Thread tool form

[Clive BarkerParticipant @clivebarker72854]

I am just about to machine the register thread on my homemade lathe which will be the standard ML7 1 1/8in x 12 tpi 55deg form. I have made a dummy regsiter in preparation to machine the face plate thread. Before proceeding I wonder if I could improve the thread form on the dummy register – since this going to be the standard that will determine the thread form of the real register, the face plate and church back plates. Living overseas in a location with few available supplies I have no access to chasers or dies so am relying on generating the thread. In practice grinding the threading tool to a (homemade) thread gauge is not easy. By holding up to the light and trying to get the best fit with the thread gauge I am reasonably close to a 55 deg form. But, can anyone suggest how to grind a really good form tool? Thanks, Clive

[Clive BarkerParticipant @clivebarker72854]

[JasonBModerator @jasonb]

Have a read of this recent Thread, not the same angle as yours but the methods will still apply

 

http://www.model-engineer.co.uk/forums/postings.asp?th=49920

[John HaineParticipant @johnhaine32865]

The book on threadcutting in the lathe by Martin Cleeve has an excellent and simple design for a lathe tool grinding jig which will ensure correct angles.

[NobbyParticipant @nobby]

Hi Clive & Guys

What is also important is the location diameter . When threading you can also bore out the size for the depth of thread say about 3/16 deep z minus and when the tool touches this diameter the depth is correct .Then can finish the location Diameter For Myford 1&1/4″

Regards Nobby

 

[Clive BarkerParticipant @clivebarker72854]

Thanks, Jason & John for your helpful repsonses.

Jason – I had a quick look at the thread you pointed out (didn’t find that for myself when I looked before) and will return to it late to give it more time.

John – Not sure I can get the book here, but will look into it.

[Clive BarkerParticipant @clivebarker72854]

Hi Nobby,

Yes, I will ensure that I get the location dia and face right! I like your suggestion for getting the right thread depth sounds good. I need to look into to the exact dims to suit my thread.

 

Incidently it was quite a challenge to get my homemade lathe to turn faces true. Diameters were not so challenging. Since I didn’t have another machine at home the final finshing of the headstock bearing faces (outboard in my case) and the collars attached to the madrel had to achieved by hand with the help of some gauges. When finished and clocked I was happy with the result. So, I hope that I can now turn a good register. I am currently machining an 8in dia cast iron faceplate so when this it fianally installed and finish machined it will show whether I have been sucessful.

 

Thanks, C

[EddieParticipant @eddie]

Hi Clive

I can recommend the book Screwcutting in the Lathe Martin Cleeve. Workshop Practice series 3, The best book I have read about screwcutting in the lathe. As a real amateur, with no technical training. use this tool to sharpen any lathe tool on a bench grinder. In fact I have three, two used set for the left and righthand side of the thred tool, so it is a breeze to touch-up the tool, swithing between toolholders, once set no changes made.

 

The detail of the sharpening tool is also on this site, with credit to Martin Cleeve.

 

http://www.gadgetbuilder.com/ThreadingTools.html

 

Eddie

Phalaborwa

South Africa

[NobbyParticipant @nobby]

HI Guys

The tool radius is also important on Whitworth form threads . When grinding tools on bench grinderr I use a Moore & Wright No. 200 thread and setting gauge . Clive good luck with the 8″ face plate

Regards Nobby

[IanHParticipant @ianh]

Hi,

 

A few years ago I started machining threads for crank pins and main shafts in JAP engines – these are fine threads subject to very high loadings – I took the plunge and invested in some throw away tip tooling which I would say has been one of the best tooling investments I have ever made. In particular I invested in Carmex miniature and sub miniature internal threading tools and these have been a Godsend.

 

I standardised on 20TPI (although metric pitch options can be cheaper) and bought full profile tools for that pitch, but supplement this with partial profile tools allowing me to machine any other pitch I need.

 

My advice would be to invest in some decent tooling – it is worth it.

 

Ian

[Clive BarkerParticipant @clivebarker72854]

Hi Ian,

 

Thanks for your comments. Hadn’t thought of throw away tooling. When we come back to the UK for a few months may consider this. However, for the time being with limited factilities and availability of tooling I will have to stick with basic teqchiniques. C

[adyParticipant @ady]

Martin Cleeve “screwcutting in the lathe” is an excellent book and an interesting read for an amateur.

 

His own Myford lathe was extensively modified and looked like a mini-herbert production machine, this guy really knew his stuff and left us an invaluable book.

[Clive BarkerParticipant @clivebarker72854]

Eddy & Ady,

 

Thanks for suggestion to look at Martin Cleeve’s book. I looked up the tool sharpening jig on the website you suggested Eddy. When I have time will have a go at that. Will also need something to dress my grinding wheels.

 

The faceplate and 4-jaw back plate successfully turned today. Will start in the lathe mandrel next.

 

Clive.

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