What is it?

[BobL]

Here's some close up's of something I've been working on and off for a while. Got a bit rushed so my drilling aint too straight on the capstan.

The last photo should give it away.
469086 469087 469089 469090 469091

[Skew ChiDAMN!!]

A modification of the VCR's head to allow it to eject toast, biscuits and small plastic animals when inserted by the rugrats? :rolleyes:

[Wood Butcher]

Is it a jig used to aid the filing of the teeth on a saw?

[ozwinner]

Indexer?

Al :)

[BobL]

Ozwinner you are . . . . the winner !!

Photos 1&2 shows the indexing jig in its entirety. You can see it's basically an Al frame that rides on a saw sharpening vice I made using taps as clamps. The jig frame and the vice, support a capstan connected to a 36" long threaded rod which in turn drives a telfon face systematically at right angles along the edge of the prospective saw blade. So when the captstan is turned a fixed amount, the threaded rod drives the telfon face a predetermined amount along the edge of the saw blade and then using a triangular file one can butt it up against the telfon face and file a tooth mark onto the blade (See photo 3).

The 5/16" threaded rod is 18 TPI. If I rotate the capstan by 360 degrees and then mark the blade with a file each time, this creates 18 marks per inch. If I grab a capstan handle at the same starting angle every time and rotate it by a predetermined number of turns and onto a predetermined position (ie straight up) I can systematically make a different set of markings per inch. It sounds complicated but it works. As well as whole numbers of turns there are 12 capstan handle positions to choose from (ie 1 every 30 degrees) so there is plenty of scope for different marks per inch. The setting used for the marks in these photos is 16.6 TPI - which is 390 degrees (1 full turn, plus one capstan handle position).

Unfortunately 18 is not all that divisible by 12 (capstan handles) but who cares whether you have 14.0 TPI or 14.4 TPI, its the consistency that counts. With 12 capstan handles and 18 TPI rod one can reasonably accurately mark the following marks per inch:
24.0, 21.6, 19.6, 18.0 (360 degrees) 16.6, 15.4, 14.4, 13.5, 12.7, 12.0 (540 degrees), 11.4, 10.8, 10.3, 9.8, 9.4, 9.0 (720 degrees), etc

I'll now use it in a few saw constructions and see how it goes before prettying it up.

Cheers

[Wood Butcher]

Bob, sort of what I thought but I was thinking a bit to complex it seems. (Its always the simple answer:()

One question, how does the teflon stand up to having the file rubbed against it? Do you think it will wear too much? or not really a problem for your purposes?

[BobL]

Bob, sort of what I thought but I was thinking a bit to complex it seems. (Its always the simple answer:()

One question, how does the teflon stand up to having the file rubbed against it? Do you think it will wear too much? or not really a problem for your purposes?

I guess I am experimenting. I found this bit of teflon in the scraps bin at work. Its the hardish form of teflon (PTFE) and it will wear but not much during the indexing of one saw. It's also not as though I plan to make dozens of saws and it's held on with a couple of self tappers so if it wears too much I'll just replace it (now that I think about it I'd better check the scraps bin). I find most of my Al bits in the scrap bin as well.

[Schtoo]

BTDT.

I used gears to drive the leadscrew myself. Ended up needing 8 1/4 turns to get 16tpi, so I think I went a tad too far. ;)

The teflon will probably wear more than you think, but it prolly won't matter very much anyway. Consistancy as you say, and all that. I used a piece of hardwood as the guide on mine.

Mine needs rehashing since it's limited in size.

I can get a v tipped steel grinder disc that's diamond dusted, I think I 'll try and wangle something around that next time, should make pointing a saw blank too easy. :)

[Mirboo]

Great idea Bob. I like it.

[BobL]

I've also thought about insetting a small roller bearing into the teflon surface so the file slides across that. The one I have is a bit too big so I'm looking around for something smaller.

[rwbuild]

I've also thought about insetting a small roller bearing into the teflon surface so the file slides across that. The one I have is a bit too big so I'm looking around for something smaller.


Bearing off a router bit?