By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Forum House Ad Zone

Finding the centre again

All Topics | Latest Posts

Search for:  in Thread Title in  
<< First < Prev 1 2
Terryd22/01/2012 21:54:45
avatar
1946 forum posts
179 photos
Posted by lee hawkins on 22/01/2012 18:16:28:
It may not work on something as small as maybe down to 6mm or something, but any other size circle it's perfect.
 
Get yourself a piece of paper+compass, get the diameter of your circle , draw the circle on the paper, then cut it out nice and accurate, fold it twice , you then have a perfect segment of the circle with a nice point, put that on the workpiece you want to find the center of, accurately lining it up, now where ever that point is will be spot on the center
 
Maybe most people already know this way.
 
lee.
 
We do,
 
but 5mm dia is a bit small for such methods,  even more accurate is to draw the circle in a drafting program and draw the centre lines with the finest lines possible.
 
T

Edited By Terryd on 22/01/2012 22:02:54

Terryd22/01/2012 21:55:38
avatar
1946 forum posts
179 photos

T

Edited By Terryd on 22/01/2012 21:57:04

Terryd22/01/2012 22:00:56
avatar
1946 forum posts
179 photos
Posted by Wolfie on 20/01/2012 19:59:59:
I tried that, the old jaws were only a couple of mm thick so thin that the drill would have had time to wander before biting.

Edited By Wolfie on 20/01/2012 20:00:40

Hi Wolfie,
 
You only have to mark the centre with the drill point, not let it bite, just a gentle rub of the drill point will do if you coat the jaw surface with marking blue or a permanent felt tip pen. Then you just have a tiny circle to find the centre of - much more accurate.
 
Regards
 
T
lee hawkins23/01/2012 07:05:27
7 forum posts
5 photos

Posted by Terryd on 22/01/2012 21:54:45:
Posted by lee hawkins on 22/01/2012 18:16:28:
It may not work on something as small as maybe down to 6mm or something, but any other size circle it's perfect.
 
Get yourself a piece of paper+compass, get the diameter of your circle , draw the circle on the paper, then cut it out nice and accurate, fold it twice , you then have a perfect segment of the circle with a nice point, put that on the workpiece you want to find the center of, accurately lining it up, now where ever that point is will be spot on the center
 
Maybe most people already know this way.
 
lee.
We do,
but 5mm dia is a bit small for such methods, even more accurate is to draw the circle in a drafting program and draw the centre lines with the finest lines possible.
T

Edited By Terryd on 22/01/2012 22:02:54

 

Edited By lee hawkins on 23/01/2012 07:06:20

Edited By lee hawkins on 23/01/2012 07:07:57

Ed Duffner23/01/2012 09:30:12
863 forum posts
104 photos
Now don't laugh guys, I'm only a beginner, but how about something like this? (knocked it up in Rhino3D).
 
The circular plate has known sized holes 1 to 12mm in increments of 1mm. This could be swapped for other plates e.g. half sizes or imperial.
 
The lower pin locates the desired hole size, which should be directly underneath the upper pin. The upper pin is then held in the mill chuck or collet. The job is then moved x,y until the marked feature on the job is centred visually in the plate hole. The centre finder is then removed and replaced with the milling tool/centre drill etc.
 

blowlamp23/01/2012 10:02:37
avatar
1885 forum posts
111 photos
A pair of dividers or a trammel with large cone points could also be used to transfer the hole centres from the old jaws to the new ones.
 
 
Martin.
Jim Greethead23/01/2012 10:04:53
avatar
131 forum posts
8 photos
I'm not laughing Ed, I think that is quite brilliant. Simple, effective and useful. Thank you for sharing.
 
Jim
 
Billy Mills23/01/2012 15:13:49
377 forum posts
Nice Ed, You can also print out a load of circles of different diameters on OHP film with the centres as very fine crosses then prick through the centre. Select circle over job then mark centre.
 
Michael mentioned overkill- well if you are using countersunk holes and fasteners you do need to get things right, some get very upset if the screw is not nicely centred in the countersink, it does not look good. For Wolfie's job it may be on the inside, if the countersink is to sink the head it still needs to be right.
 
Point that has not been mentioned is that the problem is an order-of-work issue. It may be tempting to cut the countersink at the same time as drilling holes but it could be best to leave it for later after spotting through for other holes.
 
Billy.
Martin W23/01/2012 16:45:06
940 forum posts
30 photos
Ed
 
How about a small mirror mounted on the lower upright set at 45 deg directly above the active gauge hole. This would make viewing easier and remove parallax errors especially on the smaller hole sizes.
 
I like the idea as it could be put to many uses where a centre needs to be determined, sheered screws, broken taps/drills etc. Get it patented quick and make yourself a fortune, well maybe .
 
Cheers
 
 
Martin
<< First < Prev 1 2

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Shopping Partners
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

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.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

 

Donate

donate