# Confused with spindle specs



## peter.van.haren (Feb 10, 2020)

My Yang 14x22 lathe spindle specs are in the attached picture.
What is the "Center" in Taper of Center - Morse Taper #3? 
The Spindle bore is 1.77", and that is a lot bigger than a MT3.
There is also a Taper of Spindle Bore 1/30. Is the the inside taper of the spindle nose?
The tail stock taper is MT4.
(Happens to be a M48x20 LH thread at rear of spindle)
Thanks!
Peter
	

	
	
		
		

		
			








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## Cadillac (Feb 10, 2020)

You will need a mt5 to mt3 adapter unless it’s a oddball size. Looking at your measurements it might be bigger than a mt5. Pretty common


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## peter.van.haren (Feb 11, 2020)

Yes, the hole might be bigger than MT5 (1.77" spindle bore vs 1.74" max of MT5). My measurements are certainly approximate and I don't have anything in MT5 to try it.
Still wonder why they write Center of Spindle as MT3??? Smaller yet!
Also the spindle nose being ASA A1-5, I can't see anywhere if the internal bore of that nose is a MT taper. Thoughts?
Thanks a bunch!!

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## Superburban (Feb 11, 2020)

Every bigger lathe I have owned, came with a taper adapter to fit the advertised taper into the spindle. Basically just looks like a 1/2 length MT 5 to 3 adapter.


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## darkzero (Feb 11, 2020)

A1-5 & D1-5 size spindles usually have a MT5 taper. Not sure why that spec sheet lists those specs but lathes commonly come with a spindle taper adapter to match the tail stock taper. Not always I guess but usually it seems. But you stated your tailstock is a MT4 so I would figure your lathe would have came with a MT5 to MT4 sleeve.

But the reducing sleeves used in the spindle are not the same as reducing sleeves used for arbors that would go in a tailstock or drill press. They are usually shorter & have an open end, no tang feature. The sleeve for a drill arbor will still fit in the spindle but it most likely will stick out too far if used for turning between centers. Same if you just use a MT5 center instead of a the spindle reducing sleeve.

Reducing sleeve for a drill/tool arbor






Reducing sleeve for a center used in the spindle


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## peter.van.haren (Feb 11, 2020)

Thank you Superburban and Darkzero,
I ordered a mt5 - mt4 adapter sleeve, so will know soon enough. Wondering if the spindle center mt3 is a typo? Entirely possible.
The 1:30 spec still has me baffled, but it is the spindle center that might be solved first.
More questions to come....ok? ;-)


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## rgray (Feb 11, 2020)

1:30 taper 1 inch of taper for 30 inches of length. Or 1mm for every 30mm of length. 
On that lathe it's probably the metric.


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## Stonebriar (Feb 11, 2020)

I have a 1440gt and it list the spindle as a 5 1/2MT taper. And who ever heard of that odd size.  But it came with a 5 1/2 to MT3 adapter.


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## peter.van.haren (Feb 11, 2020)

rgray said:


> 1:30 taper 1 inch of taper for 30 inches of length. Or 1mm for every 30mm of length.
> On that lathe it's probably the metric.


Thanks. Yeah i figured the 1:30 means (only because I'm familiar with roof pitch/slope), just not sure what the taper of spindle bore 1:30 vs taper of the center MT3 (typo?) is. As my Thai business partner always says..."learning by doing"

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## peter.van.haren (Feb 11, 2020)

Stonebriar said:


> I have a 1440gt and it list the spindle as a 5 1/2MT taper. And who ever heard of that odd size. But it came with a 5 1/2 to MT3 adapter.


Good grief! Hope its not a odd size like that! Anyway, didn't get an adapter, but can always ask the importer if "we" get stuck, I guess. By the way, its a Used import from a Taiwanese school.

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## peter.van.haren (Feb 20, 2020)

Well its not a MT5. Bought one and it's too small. Back to the drawing board.

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## darkzero (Feb 21, 2020)

Well damn that sucks. MT6 is obviously too big according to your measurement. Maybe you do have that odd size MT5.5 that Stonebriar mentioned. But I'll just keep my mouth shut now, feel bad that you wasted money on one that didn't fit. Hope you get it figured out & keep us posted.


