Mandrel Morse Taper wobble

[NigeParticipant @nige81730]

I have been trying to insert a reference bar into the MT2 in the mandrel on my ML4. The problem I have is that with the bar inserted there is a very slight 'wobble'. It feels as if there might be a slight lip on the outside of the internal edge/lip of the mandrel as that feels like the area of the mandrel nose that the bar is 'tipping on. The bar wobbles in any direction so I suspect there is a very slight burr all the way round the opening of the MT.and I am sure I can feel a slight lip with my finger. The photo below is the best view I can get with the phone camera. The internal surface is not smooth which is no surprise i guess on a 70 year old machine but question is what can i do about it?

Would it be worth to trying taking a very light touch with a tool to remove any possible burr? What else might I try short of fitting a new mandrel? As always any advice very welcome

[NigeParticipant @nige81730]

[David Standing 1Participant @davidstanding1]

It looks a bit bashed around at around the 4 o'clock position.

Nothing to lose by putting a very small chamfer on the inside of the nose and seeing if the test bar then fits.

[Steve FParticipant @stevef]

Hi

Have you thought of trying a MT2 reamer just to try and clear the burr. RDG sell them **LINK**. Just an idea. I'm no expert

regards

Steve

[NigeParticipant @nige81730]

Thanks David. That light cut will be the very first cut I take with this machine

[NigeParticipant @nige81730]

Steve, thanks and yes I had wondered about that as an option though I have no experience with reamers of any sort let alone tapered ones. I had wondered about using an MT2 mandrel to try polishing the inside but not sure of the result I might get or any damage I may cause. Mind you, I cant use the morse taper now !! I think I will try with the very small chamfer first.

[HOWARDTParticipant @howardt]

Before you do anything, take a good morse taper blue it and lightly twist it in the spindle to see where it touches. Then decide on next step.

[NigeParticipant @nige81730]

Thanks Howard😀 I knew I was going to need some Engineers Blue before long; that's another item for the ever growing shopping list!

[David Standing 1Participant @davidstanding1]

Posted by HOWARDT on 24/07/2017 22:06:12:

Before you do anything, take a good morse taper blue it and lightly twist it in the spindle to see where it touches. Then decide on next step.

Now why didn't I think of that. Good idea!

[Bill Davies 2Participant @billdavies2]

Or to avoid the wait in getting some blue, use a soft "lead" pencil. Rub it up and down the taper, at several points around the circumference. When we were grinding tapers, we used a chinagraph pencil, that would also involve a trip to the shops or a wait for the Post! In old turning books, they used to use chalk, but I wouldn't vouch for the accuracy.

Bill

[duncan webster 1Participant @duncanwebster1]

cadge some lipstick. Thin smear will do. Not as good as Micrometer Blue, but a lot better than nothing

[BazyleParticipant @bazyle]

Felt tip works fine if it is not water based. Can raid the kids crayon box but that tends to go on thicker. test with more than one if using old drills etc for this as there will be some variation. Make sure the taper is warmer than the spindle so it doesn't expand and jam itself as you will only be using minimal oil.

[HopperParticipant @hopper]

Make a three-sided scraper by grinding the teeth off the end of a three sided file, run the spindle, apply scraper to the mouth of hole until a nice blended chamfer has been formed.

[not done it yetParticipant @notdoneityet]

First question might be "How hard is the metal?" If relatively soft, a morse taper with strips of fine abrasive carefully glued on, could be used to remove any high spots. If hardened, a reamer may not be an option – and if reamed it would need an absolute minimum of material removed while retaining concentricity. All morse tapers would fit that much deeper into the cone and it may have been reamed previously….

[NigeParticipant @nige81730]

Thanks for the ongoing advice guys especially on alternatives for Engineers blue. Much closer inspection of the mouth of the mandrel confirmed some raised edges so I went searching among the tools that came with the lathe. There is what appears to be a complete set of Myford lathe tools of the what I will call curved bed design. A shoe with a curve in it that mates with a curve in the tool and provides the height adjustment. Having found a tool that looked like it would do the job I could see the faces needed touching up. I have a brand new never been used (don't ask) Axminster grinder with a white wheel. I had to find a piece of wood to mount that on and then clamp it to the work bench. Tool touched up and mounted only to find that it was just too deep to fit into the hole. Hunt for a different tool, find nice thin boring bar (see photo), grind a bit off that to make it fit, set it up in the compound slide to take a fine(ish) taper cut. This was the very first cut on this lathe and the first cut for me on a metalworking lathe for me in about 40 years, a big moment for me. The result can also be seen in the photo 😊

Trying the reference bar in the mandrel afterwards the wobble is gone though I didn't clock it (too excited to have acheived something) and it still doesn't feel quite right. Next job is to get some marking 'stuff' onto the taper on the bar and see what is going on inside before deciding on my next course of action.

The tool did remove metal from the mandrel though I was only taking the lightest of cuts so unsure as to whether it was 'cut' off or rubbed off. Should I expect the mandrel to have been hardened after it had been machined in the factory?

[Mark RandParticipant @markrand96270]

An ML4 wouldn't have a hardened mandrel. That didn't happen until Super 7's and later ML7's with bronze bearings.

How did you make sure that the taper you bored matched an MT2 taper?

[HopperParticipant @hopper]

You likely still have a tiny burr around the end of the cut, best removed with a three-sided scraper or file by hand.

[David Standing 1Participant @davidstanding1]

Posted by Mark Rand on 26/07/2017 01:42:02:

How did you make sure that the taper you bored matched an MT2 taper?

He didn't bore the taper, only a mm or two at the mouth at a 45 degree or so angle to clean up the lip.

[Howard LewisParticipant @howardlewis46836]

If the "bluing" shows only slight mismatches, you could then select a 2MT drill / arborl / whatever, in which you are confident, and use some fine grinding paste to lap the two together. Don't overdo it, check frequently, and clean thoroughly, before each check.

BUT, when checking afterwards, use a different arbor for any "blueing" checks.

Finally, when satisfied, clean the bore of the Mandrel really thoroughly.

Howard

[SteveIParticipant @stevei]

Pending the results of the bluing test, how about cleaning it up with a morse taper 2 finishing reamer which has the correct profile for the spindle rather than "cleaning it up" with a boring tool? I know there is a (<£20) cost but perhaps you can borrow one from a local club? At least that way you are not risking modifying the taper away from MT2.

I am not familiar with this lathe but if the tail stock is also MT2 and given the age of the lathe it may be worth an inspection and the use of the same reamer.

Steve

[NigeParticipant @nige81730]

Thanks guys.

Mark: Thanks for confirming the mandrel not being hardened. I didn't bore the full length of the taper just cleaned up the first 1 or 2 mill of the opening.

Hopper: I have cleaned up any burr left, thanks for the suggestion.

Howard: Hi again mate. I have two morse tapers I can rely on and will try that as the final process.

Steve: Thank you. A finishing MT2 reamer is next on the list of purchases. The ML4 has a No1 MT in the tailstock but I am not having the problem with that one at the moment so that will get looked at later

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