Edge Finder Speed Question

projectnut · Apr 18, 2020

I've had a couple edge finders for what seems like eons. I don't know the brand, and there's no markings on them. If I remember correctly they are supposed to be run at speeds above 300 rpm. They've worked fine at that speed until just recently, but in their old age seem to be a bit sticky. Where they would once work well at 300-400 rpm they now need to be turned at around 500 rpm or more to get accurate readings.

I thought it might be just old age creeping up on them, so I purchased a Starrett 827A. It didn't come with any paperwork or instructions, so I started using it at the same speed as my old ones. It seemed equally lazy, so I googled "Starrett edge finder speed". According to a couple old threads on this board people are recommending spinning them at between 1,000 and 1,500 rpm.

I'm also considering a Brown& Sharpe 599-792-2 since they seem to get good reviews. According to the vendors websites these "can be to be run up to 1,000 rpm". There doesn't seem to be an optimal or recommended speed.

Does anyone have experience with either the Starrett 827A or the B&S 599-792-2, and can you tell me what speeds they are supposed to be run at. It seems like speed "recommendations" are all over the board, and neither manufacturer includes anything with the units.

Trueturning · Apr 18, 2020

projectnut said:
I've had a couple edge finders for what seems like eons. I don't know the brand, and there's no markings on them. If I remember correctly they are supposed to be run at speeds above 300 rpm. They've worked fine at that speed until just recently, but in their old age seem to be a bit sticky. Where they would once work well at 300-400 rpm they now need to be turned at around 500 rpm or more to get accurate readings.

I thought it might be just old age creeping up on them, so I purchased a Starrett 827A. It didn't come with any paperwork or instructions, so I started using it at the same speed as my old ones. It seemed equally lazy, so I googled "Starrett edge finder speed". According to a couple old threads on this board people are recommending spinning them at between 1,000 and 1,500 rpm.

I'm also considering a Brown& Sharpe 599-792-2 since they seem to get good reviews. According to the vendors websites these "can be to be run up to 1,000 rpm". There doesn't seem to be an optimal or recommended speed.

Does anyone have experience with either the Starrett 827A or the B&S 599-792-2, and can you tell me what speeds they are supposed to be run at. It seems like speed "recommendations" are all over the board, and neither manufacturer includes anything with the units.

Buy some good ones. We ran them all the time at 1500 on a CNC spindle. On manuals it can easily vary. One can determine the least speed they can use and be acurate.

kustomizer · Apr 18, 2020

I have alwaus used 1000 rpm but just becayse that is how I was shown. Once in a while I let them soak overnight in diesel to clean and lube.

cmccull166 · Apr 18, 2020

I always used 1100 rpms I think that was from Herman Schmidt...IIRC
or was it 1000 but at 10000 they didnt last long. :dunce:

Mark Rand · Apr 18, 2020

Also give them a very good clean. Especially the mating faces.

DavidScott · Apr 18, 2020

3/8" Starratt, I don't know the # and it's in a collet holder so I can't find out. Many many years ago not knowing the best speed to run it I experimented and came up with 500 rpm gave me an exact .1000" from the edge. Faster increased the distance and I forget what slower did. That speed still works today.

DMF_TomB · Apr 19, 2020

projectnut said:
I've had a couple edge finders for what seems like eons. I don't know the brand, and there's no markings on them. If I remember correctly they are supposed to be run at speeds above 300 rpm. They've worked fine at that speed until just recently, but in their old age seem to be a bit sticky. Where they would once work well at 300-400 rpm they now need to be turned at around 500 rpm or more to get accurate readings.

I thought it might be just old age creeping up on them, so I purchased a Starrett 827A. It didn't come with any paperwork or instructions, so I started using it at the same speed as my old ones. It seemed equally lazy, so I googled "Starrett edge finder speed". According to a couple old threads on this board people are recommending spinning them at between 1,000 and 1,500 rpm.

I'm also considering a Brown& Sharpe 599-792-2 since they seem to get good reviews. According to the vendors websites these "can be to be run up to 1,000 rpm". There doesn't seem to be an optimal or recommended speed.

Does anyone have experience with either the Starrett 827A or the B&S 599-792-2, and can you tell me what speeds they are supposed to be run at. It seems like speed "recommendations" are all over the board, and neither manufacturer includes anything with the units.

.
many run edge finder at 1000 rpm (especially if 0.2" dia, .5000" dia can be slower than 1000 rpm if you want too), too slow it might be slow responding, usually for high precision most use a indicator and chair, obviously if spindle out of tram or leaning you get different reading depending on length sticking out of spindle.
.
horizontal spindles you have to worry about indicator rods sag (can be over .001" easily) and when spindle turning it tends to pick up spindle and go to side a little (can be easily over .0001"). you can indicate a bore just bored and measure a position error easily over .0002" at times. less of a problem with vertical spindles
.
indicator chairs get worn over time, some have over .0001" error when old

sandiapaul · Apr 19, 2020

I hit mine with Starrett M1 once in a while. Gently lift the mating faces and spray a little on. They work better after that.

moldcore · Apr 19, 2020

I've been using the Starrett 827A with the .200 Dia. for over 40 years. I run at 2000 rpm on the CNC and between 500 and 800 on the manual mill. Really depends on what you are holding them in. CNC holders and bearings run truer than a Bridgeport mill with an R8 collet set up. No point in buying a $50+ edge finder for a Bridgeport.

projectnut · Apr 19, 2020

I'm currently soaking the older edge finders in a little diesel fuel as suggested. I did find a sleeve for one of them with a part number. When I Googled the number it came up with the "Value Brand, Made In India" sold by MSC. I guess that further confirms the fact that they are old in that I haven't done much business with MSC for many years.

