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Allan Waterfall
02-16-2005, 02:19 PM
General view
http://img.photobucket.com/albums/v214/Greenlathe/Stent/No2.jpg

Close up and part done "Stent"
http://img.photobucket.com/albums/v214/Greenlathe/Stent/No1.jpg

The rack should be 3/8" square when it's finished.I shall either mill the surplus away or cut it off with a slitting saw.

As it's set up at the moment I shall just get the last tooth done before the rack hits the chuck.

Allan

[This message has been edited by Allan Waterfall (edited 02-16-2005).]

Mike Burdick
02-16-2005, 02:46 PM
Allan,

Thanks for posting the pictures!

- Mike

sandiapaul
02-16-2005, 02:52 PM
Nice pics Allan! What is the blue box in the upper right corner of the 1st pic? DRO, VFD control, something not even realted to the lathe? Those with the same lathe want to know!

Allan Waterfall
02-16-2005, 03:10 PM
That blue box is a VFD,it's got a card taped to the front with the speeds marked every 5hz jump.The white knob in the middle is a pot for varying the speed.The toggle switch on the right of it is forward and reverse.

The small silver box showing under the tailstock handwheel and sticking out of the back in the second pic are the sensors for the dro. The dro on the lathe is a wire return type,there aren't any scales as such.

The horizontal rod under the cross slide handwheel has a micrometer adjustment on the end and trips the spring tensioned half nut lever for turning up to a shoulder or stopping at the end of a thread.No problem threading at 200rpm if required,but now I've got the VFD I tend to thread a bit slower.

The brown box standing on the floor at the RH end is full of selected and weighed balsa wood,but I've not glued any together since I bought the lathe.

Allan

JCHannum
02-16-2005, 03:31 PM
Nice work. Do you have any info on the Stent? It looks like a decent machine, less intimidating and more down to earth than the Quorn.

Allan Waterfall
02-16-2005, 03:51 PM
JC...

I got the drawings and castings from Blackgates,I know they still do it but I can't find it on their site.
The drawings might not be too bad postage wise,but I would think the castings would be very expensive to ship.

http://www.blackgates.co.uk/

Allan

matador
02-16-2005, 04:58 PM
great job,allan.i'm in the same boat re the balsa.engineering has taken over,although i do still go flying once a week,sport flying only.
i have the plans for the "matador 60"engine,so it's somewhat related to model aeronautism http://bbs.homeshopmachinist.net//biggrin.gif.keep us informed about the stent,it looks a very useful and workmanlike machine.

------------------
Hans

speedy
02-16-2005, 05:31 PM
Nice project Allan. What are the essential differences between the Stent and the Quorn?

Your Myford looks nice also! not in the least like mine http://bbs.homeshopmachinist.net//biggrin.gif

cheers, Ken

Allan Waterfall
02-16-2005, 05:42 PM
Speedy....

As far as I can see the Quorn is for masochists who like to show them at model engineering shows to try and prove how much better than the rest of us they are. http://bbs.homeshopmachinist.net//biggrin.gif Also has a million ball handles to impress people.

I thought I might also be able to use the Stent as a small surface grinder,the front table will have the rack under it for quick "to and fro"

I was told that the Stent is like a small Clarkson T&C grinder.

I only put the pic of the Myford in so you would have an idea of what one looks like and could see what bits go on each end and what goes in the middle. http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

Allan

IOWOLF
02-16-2005, 05:48 PM
Thrud must have a quorn,then.

Spin Doctor
02-16-2005, 08:18 PM
Allen what are you using to maintain your circular tooth thickness.

aboard_epsilon
02-16-2005, 09:49 PM
How are you advancing the rack for each cut ...
looks to me that you are just moving the carrage along .
I cant see.
but me not knowing how .
I would do it this way as foillows.
would make some sort of vice device with a tooth of the same profile that engauges into the rack.....then advance the rack along moving one tooth at a time ...clamping prevousely made tooth with vice ...and on and on
but I see problems strait away with this method /idea of mine in that after cutting the first tooth the vice would be in the way for cutting the second tooth.
thats unless you put in a dummy peice of rack...and use this for the first five inches or so..buted up against the new peice of rack.
or maybe have the vice clamping from underneath with barely anything but the vice tooth from above, enguaging..

my above besides you look to be getting perfect results Allan..well done.

ps I need to make a new rack for my smart and brown lathe .......cant use the lathe method.as I dont have that-there fancy milling attatchment.
and the original rack apears to be made out of stainless...
At this time NOW.. I'm building a copying attachment for my bridgeport that uses MR Ewens idea of the conrod.....but different idea on how it is used.
by chance I found a conrod that has the same diameter big end as my bridgeport quill.
maybe I can use my copier with an endmill ground down to the same profile as the rack teeth .
we will have to wait and see.
all the best..mark

[This message has been edited by aboard_epsilon (edited 02-16-2005).]

