Set-Over Centre

[wongster]

I thought I am... just need to do 1/2 the job and the rest get done on its own... 

My Sherline's blade is 0.04".  I'll use that to do the job.

Thanks Dave.

Regards,
Wong

[arnoldb]

Hi Wong

I've been quietly following along - you're doing fine, and running into all the same problems all of us faced at one point or another..

If you don't have a parting tool of a suitable width to make an undercut for the thread like Dave suggested, you can also just drill out a short section of the threads in the block - just as deep as the bit that's not screwing home - to the same size as the thread's outer diameter.
I also see that the cutting tool left a radius in the corner between the male thread and its shoulder - this will also prevent the two workpieces screwing together up to the shoulder once you have the thread sorted; you can just use a countersink (or a larger drill bit) to add an additional chamfer to the hole in the block, and that should solve the problem there.  If you make an undercut using a parting tool, you won't have this last problem though.

 , Arnold

[wongster]

Hi Arnold,

That's a good one!  I should have incorporate this while drilling and tapping the hole in the Base. Since the rod is still in the lathe, I'll try the undercut first.  Just need to figure out how I should mount the Sherline part off tool on the Proxxon QCTP.

Regards,
Wong 

[wongster]

This session is extremely short; While my wife is having her shower, I steal into the shop to do the undercut for the screw thread I did yesterday night.

The parting tool from AR Warner in use.  It was squared up using the jaw of the 3 jaw chuck as reference.

Set-Over Centre

I tested the Base on the thread after each bit of cutting done till it sit almost flash. Seemed to be so in this pic.

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Turning the chuck around to check.

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The little gap formed doesn't seem to be uniformed throughout.  The base was screwed on finger tight.  It may be the tapped hole being out of square.  I'll check again when I get home after work tonight.

Regards,
Wong

[DaveH]

Wong,

Looking good  Take your time, and that little gap, we all get that sometimes, just that we tighten it up and don't say anything. 
 
DaveH

[wongster]

Before I left home for work, I did tighten it up and the misalignment is apparent. I'll just declare it good for the time being to carry on with the project. May make the replace part(s) if there is a need to.

Regards,
Wong

[wongster]

This session stopped prematurely when I cut my right thumb while tapping the arbor.  Blood was dripping on the floor and table when I rushed to wash the wound under running water.  The pain was terrible when in contact with water.  Thank God it was just a cut.  Though a little deeper than what I normally get, it was nothing serious.  My wife, of course, nagged a little while putting on the plaster for me.

The blood started dripping off my thumb when the latex glove was removed.

Set-Over Centre
 
Back to the making of the 1/2 centre.  The 60-degree point was completed this session, after struggling to make the arbor.
 
While parting off the workpiece, the HSS parting blade snapped.  It was cutting after a while and snapped when I tried pushing it further.

Set-Over Centre
 
Another view.

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Swapping in the Proxxon part off tool. It completed the job without much trouble.

Set-Over Centre
 
After facing the end flat, I centre drill and drill about 12mm deep for the 5/16 BSF.

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Tapping the hole to hold the 1/2 centre.

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This was when I cut myself.  Notice how close the tool was to the tapping handle? My hand slipped and my thumb went on to the cutting edge of the tool.

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There was still wobble when I mounted the 1/2 centre to the arbor. I pushed on this time, facing and turning it.

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The 60-degree point was completed.  Notice that the centre is now tightly screwed onto the arbor as if they're one piece of steel.

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After running a smooth file on the face and sanding it down with fine grit sandpaper.

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I fastened it down to the mill vise to prepare to drill the tommy screw hole.

Set-Over Centre

I stopped work at this point as the wound has started bleeding again.  I will try to complete this part of the work tomorrow morning before church.  Will also attempt to harden it by using my little Proxxon Micro Torch and quenching it in water.

[DaveH]

Wong,

Nicely shown and posted, looks good, nicely made.

Sorry about your cut thumb, - try to make sure all the sharp bits are out of harms way. That goes for the dead centre in the tailstock as well because that can also cut you. 

Don't forget you don't always have to part things off, it is quite acceptable to use a hacksaw and face it on the lathe afterwards. 

It is really coming along very well 

 
DaveH

[wongster]

Hi Norman,

A little flesh, blood, and sting indeed. Not the part on pride as I've yet to reach that stage.

The proper tools you spoke about are the tailstock tape & die holder? I plan to make them.

When I was using the tailstock, I always find the top slide in the way. Do you normally remove your tool post when using the tailstock for, say, drilling or tapping?

