Newbie Sticker still unremoved from my forehead.. Here we go.. with both left feet!

[Learning Curve]

I don't know what grade of material the original spindles were made from but if one were to make a new one from something like 4140, it wouldn't take much wall thickness to match the strength of the original. In doing the self-cleaning thread modification to the spindle nose, the original material files much like 1018 or some similar mild steel, if I remember correctly.

Yes I remember reading it is a mild steel. But the attachment of the Driven Gear on the outside is over an area I will not even be touching with my proposed Bore work... Please take a second and realise I am not trying to OPEN the WHOLE SPINDLE to 1 inch... I think everyone is looking at this like I will cut the entire bore.. The taper that opens to 1 " on the working end lies directly between the drive gear and the Chuck end threads.... The section I want to cut 1/16th out of begins in the shaft somewhere below the pulley and runs out to the change gears end of the shaft... I seriously do not see any real strenght issues here not in the small amount I wish to remove.. And 7/8th opening is an improvement and partially solves one of the notorious long standing comments about the limitations of these lathes. I have checked now and I will not lose ANY taper at all.... as the 29/32 I am going to go for begins in the center of this shaft... I will not be touching the working End (HALF) of the bore at all. I will try it on another shaft when I get an extra... I think this is worth the effort. If there is any reason for the bore taper to run 11" and that benefits me in some way I would like to know what it is.. And please stop me from ruining a perfectly good spindle. As it stands I will have 5" of taper.. I think that will hold any tapered tool I know of well enough and straight enough. Right?

 

[scwhite]

Excellent observation and again.... lets forget the gunbarrel... this fix is for everyone and anyone who has material of any type larger than 3/4" I see your point exactly but please take a second look just for the heck of it with me... I am measuring this taper as best I can now and from what I can see in a preliminary check.... this taper begins at the Working end of the spindle @ 1" but this is an 11" long shaft.. 3/4 Inch is achieved at the loading end.... I think we can all assume the taper is an exact instrument and continues undisturbed through the full 11" Now I have never seen an 11" dead center, chuck or tool of any kind that takes up the entire 11" to be accurate. From what I measure .....and logically we should all assume that 7/8" bore would be found in the center of this opening... Or @ 5-1/2" Dead Center in the bore... All I am going to be removing is 1/16th from the inside of the back half or "gear end" of this spindle. The working end will still maintain it's tapper as far as I can see... at least 5" of it... to hold any tools.... If you see my point.. I'f wanted to bore the whole shaft out to the full 1" through the bore, I'd loose any working taper and ruin the machine in this way as you warned. Yet @ 7/8th I think I am safe..? Does any of this make sense? For what it's worth I hope your not done looking at this and have spoken and moved on.... this is a good discussion to at least hash out a bit more... I think it would enhance many old machines if it works and there are those who want to try this. I certainly do not wish to propose madness here. Forgive me if I am... Your point is the best one against it but I really think they could have cut that spindle slightly larger at the factory years ago but they just didn't.

The taper don't go all the way through the Spindle
Bore . It just goes deep enough to get the full Dead center in full contact of the center .

 

[scwhite]

Excellent Point.. I am looking as we speak.. I do believe this is completely doable but I do not wish to ruin anything.. My measurements right now seem to show no loss of any taper at the working end of this bore. I have to find my old millwright tool box I think I have some bore gauges in there that will reach through the shaft and verify the tapper and my 29/32 goal beginning near the midway point... Where's that old bunch of long calipers when I need them? I will try this soon once I find another shaft to experiment on. And there's one of the GREAT POINTS of these lathes. Parts are everywhere..!

That taper is not very long . It is just long enough
To get a full fit on a # 3 MT .
That taper should be in the neighborhood
Of 3-1/4 long .

 

[scwhite]

Of course the engineering weaknesses are in play here. If I wanted to ream this out drastically I would not even have proposed it... but thanks for the observation... it was not lost on me at all. But we are not talking the stresses of a crankshaft on a car... this small lathe is opened to 1" on the working end for the taper already... and my bore would only begin near the center of the shaft and work toward the loading end of the shaft and we are talking about removing 4/32" of material.. not a 1/4 of an inch... No way to answer the engineering stresses without a total mathematical workup...

