt bottle (mostly to wash away any swarf build up) and the job was a good 'un; not perfect, but entirely acceptable for me for now.
Next up I turned a shaft from 6mm silver steel, threaded M5 male one end and M5 female on the other (to accept an M5 cap screw), roughly turned, and finished with a file & emery a handle and drilled and counterbored it to take said cap screw and shaft, and parted it off 0.2mm shorter than the shaft. A bit of stiff spring salvaged from an old printer, shortened with the Dremel and ground down to length on the bench grinder, a couple of washers, a grub screw, and a short length of brazing rod all resulted in today's collection of parts:
And duly assembled as a handwheel with zero-able scale:
I'm quite happy; that lot came together rather well. The scale takes a "nice" amount of effort to adjust and does not slip on the handwheel at all.
Making the vernier scale on that zero collar is going to be a bit of a challenge, but I have some ideas around that :med:
:beer: , Arnold
ksor:
In fact your BEEP weldings inside doen't matter with that outside - a perfect tool ! :clap: :clap: :clap: :clap: :clap:
arnoldb:
:beer: Thanks Keld - it's far from perfect though!
29 May 2010
I faffed around with the vernier collar and some number punches - and ended with a mixed bag of results...
Having done the calculations for the vernier collar, I set out to make a template to mark it off it from. I cheated a bit, and instead of manually laying out the template with a pair of compasses, I did it with CAD and printed it. I know my old HP laserjet 6L prints very nice and accurate circles from QCAD, so no worries there. (A couple of years on, and my old Laserjet 6L still prints great :headbang: )
Next I cut a "round" piece of plate from an old computer casing - here it is roughed out with some tin snips:
I just took it to the bench grinder to get it nice and round and without sharp edges - no finesse with a file, as this is a quick 'n dirty...
I used the compass to cut out the template from the printed page as well; I keep my compass fairly sharp, so it does cut paper albeit a bit crudely. At one point, I made a booboo and let the center slip, but not too much of a concern:
The paper template needed to be glued to the round plate... I didn't have any suitable glue on hand, so I used an ancient can of clear lacquer I've had for years (12 to be precise!) to spray a thick coating on the plate, and then stuck the paper template to it while the paint was still wet. Just for the heck of it, I ran another coat of lacquer over the top:
I didn't bother cleaning my hands so there are oily smudges all over the paper :palm:
After leaving that lot in the sun for about 20 minutes to dry, I centered and clamped it on the drill press. Thoroughly. I needed to drill a 16mm hole through the center, and plate is a bugger on break-through:
All drilled; no fuss or drama :headbang: :
Next I turned a mandrel from some 20mm aluminium rod - to mount the vernier plate on one side, and a 16mm shank to grip in my collet chuck on the other side, with the template between the collet nose and the shoulder on the mandrel - here the vernier plate is already mounted on the mandrel:
I fully intended to take photos of how I clamped this lot together on the collet chuck... and promptly forgot to take any :palm: . I mounted the collet chuck on the lathe, pushed the mandrel through the plate and into the collet in the chuck, and used the tailstock to press on the mandrel while tightening the collet closer. This kept the plate tight between the shoulder on the mandrel and the collet nose; I didn't want it to rotate later on.
Then I took the collet chuck with its contents off the lathe, and screwed it to the dividing head still mounted on the mill. For this job, the dividing head is useless for making the graduations (that's why all the fuss with a template) - but is useful as a handy mounting to make things go around.
Needing a way to index off the template, I taped my scriber securely to the magnetic base arm with some insulation tape, and set the lot up on the mill - with the scriber point very nearly, but not quite, touching the template:
Then I milled the markings; I made the template to conveniently show the lengths, so this was pretty much a no-brainer to do - except to get the scribe point as accurately on the line for each graduation as possible. I ended up with this:
Quite proud of my achievement in making a vernier scale, I put it on the RT and tried it out.... :doh: :doh: :doh: :bang:
The scale is good - for working to 0.01 degrees. Those short 0.005 degree markings are completely useless... Had I stopped earlier this week and really thought things through, I would have realised it... The handwheel collar does not have 0.05 degree marks to align the vernier marks to in the 1/10th scale I made it at. To get the 0.005 vernier scale to work, I either have to put on the 0.05 marks on the handwheel collar, or I have to stretch the vernier makings through 18 divisions on the handwheel...
At that point I didn't know whether to kick my own butt, or to cry. Instead I ended up having a good laugh at myself for being too clever for my own good, and I'll leave things as is. The small half-marks on the vernier plate can serve as a future reminder that it's possible to do some nice work off a crude template and setup, that I need to think things through more clearly, and that sometimes I just need to laugh at myself. If the marks bother me in future, I'll make a new vernier plate. With my tests, I found that it would in any case be very difficult to index to 0.005 degrees using the 72 tooth gear wheel on this size. The 0.01 degree marks are good to use, and when I set out on this project, that was what I had in mind anyway.
(I still laugh at myself to this very day for this silly mistake :lol: - every time I look at that vernier collar. the 0.005o accuracy would have been a waste anyway; I've not needed accuracy greater than 0.01o :D )
Next up, I marked my set of 3mm (1/8") number punches with a permanent marker. The numbers on the punches are oriented so that when the punch is held upright, and I can read the number, the punch is the correct way around to stamp the number properly:
What, no 9 :scratch: - here it is; it's on the "other" side of the 6 punch :coffee: :
And another crude jig to stamp the numbers. A slot milled through the face of some scrap HRS, and mounted on the magnetic base, mounted on my steel workbench serves as a punch guide. A small drill vise clamped to the table to hold down the workpiece, and I aligned the work with the end of the fixed jaw in the vise to set the depth:
It worked sort of OK - Ideally I should have stamped the numbers on the workpieces while they were all still mounted in the lathe chucks, but I'd rather take some slight misalignment on the numbering than damage my chucks and so forth by hammering on work items in them.
Result of some stamping on the table itself:
The two 3's on the 330 looks badly formed, but they are OK; I forgot to rub a dirty finger over them to fill up the recesses to improve contrast, and the lighting is playing havoc.
Some more of the numbering:
By no means perfect, but it will have to do for now.
(Heck, back then it was adequate, and it still is :ddb: )
:beer: , Arnold
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