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## peter.van.haren (Feb 21, 2020)

no worries.  not expensive, and my own fault.  could have easily measured the smallest diameter and known it was too big for MT5, but I didn't.
I've asked my local importer (the seller I got if from) and he's trying to find out.  Apparently not many Thai people use a center to put into the spindle nose, but he's looking for me.
What I have found out is that although the manufacturer specs it as ASA A1-5, it must be a modified spec. The American Standard drawings don't indicate any taper inside the spindle nose, however there is definitely a taper. 
Last night I measured (as best I could) and got this:
Length of inside taper: approx 60mm from front face of nose.
I.D. at opening (big end): approx 46.9m
I.D. at inner end (small end): approx 45.45mm
This means the taper is approximately 0.725 ((46.9-45.45)/2) over 60mm.
So, even if the manufacturer states one spec as 1:30 taper of spindle bore, the measurements I got don't indicate that.
Geometry never was my strong suit so, I could be mistaken, but that's never happened before! ha ha ha
Thanks for your comments!


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## Tozguy (Feb 21, 2020)

The 1/30 spec might mean 1 degree 30 seconds, maybe?
The included angle would be 3 degrees.
If that's the case, anything that gets set in there would be difficult to remove (like how well Jacobs tapers hold drill chucks)


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## peter.van.haren (Feb 21, 2020)

Tozguy said:


> The 1/30 spec might mean 1 degree 30 seconds, maybe?
> The included angle would be 3 degrees.
> If that's the case, anything that gets set in there would be difficult to remove (like how well Jacobs tapers hold drill chucks)


Good point, point I was just looking like 1:30 and not in degrees/minutes/seconds.  Given the measurements I made it looks like it's an acute angle of approx. 0.7 degrees.  Given that my measurements are approximate (best I could do with telescopic bore gauges), is your theory close.  
Also a good point about removing anything I insert, but perhaps could knock it out from the other end.
Your comments and help are GREATLY appreciated.


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## NortonDommi (Feb 21, 2020)

My lathe is a D1-5 spindle with a MT6 taper. Came with a MT6 - MT4 adaptor. Tailstock is MT4.


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## Tozguy (Feb 21, 2020)

If your calculations give you .7 degrees on one side then the included angle of 1.4 degrees is real close to 1/30'. That is a very slow taper.
However if it is .7 included then it boggles my mind as to why it was made that way.

My MT5 to MT3 sleeve is a very tight fit in the spindle taper, as it should be. An MT 5 taper is much steeper than yours but still sticks like gangbusters. The idea of pounding it out with a mallet never settled well with me so I made a puller. The puller just pops it out without taxing the spindle bearings.

Since your spindle taper is not so common you might consider making your own custom sleeve from an MT6 to MT3 sleeve.


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## peter.van.haren (Feb 25, 2020)

Just got a copy of the owner's manual. 
So, looks like you were right. It is 1° 30' 03" taper.
Any idea what type of taper that could be?






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## Tozguy (Feb 25, 2020)

I am not familiar with a taper like that. Could it simply be a funnel for inserting long work into the spindle bore?
If the diameter of 43.13 is larger than the bore of the spindle then the taper would prevent hangups when inserting work through the spindle. My D1-4 spindle bore is stepped instead of having a taper and work has to be inserted carefully so it does not bump on a shoulder.


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## John O (Feb 25, 2020)

google show morse taper as about 1.5 deg from center so angle is close.
Size is between a 5 and 6 morse.


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## Tozguy (Feb 25, 2020)

peter.van.haren said:


> Well its not a MT5. Bought one and it's too small. Back to the drawing board.
> Sent from my SM-N960F using Tapatalk


Peter, which was too small, the sleeve or the internal taper. It is normal for a sleeve to stick out a bit from the spindle. Or did the MT5 sleeve go too far into the spindle? 

Based on calculation, a good portion of an MT5 sleeve should fit in the spindle but with some sticking out.


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## peter.van.haren (Feb 25, 2020)

Tozguy said:


> Peter, which was too small, the sleeve or the internal taper. It is normal for a sleeve to stick out a bit from the spindle. Or did the MT5 sleeve go too far into the spindle?
> 
> Based on calculation, a good portion of an MT5 sleeve should fit in the spindle but with some sticking out.


Guess I should have been a little more clear. The MT5 sleeve (OD) was too small. 
The largest OD of an MT5 (from Google) is approx. 44.4 mm, but the smallest ID of the nose taper is approx. 45.45 mm. or about 1 mm too big
The MT5 can be pushed all the way into the spindle bore.

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## peter.van.haren (Feb 25, 2020)

John O said:


> google show morse taper as about 1.5 deg from center so angle is close.
> Size is between a 5 and 6 morse.


Yeah, another commenter said his was a 5 1/2 Morse Taper. 
Oh brother...Google doesn't know MT 5 1/2... so I can't (so far) find one. 



