[vacpress]

I just went to the hardware store to get a starter-punch set to locate holes accurately. Last night I was drilling a hole pattern into a piece of metal, and ended up using a heavy-duty wood\dry-wall type screw to locate holes. The impacts from the hammer were hurting my fingers, and the indentation produced was not very round...

Today at the hardware store I was confronted by at least 4 or 5 types of punches. I dont know much about them - what kind is best for layouts in aluminum, brass, and other soft metals?


Thanks!

[Carel]

A sharp punch approx 90 degree. Put in 1 scribed line and move gently till you feel it "click" in the other line. Give it a light tap, check and hammer tilted to correct. If correct give it the final blow. Get angry with yourself if things don't fit. Overboring and tapping a drilled hole to make things fit cost you bonuspoints.

Carel

[lakeside]

there are a few types the main thing is if the punch is for a hole or cicle if the tool edge is sharper on the outside it for a hole if it sharper on the inside it for a cicle cut out also if the punch say it for 1/2" either the outside will be 1/2" or the inside will be 1/2" go to the msc web site I think it www.mscdirect.com they have some and you can see the type on line

[vacpress]

thanks for the replys...

hmm.. i think what i need is a guide on accurate manual part layout and cutting... i am fairly inept when it comes to this...

anyone seen anything like that?
(600th post)

[lakeside]

If you are trying to do an exact location you could hold punch in drill chuck on a machine and just bring the quill down so it leaves an indentation in stock then you can place the punch back to the spot and finish the job with a hammer

[lakeside]

also you may what to look at what called a pannel punch

[vacpress]

lakeside... that would only work if i had a good way of accurately locating said hole!

unfortunately my enco mill is not a precision tool.. more like a giant hand drill on a stand...

[lakeside]

That true but you could put a center punch in drill chuck to line up center off of the edge with a scale and then put the punch in the chuck by using you big drill press (as you call it) you keep the punch 90 deg. to work

[lakeside]

you can make guides for hole location if you need to do a lot of holes

[lakeside]

also if you use you big hand drill have a piece of pvs or wood between table and part keeps those punchs sharper and longer

[One of Many]

If you must do this by hand. Take a look at some trammel points. These can be mounted on a small beam or rod type of decent length. You can set them against your scale or calipers for center to center distances. Use at least two holes or points of reference to locate the next hole by creating a crossing point you can trust. A tap with a plastic mallet should put enough of a spot to finish it off with a center punch.

Another suggestion is a set of transfer punches, screws and pins.

With transfer punches, you can place the punch(they come in sets same as drill sizes) into the hole with your part to be drilled below. Clamp it up if need be. Used the closest size that will slide in. I wrap them with masking tape if it is an odd ball diameter hole and no punch to match it well. Then tap with a plastic hammer. You can use a metal hammer, but they can swell the end, which I really dislike since I use them for locating etc. Do all the holes accessible while it is position. You can always go back a drill more later in reference to the new holes.

Transfer screws and pins are another great set of tools to have. Either you screw them in with the holders built in socket wrench. The pins just set in, but they can be loose and that don't help. More tape.......to get them to stay put within reasonable center. Once all or just a few are installed you can place the part against the protruding points and smack it enough times to transfer those points into your part. Kind of a no brainer, but the points should all be set to the same height.

To keep the drill from wandering, use a smaller drill, center drill or spotting drill to start the hole. Often, when using 118deg bits (135deg are even worse), the center punched mark is gone before the drill point is deep enough to maintain its location. That is usually found after the part is all done.

The old addage of "preparation is 90% of a job well done" comes to mind. A few tricks up your sleeve can make it so much simpler. :idea:

DC

[Cal Blacksmith]

In the tool making trade, we use “drill blocks” and “bombsights” to accurately pick up layout marks for holes.

A drill block is nothing more than a block of steel about ¾” or 1” thick that has been milled or ground to have a good flat surface. A hole is then bored into it perpendicular to the good face. The hole is normally ½” and is a very accurate ½”. The hole can be any size and I have some blocks that have a 1” hole and liner bushings that have been center less OD ground to nest together so that I can step down to ½” so that larger holes can be drilled. These blocks can be any size or length depending on your needs. A very small block that is not suitable for use as a drill block comes with the bombsite for use as a center-marking device. If all you are doing is marking the center of the layout lines, the “stock” block is fine. The drill block uses slip fit bushings (renewable bushings) to keep the drill running true to the center mark.

A link to a bushing manufacturer is here:

http://www.carrlane.com/Catalog/inde...173C1B08535246


A bombsite (optical center punch) is an acrylic (cheep) or glass (high quality) rod that is the same diameter as the hole in the drill block, usually ½”. Into one end of the rod is a pair of accurately etched cross hair lines and the other end is shaped to magnify the image.

A link to how to make your own and what they look like is here:
http://www.nucleus.com/~harlan/punch.html

A link to a commercial one is here:

http://www.productsusa.com/howtouseom.html


You place the drill block on the item to be drilled that has been laid out, place the bombsite into the drill block then align the bombsite to the layout lines on the part.”C” clamp the drill block to the part so it won’t move then you can use a transfer punch through the drill blocks hole to center punch the part. If an accurate hole is needed, you then place a slip fit bushing in the drill block and step drill out the part to the desired size, starting with a small diameter drill and stepping up in size to the finished size. For the best hole use a reamer for the final size. With this method, you can drill holes, by hand that is perpendicular to your part and accurate within .001” for location.

For layout work it is hard to get better than a surface plate and height gauges. A plate and gauge could be picked up for a couple of hundred $ if you look around. Add to that you should have a good knee block to hold your work on and keep it square to the plate.

EDIT: If you make your own bombsite, you can check the center of your bombsite by rotating it in the block without moving the block. You will quickly see if your new center is "true" If not, you can either face the end off and re-mark it or when using your bombsite, rotate it so that your layout lines are centered in the "circle" that your off-center center makes.