make a unibit.

[Mcgyver]

since you aren't allowed to open the purchased unibits, I figure i have to make one.

actually was in home despot thinking of buying one, $50!! I was feeling cheap so passed. Irony was whatever brand it was had some big stupid looking truck with a custom paint job and two guys sitting there in front of HD. Great promo me says to meself, the stupid looking truck and two guys sitting there, no wonder they have to sell it at a rip off price. promo completely misses its mark with crusty Mcgyver.

anyway, point of the thread is, what is the geometry of these things - where is the clearance, relief etc? anyone know or have a good pic?

thanks

[JRouche]

anyone know or have a good pic? thanks

[Mcgyver]

JR, thats perfect, thanks very much for taking the time

Its looking like the only angle I have to worry about is clearance along the lines of.....



I'm going to take shot tomorrow and making one. figure once all the dia are turned, the little cone section that that does the cutting and needs the clearance could be put on by working the lathe by hand with the carriage engage at a high feed rate. will report back

[JRouche]

Sorry, I measured that with a gage also. 90 degrees included angle. JRouche

The flat sections are parallel to the shank. The pics may show a distorted view of the flats. They are in line with the shank and the step is 45 degrees off of that, 90 total.

[wierdscience]

If I were going to make one I would use a real pilot drill for the tip to improve cutting effeciency at the start and reduce walk over.

And I would mill in pockets to accept.........carbide inserts!

Patent pending 12/1/06 Please send royalty checks to my accountant Dave Smith 5% off the take should keep me in new endmills.

[Paul Alciatore]

The rake angle is shown in RJ's third photo. It does have clearance (it has to in order to cut) and you are correct in showing a small clearance angle in the his first photo. It is only a few degrees, perhaps only 0.010" around the step.

The barrel steps are NOT relieved and serve as pilots for each diameter.

BTW, the 45* steps make excellent deburring cutters if you adjust the depth stop on your DP carefully. I drill from one side, deburring as I bottom out on the depth stop, then flip the piece over and instantly debur the other side. Works like a charm.

[PTSideshow]

Check out Harbor Frights web site and see if they have a posted instruction sheet for them. the paper that came with one of mine years ago. had you sharpening them with a stone along the cutting edges at the tip and along the opening. have followed the instructions and they have always put the hole and broe the lip in wood and plastic that I use them in.

[Paul Alciatore]

I've never sharpened one, but it seems that you should do it exactly like a form cutter (gear tooth cutter) and grind only on the cutting face. Leave the outside surfaces alone. This should be easy.

[Your Old Dog]

I posted to this thread earlier and don't see it now. Was it removed? If I said something wrong I'm sorry. It was obviously meant to be a tongue in cheek post.

[Mcgyver]

progress report,

after turning, to do the cut out, the setup requires a compound angle, collet block to angle plate 11 degrees, angle plate to t slot 11 degrees. 11 worked out to be the degree taper of the unibit. embarrassed to say its been so long since i used trig i had to google a refresher!




milling completed, used a carbine end mill so I could run it fast - I wanted a very light chip load with the is less than rigid setup, plus tool steel is a pita to cut with hss



since that shot, I've got half the relieving done (ie angle shown by white lines above). I'm doing it in the lathe manually, that is rotating the spindle by hand. I set the feed to 8 thou per rev, have the compound at 90. 8 thou is too much for one cut so i revolve the spindle back and forth by hand setting depth cut by the compound, seems to work well

will finish it tomorrow and heat treat. think I'll make a small dia one and try to find a big dia piece of tool steel, all i had was 1" drill rod. Then I have to figure out how to get it into a cardstock package