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 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

"Martin Whybrow"  wrote in message 
news:6Fvfk.16516$bt6.342@newsfe14.ams2...
> 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 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
>
>
Those gears work okay even when badly worn or misshapen and I am not sure 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 take 
much contact to rotate the thread dial. I have not tried it but I suspect 
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)

On Jul 17, 12:39 am, "Martin Whybrow" 
wrote:
 would be where to get a 1 1/8" x 4 TPI Acme tap for a
> reasonable price.

Try Tracy tools

In article 
<t4-dnYV9esmWO-PVnZ2dnUVZ_r3inZ2d@posted.worldwebinternetservicesprovidei
nc>, Don Young  writes
>
>"Martin Whybrow"  wrote in message
>news:6Fvfk.16516$bt6.342@newsfe14.ams2...
>> 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 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
>>
>>
>Those gears work okay even when badly worn or misshapen and I am not sure 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 take
>much contact to rotate the thread dial. I have not tried it but I suspect
>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 
missing 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 
transmission is negligible, and any tiny deviation in angular 
positioning due to deviation in shape would not be noticeable in this 
application.

David
-- 
David Littlewood

"1501"  wrote in message 
news:1b732537-c048-4d16-a699-7e256f1b6ebe@m44g2000hsc.googlegroups.com...
On Jul 17, 12:39 am, "Martin Whybrow" 
wrote:
 would be where to get a 1 1/8" x 4 TPI Acme tap for a
> reasonable price.

Try Tracy tools

I've already checked the website and they don't have them that large; thanks 
anyway.
Martin.
-- 
martin<dot here>whybrow<at here>ntlworld<dot here>com

"Don Young"  wrote in message 
news:t4-dnYV9esmWO-PVnZ2dnUVZ_r3inZ2d@posted.worldwebinternetservicesprovideinc...
>
> "Martin Whybrow"  wrote in message 
> news:6Fvfk.16516$bt6.342@newsfe14.ams2...
>> 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 
>> 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
>>
>>
> Those gears work okay even when badly worn or misshapen and I am not sure 
> 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 take 
> much contact to rotate the thread dial. I have not tried it but I suspect 
> 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)
Thanks Don but I don't fancy gashing the leadscrew and I can't think of a 
lashup that would enable me to use it to cut the gear anyway, the through 
bore of the headstock is too small to try getting in the lathe! I'll dig 
around for a 4 TPI tap but they are a bit thin on the ground in my workshop, 
maybe I'll find one on fleabay.
Martin.
-- 
martin<dot here>whybrow<at here>ntlworld<dot here>com

"David Littlewood"  wrote in message 
news:vWZtSsCPr1fIFwWA@dlittlewood.co.uk...
> In article 
> <t4-dnYV9esmWO-PVnZ2dnUVZ_r3inZ2d@posted.worldwebinternetservicesprovidei
> nc>, Don Young  writes
>>
>>"Martin Whybrow"  wrote in message
>>news:6Fvfk.16516$bt6.342@newsfe14.ams2...
>>> 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 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
>>>
>>>
>>Those gears work okay even when badly worn or misshapen and I am not sure 
>>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 take
>>much contact to rotate the thread dial. I have not tried it but I suspect
>>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 missing 
> 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 transmission 
> 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

On Jul 17, 6:48 pm, "Martin Whybrow" 
wrote:
> "David Littlewood"  wrote in message
>
> news:vWZtSsCPr1fIFwWA@dlittlewood.co.uk...
>
>
>
>
>
> > In article
> > <t4-dnYV9esmWO-PVnZ2dnUVZ_r3in...@posted.worldwebinternetservicesprovidei
> > nc>, Don Young  writes
>
> >>"Martin Whybrow"  wrote in message
> >>news:6Fvfk.16516$bt6.342@newsfe14.ams2...
> >>> 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 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
>
> >>Those gears work okay even when badly worn or misshapen and I am not sure
> >>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 take
> >>much contact to rotate the thread dial. I have not tried it but I suspect
> >>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 missing
> > 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 transmission
> > 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