# tapping a thread in aluminium



## graduate_owner (15 Mar 2019)

Hi all,
I have a woodworking lathe with spindle threads of 1 1/2" x 8 tpi inboard and 1 1/4 " x 9 tpi left hand outboard. I want to make up a few faceplates and have taps to suit these threads. I can't imagine trying to cut threads of this size into steel, but does anyone know if it would be feasible to cut into aluminium without needing biceps like Arnie Schwartz?

Many thanks,

K


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## Trevanion (15 Mar 2019)

So long as they're good quality and sharp taps with plenty of lubrication and you've got a large enough tap wrench that's about 2-3ft in total length it shouldn't be hard going in aluminium.


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## Rorschach (15 Mar 2019)

Threads of that size really need to be done by machine, single pointed ideally.


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## Lons (15 Mar 2019)

Got to be worth a go but it needs to be at perfect 90 deg to the face or it will be useless. I guess if only a little out you might be able to true it up on the lathe later maybe.

Wood faceplates are easier, I made several when I had an old Tyme cub.


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## Robbo3 (16 Mar 2019)

I've tapped M33 in oak & beech which requires a fair amount of force presumably because of the depth of the thread. They should be about the same hardness as aluminium.
I held the work in a chuck, drilled the correct size hole for the tap, locked the headstock spindle & used the tailstock centre to keep the tap in line, then used a large adjustable spanner to turn the square ended tap with lots of backing off. I only had one tap which I think was a second. A taper tap would have been easier & as it wasn't a blind hole, would have completed the operation in one go.


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## sunnybob (16 Mar 2019)

Its all feasible even in iron. It will just take you a very long time by hand.
I suggest you find a local machine shop.


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## Phil Pascoe (16 Mar 2019)

Just a thought if you decide to have something made for you. Bearing in mind the cost diminishes quickly with additional quantities as the bulk of the labour is in the setting up it might pay you get some nuts made of the 1 1/4" x 9 (in particular, as it is the more uncommon) in hexagonal bar and sell them here or on evilbay. This is a recurring problem with that thread in particular and I'm sure people needing it would be more than happy to buy nuts so they could make their own faceplates etc. up. :idea:


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## Farm Labourer (8 Oct 2019)

If doing it by hand, paraffin is the best lube for the taps!


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## wallace (10 Oct 2019)

I don't think its as easy as just putting threads onto something to make a faceplate. A faceplate will have an un threaded portion the registers on the shaft that its being threaded onto.


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## graduate_owner (7 Jan 2020)

I was thinking of cutting the register portion first, then the tapping hole, all without removing the blank from the chuck ( Colchester master). I ought to be able to cut the thread using the lathe itself but am getting problems with this at the moment - too much slack.
I am not too worried about the register, as it is for woodturning not metalturning, but I will cut one if I can.
I will have a go at making some wooden ones first anyway, to use for disc sanding. It will be easy to change faceplates for different sanding grits.

K


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