Equally spaced holes

[VicParticipant @vic]

I’ve not yet got a RT and I need to put three equally spaced holes around a central hole in the end of a short piece of 30mm steel rod. As a section of the part will be turned down I was thinking of putting it in a ER32 hex collet block mounted vertically in my mill vice and using a stop against the outer edge of the part itself. Do you think this would work? Super accuracy isn’t required but I’d like it to be pretty good. I should add I don’t have a DRO on my mill and using manual dials looks to be a bit of a faff. Each hole needs to be drilled through, then enlarged to a precise depth so I may need to “go round” several times! Any thoughts?

[VicParticipant @vic]

[martin haysomParticipant @martinhaysom48469]

get your self a Zeus book. this and lots of other useful information in it. instead of "going around" several times you could change cutters at each position. i can not look it up for you in my Zeus book as it is at work and i am not

[JasonBModerator @jasonb]

may be better to have the stop against one of the hex block's corners but the work edge would also do. clock the round work in true and then move table to your radius, then just a case of loosening vice and turning the block 120deg. And as you say a lot less faff than compensating for back lash lots of times.

[DC31kParticipant @dc31k]

Clamp a 3 jaw chuck to the mill table and hold the hex collet block in that.

Saves clocking in the spindle. Does not require a stop. Hold a round bar in the chuck and the mill collet at the same time and clamp the chuck to the table without moving anything. Move left, right, forward or backward to the correct pitch circle radius once only.

[VicParticipant @vic]

Posted by DC31k on 28/12/2022 13:08:59:

Clamp a 3 jaw chuck to the mill table and hold the hex collet block in that.

Saves clocking in the spindle. Does not require a stop. Hold a round bar in the chuck and the mill collet at the same time and clamp the chuck to the table without moving anything. Move left, right, forward or backward to the correct pitch circle radius once only.

Yes, that sounds like a good once I find a way of clamping the chuck. Thanks.

Posted by JasonB on 28/12/2022 12:21:42:

may be better to have the stop against one of the hex block's corners but the work edge would also do. clock the round work in true and then move table to your radius, then just a case of loosening vice and turning the block 120deg. And as you say a lot less faff than compensating for back lash lots of times.

I did think that originally but I suspect using the corners of the block may prove less accurate than a stop on the workpiece itself. Collet blocks are supposed to be accurately ground but I suspect the corners are regarded as less critical?

[DC31kParticipant @dc31k]

I have just seen this:

https://www.fwt-gmbh.de/en/stationary-three-jaw-lathe-chuck-vmj

If anyone makes this for next year's JS competition, I claim 5%.

I went looking as I had convinced myself that I had once seen a square three jaw chuck designed for the same purpose. I did not find the square chuck but the one above is clever.

[JasonBModerator @jasonb]

Vic you can't say things like that without me having to go down to the workshop and check

If 0.0005"(half a thou) is good enough your your needs then the corners should be OK as that is what difference I see when my ARC one is clamped onto a ground shaft held in a 5C collet in the lathe and rotated to measure each corner.

Collet block would also ensure height stays the same which you may not get using a chuck and as you say depths are precise that may be something to think about.

Edited By JasonB on 28/12/2022 13:38:54

[JasonBModerator @jasonb]

DC31K I just use a round flange to hold my chuck to the mill or rotary table, does not have to be a square plate and usually access to at least one key hole means it does not need the angled drive. What purpose does the square plate serve over another shape?

[DC31kParticipant @dc31k]

Posted by JasonB on 28/12/2022 13:42:14:

What purpose does the square plate serve over another shape?

I do not know. As I said, it was a vague recollection of seeing a commercial one that set me off looking. It was not just the plate under, it was the whole chuck body that was square.

I have found it and it has four jaws, not three:

https://lmcworkholding.com/products/stationary-rotary-workholding/mc-super-thin-square-chucks/

[BazyleParticipant @bazyle]

You said the holes were around a central hole. Mount it in the 3 jaw on your lathe instead of the collet block. Spot holes with a Dremel clamped to the cross slide using the 3 jaws for indexing. Then drill to size on a bench drill.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by DC31k on 28/12/2022 14:23:14:

[…]

I have found it and it has four jaws, […]

.

