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Posted by on July 18, 2008, 4:16 am
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> > In article
> > <t4-dnYV9esmWO-PVnZ2dnUVZ_r3in...@posted.worldwebinternetservicesprovid=
ei
>
> >>> I'm currently fixing a number of issues on my recently acquired
> >>> Colchester
> >>> Bantam 800 lathe; one of the problems I've found is that the gear on =
the
> >>> thread dial indicator has a tooth missing. I don't think that it's
> >>> repairable as it's some form of white metal (Mazak perhaps?) so I nee=
d
> >>> to
> >>> make a new one. I've read of people using a tap as a hob for worm whe=
els
> >>> and it occurred to me that this might work for this application but I=
'm
> >>> wondering if it's going to be difficult to cut with an Acme form tap;
> >>> the
> >>> second problem would be where to get a 1 1/8" x 4 TPI Acme tap for a
> >>> reasonable price.
> >>> The gear is 16 teeth and circa 1 1/4" in diameter.
> >>> Martin
> >>> --
> >>> martin<dot here>whybrow<at here>ntlworld<dot here>com
>
> >>Those gears work okay even when badly worn or misshapen and I am not su=
re
> >>it
> >>would not work properly with a tooth missing. I have seen straight spur
> >>gears used which did not fit the leadscrew at all well. It does not tak=
e
> >>much contact to rotate the thread dial. I have not tried it but I suspe=
ct
> >>you could cut a new gear from soft material by gashing a short section =
of
> >>the leadscrew at the end and using it as a hob. Otherwise you might get
> >>any
> >>kind of 4TPI tap or bolt and use it as a hob.
>
> >>Don Young (USA)
>
> > Whilst I agree with Don, if it were me I would take the thought a step
> > further and try a repair. I would cut a slot in the gear where the miss=
ing
> > tooth isn't, so to speak, and insert (using Araldite) a sliver of brass
> > (or similar) a bit bigger than the teeth, then file it down to
> > approximately the shape of the teeth. As Don says, the power transmissi=
on
> > is negligible, and any tiny deviation in angular positioning due to
> > deviation in shape would not be noticeable in this application.
>
> > David
> > --
> > David Littlewood
>
> Thanks David, that sound favourite so far.
> Martin.
> --
> martin<dot here>whybrow<at here>ntlworld<dot here>com- Hide quoted text -
>
> - Show quoted text -
Hi If you get stuck, contact me , I can probably make you a new gear.
Peter
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> Bantam 800 lathe; one of the problems I've found is that the gear on the
> thread dial indicator has a tooth missing. I don't think that it's
> repairable as it's some form of white metal (Mazak perhaps?) so I need to
> make a new one. I've read of people using a tap as a hob for worm wheels
> and it occurred to me that this might work for this application but I'm
> wondering if it's going to be difficult to cut with an Acme form tap; the
> second problem would be where to get a 1 1/8" x 4 TPI Acme tap for a
> reasonable price.
> The gear is 16 teeth and circa 1 1/4" in diameter.
> Martin
> --
> martin<dot here>whybrow<at here>ntlworld<dot here>com
>
>