Fusing diameters of differing concentrics

[MWParticipant @mw27036]

So as the title suggests, this is a question about "how to go about it".

I've turned a diameter that is relatively concentric out of silver steel, however, i didn't realize that some of the diameter lengths are actually quite important, so the end result was something that was diametrically correct but not long enough,

as i don't have another piece of material thats long enough, i decided that i could cut the part length which wasn't right, and fuse it together with another turned diameter which was right using a thread.

However, the two diameters are not concentric to each other and therefore inappropriate.

I disconnected the two and have started again, this time however, i'm going only turn the thread, and leave the rest of the piece untouched.

Now, if i fuse the two together and then turn the rest of the piece whilst it's held in that correct main bit, then is it going to be concentric to it?

Michael W

[MWParticipant @mw27036]

[Michael GilliganParticipant @michaelgilligan61133]

Michael,

On another thread; You recently mentioned turning 'between centres' … That sounds like your best bet for the next stage.

Can you give us some numbers, please ?

MichaelG.

[Tony Pratt 1Participant @tonypratt1]

You would be better getting one piece of material, so much easier & in the end perhaps cheaper & a more satisfactory component?

Can we have more details for further advice.

Tony

[Raymond AndersonParticipant @raymondanderson34407]

Michael, could you give some info on the Ø's and lengths involved, and what it will be used for. Since its not a chunk of Inconel or some other mega spendy metal, it could well be cheaper [and will certainly better ] if you were to get a new piece of Silver steel. so I agree with Tony.

Cheers.

[MWParticipant @mw27036]

Sorry about the lack of info As i don't have a very good camera and it's awkward trying to get the pictures off it, but i will put some on here a bit later to show you what i was on about.

It's a spindle for a horiz-mill machine and part of it is the arbor for the 7mm bore cycloid pinion cutter, it needs to be concentric in order to make a decent cut with no chattering.

I could've bought some more material and made another but i'm not a fan of wasted effort so i like to save things if i think it can be rescued. So the 4.5" length of silver steel is completely turned ok, this length is what the machine itself is holding and the last little bit is the cutter arbor.

I managed to turn everything to the right dia. on the 1/2 inch bar, however, i messed up on the last length which was critical because it needs to sit on the center line of the milling axis, if i dont get the length right, it'll be cutting pinions askew to one side. So thats why i cut the end off basically.

Soo, i carried out what i said i'd do, the two dia. screwed and locked together and turned the end in the 3 jaw, held by the main length and tested it with a dial indicator and it barely moves to 0.01mm, i'm happy with this, and because i cut a relief at the end of the thread, the jointing piece fits right up to the shoulder, i turned the two together and now, you'd barely realise that they were once separated at all. I will call this a success!

hooray! Once it's all pieced together i'll put pictures on here.

Michael W

[Raymond AndersonParticipant @raymondanderson34407]

So it's a spindle/arbor for a horizontal m/m to hold the gear cutter [am I correct ]? ½" seems a small Ø for a spindle so please excuse me if i'm missing something. The main thing is you managed to "rescue "it , so well done. Maybe a good idea to Loctite the two together [since they were originally going to be 1 piece ].

Cheers.

[MWParticipant @mw27036]

Thanks ray, it's going ok so far,

This is a picture of the machine at work:

It might not look it but to my surprise that 3 jaw is very accurate, it only has an inherent run out of 0.01-0.02 (when a bar of known size is used within 50mm or so) i remember using an old 3 jaw at work that was 0.2mm out of round

And this is a picture of the fused bar in the lathe, with loctite on the internal M6 thread (i personally prefer a high strength anaerobic compound called bondloc, the specific grade is for fusing pulleys to shafts, much thicker and gloopier, i'd definitely recommend it),

the maximum runout of the fused bar is shown on the plunger dial indicator when held in it's mating spindle cartridge, i can't get more than 0.02 out of it. As you can see, no mating line is visible after turning, it's like it was always 1 piece!

sorry i couldn't get the picture the right way up.

If all else fails for runout you can always superglue cigarette papers to the offending O/D, it's a black art though and certainly not kosher, i now prefer to call them "diameter shims" to legitimize it's proper engineering usage. If you could hear me i'd be telling you in hushed tones 

Michael W

Edited By Michael Walters on 30/04/2016 21:14:04

[Raymond AndersonParticipant @raymondanderson34407]

Hi Michael, I'm with you now, Pic's always make things clearer. The spindle that is in your 3 jaw in the pic, is it the same one as in one of your albums ? Congratulations that you manage to salvage the part and still have a decent TIR. It would be wise sometime in the future to get a 4 j "independent " chuck for your lathe [will save you having to use your "Diameter shims " ] You got the job done thats the main thing

Cheers

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