- Joined
- Oct 29, 2012
- Messages
- 1,328
My Logan 9" has #3 Morse Taper in the spindle and it's been mangled since day #1 (by previous owner, not me). I bought a #3 morse taper reamer to fix it years ago, but never did, because I was afraid of making the taper too deep. I rarely use the spindle taper and it was easier to just pretend there was no problem.
But last night I needed to use a draw collet and I just could not get it to run true because of this ruined internal taper, so I dusted off that old reamer and went to work.
I took a series of light cuts, checking the growth of the contact patch and the runout of a fitted center until I got an "acceptable" result. Here you can see the progression of the contact patch:
As I watched the contact patch grow and the runout improve, I saw the center draw further into the spindle. This was not a hapless accident; it was wholly anticipated, but here is the final result:
My draw collet is now recessed a full half inch into the spindle. It's still usable (for draw collets at least) and runout has been reduced from 9 thou to 0.3 thou, but I won't be able to use other tools in it, like a MT3 Jacob's Chuck for example. My MT3 center protrudes just a faction of an inch, borderline unusable.
I would like to return this to full functionality if possible. Here are some of my ideas; please shoot them down or vouch for them as appropriate, or add your better ideas to the list.
1. Get a #4 MT reamer and open it up to MT4. At best, this would beg the acquisition of new MT4 tooling and the obsolescence of my existing (and until now, unused) MT3 tooling. At worst, it would thin my spindle nose to an unacceptable level. This is a 1.5"-8TPI spindle; are there any lathes that ship with a 1.5" spindle and MT4 taper?
2. Get #4 MT reamer and ream it out but not all the way (just large enough to be able to fit a MT4->MT3 sleeve) then part off the sleeve and go into the sleeve with the MT3 reamer to bring the engagement depth back to the normal point.
3. Continue deeper with the MT3 reamer (the first picture in this post was the end of my last cut, so you can see how much deeper I could take it) and machine my own MT3->MT3 (deep/oversized MT3->normal MT3) sleeve. I could cut an extended MT3 taper on the OD of a piece of bar, freeze the bar and (gently) heat the spindle, then drive the bar in as deep as possible for an interference fit once temperatures normalize. Then bore out the bar and turn a MT3 taper on the ID for a permanent sleeve repair. I favor this idea most, but I don't know if the sleeve would be thick enough. it may be so thin that the interference fit wouldn't be enough to keep it in place; it might come out with the first tool that gets driven in too hard - I don't know, just thinking out loud.
4. Leave it as is. Being able to accurately hold stock in a draw collet makes it more functional than it was before, and I used it for years without being able to do even that. Any further action involves further risk and maybe it's best to just quit while I'm ahead.
But last night I needed to use a draw collet and I just could not get it to run true because of this ruined internal taper, so I dusted off that old reamer and went to work.
I took a series of light cuts, checking the growth of the contact patch and the runout of a fitted center until I got an "acceptable" result. Here you can see the progression of the contact patch:
As I watched the contact patch grow and the runout improve, I saw the center draw further into the spindle. This was not a hapless accident; it was wholly anticipated, but here is the final result:
My draw collet is now recessed a full half inch into the spindle. It's still usable (for draw collets at least) and runout has been reduced from 9 thou to 0.3 thou, but I won't be able to use other tools in it, like a MT3 Jacob's Chuck for example. My MT3 center protrudes just a faction of an inch, borderline unusable.
I would like to return this to full functionality if possible. Here are some of my ideas; please shoot them down or vouch for them as appropriate, or add your better ideas to the list.
1. Get a #4 MT reamer and open it up to MT4. At best, this would beg the acquisition of new MT4 tooling and the obsolescence of my existing (and until now, unused) MT3 tooling. At worst, it would thin my spindle nose to an unacceptable level. This is a 1.5"-8TPI spindle; are there any lathes that ship with a 1.5" spindle and MT4 taper?
2. Get #4 MT reamer and ream it out but not all the way (just large enough to be able to fit a MT4->MT3 sleeve) then part off the sleeve and go into the sleeve with the MT3 reamer to bring the engagement depth back to the normal point.
3. Continue deeper with the MT3 reamer (the first picture in this post was the end of my last cut, so you can see how much deeper I could take it) and machine my own MT3->MT3 (deep/oversized MT3->normal MT3) sleeve. I could cut an extended MT3 taper on the OD of a piece of bar, freeze the bar and (gently) heat the spindle, then drive the bar in as deep as possible for an interference fit once temperatures normalize. Then bore out the bar and turn a MT3 taper on the ID for a permanent sleeve repair. I favor this idea most, but I don't know if the sleeve would be thick enough. it may be so thin that the interference fit wouldn't be enough to keep it in place; it might come out with the first tool that gets driven in too hard - I don't know, just thinking out loud.
4. Leave it as is. Being able to accurately hold stock in a draw collet makes it more functional than it was before, and I used it for years without being able to do even that. Any further action involves further risk and maybe it's best to just quit while I'm ahead.
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