Metric threads in wood

[Eric The Viking]

Axminster have a handy tap+die set on offer today.

It looks good value, even if the taps are cheese, as it would fill in the gaps in the 'set' I've collected down the years on a needs-must basis.

I'm wondering if M10 and M12 threads work in hardwoods (beech in particular) for odd jobs. I'm not thinking of making Moxon vices, but the occasional use in jigs where you need an adjustment of some sort. I've managed it with M6 in the past, using small bolts as adjustable stops, which is what made me wonder.

Does anyone use ordinary (intended-for-metal) taps to do this, or even dies (possibly a bit brave)?

E.

 

[katellwood]

I regularly cut m10 and m12 in hardwoods for jigs and never had one strip, in fact the last time I cut a thread I cut another thread in a piece of American White oak I put a bolt in it and tried to strip it with an open ended spanner and guess what It wouldn't strip

Go for it

 

[Walney Col]

+1 on using those sized taps in wood (especially hardwood) I do it all the time.
One thing to look out got is that they're metric course threads... metric fine thread ones would just strip.

 

[rxh]

I agree - even tapping into end grain is possible. Dies are unlikely to work.

 

[xy mosian]

You might actually make a tap from a suitable bolt. Fashion a flute along the side and off you go. Lots of clearance needed for dust etc., and I would think a slight hook form to the cutting edge.
xy

 

[Eric The Viking]

You might actually make a tap from a suitable bolt. Fashion a flute along the side and off you go. Lots of clearance needed for dust etc., and I would think a slight hook form to the cutting edge.

I usually do that when I need a "sacrificial" tap for clearing out holes, usually motorcar-related. I just hacksaw down an inch or so, in a cross pattern. It has several advantages over using a tap: there's more meat, so it's less likely to snap, but If it does snap the pieces are small and probably won't completely jam in the hole. It works brilliantly with old spark plugs for clearing out the accreted gunge if the engine has run with a loose plug (try finding a tap for a spark plug thread!). You do have to reverse out and clean the 'tap' often though.

And it does work in wood - I've done a couple of door stops that way for cupboards in scraps of Idigbo (across the grain, not end-grain). You could just use a woodscrew, but the bolt head in place looks purposeful, so people aren't tempted to just mess with it.

I like the idea of a proper tap in wood, as the thread form will be slightly deeper - with a cut bolt you just get the minimum.

 

[xy mosian]

I couldn't imagine that the thought hadn't entered your head, but if it's anything like mine they are beginning to.
I agree about the thread depth.
The finest, pitch, woodthreads I have seen have been in Box that may be worth bearing in mind. Tighter the grain the better I would think.
I assume that you are likely to either use a metal screw for the male part, or perhaps cut one in wood on the lathe. I cannot remember, from your post on screwcutting, just what thread angle you have from your cutter, is there a possiblity of a mis-match?

xy

 

[Eric The Viking]

Wasn't me Gov - I don't have a lathe!

Will do lots of screwcutting if/when I ever do though...

 

[xy mosian]

Sorry Eric, My memory miss-read Andy T. Think I need a reboot, well a boot anyway.
I have, for a sometime project, a spare cutter for one of the Axminster thread boxes. I think it was about £7. The salient point, for me is the maximum thread pitch of 5mm. Oh! blast, now I'm doubting that, I'll have to find it to measure again. Anyhow it would be wide enough for a metric thread at the sort of sizes you mention.
Of course some gauge plate a file and a fire could be a fun way of making something, if a metal die is found wanting. Then again a 'V' router cutter and suitable jig.
Have fun
xy