Locating Many Existing Holes

[jmarkwolf]

I neglected to step backwards when they were looking for a volunteer here at work, to locate holes (more-or-less) accurately, comprising mounting hole patterns for a variety of small automotive DC motors.

I'm not a machinist, but an electrical engineer. I have been tapped to do such things here at work because they know I have a small machine shop at home.

We have an RF-31 clone table top mill with an Accurite DRO here at work, but not much else.

The Polish method I've stumbled on is to locate one of the holes, by clamping the motor in the mill vise, then move the table until a transfer punch of the closest size drops into it, and resetting the DRO to 0,0.

Then moving the mill table such that the transfer punch drops "cleanly" into the remaining holes when pulling the quill handle, and noting the coordinates on the DRO. I ultimately draw up the bolt pattern in AutoCad.

I said it was Polish.

This has been working fairly well because I don't need too much accuracy.

I know using pin gauges would improve my process, but what would the preferred method be for locating the holes? The prints are proprietary or very hard to locate (think China).

 

[Tony Wells]

Well, with a mill equipped with a DRO, you have a rudimentary 2d CMM. Clamp a sample down to the table, sweep each hole with a DTI and after zeroing on one hole as an origin, sweep each remaining hole and note the coordinates. Then go to your CAD program and lay them out, and rotate until 2 of the holes lie in a horizontal or vertical plane and share a common zero on one axis. Use rotate in your CAD and move the non-origin holes as a set to orient them in a way that makes sense.

If these are threaded holes, get some socket shoulder screws and sweep the ground OD and follow the same general method.

 

[KMoffett]

Another way with the DRO is use the conical end of an edge finder. The only use I've ever found for one. With the finder not rotating , visually center the cone over the first hole. Lower the cone into the hole so it lightly touches the rim. Move the table so the finder's body cylinder and the cone's cylinder are visually concentric. Even run your finger up and down the body to verify egocentricity. Zero the DRO, and repeat to locate the other holes' coordinates...and follow Tony suggestion with CAD. This may not work as well on holes that are tapped.

Ken

 

[RIMSPOKE]

I USED TO TAKE WELDING WORK HOME FOR THE ENGINEERS AT TOSHIBA .

WE WERE NOT ALLOWED TO DO ANY REAL WELDING IN THE SHOP BECAUSE OF
FIRE CODES & THE SPRINKLER SYSTEM IN THE BUILDING .

MANAGEMENT FOUND OUT ABOUT MY FREELANCE WELDING AND GAVE ME DIRECT ORDERS
NOT TO DO ANY MORE FREE WELDING FOR THEM .

I KEPT RIGHT ON , IT WAS WAY TOO MUCH PAPERWORK TO GET IT DONE OUTSIDE .
I THINK THE WARNING WAS TO COVER THEIR BACKSIDES IN CASE I BURN MY SHOP DOWN
WHILE DOING ONE OF THEIR JOBS .

DESPITE ALL THE LITTLE THINGS I WAS DOING BEHIND THE SCENES , THEY STILL CLOSED THE SHOP
AND LAID ME OFF AT THE END OF SEPTEMBER .

I AM STILL UNEMPLOYED BUT I HAVE NEVER BEEN BUSIER .

 

[KMoffett]

I USED TO TAKE WELDING WORK HOME FOR THE ENGINEERS AT TOSHIBA .

WE WERE NOT ALLOWED TO DO ANY REAL WELDING IN THE SHOP BECAUSE OF
FIRE CODES & THE SPRINKLER SYSTEM IN THE BUILDING .

MANAGEMENT FOUND OUT ABOUT MY FREELANCE WELDING AND GAVE ME DIRECT ORDERS
NOT TO DO ANY MORE FREE WELDING FOR THEM .

I KEPT RIGHT ON , IT WAS WAY TOO MUCH PAPERWORK TO GET IT DONE OUTSIDE .
I THINK THE WARNING WAS TO COVER THEIR BACKSIDES IN CASE I BURN MY SHOP DOWN
WHILE DOING ONE OF THEIR JOBS .

DESPITE ALL THE LITTLE THINGS I WAS DOING BEHIND THE SCENES , THEY STILL CLOSED THE SHOP
AND LAID ME OFF AT THE END OF SEPTEMBER .

I AM STILL UNEMPLOYED BUT I HAVE NEVER BEEN BUSIER .

What???

Ken

 

[RJSakowski]

After watching a German gentleman use a laser to find the centers of holes, I tried an improvement. I have a laser pointer with a 1/2" barrel. The laser has an adjustable lens for focus and I set it for the shortest focus possible. I mounted the laser in my boring head and mounted the boring head in the mill spindle. I set the spindle speed at a fairly low rpm . The laser will trace out a circle. The circle diameter can be adjusted with the boring head adjustment to be slightly larger than the size of the circle that I am trying to locate. With a sharp focus and some care, you can locate holes fairly quickly and accurately.

 

[JimDawson]

After watching a German gentleman use a laser to find the centers of holes, I tried an improvement. I have a laser pointer with a 1/2" barrel. The laser has an adjustable lens for focus and I set it for the shortest focus possible. I mounted the laser in my boring head and mounted the boring head in the mill spindle. I set the spindle speed at a fairly low rpm . The laser will trace out a circle. The circle diameter can be adjusted with the boring head adjustment to be slightly larger than the size of the circle that I am trying to locate. With a sharp focus and some care, you can locate holes fairly quickly and accurately.

That is a cool idea!