Set-Over Centre

[wongster]

I'm documenting my build of the Set-Over Centre from Hemingway Kit here, beside my blog, hoping to gather comments, criticism, tips, and suggestions from the helpful folks of this forum.

The Set-Over Centre is the 2nd kit I bought from Hemingway Kit.  The first was the knurling tool which I've not the confident to start working on.  Maybe after a few simpler projects I'll start my attempt.

Like most of the little projects I did, I've the drawings drawn on my notebook as 3D models so that I can visualise how things fit together.  The raw materials were cleaned up and cut to size to prepare for marking.

Enough of writing.  Time for pics...

The Slide


I measure the thickness of the steel stock and realised that it is not the 3/8" as shown in the drawing.  Same goes for the width, which is narrower than the 1" dimension given in the drawing.  I supposed these are not critical.


Cleaning one side of the stock to use as reference.


Marking out the other end to mill stock to length. This was the maiden "scribe" by my brand new Mitutoyo Height Gage.


I can't be more happy with what I saw on the caliper.  This is important to me as I've not been able to "hit the mark" on the mill since I started the hobby.  Hoping to see more accurate work!


Marking out the holes and the area to be milled. I used the permanent marker as "layout fluid". Tried shipping in Dykem but my order was held in US and can't be shipped.


Need to improve on using the punch. Would the optical punch help? Tried correcting by "moving" the punch marks as shown in some YouTube vids - not much of an improvement.


I was wondering if I should use the edge to move to the centre mark but decided to try using the Mitutoyo Centre Finder.  Not really sure of how to use it though.  With the point in the punch mark, I adjusted the handwheels on both the horizontal axes till I feel the Centre Finder smooth at the moving part. Anyone can share how this is to be used?


Centre drill...


Drilling with 6.4mm drill for 5/16" BSF.  Took quite a while to drill through.  There was quite some vibration felt during the process, prompting me to reduce spindle speed and ease the feed.


Hole done.  Not very round isn't it...


Tapping the hole.  The spindle with a dead centre was used to start the thread.


Countersink used to deburr the threaded hole.  Should I be doing this before tapping?

After finishing with the centre hole, I moved along X axis on both side of it for the 2 1/4" BSF tap holes.  The 1/4" BSF tap doesn't have a hole at the end of its shank.  So it went into the ER16 collet held in the spindle as guide.


The Z axis was lowered while the tap was turned using a wrench on the collet chuck.


Thread done and tested with a 1/4" BSF cap screw that came with the kit.  I don't have anything BSF at home to test the 5/16" BSF though.  It is meant for the threaded end of the half centre.

The surface was then cleaned of chips and oil. I redid the layout of the recessed area as the dye of the marker was washed away by the cutting oil.


I was a little nervous when milling the recess.  My last work in steel making the flycutter was quite a painful one; the Sherline mill vibrated like no tomorrow and it was really loud!


It wasn't that bad this round.  Each pass was only 0.2mm deep.  After reaching the final depth of the recess (1/16"), the slot mill was moved to open up the slot above and below the centre line at full depth but with rather slow feed and speed.  Conventional milling was used.


The recess completed.  I measured the slots and found that I've one end at 15mm while the other end is at the correct width of 15.08mm.  Is my horizontal axes not perpendicular to each other?  Also, I went 0.07mm to deep though I dialed in the correct amount.  I'll do the adjustments on the Base.


The top was drilled and tapped for 2BA setscrew, right to the 5/16" thread hole.


The setscrew installed. You can see that it is not exactly at the centre of the 5/16" thread hole.  Don't think this will cause problem.


The Slide is now completed.  I may not want to mill the radius at the 2 ends of both the Slide and Base to simplify the build.  Maye I should, to learn how this should be done.

I'll work on the Base in my next session in the shop.  One question which I would like to ask.  The 2MT arbor needs to be machined and thread 5/16" BSF.  I'm scratching my head thinking through how I should be holding the arbor.  The Proxxon lathe has a 3MT in the spindle.  My Sherline lathe has 1MT.  Do I hold it between centre?

Thanks for reading and hoping for comments to help me along.

Regards,
Wong

[Chuck in E. TN]

Get a MT3 to M2 sleve to hold your MT2 blank for threading. It can also be used for test fitting a MT2 taper if you make one with your new tool.
 
 Edit to correct spelling.

[wongster]

Why didn't I think of that!!! Thanks Chuck.