As for using the Starrett 827A I bumped the speed up to 1000 rpm and it works perfectly. It does seem a lot nicer than the old ones, so it'll be the go to edge finder from here on in. I'll just put the old ones in the drawer and use them as backups when I inadvertently put the Starrett in that "special place" and forget where that was.

carlherrnstein · Apr 19, 2020

I bought a Brown an Sharpe audible edge finder from amazon. I like it but, is not real loud. I usually run edge finders 800-1200rpm if you spin them took quick they come apart.

jermfab · Apr 19, 2020

I’ve been told by several mentors that 1100 RPM was the absolute max for a spring style edge finder. I’ve never personally broken one, but I’d just as soon not. That little end bit seems the perfect piece to bounce off a cheek and then the inside of my safety glasses and into my cornea. You know, because I’m standing there staring at it. I’ve not seen an appreciable increase in performance spinning them faster than 6-700 rpm. Individual results may vary.

Jeremy

sfriedberg · Apr 19, 2020

800-1200 RPM seems right to me. I've been telling highschool students to spin them at about 800. They have a Haimer there, which is what they normally use, and now I regret showing them old-school edge finders at all, because one student nearly spun the Haimer at 800 before stopped with a quick shout, a lunge and a raised hand.

Spruewell · Apr 19, 2020

Dang, I’ve always run my edge finders between 150 to 300 rpm. Never had the need to run them much faster than that and never had a problem finding an edge. The indicator chair doohickeys, although interesting, seem overly complicated for finding a part. Why add the potential errors of additional equipment to locating work positions? Just indicate on the part or fixture

DMF_TomB · Apr 20, 2020

Spruewell said:
Dang, I’ve always run my edge finders between 150 to 300 rpm. Never had the need to run them much faster than that and never had a problem finding an edge. The indicator chair doohickeys, although interesting, seem overly complicated for finding a part. Why add the potential errors of additional equipment to locating work positions? Just indicate on the part or fixture

.
edge finders usually do not repeat that good trying to hold a .0002" tolerance especially at slower rpm. sure they work ok holding .002 tolerance, debatable if you can hold .001" tolerance consistently 100 out of 100 tries
.
indicator chair is high precision, and you also have to worry about backlash. cnc have backlash too. usually not much but can easily exceed .0002" tolerance. obviously spindle tram or lean becomes a issue too. usually try to get same length indicating as the boring bar length, otherwise a bore just done, will indicate off center. obviously indicator rod sag is a issue when a horizontal spindle. some setup same indicator setup on a single length cylinder, zero indicator at top, rotate 180 and measure sag. once indicator sag value known it can be compensated for.
.
horizontal spindle rising and moving to side a bit at high speed is due to oil flow movement in bearings. spindle static to dynamic offset varies on rpm and spindle bearing looseness. this is measured again when a bore is just done and indicate setup same length and sag compensation, you still indicate bore just done is off center .0002" to the side
.
obviously if dealing with .002" tolerance you might never use or even seen a indicator chair. took me over 30 years before I worked in a shop that had indicator chairs. Never saw or used one before that. indicator chairs get a yearly gage inspection, thats how I know some are rated .0001" off. its same as gage blocks are measured for wear usually yearly and error value recorded so it can be compensated for.

Mike1974 · Apr 20, 2020

I can say definitely don't run them at 6000 rpm... ask me how I know :leaving:

I haven't used one in a very long time, but i would say in the 1000rpm range has always worked well.

carlherrnstein · Apr 20, 2020

So what if edge finders are not easily repeatable to .0002 (I trust mine to .0005) I have never seen a application where it would matter. I have only used and have seen them used to find a edge where a hole pattern is being drilled, or locating a blank on a cnc and then all features are milled/drilled.

johnfalco · Apr 20, 2020

I've run mine at 1000 rpm for 30 yrs and never had to replace it. I do believe that they are + or - .003 as far as accuracy so if you need closer than that you better use another method. Another thing I've found is the cheap imports don't seem to snap off center like the Starrett and B&S do. They ended up in the trash pretty quick and lesson learned.

Mike1974 · Apr 20, 2020

johnfalco said:
I've run mine at 1000 rpm for 30 yrs and never had to replace it. I do believe that they are + or - .003 as far as accuracy so if you need closer than that you better use another method. Another thing I've found is the cheap imports don't seem to snap off center like the Starrett and B&S do. They ended up in the trash pretty quick and lesson learned.

+/-.003??? Tou've got a bad one, or something is going on screwy. I would say +/-.001, but I do agree if you want/need the best accuracy you should use an indicator os probing...

wesg · Apr 20, 2020

A similar thread several years ago led me to use 1800. I've gotten good results with that.

But I'll also verify 6k+ is 'a terrible thing', as Eddie Murphy said. I guess I didn't hit enter twice, or something like that, after setting S1800.2 before starting the spindle ... 'tink'. And that was my favorite, the reduced shank unit Fisher made in the style of the Hermann Schmidt.

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