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25.4_mechanic
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Screwdriver
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Page 28 and page 41 explain how you can cut a metric thread on an imperial lathe, disengage the half nut, reset the saddle manually, using the TDI?
Do tell. It appears to be impossible.
500e
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Melvyn Best
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Isn’t that what finger files are for??What's wrong with a bit of sandpaper glued to the back of a hold brush?
Olderisbetter
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Spotted a tin of old nuts and bolts outside a house for scrap, it would have been rude not to take them away.
DAPPH
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Page 28 and page 41 explain how you can cut a metric thread on an imperial lathe, disengage the half nut, reset the saddle manually, using the TDI?
Do tell. It appears to be impossible.
ATLAS, CRAFTSMAN, COMPANION, DUNLAP & AA
Discuss any issues dealing with Atlas & Atlas-Clausing lathes, drill presses, mills, etc. in this forum.
www.hobby-machinist.com
You do have the basics but seem to have over complicated things by your thinking .
Set the gears to the correct metric thread feed .
Using a clamp on saddle stop at the chuck end to always bring the unclamped saddle back to the same position by rotating the lathe backwards by hand will always bring the TDI back to a ready to start point every time ... note the TDI position or
put a spot of your pink nail varnish on it to read to the start point .Run the thread off the RH end of the stock . Disengage the half nuts sharpish , stop the lathe , back off the cross slide & cutter to clear the major thread thread by a few thou , hand wind pullies back wards so the saddle is fully to the left on to the stop . Check the TDI is in the right position adjust if needed , advance the cutter in a few thou , engage the half nut fully , start the lathe .
As the lathe is in slow rpm there is no conflict about taking off a few thou on start up .
If you undercut the left hand end thread max diameter by the thread depth plus say 4 thou it will give you an under cut space space to get your tool in without having a tear out of metal .
DAPPH
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In that MOLO it's page 119 , thanks for putting it up.
That's a seriously good box of useful bits - totally envious
anto44
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The person who threw that box out is going to need one of those bolts next week
Screwdriver
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These guys have a member who lives & breathes Atlas/ craftsman lathes .. he has taken a lot of time to develop the craftsman lathe section join and all will be revealedATLAS, CRAFTSMAN, COMPANION, DUNLAP & AA
Discuss any issues dealing with Atlas & Atlas-Clausing lathes, drill presses, mills, etc. in this forum.
You do have the basics but seem to have over complicated things by your thinking .
Set the gears to the correct metric thread feed .
Using a clamp on saddle stop at the chuck end to always bring the unclamped saddle back to the same position by rotating the lathe backwards by hand will always bring the TDI back to a ready to start point every time ... note the TDI position or
Run the thread off the RH end of the stock . Disengage the half nuts sharpish , stop the lathe , back off the cross slide & cutter to clear the major thread thread by a few thou , hand wind pullies back wards so the saddle is fully to the left on to the stop . Check the TDI is in the right position adjust if needed , advance the cutter in a few thou , engage the half nut fully , start the lathe .
As the lathe is in slow rpm there is no conflict about taking off a few thou on start up .
If you undercut the left hand end thread max diameter by the thread depth plus say 4 thou it will give you an under cut space space to get your tool in without having a tear out of metal .
Been a member there for years, the link just takes me to the forum section, not a specific thread.
Using a bed stop will not work. Period. If you disconnect the half nut, the saddle is no longer correctly phased with the lead screw. I am not overthinking this or over complicating it. Looking at the basic fact of the matter, if you wind the saddle back to a stop, it will not return to the same phase relationship to the lead screw unless it happens to be an even multiple of 127 turns of the TDI away from where it stopped.
slim_boy_fat
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Olderisbetter
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DAPPH
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Yes you are right , I made a mucking fuddle in the neck top computer department whilst trying to type it out , leave the half nuts connected and wind the saddle back to the stop then check the TDI alignment .
You can always ask the guys on the welding site for worked knowledge rather than trawl through thousands of posts looking for things , they've been very helpful to me over the years .
Screwdriver
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Uh sure thanks but you're doubling down here. The bed stop will do nothing to help in the situation you describe, neither will the TDI.
You cannot "wind back" the saddle with the half nut engaged (try that and get back to me).
You can drive the lathe backwards with the half nut still engaged but two things happen:
1. When it hits the bed stop, the TDI is at a seemingly random orientation unless it has done a full 127 turns (on your ten foot seven inch long bed)
2. Under power, unless you stop the lathe perfectly, either the half nut drops out when it bangs into the saddle stop or something breaks.
There is one working technique for metric threads on an imperial lathe which allows you to disengage the half nut safely. You might want to do this when threading up to a shoulder, close to the chuck or if you are cutting at high speed and everything is a bit urgent.
Engage the half nut as usual to start the threading at a known point on the TDI.
Cut the thread into the relief, disengage the half nut and immediately stop the lathe.
Do not manually wind the saddle(!)
Power the lathe backwards and as the TDI starts turning backwards, re-engage the half nut at the mark. Note because you stopped the lathe very quickly after disengaging the half nut, the TDI has only moved a small amount past its mark. The half nut is of course in the exact same phase as if you hadn't disengaged it SO LONG AS YOU DON"T MOVE THE SADDLE MANUALLY WHILE IT IS DISENGAGED.
If the saddle moves at all while not connected via the half nut, the relationship of its position wrt the thread is lost.
<edit> I feel your pain getting befuddled when trying to describe what's happening. Intuitively it is clear the phase relationship is lost due to the odd gearing ratio (@Seadog has described why with the "hunting" gear scenario) but trying to explain in words is a bit of a head bender. It's fun though...
8ob
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The_Yellow_Ardvark
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