# finger jig problem



## guyos (17 Nov 2017)

Hello folks
I have built a box joint jig, but I am unable to get a joint that fits. I have been advised the number of cuts and turns to make but joints are too loose. I suspect that because my saw kerf is 1/8" and the rod an M10 (don't know the TPI) that could be the cause of the problem.

If I am right, is there a way to amalgamate the two by altering the turns & spins, or do I have to change the blade as I don't seem able to get a proper imperial 3/8 rod.
Your advice appreciated.

Thanks 
Guyos


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## MattRoberts (17 Nov 2017)

Are you using a gear system with the threaded rod, or just the rod? You could use a combination of gears to give you the appropriate turns (and a greater level of granularity), or you could swap the thread rod for an acme rod


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## Retire2004 (17 Nov 2017)

Guyos, in your previous enquiry you stated that you were using 3/8" rod and that 2 turns gave you 1/8". that equates to 3/8 BSW threaded rod. You are now saying that you have M10 rod which is probably 1.5mm pitch (near enough 0.059"). This means that you would need a little more than 2 turns to equate to your saw width. Have you actually measured the kerf width on the wood (with vernier calliper or feeler gauges)? It may be possible to alter the saw width slightly by turning to a different position on the arbor or strategically placed shims.
In any event, 3/8"BSW rod is readily available on ebay which is probably the best way to proceed in your case. Ideally the measured kerf width needs to be "exactly" the same as 2 turns of the thread (otherwise the combs will not assemble) and always turn in the same direction to avoid backlash.
A picture of your setup would be helpful.
Regards, Tudor


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## guyos (17 Nov 2017)

Thanks Tudor, yes when I bought the rod at B&Q I thought it was a 3/8 rod. It was the nuts that I had to use that made me twig they were M10 nuts.

My kerf is exactly 1/8 measured by calliper and micrometer.

My apology for a saw would not lend itself to any arbor adjustments.

It did take a lot of searching but I eventually found a 3/8 bsw rod of the required length on Ebay they were mostly 12" lengths.

I think that will solve the problem, 

I never knew the difference in rods made such a difference, when I measured the O/D of the M10 rod it seemed to measure 3/8". 

Once again thanks for your explanation which was most helpful, as I never had a clue.

Guyos


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## JSW (17 Nov 2017)

guyos":34i8q7fi said:


> It did take a lot of searching but I eventually found a 3/8 bsw rod of the required length on Ebay they were mostly 12" lengths.
> 
> I think that will solve the problem,
> Guyos


You'll need 3/8" BSW nuts also.


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## guyos (18 Nov 2017)

Thanks JSW


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