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Denis Foster 18" Straight Edge / Prism

nygavin

Plastic
Joined
Jan 25, 2017
Hi,
I just wanted to give a post and a big thumbs up for Denis. I recently received mine and couldn't be more pleased with the job he did on both the casting and the machining. I honestly thought he was just going to remove the dross so I wouldn't have such a mess. Instead he really took the time and made it absolutely ready to scrape in. Less than 2 thou flat and nicely relieved where the bevel meets the top. I also requested he drill and tap the holes for the precision vial since he has the tooling for that. Well packed too:)

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CountryBoy19

Stainless
Joined
Aug 14, 2012
Location
Bedford, IN
I must've missed that neat little prism when he developed it... and I can't find a sale thread for it. What's he charging for them (not-machined)?
 

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
I must've missed that neat little prism when he developed it... and I can't find a sale thread for it. What's he charging for them (not-machined)?

He sells them unmachined for 190 dollars plus shipping. :) I have not been advertising them as I have been working hard to meet demand for them. I have limited time available for production.

Denis
 

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
BTW, Shipping about $20 in the US as one of the design parameters of the SE was that it fit in a Large USPS Flat Rate Box.\

The second and third pictures show the device I drew up and made to allow drilling and tapping the mounting holes located under the overhanging upper surface of the prism/straight edge/level/parallel. The device attaches to the quill and of my mill and the spindle drives the drill and tap.

Denis
 

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dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
A couple more pics of the sidearm drilling device.
 

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TGTool

Titanium
Joined
Sep 22, 2006
Location
Stillwater, Oklahoma
Since we can assume that almost all participants are machinists or engineers I expect they're also cheering for technical solutions like Denis has worked out just as I've been. The part of me that gives a big sigh about the tool or fixture I have to make, to make the tool to do the job in the first place would consider a real non-technical short cut. Machine the recess as shown, machine a small bed plate with tapped holes and seat it with epoxy. (Hope my flame suit still fits)
 

CBlair

Diamond
Joined
Sep 23, 2002
Location
Lawrenceville GA USA
Since we can assume that almost all participants are machinists or engineers I expect they're also cheering for technical solutions like Denis has worked out just as I've been. The part of me that gives a big sigh about the tool or fixture I have to make, to make the tool to do the job in the first place would consider a real non-technical short cut. Machine the recess as shown, machine a small bed plate with tapped holes and seat it with epoxy. (Hope my flame suit still fits)

I was thinking kind of the same thing. Charles
 

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
Since we can assume that almost all participants are machinists or engineers I expect they're also cheering for technical solutions like Denis has worked out just as I've been. The part of me that gives a big sigh about the tool or fixture I have to make, to make the tool to do the job in the first place would consider a real non-technical short cut. Machine the recess as shown, machine a small bed plate with tapped holes and seat it with epoxy. (Hope my flame suit still fits)

Certainly, no flame suit needed as far as I am concerned. I must have considered 5 or 6 possible solutions to the mounting problem. They included a mounting plate, drilling and tapping through from the bottom surface of the prism, drilling from the top and or bottom and inserting threaded studs with cast iron plugs in the surface holes, or using simple JB Weld to close the hole the surface of the drilled and tapped hole, etc. But for one reason or another I discarded them as less desirable while recognizing them as all far less technically difficult than the route I chose. One significant problem with the glued in subplate is that the customer may want to additionally stress relieve the casting even though I stress relieved prior to machining and held it in the sand for initial cooling. In that case I would not have been able to hand them a truly ready-to-use casting had the plate been intended to be attached with epoxy. Then there is the less defensible prejudice I have against gluing in a plate---I had this awful vision of the plate coming loose (yes, unlikely) with it and a shattered 100 dollar precision vial on the floor. And finally, (could this have been the "real" reason;)) I wanted to make up the rig as it was uncharted territory and was a challenge.


Nevertheless, a user might very well opt to make their own plate and glue it in. They should also realize there is very little headroom for such a plate. I think it could work though.

