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MEW 156 tangential toolholder angles

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Model Mechanics Complete Issues for Download Parts 5 - 10

Model Mechanics Complete Issues for Download Parts 5 - 10

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Goran Hosinsky01/05/2011 13:57:18
41 forum posts
My first use of the tangential too lholder from MEW 156 gave me a better surface on F114 steel than I have been able to achieve until now. Has anybody experimented with other grind angles than 30 degrees for even better surface - and for other materials? If my geometry is correct the tool as designed has 10 degrees side rake and back rake, front and side relief is12 degrees.

Goran
Canary Islands
chris stephens01/05/2011 17:42:24
1049 forum posts
1 photos
Hi Goran,
I have not really tried different grind angles, but I know MGJ likes to have less top rake for Brass. What I have played with is different radii on the "business" corner, analogous to the tip radius on a TC insert. I grind both ends of the HSS and have slightly more radius on one end than the other but I have not, in truth, found the difference noticeable.
 
One tip for a possibly even better finish is to have the tool marginally above centre height for the forward cut, and then slowly traverse the tool to the right, on the final finishing pass, whilst keeping the cut on. This gives a very fine shearing cut which can improve the appearance of the finish. This trick might only work if you sharpen your tooling with a jig with the "V" in the top, it might not work if you use the Oz type one. It is all to do with which way the striations, left by your grinding wheel, are running.
 
I would heartily recommend the Eccentric style jig for sharpening a thread cutting tool, as it produces a very clean cutting tool. There are plans on the Net for such a jig, if you should wish to make your own.
There is though a slight awkwardness using the standard tool holder, for threading, when working near to the chuck. There is, luckily, an alternative style tool holder to overcome this problem. I will have to dig out the camera and take piccies if there is enough interest.
chriStephens
 
 
 

Ian Welford04/05/2011 20:38:15
300 forum posts
Hi Chris
 
please dig out the camera for the alternate style. Been thinking about making one for a while as I know you and MJG rave about them.
 
Trying currently to decide whether to part with a mk1 clarkson or a boxford T&C grinder as not enough room to use both! Life's full of hard decisions!
 
Are you doing Harrogate this year?
 
Ian
Goran Hosinsky04/05/2011 21:06:03
41 forum posts
Please take those pics - and perhaps a link to the drawings?
Goran
mgj04/05/2011 21:44:40
1017 forum posts
14 photos
All I do is round the nose of the cutting edge - get a demon finish. I only just break the corner with an oil stone.
 
There isn't any magic to the angles - it cuts no better than any other well ground high rake angle tool. (hence the bit about brass and bronze which I often cut with negative rake) The magic is in the ease with which it can be sharpened with minimal kit, and how quickly that can be done, and how economical a sharpening is of good HSS (a very rare and horrendously expensive commodity these days. Not the garbage that comes from the East BTW)
 
If you use the Chris type of holder, then it is set to cut to centre, with the shank of the holder at 90deg to the bed. That I like, becuse one does not have to change the set of the toolpost for the next tool - handy when the next tool is to be a parting tool and the toolpost has heen set truly square.
 
You can perform the same trick with an Oz type holder - which normally requires the toolpost to be offset. You grind 13 deg off the front face (.5 deg clearance), and then you can set the toolpost square. The limitation is the diameter you can face. The Chris desaign is better and more convenient. However I have 2 lathes with different toolposts and different centre heights, and but one CS design tool.

Edited By mgj on 04/05/2011 21:45:10

Edited By mgj on 04/05/2011 21:46:28

chris stephens05/05/2011 00:07:57
1049 forum posts
1 photos
Hi Guys,
I will try to take some photos tomorrow of both the screw cutter and the normal, but have not got any drawings, except in what passes for my brain.
As for MGJ, you will soon be able to junk that crappy old holder I made for you. I have finally finished a batch of the decent design. Had I been able to get to S.M. on Sunday you would have had it by now.
I don't think I can lay claim to the design of the one you already have, it is just an adaptation of another style. The new one may look like the OZ one but I think is more cleverly designed as it is all one piece.
 
The other day I ordered some 10%Cobalt HSS from J&L labelled "Intestate", silly me I thought I was buying "Intestate" the company that proudly claims American made. Yup, you guessed it made in China. Still it seems to hold an edge.
ChriStephens
chris stephens06/05/2011 12:02:23
1049 forum posts
1 photos
 
Hi Guys,
At last I have loaded some pictures of my holders. There are other views in my album. You will, I hope, forgive the photo quality and the machining detritus in some shots.
As I have said in one of the descriptions I have not improved on the prototype threading one, as recent developments (by a former ME forum member (Bogs), John Stevenson and a Mr. Cox) have rendered a static holder well and truly redundant.
chriStephens
 
Thor 🇳🇴06/05/2011 17:28:40
avatar
1766 forum posts
46 photos
Hi Chris,
thanks for posting pictures of your holders. Nice work, I must try and make somethinng similar.
 
