Reaming Blind Holes?

Gallery, Projects and General > How do I??

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Meldonmech:
Hi Pete,

When making your 1/4 inch dowels drill and tap the end M4 or equivalent, to provide for extraction. A small piece of tube, a large washer and an M4 socket head cap screw will easily remove the dowels when required.
I have recently fitted a screw cutting gearbox to my Raglan 5inch Lathe.

Good Luck David

DaveH:
Well I'm lost :Doh:
Parallel dowels are not supposed to come out - are they?
I thought the idea was for locating, looking at the drawing the two dowels stay in the base (part). The top part comes off with the two screws, the two dowels are a good fit in the top part but stay in the base part, which enables the top part be replaced accurately. Now if one is going to "knock" them out (the dowels) then what was the point of putting them in.

Or have I got this all confused :)
:beer:
DaveH

S. Heslop:
Would a D bit reamer work? As far as I know they arent usually tapered.

Meldonmech:
Hi Dave,
To remove the lead screw on a lathe it requires the lead screw support bracket to be removed by sliding it off to the right, which can only be removed by extracting both the screws and the dowels, as the lead screw has to slide through the apron there is not not enough room to remove the bracket with dowels attached to it. As you say this not the way dowels are normally used, but there are cases like this where it is necessary for dissembly, and maintenance.

Cheers David

Pete W.:
Hi there, all,

Thank you to everyone who has responded to my post. :clap: :clap: :clap:

There are a couple of points I'd better clarify:

First of all, this is a hand-tool job. There's no way I can get the lathe on its side up on the drilling machine table!!

Secondly, the gearbox fitting instructions imply that the dowel holes should be drilled blind, not right through. The idea that the dowels could be 'knocked out from behind' would require that the holes be drilled right through the front wall of the bed, across the central gulley and through the rear wall of the bed - I don't think Myford intended that.

I don't know if later ML7 & Super 7 production models left the factory with the lead-screw bracket dowelled. From the way the dowelling procedure is integrated into the gearbox fitting instructions, I'd guess this procedure wasn't done in production on most of the ML7/S7 population.

A member of my family who has a Super 7 with the dowels fitted complained to me that his come loose! :scratch: :scratch: :scratch:

The rationale for the dowelling mod is now probably lost in the mists of history. All I can conjecture is that lathes with gearboxes get more powered exercise to their lead-screws and this takes its toll on the security of the right-hand lead-screw bracket.

Regarding David's point, the gearbox fitting procedure requires that the lead-screw be shortened. In the case of the Super 7, the RH bracket is removed and the lead-screw withdrawn to the right. In the ML7 case, the RH bracket remains in-situ, the lead-screw retaining nut is removed and the lead-scre is withdrawn to the left.

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