The drill rig is nice, but I wanna see the itty bitty little tap wrench ;-)

Lucky7

Attached are pics of the housing, drill bit, tap, pulley, and drive belt

I was thinking kind of the same thing. Charles
 

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TGTool

Titanium
Joined
Sep 22, 2006
Location
Stillwater, Oklahoma
Denis,

I certainly wouldn't quarrel with your choice of process. Goodness knows I've done any number of things, sometimes the hard way, just to see if that worked or for the experience. In fact, I would postulate that there's something built in to this segment of the population that needs frequent challenge, hates boredom, has an insatiable curiosity or whatever. Otherwise lots of the toolmakers I've known would have gone into production work of one sort or another. It's exhibited in the range of features of the pieces that toolmakers make for themselves. Variations on angle plates, V-blocks, setup aids etc. Everyone knows the basic functions and features but every guy (generically speaking, no offense to women in industry) puts his own stamp on it with size, steps, hole patterns, special features or even just paint.

A long way to say that what you've done is absolutely understandable and falls into a long history of unique craftsmanship and ingenuity.

Some months back I was at a committee meeting for an organization\ work with and the few of us were hosted at someone's house. Going in the side door, there were two shelves of toolmakers' odds and ends. I stopped a bit to look at different pieces, many with a variety of initials stamped in and was just enthralled. I tried to drag a couple others over just to see the story told by the pieces. You knew what machines a guy had available, something of what he was thinking and needing and more. I couldn't get anyone else pried away so there were those shelves talking to passersby and hardly anyone was listening.
 

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
One additional bit of clarification on the method I used to drive the tap. I previously quickly summarized the operation of the device saying that the spindle powered both the tap and drill. That is indeed true for the drill. But powering that little tap with the spindle and at the same time not snapping it off would be a dicey proposition. So, the drive axle and pulley that mount in a 1/4' collet has a 2" knurled knob that I hand drove the tap with. That allowed very good feel for when the tap was reaching bottom and was quite easy to do with finger power alone. Here is an attached photo of the drive knob/axle resting on a portion of the device's "blueprint.":D

Thanks to all the kind folks who made positive comments (like TGTool, for instance)

Denis
 

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kiloseven

Plastic
Joined
Nov 27, 2018
Hi,
I just wanted to give a post and a big thumbs up for Denis. I recently received mine and couldn't be more pleased with the job he did on both the casting and the machining. I honestly thought he was just going to remove the dross so I wouldn't have such a mess. Instead he really took the time and made it absolutely ready to scrape in. Less than 2 thou flat and nicely relieved where the bevel meets the top. I also requested he drill and tap the holes for the precision vial since he has the tooling for that. Well packed too:)

View attachment 252805View attachment 252806View attachment 252807View attachment 252808
 

kiloseven

Plastic
Joined
Nov 27, 2018
Ditto , The straight edges are very well done. I have a starred vial to mount. and it's really flat. Thank for a great tool
 

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
I have had people ask, from time to time, if the 18 and 26 inch prisms can be machined to 55 degrees though they are cast as 45's. The answer is yes, they have plenty of meat to allow this. I had a recent request from a member here to machine one as close to 55 as was practical. I was able to get it within 0.1 degree of 55 without too much fiddling. Most of the time I just try to get somewhere near 45 (+/- a half degree or so.)

I thought I would post pictures of the results.
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The holes in the ends are placed for fixturing as they allow me to hold the prism for milling without inducing flexion. Straight edges are checked for flatness after milling and this one actually hinges at about 1/4 on each end (they don't always) and you can feel it suck slightly as it is lifted away from the surface plate. They are properly thermally stress relieved by me prior to machining. I have never had the first milled face "move" due to machining the second face---in other words I don't have to make a repeat cut on the first face after milling the second to maintain flatness of the faces.

I appreciate the all the support from members here over the years.

I am currently working on an improved workholding system that will streamline milling. I'll post more about that later.

Denis
 

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