It was never a big problem Peter. I never tried it with a heavy cut though. The depth of cut would probably matter A LOT.
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Working on my South Bend 9C
- Thread starter Golem Pens
- Start date
It was never a big problem Peter. I never tried it with a heavy cut though. The depth of cut would probably matter A LOT.
Golem Pens
Michael
Late response but I've been down sick the last week. Finally had the chance to do a pass in brass as noted.
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Golem Pens
Michael
Great question. And that blank is especially hard to see detail on due to the colours. Here's a comparison with an older one. https://photos.app.goo.gl/jNStajkuferCfdWA9
Honestly, I'm not sure I'm reliably nailing the OD enough between pieces make a super accurate comparison.
Honestly, I'm not sure I'm reliably nailing the OD enough between pieces make a super accurate comparison.
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^This @Golem Pens
I saw your comparison. But like Peter, I can't judge from a photo. I'd like to know what YOU think when YOU lay an eyeball on it right up close and personal.
Maybe I missed it but how are you holding the die & how are you advancing it into the work?
I wasnt getting consistent results on fine threads and/or delicate fiddly parts using the typical methods, so ended up turning up some die heads which spin on a rod held in TS. Also I must have 5 different die diameters to contend with by now & generally most die wrenches are crap. Much better results using a die head. I can thread under power just holding the head & release, or else insert a tommy bar on bigger threads to crank. I think I can improve fine threading some more with shorter rod held in a floating reamer mechanism, next on the to-do list.
I wasnt getting consistent results on fine threads and/or delicate fiddly parts using the typical methods, so ended up turning up some die heads which spin on a rod held in TS. Also I must have 5 different die diameters to contend with by now & generally most die wrenches are crap. Much better results using a die head. I can thread under power just holding the head & release, or else insert a tommy bar on bigger threads to crank. I think I can improve fine threading some more with shorter rod held in a floating reamer mechanism, next on the to-do list.
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BaronJ
Ultra Member
Hi Michael,
To me the threads on the plastic (Black) one look flattened on one side, maybe the blank was slightly over size.
BaronJ
Ultra Member
Hi Peter,
The shaft on my tailstock is 13 mm diameter and much shorter only about 25 mm into the die holder. I also have several size die holders that fit on the same tailstock holder.
Golem Pens
Michael
A somewhat similar setup in fact.
The main piece uses an er32 collet to swap in other dies or taps in their own holders.
I've only used hand power for tapping with this.
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That aspect looks good. What got me thinking about a floating reamer holder was the potential for the die to be off relative to work center axis. Example, DOC of a 1mm pitch thread = 0.613mm = 0.024". Thats considered a relatively course thread for finicky fastener work. I know my TS is 3-4 thou high. Lets say the die/holder gap is another 0.002". Lets say the ER /holder gap is is 0.001" just for numbers. Collective off-center could be as high as (0.004 + 0.002 + 0.001) / 0.024 = 0.29 so 29% of thread depth. Thats actually quite a bit in terms of thread form. And of course left/right TS off-axis could add to that. A finer 0.8 pitch = 0.433mm = 0.017" so the same hypothetical setup off center gets even more magnified relative to pitch. Of course we hope the tolerances could align to help cancel one another out but we have no control of this.
Golem Pens
Michael
That's why earlier I was wondering if I may want to try and account for the bed wear by shimming the tailstock up a bit (I think I've got the L/R alignment in hand). Obviously that only addresses it for a given location on the bed, but I cut these threads within a pretty narrow range of distance.
Two words. "SINGLE POINT".
I've done the die in the tailstock thing and have a tailstock die holder that I have four sizes for.
Mine has a shorter length than @PeterT's does. But I can see the advantage of the long shaft which I agree might act a bit like a floating reamer holder.
Will that help? I dunno.
In general I just don't like threading with a die on the lathe. Even floating, I cannot imagine them holding a true center. The teeth in the die cannot be identical and we all know how non-homogeneous most materials are which can't help but lead the die off center. I guess that applies 10 fold to the mixed layers of @Golem Pens plastic stock.
As @PeterT 's math shows, it doesn't take much. But I really don't think it needs to be off center to screw up the screw! Other factors and forces will contrive to do it regardless.
I've done the die in the tailstock thing and have a tailstock die holder that I have four sizes for.
Mine has a shorter length than @PeterT's does. But I can see the advantage of the long shaft which I agree might act a bit like a floating reamer holder.
Will that help? I dunno.
In general I just don't like threading with a die on the lathe. Even floating, I cannot imagine them holding a true center. The teeth in the die cannot be identical and we all know how non-homogeneous most materials are which can't help but lead the die off center. I guess that applies 10 fold to the mixed layers of @Golem Pens plastic stock.
As @PeterT 's math shows, it doesn't take much. But I really don't think it needs to be off center to screw up the screw! Other factors and forces will contrive to do it regardless.
Golem Pens
Michael
@Susquatch I do promise I am not ignoring you re: single point. I am just slow moving, and very easily distracted!
What you could do if you havent already is tempoarily remove the die, put a dial test indicator in your lathe chuck & rotate about the die cup ID. If thats reading fine, say within 0.001" in both primary orientations, then odds are good the die runout should not be too far off assuming its a nice sliding fit. With DTI in, you could also tug on the sliding assembly to see if that varies.
I forgot you mentioned potential bed wear but also most lathe TS start out high (3-5 thou, all depends) so it could be they are serving to cancel one another. The DTI test will reveal whats going on. And it might not be quite that simple with bed wear depending on offset distance as you say, especially if the TS is pointing downhill but may not have actually displaced itself downhill depending on where wear occurs. Where exactly would you anticipate shimming the TS?
Quite reasonable thinks I. After all you're only trying to make a single point.
140mower
Don
That and the old man can't remember if he's already mentioned it, so, you know..... see above.... 😉
Golem Pens
Michael
Finally ordered some HSS blanks to try grinding them, eventually...
140mower
Don
It's okay Molasses, errr Michael, we know you'll get there.......
We're relentless........ Like a dog on a rancid bone... 😉
Golem Pens
Michael
Hey if you wanna watch my kids or cover my day job it would go a lot faster!