Regards,
Wong

[DaveH]

Wong,

That is a great start - it looks very good to me

If you have the scribed lines one may not need to centre punch. Just line up the "cross" lines with that 'pointy bit' and in my case with a magnifying glass, then use your centre drill 

BTW the hole looked perfectly round to me, must be the camera 

Nice photo's well posted
 
DaveH

[Xldevil]

Hello.
I've made the set over center this January.
I've not done the radius to the slight as well.
If you leave it square,it's much easier to set the center at right angle to the base of your lathe,using an engineers square.This is essentiell for turning accurate tapers.
I've also done the knurling tool from Hemingway.It has been an easy build and it is a good tool to work with.
If I could do it,I'm pretty sure,you can do it too.
I'm not very talented,but I'm stubborn,if you know what I mean.

Cheers,Ralph

[wongster]

@DaveH, thanks for the encouragement.



@Ralph, yours looks nice!  You know what, I just remembered, from looking at your pic, that I missed out the witness line across the top of the part...    For the 1/4" slots, did you mill the slots at full depth in a single pass?  I don't know if my Sherline mill can handle that and was thinking of using clamps when drilling the holes as stops so that I can mill them with multiple passes.

If I've not appointments or meetings on Tuesday night, I'll start working on the Base.  Wife will be away for meeting till late, so it will be just shop and me... 

Regards,
Wong

[jcs0001]

Wong:

Interesting looking tool and very good photos of your progress.  I've seen a simplified version of this in one of Guy Lautard's Bedside Reader books (#2) but have never given much thought to building one.

I would appreciate knowing how well it works for you (and Ralph since his is complete).

Thanks,

John.

[wongster]

John,

When I get there, I will 

Regards,
Wong

[DaveH]

Wong,

There is a bit in this about milling a slot. It may you.

http://madmodder.net/index.php?topic=4678.msg51465#msg51465

 
DaveH

[wongster]

Thanks DaveH. I had that PDF'd when I read it last year. I'll clamps to mark the limits of the slots and take the D/2 depth (0.125") as indicated in your article.

One thing I realized when milling the slot in the slide. The 3/8" slot drill I used from Sherline actually cut 0.372" instead of 0.375". Don't think that will cause any problem with the 1/4" slots I'm going to mill in the Base.

Regards
Wong

[Xldevil]

@Wong
I made the slots by multiple passes.Having a DRO on my mill,it has been an easy task.




@John
The first and only MT I have  done up to now using the s.o.c., looks pretty good to me.





Cheers,Ralph

[Fergus OMore]

Ralph,
           I notice that you have a rotary table so you can happily round off 'ends' on your work.

Cheers

Norman

[MadNick]

Good start Wong, some good questions being asked and answered.

Thanks DaveH for the link to your milling 'how to', lots in there I didnt know before.

Nick

[krv3000]

HI a Good billed I'm slowly gathering up materials to make one up my self

[wongster]

@Nick, thanks for the encouragement.

Regards,
Wong

[WillieL]

Wong,

That is a great start - it looks very good to me

If you have the scribed lines one may not need to centre punch. Just line up the "cross" lines with that 'pointy bit' and in my case with a magnifying glass, then use your centre drill 

BTW the hole looked perfectly round to me, must be the camera 

Nice photo's well posted
 
DaveH

Wong,

I also agree with Dave here. You are off to a good start.

I think center punch marks are great if you are going to use a tiny drill bit to make a guide hole for a larger drill. There is no benefit if the size of the chisel tip won't fit inside your punch mark. The chisel tip on a larger drill bit will just skid around on top of the punch mark and can wander off center. In that case, as Dave mentioned just use your scribe lines and center finder to locate the spindle to the work, and then apply your center drill.

If I am using a center punch I find I have much better control using a manual (plain) punch and tapping it with a hammer. I can never seem to push exactly straight down using an automatic center punch. It always ends up going off of my mark.   
They are great for quick jobs that don't need a lot of precision though. An optical center punch is a great addition if you have a good one. Other users have discovered that the "cheap" ones aren't very accurate and are a waste of money.

Something you might want to consider in the future, and this is just one man's opinion....
I would done those operations in a slightly different order myself. I believe I would have milled the slot in the part first, and then drilled the holes - followed by chamfering them and finally tapping the threads.

That way you aren't milling away the chamfers and threads you made previously. And doing the chamfers before threading helps to guide the tap into the hole and makes it easier for the tap to get the threads started cleanly. Any burrs raised will still be below the surface of the part, and won't rub on your other part as it slides.

