StrayAlien
Cast Iron
- Joined
- Aug 18, 2014
- Location
- Melbourne, Australia
Hi all,
Looking to cut some acme threads - not for the SB 10L as yet, but it'll be some good practice for compound screw and tailstock screw which are both due for a refresh. I've not cut acme threads before.
Machinery's Handbook gives the root width of an acme thread as 'crest-0.0052". With the crest being '1/P * .3707' where P is the pitch.
I have a starrett acme thread gauge and if I offer up the calculated root width to each slot it is slightly too small - i can move it about in the slot. How small? About 0.005 small. If I offer up the calculated crest width then it is a nice fit in each slot. I have tried all to about 8tpi with the same result.
I am using a digital caliper that has proven to be pretty accurate so far.
So, just checking my sanity here. The gauge slots *are* meant to be root width right? It is the only thing that makes sense to me.
Why did I check? Because I ground an 8tpi HSS acme tool and it was dead nuts in angle and in slot width according to my acme gauge .... but when offering the tool to an unused portion of (what I believe to be) an 8tpi acme screw it didn't reach the thread root.
All help and advice appreciated.
Greg.
Looking to cut some acme threads - not for the SB 10L as yet, but it'll be some good practice for compound screw and tailstock screw which are both due for a refresh. I've not cut acme threads before.
Machinery's Handbook gives the root width of an acme thread as 'crest-0.0052". With the crest being '1/P * .3707' where P is the pitch.
I have a starrett acme thread gauge and if I offer up the calculated root width to each slot it is slightly too small - i can move it about in the slot. How small? About 0.005 small. If I offer up the calculated crest width then it is a nice fit in each slot. I have tried all to about 8tpi with the same result.
I am using a digital caliper that has proven to be pretty accurate so far.
So, just checking my sanity here. The gauge slots *are* meant to be root width right? It is the only thing that makes sense to me.
Why did I check? Because I ground an 8tpi HSS acme tool and it was dead nuts in angle and in slot width according to my acme gauge .... but when offering the tool to an unused portion of (what I believe to be) an 8tpi acme screw it didn't reach the thread root.
All help and advice appreciated.
Greg.