Here is a list of all the postings MyrtleLake has made in our forums. Click on a thread name to jump to the thread.
|Thread: Poor Hex stock|
In my experience, all standard (i.e. not precision ground) hex stock has rounding of the points. That is to be expected. How much rounding can vary, but the overall effect should be a nice, deburred corner. Something that drastically changes the overall hex profile is unacceptable.
I might also add this. All the hex stock I've encountered has a uniform rounding of the points. Your description implies a fairly dramatic variation. That, I would find very odd and could be grounds for refusal. Definitely worth a point of inquiry, IMO.
Edited By MyrtleLake on 24/04/2016 21:12:41
|Thread: Ceriani David lathe: change gears|
There is no agent in the USA. I got a quote from Ceriani a while ago. The shipping costs were significant but within reason.
Here is the context driving my interest in the matter. It may be helpful to the discussion to mention it.
My workshop functions around Schaublin W20. There are two 102 lathes which use W20 collets and chucks (M37.6 x 3 spindle thread). My milling machine also uses W20 collets, and its accessories accept W20 collets and lathe chucks. The Ceriani is the only lathe I know of that is available with this spindle option. Even if I found a Schaublin 102-VM or 102N-VM, getting it into my basement shop is not in my future.
One of my 102's is set up for thread cutting. It uses a watchmakers' type telescoping shaft to drive the top slide. There are a few issues that are less than ideal. The longest thread I can cut is 70 mm without having to move the compound slide and pick up the thread again. The cutting tool advancement is only able to be advanced straight in (90 degrees) to the work.
The final issue that an engine lathe such as the Ceriani would alleviate is longer turning operations. Anything longer than 150 mm requires the compound to be moved laterally along the bed. Then the cut must be accurately picked up at the same diameter. Here is an example: a drawbar I made.
Hence, the main focus for another lathe in my shop is turning and screw cutting longer diameter work. To a lesser extent, it would also allow faster, simpler threading operations. When feeding a cutting tool directly in during threading operations is problematic, an engine lathe would be a useful option.
While most of my work is metric --- as is my preference -- it seems inch threads are required often enough to warrant the attention to accuracy. To a far lesser point, I also like that the Ceriani is truly metric on its cross slide, top slide and tailstock screws. I am in North America, and finding a native metric hobby lathe is very limiting. (Yes, a DRO is an option here)
Having a lathe that is native W20 would mean work could be transferred in one chucking between lathe/lathe or lathe/mill. Being able to use my existing array of collets and lathe chucks is practical too.
Those are the draws that keep bringing me back to considering the Ceriani David. I've always found myself, though, a little underwhelmed by its draw. I don't know what to say beyond that.
Edited By MyrtleLake on 12/04/2016 21:05:34
Okay, I follow your math now, at least. You're calculating (60/65) x (75/30). You expressed this in an earlier post as "0.923 and 2.5." I believed I understood compound gear train calculations, but you've proven me ignorant. Having just skimmed Screwcutting in the Lathe by Cleeve and Machine Tool Operation by Burghart for review, I'm clearly lost.
Some quality time with the books are needed for me on this one.
JasonB - thank you for working those out for the various pitches. I was reading the drawing the same, but it seemed really very odd to me. 65 / 75 is a poor translation ratio to use, I would think.
I don't find much discussion of these lathes online. That said, they are a consistent advertiser in MEW, so possibly some members here own one.
I have looked through the manual of the David 203 manual. It can be found on the Ceriani website: www.cerianimu.com I still cannot determine what exact gear selection is utilized for metric to inch transposition. it is obvious (it seems to me) that there is not a 127 tooth gear, so it must be a close approximation. Does anyone know which it is?
Edited By MyrtleLake on 11/04/2016 20:28:42
|Thread: Gear hobber (mechanical)|
The Sherline rotary table...
400 steps per handle revolution. Worm and gear makes 72 turns for one full rotation of the table. So 28,800 steps per 360 degrees. That equates to 80 steps per degree, which in turn equates to 0.75 minutes per step. Final controller, electronic position is accurate to +/- 0.5 step.
"This turns out to be a very small amount because the sine of this angle is only 0.0001091. This will amount to 0.109 mm per 1 meter when compared to a flat plane. This is just 0.0055 mm at the edge of the table"
Good enough for me!
127 tooth, 1 MOD.
The mechanical hobbing machine looks fun. I agree, though---won't you then have to make the hobs? So that leads you into making the Eureka relieving tool. How far do you want to take this?
Edited By MyrtleLake on 22/02/2016 17:37:03
|Thread: Tool ID|
It is a sine bar, which is used for very precisely setting angles.
|Thread: Boring Bars.|
I am aware of at least one manufacturer that makes the following distinction on the set screw issue. The http://www.ultradexusa.com catalog offers, "Use the right set screw! Flat point, not cup point!"
Personally, I use a QCTP in a few ways to hold my boring bars. 1) A collet tool holder 1/2" shank and under. 2) A split sleeve in a bored tool holder. 1" shank and under. 3) A standard tool holder with a vee on the bottom slot. 3/8" shank and under.
Edited By MyrtleLake on 24/01/2016 21:58:30
|Thread: Milling HSS|
I've done it with a solid, micrograin carbide end mill with TiAlN coating. SFM is way up there. The exact figure escapes me at the moment. Feed should be lightning fast by hand. This is limited, though, by the rigidity of the set-up. Increase feed until surface finish goes way down. I was using 0.20 mm DOC. The chips are a fine, fuzzy dust.
I was making a small slotting tool and wanted the angle to be accurate while retaining the clearance and back rake angles. In such a small tool, this would have been a challenge by hand. After milling, the facets were finished with a fine India stone.
The tool started as a larger diameter HSS, round bit. M2. I would be more skeptical of trying this on one of the tougher HSS grades (cobalt alloy, T-15, etc.). The shank was turned down initially using a ceramic insert. This left a larger diameter portion on the end. That was then milled into the shape shown.
Edited By MyrtleLake on 22/01/2016 16:11:30
Edited By MyrtleLake on 22/01/2016 16:12:47
Edited By MyrtleLake on 22/01/2016 16:13:31
|Thread: Cutting Internal threads|
Ifanger (Swiss). It's a helix of the correct threading profile. There was (is?) an American company with an equivalent design, but I cannot remember the trade name.
Edited By JasonB on 16/12/2015 18:11:43
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