• Spring 2024 meetup in Calgary - tentative date Saturday, April 20/2024. Other regions are also discussing meet ups. If you want one in your area get going on organizing it! discussion
  • We are having email/registration problems again. Diagnosis is underway. New users sorry if you are having trouble getting registered. We are exploring different options to get registered. Contact the forum via another member or on facebook if you're stuck. Update -> we think it is fixed. Let us know if not.
  • Spring meet up in Ontario, April 6/2024. NEW LOCATION See Post #31 Discussion NEW LOCATION

Reverse Engineered

Alexander

Ultra Member
Administrator
Hey everyone. I'm starting a thread so you can follow my little adjusting screw project. I am turning this at home in my garage on the CNC lathe. I only have one side programmed so far but I will update this post later to include the other side plus a link to a video so I can fully explain the tooling I used. I've added a photo with the old screw that is black and my new one will be yellow brass.
 

Attachments

  • image.jpg
    image.jpg
    871.8 KB · Views: 28

Alexander

Ultra Member
Administrator
I have posted a video explaining all the tooling I have used for this project and the turning center I am using. It also gives a basic intro to 2 axis cnc.
 

Janger

(John)
Administrator
Vendor
Alexander, thanks for posting this, it was very interesting. So how many passes and long to complete the threading?
 

Alexander

Ultra Member
Administrator
I believe straight depth was .062 because it was 10 tpi unc. I set the threading cycle to advance the tool .0005 per pas so 124 passes were made and it took about 5 min to complete. Finish was nice! And the thread fits great.
 

Alexander

Ultra Member
Administrator
Well that's a little disappointing. I thought I could protect the treads with some paper and machine the other side just holding onto the thread. The thread is too soft. Brass really likes to grab when you machine it. So this isn't going to work both times the part came out of the Chuck at 1000rpm+. I would love to thread this part into a custom fixture for machining but is is a ridiculous proprietary thread design. .7 od and 10tpi. Any ideas?
 

Attachments

  • IMG_20150627_105139897.jpg
    IMG_20150627_105139897.jpg
    1.9 MB · Views: 19
Last edited:

Janger

(John)
Administrator
Vendor
So why would turning both ends at once then parting it off not work? I don't follow the problem there ...
I mean completing the whole part in one go, threaded end on the right and the other part on the left in the lathe ...
 
Last edited:

BradH

Member
Well that's a little disappointing. I thought I could protect the treads with some paper and machine the other side just holding onto the thread. The thread is too soft. Brass really likes to grab when you machine it. So this isn't going to work both times the part came out of the Chuck at 1000rpm+. I would love to thread this part into a custom fixture for machining but is is a ridiculous proprietary thread design. .7 od and 10tpi. Any ideas?
Very interesting video.

So: thread is 0.7"? Maybe 11/16X10. Did a quick search and there is a British thread that size and pitch... Would be close to 18mm also. Does seem to be an odd size.

For chucking; a collet chuck would hold it more firmly. You could probably buy a small ER collet set on Ebay for cheap. Depending on the MT on the head stock you might get an ER holder to go in, which would give you pretty reasonable repeatability.

I didn't see external threads on the back side, so what if you turned that side first, and then chucked it and turned the threaded portion?

Brad
 

Jwest7788

Joshua West
Administrator
For chucking, why don't you just machine a coupling nut with the correct thread you need to thread the part into the nut?

The chuck the nut. When working the piece, it will just help to tighten the connection into the nut.

Take advantage of the thread!
 
Last edited:

Alexander

Ultra Member
Administrator
Yeah @Jwest7788 that is certainly the best way. It is a custom thread profile and I don't have a internal threading bar. That is what I should probably go get. If it was an easy size I would have drilled and tapped a custom fixture for this piece already. Alternatively I could make the whole thing in one shot but the saddle on this machine is super wide. That really helps with rigidity. That also means if you want to use a center the quill is way too short. In the future I will make a custom extra long quill or a custom long center.
 

Jwest7788

Joshua West
Administrator
I don't have a internal threading bar. That is what I should probably go get.

I've done all of my internal threading with a ground piece of HSS (on my manual machine), would that work for you in the short term?

Alternatively, what does this piece screw into when complete? Would it be able to be safely chucked?
 

BradH

Member
I tried - curious now - looking up the BSW thread dimensions; the charts I found only have 11 TPI for 11/16 diameter...

I guess if you can cut the thread on your CNC maybe make a tap from a piece of drill rod?

Having said that... I can't find the page just now but that sparks another memory: there was a guy who made internal threading tools with drill rod. Basically turn a 60° profile on the end of the bar in the lathe. Undercut on the rod behind the profile deeper than the thread depth and longer than the depth you intend to thread into, then mill half of the profile away (though I would be tempted to leave 75% of it - future sharpening / wear. The rod could then be hardened and tempered, honed and used to cut the threads. Grind in top rake as required.

You could use the shank of an old (or not) HSS drill and make a threading tool. With the CNC should be easy to sort the internal thread.

B.
A link to the same concept found: http://madmodder.net/index.php/topic,8900.msg98817.html#msg98817
 

Jwest7788

Joshua West
Administrator
Don't forget the follow up video! Looking forward to seeing how you go about the other side.

JW
 
That is a sweet little cnc. Is it a conversion? Just curious,, I got away from cnc 8 years ago, old school for this old machinist.
 

Alexander

Ultra Member
Administrator
No it is porpouse built cnc. Comes setup with double nut ball screws and servos installed. Modern tool finished off the setup with a computer, drivers and a VFD for the spindle. A total pleasure to run, quality is a touch iffy but I got what I paid for.
 
Nice. Didn't know Modern did that. I love their cnc's. Cheap, run them to the gate for 5 years, toss it and get a new one. That Fagor 8055T is one sweet conversational system. My garage shop is old school only. Have some Craftex from Busy Bee, not bad machines. Are you going to use it for a small parts business?
 

Alexander

Ultra Member
Administrator
I would definitely take on jobs if they were worth my time. I don't currently have any plans to quit my day job though.
 
Not a good idea to quit your day job. Btw. to chuck threads, a small aluminum chucking ring is the ticket, with a little hacksaw slit lengthwise. just a small tube with id about .005 bigger than your thd. major od.
 

Krprice84

New Member
Just a comment on grinding tools.

My understanding was that high speed steel doesn't temper or anneal at all below a really quite high temp. I can't say for sure cuz I'm pretty inexperienced, but if it's anything like some other tool steels I've played with, you really need it to glow before you get any annealing or tempering.

I figured the quenching was just to make it so you can hold it.

Am I wrong here?
 
Top