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## peter.van.haren (Feb 25, 2020)

Tozguy said:


> I am not familiar with a taper like that. Could it simply be a funnel for inserting long work into the spindle bore?
> If the diameter of 43.13 is larger than the bore of the spindle then the taper would prevent hangups when inserting work through the spindle. My D1-4 spindle bore is stepped instead of having a taper and work has to be inserted carefully so it does not bump on a shoulder.


Yeah, where my spindle nose meets the spindle bore, there's a small step there too.

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## brino (Feb 25, 2020)

My calculator says that 1 degree, 30 minute, and 3 seconds is equal to 1.5000833 degrees in decimal.

-brino


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## peter.van.haren (Feb 25, 2020)

John O said:


> google show morse taper as about 1.5 deg from center so angle is close.
> Size is between a 5 and 6 morse.


I noticed that some MT specs have slightly different taper angles. 
Wiki shows a MT5 as 1°30'26". Real close to what my manual specs. Thus I'm assuming mine is a Morse, but bigger than a 5 and smaller than a 6.
Geeze! 

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## Tozguy (Feb 25, 2020)

peter.van.haren said:


> Guess I should have been a little more clear. The MT5 sleeve (OD) was too small.
> The largest OD of an MT5 (from Google) is approx. 44.4 mm, but the smallest ID of the nose taper is approx. 45.45 mm. or about 1 mm too big. The MT5 can be pushed all the way into the spindle bore.
> 
> Sent from my SM-N960F using Tapatalk


I'm confused because the drawing in post 16 shows the largest end of the taper to be 43.13 which converts to 1.698". So an MT5 taper that goes from 1.748 to 1.475 over 5.19'' should not pass through that spindle taper. The MT5 sleeve should bottom at roughly 80% of contact in the taper.

If we disregard the drawing and base our calculations on your measurements (the preferred approach ) then one option would be to buy an MT3 solid socket and turn the outside to suit your spindle.
For example:




__





						Amazon.com: TTC 3MT ID x 2" OD Solid Socket w/Morse Taper Hole : Industrial & Scientific
					

Buy TTC 3MT ID x 2" OD Solid Socket w/Morse Taper Hole: Tapered - Amazon.com ✓ FREE DELIVERY possible on eligible purchases



					www.amazon.com


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## Stonebriar (Feb 25, 2020)

peter.van.haren said:


> Yeah, another commenter said his was a 5 1/2 Morse Taper.
> Oh brother...Google doesn't know MT 5 1/2... so I can't (so far) find one.
> 
> 
> ...


You can get one from Precision Machine.  Tell them its for a PM1440GT spindle. I don't know if they would ship to Thailand.


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## peter.van.haren (Feb 26, 2020)

This is what I found..
.so far
Looks rough so will continue fishing..
	

	
	
		
		

		
			








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## peter.van.haren (Apr 7, 2020)

Finally got it. My lathe seller made one up for me, free. Outer taper is MT, but in between MT5 and MT6. Inside MT 3. 
Thanks for all your help.
	

	
	
		
		

		
		
	


	










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## Tozguy (Apr 7, 2020)

Good to hear Peter. Now you are off to the races!
What do you have planned for the MT3 stub arbor?


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## brino (Apr 7, 2020)

It looks great, and you cannot beat the price!
-brino


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## peter.van.haren (Apr 9, 2020)

Tozguy said:


> Good to hear Peter. Now you are off to the races!
> What do you have planned for the MT3 stub arbor?


I bought a few blank "stub" arbors. Seemed like a good idea at the time.....
One will be for a center drill holder, the other hopefully a small live center. Both at tail stock. 
Other one, don't know yet. Suggestions?

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## peter.van.haren (Apr 9, 2020)

brino said:


> It looks great, and you cannot beat the price!
> -brino


Was a surprise actually. I asked if he could find one and he showed me that crappy one pictured earlier. Next thing that happened was a surprise package at the door! The finish quality is flawless, although not sure about runout...

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## Tozguy (Apr 9, 2020)

peter.van.haren said:


> I bought a few blank "stub" arbors. Seemed like a good idea at the time.....
> One will be for a center drill holder, the other hopefully a small live center. Both at tail stock.
> Other one, don't know yet. Suggestions?
> 
> Sent from my SM-N960F using Tapatalk


If one has a drawbar thread instead of a tang you could make an ER chuck with one. Calculate the maximum ER size you could use. Then buy the nut and collets. Get the nut before cutting threads on the chuck.
Then you would not need a separate centre drill holder.


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