Monitor Steam Engine

[sco]

WD40 is ok as a general cutting lubricant for Ally but I think you need a high pressure type for threading - I use Rocal RTD.

There is another option to get the tap out - make a miniature hole saw out of drill rod and treppan around the tap until it's released - easier in a through hole but should still work in a blind one.  You then just plug the hole and drill and re-tap.

Don't let it get to you - breaking taps happens to the best of us!

Simon.

[zeeprogrammer]

Thanks Simon.
Looks like Rocal is more common in the UK.
I see a lot of people use 'tapmagic' here. Good for both aluminum and steel?

And I'm right about not using lubricant with brass?

The drill rod/treppan is an interesting idea. I'll probably leave that as a last resort though. 
Do you harden the drill rod after making the hole saw?

Not down yet. The biggest hurdle would come if I have to remake the cylinders.
Who would want to go through another dozen or so of pages watching that again? 

[sco]

Zee,

See this page http://www.modelenginemaker.com/index.php/topic,3870.210.html for the hollow drill / trepan trick that I used when in a similar predicament.

I machine brass dry but still use the Rocol when tapping.

Simon.

[mklotz]

Hertel is a quality tap but you need to use lubricant when tapping.  WD40 is just deodorized kerosene so it's fine for aluminum.  Using something is far more important than exactly what you use.

Haven't you yet built some small tap holders according to the design shown here...

http://www.homemadetools.net/forum/tap-holders-26298

To make things easier you can safely go to 65% depth-of-thread in aluminum.  [Probably in almost anything else on a model engine; very few model threads are stressed to the point of stripping.]

[zeeprogrammer]

Here's what I was using.



Collet in mill.
Short shaft in collet.
Tap driver on short shaft.

What I was referring to earlier about the tap driver letting go...

As the tap threads, it moves down that short shaft. If I don't give enough distance for the tap driver to move along the short shaft then it loses support and any side pressure will break the tap. It's quite possible that happened here.

The short shaft interferes with the wrench if the short shaft goes in too deep. So I may have corrected too much the away.

If there's enough height with the chuck then I use the chuck to hold the short shaft. Generally though there's not enough room and I use the collet.

[Flyboy Jim]

Hertel is a quality tap but you need to use lubricant when tapping.  WD40 is just deodorized kerosene so it's fine for aluminum.  Using something is far more important than exactly what you use.

Haven't you yet built some small tap holders according to the design shown here...

http://www.homemadetools.net/forum/tap-holders-26298

To make things easier you can safely go to 65% depth-of-thread in aluminum.  [Probably in almost anything else on a model engine; very few model threads are stressed to the point of stripping.]

So Marv, lets see if I'm understanding this right.

For example: My tap drill size chart shows using a #38 (.1015) drill for the hole for a 5-40 tap. Does that give me a 100% depth-of -thread? Some % other than 100%? Then if I wanted 65% depth-of -thread I'd use a larger drill? Would I just take the called for normal size drill (.1015 in my example here)and increase that size by some percentage? And what percentage might that be?

Also would this work in other materials like brass and steel?

Lots of questions.

Thanks, Jim

PS: I really like those tap holders

[sshire]

Zee
IIRC Alum only works with carbon steel taps. I've never had success with HSS taps and alum. Could be me, though.
I'm sure I've said this before but, form taps. (I've been happy with Balax)
No chips, so one less thing to worry about. Marv is right about thread percentage.
Yes, you need a lubricant when tapping anything (perhaps not with Delrin)

And, it's not a long drive to Easton,PA

http://www.crayolaexperience.com/easton/plan-your-visit/buy-tickets.aspx

[90LX_Notch]

Interesting observation Stan.  The one time I tried Alum it failed. (Broken HSS drill bit.)

-Bob

[zeeprogrammer]

So Marv, lets see if I'm understanding this right.

For example: My tap drill size chart shows using a #38 (.1015) drill for the hole for a 5-40 tap. Does that give me a 100% depth-of -thread? Some % other than 100%? Then if I wanted 65% depth-of -thread I'd use a larger drill? Would I just take the called for normal size drill (.1015 in my example here)and increase that size by some percentage? And what percentage might that be?