That’s rather tidy

MichaelG.

[Chris Evans 6Participant @chrisevans6]

I have a spare three jaw chuck mounted on a rectangular plate. I can clamp to mill table or put it into the machine vise. A useful bit of kit.

[MadMikeParticipant @madmike]

Wow what a lot of advice.

So you have a mill, a vice and an ER32 collet chuck. With that simply clamp the ER32 CC in the vice. Insert your piece of steel and clamp it. Fit a DTI in a chuck in the spindle and centralise the bar you wish to drill. Then lock the table in position. Now get your Zeus book and check the co-ordinates for three holes equi-spaced around the centre. Using these you can then simply reposition the table for the correct X and V axis positions and drill away. If you want to drill the central hole do this before you move the table. It really is that easy.

If you live close to Leicester I have a RT you could borrow if all else fails.

Edited By MadMike on 29/12/2022 12:44:55

[Howard LewisParticipant @howardlewis46836]

If the need for three equally spaced holes is only a "Once only" job, Bazyle's suggestion is a good one, unless you want to buy a Rotary Table.

(Once you have one, like your lathe, you will find other uses for it ).

Merely turn up a pillar to fit between a chuck jaw and the flat of the lathe bed, so that the jaw is horizontal.

Resting each jaw in turn on the pillar will index the work by 120 degrees, allowing the holes to be spotted, to be finish drilled elsewhere.

Howard

[Tony Pratt 1Participant @tonypratt1]

The OP has a mill with dials, just crack on and get it done, 'a bit of a faff' is what engineering is about.

Tony

[VicParticipant @vic]

Posted by Howard Lewis on 29/12/2022 15:31:01:

If the need for three equally spaced holes is only a "Once only" job, Bazyle's suggestion is a good one, unless you want to buy a Rotary Table.

(Once you have one, like your lathe, you will find other uses for it ).

Merely turn up a pillar to fit between a chuck jaw and the flat of the lathe bed, so that the jaw is horizontal.

Resting each jaw in turn on the pillar will index the work by 120 degrees, allowing the holes to be spotted, to be finish drilled elsewhere.

Howard

An RT would be useful. As I mentioned in another thread I plan to buy one when funds allow.

I have used chuck jaws to drill three holes on the periphery of a part before. No need for that now as I have a spin indexer. I don’t have anywhere near the daylight but on a big mill you could mount it vertically I suppose.

[Howard LewisParticipant @howardlewis46836]

My HV6 get used with the table horizontal for radius making, or hole spacing, and vertical for gear cutting, (get theTtailstock and Division plates at the same time as the table )

This is how the HV6, is set on my elderly RF20 Mill/Drill.

To mount stisfactorily with the table vertical, the mounting slots needed to be extended. A

2MT blank arbor was bored to be a snug fit on the barrel of the Tailstock.

The Tailstock has dowel holes under the base. theyb are too small for the T slots in the Mill table, so have stepped dowels fitted. This aligns the Tailstock on the Mill table.

The HV6 is aligned across the table with a square, in a suitable position, but not clamped tightly down yet, and the 2 MT arbor fitted,..

The clamps on the Tailstock barrel are slackened, and the barrel pushed into the bore of the .2 MT arbor.

This aligns the R T across the table, so that it can be clamped down. It also aligns the Tailstock barrel vertically, so that those clamps can be tightened.

The Tailstock can now be moved along the table to give support for the arboir / shaft for the gear that is going to be cut. For gear cutting the Division Plates are used , although the three plates do not cover every division upto 100. Possibly, ,one day, I'll use the Rt to make one or more plates to fill some of the gaps (When forced by necessity no doubt! )

To centre the RT under the , a 3MT blank arbor is turned down to a snug fit in the 2Mt arbor previously mentioned.. By entering the 3Mt into the 2MT, the RT is centred under the spindle and can be clamped down.

Remember that configured in this way, there is no access to drive out a too firmly fitted 2 MT arbor, so make provision for removal from above!

Howard.

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