Harold Hall's precision grinding table

[Bluechip]

That type of countersink / hole de-burrer or whatever is made larger than 20mm  .. here's a source if you happen to have some £140 looking for a new home .. 

http://www.engineering-supplies.com/sub/519/countersinks/

The usual included angle for a c/sink is 90 deg AFAIK, except in years gone by when 82 deg was used for 'raised csk.' or 'instrumentation head' screws ..

I don't suppose they would be difficult to make if you just wanted a special. They only appear to be a transverse hole in a bit of round silver steel stock, then machined to a point. Never made one for all that ..

Dave BC

[Bogstandard]

There is a little more to them than that Dave, they actually have a relief grind done on them.

If you look at the very tip, it should be an elliptical type of shape rather than going to a normal point.

I have resharpened mine using a half round Swiss diamond file around the edge of the thru hole, and that seemed to do the trick.

Not bad for a cheapo set of five bought about 10 to 15 years ago.


John

[Bluechip]

There is a little more to them than that Dave, they actually have a relief grind done on them.

If you look at the very tip, it should be an elliptical type of shape rather than going to a normal point.

I have resharpened mine using a half round Swiss diamond file around the edge of the thru hole, and that seemed to do the trick.

Not bad for a cheapo set of five bought about 10 to 15 years ago.


John

Hi John

Another of my illusions gone ... but I'll certainly take your word for it. Did idly look at them when I got them , and wondered how they managed to cut.

But got no further than that.

However, cut they certainly do. I find watching the thin, crinkly ribbon emerging most satisfying ...

Which probably explains the excessive depth of some of my c/sinks ....   

Dave BC

[xo18thfa]

Thanks John, Roy, and Bob.  This will give me the courage to ask another "how to use..." question on using splitting saw.  Will ask in the right thread.

Bob, you mentioned a pilot hole before countersink.  I did the hole first and then apply the countersink to it. Hope I didn't do anything wrong.

Regards,
Wong

Wongster:  I just drill a very small pilot hole first, countersink then follow up with the full hole.  If you drilled to main hole first, you'll be fine.  Just run slow speed with oil.  You'll be OK.

Those "0 flute" countersinks like someone showed are nice.  I need to get some.

Bob

[wongster]

The countersink on the plan looks to be 20mm dia and 60 degree.
but I didn't worry too much about that.
It's only got to hold on to the ball, it's not that critical. the idea is to make the sinks first then assemble the bits roughly and measure how long the bottom spacer needs to be.

Roy.

That's reassuring enough.  I'll trying using my 90-degree and give it a shot.

Thank you.

Regards,
Wong

[wongster]

Wongster:  I just drill a very small pilot hole first, countersink then follow up with the full hole.  If you drilled to main hole first, you'll be fine.  Just run slow speed with oil.  You'll be OK.

Those "0 flute" countersinks like someone showed are nice.  I need to get some.

Bob

Thanks Bob.  I'll try with the pilot hole as suggested.  From the few c/sink holes I did with full hole, the chatter and noise came on the deeper I apply th c/sink enough at very low speed.

Regards,
Wong

[wongster]

Hi Wong


See if you can get c/sinks similar to these:


http://www.axminster.co.uk/axminster-axminster-chatter-free-countersink-prod21819/

As  others have said, fine feed, low speed & oil. Although I use Rocol RTD fluid on steel.

Despite what they say, it is possible to make them chatter  a bit on stainless, but you have to really abuse them to do it.
Under normal use, they don't chatter at all.

The swarf comes out as a very thin ribbon, which can be very sharp if stainless ..   verified by experiment ...  

Dave BC

Hello Dave,

Thanks for pointing me to Axminster.  They're great folks to deal with despite my small orders.  The shank size of the 3 piece set has the largest at 10mm; perfect for my Sherline ER16 spindle!

Regards,
Wong

[Bluechip]

Hi Wong

I'm surprised you could not get them locally ... I bet they're made in the Far East.

Mine are still going strong, and they've been used a fair bit. But, as Bogs pointed out, it appears they can be sharpened.

Dave BC

 

[wongster]

Hi Dave,

I asked around those shops I frequent due to their proximity. They only carry the type I bought sometime back.  Didn't have a chance to pop by the shop Chan Man Lee that I was pointed to by a kind gentleman of this forum.  Buying on the net and getting it delivered seem the easiest option at this point; been to busy with my work.

Anyway, I'm having my 1st weekend off after 2 months. Hope to have some good quality shop time.

Regards,
Wong

[Chuck in E. TN]

I am getting ready to build this rest, using imperial measurements. I have found a few charts on the web listing metric to imperial fasteners, but nothing comparing metric to imperial stock sizes. Anyone got a reference for metal stock sizes for metric to imperial?

Chuck in E. TN

[David Jupp]

Quite a lot of metric sizes in the UK are simply imperial sizes quoted to nearest mm, or sometimes nearest round number of mm.  When we went metric, companies didn't thow away all the old imperial sizing dies.  It's been long enough now that some stock may well be 'genuinely metric' from the start.

Start from these approximations, but think carefully if there are critical design dimensions that need to be 'spot on'.

3mm ~ 1/8"  ;  12 or 13 mm ~ 1/2"  ; 25mm ~ 1"

[xo18thfa]

Quite a lot of metric sizes in the UK are simply imperial sizes quoted to nearest mm, or sometimes nearest round number of mm.  When we went metric, companies didn't thow away all the old imperial sizing dies.  It's been long enough now that some stock may well be 'genuinely metric' from the start.

