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MattMaier
09-11-2014, 08:37 PM
I' looking for plans for an automatic center punch. I'm an apprentice machinist who also has access to machines at home and I think it would be an interesting and worthwhile project.

Duffy
09-11-2014, 09:21 PM
Take a Starret automatic center punch apart and copy it. Some people call this "reverse engineering." You might want to change the thread pitches, since those used by Starret are unique to Starret.

Arthur.Marks
09-11-2014, 09:37 PM
I wonder if "center punch with sliding sleeve hammer" is an automatic center punch? Project #22 in South Bend Lathe's Machine Shop Projects (http://www.youroldtimebookstore.com/product-p/22482.htm).

tlfamm
09-11-2014, 09:46 PM
I wonder if "center punch with sliding sleeve hammer" is an automatic center punch? Project #22 in South Bend Lathe's Machine Shop Projects (http://www.youroldtimebookstore.com/product-p/22482.htm).

See page 7 for an image of same:

http://www.wewilliams.net/docs/1928%20-%20South%20Bend%20Machine%20Shop%20.pdf


I suppose it might be thought of as a "1'st generation" automatic center-punch.

Arthur.Marks
09-11-2014, 10:28 PM
Thanks for that illustration, tlfamm. Yeah... not exactly what is asked for :) I have a contents index for the Village Press books. I see Metalworking Book Three (https://secure.villagepress.com/store/items/detail/item/864) lists "An Automatic Punch" under shop improvements. I wonder if anyone could provide a general description of the one presented there?

Sun God
09-11-2014, 11:05 PM
It's not really something you need plans for; google image search for 'automatic prick punch' or 'automatic center punch' will give you cross sectional images that outline the basic principles, then copy those as you see fit. There's even an animated gif on the wikipedia article for 'automatic center punch'. The biggest challenge will be sourcing appropriate springs.

Reed
09-13-2014, 11:02 AM
Arthur,

I have the book and it is a sliding hammer center punch, no springs. The same design as tifamm's .pdf he pointed you to, just made a bit differently.

- Reed


Thanks for that illustration, tlfamm. Yeah... not exactly what is asked for :) I have a contents index for the Village Press books. I see Metalworking Book Three (https://secure.villagepress.com/store/items/detail/item/864) lists "An Automatic Punch" under shop improvements. I wonder if anyone could provide a general description of the one presented there?

Norman Bain
09-13-2014, 05:27 PM
This link has some good images of mechanims.

http://en.wikipedia.org/wiki/Automatic_center_punch

gundog
09-13-2014, 06:29 PM
Harbor freight sells them cheap buy one and take it apart build one with good materials. http://www.harborfreight.com/catalogsearch/result?q=center+punch

It is probably a China copy of the Starett.

bob_s
09-15-2014, 12:02 PM
Harbor freight sells them cheap buy one and take it apart build one with good materials. http://www.harborfreight.com/catalogsearch/result?q=center+punch

It is probably a China copy of the Starett.

Actually it's a dead ringer of a Craftsman auto center punch!

dp
09-15-2014, 12:22 PM
Buy one from Harbor Freight and learn how it is made. Make a copy, put the original in your car in case you ever need to break out a window.

http://www.youtube.com/watch?v=LLaUrJYvQG8

tlfamm
09-22-2014, 10:24 PM
Here are drawings showing the internal components of auto center punches:

http://www.micro-machine-shop.com/Lisle_auto_center_punch.pdf

(slow to load)
http://www.micro-machine-shop.com/General_Steel_Center_Punch_No78_Assembly.pdf

Glug
03-01-2016, 08:14 AM
With the current enco sale, a friend reminded me that I also need an automatic center punch. But when I read reviews of the models from General, the were pretty mixed, with lots of complaints. Those are all made in India, and apparently quality tanked when they made the move. Too bad they didn't drop the price accordingly, from the lofty $20-$30. There were even some complaints about Starrett.

Guess I'm going to try one of the harbor frieght units for $2.99, and maybe rebuild as necessary.

Any other recent experiences with ACP's?

lynnl
03-01-2016, 09:15 AM
.....

Guess I'm going to try one of the harbor frieght units for $2.99, and maybe rebuild as necessary.

Any other recent experiences with ACP's?

I have a couple of the Harbor Freight ones, and they work just fine.

cameron
03-01-2016, 09:35 AM
I have a couple of the Harbor Freight ones, and they work just fine.

I have a couple of cheapies, and they're both crap.

Making one would be an interesting exercise, but I think you would need to count on including some hardened and either ground or lapped internal parts if you want it work reliably and last a reasonable time.

Rosco-P
03-01-2016, 10:38 AM
With the current enco sale, a friend reminded me that I also need an automatic center punch. But when I read reviews of the models from General, the were pretty mixed, with lots of complaints. Those are all made in India, and apparently quality tanked when they made the move. Too bad they didn't drop the price accordingly, from the lofty $20-$30.

Would a poorly made tool at a cheaper price perform any less disappointingly?

This may help explain the change in manufacturing location: http://www.generaltools.com/about-us/

So many seem to think the answer is buying the cheapest piece of crap that they can find, no surprise that they had to move manufacturing offshore.

Richard P Wilson
03-01-2016, 02:52 PM
If you manage to make one that works reliably, more than just the first few times, you'll be doing better than most of the cheap manufacturers. To be honest, after so many disappointments, I've given up on automatic centre punches.

mattthemuppet
03-01-2016, 05:05 PM
my HF cheapie has worked just fine for the 5 years or so that I've had it. Makes punch marks where I want punch marks, not sure there's more to an automatic center punch than that. I've resharpened the point a couple of times, so perhaps it's a little soft, I don't know. Then again, with the variability of the goods coming out of China, just because mine is fine doesn't mean one you buy will be also.