Sanding Steel - What thickness can be removed?

I have:

- a Quorn grinding machine with a Ø1" tool holder (actually Ø0.992" id).

- a number of inserts for the toolholder to take square tools.

- the tool holder does not (yet) accommodate ER20 MT2 nor ER11 MT1 adaptors.

- an adaptor Ø1" to MT1; and Ø1" to MT2. These allow their respective collets to be used for sharpening drills.

So far so good.

- The two Ø1" od adaptors do not fit into the Ø0.992" id tool holder. Their radii need to be reduced by Ø0.004" each.

Problem: I am having difficulty in centring these with sufficient precision on my small lathe. Headstock end (4 jaw) better than tailstock end.

Question: If I use sandpaper / wet&dry / micro finishing film / lapping film etc - will I be able to reduce the diameter over a reasonably shortish time? Or will it take forever? What are the perceived "cutting rates" for a given grade of paper?

Four thou is quite a lot to take off with abrasive, and enough to lose concentricity/roundness unless you are lucky.

Perseverance with the lathe may end up being quicker and more accurate.

Perhaps bore out the toolholder to 1" instead?

Neil

Mount a lump of steel bar into your 3-jaw, turn to a MT2 taper and fit the first adaptor to that so OD can be turned. Then remove and reduce the taper to MT 1 so you can do the other.

The problem with sanding that much will be keeping the OD round and parallel.

I agree with Neil. It would be much quicker to bore out the toolholder. It could be done quite quickly using a Dremel grinder or similar attached to the toolpost. Have a look at some of the video's Xynudu has up on Youtube for some ideas.

regards

Take a bit of MS bar and chuck it in the lathe, face the end and drill/tap say M6 or similar. Now turn a taper on the bar to match the adapter you want to turn down - say MT2. Get it to fit as good as you can, possibly using wet and dry to get the last bit off.

DO NOT REMOVE FROM THE CHUCK!

Now take the MT2 adapter and fit it on the taper, using the tapped hole with a bolt and washer to clamp it in place. The taper will be concentric (as long as you don't remove it), so the adapter should be too. Now you should be able to take a skim with a VERY sharp tool though you only need to take a smidgen off.

I have a double ended MT2 taper that I made so that I could finish the OD of a spindle concentric with an existing taper socket - one end goes in the headstock taper with a drawbar, the other took the spindle. Worked fine.

Thanks for all your helpful suggestions.

It sounds as though using an abrasive is a risky and tedious route, so I won't be attempting this.

The idea of grinding the inside of the toolholder is sound. However I already have fittings which fit snugly inside the toolholder and I wouldn't want these to have a looser fit.

The adapter is currently held in the chuck by a bar inserted inside an ER20 collet fitted into the MT2 adapter. I thought this would be centred well enough. It clearly isn't.

So I think I will go with the other good suggestions from John and Jason and start by creating a MT2 tapered bar in the chuck and using that.

If your headstock taper is 2MT I could lend you my double-ended arbor - it isn't exactly in constant use!

Send me a PM if interested.

John,

How extremely kind of you, but sadly my headstock taper is MT1.

Best wishes, Anthony