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uute
10-12-2005, 12:37 AM
??s on the Eureka reliever if anyone knows. : )

First, the two ofsets appear to be 90* apart, is this correct? I only have the drawings in Ivan Law's book to go on.

Second, If one wanted to make larger cutters, say 3 in rather than 1-1/2, would you need to scale up the whole device, just double the ofsets (& enlarge other parts just enough to allw this), or just use the same offsets while enlarging just enough to carry larger blanks?

Looks like th offsets would have to double to keep same relief angles, am I thinking right?

TIA
uute

EDIT: Yea, its late. The first eccentric (larger one) carries the indexing pawl, so it obviously must be scaled to advance the indexing hub. So it is the smaller offset which controles the rate of fall-off in relief. This one must be increased for the same relief on a bigger blank. Correct?

[This message has been edited by uute (edited 10-12-2005).]

[This message has been edited by uute (edited 10-12-2005).]

John Stevenson
10-12-2005, 04:55 AM
Uute,
I have made a larger one but just doubled everything up by 2 as I wanted to make standard 1" bore cutters.

Here's a link to a small movie of mine working.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/eureka.mpg

Staged movie but until you have seen one of these working it's not obvious how they work.

One interesting thing is that it doesn't matter which way you run the lathe it will still rotate the cutter towards you because of the ratchet action.

John s.

hms50
10-12-2005, 09:06 AM
This looks like fun, what is the name of the book please?
hms50

John Stevenson
10-12-2005, 09:12 AM
Gears and Gearcutting by Ivan Law
Published by nexus special interests, ISBN 0-85242-911-8

Usually plenty for sale on UK Ebay.
http://www.ebay.co.uk

Sir John

Mcgyver
10-12-2005, 09:55 AM
very neat! are the plans etc are in this book? it looks like it could be univesal - if used with a feed can it be used to create a hob or other cutters?

hms50
10-12-2005, 12:02 PM
Sir John, Thanks!
hms50

John Stevenson
10-12-2005, 02:13 PM
Mcgyver,
Yes the plans are in the book, based on one for 1/2" diameter bore cutters.

It's a very good book this on most aspects of gear cutting. Aimed at the home shop guy it's straight forward and clear.
No pages of higher maths that you can't do sod all about anyway.

As far as I know no one has tried to use a Eureka for making a hob.
One problem is the spindle has to revolve 12 times to the cutter revolving once due to the 12 tooth ratchet action so you will have to build a 12:1 reduction into the feed.
As many DP feeds are weird, i.e. they don't work out to a full tpi dividing this by a 12:1 reduction would make some large ungainly gear trains.

Sir John.

[This message has been edited by John Stevenson (edited 10-12-2005).]

Charles Lessig
10-12-2005, 05:17 PM
<font face="Verdana, Arial" size="2">Originally posted by John Stevenson:
Mcgyver,
Yes the plans are in the book, based on one for 1/2" diameter bore cutters.

It's a very good book this on most aspects of gear cutting. Aimed at the home shop guy it's straight forward and clear.
No pages of higher maths that you can't do sod all about anyway.

As far as I know no one has tried to use a Eureka for making a hob.
One problem is the spindle has to revolve 12 times to the cutter revolving once due to the 12 tooth ratchet action so you will have to build a 12:1 reduction into the feed.
As many DP feeds are weird, i.e. they don't work out to a full tpi dividing this by a 12:1 reduction would make some large ungainly gear trains.

Sir John.

