How to dial in/indacate a toothed wheel?

[JeepsAndGuns]

OK, this is possiably a good one. I have not been able to figure anything out yet. I have something that I need to get set up in a 4 jaw chuck and have it be true on the outside. Only problem is its a toothed wheel.
What I have is a crankshaft reluctor wheel for a automotive fuel injection system. This partcular one started life as a crankshaft that was cut in two and then the wheel cut out of it. (wheel is cast as, and machined as part of the crankshaft) I took and cut the crankshaft apart and got it down to just the wheel. One side of the wheel is a main journal, so its centered, I left it there to have something to clamp on with a lathe chuck. The other side was a rod journal, I cut it flush. This will be mounted on the center hub (not the rubber isolated part) of a harmonic balancer on a older engine to retrofit it with modern fuel injection/DIS ignition.
Here are a couple pictures showing the wheel:







So I have already taken a facing cut off the rod journal side to clean it up. Now I am to the point of needing to bore out a center hole. Only problem is, I need this to be exact. The OD of the wheel must ride true, otherwise it will either send bad signals or not work at all. The crankshaft position sensor must stay a specific distance away from the teeth for a proper reading, the wheel must ride true, it can not wobble or run in a eccentric pattern. So basicly I need to set it up in my 4 jaw chuck and indacate off the OD. Now there is my problem. Anything else I could just stick the dial indacator on it and dial it in. But this has teeth, so I can not use a dial indacator. SO, how in the world do I get this trued up on the (toothed) OD?

 

[mzayd3]

Indicate on the chuck side off the main journal.


Sent from my iPhone using Tapatalk

 

[rgray]

A test type indicator should work once you get it reasonably close. Simple wire pointer like what you would make for an engine with a missing timing pointer would help to get it close. Set it up to the side and use it to get close. Fill the gaps with wax and then clean the outer surface might help if you have to use a standard indicator.

 

[kd4gij]

I would 4 point it. Find 4 points 90deg apart alingn them up with the 4 jaws of the chuck. Now set your indacator on the first point and zero the dial lift the plunger and rotate 180deg set plunger down. Adjust the part half the distance it is off. Then go to the outher 2 points. It takes a bit but you can get it centered that way. Hope it makes scence I do it all the time but toexplain t is anouther thinng.

 

[f350ca]

Is your chuck big enough to grab the OD of the timing wheel (looks like it is), if so reverse it in the chuck, grab the OD and dial it in off the bearing journal.

Greg

 

[eightball]

I indicate sprockets using the teeth all the time. In industrial applications, the sproket hubs are often not concentric with the teeth. Hence, I indicate the teeth and the face of the sprocket. After boring I take a light facing cut so i have a good surface to cut my key. Just place your indicator on the surface lightly. I use a regular 1" travel starret indicator. I dont want but about ten thou contact. I usally hold the plunger while i go to the opposing jaw. Especially til I get it close. Its suprizingly fast and easy to do. You could also mount your indicator on carriage and crank it out of the way til you get to next jaw. I personally only do that when im indicating square or rectangular stock that excedes the travel of my indicator. You can use a pointer or even a piece of cardboard to get close. I had to check a 25 foot auger that way today bout 14" in diameter. I had a piece of aluminum sheet about 2 foot long and it would only contact 2 flights at a time. It was about 1/8" out.Good luck !

 

[easymike29]

Use a back plunger indicator with this kind of a tip.

http://www.motionindustries.com/productDetail.jsp?sku=02052267

Gene

 

[David S]

I had to do something almost the same, except on a smaller scale. Made a fixture and machined a counter bore to accept a snug fit for the OD then machined the ID in prep for an insert.

David

 

[JeepsAndGuns]

lots of good ideas. I'm gonna try to make some time this weekend and give some of them a try and see if I can get it dialed in. The idea of using a peice of thin metal sheet sounds like a interesting idea. I have some feeler guages and may give that a try.
To answer a question, it might look like it, but the chuck will not open up enough to grab it on the OD, already tried. The one in the picture is a 3 jaw, I will use my 4 jaw when boring the center hole.
Thanks for the ideas! Feel free to keep posting up more if anyone has any more.

 

[kd4gij]

What size is your 4 jaw. you can reverse the jaws on a 4 jaw and chuck things larger than the chuck.