That taper will almost completely be lost if you
Bore out that machine .
You are talking about boring it out
.125 on the Dia.
The taper is only .150 you want have anything left .
The large end should be .938 Dia. And the Small end is .778 Dia. On a # 3 Morse Taper

 

[Reeltor]

Not sure how to make that work. Need to spin the barrel and need room to thread the end. 12x 24" Perhaps I am missing something.. I am a newbie afterall.

How long is your gun barrel? I think I'm missing something,

 

[RJSakowski]

The reason the lathe has the current bore diameter is to accommodate the MT3 taper. If you open the diameter to 29/32 or .906", you will lose all but 1/2" of that taper and it will be destroyed. As has been previously mentioned, a very useful function of an engine lathe is the ability to work between centers. For short work pieces, you can, of course, mount a bar in a 3 jaw chuck and turn a driving center in situ.

But the bottom line is that the lathe is yours to do with as you please. We all have our opinions as to the wisdom of seriously modifying a piece of machinery (some time ago a thread was posted where a lathe was turned into a barbecue spit to roast a steer; check the posts to see the comments made there) but they are our opinions not directives to you. As a wise old farmer was said to me "I'll give you some free advice; take it for what it's worth".

 

[Learning Curve]

The taper don't go all the way through the Spindle
Bore . It just goes deep enough to get the full Dead center in full contact of the center .

OK, so again considering it

That taper is not very long . It is just long enough
To get a full fit on a # 3 MT .
That taper should be in the neighborhood
Of 3-1/4 long .

Well then that might cause me to loose quite a bit if it only 3 - 1/4 long... but I have not found my tools yet and I need to verify with actual numbers to be sure. If this is the case you may be quite right and removing the 4/32 of material will perhaps not eliminate the taper but reduce its seating qualities as there will be some loss on the narrow end.... Again I will verify soon.

YEP. it's verified.... I bet this would still take a live center % that it might even still work...but for the small gain in size it's just not worth risking the damage if those centers don't run perfectly true. I'll just read the threads and enjoy learning now... my bad.

 

[Learning Curve]

How long is your gun barrel? I think I'm missing something,

Longer than the bed will handle.... and again the barrel is NOT the only consideration... I was wondering if This could be done so many other applications could fit in that bore hole... So far the consensus is I will damage the taper to much for it to be of worth.. I will verify with good measurements soon enough... If this is the case that's too bad, as it would be a fun and easy modification to increase the capacity of many old machines.... But then I suppose if was this simple someone would have thought of it before. I noticed this thread says it's being "watched" what does that mean? Sounds ominous... lol !

 

[Learning Curve]

The reason the lathe has the current bore diameter is to accommodate the MT3 taper. If you open the diameter to 29/32 or .906", you will lose all but 1/2" of that taper and it will be destroyed. As has been previously mentioned, a very useful function of an engine lathe is the ability to work between centers. For short work pieces, you can, of course, mount a bar in a 3 jaw chuck and turn a driving center in situ.

But the bottom line is that the lathe is yours to do with as you please. We all have our opinions as to the wisdom of seriously modifying a piece of machinery (some time ago a thread was posted where a lathe was turned into a barbecue spit to roast a steer; check the posts to see the comments made there) but they are our opinions not directives to you. As a wise old farmer was said to me "I'll give you some free advice; take it for what it's worth".

Yep.... Damn .. you guy's were right. That's too bad... I thought this would be a nice little modification... I verified it... the taper is just as you say it is... and although I will not remove it all I will remove just under half of it... leaving about an 1 - 1/2" to seat on any centers I use... Not worth doing if I risk losing that much taper. Well, I suppose us newbies get all excited about things then find out it's been done or just won't work. It's what hooks us into this madness to begin with I guess! Sorry for the time expenditure with such small return. I will just get used to the larger lathe... and probably end up selling the smaller lathe in the future.. Right now it's just too much fun...!

 

[3strucking]

You are being watched by the man. You are now on some list somewhere like the rest of us.

It means that you are watching it since you posted in it.