Also, I saw some YouTube videos showing tapping in the lathe under power. Is it advisable? Anything to look out for if it is.

Thanks.

Regards,
Wong

[wongster]

Dave,

Thank you. 3 more parts left to make; 2 adjustment screws (I'm thinking of just buying them than to make them) and the 2MT arbor.

Regards,
Wong

[grayone]

Hi Wong,

I have a question as I bought the kit as well (it's sitting in a box still in my workshop 5,000 miles away unopened)  You have just mentioned possibly buying the 2MT arbour.  I assume by this comment that the MT2 comes as a piece of silver steel and not a stub machining arbour.  If this is the case I think I would also buy it as they are not very expensive and my skill level is probably not good enough yet (or ever ) to be able to make one.

Graham

[wongster]

 Hi Graham,

The 2MT arbor came with the kit with a section that can be machined.  I was referring to the 2BA adjustment screws that have to made from the supplied silver steel.

Have you come across 2MT arbor with stub of about 1-1/2" long? Planning to make set of tap & die holders.

Thanks.
Wong

[grayone]

Hi Wong

I found one in the UK at

http://www.axminster.co.uk/groz-stub-arbor-prod21342/?searchfor=340307

2 MT with a machinable end 1" dia and 1 1/2" long.

Graham

[andyf]

Wong, once you have finished the set-over centre, you shouldn't find it difficult to make your own MT2 arbor. I have enough travel on my topslide to make one, which is what I did for my die holder (it doesn't hold taps). That way, you can make the cylindrical section along which the die holder slides as long as you like. Some of my dies are small (13/16", or about 20.6mm) in diameter, so the cylindrical section had to be smaller than that. If I had bought a soft-ended arbor, a lot of steel would have been wasted getting it down to size.

Set-Over Centre

I hang the tommy bar down between the bedways, so the holder can only turn a few degrees as I crank the spindle and workpiece  by hand.

Andy

[wongster]

The 1/2 Centre was completed this morning, though much is desired when come to hardening it.  It was my first real attempt at hardening and quenching in water.  The test with a file, as described in some text I read, left some scratches on it.  I'll try the hardening part again when I completed the entire project.

The "edge" of the 1/2 found.

Set-Over Centre

Drilling the hole for tommy bar after centre drilling. The plan called for the hole to be 3/32" but I would like to use the Sherline's tommy bar, which is slightly smaller than 4mm.

Set-Over Centre

With the 4mm hole, I'm too close to the edge near the threaded portion.

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Using the Sherline's tommy bar to remove the Centre for deburring.

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Mounted to the Base to hold it in the milling vise and milling away to almost 1/2 of the taper.

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Done. I couldn't go further with the mill as the edge of the Base blocked the endmill holder

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Completed but before hardening.

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After the first attempt in hardening. I heated the job till it glow and quench it in the little contain of water. I've had a hose near by (can be seen behind the torch) to spray water as standby.

Set-Over Centre

You may be able to see the scratches caused by a file. Hardening not done right? After I completed this part, I saw GeneK's comment on not directing the flame at the tip.  Wish I read his comment before I started...

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While assembling the parts, I realized that the 1/2 Centre threaded portion extended out a little too much into the Base.

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The excess was carefully milled flush

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Another attempt at hardening was carried out before putting the parts together. The cap screws provided are a little too long. They'll have to be shortened in the next session.

Set-Over Centre

That's all the work on Sunday morning.  I'm looking forward for my next session which will likely be next weekend.

[DaveH]

Wong,

Well it is looking good 

And no blood makes it doubly good 

Well done, by the way that hole, that is what I would have called precision drilling
 
DaveH

[wongster]

Hi Dave,

The precision part was definitely not my doing... It was the drill held in the collet (ER16) 

I was surprised as how easy the silver steel can be drilled through; no chatter, just felt as if it slided in and out...  The steel used for the Base and Slide weren't the case.

Regards
Wong

[wongster]

The machining of the "softer" end of the 2MT Arbor was completed. The job was to turn down a 5/16" section and put on the 5/16" BSF thread to thread the Base on. The softer end of the supplied arbor seemed rather tough to work on with my little experience.