[This message has been edited by John Stevenson (edited 10-12-2005).]</font>


Dear John,
I have built a modified Eurika to cut gear hobs. The lathe feed needs extra gears since
the hob pitch has pi in it. I used a 42-44
tooth compound to approximate pi/5. There is
a problem with multiple passes and it cannot
be solved by not opening the half nuts. The
Eurika loses place when reversed. The
hob blank must be retimed each pass. My mandrel has a hexagonal shoulder next to
the ratchet for a short wrench. I also made
a special tool to release both pawls at the
same time. After making a pass I open the
half nuts and roll the carriage back and
re-egage them where ever I want. Then,turning
the lathe by hand I look for the click where
the hob is back in time. Since the ratchet
has 12 clicks the lathe feed must be 12 times
finer as well. My mandrel has a keyway to
lock the blank in place. All work except the
relieving is done on a plain mandrel. After
cutting the main thread of the hob the blank
is stained blue and put back on the Eurika.
then the tool is run against the end to mark
where the gashes need to be. After the gashes are cut on the mill the relieving can be done. The top relief is done with a square
ended tool and timing is not too critical.
The side relieving is done with a form tool
with angled sides to match the gear pressure
angle. I have made dummy hobs of
aluminum but so far none of tool steel. I
must get some proper materials and get back
on this project. Best regards, Charlie

John Stevenson
10-12-2005, 06:05 PM
Charles,
I stand corrected, in fact your name looked familiar and I see from my emails you sent me a post to this effect in December 2004.
In that post you don't mention Pi but now you do.
Can you elaborate on this further as to me it just looks like 1/12 of a normal feed.

Sir John.

Charles Lessig
10-12-2005, 06:20 PM
<font face="Verdana, Arial" size="2">Originally posted by John Stevenson:
Charles,
I stand corrected, in fact your name looked familiar and I see from my emails you sent me a post to this effect in December 2004.
In that post you don't mention Pi but now you do.
Can you elaborate on this further as to me it just looks like 1/12 of a normal feed.

Sir John.</font>

hoffman
10-12-2005, 06:30 PM
This is interesting! I have seen an attachment that moved the compound in and out as the part rotated. What is the difference it the two approaches? I can see where the eccentric deal would be more capable of some more complex geometry... I think...

Charles Lessig
10-12-2005, 06:53 PM
If the hob pitch is near 8 tpi then the lathe would need to be set 12 times finer or 96 tpi
since the lathe turns 12 times faster than the
hob. To get a more accurate pi lead a compound
of 71-113 gives a near perfect 1/5 pi. My next
step is to get some air hardening tool steel
and some stainless foil to heat treat it in.
My Eureka needed some friction packing to
keep it from turning too far when it indexed
and missing the next position. It took me a
while to get the pawels exactly the right length too. As usual, my apologies to anyone
reading this post who has never seen the
Eurika releaving device for the above gibberish. Someone should reverse engineer
the Baltzer reliever to get the 9, 12, 18, or
36 clicks that it could provide from the
same ratchet. Charlie

uute
10-12-2005, 07:40 PM
Thanks for everything guys! Especially the movie Sir John! i knew I seen somewhere here that you had built one of these.

Scaling the whole would probably be the smart thing to do, but I was thinking it is fairly robust, one might not have to upsize the ratchet section so much.

Interesting point Charlie. with a 36 point ratchet, how to control how many teeth the pawl picks up. Hmmm?

TA
uute

shapeaholic
10-12-2005, 09:10 PM
Charles:
Any chance you could post some pictures of you modified eureka?
I was puzzling on how to use one to relieve odd thread taps.

Cheers
Pete

Charles Lessig
10-13-2005, 10:15 AM
<font face="Verdana, Arial" size="2">Originally posted by shapeaholic:
Charles:
Any chance you could post some pictures of you modified eureka?
I was puzzling on how to use one to relieve odd thread taps.

Cheers
Pete</font>

My general posting skills are not very good but
I have a Eurika album on the yahoo group
mwmills2 with a lot of pictures. Taps don't
need the same kind of relieving as hobs or
form tools so a simpler device could be made.
Someone made a small Eurika for clock gears
which was mounted on a shaft from one end instead
of between centers. With that method a chuck
could be fitted to the Eurika mandrel to hold
work that was not hollow. Worm wheel hobs are
similar to taps but do need all their teeth
relieved. Taps need plain relieving only on
the ends. The rest of the tap doesn't cut much. Maybe someone here knows how tap relieving
is done. Best regards, Charlie