Cutting parallel tooth gears

[JasonBModerator @jasonb]

When posting in the reply box there is an icon of a black camera along the top, click on that and it will bring up a window with a list of your albums on the left, click the required album, then a list of the photos comes up in the middle column, click the required photo and the image will come up on the right. If its the correct one click the OK button, if not select another photo until you get the right one.

 

J.

Edited By JasonB on 21/12/2013 20:08:09

[Geoff Lewis 1Participant @geofflewis1]

Continuing from where I left off last night after advice from a kind soul:

I decided the prudent thing to do after all the information was to try a couple of practice runs to get a feel for the operation. One of my better decisions. Not having had much experience of driving a dividing head I found the time well spent. Because I had to set the dividing head at an angle angle on the milling table right next to a wall visibility was not good and mistakes were easy to make so several blanks were used.

This first two examplesboth seemed a bit thin on the crest of the teeth but I don't know why. To make sure the centre height of the cutter was right I made a gauge to put under the cutter face after measuring the distance with a piece mounted in the chuck with slip gauges and feelers. I also made two others for use with the cutter offsets and used then to position the cutter height.

I must confess that I found first gashing the teeth at cente height and then two other positions bloody confusing with having to reset the gear position twice so I elected to use a slightly different procedure.

My first action was to offset the cutter downwards, lock the quill and do a shallow gash for the full number of teeth. This had two effects. Firstly it calmed my nerves and secondly it got me familiar with resetting the the dividing prongs. I also made sure that I turned the dividing head clockwise to rotate the gear anti clockwise.

After the first gash I went around again and cut to full depth. The results are shown below. Instead of winding the dividing head on a quarter of the indexing angle I wound it on a half of the index angle – 20 holes (anti clockwise on the handle = 20 holes clockwise on chuck) for the 22 tooth gear – raised the head twice the offset -0.112" using the DRO – and locked the quill. I then went around the second time winding the handfle clockwise this time so that the gear rotated anti clockwise. I don't know why but the result was much better.

I will follow this posting up later. The page is not responding to where I want to postthings.

[Sub MandrelParticipant @submandrel]

Hooray! Another convert to bevel gear cutting!

Neil

[Geoff Lewis 1Participant @geofflewis1]

Carrying on fromu before Christmas I can now put up a couple more pics of the two 24 tooth gears that came out much better. Only problem I had was that one was made from EN9 ? and the other from EN24 because of the duty it was to be subjected to. One cutter startedto go blunt and had to be changed to tackle the EN24 and I then found that it lost a few thou on the depth of cut which meant resetting. Apart from that hiccup they seem to run together with their 22 tooth partners ok but may just need som finaldressing with a file.

[Sub MandrelParticipant @submandrel]

I found that home made cutters struggle with the higher alloy steels like EN24T as well. There's a minimum speed you need to keep the cutter from stalling and that can be high enough to take the corners of the tool, and once they have gone you get rapid overheating and then more and more wear.

I imagine that multi-point cutters would be much better in such steels. Perhaps one day I will make a 'eureka'!

Neil

[Brian WoodParticipant @brianwood45127]

Hello Neil,

Eureka, that's a name to conjure with! I made one sized up a bit to cut standard dimension 20 DP gear cutters, but it was hard going on the pawls when it came to making cutter blanks in boron through hardening steel.

I had two hardened pawls fold up under the strain. It even struggled making an aluminiun alloy test cutter! Admittedly that was for other reasons than pawl failure, but I came to appreciate the design rerquirements for relieving lathes as a result.

In the end I attacked things in a different way altogether which was much more successful and capable of putting in the torque needed to cut the relief using button cutters. It was hand powered and still required enough effort to regularly bend the 5/16 inch diameter steel handle used to pull it over! I estimate some 30 foot pounds of torque was needed to cut that stuff.

When time permits I am thinking of writing up an article on the whole experience for MEW if you think that would be of interest, wearing your new hat of course.

Regards

Brian

[Anonymous]

CNC is the answer. Here's a cutter being machined in gauge plate, with proper relief, and intended for cutting splines:

I used an uncoated carbide 6mm ballnose cutter. Total machining time was a shade under 4 hours at 3000rpm and 150mm/min feed.

Regards,

Andrew

[Brian WoodParticipant @brianwood45127]

Hello Andrew,

I agree with you, a good rugged looking job and today's way to go IF you are suitably equipped.

There will be plenty like me without that sort of facility who might still find older methods more in their field of understanding.

Regards

Brian

[Geoff Lewis 1Participant @geofflewis1]

Many thanks to all who have replied to this thread and my queries about screws. I'll keep you posted as and when.

[Author]

Posts