[logan944t]

New guy need some basic info and to ask some stupid questions.

I found this site during a search for info on bearings. I am a refugee from the lapidary skills camp ( I carve rock into fun figures) and want to get into gem cutting. After seeing what the basic faceting machine (new) was costing I checked ebay and was a bit crestfallen when I realized the prices on a used ( needs to be refurbished) faceting machine was still upwards of 600$.

Unfortunately I have a penchant for making what I need -- and the quest began. I decided I need to make a lapping machine first.

A lapping machine is basicly a variable speed horizontal sander/grinder,that has a runout of .001 at the edge of a 4" platen. How hard could that be, right? I ordered (2) shielded single row ball bearings 1/2". After recieving them ( and having no dial indicator) I put a 12" section of threaded rod thru the bores and clamped them together -- trying to wiggle the rod. It moved. Even to my eye I could see it moved about too much-- and it was the bearings --not the rod.

First question --- what kind of bearings will have little to no play radially? Highest speed would be less than 2k and theres not much load when lapping -- but the bearings have to be tight.

Heres what I want to do -- I have my eye on a 7x12 mini lathe ( waiting for a "sale" day) with which I want to turn a spindle ( aluminum 6061 1 5/8" -- I have it laying around) and a platen ( 4" x 1" or so) and attach them ( recessed and screws) to each other with a 1/2 " threaded section sticking up from the spindle thru the platen to attach the master lap to.

2nd question -- are these mini lathes capable of these kind of tolerances ( never mind the operator right now) and what pitfalls am I in for.

#3rd question -- I've read several threads on spindles that are in the range of 1k. JUST the spindle. Is this because they spin at 20k?


4th question -- am I out in left field with this project -- technically? I have no metal turning skills -- altho I have extensive experince with wood turning ( I was a patternmaker in the navy in another life) and woodworking. I don't think any of the turning experience would translate -- except when to duck.

I appreciate any responses and critiques -- I'm here to learn.

[ToyMaker]

1. Almost any kind of bearing from skate board bearings
to car wheel bearing will have better (much better) than
0.001 runout. Some will need preloading.

2. Yes, the 7x mini-lathes can hold .001 tolerances.

3. ?

4. The best way to learn metal turning skills is to read,
read, and read. Then practice, practice, and practice.
Like other manual skills hands-on is the only way to become
proficient. How fast this happens depends on lots of things
including your motor skills and determination.




robotic regards,

Tom
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