Lathe Spindle Handle for a Myford ML10

A Lathe Spindle Handle is a cranked handle which enables the lathe chuck to be turned by hand. It is slid into the hollow end of the spindle and clamped in place by turning a central knob.

It is particularly useful when cutting threads on a lathe using a tap or die held in a holder placed in the tailstock. It is used whenever a very slow, controlled, rotation is needed. It should never be used under power.

Alternative names are: Mandrel handle, Threading handle.

There is not much new in my design - there are many other examples available online. However, I was quite pleased with the use of a large coach bolt as the axle for the wooden handle - the domed-end looks very neat and the threaded fixing method is very rigid. Also, the large aluminium knob works very well (mainly by luck) because when using the device, it does not need any tools (like a spanner or allen key). Also, when releasing the device, the knob is big enough to hit with the heel of your hand to release the wedge - again, no tool is needed.

This Instructable shows the basic design idea which was governed by the materials I had to hand! The main elements are in mild steel. The Instructable steps are in the same order as I made it:

The main mandrel
The wedge
The knob
The crank
The axle for the handle
The wooden handle

It was pretty simple to make. I'm still a real novice on the lathe and there was little precision in the manufacture, but the end result is very useful.

Step 1: Main Mandrel

The photos show the process.

• Cut the bar to rough length.
• Turn the main outer diameter and check to see that it slides snugly into the lathe spindle
• Drill out the central hole (6mm) from one end as deep as possible.
• Enlarge the central hole by drilling out to 10mm diameter - for about 40mm depth
• Flip the bar in the chuck and drill a 6mm hole to meet up with the one from the other end (hopefully).
• Form a shoulder on the unworked end of the bar (this shoulder must fit through the hole in the changewheel guard).
• Turn down the top end of the bar, ready to accept an M12 thread.
• Cut the M12 thread (I used a die).
• Cut four slots to permit the mandrel to expand (I simply used a hacksaw, having no other method).

I considered cross-drilling two through-holes at the tips of the slots (before cutting the slots). Other ones I saw on line had done this (so the slots ended with a hole). This looks good, and would be essential to stop cracks propagating from the slots in some applications. Here, I don't think it is necessary, and because I have had difficulty cross-drilling on my bench drill (the bit wanders and never seems to go across a diameter properly) I thought it best to give this a miss!

Step 2: The Wedge

• Centre-drill, drill and tap M6.
• Turn down 10mm of length to a diameter of 10mm (this will just fit inside the mandrel).
• Adjust the angle of the top-slide to 1 or 2 degrees (I lined it up by eye to give a very gentle slope). The angle did not seem critical to me because the mandrel is a close sliding fit inside the spindle without any expansion from the wedge; hence, the smallest increase in diameter due to the engagement of the wedge, is bound to clamp the mandrel very tightly against the spindle. I only needed to expand the diameter by a fraction of a millimetre to achieve a tight fit.
• To finish, I did a partial parting-off, then chamfered the sharp corner caused by the parting-off, then finished separating the job from the stock bar.

Step 3: The Knob

Simply made from some 25mm diameter aluminium and drilled/tapped M6 through most of its length.

I wanted to knurl it, but I don't yet have a knurler so I cut a short length of bicycle inner-tube which fitted nicely around the circumference. This makes it easier to grip, especially with oily fingers.

Step 4: The Crank

Made from a scrap piece of mild steel rectangular bar - rather too substantial for the task!

• It was a devil to bend in a vice (I used G-clamps to fit a 1m length of 50mm square wood onto the bar - this gave me enough leverage).
• I had a rough drawing of what shape I wanted (so it would not hit any bits of the lathe, or its stand). I cut this out as a paper template, to help me make the correct bends and final shape. The drawing also let me know how long the original piece of bar had to be (23cm).
• Once the bending had been done, I used my bench-drill to make two holes (one 12mm diameter for the mandrel, the other 7mm - ready to be tapped out to M8).
• The final step was the tapping of the hole ready for the wooden handle axle.

Step 5: The Axle for the Wooden Handle

Made from a coach-bolt.

• The end was turned down to the diameter to suit an M8 thread, and then parted off.
• The thread was cut with an M8 die. Fortunately, my lathe chuck enabled the bolt-head to be inside the chuck without affecting the grip of the jaws. This let me thread the end on the lathe (rather than having to hold the bolt in a vice for threading).
• The square section under the head of the bolt was removed to leave a smooth axle.

Step 6: The Wooden Handle

Made from an old bit of curtain pole.

• The diameter (on the right hand side in the photos) was made to match the diameter of the coach-bolt which was to form the handle axle.
• A clearance hole was drilled through the middle, so the axle could rotate freely.

