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lenord
12-27-2006, 08:54 PM
All,

Has anyone bought a set of 1/2 or 1/8" x 6" flat parallels lately that they measured to check their accuracy ?
Will you share the vendor/part numer ?

I am needing accuracy down to .0005".....thickness, length etc. The ones i have are not cutting it....

Thanks
Lenord

krems
12-27-2006, 10:24 PM
At risk of showing my ignorance what are parallel bars used for. I got a set w/ the lathe but I've never used them. They are cheap ones so not to be used in precision lathe work. Didn't mean to hijack the thread.

Krems

bob308
12-27-2006, 10:33 PM
parllels are use in a mill.

we made our own as part of our trining and we ground them closer then .0005

Fasttrack
12-27-2006, 11:01 PM
Krems - i'm new to this game too, but my understanding is that they are used in a milling machine vise to keep work off of the bottom of the vise. For example, today i cut some .515" slots in some 1/4" thick strap (2.25" by 1.25") for mounting a bike wheel on an HMV car. To hold the pieces in the vise and still cut the slot through the metal without also cutting a groove in the bottom of the vise or table, i used some very inaccurate parallels (read some pieces of 1/4" thick 1" wide strap :D ) to keep the work above the bottom of the table but still parallel to it.

Lenord - check Travers and JL industrial and, even, Enco. Most of them give specs for accuracy.

1/8" Thin style 10 pair Parallel Set carried through Enco
.0002 parallelism
Paired +/- .0004 in height
52-58 HRC

Brands: Enco Model Number
USA $112.27 505-1864
Fowler $184.37 422-184.37
Brown and Sharpe $ 199.83 637-7529


Brown and Sharpe 1/4" 9 Pair Pallel Set
.0002 parallelism
Nominal Abosolute heights, plastic case

Brown and Sharpe $211.95 - enco model number 601-1150


Enco 1/2" 8 pair parallel set
.0003" parallelism
paired +/- .0003 in height
Length +/- .006
Width .4921 +/- .0008
Woodcase - HRC 52-58

$159.80 Model Number 240-03262

Enco 1/2" Steel Parallels - 4 piece set
.0003 parallelism
$28.04 Model number 637-7536



Among many others
Go to use-enco.com and plug in one of those item numbers or just browse around for what you need...they'll probably have free shipping in january but then are you outside the US? This might not help you at all :P

rockrat
12-27-2006, 11:01 PM
Ok, I was curious, so I checked mine.

Ho-made set (I'm not a ho but you get the point :D ). Checked with standard Starrett 0.0001" mic's.
1" parallels - 0.0002" from end to end, bar to bar max change (ete, btb).

1/2" - Checked with Mit digital mic's 0.00005" resolution.
Brand x from IDG (McMaster Carr like dealer) - 0.0004" ete, btb.
Brown & Sharp thin parallels - 0.0002" ete, btb.
Brown & Sharp thin wavy parallels - 0.0003" ete, btb.

So, I was curoius about the brand x and checked the 5/8".
Try 0.0014" - sucks. Now I'm wondering what the rest are.
So I might cehck them....... after Mythbusters.

krems
12-27-2006, 11:07 PM
Now I understand what the parallel bars are used for. I checked mine...not even close to being straight or consistant thickness..ie..JUNK

Thanks...Krems

lenord
12-27-2006, 11:37 PM
You can also put parallels on a rotary table to keep the work off the table.

I required a good accuracy, put the parallels on there, bolted down the Al. slab, put on the DI, flatness off by .003", after retorquing the nuts...
Took the slab of Al. off, checked the slab and table, perfect. (good Al. slabs)
Mic'd the parallels, .007" off on one, .007 on another...These are cheap parallels from J&L. I got them when I started machining a few years ago. Suppose to be better accuracy than this !
Mic is a Starrett. Checked it too. It's fine.

I want some "known to be decent" parallels for a reasonable price. I don't want the hassle of reshipping and fussing about with returns from J&L or Enco.

I can buy bar stock that has a better thickness tolerance than these things. For the RT, I may just make a ring of the right size and use that. The Mic6 I am using is awesome.

Thanks for the replies so far !

Lenord

Carld
12-27-2006, 11:37 PM
Not junk at all. I true mine on a surface grinder. It is important to grind each pair together and perpendicular to the table. It is not important that they be exactly 1/2", 5/8", etc. unless you have to space the part an exact distance off the table or vise. I have never had to have them an exact width. I use tool steel bar stock or cold roll to make my own. I do have a store bought set.

lenord
12-28-2006, 01:18 AM
Not everyone has a surface grinder though...

Lenord

EDMTech
12-28-2006, 02:09 AM
Not everyone has a surface grinder though...

Lenord

For the cost of a really good set of parallels, you could probably almost BUY a surface grinder these days!

Ron Horton
12-28-2006, 03:27 AM
Being new at this machining business, I have asked questions all over-- One guy showed me some rings he cut in varying thicknesses from a 1 1/2 " dia. heavy walled SS pipe to use in the place of parallel bars, and he says they work well-- He is now cutting rings from a 1" piece of SS pipe-- He cuts these on a lathe, and has offered to make me some if I pay for material-- Have any of you heard of this before?? Practical?? Comments?? Thanks--
Best regards, Ron

" I just had it a minute ago"

darryl
12-28-2006, 03:34 AM
.007 off in 6 inches? Huh? Might as well start with some threaded rod and hammer the threads flat on four sides- probably get you just as close.