Spin Doctor
02-16-2005, 10:55 PM
<font face="Verdana, Arial" size="2">
by chance I found a conrod that has the same diameter big end as my bridgeport quill.
</font>

What motor, just curious

aboard_epsilon
02-16-2005, 11:16 PM
He did tell me what motor it was out of .
but i have forgotten.
I do remember that it was a four cylinder diesel.......and pssibly out of a crane engine from the 40's or 50's .....he has three more of these conecting rods with the pistons still attached .....but they were nowhere to be seen.
he is having a look for the rest.
PIC BELOW

http://img.photobucket.com/albums/v190/aboard_epsilon/conrod.jpg

All the best..mark

Thrud
02-17-2005, 04:35 AM
Allan
Nice Myford, nice Stent.

I thouroghly believe I the KISS principle myself. The quorn is a PITA to build lift & turn handles and split pins (as Stephan (SGW) has mentioned many times) are the only way to nake that hing and not go insane. I hate ball handle - always have - I really hate making them - I charge triple for pissing me off and forcing me to make them...

IOWolf
No, I have no Quorns - why, do you want me to build you one? $6,000(US$) wire tranfer or certified funds - complete with hardwood case and accessories - email me for payment details. Traditional color is Myford Green - like Allan's lathe. Diamond and CBN Cup wheels included in price.

Allan Waterfall
02-17-2005, 06:51 AM
Spin.....
I'm not sure what you mean by circular tooth thickness,it's a commercial cutter.The depth of cut is 0.108"
Mark....
What I do is,
1....Cut first tooth by raising the vertical slide.
2....Lower rack below cutter and move carriage 0.157" to the left.
3....Raise vertical slide again.
4....Keep repeating .

All the carriage movements are written down in increments of 0.157" on a bit of paper,I use the dro to keep track.The cross slide is locked,each tooth is done full depth in one slow pass.The carriage is locked before each cut.

The whole arbor was made so that I can just get the 9" long rack in between cutter and chuck,without unclamping the rack.

Allan



[This message has been edited by Allan Waterfall (edited 02-17-2005).]

speedy
02-17-2005, 07:07 AM
<font face="Verdana, Arial" size="2">Originally posted by Allan Waterfall:


I only put the pic of the Myford in so you would have an idea of what one looks like and could see what bits go on each end and what goes in the middle. http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

Allan[/B]</font>
Your ever so helpful as always Allan, thanks so much!
I have stored the images in "Documents- things to do at a much later date" and printed out also to display above the Myford parts bins http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

cheers and stay well,
Ken

Spin Doctor
02-17-2005, 07:15 AM
Allen Circular Tooth Thickness is the distance between the centerline of each tooth at the pitch line. In your case .157 or 20 DP

Mark, it almost looks like one could build a tracering attachment using one of those. Manual of course and only in the vertical axis

[This message has been edited by Spin Doctor (edited 02-17-2005).]

Guero
02-17-2005, 07:39 AM
Beautiful work, Allan. Always makes me happy to see somebody else's Myford as well, especially when they've set it up for a specific job.

IOWOLF
02-17-2005, 08:21 AM
Sure Thrud, Start right away, Your check is in the mail.

Sorry, I have 2 good sharpeners,and I have less than $100 in both.
I could post pics If you want.

webowser
02-17-2005, 04:55 PM
Perhaps I shouldn't mention this but, a involute gear cutter doesn't produce the proper profile for the teeth on a rack. On a rack the sides of the teeth are straight and they're angled at the mating gear's pressure angle. You may find that the teeth don't mesh as well as you expect, but it might not make much difference. (Just my two cents worth.)

Bill

John Stevenson
02-17-2005, 05:36 PM
Cutter number 1 cuts from 135 teeth to a rack.
Technically it's only correct for the 135 tooth form but at these large numbers it's hard to differentiate.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/1RACK.jpg

This is a geometrically correct drawing of one totth of a 20 DP 135 tooth gear and rack.
the gear is in red, the rack is in black.
Note the very small differences between the two profiles.
In this case the differences are actually less that a number 5 cutter which cuts from 21 to 25 teeth.

John S.

garyphansen
02-17-2005, 06:05 PM
Question? Couldn't the tooth form be generated in a lathe as a thread, then the threaded rod could be milled, sliced with a band saw, grounded with a surface grinder or cut down with a shaper? After cutting it down, it could be split down the center and you would end up with two racks for the price of one. No need to worry about indexing.
Gary P. Hansen

torker
02-17-2005, 07:44 PM
Gary..No matter how you did it on a lathe you'd be dealing with a helix...his gears are probably straight tooth spur gears. It takes very little helix angle to interfere.
Russ

garyphansen
02-18-2005, 02:25 PM
I would not expect the slight helix to cause a problem. Gary P. Hansen

Allan Waterfall
02-18-2005, 02:39 PM
Am I missing something here...