Step 7: Final Assembly

• I spray-painted the crank, matt black.
• I couldn't find a suitable lock-washer to under the main M12 bolt, so I used some thread-locking liquid.
• The wooden handle axle was screwed into the crank and a locking nut was screwed on the back.
• The thread-locking liquid was also used to stop the M6 threaded-rod from unscrewing out of the wedge.

The spindle-handle works well.

Comments

[stewpot_em89]

Hi Quentin. Re: your problems drill cross holes in round bars, have you got one of these (two way swivel milling attachment)? Extremely useful for a myriad of small mill / drill jobs. There are plenty of metric ones on the Net for £120ish + vise. I paid £240 for mine (inc. vise) direct from Myford because (to match my machine) it's Imperial, it's green and it's got Myford on it. Regards, Stuart

[qthurtle]

Thanks for that. I do have a milling attachment and vice, which I have used for this. The one hassle is the effort needed to set it all up. By the time I've removed the tool-post, bolted on the milling attachment, fitted on the vice and got everything aligned, I'm fit to drop.

I'm guessing that this comment is in response to my Instructable "3d Printed Lathe Toolpost Drill for Myford ML10". The 3d printed add-on described there, is no substitute for your suggestion which is a much better way to get accurately placed holes!

[stewpot_em89]

I agree about setting up the milling attachment - for a one-off job it's a lot of work, for a "production" job i.e. where you're making a batch of components it's worth it. However, I'm getting better at it the more I use it so the set-up time is coming down. I attach a photo of me milling a 14mm square on a bar which one day (I hope) will be a lathe spindle handle based on your design. The double swivel attachment is a good piece of kit but, to allow for the extra plane, it does look huge on an ML10, probably less so on an M7. Consequently you can only take very light cuts before vibration kicks in. As 99% of jobs are either vertical of horizontal the plain vertical slide would cater for most jobs and be easier to set up. Stuart

[madguernseyboy]

I have made one of these. It’s great! But I find it slips in the head stock :(
Any ideas?

[qthurtle]

Hmm. I have not had any problems with mine. Obviously, make sure the business end is wiped dry of oil. I'm guessing that the angle of taper will affect the outward clamping force, but this will already have been set when you made it. I have put some bicycle inner tube around the tightening knob so that I can make sure it is well tightened ( it then needs a good bang with a rubber mallet to release the grip after it has been in use).

If it is not really usable, perhaps put some saw cuts around the circumference of the part which grips the spindle when it expands (saw cuts parallel to the main axis of the lathe - ie at right angles to the slipping motion). This might be a bit drastic, but it should help by giving some sharp edges to help grip, and by reducing the surface area which is in contact with the spindle, hence increasing the outward force applied to the spindle.

I suppose making the outer surface of the tapered plug (the plug which is pulled into the assembly to produce the force) as smooth as possible, will enable it to slip more easily into the assembly and hence produce a bigger clamping force. Likewise, making sure that the bore it slides into is as smooth as possible will also help. Perhaps attack these areas with progressively finer sandpaper (perhaps up to 1000 or 4000) followed by a polish with metal polish (etc).

Let us know how you get on.

[MES73]

The 12mm hole in the handle where the shaft fastens needs to be threaded to prevent the handle from slipping around the shaft so that the nut locks it. I drilled it through the handle and into the shaft and put a small pin pin through it.
The nut was then replaced with a washer and this prevented it from turning. The handle is great and works well clearances are fine for my ageing ML10 Lathe, I fitted a "frog" cycle light to the handle which has a flashing light mode so I don't accidentally leave the handle in and switch the lathe on.

[qthurtle]

Nice. I like the idea of the light. I have not yet switched on the lathe with the handle in place, but at the start, I had some near misses. I now ALWAYS slip the drive belt off the pulleys whenever I use the handle - this has saved me on one or two occasions!

[ke1th]

Excellent description! I'm just about to make one of these for my own ML10, and thought I'd share this easy tip for successful cross-drilling of round bar which I was given about 40 years ago. Step 1 - put a short rod (about half an inch will do) of the same diameter of round bar into the lathe chuck Step 2 - using a pilot drill bit in the tailstock drill through the centre of the rod to form a guide cylinder. Step 3 - using the jaws of your drill press vice, or bench vice, tighten the jaws to clamp the guide cylinder at right angles to the main rod to be drilled Step 4 - pass the same pilot drill bit through the hole in the guide cylinder and drill into the surface of the main round bar. The clamping action of the vice jaws will prevent any movement of the drill bit on the surface of the bar, and you are guaranteed to be on the exact diameter as by drilling the pilot in the lathe the hole will be in the exact centre. You can vary this technique to make guide cylinders for drilling off-centre holes too.

[sw.machinist]

Great idea!! Sure beats turning the chuck with your hand!

[jessyratfink]

Perfect documentation and a really nice looking handle - great work! :D

[qthurtle]

Thanks for your kind comments!