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The Artful Bodger
04-15-2012, 04:30 PM
This idea is probably 150+ years old!:D

I made a couple of 'parallels' for my mill, I clamped scrap steel blocks to the mill table and took a light cut over the top surface with a fly cutter.

I had previously stamped the letter 'L' on the end of each one to remind myself to always use them aligned the same way on the mill table.

According to my tiny brain these should be as 'perfect' as I will ever need.;)

Hopefuldave
04-15-2012, 04:40 PM
I have some of those too - and a set of "inaccurate slip gauges" for not-so-critical setups, ranging between 0.050" and 6" cut from a length of 20x20mm cold-rolled and milled then lapped to size - good enough for most of my uses at <1 thou" tolerance! For small adjustments I add a few pieces of shim or feeler gauge to the stack, then measure and repeat...

Dave H. (the other one)

philbur
04-15-2012, 04:45 PM
I think this is only true if you always use them in the same spot on your table and clamp them in exactly the same manner they were clamped when you machined them.:rolleyes:

Phil:)


According to my tiny brain these should be as 'perfect' as I will ever need.;)

The Artful Bodger
04-15-2012, 05:19 PM
I think this is only true if you always use them in the same spot on your table and clamp them in exactly the same manner they were clamped when you machined them.:rolleyes:

Phil:)


You could well be right and that kind of calls into question the worth of factory made parallels too which would only be accurate in some places and not others?

MotorradMike
04-15-2012, 05:25 PM
You could well be right and that kind of calls into question the worth of factory made parallels too which would only be accurate in some places and not others?

I respectfully disagree.
Factory parallels are parallel to within the tolerance specified.

Parallels made on your mill simply match the angle at which they were milled.
These fall into the category of measurement tools, most of us have to buy them just like we buy micrometers.

The Artful Bodger
04-15-2012, 06:05 PM
Obviously I am missing something here, perhaps I am using the wrong terminology...:)

I would use parallels on my mill to support a workpiece above the table so that I can drill/mill right through without damaging the table.

Philbur says home-made parallels would only be accurate when used in the same place, and I am sure he is right as obvioulsy nothing is perfect in this world and that includes my mill table.

Now if the table is not perfect the expensive bought parallels will not be able to compensate for that whereas my home made parallels would be 'more perfect' at least in the position in which they were made.

Dr Stan
04-15-2012, 06:47 PM
Oh good grief. Just use the parallels and quite arguing about minutia.

The Artful Bodger
04-15-2012, 07:22 PM
Oh good grief. Just use the parallels and quite arguing about minutia.


Nah, thats not my point, I am suggesting that my home shop parallels are just as good and maybe better for my purpose than bought ones.

philbur
04-15-2012, 07:39 PM
I think it might be good for a one time set-up but for repeated use under different conditions and run of the mill precision you may as well just use ordinary flat bar-stock, I do.

Precision parallels, together with a precision mill make close tolerance work quick and easy. If you are good you can do the same quality work without either, it just takes much longer to set it up.

Phil:)


Obviously I am missing something here, perhaps I am using the wrong terminology...:)

I would use parallels on my mill to support a workpiece above the table so that I can drill/mill right through without damaging the table.

Philbur says home-made parallels would only be accurate when used in the same place, and I am sure he is right as obvioulsy nothing is perfect in this world and that includes my mill table.

Now if the table is not perfect the expensive bought parallels will not be able to compensate for that whereas my home made parallels would be 'more perfect' at least in the position in which they were made.

sasquatch
04-15-2012, 07:40 PM
Agree Bodger, Make em and use em.:D

Forrest Addy
04-15-2012, 07:47 PM
The object of "parallel" is if mates are matched for size and all are parallel. Everything else is preferential even straightness - if th error isn't excessive. They don't even have to be a particular size; merely parallel half a$$ straight, and the height you need at the moment.

For years in my home shop I got along fine with cold rolled steel rectangles. When I first set up I asked a local steel supplier to set aside rems for me and when he got to a ton, call me. In among the rems was a good selection of cold rolled flats and rectangles. Laid out yight together and there was mayne 3 frrt of shelf taken up - maybe a hundred pounds or more of make do set-up tooling. Mike them and they are pretty parallel and even flat and straight. A little judicious dressing with a file and a stone and some scientific peening to straighten and I hade a hell of a collection of parallels all for scrap price. (This was 1971 when steel was cheap.)

Anyway, satisfactory home brew parallels are very possible but results depend on the care and foresight with which you make them and since they are soft, the care you employ when you use them - and dress the dings and burrs as you make them.

