Mini-Lathe Mods

Tailtang Stop – Saddle Stop – Chuck Backstop

There are a number of modifications that you can make to your mini-lathe to provide worthwhile improvements. These are relatively straightforward to produce and most of the materials you will probably find in your scrap box. Oh yes, never throw away any offcuts or spoils. I have two small plastic storage containers under the bench, one for brass and the other for aluminium and stainless steel. They frequently provide a useful source of material.

I will try to add to this page as time goes on but to start with here are one or two items that I certainly wouldn’t like to be without.

Tailtang Stop

One of the problems I encountered when I first started using my lathe was the tendency of the drill chuck MT2 taper to rotate in the tailstock ram. This undesirable condition became more prevalent as I progressed to drilling larger diameter holes. The drill bit would grab and the rotating force of the headstock chuck would transfer to the  tailstock chuck. As you know the drill bit is not supposed to rotate.

If you haven’t experienced this undesired effect you soon will when you start using your lathe for drilling purposes.

Initially I thought it was a problem I would just have to live with until Bogs offered me a solution.

The chances are that your drill chuck is mounted on an MT2 taper (check your machine spec if unsure). You will need to buy an MT2 taper with a tang. This shouldn’t cost much more than £4 out of your pocket money. I took the opportunity to treat myself to a keyless chuck at the same time – the whole lot came to less than £20, try RDG Tools By buying an MT taper and chuck together you will be sure everything matches up.

Here’s what you do. Remove the ram and leadscrew from the tailstock.

Put each one in turn into the ram and mark on the taper how far it goes in.

Lay the tapers next to the ram and line up the depth marks, then mark on the ram the end points of each taper.

Find the spot midway between the two taper end marks for your drilling point. Avoid drilling too close to the control groove in the bottom of the ram. Ensure you drill square on to the centre line of the ram (remember the razor blade tip when setting up your cutter tip height ?).   Drill for an M4 tap (check your tapping chart, probably around 3.4mm in steel).

Now screw in the leadscrew past the hole you have drilled then screw in a grubscrew until it just touches the leadscrew. This will indicate how much you will need to grind off the end of the grubscrew with the socket (or screwdriver slot) end just below the surface.

When fitted the grubscrew should protrude just sufficiently to prevent the tanged taper from turning. Ensure the leadscrew isn’t fouled by the screw and that both sizes of taper are ejected.

Once happy that everything is in order the final stage is to put a drop of loctite on the outside edge of the grubscrew allowing it to dry before replacing the ram back in the tailstock. Should the grubscrew ever shear off just apply a little heat to release the adhesion and screw into the ram centre. Don’t try screwing out as the damaged thread on the grubscrew will foul up on your threaded hole.

Saddle Stop

Again I owe this one to Bogs. He had told me about this clever little device quite some while ago but I didn’t fully appreciate the benefits of it. But now I wouldn’t be without it. Basically it provides precise control over the length of repeat turning cuts.

Bogs’ C-o-C drawing shows the simple construction using a milling cutter. I have no doubt this device could be knocked up without the benefit of a mill. I made mine up from a piece of scrap 15mm aluminium plate. I also added a further adjustable stop which increase flexibility in use but maybe is not really essential.

Chuck backstop

This is a very useful gizmo which, when used in conjunction with the saddle stop, provides a reliable method of repeat turning of identical items. The ‘soft’ arbour is machined to be flush with the backplate when in position.

If you would like a larger copy of Bogs’ C-o-C drop me an email at john@start-model-engineering.co.uk