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Pinion Milling Attachment MEW 164

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David Carne23/10/2010 21:04:49
11 forum posts
Has anyone experience of making this attachment?
I had extreme difficulty in trying to flatten the mild steel bed, so much so that I gave up.I tried the shaping machine, flycutting on the milling machine as the article suggested and bolted to the faceplate on the lathe.
I am now using ground gauge plate as is, hoping that it will be accurate enough.
Any helpful ideas would be welcome.
 
Regards
 
David 
 
John Olsen24/10/2010 00:53:31
1294 forum posts
108 photos
1 articles
What sort of problem did you experience? I can think of two sources of difficulty with machining something flat:
 
1/ There are locked in stresses in the material, so when you machine it it moves, sometimes taking a while to reach a stable state.
2/ It is not initially flat, so when you bolt it to a machine table you build in a bend, which means that your machined surface is not flat after you take it off the table.
 
 
The first one happens with cast iron and also with cold rolled steel, eg BMS. Aging is supposed to help with castings, but who has the time...also you should skim the surface off before leaving them to age. A bit of annealing is probably the best approach for either cast iron or BMS. You dont need to get it very hot, they used to suggest using the domestic open fire and leaving it in the ashes overnight to cool slowly.
 
The second one is especially a problem with castings, since they tend not to be very flat, and it is hard to machine them flat if your hold downs are warping it. If you can bolt the item down so that it is only sitting on three points, then skim one side, then you have a flat face to put against the table to do the other side. One problem here is that the holding down arrangements tend to get in the way of the machining.
 
Anyway, guge plate should normally be flat enough for most purposes.
 
regards
John

The Harper05/11/2010 01:26:08
18 forum posts
12 photos
Hi david
 
I am in the process of making mine now.
 
Rather than machine my base out of mild steel or cast iron, I used 8mm thick gauge plate. You can get this from many suppliers i.e J&L Industrial Supplies, for a reasonable price and it is already ground to a better tolerance than you are likely to machine at home. Plus, you will have quite a bit left over for other jobs.
 
I have also done away with the block/ key for locating in the tee slot, it is as easy to clock the side of the jig when clamping it to your machine bed. If you still want to use the locating block / key on the bottom of the jig may I suggest using two 3mm (1/8") dowels to fix the key in position. It may also pay you to dowel the two blocks as well, something like 5mm diametre diagonally opposed to the two tapped holes. this will make the jig much more rigid and accurate. When cutting pinnions or wheel teeth it is important that the job stays as rigid as possible allowing you to get the best finish possible, this will save a lot of hand finishing work later. Depending on how accurate you want to be, a couple of 2 or 3mm dowels on the index plate and support block could be useful. I am sorry if this seems over engineered, it is my Toolmaking training coming through!!
 
I hope this is of some help.
 
Regards
Paul

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