Building Harold Hall's Simple Grinding Rest

[stioc]

Great write-up and photos.
I am "Watching".

Thanks for sharing this!
-brino

So that's how you do it.
Well done! Great thread and well documented.

Thanks for following along! I hope it's helpful to anyone else considering building one because I certainly had a lot of figuring out to do on how to approach the whole metric vs. imperial deal while still following along the drawings. Also Mr. Hall (who btw is 86 yo now as of 2019!) doesn't do much hand holding in his style of writing. He does provide a few helpful tips on the tricky bits but that's about it- I must admit though that it actually makes the project more fun and rewarding!

Just a note... you don't need a dovetail cutter, as you listed in your shopping list post, to cut the pieces that make up the dovetail (if you follow Harold's drawings anyways). Just tilt the pieces at the correct angle and use an end mill or whatever.

But, you can use a dovetail cutter if you so choose, but I'd save the cutter for when you want to make Harold's advanced grinding rest.

Ted

Funny you mention that because guess what I was just working on? Making sure my math/plans line up. Certainly not necessary but I'm nowhere near my shop and had some time during lunch - gotta make progress even if it's virtually lol

You're absolutely right about the dovetail cutter though. I just thought it would make things easier and I only need a hint of an excuse to buy more tooling!

 

[stioc]

Day 4:

So now that the base is built. I can get into the fun part of this project i.e. the dovetail slide that moves the table in and out like the crossfeed of the compound. I started modeling the dovetail slide to make sure my dimensions in imperial are in check (they're not critical as long as the angle is exactly the same for both the inner and outer dovetails. This is where the dovetail cutter is so much easier and accurate.

However, before cutting the dovetails I decided to drill and tape all the holes in the dovetail parts first. This is where doing a little bit of calculation up front helped me out and I simply issued a few CNC G90 G0 x/y commands to drill all the holes in the exact same locations with the help of a work stop. Also glad I did the layout work because twice I issued the G90 commands and noticed the location was off compared to the layout because I messed up my calculations.

While waiting for the spiral flute YG1 tap I've been using the 1/4-20 tap (with much trepidation) from my cheap Harbor Freight set I've had for 5 yrs - I think I paid $40 for it and have used it many times but mostly in aluminum. It's worked fine so far even in this 1018 steel.

After all the drilling and tapping I located one of the parts on the vise to cut the dovetail. Mounted up the dovetail and realized I couldn't line it up right. I know I ordered a 3/4"x3/8" from All Industrial. Checked the stamping on the dovetail shank, it said 3/4 x 3/8 x 5/16 -ugh! the height is 5/16 not 3/8. I wasn't happy. I think @Technical Ted Ted jinxed me - I kid I kid LOL. This means doing it the manual way, which requires more setup time and more chance of error from not having repeatability. So my option was to order another dovetail and wait 2 days or forge ahead.
To be continued...

 

[stioc]

Day 5

Well patience is not my strong suit so onward we go. I used an angle block to carefully set the angle and then checked/tweaked it as needed. This was repeated each time for four dovetails, it really wasn't bad, thanks to the 60 deg angle block.

This is the inner block that requires reverse dovetails on both sides.

Double checking the direction of the dovetails

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Honed all the edges

Everything fits

This is all the progress I've made thus far and it has gone pretty smoothly without me messing up parts and having to redo stuff. Still have lots of other pieces to do; namely bearing blocks, table, fence carrier, fence, leadscrews, handwheels...

 

[stioc]

Day 6

Continuing where I left off last.

Made three identical bearing blocks:

Then started on the fence carrier but it's been kicking my @ss. It's like a T-nut with threaded holes on top as well as a hole running the entire width with the center portion threaded. The first attempt (shown on top) looks good with all the features but I went a few thou too deep on one of the slots - this will make it not sit flush.

So I had to scrap it and start over (cut another chunk of steel, machine it to dimension and then drill and thread)...it was going well

until the corn-cob endmill took a sudden bite...son of a #@$! I guess I got too greedy with my WOC at the DOC even though my feed rate was about half of what it should've been.

So I guess it'll be take 3 next time :lol_hitti So far I hadn't ruined any parts so this was the first. Also when I start to bolt these pieces down to the rest's top plate everything needs to align correctly, there's really no room for making imprecise holes etc. It's making me a bit nervous.

 

[mattthemuppet2]

bummer! Looks like you were climb cutting - my guess is that there was a bit of slack in your table travel and the cutter self-fed itself a bigger bite than you expected. Try cutting the other direction next time and leave the climb cutting for a finishing pass with a nice 4 flute.

 

[stioc]

You're 100% correct. I was indeed climb milling as I often do due to the fact that it creates less strain on the machine and the cutter. In this case, after retracing my steps from last night, I was in the cut when I accidentally hit the key to reverse direction. The CNC software is configured to take up the backlash amount on directional changes and that's when the cutter took a big bite.

 

[mattthemuppet2]

I'm sorry, I didn't realise that it was on a CNC, that changes things a bunch. Glad you figured it out.

 

[stioc]

Day 7

I did remachine the fence carrier block but didn't drill and tap the top 4 holes nor did I skim it flush with the top plate. Doing so at the very end will be better in my opinion.

Next I started mounting all the pieces to the top plate. This is sort of the moment of truth. If things don't line up that would be a bummer. I decided to start with the table's fine feed bearing block, these are all going to be #6-32 holes, the drilling and tapping is in the 1/4" thick plate but these are no through holes so the depth has to be controlled. Also need a plug tap, and I highly recommend the YG1 spiral tap I got, it cut like butter and evacuated the chips up like a drill bit does.

With the first bearing block in place I attached the center dovetail and then placed one of the side dovetails against it, making sure it was all square to each other.

Then came the second dovetail. I decided to fold paper 3 times and use that to leave a gap because the two dovetails were running a bit rough against each other. However, in hindsight I should've just made the holes in the two end dovetail blocks slightly larger to allow small adjustments and I should've done the same for the bearing blocks too...I actually did in the end because things were binding up.

This completed most of rest's top and the milling work. I still have to make a fence but next I want to start on the round/lathe parts.

 

[stioc]

Day 8 (the lathe work):

Well I thought this was going to be somewhat of a more difficult task to turn leadscrews and graduated dials but I was done in 4 hrs and actually really enjoyed it. I just seem to enjoy the lathe work more than the mill work it seems lol

Used the tailstock die holder for the first time. This thing is slick but I was turning by hand so it was a slow going

For the longer leadscrew after I got 5 or 6 threads by turning it manually I decided to speed it up...to 600 RPM by gripping the die stock holder and hitting the switch (making sure I was clear of everything and I had an exit strategy if things went sideways). I don't recommend this if your lathe has a powerful motor or you're cutting a 'stronger' thread. I had purposefully undersized the major diameter by .01" so it threads easily and I can actually stall out the motor on my lathe with my hulk grip (the belt slips). This worked so well, how well? literally 3 seconds and I was done!

Then I made graduated dials, each line is .0013"

There's everything completed...I can see the light at the end of the tunnel now!

 

[stioc]

Removed the dykem and honed the sharp edges of all the parts. Ready for assembly!