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Machining a 3/4" 16TPI to 1 1/4" 8TPI Adaptor
#1
Project Name: Lathe to chuck adaptor
Budget: 100ish$ 
Time frame: No specific time constraint, soon if possible
Relevant Shops: Metal Shop
Do you have design files (illustrator files, solidworks, etc) ready to go?: I have an adaptor that could be copied for most of the dimensions that I can provide to you
Will you be providing your own materials or will you need materials provided for you: I might have the materials
Project Description and Other Comments:


I'm looking for someone to machine an adaptor for my chuck to fit onto my wood lathe. I'm not the most technical so please forgive any terminology errors. The spindle of my lathe has a 16 3/4 thread, and the chuck is supposed to have a 1 1/4" 8TPI. I bought an adaptor off of amazon that was "designed to fit any supernova chuck set" it fit the lathe perfectly but didn't fit the chuck. I reached out to the manufacturer and bought the adaptor that their technician recommended but that didn't fit either, it was the same model number as the one off amazon. So I'd much rather pay an inmate than keep throwing my money away to amazon. I measured the adaptor I bought and its around 1 1/2" thick so I figured it might be possible to just turn it down to 1 1/4" if I provided that as the materials. If not and it would be easier the start fresh I'm happy to pay for the materials instead. If anyone is interested please send me a quote, thanks!
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#2
Not sure I'd be interested, but a few comments / questions

1. Our Logan lathe has the ability to cut both 8 and 16TPI RIGHT HAND threads, (unfortunately it is not able to do metric sizes) I'm not sure if it can do left hand threads....

2. Are the needed threads normal 60* type as you would find on typical nuts and bolts, or are they 'Acme' or other less common shape (Acme threads are often found on vices or as drive screws on lathes and mills, they have an almost square shape instead of the triangular threads on bolts) Acme and other non-standard threads need specialized (expensive) tooling to cut.

3. Internal or external threads? Possibly post a rough sketch w/ dimensions - a PDF of a CAD drawing would be nice but is not essential - a paint program would do it....

4. IF external threads are needed, and the existing adapter is big enough to allow shaving the existing threads off and cutting new ones that would probably be easiest...

5. What is the material of the existing adapter? Note that hardened / tool steels are problematic, regular steels are pretty easy to deal with.

ART
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#3
(10-15-2020, 11:40 PM)ART Wrote: Not sure I'd be interested, but a few comments / questions

1. Our Logan lathe has the ability to cut both 8 and 16TPI RIGHT HAND threads, (unfortunately it is not able to do metric sizes) I'm not sure if it can do left hand threads.... 

2. Are the needed threads normal 60* type as you would find on typical nuts and bolts, or are they 'Acme' or other less common shape (Acme threads are often found on vices or as drive screws on lathes and mills, they have an almost square shape instead of the triangular threads on bolts)  Acme and other non-standard threads need specialized (expensive) tooling to cut. I believe the threads are normal, not Acme, they don't have a square shape to them. I attached a picture of the adaptor to this reply.

3. Internal or external threads?  Possibly post a rough sketch w/ dimensions - a PDF of a CAD drawing would be nice but is not essential - a paint program would do it.... The existing 3/4" 16 TPI threads are internal and the 1 1/4 8 TPI that would need to be cut are external. 

4. IF external threads are needed, and the existing adapter is big enough to allow shaving the existing threads off and cutting new ones that would probably be easiest... I rough measured the existing adaptor at 1 1/2" diameter at the peak of the threads and the entire adaptor is roughly 1 5/16" long. Does that leave enough "meat" to shave down? 

5. What is the material of the existing adapter?  Note that hardened / tool steels are problematic, regular steels are pretty easy to deal with. I'm not sure of the metal of the adaptor but it is probably a high speed/ tool steel.

ART

Hi Art,

Thanks for replying, please see my answers above in red. I Don't have a cad file of the adaptor and cant add any other pictures because of file size but if you are still maybe interested I could email you more pictures and details.


Attached Files Thumbnail(s)
   
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#4
Looking at the photo, it does appear to be a standard thread, but I am a bit concerned about whether you have the thread size right?

According to this thread size chart thread chart

There is no such thing as a 1.25-8 size thread - the standard sizes are 1.25-7 and 1.25-12.  Obviously it is possible to make any size one wants given the right tooling, but it is seriously strange to do so....

(I note in your original post you say
Quote:"the chuck is supposed to have a 1 1/4" 8TPI."
(emphasis added))


I would strongly suggest taking the chuck to a decent hardware store and verifying the thread size by finding a bolt that will screw into it where the adapter goes.... 

Where was the chuck manufactured?  If it wasn't made in the US, it is VERY likely to be a metric thread not an inch thread...  I did a little checking on Duck-Duck, and it looks an awful lot like a non-US company, if only because there is no mention of "Made in the USA" which most US companies make a big deal about...  The about us for Teknatool, which appears to be the parent company, says they are a NZ corporation w/ Manufacturing in China, and only distribution in the US - which almost certainly means metric...  Also their specs tend to be formatted with even metric sizes first, with inch sizes in parentheses - again this usually indicates metric sizing.....

With all of that, I'd suggest that it is very likely to be METRIC - probably an M30-3.5 or an M33-3.5, (metric coarse) since those are the two most common metric sizes close to 1.25"...  It is possible that they could be a metric fine thread, M30-2 or M33-2, or at least that is what my thread reference charts suggest...  (I'm attaching one that I use often as it covers about every thread there is in it's range. Note that most metric threads are "metric coarse" unless specified otherwise, and US threads will be UNF or UNC, the other sizes listed are really odd, and mostly only seen on special applications usually OLD stuff...)


.pdf   thread-size-data-inc-odd-sizes.pdf (Size: 222.42 KB / Downloads: 0)

ART
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