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darryl
02-04-2010, 10:55 PM
Here's something I came up with because I needed it. I don't have a set of countersink or recessing tools for FSHCS or SHCS. I have some shop made recessing bits, but not the ones I needed today. So- if this serves to remove all doubt, as the mysterious 'they' say, then so be it.

http://www.glacern.net/free_photo_upload/countersink%20tool%201.jpg

http://www.glacern.net/free_photo_upload/countersink%20tool%202.jpg

http://www.glacern.net/free_photo_upload/countersink%20tool%203.jpg

The cutting tool in this case is the piece of a bandsaw blade. It's pretty easy and fast for me to cut out a few of these shapes, and grind the slot, etc. In these pictures, I haven't finished contouring the 'inserts' yet. I'll do that using the tp grinder, which will ensure that I get the profile accurate and centered. I have need of about a dozen different shapes, so it will be a bit of time at the cutoff disc to make some blank inserts. Today, I needed to match the profile of a flat SHCS (what is it, 81 degrees or something?) plus recess the head without having the bevel show wider than the diameter of the screws head. Yesterday I needed a profile that matches that of drywall screws, since I like to use them to assemble mdf projects, etc. Same deal, I want to recess the head flush, but don't want the recess to grow wider than the head. Using a typical countersink can't accomplish this, even if the angle was right, which it isn't.

When I'm done, I'll have enough custom inserts to handle any size and profile of fastener that I normally use. Sharpening these will be easier than sharpening drill bits, plus I can just toss the insert when it's done and make another quite easily.

This was all machined as one piece as much as possible, well centered in the four jaw, then the recess for the insert was milled on each jaw in the same jig. The groove ends up being precisely in line with the shank. I'll probably leave a bit of a tip on the inserts so they can follow the screw hole- I've used this idea in the past and it works well to avoid wandering and chattering. It's not visible in the pictures, but if I tighten the screw without an insert in place, the 'jaws' will close up about 4 thou smaller than the thickness of the bandsaw blade material, so I know that it will secure an insert well enough. The slot centers itself on the screw, so side motion is eliminated, and as I said before, it's quick and easy to make several insert blanks using the cutoff disc machine I built.

The two halves of this tool will be epoxied together, including the pins and the one screw. The screw head will need to be taken down to clear the chuck, but I'll leave some of the head as an anti-spin pin. A piece of paper will be assembled with it, and will serve to wipe out the epoxy that oozes into the .004 gap between the jaws, which goes about up to the first pin.

Oh, pretty hard to get an idea of scale- the shank is just under 3/8 diameter, and the screws are 8-32.

Ken_Shea
02-04-2010, 11:10 PM
Very slick Darryl, ones again, it's true, necessity is the mother of invention.

A guy could make one of those pretty fast if you had a slitting saw, would only need the one pinch bolt then.

Black_Moons
02-05-2010, 12:26 AM
Very cool, how exactly did you setup the peice to turn that round? I assume you started with two peices and clamped them togethor and turned? Did you pin them togethor before or after turning?

You said bandsaw blade, did'nt know bandsaw blades could come as full HSS, or are you just using carbon steel? Bimetal afaik is only HSS teeth.

Are there plans to use this cutter on anything harder then aluminum? I bet it does wonders on wood, Might get caught/snaped on aluminum (with a non torque limited driver anyway), kinda looks a little whimpy for steel

What thickness bandsaw blade is that?

darryl
02-05-2010, 02:33 AM
The bandsaw blade- I was told it's all hss, not carbon and not bi-metal. How would I know though, except by using pieces of it and seeing how it behaves. It grinds a little brighter than the hss cutting bits I have, but not as bright as steel. I know it will take and hold an edge quite well, even in steel. I won't be shy to plunge this into steel, and anything softer will be fine also. Remains to be seen how well it will last in pvc, which will dull hss faster than a person would expect, but since it's only going to be doing recesses and the like, it should be fine. It is springy like spring steel, but seems stiffer actually. It will bend, but not too far or it will crack.

Thickness is .042.

