Re: [ATM] hogging out...break out question

[Peter De Baan <pdebaan@hotmail.com>]

I am just thinking aloud,
I also have done a few hoggings with full tool size, and more with sub diameter tool.
With full size tool we hog with MOT, wearing down the center of the mirror and the 
edge of the tool, when using subdiameter tool I have always used once less than 
40% and some only 5% such as a cast iron pipe flange and that always with TOT 
an no overhanging strokes for you don't want to wear the edge of the mirror, and 
when you use a ring kind of tool as a 4" diamond or a 2" pipe cape you wil wear the 
mirror center very nice, but a larger ring will have to move over the edge in order 
to wear the center.
So if you have some old used tools like a 10" and work that with MOT you will wear 
the center of the mirror before you match curvature, exectly what you want, but I
would not start with an flat tool on or under a new flat mirror blanc,
my 2 cents 
Peter   
  
 > From: princenorman@bellsouth.net> To: atm@atmlist.net> Date: Mon, 10 Dec 2007 19:05:58 -0500> Subject: Re: [ATM] hogging out...break out question> > Side question here....> > Lots of texts and people advocate the use of subdiameter tools/laps...yet > the descriptions of "stroke" are still defined by 1/n "diameter"...in such > instances is this the diameter of the tool or of the mirror?...the > average?...and if it is of the mirror...MoT...am i to assume that a 1/3 > stroke of a 13" mirror on a 10" tool has an average overhang of 2.166" at > either end of the stroke?(relative to edge)...or is it 3.666" do to the 3" > of tool that is not there?(that would be relative to center rather than edge > i guess)...And how does the overhang change given the same terms for ToT > operations...?> > sorry may seem obvious to others, but have never seen anyone make any > comment on this(in books or on the web). I am very curious on this point.> > Norm Prince> > ----- Original Message ----- > From: "Mike Lockwood" <melockwo@uiuc.edu>> To: "'ATMList'" <atm@atmlist.net>> Sent: Monday, December 10, 2007 13:10 PM> Subject: Re: [ATM] hogging out> > > > Frans,> >> > Frans Franssen wrote:> >> After having made several mirrors with blanks and tools of equal size I > >> am> >> now for the first time going to hog out a 13" mirror with a 10" plate > >> glass> >> tool. Which stroke should I apply to get the right depth? Should I move > >> the> >> tool COC with the center of the tool reaching the edge of the mirror with> >> each forward and backward stroke? I will start with carbo # 60. Thank > >> you> >> for your advice.> >> > I'm guessing that if you can keep the 10" tool from rocking and moving> > around, a combination of the traditional chordal stroke (mirror on> > top, carefully) and some tool on top, center over center work with 1/3> > D strokes should do a decent job.> >> > The plate glass tool is going to wear faster than the mirror (which I> > assume is Pyrex?), because it is softer and smaller, so you will have> > to determine when it is time to switch from chordal to TOT.> >> > Keep the tool beveled! It is going to wear faster, so the bevel will> > wear away faster, too.> >> > When you do TOT, don't be afraid to stack some weight on the back of> > the tool. Carbo likes pressure.> >> > If you have a turntable there are faster ways.> >> > Mike Lockwood> >> >> > _______________________________________________> > ATM mailing list http://www.atmlist.net/> > > > > _______________________________________________> ATM mailing list http://www.atmlist.net/
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