Boring the MT2 on spindle

[Howard LewisParticipant @howardlewis46836]

If reaming a machine spindle, in situ, (such as from the Tailstock) it would be advisable for the reamer to float, so that it follows the centreline of the original bore. A fixed reamer, if off centre, is likely to act as a boring bar, cutting on one side only, so producing oversize, which could be a problem.

Howard

[SteveIParticipant @stevei]

Posted by Martin Dowing on 07/12/2017 22:38:51:

I am planning to correct MK2 socket on my ML7. It is one of last jobs to be done on my old otherwise accurate lathe. To this end taper turning attachement will be deployed. Jig for holding a bigger version of Dremmel, designed to be mounted in the lathe, is now under construction. It will have dovetail slide tangentially set, so very accurate adjustments can be made. Phosphor bronze bearings which are actually not a bad fit as they are now will be professionally scraped in (I am not up to the task yet), headstock allignement will be made as close to perfect as possible (this is now not a problem for me, can do it and well) and then socket will be corrected with few tenths cut.

I will even possibly make 2 or 3 spare spindles from suitable material, all in perfect allignement, socket ground in the machine and nitrogen harden them. Recently I am studying research papers treating about cyanate bath for nitriding. These work in lower temperatures (450*C) than cyanide bath does (600-700*C) and are also substantially less toxic.

Martin

Martin,

Very interesting comment there about hardening at lower temps. In the past the late Mr Stevenson added a few items of mine for hardening in with his regular order over at Carlisle Brothers. I no longer have a hardening solution. So DIY is potentially of interest. Do you have any more details?

Thanks,

Stev

[sean logieParticipant @seanlogie69385]

Can we keep the thread on topic please .

Sean

[Martin DowingParticipant @martindowing58466]

@Steve,

Cyanate bath is prepared from urea (fertilizer) and soduim or potassium carbonate (washing soda) according to equation:

Na2CO3 + CO(NH2)2 —> 2 NaCNO + 2H2O.

Reaction goes at about 450*C. Working bath contains about 20-40% of cyanate and also other salts. You need to pass stream of air during process to prevent accumulation of much more toxic cyanides. Some ammonia is liberated as another by-product, so well ventilated hood is recommended. There is a considerable knowledge of chemistry and laboratory practice required to get satisfactory results and to operate process efficiently and safely (I am MSc chemist and was working as research chemist in pharma for 10+ years).

It is a good idea to read some research papers before attempting this process.

Read publication linked below and also references included there (if you trial-register with DeepDyve, you will get 2 weeks long free access to download what you need)

https://link.springer.com/article/10.1023/B:MSAT.0000048834.48163.2e

We should keep this thread on topic as there are complains. Send me PM, if you find this subject interesting.

Martin.

[Chris TriceParticipant @christrice43267]

Posted by Howard Lewis on 08/12/2017 11:23:15:

If reaming a machine spindle, in situ, (such as from the Tailstock) it would be advisable for the reamer to float, so that it follows the centreline of the original bore. A fixed reamer, if off centre, is likely to act as a boring bar, cutting on one side only, so producing oversize, which could be a problem.

Howard

If it were a parallel reamer, that might be true but it's a taper reamer so if it were off centre but parallel with the head stock, it would still produce the correct taper. It's more likely to create a taper that is too wide at the wide end if the whole set up has any flex because the narrow end will tend to follow down the centre of any pre-existing bore while the wide end is being pushed off to the side slightly by the off centre tail stock. My preference posted earlier is to machine the taper to a near finished size then finish ream it with a tap handle gripping the square of the reamer and very slowly turn the spindle by hand or carefully under power using plenty of lubricant and feeling the cut.

[sean logieParticipant @seanlogie69385]

I used a live centre to hold the reamer in place applying gentle pressure whilst I turned the reamer with a metric adjustable shifter .

Sean

[John MCParticipant @johnmc39344]

The way I have ensured absolute concentricity with a morse taper spindle on a milling machine (is this what the spindle is for?) is to finish in situ. I made a new spindle, reamed the taper while still in the lathe, assembled on the machine. Then tipped the head over to bring the surface of the taper vertical, clamped a boring bar vertically on the table and fed the bar up in to the spindle. It took a couple of adjustments to the angle of the head to get the tapers to match perfectly. On assembled, (after reaming), the taper was "out" by about 1.5 thou, no run out at the wide end of the taper, the error being farther up the socket. After machining as described no error.

I've done this twice now, requires a great deal of care in setting up but well worth the pain!

Hope this helps, if not, apologies for rambling on.

John

[sean logieParticipant @seanlogie69385]

It was suggested on here that I could ream my spindle in situ on the mill when I've mounted the head . I mounted the head today ,still needs a bit of fine tuning but it's in place . I set up a test indicator up against a end mill in the spindle and I have 5 thou run out …. How would I set up the reamer on the mill to try and true up the taper . I suppose if I have to I could make another if this one's not fixable . Be interested to hear you thoughts on this .

Here's a link to my Flickr with the new designed mounting ,I decided to weld the spindle and over arm if you like directly to each other .

Sean

Sean

[JasonBModerator @jasonb]

The reamer is most likely to just try and follow the off ctr hole

[sean logieParticipant @seanlogie69385]

My thoughts as well Jason .

Sean

[HopperParticipant @hopper]

You won't true that runout with a reamer. Reamer will follow the existing hole. Correct procedure for using a reamer for precision jobs is to

1. Drill the hole to remove metal quickly.
2. Bore the hole to establish correct location, concentricity and orientation.
3. Ream the hole to achieve final size and finish.

With a precision taper such as a spindle like this, the reamer is best used to remove perhaps the last thou of material, about one or two turns with a hand reamer, just enough to remove the highspots from the boring tool marks on the job.

Spindles like this are best made where the OD and the taper are machined in one set-up on a lathe that is known to turn parallel within a few tenths of a thou at least. IE in a large lathe where the large chuck will hold the spindle raw material by one end while the full length is machined to diameter and then the taper drilled and bored and finish reamed.

If you only have a smaller lathe, one way is to machine the female taper in the spindle, then machine an arbor between centres with a male taper on it. The spindle is then mounted on the arbor and the OD turned to size. You may be able to use this method to remachine the OD of your spindle now, so that the OD is concentric with the taper. YOu would then have to fit and machine sleeves to bring the OD back to size to fit your bearings.

.

Edited By Hopper on 11/02/2018 03:13:39

[sean logieParticipant @seanlogie69385]

Well curiosity had the better of me ,nowt to lose so I tried the reamer this morning,I set the spindle up in the 4jaw used the live centre on the tailstock end of the reamer, the result was surprising . When I refitted the spindle into the head runout went from 0.005" to 0.002" . Well chuffed ,still 2 thou is 2 thou I suppose .Think what I'll try next is to set up the reamer up on the mill ,I have a spring loaded centre I use for tapping threads in the lathe so I'll see if that works with the spindle in place .

Sean

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