Here is a list of all the postings Steve Crow has made in our forums. Click on a thread name to jump to the thread.
|Thread: New member from Bath|
I am a very happy Sherline user. The system is so versatile. For about £2,500 you can get a lathe and mill with a huge amount of accessories including a CNC rotary table like Clickspring uses for indexing.
I've just got the horizontal conversion kit for the mill. This enables you to turn the milling column 90 degrees in 3 different positions. This should give the potential to make wheels of much bigger sizes than anything a Cowells is capable of.
Everything I have got from Sherline has been well designed, well made and well finished. The documentation is superb as well.
Also, the service from Kevin of Millhill supplies (the UK importer) has been excellent. I have no connection with any of these, just a satisfied customer.
|Thread: Cutting small gears.|
That's nice! Does the dial work an eccentric cam for adjustment?
Would love to see plans for this.
I know, look at this beautiful tiny thing. Just don't look at the price.
And this would fit my Sherline milling machine and triple its value!
I can feel a project coming on....
Edited By Steve Crow on 01/05/2020 17:29:03
That is interesting, There is quite a wide variety of small size solid carbide end mills available, although a bit more expensive.
How many flutes would you recommend for HSS? It looks like 3 in the photo. And cutting speeds? Doesn't carbide like a high speed. But with HSS?
Any hints or tips welcome.
I used quite a simple drawing program, not CAD, and drew them exactly as I would have on paper using ruler, compass and protractor etc.
Hi Martin, yes, i took that into consideration but in most cases metric was close enough.
The exception is the 10-11 tooth. The alternative for this is 4.8mm so I can get use 3/32 for Mod 0.5 and 1/16 for Mod 0.33.
Also, I already have a good number of endmills in smaller metric sizes.
The trouble with milling single point cutters is you need the right size end mill for the correct radius on the tool.
The button diameters in Ivan Law's tables are all integers or halves for Mod 1 but are not all easily divisible for smaller mods.
I decided to draw up alternative dimensions for each tooth count. Using the alternatives, I can now cut Mods 0.25, 0.33 and 0.5 all using easily available end mill sizes.
This is what I came up with.
Can anyone see any flaws with this plan? Has anyone milled small single point gear cutters before? Any comments or question welcomed.
|Thread: Telescopic bore gauges.|
I only needed the 2 smallest sizes so I got a couple of Mitutyo rather than a set.
Lovely and smooth with loads of "feel", so much better than a no-name brand I have. Consistent readings too.
Using a micrometer stand makes all the difference as well (unless you've got 3 arms).
|Thread: Cutting small gears.|
I'm reposting the image as it was hard to see.
I want to cut gears in Mod 0.25 or 0.333.
As I need to keep the tooth count low I want to use 30 degree PA.
Originally I was going to use the "hob forming" method. I posted about it a few weeks ago and a few of you responded having used it successfully. Others were dubious.
I've done some drawing to find out what tooth profiles I'd get with a single pass and 2 passes with the work rotated 1/2 a tooth and the cutter moved by 1/2 a pitch. I then compared it to a tooth generated using Ivan Law's info. Here are the results.....
As you can see, the single pass will only work with extra depthing and it's got a crude profile. A second pass improve things a lot but still looks tight. I'm sure a couple more passes would help a lot but the accuracy of the tool movement would have to be very good.
For my application the distance between centres is fixed so I'm going to have a go at making single point cutters milled from carbon steel using Ivan Law's button dimensions. It seems to be a popular method for making horological cutter in the USA.
|Thread: Proxxon mill|
Here are some Proxxon BFW40E details.
|Thread: Gear Cutting - Pressure angle.|
Thank you Andrew that makes sense
So is the 30 degree rack profile in the drawing correct? I realise that I can fettle the dedendum ratio.
I've been looking at 30 degree pa gears.
Here is a drawing of a rack form and hob to cut it. I've followed the usual formula for the 20 degree rack but it just doesn't look right at 30. Not much in the way of crest and the root is almost non existent.
Is there a reduction in addendum and dedendum for increased pa?
I've trawled through all the excellent links you have recommended but I can't find anything. Maybe it is buried amongst some of the impenetrable (for me) maths.
|Thread: Gear forming hob|
Thank you all for you replies and information. Just a couple of points.
I understand that this is not the ideal method for gear cutting but it's my only chance of making the gears I require. With mod 0.20 or 0.25 a single point cutter of any description is going to be tricky to make to an accuracy to improve on the hob forming method.
Also, the "relief" on the drawings aren't the finished profile, just a guide for milling. I intended to go past the centre for rake and get the files out for relief.
I have a CNC dividing head so I have given thought to going round more than once and adjusting tool height but with teeth this small accuracy would be paramount. I have got a DTI mounted to Z axis so I might get away with it.
I've made the blanks and rough grooved them with a threading insert. I just need to finish the grooves with my home made 40 degree insert.
Hi Dave, what a fantastic thread. I've not taken it all in yet but there is some great stuff on there.
I intend to make a number of small gear forming hobs as described on the Helicron site and discussed here before.
I milled an insert type 40 degree cutting tool from GFS, hardened, tempered and sharpened it with a crocker jig and an arkansas stone. I can't see any tip radius under 12x magnification.
I realise that it won't stay like that for long but I will only need the sharpness for indexing for depth of cut once on the first hob. After that it is indexed for subsequent hobs.
To prolong tool life further, I intend to rough out the grooves as much as possilble using a 0.1 mm radius tip threading insert I have.
I want try to do three hobs, starting with the smallest mod where things are more critical.
I've attached some drawings. Please have a look at the relief forms and let me know if you think that they will work.
I look forward to any comments.
|Thread: E clip tool|
Cheers Ian, with a forum name like that I know where to go to for info!
I'm not sure I want to try to mill a dovetail that size. Did you make them as small as this?
I need to retain a compression spring on a 1.2mm shaft using a small e-clip.
And boy, are they small.
I need my finest point watchmakers tweezers to handle them. They are 2mm od, 0.2mm thick and fit a 0.8mm dia groove. Despite their size, they need a fair bit of pressure to engage.
I made a tool to both depress the spring and fit the clip. It was milled from 3mm silver steel, hardened, tempered and polished. Works a treat.
The photos are self explanatory.
Now I need to make a tool for removing them without the "ping"!
|Thread: Small skeletonised drill Press|
Here is one similar to Nicholas's first pictures - Link.
Words fail me.
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