Grinding Tailstock Internal Taper

mathamattox · Jul 20, 2021

Guys,

The MT3 taper in my tailstock ram is pretty boogered up. I attempted hand reaming and got a little bit of cleanup but nowhere near what I would call acceptable. The reaming mostly just removed the high spots but the gouges still remain. I am skeptical if power reaming would do much better.

I could chuck the ram and try to clean it up using the taper attachment on the lathe, but I honestly don't know if my skills are good enough to get it right.

So, I called around to a few places that advertise "spindle grinding" and most said they could do it. The way they apparently work is you ship your spindle to them, they inspect it and give you a quote to fix it. That seems a bit too "in-depth" for this issue. I was given a verbal quote from one of the places of about $300. That's more than I want to spend but I suppose nobody does a lot of internal MT grinding on spindles so it doesn't seem outrageous.

Anybody know of a small shop that has this capability that might be interested? The part is easy to ship so proximity is not that important.

Thanks,

Jonathan

Milland · Jul 20, 2021

This is a bit sketchy, but you could use a good (tangless) reamer or similar with the right sized Morse taper on it as an ad hoc lap.

Hold the reamer past the flutes in a chuck, and CAREFULLY true it such that the M-taper is properly concentric. Then bond a few narrow strips of ~320 Wet or Dry to the taper with Superglue, and at low speed run the "lap" into the spindle taper.

Do this a number of times, changing out the paper (and carefully cleaning off the reamer taper before attaching the new strips), and you'll get a useable bore. It won't be perfect, especially if you're not patient or careful enough in your setup, but it should be workable and cheap.

At worst, you've wasted a little time and have to still send the spindle out. But with care you can get a decent renewed taper. Just clean everything thoroughly when you're done, including the tailstock spindle threads.

michiganbuck · Jul 20, 2021

I agree with Milland Post #2
Also, you could take a cutoff tang and charge it with a lapping compound and hand crank it back and forth.
also. you might turn a good taper between Centers, run a saw cut down lengthways and with automotive wet paper stuck in the sawcut hand lap the tail taper bore.(with it having centers you can tickle it and make it new again)

The taper needs to hold a taper shank tool, drill chuck or center..it really doesn't have to be pretty.

Gordon Heaton · Jul 20, 2021

The gouges shouldn't be a problem unless they are huge. If you try to remove them you'll end up with a socket that everything goes way too deep into. It doesn't take much material removal on a Morse taper to greatly change the seating depth.

sfriedberg · Jul 20, 2021

Other thing is, you don't need a perfectly gouge-less bore. If there are no high spots, and the ungouged portion of the surface makes good contact, that's going to work just fine for a tailstock. (I am assuming these are narrow gouge marks, not scraping up a contiguous 20% of the circumference!) In fact, given a choice between removing some 0.002" deep gouge and leaving it alone, I would definitely leave it alone if the remaining original surface makes good contact.

[Added in edit] Gordon beat me to it.

TGTool · Jul 20, 2021

I had an MT reamer experience and education recently. I've had this MT3 reamer for years and don't remember where I bought it from so can't ding them. On the job I'd set the compound about right to clear out the bulk of the material figuring just a few thousandth with the reamer was about right. The work is in the chuck, the reamer is in the tailstock, spindle speed is slow, and I couldn't get the reamer to cut a chip for lover or money. Okay, I didn't put a cheater bar on the tailstock handwheel, but short of that.

Getting out a magnifier and looking carefully at the reamer I realized they produced it by cylindrical grinding, then just putting the clearance on with the T&C grinder. Only thing was, they left about .030 for a land as they came up to the cutting edge and it was no wonder it balked at taking any kind of bite. I stoned enough off the back sides to make it workable, but it's not first class.

So if your reamer might have come from the same guy, it's no wonder it won't do any work for you.

mathamattox · Jul 20, 2021

Thanks for the replies so far.

I agree that totally removing the gouges is not necessary. A blue check with a good MT3 shank right now is showing only a few very narrow rings of contact. The shank does not have the correct seating "feel" like a good taper to taper fit should.

I may attempt chucking the reamer I have in the headstock and feeding the tailstock ram into it. But as mentioned I am wary of removing much material and having the taper end up too "deep" in the ram.

Richard King · Jul 20, 2021

I would not chuck the reamer up unless you know the centers are aligned. If the TS is low and pointing down your screwing yourself making the hole oblong. I have done this before and it worked. Move the saddle close to the chuck, screw the chuck closed, wet the reamer with some cutting oil, put the reamer in the tailstock and press the flat to the end of the reamer lightly against the chuck, Do not turn on the spindle. Then use an end wrench or a Crescent wrench. Turn the reamer with the wrench and apply pressure with the tailstock screw. Turn it 2 times and take it out and blow out the hole, inspect it and repeat.

sfriedberg · Jul 20, 2021

TGTool said:
I realized they produced it by cylindrical grinding, then just putting the clearance on with the T&C grinder. Only thing was, they left about .030 for a land as they came up to the cutting edge and it was no wonder it balked at taking any kind of bite.

