boring head and tools

Now we have started looking at alternative holders, ChrisB' sketch reminds me of a style of holder I have seen that has two projecting pins that locate in the two vertical holes in the head and somehow puts the cutting edge horizontal.

I have a hazy memory that either the bar itself or a separate insert then fixes to this piece. I wonder if that was aimed at assisting with the balance issues. I cannot remember where I have seen it though.

OK. Found something similar at:

https://www.homemadetools.net/forum/improving-boring-heads-56968

Hi,

I did look at rotating the tool within the holder but the cutting geometry isn't correct.

NDIY, yes I did exactly the same thing, even down to the fact that it was a piece of MDF cut out a hole slight larger than the hole I need in the sheet of plastic.

Using the tool held vertical in the holder gives the right geometry but not the required diameter. I think I will need to run up the grinder and see what I can do with a piece of HSS, although for now I have completed the task I initially set out to do so it will have to go onto the list of things to do.

Thanks for all the suggestions.

Ian

As DC31K's picture suggests below is a Wohlhaupter UPA2 head with a side bar extension fitted to put a boring bar into a position more suited to the job in hand. This set up was to externally machine the snout casting of an Eaton supercharger to allow a reduced diameter pulley to fit (20% upspeed on the charger).

Easy to make from a square bar of silver steel.

Funny how we spend so much time 'toolmaking' to do the jobs we need to do!

Cutters for a boring head don't have to be anything special, as long as the cutting faces are correct and there is a bit of relief behind it.

This one was made from a piece of HSS steel that I was using on my lathe. Just had to grind off the corners of the square cutter to fit into the hole on the boring head.

Then I made this adaptor from a piece of round bar that will take the standard 1/2" dia. boring bars that fit the boring head. This will bore a 150mm hole is not out of balance at a slow speed. (High range, slow setting on my RF-45 mill). ( I also use a LH boring bar with replacable inserts in the side hole)

When it comes to assessing boring tool cutting tool angles and clearances I found it useful to spend a few minutes with the CAD program drawing a set of circular arcs of different radii with a boring tool shape having appropriate angles for cutting and clearance touching the inside.

Having always found visualisation of boring tool clearance angles a bit of a blind spot its really handy having a simple diagram to look at. For some reason I was never able to "get it" from a simple table of angles and minimum hole sizes although its exactly the same information in a different format.

For smaller holes the tool always seems to need a sharper clearance angle than I feel it ought to need.

Clive

Running a Boring Head in reverse, I would expect it to unscrew from the arbor.

Looking vertically upwards, on the end of the spindle, a Vertical Mill running forward rotates in an anti clockwise direction.

Viewed from the toolpost or tailstock, a lathe runs forward in an anti clockwise direction.

So, in both cases, if the tool is mounted perpendicular to the body, (parallel to the axis ) of the Boring Head, it will cut normally if used on either machine.

When the tool is mounted perpendicular to the axis of the Boring Head, to bore a large diameter, the normal tools are not suitable.

For this disposition, it would seem that the solution is to make up a tool holder, with an angled bore for the toolbit, so that the cutting edge is beyond, and below, the end of the holder. Into this angled hole, is fixed a toolbit, probably round, ground to suitable angles to cut when rotated in the forward direction.

In this way when a n existing hole, at the normal maximum of the Boring head, needs to be enlarged, the task can be performed.

Howard