Also would this work in other materials like brass and steel?

Lots of questions.

Well you're asking the right fellow.
Get ready.
Enjoy.
 

[zeeprogrammer]

IIRC Alum only works with carbon steel taps. I've never had success with HSS taps and alum. Could be me, though.
I'm sure I've said this before but, form taps. (I've been happy with Balax)
Yes, you need a lubricant when tapping anything (perhaps not with Delrin)

Hm. I hadn't known that about carbon steel taps. Are they good for steel and brass as well?
Do people have different taps for different metals?

I have to place an order anyway. If the price is right I may try one of those form taps. Same question though...good for brass/aluminum/steel?

Lubricant for brass surprises me. I was under the impression, given the idea not use lubricant when milling or drilling brass that tapping would be the same.
Why is it not?

[Dan Rowe]

Zee,
I use form taps for anything smaller than 1/8". They are good for malleable metal like aluminium brass and leaded steel. They do not use the standard tap tables. The rule of thumb for a form tap is OD- 1/2 the pitch. The rule for cutting taps is OD- pitch for comparison.

I like Balax also and most of od the ones I own are that brand.

Dan

[sshire]

Zee
I've used the form taps for aluminum, brass and 12L14. Don't see why they won't work with CRS also.
Here's the official Balax chart

http://balax.com/sites/default/files/Thredfloer-Class-of-Fit.pdf

[mklotz]

Karl (lassen wir richtig buchstaubieren),

Yes, you need to watch what you're doing and move the quill down when the tap wrench is about to escape from the guide pin.  I have a tap wrench like yours and find it way too heavy for small taps.  For those you need something with low inertia so you don't lose your tactile feel for what the tap is doing.  With my small tap holders I can always feel when I've outrun the guide pin.

Jim,


There's a program on my page, DRILL, which will compute tap drill sizes for conventional and form taps as well as other good stuff.  But, briefly,

TD = tapdrill size
MD = thread major diameter
P = thread pitch (tpi)
DOT = desired depth of thread expressed as a percentage

then

TD = MD = 0.013*DOT/P

Example: 1/4-20 thread with DOT = 55%

TD = 0.25 - 0.013*55/20 = 0.2143  which implies a #3 drill

Here are some suggested DOTs for various materials


MILD AND UNTREATED STEELS                       60-65
HIGH CARBON STEEL                                         50
HIGH SPEED STEEL                                             55
STAINLESS STEEL                                                50
FREE CUTTING STAINLESS STEEL                     60
CAST IRON                                                          70-75
WROUGHT ALUMINUM                                    65
CAST ALUMINUM                                              75
WROUGHT COPPER                                           60
FREE CUTTING YELLOW BRASS                       70
DRAWN BRASS                                                   65
MANGANESE BRONZE                                      55
MONEL METAL                                                   55-60
NICKEL SILVER (GERMAN SILVER)                   50-60


Stan,

Love it.  Trouble is, if Starrett sold crayons, they'd cost $20 apiece.  Mitutoyo crayons would cost $1 and last three times as long.

[zeeprogrammer]

 

Just saw the 'preferred by Zee'.
Should include a 'recommended by Marv'.

Marv...I don't know 'buchstaubiern'. That seems to translate to 'paper jam beers'?
Swapping the 'i' and 'e' gets me 'paper dust Irish'.

Sheesh. And I'm the one who gets pegged for bantering.

P.S. My crayons are free. I steal them from the kid.

[Don1966]

Stan,

Love it.  Trouble is, if Starrett sold crayons, they'd cost $20 apiece.  Mitutoyo crayons would cost $1 and last three times as long.

I have to agree on the price Marv, but I bought a Mitutoyo caliper and had it returned for another and when I recieved the replacement it didn't work either. This was right out of the box and I tried to replace both with new batteries with no luck. All they would do is blink. So sent it back and asked for my money back.

Don