securing 6 MT sleeve in headstock - how hard to tap?

I'm a hobbyist so normally I post questions on a hobby maching forum but I figured the knoweledge base on this forum is much better for my question. My Summit 14 lathe has a 6 MT in the spindle. My question is how hard to tap the sleeve into the spindle?

Backstory - on my previous lathe, Clausing 5914 with a 4.5 MT, I made a 5C adapter and when I inserted the adapter to use it, I used the hand wheel to draw the adapter into the spindle. I made a 5C adapter for my current lathe, starting with a commercial 6 x 4 MT sleeve. I very gently tapped the sleeve into place, then machined/ground the sleeve into an adapter. Checking the run out its 10x+ more than I want it to be (now .005 in.). If I lightly tap the adapter with my lead hammer the run out is reduced to .002. I've adapted a Royal lever collet closer for this lathe instead of the handwheel on the previous lathe.

How hard should one tap on the adapter to seat it, since the load (impact from tapping) goes directly into the spindle bearings? I just don't have a feel for what is reasonable in this size of a taper. BTW, I inserted the adapter clocked the same way to the spindle as it was ground - not that that should matter.

Tapping harder isn't the solution to runout. I'd start by making sure you have everything clean, clean, clean. If that doesn't address the issue then I'd suggest looking to see if you have galling inside the spindle, look for burrs, etc.

If you are able to tap on the adapter and the runout changes, that means the two tapers are not the same. Did you try to "bluing" to see if the two tapers mate end to end? And are you sure you have a No. 6 MT spindle taper? Generally with D1 style spindles in larger ones, you have a ASA standard taper that is .750" TPF. It's listed in the Machinery's handbook.

4GSR said:

If you are able to tap on the adapter and the runout changes, that means the two tapers are not the same. Did you try to "bluing" to see if the two tapers mate end to end? And are you sure you have a No. 6 MT spindle taper? Generally with D1 style spindles in larger ones, you have a ASA standard taper that is .750" TPF. It's listed in the Machinery's handbook.

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Fair question - the manual says its a 6 MT. I will blue it and check to the spindle.

aribert said:

Fair question - the manual says its a 6 MT. I will blue it and check to the spindle.

Click to expand...

What country was the lathe made in? If Taiwan or China or other countries, I would not trust the manual saying it is a MT6. I have a 1970's vintage Taiwan made lathe. The manual says it is MT6 in the spindle. The "MT" means metric taper not morse taper. Metric taper 6 is close to morse taper 6 but not the same. So I had to buy an adapter to make it a MT4 taper. A MT6 center or anything else this size looks like it fits but not close enough to not have excessive run-out.

The manual also says the tail stock is morse taper 6 but it is really a morse taper 4.

The lesson learned is don't trust manuals written in foreign countries.

The taper on the adapter and the spindle bore both measure out to be 0.0516. I have serious doubts as to my skill at measuring a diameter on a taper - especially in the spindle bore (and I never expected to get the same taper number for both bore and arbor). That said, when blueing the arbor to bore I discovered lightly indented surface on the spindle lead in (was proud in the bore at the inboard surface of the lead in). I could not see/feel the damage by eye. As I began to rework the lead in, I found a second hit on the lead in. I am guessing that someone jammed a piece of stock thru the chuck and missed the spindle bore - hitting on the edge of the spindle lead in. I cleaned up the surface by making the lead in twice as wide.

I blued the arbor and looked for contact in the bore. I discovered that the adapter is tighter in the bore at the smaller diameter - the blueing is noticeable thinner on the small dia of the arbor.

Overall the adapter fits the spindle much better after reworking the spindle lead in. Using (4) 3/4 inch 5c collets and a 0.749 gage pin, the no name collet showed run out just under .001. The three Hardinge collets had run out of: 0.0005, negligible and negligible. I need to do the same check with a few other collet / gage pin combos.

Laverda - My Summit is Chinese (was a surprise to me after purchase) as I previously thought all Summits were of Eastern European mfg. I spent an hour looking for metric taper information - lots of info on taper pins. Found an ISO chart for pins up to 32mm - no idea if it scales up. My measured taper at 0.0516 (0.6197/ft) is less than a the taper specified for a 6 MT at 0.05213. I have no idea as to how much error there is in my measurments but I am content with the concentricity results after reworking the spindle lead in.

MT6 is .6257 taper per foot on dia. here

Standard Tapers

have fun