You could cut some strips of maple on a table saw and get closer than that. You could stack 167 strips of paper to get the 1/2 inch thickness and be better than that.

dicks42000
12-28-2006, 04:18 AM
OK, parting off pieces of pipe or tubing would work, but best if they are ground flat after parting. Better yet, why not use races from ball bearings. Dead bearings are available at most motor rewind shops for free. Great when you need clearance for a boring bar or reamer, for faceplate work etc. Also useful for packing up around a hold-down. (My dad used to use them. Also read the idea in Sparey's book "The Amatures Lathe".)
Yes, grind parallels in pairs. Mark them if you need to know dim'n. Usually it's the parallelism you need....
Helps to have a saurface grinder though.
Rick

Swarf&Sparks
12-28-2006, 07:01 AM
Bearing races. They're ground within a gnat's nut.

Spin Doctor
12-28-2006, 09:42 PM
Of course if the surface the parallels are sitting on is out of flat. The point being you are always at the mercy of the compounding errors. Murphy's Law says they always make things worse. They never cancel each other out.

As an aside magnetic parallels are always flat if used properly (the secret is to grind them every single time you use them).

Greg Menke
12-29-2006, 01:17 AM
I was in the local Harbor Fright, they had boxed sets of parallels for $40 so lacking even a nasty set I got one. I've been using HSS tools to offset stuff in the vise. I just checked over the 1/8"x7/8"x6" pair, arbitrarily selected from the set.

Thickness was uniformly different about .002 between the pair, with variations at about .001 or below on each strip. Width was better, varying somewhere down at .001 or so along the strips but within about .001 between the pair. Didn't bother with the length. Measured with a Mitutoyo thickness mike and a generic import thimble micrometer.

So I guess $40 isn't unreasonable since there are 10 sets, convienently stored in a box.

Regards,

Greg

A.K. Boomer
12-29-2006, 10:30 AM
All the manufactures should give the specs, I went through e-bay and found mine in the "buy it now" for $18.00 plus shipping, they are china, they were advertized as being within 2/10ths, they came in a great sturdy red plastic case , they are 6" by 1/8" thick, when they arived i checked each and every one of them for hieght -- yup --- within 2/10ths, should be on that show "how do they do that":D

SGW
12-29-2006, 10:40 AM
I got a boxed set of 9 or 10 pair of 1/8" thick parallels from Travers Tool a few years ago, for something like 29 bucks on sale. I was amazed at how closely the pairs were matched...within a couple tenths. There are a few pits in the surface of some of the parallels, so cosmetically they aren't perfect, but in terms of functionality I have no complaints. Like Boomer's, they are in a pretty decent red plastic case.

ammcoman2
12-29-2006, 08:14 PM
Being the cheapskate that I am, I picked up some flat ground stock a few months ago from KBC (1/2, 5/8, 3/4: all 1/8 thick) and cut/milled them to 6" lengths. Looked good. And I have some leftovers for the inventory. He He.

After reading this thread something twitched in my feebled brain and I went into the w/shop to check the height of each one. Well! They vary by 0.002". I guess it is just the thickness that is held to a tight tolerance. Back to the drawing board, er mill, for a cleanup pass.

Geoff - much humbled.

spope14
12-29-2006, 10:13 PM
Leonard,

As for milling your aluminum slab, it may not be just parallels. Some aluminums have stress in them that release when milling off stock surfaces. The same may also be true when clampping, you put a bit of stress in the material.

lenord
12-30-2006, 12:13 AM
Thanks for the hints guys. I musta got a really bad batch of parallels, twice !

The Al. is a 1" x 18" disc. I did see that by changing the torque of the hold down bolts I can make the DI move.

I may break down and buy a decent set of parallels for a reasonable sum. Definately not on sale unless I can return them if they are off.
Might even just price ground flat stock too..

Lenord

Evan
12-30-2006, 01:54 AM
If you are looking for consistent dimension in one axis only such as thickness then cut off a couple of strips from suitable aluminum tooling plate. The actual thickness may vary by .001" from the plate spec but the two pieces if taken from beside each other will be the same within .0001" or better. There isn't much variation over a short distance in tooling plate. With 3/4" inch plate I have the most I have measured over 10 inches is around .0002". Tooling plate is finish ground to spec.

Your Old Dog
12-30-2006, 09:35 AM
I was in the local Harbor Fright, they had boxed sets of parallels for $40 so lacking even a nasty set I got one. I've been using HSS tools to offset stuff in the vise. I just checked over the 1/8"x7/8"x6" pair, arbitrarily selected from the set.

Thickness was uniformly different about .002 between the pair, with variations at about .001 or below on each strip. Width was better, varying somewhere down at .001 or so along the strips but within about .001 between the pair. Didn't bother with the length. Measured with a Mitutoyo thickness mike and a generic import thimble micrometer.

So I guess $40 isn't unreasonable since there are 10 sets, convienently stored in a box.

Regards,

Greg

I've got a similar set from Enco and am satisfied. When working on my rocketships in my backyard I farm out anthing that needs more accuracy than what they have! Seems to me you'd need a Kurt vice to take advantage of much more accuracy than the cheep ones afford. If I put a Kurt vice on my mill it'd be like putting a $100 saddle on a $10 horse.

lenord
12-30-2006, 11:19 AM
YOD,

LOL !

I agree, but I was using a rotary table that was actually flatter than I could measure. The machine is just a M/D though...

Did you want that motor ? I sent you a private message via this BB with a link to the specs...

Lenord