Using a Mini Lathe to Make an Optical Center Punch

Hello again everyone, I've wanted one of these for a while and figured a video was a good excuse to make one!
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[@dennythomas8887]

I have one like this a tool maker friend of mine gave me years ago. The design is pretty close to what you made with the exception of the acrylic rod has a shoulder that holds the end about .050 off the work surface because acrylic scratches very very easily. Another design difference is there is a second acrylic rod that comes in from the side at a 45* angle about half way down to transmit light to the center mark. If necessary you can use a flashlight or a light source (goose neck lamp) to brighten up the target and make it much easier to see. But all in all nice job on this build.

[@tyronejk]

I’ve seen some comments suggesting that you get a four jaw chuck but that’s necessary only if your stock material is already at the need diameter. If you cut the diameter down slightly and then cut the point without moving the part in the chuck, your two features should be concentric.

[@bobuilt10]

As an apprentice I was taught a three stage process to accurate centre punching. Scribe a cross hair on the hole centre with a nice sharp height gauge. Use a very acute angle centre punch with a point sharp enough to be a scriber. Gently slide the point along one of the scribed lines until you feel it hit the cross scribe. Give it a light tap, just enough to mark the centre. Now take your normal centre punch and locate it in the small punch you already created and give it a good whack. With practice you can consistently get within a few thousands. With regards to your design for the optical punch why not try scribing a fine crosshairs at half the diameter on the acrylic rod?

[@Someone_Should_Make_That]

I’ll have to give that process a shot, thanks for sharing! And good suggestion, a crosshair would definitely make it easier to line up the punch.

[@garyseverson3094]

I believe the commercial ones have a piece of cork on the bottom to prevent slipping, instead of making your own punch, substitute a transfer punch.

[@zachburrows9842]

Machining tip regarding the accuracy of the punch itself. Leave excess length on the punch stock. Use a dial indicator and a dead blow lightly tap the stock true. This can be done very accurately (tap with lathe on). Then do all matching without removing the part. You can then cut to desired length as the top side has no real need for true precision.

[@danceswithaardvarks3284]

Some great tips there thanks. I made one a while ago and it's not quite right, so I'll check my centre punch as I didn't consider that could be an issue. A suggestion I have is making the bottom 1/4" of the holder out of acrylic with an embedded LED powered by a CR2032 battery. I did this and it is a game changer. Illuminating from the bottom allows you to see scribe lines much more easily.

[@jimsvideos7201]

Nice work on the part and video. An o-ring in a groove in the face of the base part will give you some traction, and rotating the lens in the body while you look through it will highlight any eccentricity in your crosshairs.

[@Joz104]

Love the video! The quality keeps getting better. Keep it up!

[@sjmaguirepdx]

I realize this is an older video and I admit I didn't read all the comments so I apologize if it's already been said... The reason the drill bit didn't work to clean the sides of the center hole is because the flutes on a drill bit do not have a cutting edge. They are designed to remove the cut chips. The cutting is all done at the tip.

[@pauldevey8628]

Great video and love the project.

[@dirtbagd89]

Interesting idea. I've had similar issues getting centre punch marks in the right place. You'll find the 4 jaw independent chuck very useful. You should put a quick change tool post and boring bar on your Christmas list too. Thanks for taking the time to make and edit the video.

[@homemadetools]

Nice job yet again! We shared this video on our homemade tools forum this week 😎

[@Someone_Should_Make_That]

Glad you enjoyed!

