[How do I?] Center On A Part To Drill A Hole

[Bill C.]

They're not cheap, that's for sure. Not sure how well it repeats but Grizzly offers a small 2" self centering vise that would accomodate this. $155 doesn't seem like that great of a deal to me for it but if you have to do thousands of them it's worth the time saved. https://www.grizzly.com/products/2-Mini-Self-Centering-Vise/T10254

You could probably make one if you have the time.

I have never seen one before, thanks for the link. He needs to consider cost over profit. If this is going to be a constant part then, if it was me I would, buy it and add a part stop to one of the jaws.

 

[John Hasler]

Should be possible with a bushing for the drill bit.

Use two of these pivoting on shafts into the base of the device. Connect the two with a linkage and use a lever, springs, and an over-center mechanism to lock/unlock. You would place the part between the pins, push it up against the stop (you could use a magnet to hold it there or tilt the whole assembly and use gravity). The stop could have a slot to receive the end of the part and a bushing for the drill bit.

This has made me think about a design for a general-purpose self-centering vice based on this principle. Should be capable of greater precision than the usual leadscrew design with two moving jaws, though with less clamping force.

 

[Wreck™Wreck]

Is someone measuring the parts after you drill them?

If so I only have two words for this, Good Luck.

Also certain jobs should not be entertained regardless of quantity, unless the money is very large of course.

 

[JimDawson]

Thank you all for your replies. Based on the ideas presented, here is how it will work. The clamp is a parallelogram. I'll add a release lever, a spring, and a drill bushing but this is the general concept. This will keep the part on center as long as the width is in the range of the clamp.

 

[Bill C.]

I am concerned about the burr on the hole. On second thought you may not be responsible for removing the burr. Your part is simply drilling the hole per drawing and letting someone else deburr the part. I trying to make a mountain out of a mole hill. Whatever you decide I wish you success in this project. Keep us informed on your project.

 

[Bill C.]

*IF* the parts are uniform standard widths (not each part being oddball width) Mill the different width slots in a piece of aluminum, grab that in a vice, drill the hole the correct distance from the end. You end up with a stepped slot, hole in the right place. Add a work stop and have at it. The part sits in the proper sized slot, hit the workstop, drill hole. You could screw a strap over the top of the slot sideways to prevent the workpiece jumping out. Slide in part, squirt cutting oil, drill, remove, repeat ad nauseum.
If the parts are all unique widths, a lever activated self centering vise would be quick, pneumatic with a foot pedal even faster, but *WATCH THOSE FINGERS!*

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If you use a small clamp as a hold-down, the slotted fixture sounds good to me. http://www.grainger.com/product/DE-...m/rp/s/is/image/Grainger/3CXA4_AS01?$smthumb$

 

[Eddyde]

Brilliant solution. You could also add a spring loaded plunger on the parallel that moves towards the locating pin on closing, to push the work against the pin. Having done production runs of up to 3000 parts, I can say, even saving a second or one thing to think about per cycle is worth it.

 

[Bill C.]

I was wondering what have you decided to do? An interesting challenge. I like a fixture but a self-centering vise with a step milled in both jaws to eliminate parallels sounds good too.

Hope you keep us updated on your progress.

 

[JimDawson]

I am concerned about the burr on the hole. On second thought you may not be responsible for removing the burr. Your part is simply drilling the hole per drawing and letting someone else deburr the part. I trying to make a mountain out of a mole hill. Whatever you decide I wish you success in this project. Keep us informed on your project.

I was wondering what have you decided to do? An interesting challenge. I like a fixture but a self-centering vise with a step milled in both jaws to eliminate parallels sounds good too.

Hope you keep us updated on your progress.

I am going to go with the parallelogram fixture. Once I add the spring and release lever or maybe a small air cylinder, and foot peddle, it will work fine for this application. The material is a ceramic so there can not be a burr, so that won't be a problem. This is being set up on a specialized, customer supplied, drilling machine.

My only job is to design and build the fixture. I am not drilling the holes at all, it will be done in their production department. I rarely do production jobs, in fact, I have only done one production run in my life, 300 parts.

 

[Bill C.]

Thank you for sharing your design. I never drew up a parallelogram fixture before. Definitely quicker. I had to search the Web to fine something similar, I found a doweling jig. I forgot you design and build tooling. Glad you are not messing with production. The "Best" to you with this project.