Sanity check on aisle Onsrud!

[geneb]

I've got a pair of Onsrud 64-025 cutters that I just purchased - they state the cutter diameter as .25, but my caliper tells me .235. Is there anyone here that has one they can check for me? I'm either losing my mind, my caliper is, or Onsrud's part specs can't be trusted.

tnx!

g.

[scottp55]

Gene, Just curious. Directly from Onsrud? SB starter set .125" straight was .1135" which sent the machinist who was helping me through the roof! He convinced me to set up my "ACTUAL" category which has saved my butt more than once. I've got a couple suppliers who are Consistently .005" undersized and I can go through dozens of their bits without finding ANY discrepancies.
I Always measure now, and keep "Currents" in a separate box until I go to use them.
Just mucked me up yesterday.
If I see "Onsrud" I measure it! Very good cutting edges, BUT dimensions are ALWAYS in database in Actual and carefully monitored and a fair amount of discrepancy between Kirks Database and mine! Hard to exchange files when common bits are different diameters. We always have to make sure he's changes bit to HIS Database. Pain!!

[Burkhardt]

But that is a single flute cutter. How do you even measure the diameter at the flute with a caliper? You can not lean both jaws of the caliper against a flute edge.
If you just measure against the opposing surface, this is definitely undercut to not rub on the material. Or did you measure the shank diameter?

Maybe you can cut a clean slot in dense hardwood and measure if it is actually undersized?

[Brady Watson]

Maybe you can cut a clean slot in dense hardwood and measure if it is actually undersized?

This is the ONLY reliable way to tell...

-B

[ssflyer]

I've found MDF to work well - just measure it right after cutting...
It's cheap!

[geneb]

I was rotating the cutter in the jaw of the caliper. I'll do a test cut and see how it works.

tnx.

g.

[MogulTx]

I've rotated the bit in my caliper, but I find the actual test of the bit to be the reliable method. I try to cut in the material I am going to work with and at the roatation and travel speeds that I'd like to use- which gived me real world information from which to assess my cutting project

[jTr]

I've found the under size issue to be true on any brand bit if measured with a caliper, regardless of physical limitations and variables discussed above.

To consider:
- Shank is very likely precise at .250 , being pulled from carbide tool stock
- in order to shape and sharpen, it is inevitable that you'll loose some material
= Average of .005 to .006 under size is to be expected, and quite amazing, really.

When is this a significant issue?

For me, it is dados. When using melamine, it can be dead on for a 3/4" material. As of late, my suppliers seem to run upwards of .015 over size. In generating computer shop drafts of cabinets and furniture, it is done with the assumption of exact material thickness, which is obviously never the case for the sheet goods.

How to cope?

Under-size dados with under size plywood = very acceptable results, and I've ceased burning energy worrying. I'm making cabinets, not engine parts. A fit with .015 wiggle room makes for smooth assembly, and no excessive gaps in critical locations upon completion.

Under-size dados with over size melamine = now I'm sweating. My current formula:
.005 under size bit makes a pocket that is .010 under size, since I'm loosing .005 on both sides of the cut.
.010 to .015 over size on melamine = .020 to .025 under sized dado for a proper fit.

As of late, my solution is to assign an offset of +.021 on the pocketing tool path for the dado layer in Part works/ V-carve Pro.
This typically results in a super-snug fit that is more urgently required with melamine.

Adjust according to results you are getting, and if frustrated, remember, this is far easier to remedy in the CNC world than dealing with dado blade shimming in a table saw!!!

This seems a good place to interject an oft - stated but important note: Be sure to use a down spiral for any pockets cut into sheet goods, especially melamine. Tool change to compression bits for profile cutting, and be certain your first pass plunges .030 to bury the up cut tip into the material, assuring the down cut flutes are hitting that delicate face.

Jeff

[Justin G]

I've found the under size issue to be true on any brand bit if measured with a caliper, regardless of physical limitations and variables discussed above.

To consider:
- Shank is very likely precise at .250 , being pulled from carbide tool stock
- in order to shape and sharpen, it is inevitable that you'll loose some material
= Average of .005 to .006 under size is to be expected, and quite amazing, really.

When is this a significant issue?

For me, it is dados. When using melamine, it can be dead on for a 3/4" material. As of late, my suppliers seem to run upwards of .015 over size. In generating computer shop drafts of cabinets and furniture, it is done with the assumption of exact material thickness, which is obviously never the case for the sheet goods.

How to cope?

Under-size dados with under size plywood = very acceptable results, and I've ceased burning energy worrying. I'm making cabinets, not engine parts. A fit with .015 wiggle room makes for smooth assembly, and no excessive gaps in critical locations upon completion.

Under-size dados with over size melamine = now I'm sweating. My current formula:
.005 under size bit makes a pocket that is .010 under size, since I'm loosing .005 on both sides of the cut.
.010 to .015 over size on melamine = .020 to .025 under sized dado for a proper fit.

As of late, my solution is to assign an offset of +.021 on the pocketing tool path for the dado layer in Part works/ V-carve Pro.
This typically results in a super-snug fit that is more urgently required with melamine.

Adjust according to results you are getting, and if frustrated, remember, this is far easier to remedy in the CNC world than dealing with dado blade shimming in a table saw!!!

This seems a good place to interject an oft - stated but important note: Be sure to use a down spiral for any pockets cut into sheet goods, especially melamine. Tool change to compression bits for profile cutting, and be certain your first pass plunges .030 to bury the up cut tip into the material, assuring the down cut flutes are hitting that delicate face.

Jeff

I have been making a lot of plywood puzzle parts as of late, with perpendicular joints using dog bones so everything merrys up flush. Well every time I cut the parts with the exact width of the material measured with digital calipers, they don't fit, too tight. I was freaking out, thinking the bot was losing accuracy or aspire was f'd somehow. so I kept doing this negative offset in the profile passes. trial and error and so frustrating. Now I totally realize its because of the bits being smaller than their actual labeling. DUH! of course they are. Now i'm going to go insane trying to figure out how to measure my ballnose bits.. eesh.

[Brady Watson]

Wait a minute...End mills are most certainly their advertised size +/- 0.001 or so depending on where you get them. They are certainly not off by 0.005" - no way.

If I drill a hole with an end mill it is as close to exact advertised diameter as my digital bore scope or plug gauges can measure. 2-flute upcut spiral router bits are not typically manufactured to the same tolerances as metalworking end mills - but Onsrud is a good outfit and should be to spec.

Wood moves around while being cut. Dados can cup or be off-spec because your chipload wasn't right (EG - cutting too fast)...they can be WAY off by leaving the default Climb mill selected instead of Conventional when doing dados and pockets. A simple mouse click may cure all your ails.

-B