Member postings for Gavin Robertson

I have been reading 'Tabletop Machining' by Joe Martin as I use a Sherline lathe. Found the comments about backing off a die and the potential for swarf to wreck a new thread very helpful. At this very small scale I really can see the problem. Today I did a practice run with the advice in mind. Have not actually tested the resulting thread engagement quality yet, though with a magnifier it looks a bit better than my previous rubbish work. This latest was on just a bit of surplus CS rod of which I admit not knowing its origin.

Postscript: Today I achieved success following some of the advice. Slightly reduced diameter, chamfer on slightly overlong end, used lathe tailstock chuck to push lightly against the die to keep square and get a start. Then progress made by alternately turning headstock chuck and moving tailstock chuck forward to catch up. The start diameter and extra length made all the difference over past attempts.

Great to get so much useful advice to review and help me decide on a way forward even if a bit more trial needed on my part. Now have quite a lot of advice to work with. Just to respond to some of the questions that have been raised:-

The original CS was that supplied in the kit, the part to be threaded was turned down per drawing and my tables confirmed that PM drawing had specified the appropriate diameter. Of course, what with the scrap I ran out of bar so had to purchase material from another source in order to try again. So valid point for me to consider. When experimenting with the BA split die I reduced the core o.d. per tables and started with the die spread. At the time I had not sourced a UNF split die, hence the experiment. Certainly, these extremely small UNF/UNC dies appear harder to find in UK but I have read good reports about my proposed source so may be worth me following up if I elect to give up persisting with my solid die. Indeed I may now have worn it out or it is just a rogue as I have not had this problem with other sizes in set. So as above lots of useful comment for me to follow up.

Hello, I am fairly new to model engineering and am tackling a PM Research model lathe (my third model from PM Research as I am proceeding carefully re difficulty). Although I purchased a set of UNF/UNC taps and dies from Chronos because PM Research drawings are US imperial I have been having real trouble with the 0-80 UNF die in particular. I suspect for the price the set may not be very good quality. The issue is that the die is very difficult to engage and when it does it produces a useless thread as it is too small diameter - it is a solid die. Having consulted the book specs I then tried an 11 BA split die from another supplier and still got a rubbish thread but then re-applying the UNF die it did then engage and produced a thread though rather poor. There is some distortion but I put this down to my ham-handiness. My question is: If I can obtain another die should I go for a split or a solid die? It seems that Tracy Tools can supply either and the prices suggest could be far better quality than my original set. I am working with cs bar stock but experiments with other materials were equal failures.