Tom Fitzpatrick
Active Member
Looking to purchase a quick change tool post for my 12" Craftsman lathe. Should I go piston type or wedge type? Shars has both in AxA and BxA sizes.
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Quick change tool post.
- Thread starter Tom Fitzpatrick
- Start date
Dabbler
ersatz engineer
If you have a choice, and the price difference is acceptable, then choose wedge - however - if the wedge type isn't made very accurately, it will be worse than a piston type, which is easier to make....
Why? the wedge is a sliding gibb, and the wedge and the root have to be ground to a very high degree of parallelism to properly lock the dovetail. I have a piston AXA on my 12X37, I have a BXA piston type on my 14X40, and I have a real Aloris BXA wedge type on my 15X60.
As far a repeatability, the little AXA has a slight edge over the Aloris wedge. But that's a nitpick. they all locate within .001 in x,y, and z.
On hobby-machinist.com, we have seen some examples where the wedge wasn't well made, and it led to rocking of the tool holder. I think Shars stuff is generally better quality, hence the above recommendation.
-- If the wedge type is well made, it has more rigid holding power over the piston type, which is why it is generally preferred.
Why? the wedge is a sliding gibb, and the wedge and the root have to be ground to a very high degree of parallelism to properly lock the dovetail. I have a piston AXA on my 12X37, I have a BXA piston type on my 14X40, and I have a real Aloris BXA wedge type on my 15X60.
As far a repeatability, the little AXA has a slight edge over the Aloris wedge. But that's a nitpick. they all locate within .001 in x,y, and z.
On hobby-machinist.com, we have seen some examples where the wedge wasn't well made, and it led to rocking of the tool holder. I think Shars stuff is generally better quality, hence the above recommendation.
-- If the wedge type is well made, it has more rigid holding power over the piston type, which is why it is generally preferred.
Tom Fitzpatrick
Active Member
Thank you for this information.