The 2MT arbor was fitted on a 2MT to 3MT adapter sleeve for the spindle bore. The "soft" end measured 1" in diameter. The first job is to turn this down to 3/4".
Set-Over Centre

First is to reduce the 1" diameter to 3/4". Surface finish was rather bad.
Set-Over Centre

Next is to reduce a section down to 5/16" leaving 3/16" length of the stock at 3/4".  In order to know which I should stop turning, I tried cutting a groove but parting this material turned out to be rather unpleasant.  The AR Warner's part-off tool just jammed mid way through the cut.  But what was done provided sufficent visual of the stop point.
Set-Over Centre

The section was turned down as planned but short by about 3mm in diameter.  Can't proceed as the live centre body was blocking the tool from furhter advancement.
Set-Over Centre

I don't really have a good feeling of what I'm doing on the arbor.  There was slight wobbling when the lathe was powered on.  And so the Centre Turning Accessory was brought out and put in service.
Set-Over Centre

Too much pressure on the tailstock causing excessive heat. The grease was boiling, darkening the end of the section I was working on.
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The workpiece was taken out to clean off the burnt grease and reapply fresh dose. This time, I went easy on the tailstock when applying pressure.
Set-Over Centre

After turning down to the required diameter, I tried parting off the excess with the sleeve back in the spindle bore.  It didn't work. I can feel the job flexing away from the parting blade. The spindle guard was removed and the hacksaw drafted into service.  Thank God I've only about 7.9mm diameter to saw through.
Set-Over Centre

Facing done and sharp edges deburred with a file. The shoulder was also faced making it nice and flat.
Set-Over Centre

Sherline's grooving tool in use. I find it rather expensive but it has proven itself to be a very useful tool. The groove created is the undercut for the threads. The live centre was only pressing against the stock lightly to keep the job in place.
Set-Over Centre

Threading the 5/16" BSF was next. The 3 M6 cap screws were used as grip while turning the die holder's handle. Hope they wouldn't damage the threaded holes for mounting chucks and other accessories.
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Threading completed.  I had to cut away the half formed thread near the shoulder to allow the Base to go all the way in.
Set-Over Centre

The whole works on the arbor. Next is to find a way to get the 2MT arbor out of the 3MT sleeve.
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The threaded end of the 2MT arbor is just a tad lower than the slot for easy knocking out with a wedge tool (I don't have one anyway...).
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The 5mm Allen key and a small hammer did the job of breaking it free.
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Though still short of the 2 adjustments screws, a group photo of its members so far won't hurt.
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The Set-Over Centre on its rightful place. The 2 x 5/16" have yet to be trimmed flushed.
Set-Over Centre

I'm getting excited as I'm coming to an end of this project.  Wanted to buy the 2 x 2BA screws but the shop I always frequent only have them in brass.  Maybe that will work.  Should have buy them to test than merely walking away disappointed.

I've yet to test if the centre lies up with the centre line of the lathe.  Feeling exhausted from the long boring showflat duty I was scheduled this afternoon, I decided to stop work, wash up, and do some reading before bed.  Got to get up early for Resurrection Day service tomorrow morning.

[andyf]

Nearly there, Wong!

In my experience, the soft end of some of those blank ended arbors gets a bit hard at the back end, where it joins the tapered section.

You could probably avoid the 2BA screw hunt. I think you have already drilled the holes 4mm and tapped them 2BA, with a thread pitch is 0.81mm. An M5 screw has a pitch of 0.80mm, and the tap drill is 4.2mm. You could run a 4.2mm drill down the holes and follow it up with an M5 tap. The tiny difference in thread pitch would disappear in the process. M5 screws will be easier to find.

Andy. 

[wongster]

Andy,

I will make the 2BA screws to complete the project.  If I screwed up making the screws, I'll use the M5 cap screws.  Thanks for sharing.

Regards,
Wong

[DaveH]

Wong,

Well you are nearly at the finish post. Looking good 
 
DaveH

[wongster]

Quick check done to see if I've the centre at the correct height

Set-Over Centre

This pic doesn't show anything useful. Posted as it looks nice to me...

Set-Over Centre

I bought some 2BA screws for testing. If they work as intended, I will cut short the project and call it complete. Will try to cut a 1MT taper to make a holder of sort for the Sherline mill.

Regards,
Wong

[DaveH]

Well that looks good Wong 
 
DaveH

[ozzie46]

   Well done Wong.   

   Ron

[wongster]

Dave & Ron, thank you.

The point looks kind of rough.  Should I setup my proxxon rotary tool in the lathe to grind it smooth?

Update:
I managed to find some 2BA cap screws yesterday.  All rusted as there have not been any enquiry on it for the past few years, according to the shop assistant.  They're a little long (1-1/4") but still usable.  I tried it on yesterday night and they work as intended.

Set-Over Centre

I'm thinking if I should make a 0MT dead centre for my sherline tailstock just to test if I know how to use this set-over centre.  Or maybe a 3/8" shank endmill holder for the tailstock to flatten the bottom of blind holes after drilling.

Regards,
Wong