I cannot for the life of me see how to turn a rack in a lathe.Anything turned is circular and regardles of how you cut and dice it,it's bound to have a curved surface.All the racks I've seen have a flat top.

Allan

IOWOLF
02-18-2005, 05:11 PM
ALLAN, SEE THE PIC.

Allan Waterfall
02-18-2005, 05:17 PM
What pic? Is there a pic of a rack turning in a lathe that I've missed?

Allan

zl1byz
02-18-2005, 05:56 PM
Allan, very good work there.

Mark, I was thinking if you wanted to do a rack in similar fashon but dont have the milling attachment. What about making a jig to hold the rack on the top slide pointing up to pass under the cutter. Use shims to get the correct depth.
Another thought. Has anyone made an angle block to re orientate there top slide vertical and used that as a mill attachment?

John.

IOWOLF
02-18-2005, 06:13 PM
SORRY,Allan I missunderstood the Question.

Evan
02-18-2005, 06:18 PM
John,

Funny you should ask.

http://bbs.homeshopmachinist.net//Forum1/HTML/004176.html

zl1byz
02-18-2005, 06:28 PM
<font face="Verdana, Arial" size="2">Originally posted by Evan:
John,

Funny you should ask.

http://bbs.homeshopmachinist.net//Forum1/HTML/004176.html</font>

Evan,

Probably unconsciously were the idea came from. http://bbs.homeshopmachinist.net//smile.gif

John.

Spin Doctor
02-18-2005, 07:18 PM
<font face="Verdana, Arial" size="2">Originally posted by Allan Waterfall:
Am I missing something here...

I cannot for the life of me see how to turn a rack in a lathe.Anything turned is circular and regardles of how you cut and dice it,it's bound to have a curved surface.All the racks I've seen have a flat top.

Allan</font>

One of the regular jobs we had was for a circular rack in a clamping fixture. The tooth form was a true 20D PA rack only cut around the part. Still required very careful movements of the saddle and cross slide. IIRC the depth was controled by miking over pins

John Stevenson
02-18-2005, 07:32 PM
Spin,
Surely a circular rack would be a gear ?
I have made many quadrant gears for rise and fall tables and these were just parts of gears and followed all normal gear terminology.

John S.

Spin Doctor
02-18-2005, 07:43 PM
John, think of a circular rack as a normal rack rotated around a centerline that is at a right angle to the teeth. The reason for using something like this is for full support in the bushings in the fixture and also making it easier to assemble. Another plus is one rack can operate several gears in the clamping system

torker
02-18-2005, 10:03 PM
<font face="Verdana, Arial" size="2">Originally posted by garyphansen:
I would not expect the slight helix to cause a problem. Gary P. Hansen</font>

Gary...If you where going to use this for something with very little pressure on it then it MAY work. I can tell you for a fact that it DOES matter though. I was told the same thing when I first started cutting gears for my threading dial. I cut the first one with straight teeth. It did work after a fashion. Just out of curiousity I maintained pressure on it with my hand. You could feel the gear trying to push away from the leadscrew. After a very short time you could see a definite "ugly" wear pattern. The teeth where only engaging about 1/3 as much as they should have. This is with a straight cut gear running on a 3.3 deg helix. There was VERY little contact area and the gear felt sticky as it rotated. This was with a 6061 alu gear. The next gear was a bronze gear mistakenly cut at 2.5 degrees(it was midnight...lol!). It did the same thing but not as bad. Not until I made the next one with the proper 3.3 degree helix did it work and engage smoothly. The wear pattern is much nicer also, except for the fact that there is still not much tooth contact with the straight sided gear running on a round leadscrew. I'm thinking in a perfect world you would also want an hourglass shaped gear to run on a round rack.
Russ

Spin Doctor
02-18-2005, 10:20 PM
idealy the gear running with the lead screw should be a worm gear as the lead screw is itself a worm

torker
02-18-2005, 10:25 PM
Spin...I guess that's what I meant http://bbs.homeshopmachinist.net//biggrin.gif LOL...snorted too many welding fumes today!

Thrud
02-20-2005, 03:10 PM
<font face="Verdana, Arial" size="2">Originally posted by John Stevenson:
Spin,
Surely a circular rack would be a gear ?
I have made many quadrant gears for rise and fall tables and these were just parts of gears and followed all normal gear terminology.

John S.</font>

A circular rack is called a "worm gear"

Norman Atkinson
02-20-2005, 05:07 PM
Or a Bicycle Chain?

Norman