Feedscrew Material

[James BParticipant @jamesb]

[James BParticipant @jamesb]

Hi All,

I am currently rebuilding an old drill grinder, and am considering remaking the feedscrews / nuts as these are quite worn.

I wonder if anyone has experience of this, with regard to material selection? Would EN1 be adequate, or should you go for a higher grade steel? The nuts are bronze, and the thread is 5/8 x 20 TPI (which seems to be cycle thread – these are for fine feed).

Thanks,

James

[Howard LewisParticipant @howardlewis46836]

I thought that all cycle threads were 60 degree x 26 tpi.

20 tpi is a nice convenient thread for a feedscrew, since it gives 0.050"/rev. Sometimes, I use 1/2 UNF , since it is 20 tpi, for that very reason.

Howard

[Nigel McBurney 1Participant @nigelmcburney1]

Machinerys screw thread book lists British cycle threads Tpi Ranges from 24 tpi (hub sprockets etc) to 56 (small spokes) most common usage is 26 tpi (nuts and bolts etc) 20 tpi is not on the list.Some may frown but I have used EN 1A leaded for feed screws,excellent finish ,and they last a long time in association with bronze nuts, though a they will not last so long on a drill grinder unless the screw is shielded from the grinding dust

[Chris Evans 6Participant @chrisevans6]

BSCY is 26/20/and 24 TPI 60 degree angle. Things like wheel spindles on pre war bikes are 20 TPI in either 1/2" or 5/8" I sometimes have to use UNF if the correct BSCY tap is not available.

[John ReeseParticipant @johnreese12848]

I don't know the Brit steel classifications so I will be using US terminology. My preferred material for making lead screws would be 1144. It is a resulfurized steel of .44 nominal carbon content. It machines beautifully. Sometimes it is sold under the trade name Stressproof. Tensile strength is considerably greater than mild steel.

[John HaineParticipant @johnhaine32865]

I would have thought that the threads on a drill grinder would not have heavy loads or wear quickly. I'd suggest using good quality stainless studding, say M6x1 mm, and tapping brass or bronze nuts to fit.

[James BParticipant @jamesb]

Hi All,

Thanks for your posts – sorry for delay in replying.

Some more digging has revealed these are 5/8 x 20 TPI threads, BSW form – I had previously found some 5/8×20 cycle taps listed on RDGs site, which is why I had assumed they were cycle thread.

I want to keep the machine as original as possible, so I don't really want to use studding on this occasion – but a good idea for a future project.

I had been thinking of EN1, but want these to last – I couldn't find a UK equivalent to 1144, but EN8 looks to have a similar carbon content, so I have ordered a length on EN8, and will see how I get on.

Thanks again,

James

[Neil WyattModerator @neilwyatt]

EN8 is a good choice.

Neil

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