Thor
chris stephens09/05/2011 22:39:07
1049 forum posts
1 photos
Hi Thor,
Why thank you kind Sir. Give it a go you wont regret it. I would not recommend you try to make the one in the photo, there are much easier ways of achieving the same style tool.
 
Hi MGJ,
If the GPO are up to the mark, you should get your new holder in the post tomorrow. I fitted the chinese HSS 10% cobalt, see what you think. Just for fun i ground the two ends on different jigs, one end in a Vee block and the other in the Oz style. I would value your opinion of the relative sharpness of the two grinds.
chriStephens
Goran Hosinsky10/05/2011 10:45:42
41 forum posts
Kind Sir, could you please explain how the Oz style is.
Goran
John Coates10/05/2011 12:18:31
avatar
558 forum posts
28 photos
Must admit I am giving one of these tool holders serious consideration as CT inserts are on the shopping list again for Harrogate. Instead I think I shall buy some steel to make the holder and some square tooling steel and have a go at making one.
 
So well done for this timely post and excellent reference material chaps !
 
John
chris stephens10/05/2011 14:50:06
1049 forum posts
1 photos
Hi Goran
If you look at the picture above you will see at the bottom the two types of sharpening jig. The one on the left is a simple Vee which is cut at 30 degrees to the horizontal. The one on the right is the Eccentric (OZ) style that employs a compound angled ,rebate to hold the HSS bit.
Of the two I prefer the simple one as I find it slightly better if you want a fine shearing cut, in the reverse direction, as well as the normal forward direction. The other one is fine for a normal forward cut, but perhaps you loose out on one of the other benefits of a tangential tool. I am waiting to hear what MGJ thinks of the two grinds.
chriStephens
mgj10/05/2011 14:53:39
1017 forum posts
14 photos
Chris- thankyou very much. All arrived. That new one is a marvel, and beautifully made too.
 
Its actually very superior to the Oz one, because the head angle is such that one can face without altering and offsetting the toolpost.
 
I set my QC toolpost up with a setsquare, so I can face, or part off deeply with a single plunge all at the same setting - I don't have to prat about restting parting tools square every time I want to chop a bit off a bar. Also I can have repeatable offsets for the DRO>
 
That is a very very good design indeed. most grateful - I'll report back about the cutting (after I have tied up a rose stem!)
 
Very kind of you and greatly appreciated M>
John Coates10/05/2011 22:24:12
avatar
558 forum posts
28 photos
Chris
 
How did you make the square hole for the tool bit? Is it a round hole filed out?
 
Have looked at it several times and admire the clean lines over the MEW 156 version. Any drawings perchance to enable reproduction?
 
John
chris stephens10/05/2011 23:41:37
1049 forum posts
1 photos
Hi John,
I could say I bought a 1/4" broach to make the hole but that would be lying, although from the picture you could have believed it. It most certainly is not a filed out round hole , I hate accurate filing as I am no good at it.
People who know my work will know how I made it, and those who went to Ally-Pally a few years ago and paid attention to the SMEE stand will also know. As a bit of a tease, I will PM you with the answer, but not say here. For the rest of you chaps, it is not difficult to work out, there is no great secret involved, but when well executed it will fool anyone.
 
As for drawings, there are none at present, I made it up as I went along knowing what i wanted to end up with. The angles are similar to the simple MEW model ie forwards 12 degrees and side lean also 12., everything else is cut away to suit the lathe. If I make another batch I will take photos and possibly write it up, but as DC1 has already printed one article there is not much point in offering it to him, is there. I do think it a superior model to the published one, but it does not do any better a job, and it is harder to make. Looks good though.
christephens
 
Goran Hosinsky11/05/2011 10:48:03
41 forum posts
Chris-
For us non UK persons who do not even know what or where Ally-Pally is it would be useful if you could post the method
Goran
Canary Islands
chris stephens11/05/2011 15:55:26
1049 forum posts
1 photos
Hi Goran,
Ally-Pally is the nick-name for Alexandra Palace, the home of the London Model Engineering Exhibition which is held every January.
I will try to remember to take some pictures of the demonstration display and post them for you to peruse. The method is ludicrously simple and can be almost invisible when done right. So stand by for a "Doh" moment.
chriStephens
John C11/05/2011 18:13:16
273 forum posts
95 photos
Chris,
Any chance of a re-demo' at Harrogate on Sat?
John
chris stephens11/05/2011 20:28:06
1049 forum posts
1 photos
Sorry John, not a snowballs. I could put it on the SMEE table at Guildford or if you can wait Sandown, if you are thinking of going to either. Harrogate is on my to get to list but not this time around. What part of the country are you in?
chriStephens
John C11/05/2011 22:10:55
273 forum posts
95 photos
Hi Chris,
 
Deepest darkest North Yorkshire so the Southern events are a bit far away for me.
John
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