Con Rod - Taper Turning

Hello,

I hope I've posted this question in the right place.

I'm fairly new to the hobby of Model Engineering and am looking for help to order to turn a taper on a con rod. I've never turned any kind of taper before. The con rod is just over 6" in length. The centre should be 5/16" and each end should be1/4". I have absolutely no idea how to go about turning this. Can anyone help? I have a Myford Super 7 lathe.

Regards

Tom

Tom,

[Assuming that you don't have the 'taper turning attachment'] ... You will need to turn between centres, with the tailstock offset. ... See this very helpful page.

I suppose you could do it in two or three bites using the topslide ... but I wouldn't recommend it.

MichaelG.

I asked a similar question a while back, see here.

http://www.model-engineer.co.uk/forums/postings.asp?th=75818

Phil

With a long thin rod like that you should get away with making it overlength, holding it in the 3-jaw and setting the tailstock towards you by 1/32".

The flex in the rod will cope easily with this offest, but you may find that you get a slightly curved taper - it may not be noticeable.

Neil

Michael,

I do not have a taper turning attachment. Can you recommend one which I can use on a Myford Super 7 lathe/

Tom

For a fish bellied rod like that the two tapered ends will only be 2" long, I would just set the topslide at a slight angle. Basically diveid ethe length into three, leave the middle at 5/16 and taper the two ends from 5/16 down to 1/4" and then blend the transition with a file.

All these were done that way.

Take a look at the first few photos in this album of mine, to see the principal

Better still part way down this page is the post I used the images for with an explanation

J

PS don't try Neils suggestion as that won't work for the tapers you require the tailstock woul need to be set over atleast 3/32" not 1/32"

Edited By JasonB on 09/08/2015 16:07:54

I agree with jason b use the top slide set over to the required angle, I do own a taper turning attachment for the super 7,bought at a reasonable price at an autojumble,have only used it three times in twenty years to produce tapered BSP bronze plugs for customers full size TE. I did make a full size Crossley oil engine con rod from solid steel billet (170 lbs) and had to turn between centres with the tailstock set over,works ok. When skimming up stationary engine con rods to remove rust pits I prefer to use the top slide set over and do it in 4 o r5 bites,just have to be careful blending in the cuts.

Neil';s calculation was correct - he just didn't spot it was 1/4" at BOTH ends

Neil

.

Tom,

You really don't need one, unless you plan to do a lot of tapers. [I only mentioned it to avoid my embarrassment if you happened to have one tucked away under the bench] ... The dedicated Myford one would be the obvious choice, but I believe they are usually rather pricey.

I see that others have responded, variously, to your original question. AND most importantly, I see that [like Neil] I missed the fact that the rod is to be fish-bellied. .... obviously that makes using the top-slide feasible; although personally I would still prefer to work between centres.

MichaelG.

Michael, no reason not to work between ctrs and use the topslide.

.

Jason,

Perhaps I expressed it badly, but, that was exactly my point.

... it was Neil's suggestion [... you should get away with making it overlength, holding it in the 3-jaw and setting the tailstock towards you ...] that I was reacting to.

MichaelG.

Edited By Michael Gilligan on 09/08/2015 20:51:33

You may find, Tom, my method for producing a barrel shaped con rod worth viewing, here It requires more calculation, but less finishing, to arrive at a true barrel shape.

Harold

Gentlemen,

A very big thank you for your time and thoughts which will keep me occupied for some time to come. Very interesting...!!

Neil, I'm not particularly acquaint the with the running of this type of webpage. Have I posted my initial question in the correct place?

Tom