Turning it round- I put both pins and the one screw between them to hold the pieces together, then centered it in the 4 jaw, which pretty much kept the other end together (the business end). I removed both pins, then I turned the outboard end up to where the screw was. Then- I turned the very end down just enough for a roller from a chain to press fit over that for about .1 inch. That kept the end together, I removed the screw, then finished the turning til all the flats were just gone. After some deburing on a flat with sandpaper, and some work on the drum sander, it was ready for gluing. I took the pictures just before mixing up the epoxy. I'll have to wait a couple days now for a full cure before I can test it.

ulav8r
02-06-2010, 10:31 AM
Solder instead of epoxy would work well. Careful application of graphite on the blade recess and sparing application of flux on the shank would assure good results.

Paul Alciatore
02-06-2010, 11:47 AM
Looks like a great tool. Good job.

I am still curious for more details about that "all HSS" band saw blade you are using. I also haven't heard of it. Where are you getting it and what is it called? What sizes does it come in? And are you using used blades or new stock?

Lew Hartswick
02-06-2010, 12:26 PM
Was it realy a "band saw" or could it have been recip. "hack saw" ?
...lew...

darryl
02-06-2010, 09:50 PM
Definitely was a bandsaw blade. I got it in one piece- this is a guess, but length was probably about 12 ft- It's 1 3/8 from back edge to the tips of the teeth, which are spaced 1/2 inch apart. It's .042 thick.

I just did a test, comparing this blade with some old bi-metal ones, and an unknown wood mill blade. All grind with the same color and spread of sparks, and I didn't see any difference either when going through the bi-metal blade. I had expected to see some difference when I hit the tooth portion, but no. Just for comparison, I pulled out a piece of chinese hss, and it does grind with noticeably duller sparks with less spread.

Maybe this blade isn't hss, but it does have a more nickel/silvery color than all the other blades. It was given to me by a local metal shop by one of the owners, who said it was hss. Maybe it's just carbon steel, maybe there's some alloy- ? I don't really know, all I know is it's pretty tough stuff. I've used it to make scrapers, and all manner of forming tools, which are basically scrapers, I guess. I've used a piece as a cutoff blade, but without side relief I can't go very deep with it.

I had planned to contour at least one of the inserts last night, but a friend dropped by with a little 'five minute job' for me to do that took three hours- don't you just love it- maybe tonite I'll shape one up and try it out.

darryl
02-06-2010, 11:53 PM
Ok, a little work with the tp grinder and the tip is ground, so is the outer diameter of the cutting insert. I ground the angles by hand 'cause I didn't see another way to do it handily. A setup with the unimat would have worked, but it's motor isn't working at this time. Anyway, here is the tool and the work it did.

http://www.glacern.net/free_photo_upload/recessing%20insert%20made%201.jpg

A close up-

http://www.glacern.net/free_photo_upload/recessing%20insert%20close%20up.jpg

The gear material is quite hard, but sawable and drillable. I managed to drill in these recesses without incident, although I had to use considerable pressure on the drill press to get the recess in the gear segments done. The epoxy held, the cutter didn't chatter at all, and the parts got hot very quickly when doing the gear recesses. The depth stop on the drill press allowed me to get to the right depth without going too deep, but only in the disc parts- I didn't get in quite as deep in the harder metal, but that will be ok. I'm not going to push my luck at this point.

The first test of the cutter was in aluminum, then in steel, then I did these parts, then I tested it in aluminum again. The last cut went in like butter.

The screw in the picture is a 6-32. Next insert will be for the 1/4 inch size- we'll see how that one goes. I'll probably try to put a bit of a wave on the angled cutting edges, offset from one side to the other. The final cut should be fairly smooth, but each cutting edge will only have to remove half as much material as it would if it was a straight angled cutting edge.

darryl
02-07-2010, 04:01 AM
Ok, now I need some help. I've got a setup for grinding the angles on the inserts, but I need to know what angle is on these heads. It's not 90, I know that- does 81 degrees sound right? Maybe I'm not looking at the right sites, I can't seem to zero in on the information. I'll keep trying- and checking back here. I'd like to finish at least one of these using this jig before I go to bed.

These are FSHCS- flat socket head cap screws. I'm probably going to start using these where they will show on a front panel or some such- or in this case where they have to be flush or lower than a surface and need to hold.

Ok, never mind, I found it. 82 degrees.

So I just went down to the shop again, set it up for 41 degrees, ground the cutting edges, and tested it. Does a beautiful job, I'm happy again.