Small Boring Head Leadscrew Pitch

[electrosteam]

Hi,
I have just purchased a small boring head from a prominent UK retailer.
It was supplied as a metric 40 mm unit with a MT2 arbor.
The adjustment leadscrew thread is 34 TPI (yes, 34) with a rotary scale of 50 divisions.
The pitch is definitely less than 0.75 mm.
This makes one scale rotation 0.747 mm, and each scale division 0.01494 mm.

Do I have reason to complain to the retailer ?

For boring holes, if I use it as 0.75 mm and 0.015 mm, then I will, at least, always be a little on the small side.
Perhaps a good safety factor.

As I am in Sydney, Australia, return is not an easy option.

Happy machining,
John.

 

[b.lindsey]

John,

Were the specifications listed at the time you ordered it? Just curious.

Bill

 

[radfordc]

Anyone who can measure to .747mm will no doubt be able to use the tool effectively!

 

[steamer]

Unfortunate yes, but you could live with it now that you know the score.....adjust accordingly

Or.....make a new screw.......shouldn't be terribly difficult.....is the nut part of the slide or is it a bushing?

A bushing would be easier to alter, especially if the slide is hardened......

Dave

 

[kvom]

The error is pretty small, much less than anything that would likely cause a problem in a home shop. After 10 turns the error is still only a little more that .001".

 

[Tin Falcon]

There will always be a little error when boring whether on the mill or lathe. Lead screw/ nut wear spring in tool spring in material at times . Different material will act differently. the whole game is to know how things are working at the time sneak up on the desired dimension take spring cuts etc .
It seems like odd dimensions but if you take your time do the math and are smarter than the tool you should get the desired results.
The tool will do whatever you tell it as long as you learn its language. Bores can be cut oversize with a criterion DAMHIKT.
So your call if the tool will meet your needs. If the price was right and it is hard to return you probly need to just make it work.
Tin

 

[bob ward]

That 34 TPI/ .747mm pitch certainly seems odd. 33 1/3 TPI would be sort of understandable if the boring head were were made for the imperialists and .75mm pitch would be preferable for metric users.

But as the others have said, as long as you know what its doing, you can, with a pencil and paper at your side, make it sing your song.

 

[electrosteam]

Hi,
Thanks Guys for all the comments on this subject.

I think Bob Ward may have hit the nail on the head.
A 33 1/3 TPI with 30 divisions would be usable for imperial jobs (0.001 in), and 0.75 mm the near equivalent for metric.

Perhaps the 34 TPI is a very smart choice by the manufacturer.

No complaints,
Happy machining,
John.