what size hole

hi all I want to cut an internal metric 1mm pitch m22 thread what size hole should I have before I cut the thread my book only goes up to 18mm

thankx kevin

If its a 1mm pitch and 22 diameter the hole should be 21mm diameter. Just subtract the pitch from the major diameter.

21mm drill size.

**LINK**

or just buy a pack of assorted holes. I use an adjustable hole, a bit more expensive but it works well.

I've got some of those packs John - but I found that I quickly used up all the common sizes and then you get left with just the "odd" sized ones!

IanT

know what you mean, I have a rusty oxo tin full of old imperial sized holes, but you never know, they may just come in one day.

I did think about boring them out John - up to the next "standard" size - but it's a lot of hassle when you can get them so cheaply at Aldi's these days - so I haven't done so yet.

IanT

I'll trade the imperial holes for some metric holes I have. Due to new age economics I can no longer find post hole size holes, if anyone can direct Me to a source I would be grateful.

I find that using a much larger hammer makes posts fit the holes properly!

Can a beginner ask a question related to this topic?

Assuming I've bore the right size hole and set up the threading tool to just touch the inner surface. How do I calculate what depth of cut to make? Is there an equation for a metric thread like:-

Depth of cut = Some fraction of the pitch

Regards,

Steve

That's probably near enough but my book gives, Major Diameter - 1.082P which allows for the flat on the crest.

Russell.

It depends on the too you are using. Does it have the correct tip radius or is it sharp? Personally, for one offs I feed in about half the pitch and then skim until the mating part fits.

The correct figure is 0.614P if you are using the correct form tool and a bit more with a sharp point.

Russell.

Edited By Russell Eberhardt on 02/06/2015 15:59:41

Thanks for the reply Russell.

I'll be using a general 60 degree vee shaped internal tool which has just enough of a tip radius for it not to be sharp. I think I'll have to convert some aluminium to swarf getting in a bit of practice. Presumably where possible I cut the female thread first and make the male thread fit it?

Steve

The next MEW will have a pull-out-and keep chart of tapping drill sizes for 75% and 50% engagement for the most used threads in 'our' sizes. For roughly 60% engagement, you'll have to split the difference.

Converted (with great anguish) to 4 A4 sheets so you don't need an A3 laminator to protect it.

Neil

Steve,

As a declared beginner you should know that there is a difference between the "depth of cut" that you asked about and "depth of thread" because most of the answers you have had refer to the latter.
Depth of thread is a fraction of the pitch that you are using and varies a little depending on the specific thread form you are trying to produce.
Depth of Cut is the amount you advance the tool at each pass across the work and will vary depending on lots of parameters, your lathe's power and size, the material you are cutting, the type of tooling you are using, be it HSS or Carbide and lots more variables but it is most unlikely that you would have a depth of cut equal to the depth of thread. In other words Don't try to cut the thread in one pass!!

Bob D

Does anyone have some metrinch holes to spare please?

Bob D,

Thanks for pointing out the difference in the terminology, I should have said 'depth of thread'. I was intending to achieve that in several passes - my little table top lathe wouldn't allow me to do anything else!

Steve

I always cut the male thread first. It's much easier to measure and see what you're doing.

Russell.

I do the opposite, I cut the internal thread, then make the male thead to fit. This is a screw cut cylinder for a Stirling Engine. Sorry not too clear, 40 mm dia, 32 TPI, steel cylinder into an aluminium cylinder head.

Ian S C