[@camillosteuss]

Make your own cross hole boring bar... You just take a rod of precision stock, drill it from the end on the lathe and tap it for a set screw, you cross drill that hole to fit any diameter drill bit you want and then you use that... It also works great with broken taps, endmills and similar nonsense... Its my favorite boring bar design by far, and you can grind the hss rods into whatever shape you need... Be it threading cutter, groove cutter, sharp finishing cutter with whatever radius... Drills are the worst for that, as the drill shank which is cyl. is soft, so you have to harden it... Broken taps and endmills are the best... Actually, if you want the best, get a 50 or 100 pc set of carbide pcb drills, grind the drill tip off, you are left with a 3.175mm carbide body which is just the best for such work... Also, grind a flat on the side of the cutter shank for the set screw to actually be able to prevent it from rotating... That is how you use cut off drills and such as boring bars... This method which you attempted could maybe work with a cut off stub drill, due to its short flute length and thus higher rigidity, but still, the endmill option was the best call you could have made in your scenario... I highly advise you to get an assortment of centerless ground inox rods and to make your own boring bars that way... Its easy, cheap, and allows you to make any type of boring bar you need... The cross hole neednt be at 90deg to the screwhole, you can drill the rod at an angle, to allow you to have the cutter in front of the boring bar end, thus allowing you to bore out flat bottomed bores that arent passing all the way through the part... Tho, then you have to offset the setscrew aswell, or make a special plug to interact with the angle that the cutter is at... A wedge style cyl tip... So its easier to just offset both holes and voila... The only issue with that is the minimal bore diameter at which you can really rely on that style of boring bar, which in my experience, is no less than 10mm... Sure, it can be little less, but 9-10mm is pretty much the lower margin for such a boring bar type...

[@deanharris7149]

Awesome.

[@PatriotPainter]

A collet chuck would be great for that application.

[@BIGV1N]

That intro cut got me good

[@Someone_Should_Make_That]

Haha glad you enjoyed! There’s something inexplicably enjoyable about making stuff yourself instead of buying it, even if buying it may make much more sense

[@BIGV1N]

I really like your sense of humor and how information dense your vids are! I think the rawness of everything really drives home how genuine the content is as well. I'm here for it!

[@Northern_]

I know browntool sells a version of this they call the "bombsite" that fits in a half-inch egg cup style drill bushing holder. Never saw one together or used before, looks like it works well.

[@hardtailchop]

This is a great project that I've not seen elsewhere so a huge well done for innovation! I'm definitely adding this to my project list. A four jaw or collet chuck setup is almost certainly in your future for concentricity purposes, but do you know you can tap in a part in a three jaw? You don't need shims at all... Anyway, what I also came here to say was that you will probably want to remake your punch at some stage and make it out of a material that you can heat treat for proper hardness because the moment you use it to punch something harder than it is (i.e. steel) you're going to blunt that lovely pointy accurate tip. Charlotte

[@jessicamartin9146]

I like the project. Maybe cut some channels in the dia on the work surface to let light into the target area.

[@criggie]

If I could only have one chuck on my lathe, it would have to be 4 jaw independent for the versatility. But the second workholding thing would absolutely be a collet chuck and all the collets that I can get. Holding round things just becomes so much easier (as long as you have a collet to suit) Even a janktastic aliexpress unit is surprisingly workable - mine's a ER20 to Morse Taper that fits in my headstock.

[@Someone_Should_Make_That]

Good to know! I was always skeptical about no name collets. Nice to hear that there are some decent deals to be found

[@claeswikberg8958]

almost looked like there was abit of wiggle in the acrylic rod in the end. have you measured the play? good video on a good subject, would def. watch a part 2

[@jambusspeakermouse1325]

Definitely get a four jaw. That should be the next tool you buy as without it you are going to he seriously constrained on what you can do. Impressed with the shims in the three jaw though.

[@paradiselost9946]

design alterations... pop two o-rings in the base, at the inner and outer edges, and some type of piston plunger thing. suction cap :) or throw a few lil magnets in it if you only want it sticking to steel...

