Need a little help figuring something out. Just got a HF round post mill. It can use R8 collets, and has a MT3 taper in its spindle and it came with a few R8 collets. My lathe has a MT5 opening on the chuck side of the spindle and I have no collets for that. Is there an adapter and/or what is it called that would allow me to use the R8 collets on the lathe. OR, should I go in an other direction and find a different type of collet for the mill. The idea is to use 1 type of collet if at all possible for both machines.
Thanks
#1 Your appraisal is confusing. This "interchange" is unlikely,
It can use R8 collets, and has a MT3 taper in its spindle, and impractical for mill and lathe.
Coupled with responses identifying vast physical difference of R8 vs MT, another issue is daylight; available space from spindle to work-piece. MT uses lots in accomplishing tool changes, not to mention extending the quill to access drift slot. Few if any round column mills will reattain identical previous relationship with table X & Y after raising and lowering the head; same basic issue as round drill presses. The detriments are same if drawbar MT's were a goal, along with loosing tool diameter capacity.
Far as R8 for lathe use, the complications are similar but reversed and loosing capacity of stock [material] size and length.
So, my conclusion is yes; but time-consuming, limits machine capability, and highly impractical on different levels. Strategically thinking, it has some logic; tactically, little or no advantage.
That still doesn't involve considerations making concentric, ground holders of heat-treatable material, and in "one each" size for 2 or more machines.
Despite all that, a few guys
have made lathe QC
toolholder blocks in R8; again they are blind collets [no thru hole, need drawbar], making justification questionable.
The attraction is low cost; R8's are probably lowest of all similarly sized holders. Smaller stock, no through hole, shallow precision diameter, just 3 cuts and a keyway, ID threads simple to tap, and short angle.
If for some reason compelled to make collets, do something like ER's or DA's. They are double cut [from each end] offering more size range per unit by compressing. Single cut only hold correctly on ONE diameter, anything else is pinched; concentricity down the drain.