NEWBIE ??? re THREADING TOOL

[Tom CPM10V]

I'm a [very old] newbie who has finally saved enough pennies to set up a small shop for tinkering the rest of my daze. [Equipment to date: 15" x 50" Harrison lathe, Acer mill with 10" x 50" table, Powermatic 20" vertical bandsaw, etc.] Now I'm starting to make tool holders for the lathe. In his book "The Amateur's Lathe", L.H. Sparey strongly recommends a 'spring' threading tool. On page 82 of the 1987 reprint, he says "... well-informed persons have gone so far as to say that it is the only tool by which perfct threads can be cut in the lathe." QUESTIONS: Is he correct across-the-board? Or does it apply just to smaller lathes? Or lathes made back when he originally wrote the book in 1948? Or easily-machined materials? BOTTOM LINE: should I make this type of tool for threading on my Harrison 15 x 50 ... in primarily CRS, O-1, aluminum, and 4130?
THANK YOU for your advice and guidance. Tom

[.RC.]

Well i dunno i have had a lot more success with my carbide insert threading tool than my HSS threading tool....

The only experience with a spring holder for me is a parting off tool holder....can you spell chronic chatter...I can after using that POS

If you have a 15X50 lathe you have a lot of ridigity so it is best to use it...

[billyboy]

look in a tool suppliers catalogue and there are thread cutting tools either metric or imperial sizes these tools come with changeable tips so there is no grinding involved, i too have a harrison and i find these sort of cutting tools are far more superior to the hss tools. regarding mr sparey, i think he wrote a lot of stuff regarding the myford ML7,

[SGW]

I'm a big fan of Sparey, but I think he went a bit overboard on that statement.

[Spin Doctor]

The problem I find with most carbide inserts for threading on manual lathes is the SFM usually cannot be kept at a high enough speed to get a decent surface finish in the threads due to the faster reaction times. Hence on manual machines I still use HSS threading tools. With one exception and that is on a Hardinge Tool Room Lathe but that is a special case. But I cheat on my threading tools. I form grind them on a surface grinder



And for custom tooling and angles I use this



It can be set to any angle need and automatically adds in the side clearance. I used to have to grind my tools free hand when I was an apprentice and I think apprentices still should learn how to do it. But once you know how to offhand grind tools then the use of special fixtures a very good idea IMO.

[kap pullen]

Tom,

Sounds like a wives tail.

If they were so good, it would be a common toolbox and supplier item.

Never seen one in 35 years.

Those Armstrong tools with the circular form threading tool look nice.

Spin doctor,
Your tool looks just like this one;



Kap

[Spin Doctor]

Kap, that's because ahem, Great Minds Tend to Think Alike, (ducks from slings and arrows here)

I actually have another design that I'll post over at photobucket one of these days. Haven't made it yet but I do have all the details worked out in my head, and now in CAD





[This message has been edited by Spin Doctor (edited 01-30-2005).]

[Chester]

Tom:

Here are a couple of examples:


http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MEWA:IT


http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3867538282

If you make one, let us know if there is anything to Sparey's statement.......have often wondered.

[Spin Doctor]

I have one of these that my grandfather made in the '30s. I gave up using it a long time ago as one of the things I don't like about it is the tools all are very short. I suppose in situations where you have long thin pieces they may help but I would always worry about spingback and tool pressure. With the size Harrison you have and the rigidity it offers plus the addition of a follow rest if you have one IMO you would not need one.

[matador]

i think the springback was intentional,because the typical model engineers lathe in those days was quite a bit smaller,and therefore less rigid than nowadays.the spring gave a bit of leeway,but with modern tooling you need the opposite,i.e.no flex.i have one but never use it.i keep it only 'cause i hate throwing out tools,even old ones i have sparey's book also,and although it contains lots of good info,some parts are obviously overtaken by time.but it still keeps getting reprinted,so it must be worthwhile.


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Hans