|Ian P||14/11/2019 20:20:48|
2254 forum posts
I bought one of the Arc Eurotrade edge finders a couple of years ago and apart from a quick test when it first arrived I have never really used it. Today I experimented again but am not convinced it is any more repeatable than my goto method (short length of 4mm precision ground rod and observing light between it and the edge).
I then started to think about what the physics/principles of its operation were. I know the basic idea but how much does friction between the job and the (moving surface) compared with friction between the two faces of the finder affect its operation?
Other factors that might come into play are, the outer diameter of the two abutting faces and the diameter of the operating tip (on this Arc one there is a 4mm tip which is about 40mm lower than the split diameter bit). There is sticky grease between the moving faces but I dont know if that is meant to be removed or not.
I know lots of people use these without problems (presumably) so maybe I am missing something.
|pgk pgk||14/11/2019 20:29:49|
|1486 forum posts|
You should be able to wiggle it side to side without much effort but if it's got sticky with packing grease or old crud then I'd clean it out. As you know the function is simply to be pushed off-centre as it touches the edge and you don't want anything sticky stopping it. I don't think I've ever oiled mine but lucky my shed doesn't promote rusting.
Rather than squinting (and if you don't trust the edge finder) then a simple rod with a bearing and a spot of paint will work.
|Phil P||14/11/2019 20:48:46|
|531 forum posts|
I will also say that the bearing on a rod is a good solution, it is certainly the one I use 95% of the time on my Boley & Leinen (BCA) jig borer.
These are what I have custom made for my my machine and it is the one on the right with the 1/2" diameter ball race that gets used all the time.
I also have similar ones mounted on plain round shanks that I use in collets on my Alexander milling machine.
I can usually rely on getting within .0005" using this type of edge finder and for most jobs that is more than acceptable. I have a few other ways of getting better accuracy, but this thing is just so easy to use along with the DRO.
Very easy to make and use, all you do is just move it until the outer race touches the work and stops spinning, that is where the spot of paint on the edge of the outer race comes in handy so you can see when it stops spinning easily. Then subtract half the bearing diameter to get your spindle centreline over the work edge.
Edited By Phil P on 14/11/2019 20:53:54
Edited By Phil P on 14/11/2019 20:54:13
|pgk pgk||14/11/2019 20:51:34|
|1486 forum posts|
Edited By pgk pgk on 14/11/2019 20:52:22
|mark costello 1||15/11/2019 19:49:46|
548 forum posts
Years ago My edge finder got sticky. I called Starrett and asked what They used to lube Them with. They said STP. Don't know the British equivalent. Did not want to buy an entire can for just a couple of drops, so I started watching the skips around car auto parts shop and found a discarded can with an ounce or two in it. Still have it, still good after about 30 years.
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.