An alternative way to cut big threads in wood

[No skills]

Interesting stuff.

For smoothing out/final fit for the threads in the 'nuts' maybe an abrasive could be used instead of an edged thread chaser. Make a second length of threaded stud to the same size/tpi - coat a few threads with cheap thin CA and sprinkle some fine abrasive powder over it, let it dry - dust off any loose powder and second coat with thin CA again.

Thread the new stud in the nut and wind it in and out etc, might work - or could be a complete waste of time. Who knows?

 

[AndyT]

Interesting stuff.

For smoothing out/final fit for the threads in the 'nuts' maybe an abrasive could be used instead of an edged thread chaser. Make a second length of threaded stud to the same size/tpi - coat a few threads with cheap thin CA and sprinkle some fine abrasive powder over it, let it dry - dust off any loose powder and second coat with thin CA again.

Thread the new stud in the nut and wind it in and out etc, might work - or could be a complete waste of time. Who knows?

Now that does sound like a workable idea!
I will give that one a try.

It would need to be less than the full diameter, or else it would not fit in the undersized hole it was intended to enlarge, but a third of the cylinder, cut down the long axis, could work.

 

[Sheffield Tony]

Did you try the linseed oil ? At the weekend a friend was proudly showing me his new thread cutting boxes/taps - rather like the ones at the top of the thread, and he reckoned a good soak on linseed oil really helped.

 

[AndyT]

Did you try the linseed oil ? At the weekend a friend was proudly showing me his new thread cutting boxes/taps - rather like the ones at the top of the thread, and he reckoned a good soak on linseed oil really helped.

It's on the to do list. I know that Douglas has used it when cutting some very neat threads. I just wanted to try the instant method first, without waiting for oil to dry - unless you mean to cut the threads while the oil is still wet?

 

[chipmunk]

Andy,
Truly fascinating.

Another suggestion would be to try diamond lapping the flat tops of your scrapers and chasers and slightly trailing them (negative rake) as you would a bowl turning scraper. A good finish is possible using bowl scrapers but light cuts are necessary on end-grain to minimize tear-out so I would have thought that it will require very gradual feed rates per pass.

HTH
Jon

 

[AndyT]

Andy,
Truly fascinating.

Another suggestion would be to try diamond lapping the flat tops of your scrapers and chasers and slightly trailing them (negative rake) as you would a bowl turning scraper. A good finish is possible using bowl scrapers but light cuts are necessary on end-grain to minimize tear-out so I would have thought that it will require very gradual feed rates per pass.

HTH
Jon

That's another useful thought. So far I've not altered any of the original angles, which would have been chosen for work on metal. The way I'm holding the tooling (ie the original Barnes tool post) naturally does not allow for tilting of the tool, but if I make up some sort of suitable hardwood block, I could design it to hold the tool better, and allow a negative angle.

My to do list is getting longer...

 

[rxh]

I had another attempt at thread making with the lathe tonight and the result was as good as one made by tap (but much slower to do). Again I soaked with thinned oil and put a chamfer on each end of the hole beforehand. I took light cuts and turned slowly, brushing motor oil inside the hole between passes of the cutter. My cutter is fairly new and has only been used on aluminium before so it is nice and sharp.

 

[Sheffield Tony]

Did you try the linseed oil ? At the weekend a friend was proudly showing me his new thread cutting boxes/taps - rather like the ones at the top of the thread, and he reckoned a good soak on linseed oil really helped.

It's on the to do list. I know that Douglas has used it when cutting some very neat threads. I just wanted to try the instant method first, without waiting for oil to dry - unless you mean to cut the threads while the oil is still wet?

I asked my friend (AndyM) what he did. He was going by the instructions that came with his threading box/tap and what he could find on the web. Not very specific unfortunately, the instructions say to soak between a few minutes and a few days in linseed or tung oil (so timing is fairly critical then :roll: ). Descriptions on the web are not much more specific, but seem to be expecting you to cut the thread straight away when the oil is wet as a lubricant, rather than cured as a hardener. For what it's worth, Andy said he soaked his for 20 minutes before threading, but thought longer would be better. Looks like some experimenting is needed !

 

[chipmunk]

I hope I'm not teaching my grandmother here but soaking with oil is a fairy well established technique for turners to improve the finish for end-grain -especially on bowls which will be finished with oil. It would be normal for this oil to be completely uncured when the cutting/scraping is done.

I think the rationale is that it just serves to swell the surface fibres so that they form a closer bundle and can support one another during the cut/scrape, rather than forming a hardened bundle, but repeated application before each cut would be more normal than a single long soak FME.

Anyway I think that the degree to which this can help, and indeed will be needed, will depend upon the "open-grained-ness" or porosity of the timber being used.

HTH
Jon

 

[condeesteso]

The off-the-shelf cutter from Axi is a good idea Andy - I sharpened mine recently and was fairly shocked how soft the steel was... but it can cut cleanly.
On the linseed soak, I first got that from Richard Maguire - a long (48hr say) immersion in 70/30 BLO/spirit (or turps just for the nicer smell). I imagined the swelling and lubrication was what mattered, never crossed my mind about it drying to harden. I'm sure RM cuts it whilst still wet, which is what I do, adding oil as cutting if necessary. I've just found that really wet is good.
I really have to investigate this more, a much coarser pitch than the Axi set is just what I need. Those Barnes lathes seem handy things (or is it the users I wonder). =D> =D>

 

[bugbear]

The off-the-shelf cutter from Axi is a good idea Andy - I sharpened mine recently and was fairly shocked how soft the steel was... but it can cut cleanly.

Given the small amount of actual cutting it will ever have to do (so edge life is a low prioirity), I will give the manufacturers the benefit of the doubt, and assume they erred on the side of ease of sharpening.

A cynic might suggest they just used cheap steel.

BugBear