Shank size and modifying for correct tool height for Myford S7
|Thomas Gude||14/07/2020 19:24:19|
|104 forum posts|
After years of head scratching and purchasing different sized parting and indexed cutting tools I have finally gotten to the bottom of why my tools sometime appear high as well as the contradiction between members' experience on whether a 10mm indexing tool can be used on a Myford S7.
Here is a photo of my tool holders:
The top 2 came with the lathe and I purchased the bottom three from Chronos in 2014. Visually the top ones have different knurling, different coloured cap head screws and the original's have a matt "blasted" finish. But crucially, the lower lip of the original holders is 0.2320" whereas it is 0.2665" for the new holders. This means that a 10mm indexing or parting tool will only fit in the top two holders! It is too high in the newer ones.
So, my question is - can I shave some material off the bottom of the newer holders? I am unsure what kind of steel they are or whether they are hardened. I do have a fly cutter set up on my S7 which I have used to good effect before.
In the interest of reference to anyone viewing this is the future, these ME threads may also be useful:
|David George 1||14/07/2020 19:33:03|
1264 forum posts
The ones I have are case hardened and when I bought some extra for my lathe they were slightly diferent and I found that I could mill them with a solid 10mm carbide end mill. If you go straight in under the hard skin it milled ok.
Edited By David George 1 on 14/07/2020 19:35:09
|Peter Spink||14/07/2020 20:01:56|
93 forum posts
Another thread here "LINK"
I had a similar problem so machined 0.050" from the top of the topslide - problem solved!
|Clive Foster||14/07/2020 20:47:07|
|2254 forum posts|
The bottom of the holder is "in the wind" anyway and does nothing so exact size and shape matters little so long as you have clearance and the bottom lip not unduly weakened.
If the material is machine unfriendly, or needs a heftier machine than what is available, I'd have no compunction about hitting it with a flap disk in a hand held angle grinder to rush the bulk of the material off then finishing up in the linisher so the final surface looks true. My linisher is a Morrisflex vertical type so setting some stops on the table and clamping a bar in the tool post would let me get very close to true and parallel.
If you do go the flap disk in an angle grinder way blueing up the four edges and scribing a line will give you a good guide for getting it close with the angle grinder.
One other issue to be aware of when mixing'n matching Dickson type toolholders is the thickness of the bottom collar on the height adjusting device. There is some variation, much more so with hobby market suppliers than professional. If they are too thick they won't fit properly in the snail shaped slot in the locking device and the holder will be canted over rather than properly locked vertically to the post. Which is very unsatisfactory. Frequently you see bent height setting studs on holders abused in this manner. Well worth checking if you haven't already done so.
|Thomas Gude||15/07/2020 09:29:38|
|104 forum posts|
[quote]Posted by Peter Spink on 14/07/2020 20:01:56:
I had a similar problem so machined 0.050" from the top of the topslide - problem solved![/quote]
Unfortunately I don't have a mill, so that would be tricky. Also, to me something feels slightly off about modifying a 65 year old machine,
Thanks Clive. If anything I think the collars are slightly under thickness, but well worth knowing, cheers.
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