How to use a center finder

[CoopVA]

Here is the reason for my question. I wanted to make a Dremel tool holder for my 9x20 lathe. Using guidance received I centered the job on my lathe chuck and made the tool holder. Pictures are attached.

Thank you for all the help.

Regards and happy turkey day,
Prasad
Wynnewood PA

I like that! Great idea...


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[JimDawson]

Nice job!

 

[Tony Wells]

For that application there is another method of choice for me. I'll try to set it up for a photo if I get a chance, but here's a description:


Take a small diameter drill rod or similar with a accurately concentric cone ground on the end. This rod should be around a foot long (adjust for lathe size). Put the non-pointed end in a drill chuck in the tailstock, and get the point in the center punch but just barely tight. Now put a dial indicator as near as possible to the pointed end of the rod. The length of the rod will allow it to flex and follow whatever error there is with the punch mark. If it is way out, you should back off the tailstock a bit as you go because the effect on the rod is to lengthen as it runs truer. You don't want to push hard enough to bow it.


Alternatively, you can chuck the center finder lightly and again, place the point in the punch mark and use an indicator on the collar just above the point so that the indicator follows the point. You aren't really interested in the runout of the body, just the pointed section that is following the punch mark. Only gentle pressure should be used to engage the center finder.

 

[prasad]

For that application there is another method of choice for me. I'll try to set it up for a photo if I get a chance, but here's a description:


Take a small diameter drill rod or similar with a accurately concentric cone ground on the end. This rod should be around a foot long (adjust for lathe size). Put the non-pointed end in a drill chuck in the tailstock, and get the point in the center punch but just barely tight. Now put a dial indicator as near as possible to the pointed end of the rod. The length of the rod will allow it to flex and follow whatever error there is with the punch mark. If it is way out, you should back off the tailstock a bit as you go because the effect on the rod is to lengthen as it runs truer. You don't want to push hard enough to bow it.

I understand your idea but where can one get a long drill rod with a conical end?. I am using a Chinese made lathe with no-good or questionable precision, I can not make a perfect (or near decent) conical end.

Please understand I am a beginner and not criticizing. I want to understand every possible answer to my question.

Thanks
Prasad
Wynnewood PA

 

[Skarven]

I understand your idea but where can one get a long drill rod with a conical end?. I am using a Chinese made lathe with no-good or questionable precision, I can not make a perfect (or near decent) conical end.

Please understand I am a beginner and not criticizing. I want to understand every possible answer to my question.

Thanks
Prasad
Wynnewood PA

You could use your new Dremel toolholder to grind a near perfect cone on the end of a drill rod. Set a non-critical angle on your compound and get the dremel height right, and you should be OK.

The toolholder is nice! Good work. I will also make one, shamelessly copying your design!

Kai

 

[prasad]

For that application there is another method of choice for me. I'll try to set it up for a photo if I get a chance, but here's a description:


Take a small diameter drill rod or similar with a accurately concentric cone ground on the end. This rod should be around a foot long (adjust for lathe size). Put the non-pointed end in a drill chuck in the tailstock, and get the point in the center punch but just barely tight. Now put a dial indicator as near as possible to the pointed end of the rod. The length of the rod will allow it to flex and follow whatever error there is with the punch mark. If it is way out, you should back off the tailstock a bit as you go because the effect on the rod is to lengthen as it runs truer. You don't want to push hard enough to bow it.

Tony

I have a few centerless ground rods 0.375" in diameter and about 10 inch long. Will it suit?

Thanks
Prasad

 

[prasad]

You could use your new Dremel toolholder to grind a near perfect cone on the end of a drill rod. Set a non-critical angle on your compound and get the dremel height right, and you should be OK.

The toolholder is nice! Good work. I will also make one, shamelessly copying your design!

Kai

Kai,

Thank you but what do you mean by non-critical angle? I did not understand that part.

Thank you
Prasad
Wynnewood PA

 

[Thoro]

What was the thread specs you used to fit to your dremel? When I made one of those jobbers a year or so ago I decided that trying to thread it was going to be a PITA so I bored it, then slit it, drilled, tapped and counterbored it for a cap head screw....making a clamp in effect. Probably would have been less work to thread it in hindsight....

 

[Tony Wells]

Tony

I have a few centerless ground rods 0.375" in diameter and about 10 inch long. Will it suit?

Thanks
Prasad

Prasad, a more slender rod would be better. You want it to flex as the out-of-center punch mark moves around a circular path as you rotate the chuck. I would use nothing larger than around 3/16". Then, use your indicator up close and personal to the part you are dialing in.

If you have a good running chuck, or a collet (even better), you can grind a point on your centering rod. Just mimic the angle of a live center as you would use in a tailstock. But it doesn't have to be exact. Just as long as it will seat well enough in your punch mark.

 

[prasad]

What was the thread specs you used to fit to your dremel? When I made one of those jobbers a year or so ago I decided that trying to thread it was going to be a PITA so I bored it, then slit it, drilled, tapped and counterbored it for a cap head screw....making a clamp in effect. Probably would have been less work to thread it in hindsight....

Hi Thoro,

Dremel thread size is 3/4" at 12 TPI. The bore was machined to 0.67" before starting internal thread cutting. I used a 1"x1/2" aluminum flat 4 inches long which was later milled to 1/2" square shank.

Hope this helps,
Prasad
Wynnewood PA (Near Philly)