Thread: Grinding a Hardened Tailstock Bore

Couldn't you have fitted a bung inside the pipe that had a centre in it.
Two chucks are great for holding heavy work like over a tonne that can't be supported properly by a centre.
Also for odd shaped eccentric shafts.
Guess if you have the time it's another way of doing it.

I have been wanting to make one myself for a long time now, but just cant bring myself to pay $100 odd dollars for a 125mm chuck that I want to use. I will used a 4 jaw as it will only be an occasional use and will need the accuracy and not the speed.

There have been a few turning jobs where it would have come in handy for me.

Dave

Hi Bryan

Yes, the chuck is 3 jaw. The bearing and backplate is interference fits. I tried it today and very happy with it. The centre steady on the ML7 is not that big. I guess once I clamp at both ends then lock the tailstock then its quite safe to operate.


Thanks on the bung idea Clubman7.

Hi DaveJ, the bearing is double roller bearing so its quite good.

Well the more I thought about it the more I got the wind up about getting the grinder set up accurately enough.
Call me chicken but I decided to have a play with some abrasive paper on a mandrel, as suggested by RC.
I will let the pictures do most of the talking.

Before. I had actually done a little work at this point. But the offending ridge can be clearly seen.



280 grit paper trimmed to fit mandrel. (I know Bob will love my drive dog.)



I tried it by hand first but that got old. This is 400 rpm, as fast as I dared.

[ame=http://www.youtube.com/watch?v=pTxhApgcT7A&feature=youtube]tailstockrepair - YouTube[/ame]

At first I had a centre in the chuck locating the mandrel, but later switched to a flat pad so it could float.

After wearing out half a dozen bits of paper. The taper on the right is virginal so should be correct.



Here's a before & after looking up the spout.




So I'm calling that fixed. Thanks everyone for the input, and especially to MichaelG for the loan of the TPG and Garry Edwards for the reamer.
I will get both those items returned asap.

Very nice work there...Looks good...

Nice dog Bryan,

Sure beats the cast iron versions I have with their nasty hardened set screws. And sure beats fooling around with bits of shim trying to prevent those screws from gouging a nicely turned surface. I need to make a copy.

BT

Chicken... though I cant say I blame you. The spindle in my mill could use some work but I'm putting that off.
What made the paper turn with the mandrel?
How did you do the bluing? Shouldnt you blue the taper then drive the arbor in with a soft hammer?
I like the flat pad idea.

Stuart

Originally Posted by Anorak Bob

Sure beats the cast iron versions I have with their nasty hardened set screws. And sure beats fooling around with bits of shim trying to prevent those screws from gouging a nicely turned surface. I need to make a copy.

Bob, I was referring to the junkyard finish. If you make a copy I'm sure it will be much nicer. Chrome bar is pretty slippery so I used a roll pin as a drive key. I ground a slight groove in the bar to engage it. I've never had much luck with those cast dogs.

Originally Posted by Stustoys

What made the paper turn with the mandrel?
How did you do the bluing? Shouldnt you blue the taper then drive the arbor in with a soft hammer?

Stuart, I'm not really sure why the paper turned but it consistently did, as long as I got each new piece started gently by hand. That seemed to give it the right idea. I used diesel as a lubricant but it got on both sides of the paper so I don't think that made any difference.

I blued the socket with this precision instrument. Could have used a bit more length.



... then inserted the taper. Tried tapping it in and tried rubbing around. Didn't seem to make much difference.

Good one Bryan.

Michael

Originally Posted by Bryan

Well the more I thought about it the more I got the wind up about getting the grinder set up accurately enough.
Call me chicken but I decided to have a play with some abrasive paper on a mandrel, as suggested by RC.
I will let the pictures do most of the talking.

Now that is a solution I like - and might just steal to help me restore my own tailstock from its own sorry state. Brilliant!

Originally Posted by Jekyll and Hyde

Now that is a solution I like - and might just steal to help me restore my own tailstock from its own sorry state. Brilliant!

Then for you or anyone else considering this method I will add a few details. I tried using a standard MT arbour but with paper around it the engagement was too short. So I needed to make an extra long one and for that I needed a gauge. I turned up a plug to suit my spindle (so it would be useful later), rough bored a MT4 socket and finish reamed it. The reamer (a quality one) gave me confidence the geometry was correct.

To turn the male taper I used the tailstock offset method because it gave me power feed and also I felt I had more control over the adjustments. After a few cycles of cut-blue-adjust I got it pretty good. One slight snag was that the mandrel was longer than the gauge socket - which was limited by the reamer - so I wasn't getting a reading on the small end. I just had to hope for the best.

The handwheel was used to apply pressure but was pretty insensitive. With a hand on the quill I found I could ride the backlash in the key and get a feel for how much torque was being gnereated. When I couldn't resist the torque I figured that was enough. The hand also told me how hot things were getting. I started with low speeds and worked up to 400 rpm. I figured high speed and light pressure was better, but that's just a hunch.

One good thing about this method is the removal rate is low. If you blue up every time you change paper (about every 30-60 seconds) you'll be in full control. That's why I changed to fully floating - because I saw I was losing contact on the bottom. With a floating mandrel I don't see any danger of altering the socket's alignment. Where the abrasive has a large contact area the removal rate will be much lower than where the contact area is small. So you will be removing the high spots first. That's my theory anyway.

Originally Posted by Bryan

With a floating mandrel I don't see any danger of altering the socket's alignment.

That was exactly the part that most appeals to me, not having to get a dead perfect alignment of headstock to tailstock! Thanks for the extra details too, I'll have to file it away in the box marked "Uses for spare roundtoits". I think the box takes up more space than my Bridgeport clone....