[@tilliesinabottle]

There is a very good section in Karl Moultrecht's Machine Shop Practice vol 1 that describes traditional hole layout. It involves using a very slight and sharp punch by hand and then moving up to broader marking tools, then a particular way of drilling to keep the hole on location. If you want I'll send an email with those pages from the book. Weather you do it that way or with an optical center punch, you can move your punch mark into the right spot (yes it can be done) so long as you can see it under magnification. With enough care you can get two holes on mark within .001" . I do this with a jeweler's visor like the optivisor. You can even set the punch into position before striking with much more accuracy when magnified that much. I suppose a low-power microscope can also let you at least see what you've done.

[@Someone_Should_Make_That]

Thanks for the information! I’ll have to look into that method

[@D3rron08]

Asd some neodymiumagnets to the base so when u are working with steel both hands are free.

[@haydenc2742]

Neat!!!

[@johnpublic168]

On the bottom surface of the punch housing mill cutouts to let light in and it will be usable on round stock.

[@hellshot1214]

yea get the 4 jaw it will help with that issue. Also good work on that. back when I was in high school that was one of the final tests that we could take for shop class. the tests was one of those , or a hand made ballpein hammer made on the lathe. went with the the ballpein hammer and still have it to this day

[@Someone_Should_Make_That]

Sounds like I’ll have to get to work on a hammer to go with this then!

[@woosier1]

If I might make a suggestion, I think you could cut down on some of the exposition regarding what camera shots you want to take and some of the stuff that you are currently doing, and just show them. Sometimes it's easy enough to see what you're doing without an explanation. I hope that's constructive. I do enjoy your content and I'm definitely looking forward to more!

[@JC-ew5ss]

Did you lathe that center punch from hardened steel or did you harden the steel after?

[@haligonian7944]

I miss the train sign that was on the wall

[@mikebeacom4883]

I was guessing you would order a small Plano-Convex lens from someone like Edmunds Scientific and glue it to the end of the polycarbonate rod.

[@philanderingwhitecollartra8281]

how about an auto punch ( could be interesting to see the slip action built) instead of hammering? sometimes the angle of impact deflects...

[@BillDavies-ej6ye]

A nice project! A 60 degree point might give a better centre mark. Did you harden the centre punch?

[@Someone_Should_Make_That]

Thank you! I’ll have to try that out. I didn’t end up hardening the punch but now that it’s confirmed in the right spot that’s a good idea

[@darylh8657]

For more brownie points, you could use a convex cutting tool to put a radius curve from 45 to 60 deg. That point should add some precision.

[@David-hm9ic]

That’s what I thought, too. I have several pieces of HSS from broken end mills that were cut down to 60 degree points and one with a very long “pointer” tip. It’s great for locating center punch marks in the mill and drill press. The carbide tools in the video will cut HSS effortlessly.

[@trollforge]

Power Fist Dial indicator, Eh? What part of the country are you in?

[@MarkATrombley]

You probably want to harden the punch. Adding an LED for light might be a good idea.

[@procyonia3654]

It's linear motion rod, usually thru hardened isn't it?

[@robertwoodcock1012]

@@procyonia3654 The linear motion rods I've used for things are case-hardened, not through-hardened. In the video he turns it and uses a file on it, so we know the inside material isn't particularly hard. If he uses it only on aluminum he'll probably be OK. BTW, you only want the tip of a punch to be hard, because the head of the hammer is hardened and striking hardened steel against hardened steel is dangerous.

[@mikemullis6862]

8mm reamer?

[@andyknappenberger7512]

A CLAW HAMMER?!

[@Someone_Should_Make_That]

Inflation hits us all in unexpected ways 😂

[@matthewrichardson828]

need an 8mm reamer

[@user-zo8mm4sb4i]

Когда коту делать нечего что он делает??

[@OutlawEdge]

Your channel is absolutely awesome! I’m glad I found it by accident. You have great content I hope you keep making videos. See you on the next video. Subbed!! 👍 ARCO-MN OUTLAW CUSTOMS (outlaw edge KZbin channel)

[@Someone_Should_Make_That]

Glad you enjoyed! Thanks for watching!