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[4]

PM-1236-T -- threading at 90 RPM?

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Meta Key

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#1
Hi Everyone!

Newbie to the forum although not new to metal cutting.

I'm looking for a new lathe and my search led me to Precision Matthews and then to this forum.

Initially I was looking for something like the PM-1127 or PM-1228 as those sizes would be fine for my projects. But, then I discovered that the "Ultra Precision" machines were made in Taiwan and that has changed my thinking. So, now I'm contemplating the PM-1236-T machine.

But, I'm freaking out over the lowest spindle speed being 90 RPM. I do single point threading from time to time and also some boring and 90 RPM just seems crazy fast for such operations. So, my questions for anyone using either of the Ultra Precision machines are have you cut threads to a shoulder? If so, are you still alive to tell the tale?

Secondary question -- what speed does the stock motor turn at? 1800? 3600?

I see that some of you have converted to 3-phase using a VFD and I think that's great but I'm not really looking for a project but, rather, a lathe I can use after cleaning and setting up. Also, the PM-1236-T with stand and shipping puts me right at the top of my budget so another $500~ish for a 3-phase conversion isn't terribly appealing -- at least not right now.. (Got all the other tooling I need from prior lathes.)

Thank you and best regards,
Meta Key
 

jbolt

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#2
While the lowest speed on my lathe is 50 rpm I generally bore at the same speed as turning for the given diameter. For single point threading I run 100 to 200 rpm depending on the pitch. For threading to a shoulder if I'm not comfortable with the approach speed or do not want a large relief I invert the threading tool and thread in reverse away from the shoulder.
 

markba633csi

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#3
Such is the dilemma when you don't have either backgears or a variable speed motor. I prefer both. But then I'm an old fart. (at play)
Mark
 

Ray C

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#4
I have a PM1236 -Chinese version that's about 7 years old now. It's lowest speed is 60 or 65 but I never cut that slow and usually bump it up to around 100 or more. For some things, it's perfectly fine to cut away from the shoulder using cutter made for the other side. This is how a great many folks do it.

Buy once, cry once. Consider getting the 3 phase option. I converted mine to VFD 3Phase and could never go back. I still use all the gears as usual but, it's really nice to tweak the speed 5 - 15% to fine-tune a finish. It's frosting on the cake.

Ray
 

FLguy

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#5
What jbolt said is what I do and I've been doing it for 54 years. Got every thing I was born with too.
 

pacifica

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#6
Hi Everyone!

Newbie to the forum although not new to metal cutting.

I'm looking for a new lathe and my search led me to Precision Matthews and then to this forum.

Initially I was looking for something like the PM-1127 or PM-1228 as those sizes would be fine for my projects. But, then I discovered that the "Ultra Precision" machines were made in Taiwan and that has changed my thinking. So, now I'm contemplating the PM-1236-T machine.

But, I'm freaking out over the lowest spindle speed being 90 RPM. I do single point threading from time to time and also some boring and 90 RPM just seems crazy fast for such operations. So, my questions for anyone using either of the Ultra Precision machines are have you cut threads to a shoulder? If so, are you still alive to tell the tale?

Secondary question -- what speed does the stock motor turn at? 1800? 3600?

I see that some of you have converted to 3-phase using a VFD and I think that's great but I'm not really looking for a project but, rather, a lathe I can use after cleaning and setting up. Also, the PM-1236-T with stand and shipping puts me right at the top of my budget so another $500~ish for a 3-phase conversion isn't terribly appealing -- at least not right now.. (Got all the other tooling I need from prior lathes.)

Thank you and best regards,
Meta Key
I feel more comfortable threading at 50 rpm, but I think the thread surface finsh is superior at 100 or 200 rpm.

You can make a flip-up toolholder for $35, will allow you to get close to the shoulder and use a higher rpm.

VFD($150 to $250) is best solution, but 1236 doesnt come w. 3 phase moter(another cost)
 
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