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?

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.