View Full Version : How do you keep material from...

11-28-2003, 10:22 AM
I?d appreciate any help on a problem holding round stock when drilling or tapping in.

I have a finished piece of round steel (1 in inch dia and .5 in inch thick) into which I have to drill a center hole and tap in with a 3/8 thread. I have a hand tap device to help tap the threads straight and it has clamping set up to hold the work. I try to use ?v? blocks to hold the work from moving. Problem arises because the outside surface of the piece is already finished and I don?t want to scare it by clamping hard. But when the tap goes in deep, it starts to ?turn? the work inside the ?v? blocks.
Is there some kind of (rubber or plastic?) liner that I can use on the inside jaws of the ?v? block against the work surface that will keep the work from turning when the tap engages?
Is there a less damaging way to hold round rod firmly than using ?v? blocks?
Much thanks for any help.

11-28-2003, 10:28 AM
There are others with more experience, so I'll be interested to hear what they'd say, but.....you could try a thin piece of copper contacting the work 'tween the vee-block and workpiece....or possibly TWO vee-blocks sandwiching the workpiece.

Good luck,


11-28-2003, 10:47 AM
A good investment would be a set of 5-C collet blocks, or better yet, a horizontal/verticle 5-C fixture or indexer. Use one of these along with a collet stop to hold you part depth and you will have no problem holding the part without marring the finished surface. A 5-C emergency collet would also work but is limited in long term usefulness unless this kind of part repeats a lot.

Forrest Addy
11-28-2003, 12:01 PM
A handy thing to have around the drill press is a backless lathe chuck. They grab stuff awkward for a drill vise.

I have a 12" four jaw and a 6" three jaw whose only job is to be drill press stuff grabbin' equipment both are (very) cheap imports with one piece jaws. First thing I did was make extended chuck wrenches for them so I could tweak the chucks when they're falat on their backs.

11-28-2003, 12:32 PM
Probably the REAL way to solve this is to tap the hole before parting off the piece to final length, so you can hold on the parent bar and not worry about scarring, but, given the existing situation (which we're probably all found ourselves in, at one time or another....)

The ideas from the other guys all sound good to me. I'd probably go with the idea of wrapping the piece in something like a thin (1/32"?) sheet of copper or aluminum and holding in my lathe chuck. If no lathe chuck is available, two V-blocks will help.

11-28-2003, 12:35 PM
try putting paper between the pat and thw vee block. the paper will give a lot more holding power. If that don't work, go with Forrest's plan.

11-28-2003, 12:43 PM
I have used plain old black electrical tape, about three wraps. That protects even aluminum and gives pretty good grip with good centering in the chuck. I also use 16 guage annealed copper soft jaw covers in my bench vise.

11-28-2003, 03:22 PM
Get some scrap plastic sheet like hmw,uhmw,or abs. These are all soft enough to not mark the metal you're working with. You could use lexan, don't use plexiglass. Make a square chunk larger than your workpiece. Bore a hole the size of the workpiece, then cut through one side into the hole. Press the piece into it, and clamp in a vice. You could also clamp it in a 4 jaw, in that case, make the cut so that one jaw won't be right on it. The cut will close up as the pressure is on, and hold the round without damaging it. There is another way of putting the cuts in this plastic piece without cutting right through the side. Make a cut most of the way through, then put another cut from the inside of the hole, near the other cut. Do this again on the opposite side of this plastic piece. Now there's some flex in the plastic on two sides, so if clamping in a vise, the jaws will stay parallel, and the jig will compress around the workpiece without marking it. This jig stays in one piece so it's not a pain to use, and allows you to bore the hole slightly undersize, for a press fit of the workpiece. Makes handling and aligning easier, and it also holds better. This might sound more complicated than it is, but it's a good way to hold parts especially if there are many to do. A dollar store plastic cutting board is also a good source for plastic that won't mark the work. I think these are polyethylene or polypropylene, both soft enough, and a useable thickness.

[This message has been edited by darryl (edited 11-28-2003).]

11-28-2003, 03:39 PM
I use an old chuck that has no back to it, but so as not to damage the round stock, I wrap it in tape or use a card board tube.


11-28-2003, 04:12 PM
Aside from holding the part tighter use a larger tap drill which will need less torque. Assuming a 3/8-16 thread with a half inch engagement you can go as large as .325" on tap drill.

Also, be sure you're using a quality spiral point tap that's sharp (NO third world carbon steel taps).