vevor 5 dividing head issue

[tatlerParticipant @tatler]

Can anyone help regarding the locking mechanism for the  5 ”  dividing head.

The spring that locks the sector arms is a waste of time.

 

has anyone else come across thois and any ideas how or what can be made to make this a bit more secure,

 

Also is it easy to make some sector arms from brass >

 

thanks in anticipation.

 

Joe

[Clive FosterParticipant @clivefoster55965]

Various You-Tube video reviews covering this dividing head which might have suggestions for improvements.

The Tubal Cain two part You-Tube covering both functional review and operation of the device might be good place to look for help as he is known to be reliable and honest about shortcomings along with ways to overcome them.

Clive

[PeteParticipant @pete41194]

It depends on what else you have available as far as how easy it is to make the sector fingers Joe. The boring could be done on a lathe or with a boring head and mill. The rest could range from just filing the shapes out, or milling them. Having a rotary table for the radial milling would be helpful for some of it. Impossible to say without knowing what else you have and how experienced you might be. Now if you had say something like CNC, EDM, Laser or Water Jet Cutting, my answer would be a bit different. 🙂

I don’t know anything about your dividing head, but what I have seen on a few YT videos, they don’t seem to be too concerned about incorrect or over sized machined features in lot of places. If it’s the part I’m thinking of, and at a guess, it almost sounds like the recess that slightly bent flat leaf spring slips into if I recall how it works correctly. That might have been cut over width for the springs thickness? Making a new one out of something like a short length of steel strapping used on larger shipping boxes might work? The bends position and just how much to bend it is a bit critical though. You really need to study and access what and where the issues are that are causing them. Figure that out and you should be able to come up with a logical way to fix it.

[Andy StopfordParticipant @andystopford50521]

I improved the spring clip with a bit of filing and judicious hammering – I assume it’s basically the same idea as was fitted to the Browne and Sharpe heads these are copied from.

The sector arms should be simple to make you just need to make sure they can be moved easily, but stay in place when not being moved, which brings me to a maddening problem with this design.

The handle to turn the worm gear also does duty as the housing for the plunger which engages the dividing plate holes. To advance the worm you pull the handle out, and give it a part turn to engage a bayonet type locking mechanism which holds it clear of the division plate. You then rotate the handle to the next hole position.

However, turning the handle tends to disengage the bayonet, the plunger pops out and, all too often, strikes a sector arm pushing it out of position. You then have to go back and try to work out where the sector arms had been, which is by no means obvious.

Sometime, I intend to make a new slide bar with a handle just for turning the worm, and reserve the plunger equipped one solely for indexing. Some dividing heads have this feature, and maybe the original B&S ones had a better locking mechanism for the plunger – the Vevor ones are pretty good for the money, but they are, I suppose, made down to a price.

[Dave HalfordParticipant @davehalford22513]

The easy answer is to keep the handle pulled out and mark each hole with a marker pen. You just need to be able to clamp the two arms together properly at what ever hole setting you need.

[BazyleParticipant @bazyle]

The OP seems to have a problem with movement of the sector arms, not needing to make them. It is not clear exactly what he has got on his particular setup but lets look at a the picture for a BS0 head fingers.

The left one fits over and rotates on a small spigot on the right one. The black screw is used to lock them relative to one another. Note the washer on the black screw which must overlap the top finger. This washer could do with being bigger and is crucial to the locking. The screw does go out the back and can lock the rotation of the assembly if the washer is not in place but it is not meant to. A replacement screw might be too long.
The spring clip can be bent for added friction but it is only meant to resist movement of the finger pair assembly between operations not to lock anything.

The correct procedure when advancing is to use two hands. After advancing the sector arm pair one thumb is used to hold the arm next to the plunger while the other hand is used to pull and move the plunger. On old industrial heads you can sometimes see the effect of bad practice where the operator  lands the plunger on the slope of the finger to let it slid down into place to avoid clunking against the arm and risking moving it.

Joseph Whitworth recognised that this procedure was too complicated for minimum wage production workers and arranged indexing systems that used enough gears such that one full turn of the control wheel advanced the spindle the correct amount. No counting and no care needed.

 

[BazyleParticipant @bazyle]

Re-read the first post and see he does want to make arms. Yes, brass is fine and looks nice or aluminium less pretty but both easy to work. 1/8 thick. The black screw is probably 1/8BSF (or UNF) but I haven’t measured it. Otherwise use a BA screw as you want a fine thread.
Of course you can also just 3D print an index plate that only has the holes you are using today.

arms https://www.thingiverse.com/thing:3812736

 

[Author]

Posts