Thread: Lathe basics: Spindle centre error

Originally Posted by Bryan

Ok. Got a strong reading at the mouth, not much elsewhere. Chief Tiff, no-one said it was accurately machined. I measured up the bore as best I could and calculated an angle of I think 1.25 deg. Knowing full well my compound scale is not to be trusted, I went for trial and error. My error was not enough trial. I should have blued it. Besides which, I'm guessing I should have used the tailstock method rather than the compound. That aside, I'm sure I could get it a lot better now.

Not having a male 4.5 MT to measure, anywhere in the known universe, makes it hard. I can only find specs on whole numbered MTs, and the taper varies, as you seasoned machinista would know: Machine taper - Wikipedia, the free encyclopedia.

Dave J, I will also try your headstock test when I get a chance. I did recently have it apart and was unsure how much to preload the bearings, so went for 'not much' to be safe. Maybe they've settled.



But I think the main mystery has been solved: I botched it!
Thanks guys.

I have four carbide tipped MT dead centres that are larger than a four which I assumed are fives. They were bundled in with a mill I scored at an auction but I suspect they are for Sheraton lathes as there were four for sale at the auction.

What are your dimensions for a 4.5?, I can check these centres out and see if they are what you want.

Originally Posted by Graziano

What are your dimensions for a 4.5?, I can check these centres out and see if they are what you want.

My notes give diameters of 37 and 35.3 mm, and length of 40 mm - quite stubby. The only number I'm pretty confident of is the large diameter; the others I wouldn't bet my life on. If yours are in the same neighbourhood I'll have another go. Thanks a lot.

Some great info coming up BTW. Old hat for most of you I guess But I'm really appreciating it.

Originally Posted by Bryan

My notes give diameters of 37 and 35.3 mm, and length of 40 mm - quite stubby. The only number I'm pretty confident of is the large diameter; the others I wouldn't bet my life on. If yours are in the same neighbourhood I'll have another go. Thanks a lot.

Some great info coming up BTW. Old hat for most of you I guess But I'm really appreciating it.

I was going to post it to you if it's the right one. These are about 20 cm long, kind of looks like an armour piercing round or something to me. If it's for a lathe spindle then the excess will just poke down the spindle bore. I won't be able to take a pic for two days though.

I have never heard of a morse taper 4.5

I am wondering if it could be a Jarno or Brown and Sharpe, or a National American taper or even a metric taper..

There is certainly no Morse Taper 4.5 listed here

There are other taper sizes listed there as well.

It's easy to find places it's NOT mentioned. One place it IS mentioned is in the Lantaine owner's manual. Another apparently is certain editions of Machinery's Handbook. I read that in one of several forum discussions I found when googling. I think we can say it exists. Whether it should really be called something else is another matter.

Originally Posted by Graziano

I was going to post it to you if it's the right one. These are about 20 cm long, kind of look like an armour piercing round or something to me. If it's for a lathe spindle then the excess will just poke down the spindle bore. I won't be able to take a pic for two days though.

That's a very kind offer, Graziano. Thank you. Let's see if the size is right first.

Originally Posted by Bryan

It's easy to find places it's NOT mentioned. One place it IS mentioned is in the Lantaine owner's manual. Another apparently is certain editions of Machinery's Handbook. I read that in one of several forum discussions I found when googling. I think we can say it exists. Whether it should really be called something else is another matter.

I have the 28th Edition in pdf form, there is no Morse Taper 4.5 mentioned in there, but there is a ANSI/ASME B5.10 Taper listed there in 4 1/2.

You should find that the Large diameter is 1.500" and the Small diameter 1.266",the length should be 4.3125" for standard 4 1/2 M/T.
It is the same angle as a M/T 7 1 1/2 Degrees.

I do not think there is such a taper as a 4 1/2 morse.. It is an American taper as shown here

Shop reference for students and ... - Google Books

Originally Posted by .RC.

I do not think there is such a taper as a 4 1/2 morse.. It is an American taper as shown here

Shop reference for students and ... - Google Books

Which one, the 4 1/2? The large diameter is 1.5"; mine is 1.456". I measured it reeel careful. No way it's 1.5. And I can't find anything in any of the taper tables with that diameter (thanks for the various links BTW). It's an interesting anomaly, but what's more interesting to me is, can I make something to fit it?

I tried Dave J's method today. I liked the idea of it but found it harder than it sounds. It kinda needs to be a round bar to be sure of full axial contact. And it has to be dead on centreline or your indicator will be thrown out. I spent quite a bit of time getting it chocked just so and got the indicator reading steady. But the resulting taper was no better than the first attempt. This time the contact was all at the small end. I'm not saying it's a bad method, just that it needs a lot of care to get right and as a novice I failed.

So I gave the compound a squint and a nudge and tried again. My centre now reads 'true' (<.01) when registered to the spindle. Which is not perfect but at least it's usable. Before I try some of the other methods mentioned I'll need to get some more material. My poor little workpiece has been whittled away to nothing.

Hi Bryan,
It can be fiddly to get set up to get a true reading.
Just another thought.
Most tapers have around 75% contact, since your so close you could try machining the middle out of the taper so only about 15- 20mm of each end contacts. Use your texta or blue it up, then use some emery paper on the large end to bring it down to size. It might be all it needs.
Dave

Bryan do you have anything that is round,a piece of centreless ground bar or similar would be good to use.
Set the bar up running true in your chuck or between centres and adjust your compound untill you can get it set for the M/T 4 1/2,they are .052" taper/inch.
It want matter if the spindle bore is smaller or bigger than 1.500" the taper will bottom itself out.

Originally Posted by Bryan

My notes give diameters of 37 and 35.3 mm, and length of 40 mm - quite stubby. The only number I'm pretty confident of is the large diameter; the others I wouldn't bet my life on. If yours are in the same neighbourhood I'll have another go. Thanks a lot.

Some great info coming up BTW. Old hat for most of you I guess But I'm really appreciating it.

I found the MT5 dead centres, they are about 44mm at the wide end.