threading Invar alloy

Hello folks

I am currently making a clock and I have come to the pendulum rod which is made from invar rod.

Has anyone got any experience threading this material?

I don't particularly want to do it with a die. would much rather single point it on the lathe.

Is this even possible of the steel too gummy for that?

Some helpful notes here, Peter

http://www.invaralloy.com/invar-machining.php

MichaelG.

I'm sure I used a die on the last one I did. I think you would really want to roll the threads if you were being posh. It would be worth having a think about the geometry of the pendulum and maybe loctiting a thread onto the end. You would usually want to suspend the bob from the middle supported with an internally threaded tube screwed onto the rod. I am sure you should be able to come to an arrangement that doesn't screw the temperature compensation up.

For tapping they do suggest increasing the taping drill size as the material will swage down into the bottom of the threads and jam the tap if there is not enough clearence. (Clearence isn't quite the right word, just provide somewhere for the metal to flow into). Similar thoughts apply to dies and screw cutting too.

You will get it done but don't expect the shiny smooth threads you usually achieve on harder steels.

regards Martin

If you approach it as you would any of the austenitic stainless steels ie 304, 316 It will be fine. It will produce gummy stringy swarf and also because of the high Nickel content it will work harden in a flash. Dont let the tool "dwell " [although that shouldn't be an issue in threading ] a sharp geometry tool is good. Single pointing will be fine.

many thanks for the replies guys.

Michael, I had seen that page but couldn't find anything useful for my situation. some useful advice on tapping but not external threading.

Martin. Many thanks for your reply. I don't currently have a tailstock die holder and my attempts at producing a decent thread with dies have been a mixed bag! there seems to be no rhyme or reason as to which ones turn out fine and which ones are a horrible mess! normally I don't care, but this piece of metal is nearly £60! and I really don't want to mess it up! so I thought I may have more luck single pointing it on the lathe. although having a meter of rod sticking out the back of the headstock will be interesting..... need to find a way of supporting that!...

The bob actually isn't the problem. its temperature compensated in exactly the manner you suggest. its been sitting here on a piece of stainless rod for some time now while I work up the courage (and the money) to do the invar rod!

Raymond... sorry question from a complete thickie (the biggest problem with my model engineering exploits is that I have no clue what I am doing most of the time...) but will it turn more like silver steel or free machining stainless? (these are the 2 steels that I have turned) Will a normal carbide insert in the external threading tool be ok or do I need something fancy?

Again a huge thank you for your replies. its really appreciated.

Peter

My point regarding the loctite was to get around threading the rod at all. As far as supporting the end goes it does not have to be fancy. I had a convenient vice to use so I just arranged a piece of mdf sheet behind the headstock. Shoved the invar through the spindle and marked where it touched the board. Drill a hole with the battery drill and pass the invar through. It flexes easily at that length so it does not have to be spot on centre.

regards Martin

Free cutting stainless would be the 303 type The invar would be closer to the 303 than silver steel. No fancy exotic insert would be required as long as it is the correct profile for the thread. Just make sure that you are aware of the insert type ie Partial profile or full profile. Why not try what Martin has suggested, would save you all this trepidation. I would'nt have the skills or knowledge needed for clock making but Martin's idea should be just the ticket.

cheers

If you have a lot of bar sticking out of the far end of the headstock, DON'T run the lathe at high speed or you'll be £60 worse off - it will whip and bend through 90 degrees. Don't ask me how I know this....

Screwcutting speeds should be fine.

Rocol RTD cutting fluid might be a good option; I have seen it work wonders when drilling nasty hardened martensitic stainless steel.

Thanks Martin. I don't think I quite understand the Loctite idea... are you talking about adding a sleeve with a thread on it? it actually loctiting the pendulum bob at the correct height? I cant do the latter as it would prevent the rating nut from turning (and I am rather proud of the way my rating nut turned out... the first time my knurls turned out just about perfect!).

Love the idea about using some MDF. problem solved! I was going to try and rig up some wire loops on an old keyboard stand.

many thanks Raymond.

I will let you all know how I get on. I still need to get the invar but that's just a case of waiting for the Brooklands show in a couple of weeks.

Yes mate, threaded sleeve. You do need the gross adjustment although if you need to fine adjust the rate you do better with a weight pan some way up the rod with tiny weights in it that you can add or remove without stopping the clock. Precision clocks will always change rate when you stop and start them even if you haven't adjusted anything. Well all clocks do that but you only notice if the clock is good enough.

Regarding getting your Invar from the show, good luck with that unless you know something I don't. My last lot came from here. I've never seen any at a show and I've been to a few.

**LINK**

Some people have used carbon fibre for rods and I guess they would bond a tubular thread on cos I cannot see anyone threading that stuff.

Martin

thanks Martin

Noggins end has some and is bringing it to the show for me. he doesn't carry it around routinely because there are only about 6 of us looking for it!

I think I remember reading somewhere in the book about the weight try but haven't got to that bit yet.

I thought about using carbon fibre but it just somehow doesn't seem right.

Peter

Good oh, just didn't want you to be disappointed if it was just an assumption on supply.

I don't like carbon fibre on a traditional clock either.

What are you building?

Martin

Its the Peter Heimann 8 day regulator. I understand it was illustrated in ME a few years ago.

Its really been a bit of a challenge at times. The toughest part so far was turning the pendulum bob. a simple machining operation but really pushed the lathe to its limits. if it had been only slightly bigger it wouldn't have fitted in the lathe. its a bit scary swinging such a massive piece of metal if you have never done it before!

I only have a mini lathe (which is surprisingly good with the posh motor) and a mini mill which I am really not getting on well with but don't know why.

I have cut most of my wheels and made all but 1 of the lantern pinions and on my depthing tool, they seem to work ok. Recently I have been turning the barrels but messed up the first one. I was just pushing my machine too hard and the workpiece slipped. I have ordered an expanding mandrell and hopefully it will be better next time.

I have got 2 other problems looming on the horizon. firstly I don't entirely understand how the main barrel goes together. even with the drawings I could really do with a couple more pictures. and I have absoloutly no idea how I am going to make the pallets because my mill isn't up to the job of cutting siots as per the instructions.

All good fun. its really been a steep learning curve for me.

Peter

Edited By peter morgan 3 on 07/09/2016 15:35:30

A few regulators that I have come across have used wood for the pendulum rod. I used it for my 30 hour clock 5/16ths dowelling treated with beeswax. On my regulator I made the pallets by hand but they are not adjustable

Roy

I thought I would post a follow up on this one.

It worked a treat. in the end I had a small offcut so tried to thread it with a fairly new die. it worked fine so I just went with that. It gave me a chance to use my new Myford tailstock die holder.... Not really convinced. its a nice tool but I think I paid for the badge.

I am glad I had the right size collet. The force needed to thread would have been too much for the 3 jaw. it would have made a complete mess of my £60 rod.

Next step, suspension spring...