Hi Mark,
My view on the use of the 'pointy probe' stylus in the wiggler set:
I was taught to set the point by running the wiggler at a reasonably fast speed and pushing the pointy stylus, using a steel rule, until it runs true (if you push the point past the centre of rotation it will suddenly flick out. This action will cause significant injury if you do this setting using your finger instead of a steel rule....)
Once centred, turn the machine off and align the point with the bed lines marking the required centre on the work.
Rather than use a wiggler, I use a 'sticky pin' to perform the same function - much more convenient and quicker to set up.
Your reference to centre pop marks cannot pass without comment.
I would advise against the use of a centre punch or attempting to mark the centre with a 'pop mark'. The centre punch is the work of the Devil and it is for the use of blacksmiths, not engineers. Consider the following:
You carefully mark out the desired centre with scribed lines to the required degree of accuracy. You know the centre is not perfectly marked (no measurement or marking is perfect, there will always be some error) but it is accurate enough for the task in hand. Now imagine re-enforcing the centre location with a punch - one of three things will happen.
1) You hit the punch and it creates a perfectly symmetrical crater exactly on the intersect of the scribed lines. When you drill the hole, the drill takes up perfectly on the centre pop mark and produces a hole exactly aligned with the scribed lines.
2) The centre pop is not perfectly aligned with the scribed lines and/or the crater produced is not perfectly symmetrical. When you drill the hole the asymmetry pushes the drill slightly to one side and this, combined with the imperfect alignment, by some amazing piece of luck exactly compensates for the error in the initial marking out and makes the location of the hole more accurate than the original position marked with the scribed lines.
3 ) The centre pop is not perfectly aligned with the scribed lines and/or the crater produced is not perfectly symmetrical. When you drill the hole the asymmetry pushes the drill slightly to one side and this, combined with the imperfect alignment, pushes the centre of the drilled hole away from its intended centre and results in a hole location that is less accurate than the original position marked with the scribed lines.
Let's be honest, condition 1) and condition 2) are not going to happen. If you centre punch a hole location you will always introduce errors which mean the centre punched hole is less accurately placed that the original marking (condition 3).
I would advise that where any degree of accuracy is required use a drill ground to a four facet point which will start directly on to scribed lines without the need for a centre punch mark.
All the best,
Ian
From: "mark.kimball2@frontier.com [GrizHFMinimill]" <GrizHFMinimill@yahoogroups.com>
To: GrizHFMinimill@yahoogroups.com
Sent: Thursday, 5 November 2015, 3:58
Subject: [GrizHFMinimill] Re: proper use of a wiggler
I go by the 'flies off the piece' method. It's my impression that the business end has to be in continuous contact with the edge before it will do that. Trying to evaluate when the wiggler stops wobbling depends on how good your eyesight is, what you use to inspect the end while it's spinning, etc. So there could be some variability there. The "preferred" approach also depends on what your requirements are!
When I use the pointed-end attachment to find the center of a pop mark, I use a machinist's magnifier to check for wobble. It can still have some wobble going on, even when you can't see it with the naked eye. These days I'd rather use the edges of the workpiece as datum coords and drive the table to where it's needed using DROs. You can't always do that so you have to use what's best suited for the task at hand. As always.
I also have an electronic edge finder & the maker says NOT to spin it while finding an edge.
I have wondered if the presence of lubricants alters how well a wiggler works. Any comments there?
Mark
When I use the pointed-end attachment to find the center of a pop mark, I use a machinist's magnifier to check for wobble. It can still have some wobble going on, even when you can't see it with the naked eye. These days I'd rather use the edges of the workpiece as datum coords and drive the table to where it's needed using DROs. You can't always do that so you have to use what's best suited for the task at hand. As always.
I also have an electronic edge finder & the maker says NOT to spin it while finding an edge.
I have wondered if the presence of lubricants alters how well a wiggler works. Any comments there?
Mark
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Posted by: Ian Newman <ian_new@yahoo.com>
