Improving Drilling Accuracy after Center Punching

[jjr2001]

Probably old hat to many but I just tried this method and I must say that it works and works well.
The holes are in a base plate that has limited room for error since I did not want to drill out the sides
of the vise that the base was to be used on. It was a casting so it was not exactly symmetrical.

I did not center drill any of the holes after I center punched them.
Instead I used a 1/2" center in my drill press chuck and lined up each hole prick with the center point.
Locked the base down to the drill press table with a toggle clamp for each prick point.
Then I changed out the center for the drill bit without center drilling. Went straight to the #21 drill bit.

All the holes were drilled and then the newly drilled base was aligned to the bottom of the vise.
The base was then used as a template and the holes were drilled into the vise cast iron frame.
Drilling was exactly where expected and none of the holes broke through the sides of the vise.
The drill bit used was a #21 which was the tap drill for the 10-32 threads that needed to be tapped.

The rest of the story is in my next project: Locking Down The Vise
http://www.homemadetools.net/forum/r...905#post105773

Cheers, JR

[Paul Jones]

JR,
Excellent technique and explanation. I have used the same method with a "sacrificial" over-plate clamped on the part and preserved the exact very close-to-the-edge alignment without any break-through. You have to trust the method.
Thank you for the posting.
Regards,
Paul

[jjr2001]

Thanks Paul, good to know that other workers have used a similar method.
I know in the past when prick punching and center drilling without anything lining things up that my results were
often close but not right on. This method really works. Using the clamp helps too.

Cheers, JR

[DIYer]

Thanks jjr2001! We've added your Drill Press Centering Method to our Drilling and Drill Presses category,
as well as to your builder page: jjr2001's Homemade Tools. Your receipt:

Drill Press Centering Method by jjr2001

tags: drilling, centering

[mklotz]

For a bit more accuracy in this technique, I use the pointy end of a double-ended edge finder in place of the 1/2" center. A fingernail dragged across the junction where the point meets the body of the edge finder can detect the tiniest deviation.

I use the same technique to center over holes, both small and large...

http://www.homemadetools.net/forum/h...ring-aid-26216

[Douglas Rome]

How do you use the slots in the drill press table? Can you show me
with photos? Thanks, douglas

[jjr2001]

Sure can. T-slot nuts are available from Littlemachineshop.com and any machining equipment supplier. Many on line and even Ebay.
Here are a few pics of the details.

As you can see I have also drilled and tapped mounting holes in my drill press table. Mostly for some jigs that I use from time to time.
T-Slots are more versatile.

Cheers, JR

[Douglas Rome]

Thanks I have to get some I had the drill press for years but never
knew what the slots were for. Thanks, douglas

[jjr2001]

You are very welcome Douglas, if you don't have a drill press vise yet then you may consider one of them.
Two types are inexpensive and very useful on the DP. One has slots that you can use with the T-Slots and bolts to fasten it to the DP table.
The other one uses slots in it's side for clamping. It can be used in the horizontal or vertical mode.

I have included a picture of the side clamping type below. It is mounted on a mini mill. You can't see the T-slots since the mill has been fitted with table covers in that picture.

Cheers, JR

Just added a second picture showing the slots better. You can see how it could be used in the vertical position on the DP.

[Douglas Rome]

Thanks, I have a couple of nice DP vises, I wondered what the slots were for. The machine tool company
you referred doesn’t carry 916” slot nuts, must be an oddball size? I wish I knew how to post a link,
I found an alternative nut that might work. Its a flat bar about 1” L x 1/2” W x 1/8” thick with a 1/4-20
female thread in the middle. Thanks douglas