Just my way of thinking anyway. I'm certainly no expert at any of this. You are doing just fine though IMO. 

[wongster]

Willie,

Thanks for the tips and encouragement.  I find the automatic ones rather hard to push down.  May be the reason why getting the mark on is a hit and miss...  The optical punches I saw on Little Machine Shop and another site don't look cheap - but cheap is relative...

Regards,
Wong

[WillieL]

- but cheap is relative...

Regards,
Wong

So true. I only meant don't buy from the bottom of the barrel. IIRC, one of the other members here bought the least expensive "import" optical punch that Enco had to offer. He said the base was missing the cork(?) washer that is supposed to hold it in place, and the base would move on the part as he was trying to hold it. I think he also said the punches were a bit of a sloppy fit in the holes in the base as well.

I believe he said another brand didn't cost much more, and was a big improvement over the economy model he first went with.
Sorry, I don't remember which one it was though.   

[Xldevil]

Hello.
The optical center punch I'm using is made by veritas tools.
It works great.
In the long term,the good tool is always the cheaper one.
Cheers,Ralph
http://www.leevalley.com/us/wood/page.aspx?p=45502&cat=1,180,42311

[jcs0001]

Ralph:

Thanks for showing the mt sample you made - looks good to me.

John.

[DaveH]

The 3/8" slot drill I used from Sherline actually cut 0.372" instead of 0.375".
Regards
Wong

Wong,
Well that is just not acceptable, worst I ever heard 
 
DaveH

[wongster]

WillieL/Ralph, the price range is rather big.  Veritas' is about $40, Little Machine Shop's almost $70 (up to 0.002"), and Travers' about $83 (up to 0.001").  I now believe in buying one time after the experience with the Height Gage which I just replaced.  The Taiwanese gage I have is not that cheap but its about 1/2 the price of the new Mitutoyo 570-312 (made in China though).  Don't know which Optical Punch to go for yet.  Will have to read more.

DaveH, I'll run some more test with a deeper slot to ease measuring with the caliper to confirm this.  One thing I observed during making the initial slot was the slot drill cut better when held in the the endmill holder from Sherline.  When I was using the the ER16 collet chuck (with 1MT shank), the surface finish wasn't impressive.  Maybe the collet chuck sticks out more to make it less rigid in the micro mill.

I'm hoping for another session in the shop this evening when my wife is away for church meeting till late.  Will be thinking of correcting the tapered slot in the Slide and see if I can mill the same width on the Base to match.  I'll try, as Norman shared, using the edges at one corner of the workpiece to layout the holes and lines instead of the centre hole.

[DaveH]

DaveH, I'll run some more test with a deeper slot to ease measuring with the caliper to confirm this.  One thing I observed during making the initial slot was the slot drill cut better when held in the the endmill holder from Sherline.  When I was using the the ER16 collet chuck (with 1MT shank), the surface finish wasn't impressive.  Maybe the collet chuck sticks out more to make it less rigid in the micro mill.

Wong,
I wouldn't concern yourself with it at the moment, go with what works.

Just to let you know I have a sherline mill and lathe. See my avatar made only on the Sherline's.
 
DaveH

[Fergus OMore]

Wong,
          By now you should have a couple of poor-ish copies of the little 'centre finder' or sort of D Bit from the other book by George Thomas.

It came from the write up on his Versatile Dividing Head which I made up some years ago. Again, this is a very worthwhile tool to gain  more machining experience but to be invaluable for all sorts subsequent worth.

I was musing- it had been a night of nights next door to a Chinese dragon display- and then innumerable courses and a disgusting lot of wine.
We all have problems   And the coff/tea needs to be stronger but you made an Ian Bradley tool. Did you realise that George Thomas took many of the Bradley 'designs' and improved on them?

Now there is a thought

Cheers

N

[wongster]

Thanks N.

Lunar New Year was towards the last week of January.  It went on for 15 days (by tradition) but most of us were back to work on the 3rd day (only first 2 days are public holiday in Singapore).  I started work on the 2nd day till 11 pm as I was scheduled on duty at a new property launch. This year was quieter with watered down festive mood in this country.

I'll spend some time reading through all the books and materials, including the 2 jpg's you sent.  My understanding should improve as time passes.

Just got home from appointments. Too tired to do anything today in the shop.  Will read instead.

Regards,
Wong