Start from these approximations, but think carefully if there are critical design dimensions that need to be 'spot on'.

3mm ~ 1/8"  ;  12 or 13 mm ~ 1/2"  ; 25mm ~ 1"

That's what I did.  Did not run into any problems.  The only critical dimension is the dovetails.  You can either go "spot on" or "fit the next"

[Chuck in E. TN]

Bob (xo18thfa),

I have a noob question on the dovetails. I had it in my mind that the lower slide was 1" stock, and that's what I got. I've already cut the piece for the lower slide, so I can't return it. My question, if I make the lower slide (drawing 4) from 1" square stock, can I make up the difference with a thicker gib strip? Or do I have to bite the bullet and get bigger stock? I have already completed the slide swivel pieces (drawing 9), except for the dovetail cuts, as I have not received the dovetail cutter yet.
 
Chuck in E. TN

[Chuck in E. TN]

Never mind. Found a block of 2"x2"x3" I'm cutting down now.

Chuck in E. TN

[Chuck in E. TN]

For those that have built this table, I'm a bit confused on the parts that fit to the lower lead screw nut (drawing 16). What is the 6 mm hole at A for?
Also the parts that assemble to the lower slide (drawing 4), what fits in the 12 mm slot? The lower lead screw nut is 9 mm dia.

Chuck in E. TN

[wongster]

Hi Chuck,

Would you be able to post your machining and construction pics when you are building this?  I'll be building one when I finished the 2 jobs on hand.

Thank you.

Regards,
Wong

[Chuck in E. TN]

Well, I went back and re-read HH's assembly instructions and figured out the assembly of the lead screws.
Wongster, I'll be glad to take pictures. Haven't taken many yet, I'll get on that today.

Chuck in E. TN

[Chuck in E. TN]

I have posted pics of my progress so far:

http://s571.photobucket.com/albums/ss157/chucketn/Machining/HH%20Grinding%20table/

I don't yet have a dovetail cutter, but have one on order. I have been substituting dimensional metal for what I have in my junk box, and adjusting dimensions as I go. The leadscrews are just 10-24 screws as I have more imperial taps than metric. I only have 2 major parts left to make, the table itself, and the top slide.
I have simplified as much as I can, and probably won't make the fancy locking handles. I simplified the locking screws to bolts with a washer to fit the slots, and loctited them together. I may change my mind later and make the locking screws as HH did. I still have some tuning to do such as rounding the ends of the side arms.
Any comments/suggestions welcome.
I have enjoyed the challenge of this project, and learned a lot in spite of myself! So far, I've burned a couple of cutters, broke one center drill, and spent money on stock that was the wrong size, but still learning a lot.

Chuck in E. TN

[Bernd]

Lookin' good Chuck. 

I'll be building one of those after a couple of projects for two other people and the Shay has all the truck parts made. So it looks likeit'll be well into this years cold season. 

Bernd

[Chuck in E. TN]

I realize some of the questions I've asked on this build were obvious, but I couldn't see the forrest for the trees. I did convert stock sizes from metric to imperial, but that was an exercise in futility. I have digital calipers and a DRO on the mill. I ended up machining to the metric dimentions most of the time.
I did substitute imperial fasteners as the only metric tap I have is 6mm for the lathe. I ended up cutting most of the parts from larger stock.
So, I'm getting more comfortable with going back and forth from metric to imperial, and my machining abilities are improving. I need to work on learning speeds and feeds as I burned up most of my mill cutters. Motivation to build the milling cutter sharpening jig, huh!
All in all a fun project that taught me a lot. Lathe tool jig, first, drill jig next.

Chuck in E. TN

[DaveH]

Chuck,

Have a look at this - might help a little with the milling.

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

 

DaveH

[Chuck in E. TN]

Thanks, Dave, I truely needed that. One of the casualties was a double end mill cutter I inhereted from my late father. Sad loss. It had done many parts when all of a sudden it started spitting out very hot blue chips and I had not changed anything I was doing that I could tell.
I did have a few situations where the vise was not tight enough, and the part was sucked up in the vise and the depth of cut started getting deeper. But, when I started this project, I though I had enough experience with my equipment to know when something was not right. Wake up call!
Can you recommend a set of mill cutters for general purpose projects like we do, including slots, cleaning out for dovetails, etc.? Should I be getting carbide for roughing and HHS for finishing? Should I be using endmills for squaring/cleaning up stock or should I get a face mill?
I have copied your referred post to Word and saved it. I will now sit in the corner and study it...
Thanks again, Dave.

Chuck in E. TN

[DaveH]

Chuck,

Here's a bit on carbide mill cutters - some useful info.

http://madmodder.net/index.php?topic=4861.0

Can you recommend a set of mill cutters for general purpose projects like we do, including slots, cleaning out for dovetails, etc.? Should I be getting carbide for roughing and HHS for finishing? Should I be using endmills for squaring/cleaning up stock or should I get a face mill?
Chuck in E. TN

The above is a really good question, comments and answers could really benifit others.

Would you mind posting your question - say in TOOLS.

This way it should generate a good discussion. It is not that I don't want to answer I will, I just think it is such a good question it deserves a post on it's own.

 

DaveH