square holes

[david lockwoodParticipant @davidlockwood10028]

Hi everyone I have just been trying to make a square hole to take some high speed steel in a boring bar I am making. This is the first time I have tried and the results are not yet good.

 >>

I have made a temporary lever feed for my top slide and mounted a tool made from an old centre drill which was the same width as the desired square hole ground with a flat down one side to the centre line with some clearance as the tool moves in and put some rake on the front to cut on its end with a pushing force from the top slide.

 >>

 The idea was to drill a hole the same width as the across flats width of the desired square hole. Then mount the tool with the flat vertical so it fits along the vertical centre line of the hole then reciprocate the tool and move it along with the cross slide until one side of the hole is square then turn it around and do the same for the other side.

 >>

So far I have managed some holes, which are definitely not round but not really square either so before I go trying any harder do I need to go right back to the drawing board and if so how does one make a square hole?

 >>

Regards David

[david lockwoodParticipant @davidlockwood10028]

[Martin CottrellParticipant @martincottrell21329]

Hi David,

 

Would it not be easier just to use round tool steel rather than square to fit a round hole in your boring bar or is there a particular reason for using square tool steel? You could try making a broach from silver steel ( I think the process has been described recently in ME or MEW) to cut the square hole or how about filing it square?

 

Regards, Martin.

[chris stephensParticipant @chrisstephens63393]

Hi DavidHi David,

The following might help, it was written some time ago to accompany a board made with all the stages needed to make a square key for a tool post. This was shown as “work on the table” at SMEE. I am posting it complete as I could not be bothered to edit it. Should make sense, if not don’t be afraid to ask questions, or you could just laugh out loud.

Chances are that the post will not appear, it has happened before or more correctly not happened before.

chriStephens

Shows how long ago it was, it talks about the last Sandown MEX

 

I don’t know how it came out for you guys but it appears as a complete male chicken-up here. How the heck do you remove it? Looked fine before I posted it.  

Hopefully it has now gone.

If none of this makes any sense, to you, that means I have managed to get rid of the offending garbage. You don’t know what you are missing

Edited By chris stephens on 22/11/2009 18:52:04

[chris stephensParticipant @chrisstephens63393]

 Sorry about before, just read “Noddy’s book of thread posting” and think I might have it “sussed” now. Heres hoping.

ChriStephens

Oh bo**ocks, I will try once more and if that doesn’t work , I shall sweam and sweam until, I am red in the face.

 

Edited By chris stephens on 22/11/2009 19:00:04

[chris stephensParticipant @chrisstephens63393]

Fifth time lucky, not bl**dy likely, I give up.
Where’s my medication?
 

 

 >>

Edited By chris stephens on 22/11/2009 19:09:38

[Tony MartyrParticipant @tonymartyr14488]

David

The task of making a square hole was (a very small) part of my apprentice test piece long ago.

I was not allowed to use the vertical slotting machine, so reproduced the same cutting action in a lathe. Using a square section of tool steel means that by turning the tool in the tool head ensures that each side is slotted at 90 degrees as long as the work is held in a locked headstock.

The problem is that unless the shortest stiffest tool is use the hole will taper in from the entry face so you have to take very small cuts and traverse the whole saddle which gives some momentum to the process.

The form of the tooli difficult to describe if you have’t worked on a slotter while cutting keyways but it is like a chisel end with about a 30 degree rake.

At least that is how I did and do it

Tony

[mgjParticipant @mgj]

Tony, I agree and in our sized holes I think you need to index round the 4 corners.

 

Whatever one does, its quite a load on the feed handwheel.

 

I have now built a slotter by Hemingway, and that works well. Its bored off the Myford nose, so its automatically at centre height. biggest job done with that was to do the internal splines on the 2 Little Samson primary drive grears, and they are 2″ long, 3/16 wide  and .150 deep – 6 per gear.

 

However I now need to buy an angle plate and drill it  so I can get it on the Chinaman..

[JasonBModerator @jasonb]

There are a few pics of a slotting tool and the bit used to make a sq hole on this page belonging to a fellow Fowler builder, though I just used a sq needle file to do the same part.

 

You could just drill a round hole with a diameter equal to the diagonal of your tool bit.

 

Jason

[david lockwoodParticipant @davidlockwood10028]

Thank you every one for your posts (and attempts) I will try again. With regards to indexing of the corners and locking the headstock the only way I can see to do it is to make a headstock dividing attachment and divide around each corner and leave the tool in the same position rotationally (rotate the work and not the tool am I right?)

 >>

with regard to calculating the amount of traverse to take the cut. If I have this worked out right the square can be seen as two right angled triangles and I would be cutting along  the hypotenuse.

 >>

The amount already removed by the drill will be the same as the length of one of the sides.

 >>

 

The traverse for each cut will be (hypotenuse minus diameter) divided by two as I am only cutting one corner at a time

 >>

If that makes any sense

 >>

Regards David

[mgjParticipant @mgj]

1. Indexing.

 

A headstoc kdividing attachemnt is a bit up market.

 

If your lathe is backgeared with 60 teeth, you need only make a lock that engages in the teeth.teh ohter way is to set hte work in a 4 jaw and use each jaw as the reference.

 

I have a dividing head, so I just bodged up a little platform for hte head, and stuck it into the back of the spindle.

 

2. Actually chomping.

 

I just made my cutter the width of the side of the square. Drill such that dia = side. Feed across to a total of 1/2 one side. Index round. The reason for doing all 4 sides is just to get a decent finish.

 

You could make the cutter 1/2  1 side and do each corner singly, but then the load on hte cutter is assymetric and it is likely to deflect. But you could clean up with a square file.

 

I have used the 1/2 side method, but only on bigger squares where the tool was rigid enough along its length.

[Ian S CParticipant @iansc]

The boring bars with square holes that i’v made have been made by hand with a file after drilling to the required dia of tte hole,being only 1/4″ not too much metal to remove.These days I use round material ie old center drills,taps etc also use these for fly cutters and have used these to cut gears.IAN S C

[CirclipParticipant @circlip]

Nother slant on this one.

 

Use a piece of square Silver Steel (Drill Rod) the size of the finished hole.

 

Turn a spigot on the end so that the spigot is the same Dia. as the square A/F using a pointy turning tool so that you get four “Crown” points at the transision of square to round.

 

  H & T and Squeeeeeeeeeeeeeeeeeeze through the hole in the Holder.

 

  Regards  Ian.

[Author]

Posts