# Reverse Engineered



## Alexander (Jun 16, 2015)

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.


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## Alexander (Jun 16, 2015)

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.


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## Janger (Jun 16, 2015)

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


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## Alexander (Jun 16, 2015)

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.


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## Alexander (Jun 27, 2015)

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?


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## Janger (Jun 27, 2015)

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 ...


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## BradH (Jun 28, 2015)

Alexander said:


> 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


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## Jwest7788 (Jun 28, 2015)

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!


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## Alexander (Jun 28, 2015)

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.


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## Jwest7788 (Jun 29, 2015)

Alexander said:


> 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?


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## BradH (Jun 29, 2015)

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


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## Jwest7788 (Jun 29, 2015)

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

JW


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## Rick Runciman (Jul 4, 2015)

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.


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## Alexander (Jul 4, 2015)

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.


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## Rick Runciman (Jul 4, 2015)

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?


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## Alexander (Jul 5, 2015)

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.


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## Rick Runciman (Jul 5, 2015)

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.


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## Alexander (Jul 6, 2015)

Thanks that makes sense. The more you know the further you go.


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## Rick Runciman (Jul 6, 2015)

Always do the threaded end last, if you can.


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## Krprice84 (Oct 8, 2015)

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?


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## Alexander (Oct 9, 2015)

You are probably not wrong. My basic understanding of metallurgy led me to think that if you get a piece of HSS hot enought that you change the colour that is because you have taken that piece past its critical temperature and the oxygen has left the discoloured look. Doesn't sound like the ideal situation to me. What does everyone else think? Non ferrous metals go brown or blue when the oxygen oxidizes the surface which only happens above the temperature when the metal starts to change. Am I right?


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## PeterT (Oct 9, 2015)

apparentlyI'm no expert either but have been lurking on some heat treating sites as I'm machining O1 tool steel parts that require hardening. My take: assuming proper quenching of typical high carbon tool steels, they have a predictable color change during tempering. Each color occurs at a certain temp during elevation & has a corresponding hardness level when stopped there. So if you were to heat these steel blanks from straw yellow (450F) to blue (575F) you would reduce hardness from about 61 to 55 Rockwell according to the chart. http://www.threeplanes.net/toolsteel.html

But I think modern, premade HSS tool blanks is a different animal with other metallurgy goodies to increase strength, toughness & maintain hardness over elevated temperatures. The graph is  kind of generic but shows plain carbon steel to HSS & cobalt alloy for example. Tool steel is probably somewhere in between. But notice that's Temp vs. Hardness. What I've always wondered is if HSS has the same color spectrum as carbon steel but 'displaced' at say 100F higher temp? Haven't seen a chart like that. But I remember being told  by Mr. Shop Teacher "don't let your cutter edge turn blue" when grinding, hence the frequent water dip. So whatever temp that equates to means less hard. Now if you are grinding tool steel profile (prior to heat treating) then who cares what color, once profiled you are going to take it up to carrot red anyway for quenching/hardening, but that's a completely different operation.

Another guy told me its confusing because older generation cutters (and therefore text books) were more like modern high oil/water/hardening 'tool' steels. So as the chart shows they would see a more dramatic degradation of hardness with color show. Whereas about the only thing you can do to shape commercial HSS tool blank to best of my knowledge is grind it. Enough theory - lets make something!


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## Krprice84 (Oct 9, 2015)

Yea, my understanding (basic as it is) is that modern hss and cobalt alloys are designed for high hot wear resistance. They still will get tempered at high temps, but the color isn't representative of the actual tempering in the same way that it is for other steels.

This is, of course, just my understanding, but that's how it was explained to me a few times, plus on a few YouTube videos.

One guy said that you used to have to quench, but that now it's primarily for comfort holding the tool. You still don't want to get it crazy hot, but he said that you generally don't come near hot enough unless really grinding tons of steel off a tool. Dunno though..... I'll probably quench anyways just to be certain


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## EricB (Oct 12, 2015)

I was going to mention the same ideas as @Rick Runciman I do nothing but threads at work, and I use aluminum shims a lot. The other thing you could look at is making yourself a set of soft-jaws for your chuck, but as Rick said, I would probably just machine the other side first. What kind of jack are you working on, is it an old Walker or something?


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## Alexander (Oct 12, 2015)

It is a hillman toe jack. Fancy and expensive  unfortunately   they don't sell the part I need so I'll make some.


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## PeterT (Oct 23, 2015)

some additional info I stumbled on re what heat colors imply to grinding HSS tool bits (starts about 13:40)


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## Johnwa (Nov 4, 2015)

Krprice84 said:


> 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.
> 
> ...



You're right.


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## PeterT (Dec 15, 2015)

Finally found a link with some good down to earth temperature specs
http://www.gadgetbuilder.com/VerticalShearBit.html

*About HSS* _In "Design and Use of Cutting Tools" Leo St. Clair had some interesting observations on HSS and how to select among the various grades. The basic M1/T1 grade of HSS (without cobalt) is the strongest and toughest material but begins to lose hardness above 750F and should not be used above 1000F. Adding 8% cobalt improves hardness at cutting point temperatures to 1100F but reduces strength and toughness. Adding more cobalt (12%) extends the temperature range to about 1150F but further reduces strength and hardness. The cast alloys (T15, Tantung, Motung, Rex76, Rex95, etc.) handle 1200F or more but are somewhat brittle and their cold hardness is less than some regular HSS._


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