Dualling banjos

[BobL]

The is really a metal working project but I though wood turners might like to see a second banjo I made for my Woodfast lathe.

The reason I wanted a second banjo is like Derek Cohen I eventually want to make a 600 mm long, two legged, tool rest.

The banjo body (blue bit) is made from a length of 40 x 40 x 3 mm SHS, from which a 25 mm wide slot is cut along its full length - that slot is underneath the body.

The banjo body end caps are made from pieces of 10 mm thick steel plate and shaped to fit inside the SHS. A 15.5 mm hole is then drilled in the middle of the caps. The front cap was welded in place and the rear cap is removable and held in place using 3/16" CS socket screws.

The long cam that locks the banjo in place and rides down the middle of the banjo body is made from 18 mm diameter steel and has 15.5 mm steps at each end, turned 2.5mm off centre to act as a cam.

The handle is at one end of the cam and was turned down and to shape and the bent after heating the middle of the reduced section with a MAPP torch

The tool post support component is made from 32 mm diameter teel rod and is welded to the body of the banjo.
Welding the support post 90º to the lathe bed was tricky and I got it to 89.95º. It's not that critical because the two poster tool post is going to be adjustable so that the top of the post can easily be made to be level with the lathe bed.

The tool post locking handle is just a temporary thing till I work out what to use. If it works out OK I may not change it.


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[bueller]

Thanks for sharing mate! I’ll be trying to copy this at some point, the current version of the Vicmarc banjo uses a different shaft size to my old one so their two posted tool rests won’t fit. Will have to have a good squiz next time I’m around!

[artful bodger]

Nice job Bob.
When I bought my woodfast lathe it actually came with 2 banjos. I think because I ordered the outside turning attachment with it. Anyway, any longer bed woodlathe worth it's salt deserves 2 banjos and a long tool rest.
I made a pattern for my big lathe's banjo and got another one cast. Well worth the effort.

[rob streeper]

Thanks Bob,

Can we see a shot of the mechanism inside the banjo?

[BobL]

Thanks Bob,

Can we see a shot of the mechanism inside the banjo?

Sure - I have to take it apart to paint it anyway.

[BobL]

As requested above.

The cam locking arm, starts out as a 300 mm long x 18mm diameter BMS Rod.

The rod is placed into a 4 (independent) jawed lathe chuck with one pair of opposite jaws offset from the centre of the rod by 1.25 mm.
When section B, and then section A (plus the handle) are turned down t0 15.5mm this effectively turns the long section between A and B into a long cam shaft
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Here's a close up of the step that shows the 2.5 mm cam lobe.
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The photo below shows all the parts.

The handle is turned down further to about 13.5 mm so it is narrow enough to fit through the hole (following the path of the red arrow.) in the end of main body of the banjo.
A reduced section is turned into the handle which enables the handle to "go through the hole and turn around the corner and facilitates the creation of a reasonably tight bend in the handle when heated heated with a MAPP. torch. The bend is made before insertion into the hole.

In the photo below, part A is a piece of 25 mm BMS rod with an 18 mm hole in it and a short section of 10 mm threaded rod welded at right angles in the middle.
After the handle has been put through the hole in the end of the banjo body, Part A is then slid onto the long cam (see picture below)

Part B is the end cap that is used to support the short stub at the end of the cam lobe and held in place to the banjo body with 3, SS CS screws (D)
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This shows part A above slid onto the long cam.
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Part C is placed onto the threaded rod after the banjo has been placed on the lathe bed so the threaded rod pokes through the gap in the lathe bed.
Here you can also see the banjo body end cap in place.
Turning the handle now lifts/lowers the threaded rod locking the banjo to the lathe bed.
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Ready to rock 'n roll - works just like the bought one
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If I was doing this for a bigger lathe, or more HD work than this banjo will be exposed to, I would have placed some phosphor bronze bearings at each end of the long cam.

[Skew ChiDAMN!!]

Nice bit of machining and it certainly looks good, Bob... plus it'd fit my girl nicely. ;) Going to throw a splash of MF Yellow over it?

I haven't had much luck with those tool post locking handles. They're alright on midi-lathes but I've found that when roughing larger, lumpier pieces they tend to loosen during a job. Repeatedly. Which means retightening... and retightening... and retightening... until out of frustration I overtighten and eventually either the handle gives way and snaps or the engagement becomes ridiculously sloppy to use henceforth.

I've tried a few of the metal versions but they seem to have the same general failings, although they do last longer before they become 'Skewed.' :blush:

Right now I'm favouring just welding 1/4" rod as a T-handle across the end of a suitable bolt. I did grind a bit of a bevel on the end of the bolt, that contacts the tool rest, to minimise contact area/increase holding pressure so that may be more of a factor than the handle itself.

It certainly doesn't look as nice, though.

[BobL]

Cheers SCD, I agree its a light weight mechanism for a small lathe. The problem with log rod cams is that they are liable to bend and so ease up on teh tension
The one concession I made to increase the strength a little was to use 18 mm rod instead of the 5/8 that's on the original banjo.

One of the neatest solutions I saw on a home made lathe used a length of 50 x 50 x 5mm as the banjo body and a 12mm slot cut longwise for a 12mm bolt that passed through a 40 x 40 x 10 mm washer that slid up and down inside the banjo body and then a similar washer underneath the lathe bed. The locking nut was on a cam with a long handle and could be tightened to go "over centre". These "over centre" cams are much harder to undo than straight cams . I use them on my 8HP Chain Saw mill which is a vibration monster but has never undone one of these cam bolts.
The cam pressure washer in this mock up photo is white plastic but eventually it was changed for a steel washer.

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