Nowadays in the epoch of cheapo imports I have several thickness sets of hardened and ground parallels but the cold rolled steel ones still have a place.

lane
04-15-2012, 07:51 PM
If they are parallel with in 0.0005 they are good enough for any thing you will do. Even .001 will be alright . I have plenty of home made parallels and they all work just fine. You aren't building rocket ships are air planes. Use them .

Bryan B
04-15-2012, 08:26 PM
I think what Bodger is driving at is that, like soft-jaws on a lathe, his 'parallels' are machined in situ, and therefore necessarily true to the spindle. Repeatability is another question.

The Artful Bodger
04-15-2012, 08:29 PM
Thanks for all the comments.

I am sorry if I did not make clear the gist of what I am doing.

I am skimming the top surface of the scrap steel blocks to make a surface that is parallel with respect to the movement of the mill head and I am marking these blocks so they will always be used in the same orientation with a view to preserving this accuracy.

Dang! Bryan you are right on! That is exactly my message, you posted while I was typing.

MotorradMike
04-15-2012, 08:34 PM
The object of "parallel" is if mates are matched for size and all are parallel. Everything else is preferential even straightness - if th error isn't excessive. They don't even have to be a particular size; merely parallel half a$$ straight, and the height you need at the moment.

For years in my home shop I got along fine with cold rolled steel rectangles. When I first set up I asked a local steel supplier to set aside rems for me and when he got to a ton, call me. In among the rems was a good selection of cold rolled flats and rectangles. Laid out yight together and there was mayne 3 frrt of shelf taken up - maybe a hundred pounds or more of make do set-up tooling. Mike them and they are pretty parallel and even flat and straight. A little judicious dressing with a file and a stone and some scientific peening to straighten and I hade a hell of a collection of parallels all for scrap price. (This was 1971 when steel was cheap.)

Anyway, satisfactory home brew parallels are very possible but results depend on the care and foresight with which you make them and since they are soft, the care you employ when you use them - and dress the dings and burrs as you make them.

Nowadays in the epoch of cheapo imports I have several thickness sets of hardened and ground parallels but the cold rolled steel ones still have a place.

Forrest:

I'd happily pay your price for 10 pounds of anything you thought was straight and parallel.
I'm not going to try to make my own though, I've got enough other errors to contend with.

gnm109
04-15-2012, 08:39 PM
Oh good grief. Just use the parallels and quite arguing about minutia.


I have to agree. It's not worth making your own when good ones are so reasonably priced

oldtiffie
04-15-2012, 11:05 PM
Originally Posted by The Artful Bodger

Obviously I am missing something here, perhaps I am using the wrong terminology...

I would use parallels on my mill to support a workpiece above the table so that I can drill/mill right through without damaging the table.

Philbur says home-made parallels would only be accurate when used in the same place, and I am sure he is right as obvioulsy nothing is perfect in this world and that includes my mill table.

Now if the table is not perfect the expensive bought parallels will not be able to compensate for that whereas my home made parallels would be 'more perfect' at least in the position in which they were made.

The way you are using them is as spacers to keep the job clear of the mill table for drilling.

Given the "slop/clearance" between most drills and the drilled hole/s and the usual high positional errors for drilled holes, it would not matter one iota if you just used hot rolled bars "as is" (not machined).

Precision parallels are spacers too but their role is usually to keep a surface parallel to the vise fixed jaw or a mill table.

I often use cold rolled strip for spacers and parallels (job dependent) and they work fine.

J Tiers
04-15-2012, 11:18 PM
use the least expensive tool that does the job. Scrap parallels can work well, and if you nick one, it won't annoy you so much.

If you want better ones, you can make them too, but you'll need a granite flat (no a piece of glass won't do here) and good indicator with stand.

Scrape one side of each flat, then check the opposite sides by passing them under the indicator on the flat.... use the results to guide your scraping, and work until the two match in height, AND are flat and even in height the whole length and width.

It isn't that hard, although steel is a big nuisance to scrape. CI is much better.

oldtiffie
04-15-2012, 11:42 PM
If all you are doing is using your mill as a press-drill why not use the packers you'd use on a press drill - kiln-dried dressed all-round rectangular hard or soft wood (as used to build the house frame) will work just fine and you can drill into them and replace them as required.

If I have a line of holes to drill on the mill, I set and clamp the job to the table with the holes positioned over the table t-slots - no spacers, packers or parallels needed.

I keep all jobs as simple as I can and use just basic tools.

danlb
04-16-2012, 12:30 AM
If I have a line of holes to drill on the mill, I set and clamp the job to the table with the holes positioned over the table t-slots - no spacers, packers or parallels needed.



Thank you. That's yet another technique that I would not have thought of.

Dan