Banjo Modification:
Chris Grace makes an improvement to his banjo and tailstock.
Chris Grace makes an improvement to his banjo and tailstock
Have you ever suffered a sticking banjo or tailstock, when it just won’t slide freely and you need to jiggle it or use two hands to move it? I have experienced this problem on several lathes. Sometimes it’s a minor irritation, and other times it can get quite annoying. When I get fed up with it I usually slide the offending item off, clean it, lube it and the lathe bed, and off we go with a nice smooth and freely positionable banjo and tailstock again.
The bolt that holds the banjo and tailstock on simply dangles down from the cam when loose, and is free to pendulum. When you suddenly move it, the plate at the bottom can catch on the underside of the lathe
bed causing a sudden increase in friction. This results in its inability to move smoothly. I have noticed this issue varies between different lathes, and most people simply use two hands and jiggle the offending
item into position.
In addition, particularly with my Hegner based demo lathe, I like to remove the banjo and tailstock to reduce weight for transport, therefore being able to slot both onto the bed in the middle would be a great advantage. So I was determined to kill two birds with one stone. On my lathe with box section bed bars, this was relatively easy, though my otherlathe with flat steel bedways was a little more of a challenge. My solution required a spacer that would slide between the bed bars, just under the banjo. I chose to use hard plastic – Corian, as I had some in my workshop. This would keep the securing bolt perpendicular to the lathe bed at all times if a strong spring is placed between it and the metal clamp plate that presses against the bottom of the bed bars. I slipped the spring over the securing bolt and replaced the bottom plate with one that would slip between the bed bars widthways, but be long enough to clamp securely when turned through 90°. The friction of the spring stops the clamp plate rotating when you have positioned it where you want it.
That solution is fine where there is plenty of room, such as on my lathe with square tube steel bed bars. However, on my lathe with flat solid steel bedways there isn’t enough room for the plastic and spring, so another solution was required. For this lathe I ended up using two small springs with a ball bearing on top, and mounted them in the bottom metal plate. A large washer gives the springs something to push against, and it seems to work just as well as the single spring method. The same principle was applied to my tailstocks.
Plans and Equipment
Equipment and materials used
• Saw
• Digital calliper
• Centre punch (I used an optical punch)
• Hammer
• Drill press
• Drill bits
• A piece of steel that slips between your bed bars
• A piece of hard plastic that slips between your bed bars (I used Corian)
• Springs
• Ball bearings (if necessary)
• Large washer (if necessary)
Handy hints
1. Digital callipers are extremely useful in any workshop, they can be used as a depth gauge, you can lock them to transfer measurements, switch between inches and milimetres, the points can scribe lines, etc. They are very accurate
1. Having selected a piece of Corian that was about the right size, I carefully measured from the edge of the blade to the end of the plastic with digital callipers and clamped it down to cut it to size. If you are careful you can easily achieve an accuracy of better than half a millimetre which is sufficient for this application. Just ensure the plastic is long enough to extend a little beyond the sides of your banjo so that it still touches it when you angle the banjo. I cut a similar sized piece of steel, though not with my chop saw
2. To make it easier to see scribed marks some people use engineer’s blue, a dye, however a black marker works just as well and is less messy
3. I often use an old engineer’s square and digital callipers to mark up pieces of a project accurately. Here I have simply divided the cut width into two to find the centre for the bolt hole
4. It is essential that the hole is drilled as accurately as possible, so I use an optical centre punch to get a good starting mark. This magnifies your view of the marks and you simply have to align the black cross hairs with your marks
5. Remove the acrylic stick and replace it with your punch while holding it still. A quick tap with the hammer provides you with an accurately positioned centre punch
6. Here you can see the punched mark has been positioned extremely accurately
7. Now it’s important to drill it accurately. I hold small things in a vice that can be clamped down for safety. Corian drills easily and you can create a 12mm hole in one pass. For the steel you may need to drill a pilot hole
8. If there are any rough edges on the Corian or steel, or if your blocks don’t slide easily enough between your bed bars, you can ease the fit with a quick rub on your disc sander. As a disc sander abrades more quickly at its periphery than nearer the middle, sometimes it helps to flip the work over to even this effect out and avoid an unintended taper
9. Here you can see the hard plastic, spring and new metal clamp plate. The spring provides sufficient friction so that the plate stays where you put it. If you are happy sliding your banjo on from the end of the bed you can re-use your existing clamp plate
10. An underneath shot shows you don’t need to be completely accurate when turning the clamp plate, it just needs to be under the bed bars, it will clamp happily at any angle near 90°
Handy hints
2. Engineers have used all sorts of tools to enable them to accurately mark and cut metal for years, so online engineering suppliers are a great source of relatively inexpensive tools that can make your life so much easier
3. When drilling small pieces of metal always use a vice. If you clamp it down you can change from a pilot drill to the finished size and be sure you are still drilling straight and accurately
11. The alternative method uses smaller springs and 8mm ball bearings set into holes drilled into the metal clamp plate. I used two opposing springs to ensure the plate would be level (otherwise it may not be smooth which is, after all, the whole objective). I also drilled two pairs of small recesses in the plastic at 90° to each other to hold the plate where you position it
12. Here you can see the large washer the springs press against, the metal clamping plate is held to it with double-sided tape, after all, when it’s in position gravity will help. You just need to keep them together while you’re slipping it in and out. This is in the open position, so it can be attached to the lathe
13. Now the clamping plate has been swung into its clamping position and the cam closed
14. Line up both the plastic and clamp plate at 90° to the banjo, and they happily slip in between your bed bars
15. All that’s left to do is to pop your fingers underneath and swing the metal clamp plate through 90° and you will hear the ball bearings click into their drilled recesses
16. The banjo now slides very freely and can easily be moved with one hand quickly to whereever you need it
17. I have used the same principle to modify my tailstock. My Hegner based demonstration lathe has a spacer between the bed bars preventing me from sliding the tailstock or banjo off the end. So this modification means they can now be slipped into place anywhere along the bed. This enables me to remove both the banjo and tailstock to make the lathe lighter for transportation
18. However, on my Wivamac tailstock there was no flat surface for the plastic to rest against, so I kept it level by adding four bolts that would rest against the recessed casting. This works just as well as on the banjo and I can now lift the tailstock off wherever it is convenient for me
Handy hints
4. Don’t just accept it if your equipment doesn’t perform how you think it should, investigate the cause and see if you can make any improvement that will make your life easier
This was a long overdue, and very worthwhile modification, which I have now done to all my lathes. It speeds things up when I am changing configurations or adding large jigs to the lathe bed
1 Comment
Hi Chris
Thanks for this.
I recently purchased a used Hegner HDB 200 XL lathe; on the whole I’m very pleased with it.
But one major niggle is that getting the tool rest close to a smallish spindle is a pain – I have to get the rest and banjo at a fairly acute angle to the bed which is fiddly.
I have looked at possibly a replacement banjo, but everything I look at – unlike the Hegner – has the clamping mechanism built into the banjo itself – above the bed – rather than underneath.
Could you tell me what banjo you use on your Hegner please, as it doesn’t look like the Hegner one?
Kind regards
Jonathan