I had a similar experience back in the early '90s. I had sent an MT3 reamer out for resharpening, and when I got it back, it would not cut. I had to send it back to the sharpeners (no charge) and tell them exactly what land and clearance angles I expected.

michiganbuck · Jul 20, 2021

I used to make precision reamers and a trick I used was to back circle grind the last .001 to size. by doing that there would be a few millionths of radial relief on the circle grind margin. it took a needlepoint indicator point to even find it. It was the result of the tiny amount of give there is in all grinding machines caused by forces. Yes, it would be greater on straight flute reamers but still evident on spiral flutes.
Diamond lapping to size I also ran back into the edge, but the effect was less than with grinding.

Video_Man · Jul 20, 2021

I once cleaned up an MT3 tailstock center with the proper reamer, followed by polishing with a brake cylinder hone...the articulated kind with three very fine stones. Stones followed the taper nicely, bridged the small irregular spots left, and did a nice job. FWIW.

john.k · Jul 20, 2021

I know from experience that tailstock barrels sent out for grinding will come back with the taper set back far too deep.....on account of the fact it will take the grinder several goes to get it right to blued gauge......And ,yes,I have stuffed them up myself in exactly this way........one in four will be spot on first grind,and you can pretend you are a genius ,the other three,well ,you did get paid in advance ,didnt you?

Milland · Jul 21, 2021

john.k said:
one in four will be spot on first grind,and you can pretend you are a genius ,the other three,well ,you did get paid in advance ,didnt you?

Wait, you're supposed to get paid in advance?!

Why didn't someone tell me this earlier!!

eKretz · Jul 21, 2021

Doesn't matter if they're a tiny bit too deep after grinding the taper, just grind some off the face until the gage line is correct again. Might need to shorten the ejector pin if it kicks too early. (If the machine has one). I would be very wary of using a reamer piloted in by a center held in the headstock if the tailstock had any wear. In such a case you would almost certainly be better off seating the reamer in the tailstock and just giving it a couple gentle turns with a tap wrench. Best case scenario would be a regrind though.

michiganbuck · Jul 21, 2021

If the tail spindle was out of the tailstock assembly a local ID grinding shop might grind it.

Qtop:[given a verbal quote from one of the places of about $300. ]

It's kind of a tricky job but 3 hours(?)but yes with the tube in the tail that makes it more difficult.

No, I don't want the job, I don't even have an ID grinder.

Screwmachine · Jul 21, 2021

mathamattox said:
Guys,

The MT3 taper in my tailstock ram is pretty boogered up. I attempted hand reaming and got a little bit of cleanup but nowhere near what I would call acceptable. The reaming mostly just removed the high spots but the gouges still remain. I am skeptical if power reaming would do much better.

How hard was it to turn the reamer? In a MT3 it should be a fair bit of effort for a 6 foot machinist to get 1 turn on it, and harder for the 2nd and 3rd. Like break a sweat hard. To get the reamer to drift on 3 turns is next to impossible, and 3 turns should knock off enough high spots that I doubt you'd still be thinking about grinding. I've cleaned up MT3 tapers that were ugly as hell and ended up with awesome contact and holding power, but blueing still showed a lot of mankiness.

mathamattox · Jul 21, 2021

I bought a set of reamers, rough and finish, but they are cheap reamers from China just to see if they would work. If I need USA reamers to make further progress then I would just have it ground because the costs of the reamer.

rke[pler · Jul 21, 2021

Sure sounds to me that your taper is likely too messed up to just cleanup with a reamer, and that grinding it should to take too much out if there's tang support in the back of the quill. .001" on the bore is .007" on the taper depth so it's way easy to set a tool back until the the back of the taper hits the tang stops. If that's the case you're likely going to have to hard chrome the bore then have it ground back to taper with a gage. I had that with my 10EE tailstock some years ago and never found someone to do that work for less than I could just made a new quill, heck, I could have bought material for 100 quills for the prices I had been tossed as estimates.

michiganbuck · Jul 21, 2021

mathamattox said:
I bought a set of reamers, rough and finish, but they are cheap reamers from China just to see if they would work. If I need USA reamers to make further progress then I would just have it ground because the costs of the reamer.

Running in a taper charge with compound and hand-turned will make a fair repair, pushing against the cuck as Richard mentioned. using a number or scrap tang tool will keep it at a good taper. IMHO, when it makes a good lock on a taper that is good.

Agree the repair tool should be a little longer than an actual taper to go past the small end length

Likely the original meat of the taper has not been hurt very much so taking .005 of the original may make it look good/ok.

Grinding Tailstock Internal Taper

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