Re: [ATM] Help me get back to sphere

["Jonathan Bishop" <jonathan_bishop@sbcglobal.net>]

Hi Ken,

Many others have more experience on this than me, but here are my thoughts
anyway...

You should be able to get back to a sphere by using short TOT center over
center strokes - provided the lap is hard enough. I suspect that with the
warmer weather many of us newbies (including myself) are experiencing
problems with soft pitch laps.

So my advice is to make sure your pitch is not too soft. Maybe try Gugolz
73, or boil the pitch you have for an hour or two (outdoors on electric
pad). Then give it a try. I have not made a Twyman tester (I don't want to
get that sceintific, yet), but did make sure to get a thermometer so I knew
exactly what temperature my garage was. What works for me is to avoid
temperatures much above 75F, but I guess that depends on the pitch you are
using.

BTW, I was surprised at how much the temperature was varying without my
noticing it. I guess we are not very good at estimating temperatures. You
may want to control that variable at least.

Hope this helps,

Jon Bishop


----- Original Message -----
From: "Ken Reid" <ken_reid@telus.net>
To: "Guy Brandenburg" <gfbrandenburg@yahoo.com>; "Rich Ball"
<ShooterBall@hotmail.com>; "ATM List" <atm@atmlist.net>
Sent: Saturday, July 03, 2004 12:14 AM
Subject: Re: [ATM] Help me get back to sphere


>
> ----- Original Message -----
> From: "Guy Brandenburg" <gfbrandenburg@yahoo.com>
> To: "Rich Ball" <ShooterBall@hotmail.com>; "ATM List" <atm@atmlist.net>
> Sent: Thursday, July 01, 2004 7:32 PM
> Subject: Re: [ATM] Help me get back to sphere
>
>
> > I agree with others that your pitch is too soft. Get
> > it all off, and then boil it for a while and recast
> > it. Be sure that it is relatively hard, first. Then
>
> Hi All,
>
> I've been tempted to ask this question, too, for some time.  My pitch lap
> (made with a home made a Silicone II form: 3/4" squares, 5/16" channels)
has
> been trimmed once in fifty plus hours. (Gugolz 64 originally:) Only
recently
> has it warmed up above 65 F., but it has little affect on getting out of
> Hyperbola land. (my third trip) It isn't difficult to get a  descent
> Parabola either. It's just that every stroke suggested  for getting back
to
> a sphere digs deeper. Short TOT, Short MOT,  even TOT pabarolizing . I'm
> chicken to go above 1/3 for turning the edge, again. With the warmer
> temperature even chordal strokes on the 60% zone have little effect. So
I'm
> currently using TOT 1/3 and slowly cutting down the edge. It's a 10" f/6
> plate glass, by the way. 1.75" thick. I've read Follet's treatise, so I
> appreciate the edge active, historical implications of pitch lap action.
> And, I press overnight using wetted Saran wrap between tool and mirror.
>
> I've been thinking it's hard pitch. Got to be too hard. Now the thread is
> soft pitch is the culprit. This topic 'hyperbola land ' seems to be
avoided
> like the plague on the list. Only 1 good reference in the archive. So, no
> quick remedy? Simply, a long polish back with 1/3 TOT. Make a Tywann
tester
> and avoid all the experimentation? I think once people learn "the way"
they
> forget the numerous pitfalls they had to overcome, the details? Could the
> tywann tester be a bulwark against this?  Sorry for the rant, I prefer to
> shut up.
>
> Thanks
> KR
>
>
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/

_______________________________________________
ATM mailing list http://www.atmlist.net/