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-   -   Off-the-shelf jig cones? (http://www.bikeforums.net/framebuilders/700813-off-shelf-jig-cones.html)

mudboy 12-12-10 03:14 PM

Off-the-shelf jig cones?
 
I'm about to build my first jig using 8020 extrusion. I'm looking for 3 cones for holding the head tube and top of the seat tube in the jig, similar to this http://www.flickr.com/photos/mrwright/3747714619/ I would guess that the cones can be steel, brass, or aluminum, tapered from about 24mm to 42mm. Having them tapped M6 or M8 would be a huge plus. My only machining capability is via a drill press and a bench disk/belt sander, which ain't going to cut it for what I need.

Does anyone here know of a commercial source for something like this? I found these http://www.cmmfixture.com/components...llaneous/cone/ but they are too small.

Thanks,

Pete

unterhausen 12-12-10 04:21 PM

there is a motorcycle guy that sells cones on ebay. If you search for jig cones there is another source

For some reason I hate to admit I used moog toolholders on my jig. The taper is nice and they are short. Got the idea from someone using drill chucks. Problem with a drill chuck is that they are not really made to control the two dimensions you need to use in this application. In particular, the taper is mostly cosmetic/clearance.

NoReg 12-12-10 04:24 PM

http://mechwerks.com/Jigparts.htm

The Anvil jigs don't use cones, top and bottom. And your parts need to be perfect, ie, someone needs to have a lathe, or the cones won't hold the part straight. Anvil uses a one cone system, a v-block is an alternative.

unterhausen 12-12-10 04:38 PM

anvil used to use dual cones, lots of people do. However, the puck system that Anvil uses on the lower end of the head tube is very nice, it allows much easier setting of the lower end of the head tube. The other issue with only having cones is at the seat tube. With a cone, you should have a round seat tube at the top. However, that's not possible with some lugs, which have a shoulder at the top. I have removed the shoulder on one lug, it was a pain. I have a fitting on my jig which is a sleeve on a 3/4" shaft. The sleeve fits down into the seat tube. So I have to make a different one for each tubing size I use.

I cut my tubes on the lathe, that is a lot better than most other methods.

mudboy 12-12-10 05:44 PM

Unterhausen - looks like a good, reasonably priced option -- and the set screw is a nice bonus. Can you tell me what the taper dimensions are at the top and the bottom? I just want to make sure they would work with an oversized head tube. It looks like I could bore a 3/4" hole in an 8020 L bracket and through-bolt the toolholder.

Thanks

Pete

unterhausen 12-12-10 09:52 PM

1" at the small end and 1.4" at the big end. It will hold up to 1 3/8" tubing no problem

NoReg 12-12-10 09:59 PM

as far as centering is concerned, a ball bearing is also pretty good particularly if you only use one size of head tube per bearing. If you weld it fasten to one of the poles.

Doug Fattic 12-13-10 09:10 AM

Mudboy,

I have stainless steel cones made for my laser cut and etched fixtures that fit both standard and double oversized head tubes. Their middle is tapped with M6 threads. The angle pieces that hold them to the fixture are designed to fit (and slide) on 38mm wide (very close to 1.5") pieces themselves. That means they would work on 1 1/2" 80/20. They have little outriggers on the bottom of each side that can be adjusted so the slide fit can be made to be perfect (move freely without play). They can be sold separately as well. You can see pictures on our Ukrainebicycletours website.

My machinist makes me a set of pieces for each of my fixtures. 2 cones, 1 step piece that I can use to hold the bottom of the head tube so I can measure up from the front wheel center, a bottom and top for the bottom bracket holder. The top piece of the bb holder can also double as the lower head tube holder for double oversize head tubes (for 1 1/8" steerers).

Contact me off list for more information if you think any of this might work for your needs.


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