NMTB 50 taper with 5/8 11 drawbar and boring head question

marka12161 · Mar 15, 2019

When i bought the Kempsmith #1G universal mill, i bought up a bunch of tooling as well. In the mix were a couple of boring heads both of which have what appears to be nmtb 50 tapers but with 5/8 11 threads for the drawbar. All my other nmtb 50 taper tooling has 1" 11 threads. What's up with that?

Also,
The large boring head looks to be large for my machine (3HP motor). Am i overthinking this?

Limy Sami · Mar 15, 2019

A bit

in your shoes I'd knock up a drawbar to fit the tooling (allthread will do) and not worry about the size of the head V machine HP , boring head work is not normally high HP hogging.

Blazemaster · Mar 15, 2019

if the machine is a 50 taper it can hold some pretty large tooling. I just bought a huge boring head at an auction, 15" diameter that mounts directly to a 50 taper spindle. It must weigh 150lbs. I have also seen some pretty large face mills on a 50 taper sized machine.

Paolo_MD · Mar 16, 2019

Although much less popular, I believe that 5/8-11 is one of the two standard threads for NMTB holders. I have a couple with that thread as well.

Paolo

johnoder · Mar 16, 2019

A reason tens of thousands of draw bars had both threads on the business end - and plenty of thread length other end

marka12161 · Mar 16, 2019

Thanks guys. The body of the boring head is about 6" dia so maybe not so big in the grand scheme of things after all. Thank you for tolerating the newbie.

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NMTB 50 taper with 5/8 11 drawbar and boring head question

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